1 biology.docx · Web viewThe word Biology is derived from two Greek words: Bios. which means ....

INTRODUCTION TO BIOLOGY

All around us we notice the existence of trees, grass, insects, birds, wild animals, rocks, soil, water and many other things. This make part of our environment from which we derive existence. All these things can be put into two categories: Living things and non-living things. You learnt about these things in Primary science.

In Biology we study living things.

Lesson Objectives

By the end of the lesson you should be able to:

Define biology. List at least five branches of Biology. Explain ways in which Biology is important in our everyday life. State the characteristics of living things. State the main observable differences between plants and animals.

Biology is a science. It is the study of living things in their environment. The word Biology is derived from two Greek words: Bios which means life and logos which means knowledge. People who study Biology are called Biologists.

In this session you will learn about

a) Branches of Biology, b) Characteristics of living things, c) Classification of living things, d) Cells and their structure, e) the microscope and how to use and care for it, f) Cell Physiology, g) Nutrition in plants and animals.

Branches of Biology

Biology can be divided into various branches. Such branches are named according to which organisms are involved:

1. Botany- the study of plants e.g. Maize.

2. Zoology- the study of animals e.g. Leopard

3. Microbiology- the study of micro-organisms e.g. bacteria

4. Mycology- the study of fungi e.g. mushrooms

1. Botany- the study of plants e.g. Maize.

2. Zoology- the study of animals e.g. Leopard

3. Microbiology- the study of micro-organisms e.g. bacteria

Bacteria

4. Mycology- the study of fungi e.g. mushrooms

Mushrooms

Taxonomy refers to study of scientific classification of organisms.

To replace with movie

Importance of Biology

Study of Biology helps you to develop scientific skills such as planning, observing, classifying, measuring, recording and analyzing

It is also necessary for entry into careers such as Medicine, Teaching, Agriculture and Research. Scientific research based on Biology has led to development of high yielding and disease-resistant plants and animals.

In solving environmental problems such as shortage of food, poor health services misuse of environmental resources e.g. forests, wildlife, water and soil.

To know more about living organisms in relation to their environment.

SUMMARY OF CHARACTERISTICS OF LIVING THINGS

Nutrition

Living things feed.

Plants make their own food.

CLIP

Animals feed on ready- made food.

CLIP

Reproduction

Refers to giving rise to young ones of the same kind. Living things give rise to young ones of their own kind.

Irritability

Living thigs have the ability to detect and respond to changes in their environment.

Gaseous Exchange

They exchange Carbon (iv) Oxide and Oxygen, across a respiratory surface.

Respiration

They breakdown food in their body cells to release energy.

Excretion

They remove waste products of chemical reactions from the body.

CLIP

Movement

Change in position of part or whole organism.

Animation

Growth and Development:

They grow. Growth is permanent increase in size and mass of an organism.

They develop. This is the modification of simple structures to more complex forms.

Excretion

Reproduction

Irritability

Growth and Development

MAIN DIFFERENCES BETWEEN PLANTS AND ANIMALS

{GAME}

The following statements are comparisons between plants and animals. Click on True or False button for the correct statement.

• Plants make their own food while animals feed on already made food.

• Plants and most animals move from one place to another.

In the bubble show some parts of a plant moving while animals move from place to place.

Plants respond slowly while animals respond quickly to changes in the environment. Plants and animals grow throughout the life.

In the bubble - plants grow indefinitely while animals stop growing when they reach adult stage.

Other difference between plants and animals will be explained in relevant topics.

Classification of Organisms

Classification refers to placing of organisms into their respective groups which are known as taxa (one is a taxon), in relation to features or characteristics of the specific organism.

There are millions of living organisms on earth. Traditionally man classified organisms depending on their characteristics, habitat as well as the use to which the organisms could be put. Scientists classify them basing on their physical and physiological characterstics.

Classification also allows for easy identification, easy naming and study of the organisms. It is also easy to establish ancestral relationships between organisms using a classification system.

SUMMARYOrganisms are grouped into five major kingdoms namely; 1. Monera

2. Protoctista

3. Fungi

4. Plantae

5. Animalia.

The seven taxonomic units of a Kingdom, in descending order are:

1. Kingdom

2. Phylum/division

3. Class

4. Order

5. Family

6. Genus

7. Species

Binomial nomenclature is a system of naming organisms by

assigning them a generic and specific name e.g., the lion belongs to the genus Panthera and species leo. The scientific name of the lion, therefore is "Panthera leo".

Background Information

In Primary Science study, you grouped living organisms as shown below::

LESSON OBJECTIVE

By the end of the lesson you should be able to state the necessity and significance of classifying organisms.

Necessity and Significance of Classification

Organisms are classified according to similarities and differences. This is based on external and sometimes internal features of the organisms. The illustrations below indicate organisms with varying characteristics that can be used in classification.

BACKGROUND INFORMATION

Activity 1

Place the following animals into their respective groups by dragging and dropping method.

- Man - Lizard - Crab - Elephant

- Cockroach - Octopus - Warthog - roundworm

Drag and drop the following plants into the group of monocotyledons or dicotyledons.

Flow chart of classification of plants into monocots and dicots.

• Onion bulb with leaves

• Sisal plant

• Rose flower

• Banana plant

• Pawpaw plant

• Sugarcane plant

Correct answers

Monocots- sisal, onion, sugarcane

Dicots- Rose flower, banana and pawpaw

Voice and print

The placing of organisms into various groups based on their structural and physiological differences and similarities is called classification.

Necessity for Classifying Organisms

You have already learnt that Classification is important for:

1.) Easy identification of orgsnisms. 2) For scientific naming, so as to have universally accepted names. 3) For establishment of relationships between organisms and their ancestry.4) For easy study of organisms. 5) To facilitate orderly arrangement of biological information to avoid confusion.

Assignment

1. List down as many living organisms as possible and place

them in their respective kingdoms.

2. With guidance from your teacher, assign scientific names to

common plants and animals found within your school compound.


In primary science you placed living things into two groups: plants and animals. Plants make their own food and animals feed on ready made food. You placed mushrooms in the group of non-green plants since they do not make their own food, but look like plants. Mushrooms, however, are not plants. Some organisms have been found to possess both plant and animal characteristics. For this reason, taxonomists have now placed organisms into five groups called kingdoms.

NB The kingdoms will be outlined in the course of the lesson.

GAME

LESSON OBJECTIVES

By the end of the lesson you should be able to;

1. Name the five kingdoms, giving an example in each case

2. Name the seven major taxonomic units of a Kingdom

3. Place one plant and animal in the taxonomic units in descending order

ActivityUse the drag and drop method to place the taxonomic names listed below into their appropriate taxonomic position.

TAXON HUMAN MAIZEKingdom Phylum/division Class Order Family Genus Species

TAXONOMIC NAMES:Animalia, Monocotyledonae, Chordata, spermatophyte, primate, Mammalia, Graminales, Zea, Homo, Hominidae, sapiens, Plantae.

Human MaizeKingdom Animalia PlantaePhylum/division Chordata SpermatophyteClass Mammalia MonocotyledonaeOrder Primate GraminaeGenus Homo ZeaSpecies sapiens mays

Incorrect answer (try again)

Units of Classification

In primary science you placed living things into two groups; plants and animals. Plants make their own food and animals feed on ready made food. You placed mushrooms in the group of non-green plants since they do not make their own food. Such organisms are not really plants. Some organisms have been found to possess both plant and animal characteristics. It therefore became necessary for taxonomists to place organisms into five groups called kingdoms.

The kingdoms will be outlined in the course of the lesson.

Currently, the Five-kingdom system of classification is used. In this classification system, organisms are placed in the following groups:

1. Kingdom Monera- This group consists of bacteria such as Coccus, Bacillus and Vibrio. Examples are shown in the figure.

2. Kingdom Protoctista This group contains single celled organisms including Amoeba, Paramecium, Trypanosoma.See examples (Liver fluke and Trypanosome) in the figure.

3. Kingdom Fungi This kingdom includes Mushroom, Bread mould, Yeast, Rhizopus. The mushroom in the figure are growing on a dead tree trunk.

4. Kingdom Plantae This contains plants such as Maize, Bean and Fern

5. Kingdom Animalia Contains animals for example Insect, Fish, Lizard, Bird, Human being.

ANALOGY OF CLASSIFICATION

Planet earth is one huge body which supports life unlike other planets. It can be used as an analogy in classification

This planet is made up of five continents. The continents differ from each other in many ways but have some similarities such as climatic conditions and geographical features.

This can be likened to classification in which organisms are placed into five kingdoms. The organisms in a kingdom have some similarities and a wide range of differences.

Analogy of classification based on the map of Africa

Each continent is made up of regions. The African continent is made

up of several regions such as the East African region. This is likened

to the classification in which organisms in a kingdom are placed into

groups called Phyla/ Divisions. Members of a phylum/division have

more in common than members of a kingdom.

Analogy contd

Each region is made up of several countries for example Kenya, Uganda, Tanzania.

Rwanda and Burundi are countries which make up the East African region.

Similarly, several classes are found in a Phylum/ Division. Members of a classhave more in common than members of the same phylum/division.

Analogy of classification continued: -Provinces Vs Orders

Kenya is divided into provinces just like several orders make up one class. A province has a lot in common just as members of the same order. In Coast Province, for example, the most common group of people are the Mijikenda, who use Kiswahili as their major language.

Members of an order have many similarities.

District Vs Families

A province is further divided into districts, just like Order is

made up of several Families.

Members of the same family have more similarities than those of the same order.

Division Vs Genus

A district is further divided into divisions. This is likened to the

division of the families into genera. Members of a genus have a lot

more in common than members of a family. In a Division the people

are closely related, under one ancestry and have one area chief.

They have similar cultural habits.

Location Vs Species

INSERT LAMU MAP SHOWING DIVISIONS

A division is further divided into locations. This is likened to the

division of a genus into several species.

Members of the same species are so closely related that they can

interbreed to give rise to fertile (viable) offspring.

INSERT FLOWCHART OF GENUS PANTHERA AND SPECIES LEO AND PARDUS

Classification of Bean and Domestic Dog

An individual organism can be placed in different taxonomic units.

Examples:

Bean Plant

KINGDOM: Plantae

DIVISION/PHYLUM: Spermatophyta

CLASS: Angiospermae

ORDER: Rosales

FAMILY: Leguminosae

GENUS: Phaseolus

SPECIES: vulgaris

2. Domestic Dog

KINGDOM: Animalia

DIVISION/PHYLUM: Chordata

CLASS: Mammalia

ORDER: Carnivore

FAMILY: Canidae

GENUS: Canis

SPECIES: familiaris


You have already learnt how to classify an organism in various

taxonomic units. In this lesson, you will learn how organisms are

given scientific names.

Binomial Nomenclature

This refers to the giving of organisms two names: Genus name and specific name. The first name refers to the genus to which the organism belongs. The first and second names together refer to the species to which the organism belongs. For example, the scientific name of maize is Zea mays. Zea is the Genus to which maize belongs. Zea mays is the species.

LESSON OBJECTIVE

By the end of this lesson, you should be able to use Binomial nomenclature

to scientifically name a plant and an animal.

QUIZ

1. Name the five kingdoms which organisms are classified.

2. List the taxonomic units in classifying a plant in ascending order.

1. Fill in the correct taxonomic names of the following organisms.

Kingdom PhylumClass

1. The scientific name of a housefly is Musa domestica.What does Musa stand for?

(a) Which two of the following organisms are closely related?

Homo sapiensMangifera indicaHomo erectusCanis familiaris

(b)Give a reason for your answer in (a) above

Answer

(a) Homo sapiens and Homo erectus

(b) They belong to the same genus.

BINOMIAL NOMENCLATURE

Binomial nomenclature refers to the system of assigning scientific names to organisms. The scientific name is derived from combining the genus name and the specific name.

This system of giving an organism a scientific name was started by Carolus Linnaeus in the 18th century.The scientific name is given in the Latin language or made to sound Latin. This language which was widely by scientists is accepted as it does not change.

The generic name starts with a capital letter while the specificname is all written in small letters.

Example 1: The common bean plant belongs to the genus Phaseolus and species vulgaris. The scientific name of the common bean plant is therefore Phaseolus vulgaris. The domestic dog belongs to genus Canis and species familiaris. Its scientific name is thus Canis familiaris.

When hand-written, the two parts of the name are underlined separately as shown:

1. Phaseolus vulgaris

2. Canis familiaris

Example 2: The following is the scientific name of the human being:

In print the scientific name is written in italics, e.g Phaseolus vulgaris and Canis familiaris.

Background Information

In the topic Classification I you learnt about the use of a hand lens. The hand lens is a device used to magnify objects in order to see them much more clearly. Test yourself to see how much of the hand lens you can remember by naming the parts of the hand lens in the figure below.

LESSON OBJECTIVES

By the end of this lesson you should be able to:

State the purpose of the light microscope. Identify parts of the light microscope and state their functions. Use and care for the light microscope. Calculate magnification when using the light microscope

The Cell

Cells

A Light Microscope

The Light Mcroscope

In Primary Science, you learnt about water-borne diseases which are caused by tiny living things in water. The tiny living things cannot be seen by the unaided eye or the hand lens. The microscope, an instrument with greater magnifying power, is used. A microscope gives finer details of tiny objects. The commonly used microscope in schools is the light microscope.

The light microscope uses light for illumination of the specimen to be viewed. It is therefore important to know the parts of the light microscope, functions of these parts and care for the microscope.

FUNCTIONS OF PARTS OF LIGHT MICROSCOPE

PART FUNCTION

Eye piece lens: Used to magnify the specimen under viewCoarse adjustment knob: Raises or lowers the body tube for focusingFine adjustment knob: Raises or lowers the body tube for sharp focusing.

Body tube: Holds the eye piece lens and the revolving nose piece in position.Revolving nose piece: Holds the objective lens in position enabling changes from one objective lens to the other.Objective lens: Magnifies the specimen.Limb: Supports the body tube and the stage

Base/Stand: Provides steady support.Stage: Where specimen on a slide is placed. It has two clips to hold slide in position during viewing.Diaphragm: An opening which regulates the amount of light passing through condenser to illuminate the specimen.

Mirror: Reflects light through condenser to the specimen.

Use of the Light Microscope

The microscope is used as follows:

Prepare the specimen to be observed.

Place the microscope on the bench, with the stage facing away from you.

Turn the low power objective lens into position. Ensure that the diaphragm is fully open.

Look through the eye piece lens with one eye while adjusting the mirror under the stage to allow enough light.

Place the slide with the specimen (already prepared) on the stage and clip the slide into position.

Look through the eye piece while ensuring enough light passes through the specimen.

Bring the low power objective lens to the lowest point using coarse adjustment knob until the specimen comes into focus.

Use fine adjustment knob to bring image into sharp focus.

Turn the medium power objective lens in position and adjust the focus using the coarse knob. For sharper images, use the fine adjustment knob.

If more details are required, turn the high power objective lens into position then use only the fine adjustment knob to bring the image into sharp focus.

Observe and draw what you see under the microscope. Work out and write the magnification beside the drawing

The videos next illustrate how to use and care for a light microscope.

MagnificationYou are able to see microscopic structures under the microscope because such structures are magnified. The extent of the magnification is a a product of eyepiece and objective lens magnifications. Thus when using the microscope the magnification of the object/specimen viewed is given by multiplying the eyepiece lens magnification by the objective lens magnification. Eyepiece lens magnification x Objective lens magnification = Total Magnification.

However the term magnification is broader. It refers to the extent to which the specimen size has been changed. Image observed may be smaller or larger than the actual specimen. In either case, it is still a magnification.

CARE FOR THE MICROSCOPE

When using the microscope the following points should be observed:

Do not place the microscope too close to the edge of the bench/table.

When carrying the microscope, always use two hands.

To clean dirty lenses, special soft lens tissue paper or tissue

paper moistened with ethanol is used.

The low power objective lens should click into position before and after use of a microscope. This helps to avoid damaging of objective lenses.

Clean and store the microscope in a safe place free from moisture and dust.

BACKGROUND INFORMATIONIn Primary science you studied about water borne diseases such as typhoid and cholera. You learnt that such diseases are caused by tiny living organisms which cannot be seen using the unaided eye. These are therefore called microscopic organisms or microorganisms.

The microscope is used to observe such organisms.

LESSON OBJECTIVES


Identify the components of a cell as seen under the light microscope. Identify the components of a cell as seen under the electron microscope and relate their

structure to functions. Compare plant and animal cells as seen under the microscope.

Cell StructureThe basic unit of a living organism is the cell. A cell is a microscopic structure, that is, it can not be seen using the unaided eye. A microscope is used to observe cells.

Unicellular organisms, for example amoeba and bacteria are made up of only one cell. Multicellular organisms, for example humans, elephants and trees are made up of billions of cells. The main features of a plant and animal cell, as seen through a light microscope, is given next.

Cell Structure

A living organism is made up of tiny microscopic units called cells. The cell is the basic structural and functional unit of a living organism. Unicellular organisms, for example Amoeba and Bacteria are made up of only one cell. Multicellular organisms, for example humans, elephants and trees are made up of billions of cells. The main features of a plant and animal cell, as seen through a light microscope, is given next.

Using the light microscope the following parts of the cell above are seen:

Cell membrane

Cytoplasm

Nucleus

Nucleolus

Vacuole

Cell wall

Chloroplast

Cell Structure as Seen Under the Light Microscope

Under the light microscope only a few parts of the cell can be seen, as in the animal and plant cells below.

Cell Structure as Seen Under the Electron Microscope

Under electron microscope, great detail of the cell can be seen(See next panel).An electron microscope has high resolving and magnification power and uses electron beam to illuminate the specimen.Cick on the icons above to see the structures of cells seen under electron microscope.

Cell Structure as seen under the electron microscope

Activity 2

Drag and place the name on respective structures illustrated below.

Cell membrane Cell wall

Chloroplast Nucleus Cytoplasm Vacuole

Activity

Below is a generalization plant cell as seen under the electron microscope. Label the cell using names given by dragging and dropping them on the correct structure.Name of the parts:Cell wallNucleus Nucleolus Nuclear membranePlasma membraneCytoplasm Smooth endoplasmic reticulumRough endoplasmic reticulum RibosomeGolgi apparatusTonoplast Cell sapChloroplastLysosomes

Cell Membrane

This is a very thin and flexible membrane that surrounds each cell. It is also known as the plasma membrane.

This membrane has tiny pores which allow movement of some materials in and out of the cell. For example, it allows only small particles such as those of water to move across it but not the relatively large sugar molecules. It is therefore referred to as a semi permeable membrane

Activity

Pick the correct organelle from the list given to fill the blanks in the given statement.Chloroplast CentrioleTonoplastCell wallLysosomeGolgi apparatusCell sap/ sap vacuole

1 is an organelle only found in the animal cell while 2 , 3 , 4,

5 are organelles only found in plant cells.

Check for answers:

1. Centriole 2. Chloroplast 3.Tonoplast 4.Cell wall 5.Cell sap/sap vacuole.

Chloroplast

The chloroplast is the site for photosynthesis. Chloroplasts are found in plant cells but are absent in animal cells.Chloroplast is an organelle enveloped/enclosed in a double membrane that is similar to the plasma membrane.Within the chloroplasts are granal lamellae or membranes containing chlorophyll (green pigment) molecules that trap light for photosynthesis.

GAME-QUIZZ

Cell Vacuole (Sap Vacuole)

Cell vacuole is also referred to as sap vacuole.

It is surrounded by a single membrane called tonoplast.

Tonoplast is permeable to water. The size of sap vacuole varies

according to the condition of the cell.

Cell vacuole contains cell sap which is a solution of sugars, ions and waste products. Sap vacuole provides mechanical support to the cell when it is full. It also acts as storage organelle for sugars, ions and pigments.

GAME-QUIZZ

Mitochondrion

A mitochondrion appears as a sausage-shaped organelle. Each cell contains several mitochondria.It has a smooth outer membrane and extensively infolded inner membrane. These infoldings, called cristae, project into the matrix (fluid filled space) of the mitochondrion.

A Mitochondrion

This organelle is responsible for production of energy through the process of respiration. Cristae increase surface area for increased enzyme attachment and respiration. Mitochondria are numerous in very active cells such as sperm cells and intestinal cells.

Cell Wall

The cell wall is a rigid outer cover of plant cells. It is made of cellulose fibres. Cell wall gives plant cells its definite shape and provides mechanical support.It allows passage of gases, water and other substances. Cell wall is completely permeable. Due to its rigidity it prevents bursting of plant cells, even when they take in a lot of water.

GAME-EXERCISE

Activity 5-QUIZ-1Using the cell illustration provided drag and drop the function into its structure.

Function

A. Site for protein synthesis

1. Contains hereditary material and regulates all cellular activities

1. Regulates movement of material into and out of a cell.

1. Synthesize and transport lipids

1. Site for photosynthesis

1. Site for respiration

ACTIVITY 6-QUIZ-2The following are statements about the structure and functions of a cell. Fill in the blanks to complete the statements.

Centrioles are organelles in an animal cell which take part in cell division and in cilia and flagella formation.

Rough endoplasmic reticulum facilitates transport of proteins in the cells.Lysosomes contain lytic enzymes which destroy worn out cells and unwanted organelles.

Activity 7-QUIZ3

1. Illustrations A and B represent two cell organelles: Smooth endoplasmic reticulum and Golgi bodies.

Identify each of the following cell organelles by typing in their names.

With reference to plant cells, complete the table below by filling in column II the name of the structure that corresponds with the statement in column I.

COLUMN I COLUMN II1.Contains the pigment that traps solar energy 2. Contains the chemical compound that is responsible for transmitting hereditary information.

3. Acts as a selective barrier between the cell and its surroundings 4.Is composed mainly of a high molecular weight polysaccride(cellulose) 5. contains the enzymes responsible for synthesis of most of the cellular ATP 6. Contains most of the cellular solutes

Pick and drop in the right box from the listNucleus, cell membrane, cytoplasm, cell wall, mitochondria, chloroplast.

AnswersColumn I Column II

1. chloroplast2. nucleus3. cell membrane4. cell wall5. mitochondria6. cytoplasm

Golgi Body

These are complex organelles composed of a stack of closely packed flattened cavities. Numerous spherical vesicles are found at the ends of the cavities. These vesicles contain secretions.Secretions are substances made in glands and taken to other tissues to perform specific functions.A Vesicle moves to the surface of the cell and discharges its contents to the exterior, in tissue fluid.

Golgi Body

The Golgi apparatus is where packaging of glycoprotein and other materials occur. It also produces lysosomes which contain enzymes that break down wornout organelles or entire cell.

Golgi bodies are abundant in glandular/secretory cells such as liver

and salivary gland.

GAME-QUIZZ

Lysosome

These are small spherical bodies. They arise from golgi bodies.Lysosomes contain lytic enzymes which carry out the digestive processes or lysis. They digest lipids, proteins and carbohydrates. They also digest unwanted organelles and destroy old and damaged cells.

A Lysosome

Cytoplasm

Cytoplasm is the fluid part of the cell in which materials and organelles are found. It consists of a fluid medium where chemical reactions occur. It contains organelles and other inclusions such as starch, glycogen, fat droplets and other dissolved materials.

Nucleus

The nucleus is bound by a double unit called a nuclear membrane which has pores to allow exchange of materials between nucleus and cytoplasm. The outer membrane is continuous with endoplasmic reticulum. The nucleus is made up of a viscous fluid called nucleoplasm in which chromatin materials are suspended. Chromatin makes up chromosomes which carry genetic information. Nucleus carries hereditary materials and also controls the activities of the cells.

Ribosomes

They are spherical in shape, scattered within the cytoplasm and on the surface of rough endoplasmic reticulum.They are sites for protein synthesis.

Ribosomes

Centrioles

Centrioles are rod-shaped structures located outside the nuclear membrane, in animal cells. In each cell, two centrioles are found, situated at right angles to each other.Centrioles take part in cell division and in the formation of cilia and flagella.

Centrioles

Endoplasmic Reticulum (ER).

These appear as a series of interconnected channels running throughout the cytoplasm. It is continuous with outer membranes of the nucleus. Some endoplasmic reticulums have ribosomes on their surface and are called Rough Endoplasmic reticulum (RER). RER facilitates transport of proteins synthesized in the cells.

Rough Endoplasmic Reticulum

Smooth Endoplasmic Reticulum

Endoplasmic reticulum without ribosomes on its surface is called Smooth Endoplasmic Reticulum (SER). It is concerned with the synthesis and transport of lipids and steroids


Endoplasmic Reticulum (ER).

These appear as a series of interconnected channels running throughout the cytoplasm. It is continuous with outer membranes of the nucleus. Some endoplasmic reticulums have ribosomes on their surface and are called Rough Endoplasmic reticulum (RER). RER facilitates transport of proteins synthesized in the cells.

Rough Endoplasmic Reticulum

Endoplasmic reticulum without ribosomes on its surface is called Smooth Endoplasmic Reticulum (SER). It is concerned with the synthesis and transport of lipids and steroids


Centrioles

Centrioles are rod-shaped structures located outside the nuclear membrane, in animal cells. In each cell, two centrioles are found, situated at right angles to each other.Centrioles take part in cell division and in the formation of cilia and flagella.


You have learnt about the structure, functions and use of a light microscope. You have also learnt about the cell structure as seen under the light microscope and electron microscope. In this lesson, you will learn how to prepare and observe temporary slides.

LESSON OBJECTIVE

By the end of this lesson you should be able to prepare,mount and stain temporary slides of plant cells such as onion epidermal cells.

QUIZ-GAME

State whether true or false for the following statements about the previous activity.True False

1. Cell membrane, cytoplasm, chloroplast, cell wall, nucleus, tonoplast, and lysosomes are observed both in the stained and unstained temporary slides

2. Staining makes the cells more clear when viewing under the light microscope3. The specimen is placed in a drop of water to keep cells turgid. 4. Lysosomes are visible under both light and electron microscopes.

Answers.

1. False 2. True3. True

4. False

Temporary and Permanent Slides

We may observe cells on a permanent slide, or we can prepare a temporary slide of cells. Temporary slides are also called fresh slides and are used during a laboratory activity and then discarded.

A Temporary Slide seen under a light microscope

A Permanent Slide

Materials for Preparing Temporary Slides

You have already learnt about two types of microscopes. You will now learn how to prepare and observe temporary slides. To prepare temporary slides you need the following materials and apparatus:

Microscope Clean microscope slides Cover slips Scalpel / new razor blade Distilled water Onion bulb A pair of forceps Mounting needle Dropper Iodine solution

Microscope

Clean microscope slides

Scalpel / new razor blade

Cover slips

Distilled water

Onion bulb

A pair of forceps

Mounting needle

Dropper

Iodine solution

Procedure for Preparation of Temporary Slides:

Follow the following procedure for preparation of temporary slides. Cut the onion bulb vertically into two parts.This gives you a longitudinal section through the bulb.

Separate a fleshy leaf from one of the parts Remove a thin piece of epidermis from this leaf using forceps. Place a drop of water on a clean slide and quickly spread the piece of epidermis onto the drop of

water. Gently lower a clear cover slip onto the epidermis strip using a mounting needle to avoid trapping

of air bubbles. Observe this temporary slide under the low and then medium power objective lens of the

microscope Repeat the above procedure using another epidermal strip. Use a drop of dilute iodine solution

instead of distilled water, to stain the cells, then observe under the microscope.


GAME

You have already learnt about the preparation and observation of temporary slides.

Fill in the blanks in the following statement in the following statements to remind yourself of what you did in that lessonDuring preparation of a temporary slide, the specimen is placed in 1 to maintain

cell cytoplasm. The staining of the specimen makes the cells more 2 . A sharp

cutting instrument is used to avoid 3 .

Check for answers.

1. Water 2. Clear 3. Cell destruction/cell distortion

GAME 1

1. Count and estimate the number of millimeter markings that fit into the diameter of the circular field of view.

Type your answer

Illustrate field of view at lowest magnification µm with outer markings

3mm

(ii) Count the number of the cells in the row along the diameter of view.

1.

Estimate the diameter/ length of the cells in micrometers Type in your answer

Diameter/ length of one cell= Diameter of field in micrometer Number of cells across the field

Answer

(i) 3.5mm (3.3 - 3.7mm)(ii) 15 cells

1. field of view in mm= 3.5mm

field of view in µm = 3.5 X 1000= 3500µm Diameter/ length of the cells= Diameter of field in micrometer Number of cells across the fields

= 3500 15

= 233.33µm

LESSON OBJECTIVE

By the end of this lesson you should be able to observe and estimate the size of a plant cell.

GAME 2

Activity: TwoA piece of squared graph paper was placed on the stage of a microscope and its edge viewed through a *10 objective lens and *4 eye piece lens.A slide carrying several cheek cells were also placed alongside the ruler on the microscope stage.The viewer observed that each cheek cell covered about one eighth of a millimeter square (mm2).

AnswerEach cheek cell is 1/8 of a millimeter1mm== 1000µm1/8mm== (1000/8) µmDiameter of cheek cells = 1000/8 = 125µm

Estimation of Cell Size

A cell is very tiny. To estimate the size of this structure we need to use a microscope. The length and width of a fairly large organism can be measured with a ruler in millimeters. Most cells are shorter than a millimeter and therefore their sizes are measured in smaller units such as micrometers.

A Microscope

To measure this a transparent ruler with mm markings is mounted on the stage of a light microscope and the markings brought into focus in a similar procedure as when observing a specimen on a slide. The marks observed are noted and recorded to indicate the span of the field of view in millimetrs e.g. 3mm as in the figure below.

Microscope Field of View with ruler mm markings

Convert the milimetres into micrometres by multiplying the millimetres observed by 1000 e.g. (3mm X 1000 = 3000micrometres).This is the diameter of the field of view in micrometers.

Remove the plastic rule and mount an onion skin epidermis and observe under the same magnification. Count the number of cells along the diameter of the field of view.(e.g. 4 cells in the figure)

Estimate the width/length of one cell in micrometes by dividing the diameter of the field of view by the number of cells across the the field of view. (e.g. 3000 divide by 4 = 750 micrometes in the figure.) This is the estimated length of one cell.

Activity

1mm = 1000µm1cm = 10mm = 10000µmConvert 1m to micrometer

Answer1m=100cm1cm=10000µm1m= 100*10000µm =1000000µm

1µm = 1/1000 of a millimeter= 0.001mm

Convert 1 micrometer to:

1. Centimeter 2. Meter

Answer

1. 1µm = 1/1000000 th of a centimeter.2. 1µm = 1/1000000 th of a meter

=0 .000001m

Materials Required for Estimation of Cell size

To estimate the size of a cell the following materials are required:

Transparent ruler marked in millimeters

Microscope

Epidermal cells from onion bulb.

Iodine stain

Glass slide

A razor blade

Razor blade

Scalpel

Forceps

Procedure for Cell Estimation

With the low power objective in place keep the transparent ruler on the stage of the microscope Focus the microscope so that the millimeter markings are visible as thick dark lines Determine the diameter of the field by counting the number of millimeter spaces with the field. Express the diameter of the field in µm by multiplying by 1000. Remove the ruler and place the slide containing the onion epidermis on the stage. Identify a row of cells that spans the diameter of the field. Count the number of cells in the row. Estimate the diameter/ length of the cells in micrometer using the following formular:

Diameter/ length of the cells= Diameter of field in micrometer Number of cells across the field

Video tape all these stages: counting of the number of the cells from the screen.

BACKGROUND INFORMATIONYou have learnt about the structure and functions of the cell. You have

also estimated the size of a cell from a temporary slide.

Earlier you learnt characteristics of living organisms in the topic "Introduction to Biology".

In this lesson, you will learn about cells that are modified to carry out specific functions. Such cells develop a special structure which enables them to be more efficient.

Activity: 1Match each of the plant tissues in column A with its major function in column B.

COLUMN A COLUMN Ba. Meristematic 1. Transport water, salts and food

materialsb. Photosynthetic 2. To make new tissuesc. Parenchyma 3. To make food for plantsd. Epidermal 4. To support and strengthen plants.e. Vascular 5. Protect the inner delicate tissues.f. Supportive 6. Fill spaces between other tissues.

Answersa – 2 c – 6 e – 1b – 3 d – 5 f – 4

LESSON OBJECTIVE

By the end of this lesson you should be able to state

the differences between cells, tissues, organs and organ systems.

Activity

AnswersHeart…………………….OrganChloroplast……………...OrganelleNuclear………………….OrganelleCheek cell……………….CellOnion epidermis…………Tissue Onion bulb………………OrganMitochondrion…………..OrganelleLung……………………..OrganBlood…………………… Tissue

CELL SPECIALISATION

In multicellular animals and plants cells from different parts of the body differ in size, shape and contents. Each cell type has special features that enable it perform a particular function efficiently. This is described as cell specialization.

Specialised Plant Cells

The diagrams shown below are some types of plant cells that develop from an undifferentiated cell.

Specialised Plant Cells

Activity 2

GAME- Background

Activity 2:

Activity

1. Arrange the following in the correct order from the simplest to the most complex organ, cell, organelle, organ, organism, tissue.

Check answer

Organelle cell tissue organ organ system organism

If correct reinforce positively and if incorrect try again (only twice).

Specialised Animal Cells

The illustrations below are of some types of specialized animal cells that develop from undifferentiated cells:

Sperm Cell (Spermatozoon)

Nerve Cell (Neurone)

Egg Cell (Ovum)

TissuesA tissue is made up of cells of a particular type that are grouped together to perform the same functions.Below are examples of tissues.

Plant Tissues

Animal Tissues

Plant Tissues

The table below shows plant tissues, their description and functions. (Show illustration of each part)

Name of tissue Description FunctionEpidermal Single thin layer of cells covering the

outer surface of plant parts.Protects plants from mechanical damage and infection.

Photosynthetic Cells rich in chloroplasts containing chlorophyll.

Absorb light energy and manufacture food (photocy)

Vascular (conducting tissue)

Consists of xylem and phloem. Xylem – Conduct water and salts up the plantPhloem – Transport food substances.

Parenchyma Thin walled, irregularly shaped cells Packaging and storage functionsMeristematic Small, thin walled cells which retain

ability to divide throughout their life.To make new cells

Animal Tissues

The following table shows some animal tissues.

Name of tissue

Description Functions

Epithelial Thin continuous layer of cells. Lining and protection of internal and external body surfaces.

Muscle Bodies/ sheets of elongated cells with fibers that can contract.

Contract and relax to bring about movement.

Blood Fluid containing red and white blood cells, platelets and dissolved substances.

Transport gases, nutrients and other dissolved substances.Protect the body against Functions.

Connective Consists of strong fibres. Connects other tissues and organs holding others together in position.

Organs

An organ is a group of different tissues working together to perform a specific function, for example the mammalian heart.

The heart is made up of the following tissues:

Epithelial tissue

Muscular tissue,

Connective tissue

Blood tissue

Mammalian Heart

The heart pumps blood around the body. It is made up of various tissues.

Epithelial tissue Muscular tissue

Blood tissue Nerve tissue Connective tissue

Functions of Tissues of Mammalian Heart

The table below is a summary of the various tissues which form the heart.

(Let each tissue appear as it is mentioned).

Tissue Role1. Connective tissue

Binds other tissues together

2. Blood tissue Transports oxygen and nutrient needed for energy production. Also removes carbon dioxide and nitrogenous wastes.

3. Muscular tissue

Contracts and relaxes causing the pumping action of the heart.

4. Epithelial tissue

Protects the inner tissues

5. Nerve tissue Receives signals and informs the heart about the heartbeat rate

This is an example of different tissues functioning together in an organ. The organ is then able to perform its functions.

Other Human Organs

Other organs composed of several tissues in animals include liver, brain, stomach, kidneys, lungs, gills and skin.

HEART

PLANT ORGANS

Plant organs include the leaf, roots, and stems.The root is composed of epidermal tissue, vascular tissue and parenchyma tissue.

Vascular tissue Parenchyma tissue

ROOT

Epidermal tissue

Organ Systems

An organ system is a system consisting of several organs working

together to perform a specific function.

An example of an organ system is the digestive system in humans.

This system is composed of the following organs:

Mouth Oesophagus Liver Stomach Pancreases Intestines

Human Digestive System

Other human organ systems include:

Circulatory system

Excretory system

Respiratory system (Breathing/Gaseous Exchange)

Reproductive system

Female

Male

Nervous system

Organs and organ systems work together to form an independent, whole organism.

ASSIGNMENT

Project Work

Find out the organ systems which make up a plant. State the main functions of each organ system.


In Primary Science, you learnt that molecules exist in three states of matter; solids, liquids, and gases. You have also learnt that the cell membrane controls the movement of molecules in and out of the cell.In this lesson you will learn how these molecules move across the cell membrane and the factors affecting their movement.

You will also learn the importance of the movement of these molecules to living organisms.

LESSON OBJECTIVESBy the end of this lesson you should be able to:

1. Define the term diffusion2. Demonstrate diffusion of substances in gaseous, liquid, and solid media.3. Describe four factors that affect the rate of diffusion.4. State four roles of diffusion in living organisms.

Cell Physiology

Molecules needed for cellular activities move into the cell across the cell membrane. Some of the manufactured materials pass out of the cell to be used for various activities. Cell physiology refers to to the cellular activities including the movement of materials into and out of the cell across the cell membrane. Materials taken in include water, oxygen, food substances, vitamins and minerals. The products of cellular activities which cells release to their environment include secretions and waste products. The processes through which this exchange occurs include diffusion, osmosis, active transport, phagocytosis and pinocytosis. In this lesson we will discuss the first three of these processes: diffusion, osmosis and active transport.

CELL PHYSIOLOGY

Diffusion

Diffusion

Diffusion occurs in gases, liquids, and solids as demonstrated in the following activities.

GAMEActivity 2

Q. Drag and drop the substances that can dissolve in water from the list below.Basin with water is shown.List of substances

1. glucose 2. chalk dust3. soil4. ash5. salt

Correct answer – glucose, saltIncorrect - try again

ActivityAn animation of a scientist pouring cold water into two beakers labeled A and B. one beaker (B) heated until boiling. Crystals of equal mass of potassium permagnate are dropped using a glass tube are dropped to the two beakers A and B having cold and hot water simultaneously. A stop watch is then set to show how long it takes for the water to have a uniform purple colour.

Question: 1

In which beaker did it take the water to have a uniform purple colour faster?Click either r A or B button.

Correct answer – beaker BIncorrect answer – try again – beaker AQuestion: 2Explain your answer in question 1 above. Type your answer in the box below.

Once student types his/her answer the correct explanation appears in word and print.

Diffussion in Gases

GAME

Factors Affecting the rate of Diffusion Temperature

Increase in temperature increases the rate of movement of molecules hence increases the rate of diffusion while decrease in temperature decreases the rate of movement of molecules.

As temperature increases the kinetic energy of the molecules increase making them to move faster and further from each other while drop in temperature decreases kinetic energy of molecules.

ACTIVITY

Q. Explain what happened to the potassium permagnate crystals at the end of the experiment. Type your answer in the space below.

After the student types his answer the correct explanation appears in both print and voice. Voice says “the potassium permagnate crystals dissolve in water and spread evenly until the whole water environment is coloured purple.”

DIFFUSION IN LIQUIDS

Potassium permanganate crystals dissolve in water and spread evenly until the whole water environment is coloured purple. Rate of diffusion in liquids is slower than in gases.

FACTORS AFFECTING RATE OF DIFFUSION

Temperature:

Activity

An animation of a scientist pouring cold water into two beakers labeled A and B. one beaker (B) heated until boiling. Crystals of equal mass of potassium permagnate are dropped using a glass tube to the two beakers A and B having cold and hot water simultaneously. A stop watch is then set to show how long it takes for the water to have a uniform purple colour.

Question: 1In which beaker did it take the water to have a uniform purple colour faster?Click either r A or B button.

Correct answer – beaker BIncorrect answer – try again – beaker AQuestion: 2Explain your answer in question 1 above. Type your answer in the box below.

Once student types his/her answer the correct explanation appears in word and print.

Temperature

Increase in temperature increases the rate of movement of molecules hence increases the rate of diffusion while decrease in temperature decreases the rate of movement of molecules.

As temperature increases, the kinetic energy of the molecules increases, causing them to move faster and further from each other while drop in temperature decreases kinetic energy of molecules. This makes molecules to move more slowly and closer to each other.

Surface area to volume ratio

ActivityVideo shooting: A scientist obtains two large blocks of Copper II sulphate crystals. One of the crystals is crushed into fine powder. They are then dropped simultaneously into two beakers containing warm water (beaker A has large particles while beaker B has fine/powdery crystals).

The solutions in the beakers are stirred gently for about 1 minute. (Use a stop watch to time.)Q1. In which beaker did the crystals take a shorter time to dissolve and diffuse evenly? Click the correct answer.

Beaker A Beaker B

Q2. Explain your observations in the above experiment. Type your answer in the space below.

Surface Area to Volume Ratio

Small particles expose a large surface area to volume ratio to their surrounding compared to large particles. As a result more molecules from small particles dissolve and diffuse compared to the molecules of the large particles.

Diffusion Gradient

ActivityA video shooting of dissolving potassium permagnate in water of different volumes.Put equal volumes of potassium permagnate crystals in two beakers. In beaker A add a little water (10ml), and in beaker B add much water (20ml). Let to stand for 5 minutes observe the colour of water in both beakers.

Questions

1. In which beaker was the colour more intense.

Beaker A Beaker BClick the correct answer.Explain what you have observed in the demonstration. Type your answer in the box below.

Diffusion Gradient

Diffusion gradient refers to the diffrence in concentration between two regions.

The greater the difference in concentration of a substance between two regions the faster the rate of movement of those molecules from the region of higher concentration to the region of lower concentration, until an even concentration or equilibrium is achieved.

Size of Molecules

Small and light molecules diffuse faster than large and heavy molecules.Gas molecules diffuse faster than liquid molecules while liquid molecules diffuse faster than solid molecules.

Importance of diffussion. Diffusion is important to living organisms for the following reasons:

Absorption of digested food nutrients from the small intestine into the blood stream

Gaseous exchange

Removal of metabolic wastes from cells

Transport of synthesised food from the leaves to the rest of the plant body

Absorption of food nutrients by cells.


In Primary Science you learnt that mixtures of solids

and liquids can be separated by sieving and filtering

methods. A filter paper and a piece of clothing were used

to separate soil and water. You have also learnt about

the movement of substances into and out of the cell.

In this lesson you will learn how water molecules move across

the cell membrane, factors influencing their movement and

importance of their movement to living organisms.

ActivityQ. Why did the soil particles remain trapped on the piece of cloth while water passed through?Type your answer in the space below.

LESSON OBJECTIVES


1. Explain the term osmosis2. Describe two factors which affect the rate of osmosis.3. Explain four roles of osmosis in living organisms

QUIZ - GAME

1. Explain the meaning of the following terms. Type in your answers.

1. Osmosis2. Osmotic potential3. Plasmolysis4. Haemolysis5. Turgor pressure 6. Osmotic pressure

2. What would happen to the rate of osmosis in a living organism if

1. The temperature was increased to 400C.2. The temperature was raised above 400C.3. State four roles of osmosis in living organisms.

a) Osmosis is the movement of water molecules from a dilute solution to a concentrated solution through a semi permeable membrane. It can also be looked at as the movement of water molecules from a region of high concentration to a region of low concentration of water molecules through a semi permeable membraneb) This is the ability of a concentrated solution to draw in water molecule by osmosis when separated from a dilute solution by a semi permeable membrane.

Answers

1. This is the shrinkage of the protoplasm away from the cell wall due to loss of water by osmosis.2. This is the bursting of red blood cells when placed in a placed in a hypotonic solution due to

excessive uptake of water by osmosis.

3. This is the pressure that is exerted on the cell wall by the protoplasm as a result of the plant cell absorbing water by osmosis.

4. This is the pressure requires to stop flow of water molecules into a solution by osmosis.5. a) The rate of osmosis will increase.b) Osmosis will stop because the cell membrane will have

been destroyed.

Introduction

The illustration shown indicates the process of osmosis across a semipermeable membrane. The small particles represent water molecules while the large ones represent salt molecules. The semipermeable membrane is a visking tubing.

Osmosis is the movement of water molecules from a region of high concentration of water molecules to region of low concentration of water molecules through a semi permeable membrane.

Osmosis can also be defined as the movement of water molecules from a dilute solution to a concentrated solution through a semi permeable membrane. A semi permeable membrane is a membrane that allows some substances to pass through but not others. It has pores which allow substances made up of small particles to pass through but not the large ones. The illustration shows osmosis of water molecules across a semi permeable membrane.The smallest molecules are water molecules while the largest molecules are salt molecules. The semi permeable membrane used is a visking tube.

Osmosis across a cell membrane

ActivityQ. From the illustration of dirty water using a piece of cloth suggest the meaning of a semi permeable membrane.

ActivityThe list below contains three semi permeable membranes. Identify them by clicking the button beside each.

Polythene bag Cows bladder Visking tubing Filter paper Piece of cloth Cell membrane

Factors Affecting the Rate of Osmosis

The rate of osmosis is affected by concentration gradient, temperature and the thikness of the membrane across which the process is taking place.

Concentration Gradient

This refers to the difference in concentration between adjacent regions. In the figure below the solution in visking tubing A is more concentrated compared to that in visking tubing B.

Water molecules from the beaker move into visking tubing A at a faster rate than in visking tubing B. This is because there is a higher osmotic gradient between the water in the beaker and the solution in visking tubing A compared to the difference in concentration between the water in the beaker and visking tubing B.

The concentrated solution in visking tubing A is referred to as hypertonic solution while the distilled water in the beaker is referred to as a hypotonic solution.

Hypotonic and Hypertonic solutions

A hypertonic solution is a more concentrated solution than the surounding. It has a lot of solute molecules and a few solvent molecules. A hypotonic solution is a dilute solution, compared to the surounding. It has a lot of solvent molecules and few or no solute molecules.Isotonic solutions refer to two solutions of equal concentration.

NB:Plant and animal cells gain water when put in a hypotonic solution and lose water when put in a hypertonic solutions.

GAME

Q1. What happens to the water molecule when the temperature increases up to 400c?Click on the suggested answer below

Molecules move across the membrane at a faster rate. Molecules move across membrane Molecules move across membrane at slow rate No change in rate of movement of water molecules

Temperature

Molecules of water in a container vibrate at a slow rate when the temperature is low.The rate of osmosis is equally low. As temperature is increased the rate of osmosis increases due to increase in movement of solvent molecules.

Further increase in temperature, up to 40 degrees Centigrade causes water molecules to move faster but they do not cross the semi permeable membrane. This is becausethe plasma membrane is protein in nature. Temperatures of 40*C and above denature the semi-permeable membrane and therefore stop osmosis from taking place.

GAME

Q2. Explain the observation in the set up.Type your answer below.

After student types answer the following print and voice appears.“The solution in Visking tubing A is less concentrated compared to that in Visking tube B. Water molecules from the beaker moves into Visking tubing B at a faster rate than in Visking tubing A, this is because there is a higher osmotic gradient between the water in the beaker and the solution in the Visking tubing B compared to the difference in concentration between the water in the beaker and Visking tubing A.”

Thickness of membrane

Most membranes in the body are thin to ensure that molecules move across at a faster rate.

Molecules take a longer period of time to cross thicker membranes.

Water Relations in Plants

A plant cell placed in hypotonic solution gains water. This ability of a concentrated solution to draw in water by osmosis is called osmotic potential. As the cell draws in water it develops an osmotic pressure. This is the pressure required to stop flow of water into a solution across a semi-permeable membrane

Turgor Pressure and Wall Pressure

When a plant cell is placed in a hypotonic solution (dilute solution) it gains water by osmosis. The cell sap increases in volume, pushing the protoplasm against the cell wall. The resultant internal pressure pushing the protoplasm against the cell wall is called turgor pressure. When the cell wall is being stretched out ward it develops a resistant pressure on the outside. This is known as wall pressure. Wall pressure is the pressure which acts against the cell protoplasm to oppose the turgor pressure. When the cell wall can no longer stretch then the cell is said to be fully turgid. When the cell is fully turgid the wall pressure is equal to the turgor pressure.

Illustration of Turgor Pressure and Wall Pressure in a Plant Cell

Plant Cells in Hypertonic Solution

A cell is placed in a more concentrated or hypertonic solution will loose water molecules to that solution by osmosis. The cell protoplasm detaches itself from the cell wall. This is called plasmolysis. During drought, plants lose water by transpiration at a faster rate than the root hair cells are absorbing water from the soil. This leads to the cells loosing turgidity and the tissues become flaccid. This leads to wilting of the plant.

Water Relations in Animal Cells

When an animal cell such as a red blood cell is placed in a hypotonic solution it gains water by osmosis. Volume of the cytoplasm increases, creating an outward pressure on the cell membrane.

The cell swells and eventually bursts because the cell membrane cannot resist the outward pressure. The bursting of red blood cells when placed in a hypotonic solution is called haemolysis.

When placed in hypertonic solution the cells lose water and shrink or become crenated.

Animal Cell in Hypotonic and Hypertonic solutions

Animal cell in hypertonic and hypotonic solution

When an animal cell such as red blood cell is placed in hypertonic solution it looses water by osmosis to the surrounding solution. This makes the cell to shrink such that the cell membrane appears wrinkled. This is known as crenation.

A hypotonic solution surrounding an animal cell causes that cell to absorb water by osmosis. This may lead to swelling and eventually bursting of the cell. This condition is known as haemolysis.

Animation of an animal cell subjected to hypotonic and hypertonic solutions.

Role of Osmosis in Living Organisms Osmosis is important to living organisms for the following reasons:

Support: Plant cells take in water by osmosis and become turgid. This makes the plant tissues to become firm and rigid hence providing support. This support is important in seedlings, leaves and herbaceous plants which are less woody.

Absorption of water from soil: The root hair cells have a higher concentration of salts compared to the solution in soil . This provides a suitable osmotic gradient for water to enter the root hair cells by osmosis. Water moves from the cell within the plant by osmosis.

Structures associated with absorption of water from the soil

iii. Opening and closing of the stomata: During the day the guard cells have a higher concentration of sugars than the surrounding epidermal cells. This makes water to enter the guard cells by osmosis, subsequently making them turgid. The stomata opens up. At night the concentration of sugars in the guard cells is lower than the surrounding epidermal cells. This makes the guard cells to lose water by osmosis and become flaccid. The stomata closes up. The illustration shows an open and cosed stomata.

iv. Osmoregulation: Movement of water in and out of the blood balances the concentration of fluids in the blood and tissue fluid.

Summary of osmosisIn this lesson you have learnt the following:

Osmosis is the movement of water molecules from a dilute solution to a concentrated solution across a semi permeable membrane. Rate of osmosis is affected by temperature and the osmotic gradient between solutions separated by a semi permeable membrane. Osmosis is important to living organisms since it absorbs water from the soil and the stomata to open and close it and also enables herbaceous plants, seedlings and leaves to have support.


You have learnt that molecules move from where they are highly concentrated to where their concentration is low by osmosis and diffusion.

In certain circumstances, molecules move from where they are less concentrated, through a semi-permeable membrane, to where they are highly concentrated. This movement which occurs against the concentration gradient requires energy. The process involved in such movement is known as ACTIVE TRANSPORT.

Activity

An animation of movement of a stone up and down the slope.

Direction of movement

Q1. in which of the two illustrations is energy required to move the stone?

A B

Click the correct answer.Correct answer: B

LESSON OBJECTIVES


1. Explain the term active transport2. Describe five factors which affect active transport.3. State five roles of active transport in living organisms.

QUIZ-GAME

Type in your answers in the space providedQ1. Explain two uses of active transport in:

1. Plants

i)ii)

1. Humans

i)ii)

Q2. Explain how the following factors affect the rate of active transport.

1. Temperature2. Oxygen concentration3. Enzyme inhibitors

Q3.The illustration below shows two physiological processes occurring in a cell.

1. Identify the two physiological processes.

Give two differences between processes (a) and (b).

Active Transport

Sometimes solute molecules move from where they are less concentrated to where they are more concentrated across a semi-permeable membrane. They are then said to move against a concentration gradient. The process is known as active transport and energy is used.

This can be compared to the energy required to roll a stone uphill. Active transport is unlike diffusion and osmosis where materials move along a concentration gradient and energy is not required. This is equivalent to a stone rolling downhill.

ACTIVITYQ2. Explain your answer in one above

Type your answer in the box below

The correct answer appears after student types the answer.Correct answer energy in requires to move stone B up the slope against force of gravity.From the illustration above define Active transport. Type your answer in the box below.

Correct answer. Active transport is the movement of substances across a semi permeable membrane against concentration gradient. The process requires energy. The energy is generated within the cell. Active transport takes place only in living cells.

Factors Affecting Active Transport

Any factor that affects energy production affects rate of active transport. Factors affecting rate of active transport include the following: Oxygen concentration, Temperature, Enzyme inhibitors, pH, Co-factors and Co-enzymes.

Oxygen Concentration

Oxygen is used to break down food to release energy. When the concentration of oxygen is low, less energy is produced; hence rate of active transport is slow. The higher the oxygen concentration the more energy is released and therefore the rate of active transport is increased.

TemperatureIncrease in temperature up to optimum levels increases rate of chemical reactions that release energy in the cell. Increase in energy increases the rate of active transport.Temperatures above optimum levels denature enzymes that speed up chemical reactions. This results in low energy production and therefore rate of active transport is slowed down.Low temperatures inactivate enzymes hence less energy is produced. This slows down active transport.

Enzyme inhibitors

Enzyme inhibitors are substances that slow down the rate of enzyme activity. Presence of enzyme inhibitors slows down the rate of active transport. These block the enzyme active sites which makes it hard for the enzymes to bind and react with the substrates.

pH

This is the acidity or alkalinity of a solution. Some enzymes function best in acidic, alkaline or neutral pH. If the pH of a chemical reaction is altered, enzyme activity will be slowed down or stopped. This will slow down or stop energy production. Consequently active transport will be slowed down or may stop.

Effect of pH on Enzymes A and B.

Co-factors and Co-EnzymesCo- factors and Co-enzymes are substances that activate enzymes. Their presence increases the rate of chemical reactions leading to more energy production. This increases rate of active transport.

Role of Active Transport in Living OrganismsActive transport is used by various organisms for different purposes such as:

1. Absorption of digested food from the alimentary canal into blood stream.2. Absorption of mineral salts from soil by roots.3. Excretion of metabolic waste products from body cells.4. Reabsorption of sugars and some salts by the kidney.5. Accumulation of substances into the body to offset osmotic imbalance in the body especially for

organisms in arid and saline environments.

Summary

In this lesson you have learnt that: 1.Active transport is a physiological process that controls the movement of important substances into and out of the organism, across cell membranes.2. This is an energy-consuming proces, occurring only in living cells.3. Active transport is affected by; TemperaturepH changeOxygen concentrationEnzyme inhibitorsCo-factors and coenzymes


In the topic Introduction to Biology you learnt that plants make their own food through the process of photosynthesis. This is one of the most important processes in nature. It ensures the survival of both plants and animals. In this lesson you are going to learn how this process takes place and the structures involved. You will also learn about the conditions that affect photosynthesis.

LESSON OBJECTIVES


Define photosynthesis State the importance of photosynthesis in nature Describe the structure of the leaf Describe structure and function of the chloroplast Describe the process of photosynthesis Explain at least three factors affecting photosynthesis Explain at least five ways in which the leaf is adapted for photosynthesis.

Nutrition

In this topic you will learn about nutrition in plants and animals

Activity

Q2. List the requirements for the process to take place .type and check the answer.Answer-

Water Carbon dioxide Light

Photosynthesis

Plants are said to be autotrophic in nature. This means that they make their own food. They do not depend on other organisms for food. The process by which plants manufacture their own food is reffered to as photosynthesis. In the process Carbon (IV) Oxide and water react using sunlight.

The light energy from the sun is trapped by the green colouring matter in the plants called chlorophyll.

External Structure of the Leaf

Photosynthesis takes place mainly in the leaves. The figure shows external parts of a leaf.

ACTIVITY

In the illustration of the internal structure of the leaf, identify the three types of photosynthetic cells. Type your answers in the boxes.

Correct answers.

Palisade cell Spongy mesophyll cell Guard cells

Internal Structure of the Leaf

The leaf's internal structure is adapted to maximise efficiency for photosynthesis. Study the illustrated transverse section of the leaf.

A thin transverse-section of the leaf observed through the light microscope would appear as shown in the illustration below.

Transverse Section through a Leaf

The process of photosynthesis takes place in structures called chloroplasts. Chloroplasts are disc-like structures found in the cytoplasm of photosynthetic cells.

L.S of a chloroplast

Chloroplasts in a palisade cell

ACTIVITY

What makes the grana appear green?

Type your answer in the box

Answer

Chlorophyll

The grana contain chlorophyll molecules which trap light energy from the sun.

Structure of a Chloroplast

The illustrations below outline the location and structure of chloroplasts.

The Grana

The grana are membraneous structures containing chlorophyll molecules on their surface. These trap light energy from the sun.

The Stroma

The stroma is the fluid matrix in which the grana are suspended.

Stages of Photosynthesis

The process of photosynthesis takes place in the chloroplast in two distinct stages: Light stage and Dark stage. In the Light stage light energy is used to break water in the leaves into Hydrogen ions and Oxygen as illustrated.

Formation of Hydrogen ions and Oxygen from water during the Light stage of photosynthesis

Light Stage

This is a light-dependent stage. It occurs in the granum of the chloroplast.In this stage light energy from the sun is absorbed by chlorophyll molecules.Light energy is used to split water molecules into Hydrogen atoms and Oxygen gas is produced. The process of splitting water molecules is called photolysis.

Some of the light energy absorbed by chlorophyll molecules is used to form an energy-rich compound called Adenosine Triphosphate (ATP). Oxygen is released into the atmosphere as a by-product.

Dark Stage During the dark stage Hydrogen atoms and ATP from the light stage enter the stroma of the chloroplast. Hydrogen atoms reduce Carbon (IV) Oxide from the atmosphere to form glucose. Energy is from ATP.

This process is called Carbon dioxide fixation. Water is produced as a by-product.

.

Testing for Starch in a Leaf

The simple sugar formed during photosynthesis is converted into starch and stored in the leaves. The presence of starch in the leaf is evidence that photosynthesis has taken place. Test for starch in a leaf can be done through a simple procedure.Materials and Apparatus requred for this process include:

A leafy potted plant which has been kept in the dark for at least 5 hours Droppers, Beakers, Source of heat, Boiling tubes, Forceps, a tripod stand, Methylated spirit,

Iodine solution, White tile

Droppers

Beaker with water

Source of heat

Boiling tube

Forceps

Tripod stand

Products of PhotosynthesisActivity

Drag and drop each of the products of photosynthesis listed below into the correct stage of photosynthesis.

Answers.Light stage

Hydrogen atoms Oxygen ATP

Dark Stage

Simple sugar Water

Procedure for Testing for Starch

Boil water in a beaker Detach one leaf from the potted plant Dip the leaf in the boiling water for three minutes. This stops chemical activity/photosynthesis in

the leaf Remove the leaf from the hot water using forceps Put the leaf in the boiling tube containing methylated spirit and stand the tube in the beaker

containing boiling water until all the green colour has been dissolved out of the leaf Remove the leaf from the methylated spirit and dip it in warm water. This softens the leaf Spread the leaf on the white tile Add drops of iodine to cover the whole leaf. Record your observation

Activity

1. Match the procedure below to the reasons why they were carried out.

Procedure Reason

Use leaf that had been exposed to light. To soften leafDropping the leaf into boiling water. To remove chlorophyllBoiling the leaf in methylated spirit To kill the leaf

2. Why was it necessary to boil the leaf indirectly in the methylated spirit? Type and check for the answer.Answer: Methylated spirit is highly inflammable.

3. Observe the following illustration on photosynthesis before the setup. The plant had been kept in the dark for 24hrs.

Why was the plant kept in the dark for 24hrs?

Insert a potted leaf in which two leaves are treated as follows: one is put in a conical flask containing Sodium hydroxide pellets and another is covered with a strip of Aluminium foil.

This setup was exposed to light for five hours.

1.

A

B

C

To absorb water

To keep off carbon dioxide

To manufacture starch

DAnswer D

1. What role is played by the Aluminium foil?

A

B

C

D Answer B

1. Why was sodium hydroxide included in the conical flask?

A

B

C

4. Leaf A, B and C were tested for starch .Drag and drop the correct results to the matching leaf.

To remove starch

To let light into leaf To prevent light reaching leaf

To absorb light

To warm the leaf

To absorb carbon dioxide To absorb oxygen

To add nutrients

To absorb water

Leaf A

Leaf B

Leaf C

a

b

Conclusion from starch test:A leaf in which photosynthesis took place would turn blue black. This color indicates the presence of starch in the leaf. Starch would have been formed from the sugar produced during photosynthesis.

In the absence of starch there would be no color change.

a) Light Intensity

Activity

Drag the button along the horizontal axis in the illustration below. Note and record your observation in the box.

Insert a graph of rate of photosynthesis against light intensity.Animate the curve so that as the button moves along the horizontal axis. it rises up to the optimum point when it levels off.

Correct Observation.As the light intensity increases the rate of photosynthesis increases up to optimum

No starch Starch present in the whole leaf

Starch present in some parts of the leaf

Why does the curve level off after the optimum point? Type your answer in the box and check for correct answer.

Correct answer.Another factor such as CO2 concentration must be limiting the rate of photosynthesis.

Factors Influencing the Rate of Photosynthesis

The rate of photosynthesis is affected by Light intensity, Carbon dioxide concentration and temperature.

Effect of Carbon (IV) Oxide on the rate of Photosynthesis

The graph indicates how the rate of photosynthesis changes with increase in Carbon (IV) Oxide. Note that the rate increases until a maximum beyond which further increase has no effect. At this time other factors other than Carbon dioxide become limiting.

Effect of Carbon (IV) Oxide concentration on the rate of photosynthesis

Effect of Temperature on the Rate of Photosynthesis

The rate of photosynthesis increases with increase in temperature up to an optimum temperature of between 30 to 40 degrees centigrade. Any further increase in temperature leads to a slow down in the process. The process stops at 60 degrees. This is because photosynthesis s controlled by enzymes. At low temperatures enzymes are inactive. They are most active at between 35 and 38 degrees Centigrade but are denatured at temperatures above 40 degrees Centigrade.

Activity

b) Carbon Dioxide Concentration Drag the button on the horizontal axis in the illustration below .note and record your observation in the box.

Observation.As the carbon dioxide concentration increases the rate of photosynthesis increases up to optimum

Why does the curve level off after the optimum point? Type and check for the answer.

Answer

Another factor such as temperature must be limiting the process.

c) Temperature

ActivityDrag the button along the horizontal axis in the illustration and record your observation in the text box.

ObservationAs temperature increases the rate of photosynthesis increases up to optimum it slows down and then stops.

Why does the rate of photosynthesis slow down and finally drop as temperature is increased? Type your answer and check for the correct answer.

Answer.

Insert a graph of rate of photosynthesis against carbon dioxide concentration. Animate the curve so that as the button moves along the horizontal axis, it rises until the optimum and then levels out .

It slows down as the enzymes are being denatured.

Drops when all enzymes have been denatured.

Adaptation of the Leaf to Photosynthesis

The leaf is adapted for photosynthesis. Adaptations of the leaf increase efficiency of this process.

Adaptive features of the leaf include:

Broad flat lamina to provide large surface area for absorption of carbon dioxide and sunlight.

Thin, to allow light to pass through a short distance to reach photosynthetic cells.

Has stomata, through which Carbon dioxide diffuses into the leaf.

Extensive veinsto conduct water and mineral salts to photosynthetic cells and carry manufactured food to other parts of the plant.

Large air spaces in the spongy mesophyll to allow gases to circulate easily.

Regular arrangement of leaves on the stem (leaf mosaic) minimizes overlapping and overshadowing. This allows maximum exposure of the leaf to light.

The palisade cells have more chloroplasts than the spongy mesophyll cells. They are located on the upper surface of the leaf to trap maximum light.

TS of leaf showing chloroplasts in palisade and spongy mesophyll cells.


In Primary School, you learnt about digestion or breakdown of food into simple substances that can be absorbed into the body. The chemical compounds used to break down the food into simple substances are called enzymes. In this lesson you are going to learn about enzymes.

ACTIVITYYou have already learnt about carbohydrates, proteins and lipids.State the building blocks of these compounds:

Carbohydrate

Proteins

Lipids

LESSON OBJECTIVES


Define an enzyme State at least four properties of enzymes Explain at least four factors that affect enzyme-controlled reactions.

NUTRITION IN ANIMALS

Animals require food materials such as carbohydrates, proteins and fats. From these materials the organism extracts nutrients which are the building blocks of the food materials.

To obtain these building blocks from the large molecules, enzymes are required.Enzymes are organic biological catalysts. A catalyst is a substance that speeds up the rate of chemical reactions. Enzymes are therefore necessary because in their absence chemical reactions in living organisms would be too slow to sustain life.

Insert an illustration of a reaction with enzyme and one without enzyme as shown below.

Large molecule Small molecules

Animate such that the arrow moves slowly along with the small molecules.

Large molecule Small molecules

Animate such that the movement of the arrow and the formation of small molecules is very fast.

PROPERTIES OF ENZYMES

1.Enzymes are protein in nature. Any factor that affects a protein will therefore affect an enzyme.

2.Enzymes are specific to the reactions they catalyse i.e. a given enzyme will only act on a particular type of substrate, for example, an enzyme that breaks down a protein cannot break down a carbohydrate.

Insert an illustration to show two different molecules in the presence of a particular enzyme.Reaction 1.

Animate the reaction to show the enzyme breaking down the substrate and the formation of product. This illustration should be raised and indicate that enzyme is not used up in the reaction.Reaction 2.

Animate to show enzyme knocking on the substrate molecule.

3. Enzymes are not used up in the reactions they catalyse. They remain unchanged and can be used repeatedly.

4.Many of the reactions they catalyse are reversible.

Animate the illustration to show breakdown of substrate into products and enzyme recombining products back into substrate molecule.

Factors that Affect Enzyme-Controlled Reactions

Enzymes are protein in nature. They are therefore affected by various factors. Enzyme-controlled reactions are in turn influenced by factors that affect enzymes. Any factor that affects the enzyme affects the reaction as well. The following are factors that affect enzyme-controlled reactions:

1. Temperature2. pH3. Substrate concentration4. Enzyme concentration5. Co-factors and Co-enzymes6. Enzyme inhibitors.

ACTIVITY

Effect of temperature on enzyme controlled reactions.

Drag the button along the horizontal axis in the illustration below. Record your observation in the box. Check for the answer

AnswerAs the temp increases the rate of reaction increases up to 35oC then drops at 60oC.

From the graph, identify the temperature at which the rate of reaction is maximum. Type and check the answer.

Correct answer: 35oC

This is the optimum temperature for the enzyme i.e. the temperature at which the enzyme works best.The optimum temperature varies for different enzymes.

Describe the shape of the graph between;a) 0- 10*C.Type and check for the answer

AnswerRate of reaction is slow.This temperature is too low and the enzymes are therefore inactive.

b) 10-35*C. Type and check for the answer

AnswerRate of reaction increases rapidly.This is because the enzymes are activated as the temperature rises up to the optimum.

c) 35-60*C. Type and check for the answerAnswer The rate of reaction decreases and stops altogether at 60*C .

This is because above the optimum temperature, enzymes get denatured and permanently destroyed at 60*C.

Temperature

Enzymes work best within a narrow range of temperature. Each enzyme has a specific optimum temperature at which it has maximum effect on the rate of reaction.

Carry out the activity provided to investigate the effect of temperature on an enzyme-controlled reactions.

ACTIVITY

Drag button A along the horizontal axis in the illustration below .Record the optimum pH.Check for the answer.

Answer:

Optimum pH is 2.0

Drag button B along the horizontal axis in the illustration below. Record the optimum pH.check for the answer.

Answer:

Optimum pH is 8.0

Insert two curves on the same axis such that when a student drags button A along the horizontal axis, it describes curve for enzyme A. when he drags button B it describes curve for enzyme B. Use different colours for curve A and B.

If the pH increases beyond the optimum for a particular enzyme, the enzyme becomes denatured.For example, enzyme A which work best at pH 2 will get denatured at pH 6

pHThis is the degree of alkalinity or acidity of a solution. pH scale ranges from 0-14.

Enzymes are protein in nature hence they are sensitive to changes in pH. Some work best in acidic medium while others work best in alkaline medium.

ACTIVITYDrag the button along the horizontal axis in the illustration below showing the rate of reaction against substrate concentration. Record your observation in the box. Check for the answer.

AnswerAs the substrate concentration increases, the rate of reaction increases up to a certain point and then levels off.

Explanation (voiced together with text)Increasing the substrate concentration increases the number of molecules being acted on by the enzymes present. The graph levels off because all the active sites of the enzyme are occupied. It is the enzymes concentration that is now limiting the rate of reaction.

Insert a curve of rate of reaction against substrate concentration. Animate button to dragged horizontally by learner.

Substrate concentrationIncreasing substrate concentration increases the number of molecules being acted on by the enzyme. This therefore increases the rate of reaction up to a maximum level as illustrated in the activity provided. Carry out the activity.

You notice that the rate of enzyme controlled reaction changes with variation in the substrate concentration. The reaction increases with increase in the amount of the substrate up to an optimum level when no further increase in reaction occurs. This is when all enzyme active sites have been occuppied by substrate molecules.

The graph shows how the rate of enzyme controlled reactions varies with substrate concentration.

Enzyme Concentration

The rate of reaction increases with increase in the enzyme concentration. This remains true as long as the substrate concentration is in the excess of the enzyme.


Increasing enzyme concentration increases the number of active sites available for substrate molecules. This therefore increases the rate of reaction until when all substrate molecules have reacted and the reaction stopped.


Co-factors and Coenzymes

Co-factors increase the rate of enzyme-controlled reactions. This is because co-factors make enzymes more active. Organic co-factors are known as co-enzymes while inorganic ones are mettalic ions such as Copper, Iron, Magnessium and Zinc.

Organic co-factors (coenzymes) include vitamins.

InhibitorsAn inhibitor is a chemical substance that blocks the activity of an enzyme, thereby reducing the rate of reaction.The inhibitor competes with the normal substrate for the active site of the enzyme.

Some inhibitors temporarily occupy the enzyme active sites while others do so permanently.Examples of inhibitors include poisons such as Cyanide, Mercury, Arsenic and compounds of Silver, which permanently occupy the active sites, rendering the enzyme unavailable for the reaction.

ACTIVITYAIM: To investigate the presence of enzyme catalase in a living tissue.

Requirements:

3 pieces of 1cm3of fresh mammalian liver

10ml hydrogen peroxide

Test tubes

Forceps

Scalpel

Mortar and pestle

Fine sand

Source of heat

Wooden splints

Labels

Enzymes in Living TissuesCatalase is an enzyme present in living tissues of plants and animals.Its role in living tissues is to break down hydrogen peroxide (H2O2) produced during chemical reactions in cells.Hydrogen peroxide is a highly toxic chemical substance which should not be allowed to accumulate in the tissues. Enzyme catalase renders it harmless by breaking it down into water and oxygen.

The chemical equation below summarizes this process.

Enzyme Catalase

2H2O2......................................................... 2H2O+ O2

Procedure

1. Label the three test tubes A, B and C.2. Measure 2cm3 of hydrogen peroxide and put in each of the test tubes.3. Pick one piece of liver and drop it into test tube A. Record your observation.

Observation:Bubbles are formed

4. Grind the second piece of liver in a mortar containing a little sand.5. Place the crushed piece of liver into test tube B. Immediately introduce a glowing splint into the

mouth of the test tube.6. Record your observation.

GAMEObservation.Vigorous reaction producing a lot of bubbles. Glowing splint relights. This shows that the gas produced is oxygen. The reaction is more vigorous because crushing released more enzymes from the liver tissue.Boil the third piece of liver in a test tube for five minutes. Place it in test tube C. Record your observation.

ObservationNo reaction occurs Explanation: boiling denatured the enzyme catalase.

Animate the following processes for the respective reactions.

1. Reaction A2. Reaction B3. Reaction C


In Primary school you learnt about the structure and functions of different types of teeth in human beings. In this lesson you will learn more about how these teeth are modified to carry out their functions efficiently. You will also learn about teeth of other mammals in relation to their different modes of feeding.

ACTIVITYName four types of heterotrophic nutrition. Type your answers in the text boxes and check for the correct answer.


1. Describe the dentition of a named carnivorous, herbivorous, and omnivorous mammal.2. Relate various types of teeth in mammals to their feeding habits.3. Describe the internal structure of a mammalian tooth.4. Describe at least two dental diseases.

To insert Herbivore, Carnivore and Omnivore

Nutrition in Animals

In this section you are going to learn about feeding in animals.

A skull of a rhinocerus showing upper and lower jaws.

ACTIVITYName four types of mammalin teeth.

Type your answers in the text boxes and check for the answer.

Correct answersIncisor CaninePre-molarMolar

(Accompany each tooth with its respective illustration (photo/ diagram)

Introduction to Nutrition in Animals

Animals carry out heterotrophic nutrition. These organisms have organs and structures which are specialised for breakdown of the complex food molecules taken in into simple absorbable and usable forms.

QUIZI. Identify the modes of feeding of the mammal whose dental formulae are shown below. Type the answer in the text box.

1. i2/2 c1/1 pm2/2 m3/3= 32 2. i3/3 c1/1 pm4/4 m2/3= 423. i0/3 c0/1 pm3/3 m3/3 = 32

II. State the functions of the followinga) Carnassial teeth in a dog

b) Diastema in a sheep

III. Identify the type of mammalian tooth shown below

Name the parts labeled A, Band C

IV) The illustration below shows the internal structure of the above tooth. P

Q

R

S

1. Name the parts labeled P, Q, R and S2. Which of the labeled parts contains a higher content of calcium phosphate?

V) Suggest two ways of preventing periodontal diseases.

Answers 1a) (i) Omnivore(ii) Carnivore(iii) Herbivore

(b) (i) Slicing off pieces of teethCrushing bones

(ii) Provides space for the tongue to turn grass during chewing.

2. (a) (i) Canine (ii) A- Crown B- Neck C- Root (b) (i) P- Enamel Q- Dentine R- Pulp cavity S- Root

1. P

3 Regular cleaning of gums Regular visits to the dentist

Eating foods rich in vitamins A, C and D

Holozoic Nutrition

In holozoic nutrition solid complex food substances are ingested, digested and assimilated in the bodies of animals.The ingested food is broken down mechanically by teeth. The type, arrangement and number of teeth in a mammal is refered to as dentition.The teeth are arranged in groups to occupy specific positions in the jaw.The dentition determines the mode of feeding that is whether herbivorous, carnivorous or omnivorous.

ACTIVITYInsert an animated illustration of the skull of a carnivore showing both upper and lower jaws with teeth intact. The illustration should have the teeth labeled. As it rotates the teeth should be seen from all angles.

Observe the illustration and describe the shape of the labeled teeth.

Answers

Incisors are chisel shaped, small. They are used for cutting, gripping and stripping flesh from the bones.

Canines are long, pointed and curved .They are used for holding, piercing and killing the prey and tearing flesh.

Carnassial teeth are large, with sharp cutting edges. They are the last upper pre molar and the first lower molar modified for slicing off pieces of flesh from bones and crushing bones.

The rest of the molars and premolars are small in size because there is little chewing of food.

Count the number of each type of teeth in the upper and lower jaws. Record and check for the answer.

What is the total number of teeth in jaws of the dog?

Incisors

canines

premolars

molars

Total

Upper jaw Lower jaw Total number of teeth

incisors

canines

premolars

molars

Total

Upper jaw 6 2 8 4 20Lower jaw 6 2 8 6 22Total number of teeth

12 4 16 10 42

Dentition of a CarnivoreTeeth of a carnivore are adapted for cutting, holding, tearing, biting and piercing.

Carnivores feed on flesh. Examples of carnivores are dog, cat, lion, cheetah and leopard.

A Lion

A Leopard

Dental Formula

The number, type and position of teeth in the jaw of a mammal are described by the dental formula. The dental formula of a carnivore is related to its mode of feeding. The number of teeth recorded represents half the total teeth in the upper and lower jaws. The names of types of teeth are abbreviated as follows; incisors as i, canines as c, premolars as pm, and molar as m.

For a dog, a carnivore the dental formula is i 3/3, c 1/1 pm 4/4 m 2/3=42 The total number of teeth is obtained by multiplying teeth in each half jaw by two.

ACTIVITYGive three examples of Grazers

Browsers

Correct answerGrazers: cow, sheep, donkey, zebraBrowsers: goat, gazelle, antelopes, giraffe

Observe the illustration of the skull of a sheep.

Insert an animated skull of a herbivore (sheep) showing both lower and upper jaws with teeth intact. The following structures are to be labeled: incisor, canine, premolars, molars horny pad, and diastema. Let the illustration rotated to be seen from all angles.

Describe the shape of the labeled teeth. Type and check for the answer.

Incisor

Canine

Premolar

Molars

Answers Incisors are flat chisel shaped with sharp edges for cutting and biting vegetation. They have one root.NB: Put an illustration of a complete labeled incisor tooth.

Canines are sharp pointed and reduced in size. They also have one root. NB: Insert an illustration of a complete labeled canine of a herbivorePremolars and molars are large with broad surfaces. The surfaces have ridges and cusps for grinding vegetation.Premolars have two roots; molars have three roots. The roots are open. The enamel in the crown is open to allow for continuous growth of tooth to replace that worn out by grinding.NB: Insert an illustration of a labeled molar tooth of an herbivore.

Suggest the functions of the following structures

1. Diastema2. Horny pad

Answers

1. Diastema- provides space for the tongue to turn the grass. This facilitates effective chewing2. The horny pad serves as a surface against which vegetation is pressed and cut by the incisors in

the lower jaw.

Count the total number of each type of teeth in each jaw. Record.

Answer.

Incisors

canines

premolars

molars

Total

Upper jaw Lower jaw Total number of teeth

Answers

incisor

canines

premolars

molars

Total

Upper jaw 0 0 6 6 12Lower jaw 6 2 6 6 20Total number of teeth

6 2 12 12 32

Work out the dental formula of a sheep. Type and check for the answer

Dental formula

Answer

I0/3 c0/3 pm3/3 m3/3=32

Dentition of a Herbivore

Herbivore teeth are adapted for holding, cutting, crushing and grinding

Herbivores feed exclusively on vegetation. Their mode of feeding is referred to as herbivorous. Herbivores that feed on grass are called grazers. Those that feed on twigs, shrubs and herbs are called browsers.

ACTIVITYObserve the illustration of a human skull

Insert an illustration of a man showing both upper and lower jaws.

The teeth should be labeled. The skull should be animated and slowly rotate to be viewed from all directions.

Describe the shape of the labeled teeth. Type and check for the answer.

Incisor

Canine

Premolar

Molar

AnswersIncisors are flat, chisel shaped with sharp edges for cutting and biting. They have one root.NB: Insert an illustration of a human tooth. Rotate to be seen from all angles.

Canines are conical with sharp pointed edges for tearing. They have one root.NB: Insert a labeled illustration of a canine tooth. Animate to rotate.

Premolars are large with broad surfaces. The surfaces have cusps and ridges for grinding food. They have two roots.NB: Insert a labeled illustration of a human premolar. Rotate.

Molars are large with broad surfaces. They have more cusps and ridges for grinding food. Molars have three roots.

NB: Insert a labeled illustration of a human molar tooth. Rotate.Count the total number of each type of teeth in each jaw. Record and check the answer.

incisor

canines

premolars

molars

Total

Upper jaw

Lower jaw Total number of teeth

incisor

canines

premolars

molars

Total

Upper jaw

4 2 4 6 16

Lower jaw 4 2 4 6 16Total number of teeth

8 4 8 12 32

Work out the dental formula of a human being. Type and check for the answer.

Answer

I2/2 c1/1 pm2/2 m3/3 =32

Dentition of an Omnivore

Omnivores feed on both flesh and vegetable matter. Their teeth are adapted for this type of food. Examples of omnivores are human being, gorilla and pig.

Human Jaw

Gorrilla Jaw

ACTIVITY

Count the total number of each type of teeth in each jaw. Record and check the answer.

incisor

canines

premolars

molars

Total

Upper jaw

Lower jaw Total number of teeth

incisor

canines

premolars

molars

Total

Upper jaw

4 2 4 6 16

Lower jaw 4 2 4 6 16Total number of teeth

8 4 8 12 32

Work out the dental formula of a human being. Type and check for the answer.

Correct answer i2/2 c1/1 pm2/2 m3/3 =32

Dental Formula of an omnivore

Dental formula of an omnivore is related to mode of feeding as well as the species under consideration.

Omnivores feed on both flesh and vegetation. The mode of feeding is called omnivorous. These have all their incisors, canines, premolars and molars well developed.

Structure of Teeth

These animations show the external structure of the four types of teeth in man, that is, incisors, canines, premolars and molars.

This illustration shows the Internal Structure of a Molar Tooth

Enamel: Outermost non living material covering the crown. It is made up of calcium and calcium phosphate. It is hard, and protects the inner delicate parts of the tooth and to provide a surface suitable for cutting and chewing food.

Dentine: It is found under the enamel. It is a living part, containing cytoplasmic strands. It is hard and bone-like but softer than the enamel. It gives rise to the enamel.

Pulp cavity: Contains blood vessels and nerve endings. The blood vessels provide nutrients to the living tissues and remove waste products. The nerves detect heat and pain sensations or stimuli.

Cement: It is spongy material made of calcium. It fixes the tooth to the socket in the jaw bone.

ACTIVITYQ. Suggest four ways of preventing dental diseases

Answers

Regular cleaning and brushing of teeth Avoid too much sugary foods Eating hard foods such as raw carrots, cassava, yams, sugarcane Eating foods rich in calcium phosphates and vitamins A,C, and D Using teeth for their proper purpose. Do not use to open bottles Regular visits to the dentist.

Dental Diseases The two common dental disorders in humans are dental carries and periodontal disease:

Dental carries

This is an infection of the tooth itself. It results into tooth decay seen as cavities in the tooth. The photos show teeth with this kind of problem.

Periodontal Diseases: This is inflamation of the gums due to bacterial infection.The gums become soft and swollen. e.g.Gingivitis.

Healthy Gums

Infected gums

Moderate Gingivitis

Advanced Gingivitis

Causes of Dental Carries

Dental carries are cavities in teeth and are brought about by destruction of the hard tissue of the tooth. They may be due to eating too many sugary foods, not eating relatively hard foods and not cleaning teeth well

Too many sugary foods.

Accumulation of sugary food on the tooth surface

Progression of Dental Carries in a molar tooth due to accumulation of sugary foods.

Not eating hard foods such as sugarcane.

Lack of calcium in the diet.

Insufficient vitamin D.

Poor cleaning of teeth.

Treatment and Control of Dental Carries

Dental carries can be controlled by:

Proper cleaning (brushing), especially before going to bed.

Filling in cavities that have developed.

Removing plaque from the enamel.

Root canal treatment.

Visiting the dentist at least once a year.

Avoiding too many sugary foods

Feeding on a balanced diet rich in all types of nutrients.

Eggs

Milk

Bananas

Periodontal DiseasesPeriodontal diseases attack the gums and walls of the mouth cavity. The gums become soft and flabby,

such that they are unable to support the teeth. The disease is characterized by the reddening of gums and, in severe cases, the presence of pus. The presence of pus in the gums is a condition called pyorrhea while bleeding of the gum is a condition called gingivitis.

Infected gums

Causes of Periodontal Diseases

Periodontal diseases may be caused by :

Lack of vitamins A and C in the diet Not cleaning gums properly

Treatment and Control of Periodontal Diseases.

Eating a balanced diet

Proper cleaning of teeth.

Brushing Teeth

Visiting a dentist at least once a year.


In primary school you learnt about the parts of the human digestive system (alimentary canal).

Human Digestive System

ACTIVITYComplete the table below by filling in the blank spaces

Part of the alimentary canal

Juice secreted

Gland where made

Enzyme in juice

Substance acted upon by juice

Products

Mouth saliva a b Cooked starch cStomach d Gastric gland e

fProteinscaseinogens

g

Duodenum h Pancreases Typsinlipase

Starchj k

iPeptidesm

bile n o lipids Tiny fat droplets

Ileum p Wall of the ileum

Maltaseq r

sSucroselactose

tGlucose + uGlucose +v

Peptidasew

xEmulsified fats

yz

2. The figure below is a part of the alimentary canal

(a) (i) Which part of the alimentary canal is represented by the portion above?(ii) Give one reason for your answer in (a) (i) above (b) State two functions of the part of alimentary canal represented above

3. Explain why enzymes pepsin and typsin are secreted as inactive pepsinogen and typsinogen respectively.4. Name the blood vessel that transport digested food from the ileum to the liver.5. What happens to absorbed glucose in the body?

Answers1. a- salivary glands b- salivary amylasec- Maltose d- gastric juicee- Pepsin f- renning- Peptides h- pancreatic juicei- Protein k- lipidsl-maltose m- fatty acids and glyceroln- Liver o- bile saltsp- Intestinal juice q- sucraser- Lactase s- maltoset- Glucose u fructosev- Galactose w lactasex- Peptides y- amino acidsz- Fatty acids and glycerol.

2 (a) (i) ileum ii) Presence of villi(b) Digestion Absorption3. To prevent them from digesting the wall of the alimentary canal4. Hepatic portal vein5. Used to release energy Excess is converted into glycogen and stores in the liver.


Relate the structures of the human alimentary canal to their functions. Describe the process of digestion. Describe the process of absorption.

Digestive System and Digestion in Humans

ACTIVITY

Label the parts of the human digestive system in the human digestive system in the illustration below by dragging and dropping at the respective labels.

Insert an illustration of human digestive system

Pancreas AnusSmall intestine MouthOesophagus LiverRectum Large intestineStomach Salivary glands

Gall bladder ACTIVITYObserve the illustration below and describe the movement of food along the esophagus. Type and check for the answer

Observation

Food moves in a wave like motion. This is due to rhythmic contraction and relaxation of muscles of the oesophagus. This movement is called peristalsis.

Digestion

Breakdown of large complex molecules of food materials into simple usable forms is known as digestion. Physical breakdown is done by teeth while enzymes chemically breakdown the food. You have learnt about the functions of enzymes and teeth respectively. You learned that enzymes speed up the rate of chemical reactions in the body, for example, break down of large complex molecules into simple, usable molecules. Much of the food a human being takes in (ingests) is made up of large complex molecules. It is first broken down physically by the teeth and then chemically by enzymes into simple and soluble molecules before it can be absorbed. Along the alimentary canal, enzymes chemically digest carbohydrates, proteins and lipids.

ACTIVITY

Mammalin Ileum

From the illustration given above, suggest how the ileum is adapted for absorption of food.Type and check for the answer

TEXT BOX

Correct answers

Long, to provide large surface area for absorption. Coiled, to slow down movement of food allowing more time for digestion to be complete and

absorption to take place. Inner surface has numerous villi and microvillus which increase surface area for absorption . Thin epithelium (thin layer of cells), to allow rapid diffusion of digested food. Dense network of blood capillaries, to facilitate absorption and transport of food. Presence of lacteals in the villi for absorption of fatty acids and glycerol.

Digestion in the Mouth

Mastication is carried out in the mouth whereby food is physically broken in to small pieces using teeth.These small pieces can then be chemically digested by the help of enzymes in the mouth and along the digestive canal.

Salivary glands secrete saliva which contains the following:

Enzyme salivary amylase (ptyalin). This enzyme breaks down cooked starch into maltose in a slightly alkaline pH.

Mucus which lubricates the food. Water which is a medium for the enzyme to act in and to soften the food

The tongue rolls the food into a bolus which can easily be swallowed.

Swallowing

During swallowing the epiglottis closes over the glottis thereby covering the air passage. The tongue then forces the bolus into the oesophagus.

Peristalsis during swallowing of food

Digestion in the Stomach

The bolus of food enters the stomach through a muscular valve called cardiac sphincter. The arrival of food into the stomach stimulates the stomach wall to secrete the hormone gastrin.Gastrin stimulates gastric glands to secrete gastric juice. Gastric juice contains:

Enzyme pepsin which is produced in an inactive form pepsinogen. Pepsin breaks down proteins into peptides.

Enzyme rennin which converts soluble milk caseinogen into insoluble casein. This process is called coagulation. Casein is acted upon by pepsin to produce peptides

Hydrochloric acid which (1)activates the inactive enzyme pepsinogen to active enzyme pepsin, (2)creates a suitable (acidic) pH for the action of the enzyme pepsin, (3)kills bacteria present in the food and (4)emulsifies fats into droplets.

Mucus which forms a protective barrier to the stomach wall, against corrosion by hydrochloric acid and

digestion by pepsin.

Formation of Chyme in the Stomach

Rhythmical contractions of the stomach churn the food into a semi- fluid state called chyme.

Churning of Food in the Stomach

Digestion in the Duodenum

Chyme enters the duodenum and stimulates secretion of the hormone cholecystokinnin. This hormone in turn stimulates the pancreas to secret enzymes lipase, amylase and trypsin contained in pancreatic juice. The hormone also stimulates production of bile.

The duodenum is the first part of the small intestine. Chyme is let into the duodenum in small amounts through the pyloric sphincter.

The figure shows chyme entering the duodenum

Arrival of food in the duodenum stimulates the secretion of the hormones secretin and cholecystokynin (CCK) from the wall of the duodenum. Secretin stimulates pancreas to release pancreatic juice into the duodenum.Cholecystokynin stimulates the gall bladder to release bile.

Pancreatic juice contains three enzymes:

Pancreatic lipase which breaks down lipids into fatty acids and glycerol. Pancreatic amylase which breaks down remaining undigested starch to maltose. Typsin which breaks down proteins into peptides. This enzyme is secreted in an inactive

form,trypsinogen. Enzyme enterokinase stimulates production of trypsinogen.

Pancreatic juice also contains Sodium hydrogen carbonate which (i) neutralizes the acidic chyme and (ii) provides an alkaline medium for pancreatic enzymes.

Bile contains bile salts which include sodium glycocholate and sodium trycocholate. The salts break down fats into tiny fat droplets to increase surface area for digestion. This process is called emulsification.

Bile also provides an alkaline medium for the enzymes and neutralizes the acidic chyme.

Digestion in the Ileum

Entry of food in the ileum stimulates production of succus entericus, a juice which contains enzymes that complete digestion. The enzymes include Maltase which breaks down maltose to glucose. Sucrase which breaks down sucrose into glucose and fructose. Peptidase breaks down lipids into fatty acids and

glycerol. Lactase which breaks down lactose to glucose and galactose. The completion of digestion results into a watery emulsion (mixture) called chyle from which the products of digestion are absorbed.

Summary of Digestion in the Small Intestine

Absorption of Digested Food

Absorption is the process by which the soluble products of digestion pass through the wall of the ileum into the blood stream. This occurs mainly in the ileum.

Coiled Human Ileum (Small Intestine)

Section of Ileum Showing Villi

Microscopic Section of Ileum Showing Villi

Epithelial Cell Showing Microvilli

Absorption and Transport of Digested Food at a villus

The absorbed products of digestion are carried to the liver by hepatic portal vein.

Assimilation

Assimilation is the process by which the body uses up the absorbed products of digestion. From the liver the products of digestion are transported in the blood stream to the rest of the body. The different food substances are assimilated as follows: Glucose is oxidized to release energy. Excess glucose is converted into glycogen and stored in the liver.Fatty acids and glycerol are oxidized to release energy. Excess is converted into fats and stored under the skin. Amino acids are used in the synthesis of proteins for growth and repair of worn-out tissues. Excess amino acids are converted to urea and excreted in urine. These processes are illustrated next

Assimilation of Glucose

Assimilation of amino acids: Most amino acids are used to make proteins for the body in a process called protein synthesis

Assimilation of Lipids

Egestion

Undigested materials are the materials that missed to be digested because they were not in the alimentay canal long enough. Indigestible food materials are those materials that can not be digested. Both the undigested and the indigestible materials are removed from the alimentary canal through the anus at intervals as faeces.

Egestion is the terminology that refers to this removal of undigested and indigestible food materials from the body through the anus in form of feaces.As the undigested and indigestible materials pass through the colon, water is exclusively absorbed. This leaves faeces to come out as a semi-solid waste material.

Egestion of undigested and indigestible materials as feaces

The figure bellow illustrastes the summary of digestion. It also marks the end of our Form One lessons in Biology. Move the cursor along the alimentary canal to activate the processes in key sections.

The End

This is the end of our Form One Lessons.

Test yourself using the exercises and quizzes provided at the start of each of the topics in these lessons to gauge your progress.

Digestion in the Ileum

Entry of food in the ileum stimulates production of succus entericus, a juice which Maltase which breaks down maltose to glucose. Sucrase which breaks down sucrose into glucose and fructose. Peptidase breaks down lipids into fatty acids and glycerol. Lactase which breaks down lactose to glucose and galactose. The completion of digestion results into a watery emulsion (mixture) called chyle from which the products of digestion are absorbed.

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