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BiologyPreliminary CourseStage 6

Patterns in nature

Part 7: Transporting materials in animals

Incorporating October 2002

AMENDMENTS

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Part 7: Transporting materials in animals 1

Contents

Introduction................................................................................ 2

Transport systems in animals .................................................... 3

Respiratory system ..............................................................................3

Circulatory system................................................................................3

Excretory system..................................................................................4

Circulatory systems ................................................................... 5

Gas exchange in animals .......................................................... 8

Insects ..................................................................................................8

Fish .....................................................................................................10

Frogs...................................................................................................11

Mammals ............................................................................................12

Investigative technology .......................................................... 16

Exercises–Part 7 ..................................................................... 19

2 Patterns in nature

Introduction

In plants and animals transport systems and gaseous exchange move

chemicals through the internal environment as well as the external

environment.

In the previous parts you have identified the nutrients required by living

things and how they are obtained form the surroundings. In this part you

will be looking at how these nutrients are transported around animals.

In this part you will be given opportunities to learn to:

• compare the roles of the respiratory, circulatory and excretory

systems

• identify and compare the gas exchange surfaces in an insect, a frog, a

fish and a mammal

• explain the relationship between the requirements of cells and

transport system in multicellular organisms

• compare open and closed circulatory systems using one vertebrate

and one invertebrate as examples

In this part you will be given opportunities to:

• use available evidence to discuss, using examples, the role of

technologies, such as the use of radioisotopes in tracing the path of

elements through living plants and animals.

Extract from Biology Stage 6 Syllabus © Board of Studies NSW, originally

issued 1999. The most up-to-date version can be found on the Board's website

at http://www.boardofstudies.nsw.edu.au/syllabus_hsc/syllabus2000_lista.html

This version November 2002.

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Transport systems inanimals

In animals there are three systems that move materials around the body

and between the body and the surrounding environment.

These systems are:

• respiratory system

• circulatory system

• excretory system.

Respiratory system

The respiratory system is responsible for the movement of gases

throughout the body. Oxygen is required for every cell in the body and

carbon dioxide must be removed from every cell in the body.

The respiratory system performs this function. Organs that are part of

the respiratory system of animals are lungs, gills and spiracles in insects.

Circulatory system

The circulatory system transports food, oxygen and wastes throughout

the body. Every cell has requirements for nutrients and must get rid of

poisonous waste materials. This is the role of the circulatory system.

Organs of circulatory systems are heart, veins, arteries, capillaries and

the haemocoel in insects. Circulatory systems may be open or closed.


Excretory system

All animals need to excrete wastes produced from metabolic processes in

their cells. A build–up of wastes can produce unwanted effects and

many substances such as urea can become toxic in excess qualities.

Wastes substances that have to be remove include water, carbon dioxide

and nitrogenous compounds. Organs of excretion include kidneys, lungs,

skin and malpighian tubules in insects.

Comparison of the systems

All three systems have different tasks but they share common features

and common roles. The circulatory system has a role in the other two

systems because the blood vessels move materials to the organs of

respiration and excretion. Organs of the respiratory system such as the

lungs have a function in excretion of carbon dioxide. All three systems

work together to transport nutrients and waste products from where they

enter the body to where they leave the body.

The table below summarises this information.

Respiratory system Circulatory system Excretory system

Organs Lungs, gills, skin,spiracles

Heart, blood vessels,lymph, haemocoel

Kidneys, lungs, skin,malpighian tubules

Function Movement of gasesthrough the body

Transport nutrients andwaste products around thebody

Rid the body ofwaste materials,water balance

Complete Exercise 7.1.

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Circulatory systems

All multicellular plants and animals require a transport mechanism to

move nutrients, gases and wastes to and from cells. These materials need

to be moved around an organism’s body efficiently. This to ensure that

all cells obtain the appropriate materials to maintain function and any

products and wastes are removed.

Both plants and animals have methods of transporting materials within

the body. However, the transport of materials occurs in different ways.

In this section you will focus on transport in animals.

The circulatory system transports oxygen, food material and wastes to

and from cells. The movement of the blood through an organism

depends on the action of a heart.

All vertebrates and some invertebrates such as earthworms have a closed

circulatory system. This means that blood is transported around an

organism within muscular tubes or blood vessels.

The diagram following shows the movement of blood through the human

circulatory system.

Invertebrates such as arthropods have an open circulatory system.

A pool of blood is circulated by the action of a heart, there are no

specialised vessels for transporting blood.

An insect’s blood is in direct contact with its body cells–blood is not

contained in blood vessels as such. The internal space of an insect’s body

can be considered as a single blood vessel called the haemocoel.

This name comes from Greek words: haima (blood) and koilia (hollow).

An insect’s circulation system is in fact not entirely ‘open’ as they have

pumping vessels to promote the flow of blood.


capillariesin kidneys

capillariesin lungs

capillariesin liver

capillaries inlegs and

abdominal organs

capillaries instomach and

small intestine

anteriorvena cava

pulmonaryartery

capillariesin arms and

head

capillariesin lungs

mesentericartery

rightatrium

rightventricle

posteriorvena cava

pulmonaryvein

leftatrium

leftventriclehepatic

portal vein

renalvein

hepaticartery

renalartery

oxygenated blood de-oxygenated blood

mesentericvein

Human circulatory system – a closed system.

brain

gut

haemocoel

accesory pump

pumping vessel

Insect circulatory system – partially open system.

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A closed circulatory system ensures that there is one pathway ensuring

tissues are supplied with blood. It relies on a central heart to pump the

blood around within the specialised blood vessels. These require large

amounts of energy. All vertebrates have a closed circulatory system.

Open circulatory systems do not require the large amounts of energy

required by closed circulatory systems. They suit smaller animals that do

not make rapid movements.



Gas exchange in animals

All animal cells respire. Animal cells respire aerobically (most of the

time). They use oxygen gas in the process and release carbon dioxide

gas as a waste product. Animal cells do not photosynthesise.

In this section you will investigate and compare gas exchange surfaces of

an insect, a fish, a frog and a mammal. The gas exchange tissues and

organs of major groups of multicellular animals are often different.

In this section you will examine those differences.

Insects

Insects do not have lungs or gills. Insects exchange gases with the

atmosphere using trachea, tracheoles and spiracles.

longitudinaltrachea

spiracle

tracheoles

Structures used in gas exchange in an insect.

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Insects carry out gas exchange through a series of internal tubes (trachea)

that connect to the outside through holes (spiracles) located at various

points on the insect body.

The trachea branch into smaller and smaller tubes (tracheoles).

Tracheoles are very tiny (about one micron in diameter). The branching

into many tiny tubes has two advantages for the insect.

• Because the tracheoles are extensively branched throughout the

insect, most cells are close to specialist gas exchange surfaces.

• The branching and the small size of the tracheoles greatly increases

the surface area to volume ratio of the gas exchange surfaces.

Fluid collects in the ends of the tracheoles and it is into this fluid that

gases dissolve before diffusing into the surrounding cells.

The tracheoles are close to body cells. When waste gases eg. carbon

dioxide concentrations are higher in the cell than the neighbouring

trachea, then the waste gases diffuse out of the cell. When oxygen levels

are higher in the trachea than the surrounding cells oxygen will diffuse

into the cells.

The spiracles connect the trachea to the atmosphere surrounding the

insect. When the insect uses its muscles the trachea are compressed

and this causes gases to be pushed out of the spiracles. When the

muscles relax the trachea are not compressed and gases flow back into

the trachea.

Spiracles are able to close to help reduce water loss. Because the internal

parts of the body are very humid it is possible for water be removed as a

vapour from the body.

Spiracles also have fine hair–like structures to prevent dust entering the

system. If dust were to enter, the tracheoles could become blocked and

this would reduce the efficiency of the gas exchange surfaces.


Fish

Most fish use gills for gas exchange. Gills are external structures–they

hang outside the main body cavity and often have a protective cover over

them. Gills have a large surface area because they are thin and

highly folded.

Gas exchange in fish

Water enters a fish’s mouth and passes over the gills. When most fish

are stationary they gulp water to maintain the flow over the gills.

This also explains why so many fish (sharks included) swim with their

mouth open–this allows the water to pass into the mouth and over the

gills without the need to gulp water.

Gases are exchanged between the surrounding water and the fish on the

gill surface. The gases enter the circulatory system where they are

transported to cells throughout the body. The main blood vessels

entering the gills branch into tiny tubes called capillaries.

The capillaries are very close to the gill surface. It is the colour of the

blood in the capillaries that makes gills appear red. Capillaries being tiny

and numerous make the surface area to volume ratio for diffusion of

gases very high in the gills.

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Frogs

Frogs have two methods of gas exchange: gas exchange via the lungs and

gas exchange via the skin. The diagram below shows the structures

involved.

lungs

diffusion in moist skin

Frogs exchange gases through their lungs and moist skin.

Gas exchange via the lungs

Lungs are internal organs involved in gas exchange. The gas exchange

surfaces of terrestrial organisms are usually internal to prevent

desiccation (drying out). You will have noticed that the gas exchange

surfaces of insects (also terrestrial) are internal too.

Frogs ventilate their lungs by positive pressure breathing. This means

that they force air into the lungs. This method of breathing is very

different to the negative pressure breathing seen in mammals. You will

look at negative pressure breathing later.

Unlike human nostrils, which stay open all the time, frogs are able to

open and close their nares (nostrils). To breathe, a frog

• closes its mouth and opens its nares

• lowers the floor of the mouth causing air to be ‘sucked’ into the

mouth cavity

• closes the nares (nostrils)

• raises the floor of the mouth.

This forces the air in the mouth into the lungs.


Lung structure of a frog

The internal structure of a frog lung is not too dissimilar to a human lung.

Air enters the lungs and then moves through a series of branching tubes.

The tubes become smaller and smaller as they branch (this is becoming a

familiar theme for gas exchange). The finest tubes are in close

association with capillaries (small blood vessels). Gases diffuse into and

out of the blood at these sites.

Like the fish, the circulatory system delivers gases to the cells.

The circulatory system also receives the waste gases from cells and

delivers them to the lungs. You will take a much closer look at the

structure of lungs in the next section.

Gas exchange via the skin

The skin of a frog is thin and kept moist by the habitats in which the frog

lives. The skin is permeable to water (unlike human skin).

Frogs dehydrate rapidly if they are not kept in a moist environment.

This is why you find frogs in moist locations.

Gases from the atmosphere dissolve into the moisture on the skin.

From there the gases can diffuse into the capillaries beneath the skin.

The skin does not exchange sufficient gases for all of a frog’s needs.

However, the gas exchange is important and allows the frog to remain

submerged for longer than if it had to depend on lungs alone.

While submerged, gaseous exchange occurs on the frog’s skin.

Mammals

Mammalian lungs are internal. This helps to reduce the loss of water

and heat through these structures that have a high surface area to

volume ratio.

To get air into the lungs the mammal lowers the air pressure in the lungs.

When the air pressure in the lungs is lower than the surrounding

atmosphere, air enters via the nose.

To remove air from the lungs, mammals increase the pressure of the air

in the lungs. When air pressure in the lungs is higher than the

surrounding atmosphere air moves out of the lungs.

The structure of the human respiratory system is shown on the diagram

on the following page.

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epiglottis

to the stomach

rib

right lungshowinglobes

diaphragm

air

nosetrachea wallmagnified

cilia

trachea

bronchusbronchiole

left lungdissected toshowinternal

cluster ofalveoli

from pulmonaryartery to pulmonary

vein

nasal cavity

capillaries

Structures involved in the exchange of gases in humans.

Air enters the body through the nostrils. The nasal cavity warms the air,

filters it and removes dust. The air then moves into the throat region or

pharynx (pronounced farrinks). It enters the largest air tube–the trachea

(pronounced track–ee–ah) through the opening called the glottis.

The epiglottis is a flap of tissue that closes over the glottis and stops food

going down the wrong way when we swallow.

The trachea branches into two bronchi (pronounced bron–key).

Each bronchus (singular) branches into smaller air passages called

bronchioles (bron–key–oles) and these end in very thin–walled alveoli

(pronounced al–vee–oh–lie), singular alveolus. Blood capillaries are

wrapped closely around the alveoli.

It has been estimated that the total surface area of the alveoli of an adult

male is about one third the area of a tennis court. A large surface area

obviously allows for a greater quantity of gases to be exchanged.

The thinness of the walls of the alveoli allows for rapid diffusion of

oxygen into the blood and carbon dioxide out of the blood. The moisture

in the alveoli walls allows gases to dissolve.


blood from body(low in oxygen, high in carbon dioxide)

blood capillary

blood cell

oxygen

carbon dioxide

wall of alveolus

air inhaledair exhaled

blood to rest of body(high in oxygen,low in carbon dioxide)

Movement of material in an alveolus.

Composition of inhaled and exhaled air is shown in the table below.

Gases Percentage in inhaled air(%)

Percentage in exhaled air(%)

oxygen 21 16

carbon dioxide 0.04 4

nitrogen about 80 about 80

water vapour varies according to thehumidity of the air

more than in inhaled air

Air passages

Rings of cartilage keep the trachea and bronchi open and prevent them

closing when the air pressure inside the body falls. The lining cells of

the air passages have numerous cilia (sill–ee–ah). These are minute

hair–like projections that sweep to and fro.

Mucus is secreted by special gland cells, also present in the lining or

epithelial (ep–e–theel–e–al) cells. Dust particles and bacteria in the air

are trapped by the mucus film. The movements of the cilia sweep them

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away in the mucus to the larynx and the mucus is swallowed or

coughed up.

The nose hairs and mucus also trap dust and foreign particles.

Around the lungs is a membrane, the pleural (ploo–ral) membrane, which

covers the outside of the lungs and the inside of the chest cavity.

It contains a fluid that lubricates the surface so that there is no friction

between the tissues during breathing movements.

The mechanism of breathing

In mammals, breathing refers to the movements of the chest that result in

air entering and leaving the lungs.

The movement of air in and out of our chest is bought about by changes

in the pressure of the air in the chest cavity. This pressure varies because

the volume of the chest cavity varies. The chest cavity is airtight and

enclosed by ribs with intercostal (inter–cos–tal) muscle between them.

At the base of the chest cavity is the diaphragm (die–ah–fram).

The diaphragm is the muscular sheet separating the chest (also called

thorax) and abdomen.

At rest, the diaphragm is curved upwards. The intercostal muscles relax

at the same time and the ribs move downwards and inwards.

These collapsing movements reduce the size of the chest cavity, increase

the pressure of the air in the lungs and thus force it out.

During inhalation, the diaphragm contracts and flattens, being more taunt

or tight in this state. At the same time, the intercostal muscles contract

and move the rib cage up and outwards. This increases the volume of the

chest cavity and reduces the pressure of the air in it. Air thus moves into

the lungs. You can check these movements by placing your fingers over

your rib cage as you inhale and exhale.



Investigative technology

Much of what is known about the structure and function of living

things has been directly associated with the improvements in

technology available.

New technology is increasing the range of investigative methods in

research laboratories, industry, environmental management and in the

medical profession. The use of radioisotopes have improved productivity

and gained information that cannot be obtained in any other way.

Radioisotopes produce radioactive emissions that can be easily detected.

This property makes radioisotopes very useful as tracers.

Radioactive materials can be tracked through a process, system or

organism. Examples of use include mapping pathways of nutrients and

toxins through ecosystems, absorption of nutrients by plants and tracing

metabolic pathways. Increasingly medical diagnosis is making use of

tracers for organ and tissue function.

Many chemical elements have isotopes. (Isotopes have the same number

of protons but a different number of neutrons in the nucleus of an atom.)

Some isotopes are unstable and emit alpha or beta particles and

sometimes gamma radiation.

Tracers can be used to follow movement of substances in large amounts

or at molecular or even atomic levels. The observations are made by

measuring the radioactivity or by measuring the relative abundance of the

stable isotopes. The instruments used for detecting the tracers pathway

include electroscopes, scintillation counters, the Geiger–Müller counter

and the mass spectrometer.

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Radioactive tracers

Radiation is used in nuclear medicine to diagnose the functioning of

organs such as the liver and kidneys. Radioactive tracers are used which

emit gamma rays for very short periods of time. Radioactive materials

are introduced into the body orally, by injected or they are inhaled.

An image of the organ showing the location of the radioisotope is used in

diagnosis. An unusual pattern indicates a malfunction in the organ.

Bone and other tissue can be seen much more clearly using these imaging

techniques than by x–rays.

Blood flow to the brain, liver and kidney function and bone growth can

be diagnosed using radioisotopes as tracers. The amount of radioisotope

given to patient is a very small dose, only enough to obtain an image for

diagnosis.

Technetium–99 is a very common isotope used in medicine.

It has a half–life of six hours. Technetium–99 emits low energy gamma

rays so the patient receives only a very low radiation dose.

Geiger counters

A Geiger counter is a machine that measures radioactivity.

In the experiment on the following page radioactive carbon was taken in

by the leaves through the process of photosynthesis. The Geiger counter

was used to measure the amount of radioactive carbon in the leaves and

in the fruit. The next day the readings showed that the radioactive carbon

had moved from the leaf to the fruit.


Geiger counter

Geiger counter

sugar with radioactive carbon on scraped leaf

Day 1

tomato fruit

HIGH

LOW

Geiger counter

Geiger counter

sugar with radioactive carbon on scraped leafDay 2

tomato fruit

LOW

HIGH

Gather information from secondary sources on the use of radioisotopes in

tracing the path of elements through living plants and animals.

You will need to carry out a search of secondary information sources such as

contacting research institutions such as ANSTO, CSIRO or the Internet.

Conventional sources such as libraries will have many references you can

use and may be a good place to start.

Process the information by answering the questions in Exercise 7.4.

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Exercises - Part 7

Exercises 7.1 to 7.4 Name: _________________________________

Exercise 7.1: Transport systems in animals

Compare the roles of the excretory, respiratory and circulatory systems in

the body. systems

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Exercise 7.2: Circulatory systemsa) What is the role of the circulatory system in humans?

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b) What is the difference between open and closed circulatory systems?

Give examples.

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c) Which system is more efficient – open or closed circulatory system?

Give reasons.

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Exercise 7.3: Comparison of gas exchange

Identify and compare the gas exchange surfaces in an insect, a frog a fish

and a mammal by filling in the table below.

Organism Name of gasexchange structures

Surface Area/Volumeratio

Gas exchangestructuresinternal/external

insect high

skin low externalfrog

lungs high

fish

mammal internal

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Exercise 7.4: Radioactive tracers

Discuss the role of radioisotopes as tracers in medicine. What are the

issues? Provide points for and against the use of radioactive materials in

medicine.

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