Ahmad Bio Notes

8/19/2019 Ahmad Bio Notes

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9.2 Maintaining a Balance

Contextual Outline

Multicellular organisms have specialised organ systems that are adapted for the uptake and transport

of essential nutrients from the environment, the utilisation or production of energy and the removalof waste products arising from cellular activities.

The basis of healthy body-functioning in all organisms is the health of their cells. The physical and

chemical factors of the environment surrounding these cells must remain within narrow limits forcells to survive. These narrow limits need to be maintained and any deviation from these limits must

be quickly corrected. A breakdown in the maintenance of this balance causes problems for theorganism.

The nervous and endocrine systems in animals and the hormone system in plants bring about the

coordinated functioning of these organ systems. They are able to monitor and provide the feedback

necessary to maintain a constant internal environment. Enzyme action is a prime example of the need

for this balance. Enzymes control all of the chemical reactions that constitute the body’s metabolism.

As enzymes normally function only within a narrow temperature range, even small rises in body

temperature can result in failure of many of the reactions of metabolism that are essential to life.

This module increases students understanding of the applications and uses of biology, implications

for society and the environment and current issues, research and developments in biology.


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9.2 – Maintaining a Balance:

1. Most organisms are active within a limited temperature range:

Identify the role of enzymes in metabolism, describe their chemical

composition and use a simple model to describe their specificity in

substrates:

– Metabolism is the sum total of all chemical reactions occurring within a living organism. The only reason you

grow, heal etc is because of this. It is divided into two parts:

Anabolic: are reactions that involve the building up of larger organic compounds from simple molecules, eg

large polysaccharide molecule such as starch being made from monosaccharide units such as glucose (product

of photosynthesis).

Catabolic: are reactions that involve the breaking down of complex organic compounds to simple ones, eg

digestion of food, large food molecules such as proteins are broken down into small amino acids, which can be

used for other uses.

– All the above, ie every metabolic reaction in your body is carried out by enzymes, they are organic protein

catalysts (chemical substance that speed reactions without taking part in it).

– Chemical composition of enzymes:

Recall: proteins are made of polypeptides which in turn are made of amino acids.

All enzymes are made of protein as well as other elements that are known as co-enzymes/co-factors which help

specific enzymes function, such as carbon, hydrogen, oxygen and nitrogen.

Enzymes are globular proteins, meaning the polypeptide chains (ie amino acids) are folded into a 3-dimensional

globular shape.

This shape is what effective gives each enzyme its function, and parts of it are called active sites. The molecule

on which an enzyme acts on is called the substrate.

– Specificity of enzymes:

Enzymes are highly specific in their action; this means that each enzyme acts on one substrate only, this is

because the shape of the active site of the enzyme matches the shape of the substrate material.

The products are the substances that the substrate(s) become. One substrate can be split, or two substrates can be

joined.

– Models to explain specificity:

There are two current hypothesis:

The Lock and Key Model: suggests that the substrate fits exactly into the active site of the enzyme like a key

fits into a lock. It assumes that the enzyme had a rigid and unchanging shape.


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The Induced Fit Model: states that the binding of the substrate to the enzyme ‘induces’ a temporary change in

shape of the enzyme. The new shape of the enzyme better accommodates the shape of the substrate and a

reaction occurs.

Identify the pH as a way of describing the acidity of a substance:

– pH is a way of describing the acidity or the alkalinity of a substance, its a measure of the concentration of

hydrogen ions per litre of solution, so the more acidic a substance is, the more hydrogen ions, the LOWER the pH.

– The pH scale is from 0 to 14: a pH of 7 is neutral (pure water); above 7 is alkaline and below 7 is acidic.


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Identify data sources, plan, choose equipment or resources and perform a

first-hand investigation to test the effect of increased temperature, change

in pH and change in substrate concentrations on the activity of enzymes:

– Aim: To test the variety of factors (such as temperature, pH (acidity/alkalinity), substrate concentrations) on the

effect on enzyme activity.

– Equipment:

Potato pieces/living tissue (ie cow liver pieces) (both contain the enzyme catalyse)

Catalyse is a enzyme that breaks poisonous hydrogen peroxide into harmless water and oxygen gas

20 test-tubes

Hydrogen peroxide (H2O2)

Acid: H2SO4, Base: NaOH

Source of heat (ie hot plate)

pH probe

Thermometer

– Safety:

Hydrogen peroxide is an extremely poisonous substance, it must not be ingested, and teacher supervision is

needed.

Hot plate can reach temperatures well over 200-400 degrees, it must be put in a rigid and safe position.

Gloves and glasses must be worn, in case of accidental test-tube damage.

– Method:

3 separate tests were carried out in test tubes with potatoes placed in them; pH, temperature, substrate

concentration.

Evidence for enzyme activity came from the sound of ' fizzing effect ', the louder the more activity is presumed. This is further determined by the ' formation of bubbles', where bubbles that are in greater in height show greater

activity.

– Result:

– pH:

Each enzymes work best at its optimum pH, which is usually within a very narrow range, for example enzymes

in the stomach can work at 1-2 pH , whilst enzymes as catalase work at 7 pH.

Extremes of acidity or alkalinity can affect the bonds holding the 3D globular shape of the enzyme. Thus losing

activity and distorted.


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– Temperature:

As temperature increases, MOST enzyme activity increases, up to the optimum temperature (a particular

temperature, approx. 40°C, an enzyme is most active). This is because the enzyme and substrate molecules

move faster as (more kinetic energy) and therefore more collisions between enzyme and substrate occur.

At very high temperatures, the activity of the enzyme falls rapidly, because the heat energy breaks the bonds

that cause the protein to fold, so destroying the active site in a irreversible process, called denaturation.


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– Substrate concentration:

An increase in substrate concentration will increase the reaction until all enzyme active sites are occupied this is

known as saturation point , thus reaction proceeds at maximum rate (VMax or Maximum velocity). A further

increase in substrate, cannot increase the rate because the are no active sites available.

Explain why the maintenance of a constant internal environment is important

for optimal metabolic efficiency:

– Metabolism is severally affected by enzymes, and hence the functioning of an organism. Enzymes work best

within a limited range of environmental conditions, but their efficiency is affected greatly by certain factors which

include temperature, pH and substrate concentration.


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– Hence a constant and stable internal environment is needed so that enzymes will always be working at an optimum

rate, and thus metabolism will be a optimum efficiency, if these factors do not remain relatively stable then the

rate of enzyme-catalysed reactions decrease, this rate could affect an entire metabolic pathway.

Describe homeostasis as the process by which organisms maintain a relatively

stable internal environment:

– Homeostasis is the process by which organisms maintain a relatively stable (constant) or almost constant, internal

environment.

– Homeostasis falls into 2 categories, depending if it is exothermic (doesn't produce own heat) or endothermic

(produce own heat). An organism may be a conformer or a regulator .

Regulators try to maintain the parameter at a constant level over possibly wide environmental variations.

Conformers allow the environment to determine the parameter.

Explain that homeostasis consists of two stages

– Detecting changes from the stable state;

– Counteracting changes from the stable state:

– Homeostasis in endotherms is carried out in 2 steps, this mechanism is known as feedback:

Detecting change.

Counteracting the change.

– Detecting Changes:

Any change that provokes a response is a stimulus.

Receptors detect stimuli.

Examples of external stimuli: light, day length, sound, temperature, odours.

Examples of internal stimuli: levels of CO2, oxygen levels, water, wastes.

Receptors can range from a patch of sensitive cells, to complex organs like the eyes and ears of mammals.

– Counteracting Changes:

After receptors detect changes, organisms can then react to the change.

This type of response will counteract the change to ensure the stable state is maintained.

Effectors bring about responses to stimuli.

Effectors can either be muscles or glands:

Muscles bring about change by movement

Glands bring about change by secreting chemical substances

Gather, process and analyse information from secondary sources and use

available evidence to develop a model of a feedback mechanism:

– The mechanism that brings about homeostatic change is called FEEDBACK

– Homeostasis does not maintain the exact set point, but homeostasis is maintained as long as there is only a narrow

range of fluctuation (increase and decrease) of the variable around the set point. If the fluctuation is large (this is

the most common in humans), and exceeds the normal range, a negative feedback mechanism comes into

operation in response to this change; it is termed negative because it counteracts (negates) the change, thus

returning the body to within the normal range.


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– In living organisms, the feedback system has 3 main parts:

Receptors: a type of sensor that constantly monitors the internal environment

Control Centre: receives info from the receptors and determines the response

Effector: Restores the set value. Keeps environments stable.

– An example of a feedback system would be the control of carbon dioxide levels (an increase in it):

Outline the role of the nervous system in detecting and responding to

environmental changes:

– The nervous system is an organ system containing a network of specialized cells called neurons that coordinate

the actions of an animal and transmit signals between different parts of its body.

– The nervous system works to regulate and maintain an animal’s internal environment and respond to the external

environment, ie maintain homeostasis.

– The nervous system is made up of two parts:

Central Nervous System: This acts as a CONTROL CENTRE for all the body’s responses and it coordinates

all these responses, it consists of the brain (specifically hypothalamus) and the spinal chord where it receives

information, interprets it and initiates a response.

Peripheral Nervous System: This is a branching system of nerves that connects receptors and effectors. This

system transmits messages from the central nervous system and back. It acts as a communication channel.


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Identify the broad range over which life is found compared with the narrow

limits for individual species:

– Ambient temperature literally means the temperature of the environment; room temperature implies a

temperature inside a temperature-controlled building (the building has specific parts which affect the ambient

temp).

– Organisms on Earth life in environments with ambient temperatures ranging from less than 0ºC (such as arctic

animals) to more than 100ºC (such bacteria found in boiling undersea volcano vents).

– However, individual organisms cannot survive this entire range of temperatures for example mammals can only

survive temperatures from about 0 - 45ºC.

– This means that life is found in a very wide range of temperatures, but individual species can only be found in a

narrow temperature range.

Compare responses of named Australian ectothermic and endothermic organisms

to changes in the ambient temperature and explain how these responses assist

in temperature regulation:

Analyse information from secondary sources to describe adaptations and

responses that have occurred in Australian organisms to assist temperature

regulation:

– Ectotherms (cold blooded): are organisms that have a limited ability to control their body temperature (due to

their cellular activities generate little heat). Their body temperatures rise and fall with ambient temperature

changes.

Most organisms are ectotherms; examples are plants, all invertebrates, fish, amphibians and reptiles.

– Endotherms (warm blooded): are organisms whose metabolism generates enough heat to maintain an internal

temperature independent of the ambient temperature.

Examples are birds and mammals.

– Ectothermic response; Central netted dragon (Ctenophorus nuchalis):

Increase in temperature (ie hotter):

Stays in sheltered areas to avoid extreme heat. They can dig burrows or seek shelter in caves or crevices. This

reduces the effect of heat on their body.

It can change into nocturnal animal when the temperature becomes very hot. Many desert animals sleep in

burrows during the day and are active at night, to escape the heat.

Decrease in temperature (ie colder):

It will change its body position, to expose more of its body surface area to sun's rays, increasing core body

temperature.

They will seek areas of higher heat rays, such as on top of ledges instead of burrows.

– Endothermic response; Red Kangaroo ( Macropus rufus):

Increase in temperature (ie hotter):

It licks its arms to cool itself. The evaporation of the saliva cools its skin by convection.

It becomes less active, activity generates heat as many reactions are exothermic (release heat).

Decrease in temperature (ie colder):

Insulation: they have a thick fur layer, and contract their muscles controlling and shiver to generate heat.

They seek group warming, where they are exposed to less cold air.


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Identify some responses of plants to temperature change:

– Since plants cannot move from environment to environment, they respond to temperature by various changes:

– Increase in temperature (ie hotter):

Leaf orientation: Some plants can change the orientation of their leaves in relation to the sun at different times,

for example their leaves hang down vertically, to reduce exposure, thus controlling temperature.

Growth rates: They alter their growth rate for example; some Eucalyptus trees grow more in spring than in

winter, hence using less water which can be use for cooling itself.

– Decrease in temperature (ie colder):

Deciduous trees (trees that shed their leaves for a part of every year) lose their leaves in winter (leaf fall) and

undergo a period of dormancy, which allows them to survive not only the extremely low temperatures, but also

water shortages and lower availability of sunlight.

Plants may die above the ground, but leave bulbs, roots, rhizomes or tubers to survive underground. These then

sprout when favourable conditions return.


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2. Plants and animals transport dissolved nutrients and gases in a fluid

medium:

Perform a first-hand investigation using the light microscope and prepared

slides to gather information to estimate the size of red and white blood

cells and draw scaled diagrams of each:

– Aim: To estimate the size of red blood cells and white blood cells seen with a light microscope.

– Equipment:

Light microscope

Prepared slides of human blood

1mm sized Mini-grid plastic paper

Pencil and drawing paper

– Safety:

Slides can have sharp or unseen flint pieces of glass, gloves and glasses should be worn.

Use commercially prepared microscope slides of blood and not fresh blood, to eliminate the risk of contracting

blood-borne disease.

– Method:

The microscope on normal view ie 1X, has a limited field of view of 16mm.

Hence set your microscope with the millimetre-squared graph paper first. Then 'click' the 1X objective lense,

this will show you what the 'normal' eye of 16mm can see.

Then click the 10X objective, this will magnify the 10mm by a factor of 10. Hence now youll see a maximum

field of view of 1.6mm, and its sub-ten components. (also note 1mm= 1000µm)

Now using the 40X objective, this now makes the initial 16mm diameter four times less then the 10X, so the

diameter is approximately 0.4mm. Hence this diameter is 0.4mm, or 400µm

Now, putting a slide of a prepared blood, at 40X objective, estimate how many blood cells there exists in that

'field of view', approximately 50 red blood cells exist, hence the size of 1 RBC is 400 µm divided by 50

(400/50), which is 8 µm.

Now for white blood cells since there are so few of them, it is NOT possible to count the number of white cells

across the diameter, and even much more difficult to estimate how many would fit across the diameter. Hence

there size is estimated by proportion in comparison to that of RBC.


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– Result:

Red blood cells ( Erythrocytes):

Size: 6-9 µm

Shape: Bi-concave (concave on both side) discs

Function: Transport of oxygen.

They have no nuclei; they only live for 3 months. After this they are destroyed in the liver

or spleen.

5-6 million in every millilitre of blood.

They are produced in the bone marrow

White blood cells ( Leucocytes):

Size: 12-15 µm

Shape: Irregular shape; can change shape

Function: To defend against disease

Only 4-12 thousand per millilitre of blood

They have nuclei, unlike red blood cells

They are produced in the lymph glands.

Identify the forms in which each of the following is carried in mammalian

blood:

– Carbon Dioxide

– Oxygen

– Water

– Salts

– Lipids

– Nitrogenous wastes

– Other products of digestion


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– Carbon dioxide:

It is produced as a waste product of respiration in body cells. As its concentration is higher in the cell than in the

blood its diffuses in the blood:

70% of the carbon dioxide is converted into carbonic acid then changed into hydrogen carbonate ions. This

change from carbon dioxide to carbonate ions happens on the red blood cells. The ions are transported in the

plasma, NOT dissolved in it.

Bind to haemoglobin in erythrocytes forming carbaminohaemoglobin (only 23% of the carbon dioxide).

Be dissolved directly in the plasma (only 7% of the carbon dioxide).

– Oxygen:

Oxygen is needed in the body for respiration. It is brought in across the respiratory surfaces of the lungs.

It binds with haemoglobin in red blood cells, forming oxyhaemoglobin.

– Water:

Water is the solvent of plasma; it makes up the bulk of blood volume.

It makes up 60% of the volume of blood.

– Salts:

These are transported directly dissolved in the plasma as ions (ie NaCl as Na+ and Cl

-), these are known as

electrolytes.

– Lipids and other products of digestion:

The aim of digestion is to break large molecules down to a size small enough for absorption through theintestine wall and into the bloodstream, so that they can be transported to cells in the body where they are

required.

Lipids are any of a group of organic compounds (ie containing carbon), including the fats, oils, waxes, sterols,

and triglycerides that are insoluble in water, are oily to the touch, and together with carbohydrates and proteins

constitute the principal structural material of living cells.

Digested lipids are changed into triglycerides (this happens in the lining of the small intestine).

Lipids are then transported as chylomicrons (these are clusters of triglycerides, phospholipids and

cholesterol), wrapped in a coat of protein.

These are released into the lymph and eventually pass into the veins

Carbon + Water Carbonic Hydrogen + Hydrogen

Dioxide Acid Ions Carbonate Ions

CO2 + H2O H2CO3 H+ + HCO

-


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– Other products:

Nitrogenous wastes:

Wastes such as ammonia are changed in urea

Urea is transported dissolved in the plasma

Minute minerals:

Includes amino acids, sugars and vitamins

They are mainly water soluble and transported in the plasma.

Explain the adaptive advantage of haemoglobin:

– Haemoglobin is a protein made up of four polypeptide chains (called globins) and each is bonded to a haem

(iron-containing) group which can attach to an O molecule, forming oxyhaemoglobin.

– For every haemoglobin, 4 oxygen molecules can attach. There about 250 million molecules of haemoglobin in

each red blood cell, hence the very high oxygen carrying capacity.

– If blood carried oxygen without haemoglobin, the oxygen would have to be dissolved directly into the plasma

(into water). But oxygen is not very soluble in water therefore, if oxygen was carried only by being dissolved in

blood plasma, 100 ml of water would only be able to carry 0.2 ml of oxygen.

– The presence of haemoglobin increases the oxygen carrying capacity of blood by 100 times

Dissolved only 0.2 ml O2/ 100 ml blood

Haemoglobin 20 ml O2/ 100 ml blood

– The adaptive advantage:

It increases the oxygen carrying capacity of blood (proven above). Mammalian cells need a lot of energy and

therefore must have a continual supply of OXYGEN for RESPIRATION; this ability of blood to carry large

quantities of oxygen gives mammals a considerable survival advantage. The extra energy allows mammals to be

active, as well as grow large.

It has the ability to bind oxygen at an increasing rate once the first oxygen molecule binds to it. The bonding of

each oxygen molecule causes the haemoglobin to change slightly in shape, making it easier for every subsequent

oxygen molecule to bind to it. This increases the rate and efficiency of oxygen uptake. As a result, a very small

increase in the oxygen concentration in the lungs can result in a large increase in the oxygen saturation in the

blood.

It has the capacity to release oxygen at an increasing rate when carbon dioxide is present. Metabolising cells

release carbon dioxide, which combines to form acidic carbonic acid, and this lower pH, thus increases chances

to affect enzymes, and toxicoses cells (acid is corrosive).

It can undergo the Bohr effect , which at lower pH (due to increasing CO2) levels can release oxygen to tissue

areas that in need of it.

Outline the need for oxygen in living cells and explain why the removal of

carbon dioxide from cells is essential:

– Cells require oxygen in the process of respiration:

Glucose + oxygen carbon dioxide + water + energy (in the form of ATP).

– Carbon dioxide is a waste product and must be removed to maintain the normal pH balance of the blood. By

removing excess carbon dioxide, it prevents a build up of carbonic acid, which causes the lowering of the pH, and

therefore increasing breathing rate and depth. Carbonic acid forms when carbon dioxide dissolves in water. At

normal levels, the carbon dioxide; bicarbonate ion (HCO3-) equilibrium is an important mechanism for buffering


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the blood to maintain a constant pH, if greater amounts of carbon dioxide are produced the body cells (blood and

lymph) will become acidic, enzymes can only function within a specific pH range, therefore an increase in carbon

dioxide will result in lowering the pH which will affect the overall metabolism of the body.

Perform a first-hand investigation to demonstrate the effect of dissolved

carbon dioxide on the pH of water:

– Aim: To model the effect of carbon dioxide on the pH of water.

– Equipment:

25ml of Distilled water in 100mL beaker

Universal indictor (its an indicator that changes colour depending on the pH of a solution)

pH probe attached to data logger

– Safety:

Gloves and glasses should be worn, in case of glass breaking.

The water can become corrosive due to increasing pH, it should NOT be ingested after use, dispose in an

organic waste container.

Straws should NOT be used by more then one student, to minimise contracting diseases.

– Method:

In a beaker, pour water till the 25mL grade mark, then put 3 drops of universal indicator, this should now

change into greenish colour.

Then put the pH probe, and check the pH is about 7.

Exhale air into the straw that is dipped into the solution, for about 3 minutes.

– Result:

After about 30 seconds, the colour of the solution began to change into pale yellow, and the pH on the data

logger started decreasing.


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This is because carbon dioxide forms a weak acid; carbonic acid (H2CO3) so the water becomes more acidic.

Carbonic acid in water dissociates to form hydrogen carbonate ions (HCO3-), and some carbonate ions (CO3

2-).

Analyse information from secondary sources to identify current technologies

that allow measurement of oxygen saturation and carbon dioxide

concentrations in blood and describe and explain the conditions under which

these technologies are used:

Technology How it Works The Conditions It Is Used

Pulse

oximeter

Measures O2 levels ONLY.

Device like a peg sits on the finger and

measures the transmission of light through

tissues ie measures the amount of oxygen in

arterial blood.

There is a large difference between red light

absorbed by haemoglobin compared to

oxyhaemoglobin, hence this can be analysed

to give a reading.

Used in many conditions; this is because it is

painless, easy to apply and quick to give results,

example:

During surgeries, to monitor patients under

anaesthesia.

Monitor premature babies that are in neo-natal

wards.

Can be used as a general check-up procedure to

analyse O2 levels

Arterial blood

gas (ABG)

analysis

Measures O2 and CO2 levels.

Measures pressure (or the

concentration) of O2 and CO2 in the

blood

Measures saturation of oxygen (which is

the amount of oxygen combined to

haemoglobin compared to the

maximum)

Measures levels of bicarbonate and pH

(to show CO2 levels)

This analysis evaluates how effectively the

lungs are delivering oxygen and removing

carbon dioxide.

Used when there are signs of dangerously low

oxygen or high carbon dioxide levels.

Helpful for monitoring patients under

anaesthesia, in intensive care, in accident or

emergency facilities and for premature babies.

Helps for diagnosing as well as monitoring

patients eg a patient in a coma can have their

blood gases regularly monitored.


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Compare the structure of arteries, capillaries and veins in relation to

their function:

Arteries Veins

Diagram

Structure Thick walled, elastic, muscular Thinner walls then arteries, elastic, lessmuscle , wider diameter (larger lumen)

Direction of blood: flow / pressure

Carry blood away from heart, pressurecreated by hearts pumping puts stress on

arteries, blood pressure is high

Carry blood to heart, as there is no stress onveins the blood pressure is low

Blood movement andrate

Contain muscle fibres which contract and

relax, rate is maintained as blood travels inspurts towards body tissues

Contain no muscle, rely on valves and when

large muscle contract they help push the bloodflow through the veins

Carries Oxygenated blood taken away from heart Deoxygenated blood taken to the heart

– Capillaries:

Capillaries are an extension of the inner layers of the arteries and veins (Artery arterioles capillary

venules veins).

Capillaries are only one cell thick, and are so narrow, that only one red blood cell can pass at a time.

Capillaries surround all tissue cells, thus they provide a very large surface area over which exchange of

materials between blood and body cells can occur.


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Describe the main changes in the composition of the blood as it moves around

the body and identify tissues in which these changes occur:

– Pulmonary circuit (From Body to HEART to the Lungs):

Blood enters the right atrium of the heart via the vena cava (major vein):

The blood is deoxygenated , and high in carbon dioxide.

It is also low in glucose and other nutrients; high in urea, other nitrogenous wastes and various poisons.

As the heart beats, the right ventricle pumps the blood through the pulmonary artery, to the lungs:

Here the blood gains oxygen through exchange with alveoli in the lungs (ie air sacs), and loses its carbon

dioxide.

The blood then enters the left atrium via the pulmonary vein.

– Systemic circuit (From Lungs to HEART to the Body):

The left ventricle pumps oxygenated blood to the body through the aorta.

In the body, various changes occur to the blood.

The blood loses oxygen and gains carbon dioxide in all body cells, as respiration occurs.

In the Liver:

Levels of glucose are regulated: excess glucose is changed to glycogen, or glycogen stores are changed to

glucose (if needed).

Excess amino acids are changed to ammonia, and then to urea.

Poisons are also reduced, as the liver changes them to less toxic forms.


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In the Intestines:

Levels of nutrients from digestion increase.

Glucose, amino acids, ions, lipids and other substances from food enter the blood.

In the Kidneys:

Salt and water levels are regulated.

All urea is removed, toxins are excreted into the urine.

The changed blood, again highly deoxygenated, from the body then flows back to the pulmonary circuit.

Analyse information from secondary sources to identify the products extracted

from donated blood and discuss the uses of these products:

– Red blood cells:

Used to increase the amount of oxygen that can be carried to the body’s tissues; given to anaemic patients, or

people whose bone marrow do not make enough red blood cells

– Plasma:

This liquid portion of the blood, is given to people with clotting disorders (such as haemophilia), and also used

to adjust the osmotic pressure of the blood (to pull fluids out of tissues).

– White blood cells:

Infection fighting component of the blood.

Analyse and present information from secondary sources to report progress in

the production of artificial blood and use available evidence to propose

reasons why such research is needed:

– The problems of using real blood:

Shortage of real blood

It has to be ‘cross-matched’. This is because, if you receive the wrong type of blood, it can be fatal. This is a

great disadvantage in emergency situations.

It has to be free of infectious agents. Only blood that is free of bacteria and infectious agents (such as HIV) can

be used. Testing the blood is costly.

It has a short shelf-life. Because red blood cells only survive for 3 months, the blood has a short life span (blood

can only survive for 3-4 weeks).

– Proposed replacement; Perflurochemicals (perflurocarbons):

Synthetic and inert, are completely sterile

Cheap to produce, compared to using real blood.

Can dissolve 5 times more oxygen than blood.

Free of biological materials, therefore no risk of infections

BUT; must be combined with other materials to mix in with the bloodstream (eg lecithin).


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Choose equipment or resources to perform a first-hand investigation to

gather first-hand data to draw transverse and longitudinal sections of

phloem and xylem tissue:

– Aim: To draw the transverse (top view) and longitudinal section (side view) of plant tissue (ie xylem and phloem).

– Equipment:

A stick of celery

Red food colouring

Water in a 100mL beaker

Razor blade

Light microscope

– Safety:

The razor blade is extremely sharp, gloves should be worn incase of accidental flicking of blade onto skin.

Glasses should be worn incase of glass breaking.

– Method:

In the 100mL beaker filled with water, put 3-5 drops of red food colouring into the solution. It should change to

dilute red colour.

Place the celery stick into the beaker, and leave it over night, so the coloured water can seep into the plant

sections to rise through xylem vessels, hence staining them strongly. Some water also travelled down the

phloem vessels.

Using a sharp one-sided razor blade, very thin slices were cut from across the stalk (for the transverse section)

and from the length of the stalk (for the longitudinal section).

Suitable slices were then prepared as wet mounts and viewed under a light microscope.

– Result:


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Phloem:


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Xylem:

Describe current theories about processes responsible for the movement of

materials through plants in xylem and phloem tissue:

– There are 2 types of transport tissues in plants:

Xylem: This transports water and mineral ions upwards from the roots to the leaves of a plant.

Phloem: This transports organic materials (particularly sugars) up and down the stem to other parts of the plant.


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– There exist two theories (ie possible explanations based on evidence) into how water/nutrient moves in each tissue

respectively.

In Xylem:

The transpiration stream theory (ie cohesion-adhesion-tension theory) possists that due to physical forces of

water (and ions) being removed from the plant stomates by passive transport (ie transpiration), causes a

column of water to be sucked up into the stem by the evaporative pull, also the low concentration of water at

the roots allows more water to diffuse in.

Once water has been absorbed into the roots of plants (by osmosis) along with mineral ions (by diffusion and

active transport), these substances move across the root into the xylem. A small amount of root pressure

results from the continual influx of more water and ions, hence forcing the solution already present upwards

(due to pressure build up), however this is usually not enough.

The constant loss of water, leads to a transpiration stream (which is the constant upward flow of water

through a plant), this is because of waters 2 properties, which are adhesive forces (the ability of molecules to

attach to walls), and cohesive forces (the attraction of molecules to each other), hence leading to the

capillarity (water rising up through bore of tissue) and hence the stream.

In Phloem:

The pressure flow theory (ie source-path-sink theory) states that in the plants, there are sources of nutrients,

e.g. leaf cells are the sources of sucrose. As the sucrose, amino acids and other minerals build up, the cells

actively transport the glucose sugars by active transport into the phloem tubes, this is known as loading, it

can be done by 2 ways:

Symplastic Loading: Sugars and nutrients move in the phloem from the mesophyll cells to the sieve

elements through the plasmodesmata that join adjacent cells (note: Plasmodesmata have not been found in

all plants).


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Apoplastic Loading: sugar and nutrients move along the cell walls to the sieve plate. Then they cross the

cell membrane by active transport to enter the phloem tube.

As sugars enter the phloem the concentration of phloem sap increases, this causes the entry of water by

osmosis from the surrounding cells (osmotic pressure gradient is low). This resulting pressure causes water

and dissolved solutes to flow towards a SINK.

A sink is a region of the plant where sugars and other nutrients are actively begin removed from the phloem.

As sugars move out of the phloem, water flows out with them. This reduces the pressure in the sieve cells at

the sink region.

Materials are transported both up and down the stem and are distributed especially to the growing points and

reproductive structures, including developing fruits and seeds, it is driven by a gradient generated osmotically.


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3. Plants and animals regulate the concentration of gases, water and waste

products of metabolism in cells and in interstitial fluid:

Explain why the concentration of water in cells should be maintained within

a narrow range for optimal function:

– Water makes up around 70-90% of living things; it is essential for life, it is the solvent of all metabolic reactions in

living cells (universal solvent), and sometimes directly takes part in it (eg. respiration). Therefore a deviation can

cause:

Isotonic: Concentration of solutes outside the cell is the same as inside the cell. No overall movement of water.

Hypertonic: Concentration of solutes is greater outside the cell than inside. Water tends to move out of the cell.

Hypotonic: Concentration of solutes is greater inside the cell than out. Water tends to move inside the cell.

– Living cells work best in an isotonic environment where the levels of water in cells need to be kept relatively

constant, any change in the concentration of solutes will result in a change in the levels of water in cells which

usually results in death (either dehydration or cell bursting)

– Enzymes also require specific conditions of functioning, some of which could relate to the levels of water andsolutes in cells, as an increase in water changes the concentration of acid (either dilutes it or makes it

concentrated).

Explain why the removal of wastes is essential for continued metabolic

activity:

– As a result of metabolism, many waste products are formed, for example:

In the process of deamination (process by which amino acids and proteins are broken down into ammonia),

ammonia is highly toxic and must be removed or changed to a less toxic form. It can greatly increase the pH and

make it more alkaline.

It carbon dioxide acculmates, it can form carbonic acid, which lowers the pH.

– If these toxins are allowed to accumulate, they would slow down metabolism and kill the cells (e.g. excess toxins

is acidic thus increases pH, affection enzyme function which can lead to denaturation), this is why they need to

quickly be removed, or converted into a less toxic form.


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Identify the role of the kidney in the excretory system of fish and mammals:

– The maintenance of a constant concentration of nutrients, water and waste products in the internal environment of

organism, is crucial to its wellbeing. The concentration of these substances directly affects metabolism in cells,

and hence needs to be balanced.

– Many wastes are excreted (process by which waste products, which have been produced as a result of metabolism,

are removed from the body). The excretory system is made up of systems and organs that carry out the removal of

metabolic wastes.

Carbon dioxide is excreted via the lungs (ie respiratory system).

Nitrogenous wastes are removed along with excess salts and water via the kidneys (ie urinary system).

– The kidney is an organ of the excretory system of both fish and mammals. It plays a central role in homeostasis,

forming excreting urine while maintaining osmoregulatory.

– Osmoregulation: means the physiological processes that an organism uses to maintain water balance; that is, to

compensate for water loss, avoid excess water gain, and maintain the proper osmotic concentration (osmolarity) of

the body fluids.

Distinguish between active and passive transport and relate these to

processes occurring in the mammalian kidney:

Explain how the processes of filtration and reabsorption in the mammalian

nephron regulate body fluid composition:

– Active transport: is the process of using energy to transport substances across highly concentrated membrane

from an area of low concentration, it would normally not be able to cross due to a concentration gradient (the

amount of substance in a particular area).

– Passive transport: is the process of movement substances across a membrane from an area of higher

concentration to an area of lower concentration without energy expenditure (this is diffusion and osmosis).

– The excretory system is a group of organs that function together remove metabolic wastes from the tissues of an

organism and expel them to the outside, a kidney is the main excretory organ responsible for removing

nitrogenous wastes from the bodies of vertebrate animals (including fish and humans).

– The function of the kidney in excretion is to filter the blood that enters it, removing the waste in the blood

solution, for this waste to be excreted. This filtration is carried out by millions of small filtering units that are in

kidneys which are known as nephrons.

The nephron is a regulatory unit; it absorbs or secretes substances in order to maintain homeostasis, this

regulation maintains the constant composition of body fluids which is done by adjusting salts and water levels to

maintain fluid concentration, different ions also adjusted to maintain pH.

– Urine is the final solution produced by these microscopic tubules, and passes out the kidney via ducts (ureters) and

then goes to the urine storage organ (bladder), which after a certain limit fills and the human passes this urine

through the urethra to the outside. (In vertebrates this goes to the a chamber (cloaca) instead of the urethra, which

empties to the outside)


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– Detailed structure of a nephron:

It consists of 4 parts (in order of movement) THAT are heavily surrounded by capillaries: Bowmans capsule

Proximal (ie first) convoluted tubule the loop of Henle Distal (ie second) convoluted tubule

collecting duct which produces urine that leads to the bladder.


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– Function of nephrons

Three main process occur in the kidney, in the parts mentioned above, they are filteration reabsorption

secretion.

Filtration:

When highly oxygenated, unfiltered blood enters the kidney through the renal artery it goes to the nephrons,

upon reaching it splits into a spherical network of blood capillaries called glomerulus that are in a Bowman's

capsule, the blood pressure here is so high that fluid and substance from the blood are forced into theBowman’s capsule, and forms a fluid called the glomerular filtrate.

Blood cells and proteins are retained in the blood, while large volumes of water pass through contained

dissolved substances such as: water, amino acids, glucose, salts (ions), nitrogenous wastes and other toxic

molecules.

This process is known as filtration, it separates based on SIZE of molecules, since proteins and RBC are

larger then other molecules they cannot pass the Bowmans capsule. Therefore:

Substances that the body needs will require reabsorption, so they are not lost with urine.

Additional wastes that were in the bloodstream, and managed to escape the higher pressure of the Bowmans

capsule need to be added to this 'urine' mixture.

Hence this is not the final fluid excretion.


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Reabsorption:

Depending on the feedback of the body, varying amounts of solutes are reabsorbed from the solution, for

example water, amino acids, glucose, salts (Na+, K +, Cl-, Ca2+, Mg2+, HCO3-).

This occurs in the proximal, loop of Henle and distal tubules.

In the proximal tube:

All organic nutrients (amino acids and glucose) are reabsorbed, aswell as some ions such as (Na+, K

+, Cl

-,

Ca2+

, Mg2+

, HCO3-).

In the loop of Henle:

After the initial reabsorption from the distil tube, you'll have a liquid that is primarily urine, whether its

concentrated or not, is dependent in the loop of Henle.

The loop of Henle has 2 limbs, a descending then ascending, where the descending is permeable to water

ONLY, and the descending is permeable to salt ONLY.

Secretion:

This is the last process and leads to the formation of urine. It occurs in the distil and collecting tubule.

The liquid present in the tubule, are then added with metabolic wastes (such as urea, ammonia, hydrogen ions,

durgs: pencillin, morphine) etc that are brought by active transport to the distil tubule.


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Explain why the processes of diffusion and osmosis are inadequate in

removing dissolved nitrogenous wastes in some organisms:

– Diffusion and osmosis are both examples of passive transport (ie they do not require energy), this is too slow for

the normal functioning, because the movement of molecules relies on differences in the concentration gradient

between two solutions (it moves from high conc. to low conc.)

– Also this process greatly slows down once the difference in concentration gradient becomes smaller, and stops

once the concentrations are at equilibrium.

– Further problems with:

Diffusion:

Toxins such as drugs can accumulate in the body, and can only be removed if they are in water, hence they

would ONLY move if there was a higher concentration of toxins in the blood then the urine itself. And this

would stop if the concentrations equalise.

Osmosis:

Too much water is lost in urine: If there is a high concentration of urine, water will continually be drawn from

the body to even out the conc. gradient. However, excretion of dilute urine means the loss of large amount of

water from body, a loss to great for terrestrial animals.

Osmosis only deals with the movement of water and thus would only allow water to move out of the body,

not the nitrogenous wastes.

Perform a first-hand investigation of the structure of a mammalian kidney by

dissection, use a model or visual resource and identify the regions of the

mammalian kidney involved in the excretion of waste products:

– Aim: To identify the regions of the mammalian kidney, notably the ones involved in the excretion of waste

products.

– Equipment:

One commercially packed cow (mammalian) kidney

One sharp medical cutting scalpel

Dissecting tray

Clean 'laying' paper

Latex gloves

Tissue forceps (they are things that help pull skin)

Disinfecting agent

– Safety:

Gloves and protective face masks are crucial, incase of a diseased kidney, or the possible contracting of a

disease between touching.

Gloves are also crucial in handling of sharp object, incase of accidental damage.

Disinfecting agent was used on the tray, and the paper, incase of airborne particles that may be ingested and

cause allergies or disease.

Material was carefully disposed, to inhibit the build up of bacteria and other organisms.

– Method:

Carefully layer brush the tray with agent, and paper, and place them together. Place the kidney facing sideways, and carefully cut sideways to obtain a 'longitudinal' cut (ie sideway cut), using

forceps to open the skin.


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– Result:

The kidney is made up of 3 sections, the pelvis, the medulla and the cortex, the obvious observable sections

where located, and an imaginary "large" nephron was placed, to observe where the 3 mains process (ie

filteration reabsorption secretion) occur.

Cortex:

Contains the glomeruli. It is very dark red due to the capillaries It is involved in the filtration of blood.

Medulla:

Contains the nephron tubules, as can be observed by the striped appearance of the medulla

It is involved in the reabsorption and secretion of substances

Pelvis:

It is where all the collecting ducts connect to, ie the collecting of urine.

Gather, process and analyse information from secondary sources to compare

the process of renal dialysis with the function of the kidney:

– People with disfunctional kidneys are not able to remove wastes such as urea, they have to undergo renal dialysis

to regulate their blood.

– Renal dialysis is an artificial process in which waste in the blood are removed by diffusion across a partially

permeable membrane of solution known as dialysis fluid. It is a solution of salts, glucose, dissolved gases and

other substances (it has an equivalent composition to interstitial fluid), wastes (particular urea and excess salts),

diffuse out of the blood into the dialysis fluid. The clean blood is then returned.


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– The process:

The blood is extracted from the body from a artery (as it has come from the heart with oxygen, and going to

body to pass its waste and regulate levels etc, but it cant as kidney has failed hence blood from artery is used)

and passed into a dialyser, which is is a medical unit which is a bundle of hollow fibres made of partially

permeable membrane to help units suffering from artery failure.

The dialyser is in a solution of dialysing fluid, which has similar concentrations of substances as blood.

The dialyser only allows wastes to pass through, and not blood cells and proteins (in this way it is similar to the

filtrations stage of the nephron).

The wastes diffuse into the solution, and it is constantly replaced

The anti-clotting agent, heparin, is also added to prevent clotting.

The blood is then returned to the body via a vein.

– Comparison of dialysis and normal kidney function:

Kidneys Renal Dialysis

- Continuous process; very efficient - Slow process; occurs a few times a week for

patients

- Active and passive transport is used throughout

the nephron

- Only passive transport is used

- Useful substances are reabsorbed actively by

the kidney

- Useful substances are not reabsorbed as they

diffuse into blood from dialysing fluid

- Uses a series of membranes (nephrons) which

are selectively permeable.

- Also uses membranes (but artificial) which are

selectively permeable.


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Outline the role of the hormones, aldosterone and ADH (anti-diuretic

hormone) in the regulation of water and salt levels in blood:

– Recall:

Dehydration is defined as an excessive loss of body fluid.

Blood volume is the volume of blood (both red blood cells and plasma) in a person's circulatory system. Blood

volume is determined by the amount of water and sodium ingested, excreted by the kidneys into the urine.

– A hormone is a chemical released by one or more cells that affects cells in other parts of the organism. It is

essentially a chemical messenger that transports a signal from one cell to another, only a small amount of hormone

is required to alter cell metabolism. All multicellular organisms produce hormones however animals usually

produce hormones which are often transported in the blood.

– The kidneys maintain constant conditions within the body by excreting wastes such as urea and by regulating the

amounts of water and salts that are reabsorbed. This aspect of homeostasis is mainly due to the actions of two

hormones: aldosterone and antidiuretic hormone (ADH):

– ADH (Anti-Diuretic Hormone):

Also called vasopressin, anti-diuretic hormone literally means (anti-'water losing'), diuretic are heavily used in

pro-bodybuilding shows to lose water.

It controls the reabsorption of water, this is done by adjusting the permeability of the collecting ducts and the

distal tubules.

Hence a release of it (ie increase levels), increases (sucks) water out from the tubules, hence the urine

becomes more concentrated (as less water is present).

It is made in the hypothalamus in the brain, but stored in the pituitary gland . Receptors in the hypothalamus monitor the concentration of the blood:

High Salt Concentration: ADH levels increased, collecting ducts and distal tubules become more permeable to

water, more water reabsorbed, concentration returns to normal. (Concentrated urine)

Low Salt Concentration: ADH levels reduced, collecting ducts and distal tubules less permeable to water, less

water absorbed, concentration returns to stable state. (Dilute urine)

ADH does not control the levels of salt in the blood. It only controls the concentration of salt through water

retention.

– Aldosterone:

Is a hormone that increases the reabsorption of sodium and the release (secretion) of potassium in the kidneys.

Hence a release of it (ie increase levels), causes more salts to be sucked out of the tubules.

Aldosterone is produced by the outer-section of the adrenal cortex in the adrenal gland, (which sits above the

kidney) and acts on the distal tubules and collecting ducts of the kidney.

When there is a lack of absorption of salts (ex. NaCl, NH3, K + etc) , a signal goes to the hypothalamus which

triggers the secretion of aldosterone.

High Salt Concentration: Aldosterone levels decreased, less salt reabsorbed, hence less water diffusing into

body cells.

Low Salt Concentration: Aldosterone levels increased, more salt reabsorbed, more water diffusing into body

cells.


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Present information to outline the general use of hormone replacement

therapy in people who cannot secrete aldosterone:

– This is a second developed technology, where the first was renal dialysis to aid people with affected kidneys.

– Addison’s disease is a rare endocrine disorder occurring when the adrenal glands, seated above the kidney, fail to

produce enough aldosterone. Without aldosterone, the body would not be able to reabsorb salt (specifically sodium

ions) this would cause severe dehydration and excessive potassium loss which may cause brain damage and death.

– The artificial replacement hormone is called Fludrocortisone, a drug that decreases the amount of salt the body

excretes. It is taken either orally or intravenously, patients are also advised by their doctors to increase their salt

intake.

Define enantiostasis as the maintenance of metabolic and physiological

functions in response to variations in the environment and discuss its

importance to estuarine organisms in maintaining appropriate salt

concentrations:

– Homeostasis is the process by which organisms maintain a relatively stable (constant) or almost constant, internal

environment.

– Enantiostasis is the maintenance of metabolic and physiological functions in response to variations in the

environment.

– The difference between the two, is the fact that homeostasis requires only a SPECIFIC internal condition for an

organism to function properly, example 37o

is the required temperature for humans to function, enantiostasis is for

a VARIETY of internal condition which the function can function properly at, for example diving birds rely on

enantiostasis to function properly at extremely high and low pressure sky levels.

In homeostasis heat is 'acted against' by sweating etc, the pressure for birds isn't 'acted against'; it is 'adapted' to.

– An estuary is where a freshwater river meets and mixes with saltwater sea, and as such the salinity levels are

always changing dramatically. This is determined by the tide of the sea:

At high tide: sea water flows into the river mouth, creating an environment with higher salt concentration, hence

this salt water has the tendency to draw water out cells by osmosis (as the organism will be in freshwater)

At low tide: sea water flows out of the river mouth, and freshwater from the estuary is abundant, hence by

diffusion organism face the challenge of water moving into their tissue.

– Organisms living in such an environment need to have mechanisms to cope with such changes in order to survive,

this is collectively called enantiostasis.

– Enantiostasis is carried out by 2 process (these are present in normal homestasis conditions too, but they carry out

different roles):

Osmoconformation: process by which organisms tolerate the changes in the environment, and conform, or alter

the concentration of their internal solutes to match the external environment. Their metabolism can handle it.

Osmoregulation: is the control of the levels of water and mineral salts in the blood.


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Process and analyse information from secondary sources and use available

evidence to discuss processes used by different plants for salt regulation

in saline environments:

– Salt, even in small concentrations, has a damaging effect on cell metabolism.

– Halophytes are plants that adapted and can tolerate high salt levelled environments, they are commonly found in

areas such as estuaries.

– Grey Mangroves ( Avicennia marina ):

Salt Prevention: In its roots, it has a layer of cells that actively restrict the movement of salt into xylem vessels.

Salt Exclusion: Special glands in the mangroves can actively exclude the salt from the water, so that the water

absorbed has a lower salt concentration than the water in the environment.

Salt Accumulation: Salt is accumulated in old leaves that drop off, so that the salt is out of the plant’s system

Salt Excretion: Salt can be excreted from the underside of the leaves of the mangrove plants; salt crystals form

under the leaves.

Describe adaptations of a range of terrestrial Australian plants that assistin minimising water loss:

Perform a first-hand investigation to gather information about structures in

plants that assist in the conservation of water:

– Aim: To gather information from plant specimens about structures that assist in the conservation of water.

– Equipment:

Different type of leafs that exist around the school (typical environment)

Hand lens

– Safety:

Sun has strong UV light outside, sunscreen and hats should be worn.

Leaf can be diseased and can have splinters and can be sharp, gloves should be worn.

– Method:

Carefully, leaves where looked at for different 'prominent' features that could inhibit water loss, these where

then cross-checked with reliable sources.

– Result:

Banksia:

Leaves have sunken stomates: this reduces transpiration.

Hard, waxy cuticles: this reduces the amount of water loss through transpiration.

Eucalyptus trees:

Hard, waxy cuticles: this reduces the amount of water loss through transpiration.

Leaves hang vertically: reduce sun exposure.

Spinifex grass:

Have extensive root systems that can reach underground water.

Leaves are also long and thin: to reduce water loss by transpiration.

Can roll up to hide their stomata's: this reduces the amount of water loss through transpiration.

Analyse information from secondary sources to compare and explain the

differences in urine concentration of terrestrial mammals, marine fish and

freshwater fish:

– Freshwater Fish:


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Osmotic Problem: Hypotonic to environment. Water diffuses INTO their bodies. Salts diffuses out.

Role of Kidney: Doesn’t drink continually, Kidneys removes excess water, while reabsorbing salts.

Urine: Large, dilute amount.

– Marine Fish:

Osmotic Problem: Hypertonic to environment. Water diffuses OUT of their bodies. Salt diffuses in.

Role of Kidney: Continually drinks water, Kidneys reabsorb water, while actively secreting salts.

(Salt is also excreted across gills)

Urine: Small, concentrated amount.

– Terrestrial Mammals:

Osmotic Problem: Water needs to be conserved.

Role of Kidney: Regulates concentration of blood, while at the same time excretes urea and conserves water.

Urine: Concentration changes with the availability of water, as well as temperature and water loss through

sweat. Water levels in blood rise, urine amount rises, and concentration decreases and vice versa.

Explain the relationship between the conservation of water and the

production and excretion of concentrated nitrogenous wastes in a range of

Australian insects and terrestrial animals:

– Ammonia is the direct result of amino acid breakdown (deamination) and is a waste product of all organisms. It is

very water soluble, but VERY toxic, and must be removed quickly, or changed to a less toxic form.

– The removal of ammonia would require large volumes of water, and this is not possible for animals or insects that

seek to conserve water.

Aquatic Animals and Fish: These organisms directly release AMMONIA into the environment. This uses a lot

of water, but they have no need to conserve it. Ammonia is very water soluble and is excreted through the gills.

Terrestrial Animals: Releasing ammonia would be impossible due to lack of water. Instead, land-dwellerschange ammonia into less toxic forms and release it periodically. Mammals change it into UREA and release it

as urine (ex; kangaroos, wallabies, hopping mice and koalas). Australian animals release very concentrated

urine, and are able to tolerate high levels of urea in their bodies.

Birds: Birds change ammonia into URIC ACID, a whitish paste which uses hardly any water. This is lighter

than using urea, and helps in flight.

Insects: Insects also change ammonia to URIC ACID.

Ahmad Bio Notes

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