Syllabus:

1. Most organisms are active in a limited temperature range

DP1 “identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates”

o Enzymes are biological catalysts. This means that they lower the energy required to start a chemical reaction within a cell but do not get used up by that reaction. Every reaction and process within a cell (metabolism) is controlled by a specific enzyme.

o Enzymes are globular proteins whose shapes are specialised so that other chemicals (substrates) can form a temporary bond with them. There are two models used to show how an enzyme work:

o One model used to illustrate the action of an enzyme is the lock-key model. This is where only one small part of the enzyme molecule can form a complex with the substrate. This part of the molecule is called the active site. Only a specific substrate(s) can bond in that site and this makes the enzyme specific to that substrate.

o The induced fit model, a more recent modification on the lock-key model, proposes that the active site slightly changes its shape to accommodate the substrate perfectly.

DP2 “identify the pH as a way of describing the acidity of a substance” The pH of blood is between 7.2 and 7.4 (neutral)

DP3 “explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency”

Behavioural adaptationsThe following adaptations are common to Endo and Ectotherms.

1. Migration – Animals can move to avoid temperature extremes. Behavioural.

2. Hibernation – Some animals remain in a sheltered spot, their metabolism slows, and in endotherms their body temperature drops.

3. Shelter – Animals seek shelter from extreme conditions. They may dig burrows or hide in caves. For Ectotherms such as lizards, basking in the sun and sheltering in shade may both be part of regular daily activity to keep the body temperature reasonably constant.

4. Nocturnal activity – The brown snake is usually active during the day, but when it gets very hot they become nocturnal and their active period is at night time.

5. Controlling exposure – Ectotherms such as lizards may alter their posture to gain as much access to sunlight as possible through increasing their surface area. Endotherms may cuddle up or huddle together to reduce heat loss.

Structural And Physiological Adaptations Of Endotherms1. Insulation – Fur in mammals and feathers in birds maintain an insulating

layer of trapped air that slows down heat exchange with the environment.2. Metabolic activity – Endotherms generate heat as a result of their

metabolic activity. In cold conditions this keeps the body warm; one of these means is shivering which drastically reduces heat loss.

3. Control of blood flow – Endotherms may increase or decrease heat exchange with the environment by controlling the blood flow to their skin and extremities. This enables the skin temperature to be lowered while maintaining a normal internal body temperature.

4. Counter-current exchange – Is used by some endotherms in cold conditions. Blood vessels leading to and from the extremities of the body (E.G. the tail and the legs) are placed close together and chilled blood returning in the veins picks up heat from the arteries going to extremities.

5. Evaporation – By controlling the rate of evaporation of water from their bodies, endotherms can help keep themselves cool. E.G. Humans sweat, dogs pant and bird flutter a membrane in their throat.

DP4 “describe homeostasis as the process by which organisms maintain a relatively stable internal environment”

Homeostasis is the maintenance of a balanced or stable internal environment.

Examples of conditions or features maintained by this process include:o Temperatureo Water Concentrationo Blood Pressureo Oxygen Concentrationo Blood Sugar Levelo Carbon Dioxide Concentrationo Salt Concentrationo Urea Concentrationo pH Level

A feedback mechanism is one in which the response alters the original stimulus.

o If the response causes an increase in the stimulus, it is said to be positive feedback. E.g. Oxytocin is produced in women during childbirth to expand the cervix, this is done even though it is defies homeostasis.

o If the response opposes or counteracts the stimulus, it is called negative feedback.

DP5 “explain that homeostasis consists of two stages:” detecting changes from the stable state counteracting changes from the stable state Homeostasis involves two key steps:

o Detection of any change within the internal environment.o Counteract the change that has taken place.

DP6 “outline the role of the nervous system in detecting and responding to environmental changes” DO 16 WORK

Receptors:These are highly specialised cells found throughout the body. They are responsible for detecting stimuli or change.

Stimulus ReceptorLight PhotoreceptorsTemperature ThermoreceptorsTouch, movement and vibration MechanoreceptorsChemical Concentrations ChemoreceptorsReceptor cells also convert the stimulus in formation into electrochemical impulses that the nerve cells and brain can understand and interpret.

Nerve cells or neurones:These cells carry the information, in the form of impulses, to and from the central nervous system.

Central Nervous System:The brain receives information regarding any change and formulates an appropriate response.

DP7 “identify the broad range of temperatures over which life is found compared with the narrow limits for individual species”

Habitats that offer temperature conditions that are fairly stable and those that fall within a relatively narrow range are highly sought after and result in much competition. Most living things live at a temperature between 10 and 35 degrees Celsius. Active growth in most plants occurs between 5 and 40 degrees Celsius.

The diverse number of living things on Earth are found across a broad range of temperatures. Some can survive in temperatures as low as -70 Celsius, others as high as 56 Celsius in deserts and 350 Celsius in Thermal vents. However, individual species cannot survive in this large temperature range, they need narrower ranges.

Species have an optimal range of temperatures at which they can function. The temperatures range in which they can survive is termed its tolerance range. The tolerance range for the platypus is -8 to 34, the Sydney blue gum is -1 to 34.

Endotherms – These organisms are able to maintain a constant, stable internal body temperature.

Ectotherms – These organisms are able to change their internal temperature in relation to the external or ambient temperature.

Methods of mammalian temperature regulation:Observation Type of Adaptation

(structural, behavioural, physiological)

Explanation(how it relates to temperature regulation)

An echidna living in cold regions hibernates during the winter.

Behavioural They will move where it is cold so their body temperature will drop and they can hibernate.

Your skin often looks flushed on a hot day.

Physiological The body does this to regulate heat temperature.

Many Australian marsupials salivate and lick their fur on a hot day.

Behavioural They choose to lick their fur because they want their body temperature to lower.

Whales have a thick layer of blubber or fat under their skin.

Structural The whales are born with a thick layer of blubber.

You tend to feel cooler on a hot dry day than on a humid day of temperature.

Physiological Your body functions better without humidity.

A small mammal, with the same body temperature and insulating mechanisms as a larger mammal, loses more heat than a larger mammal.

Structural Their smaller body size prevents them from insulating the heat, even though it is the same principle as the larger mammal.

DP8 “compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation”Animal Environment Adaptations for heat control

Structural Behavioural PhysiologicalThorny Devil Desert Flattened

body to increase surface area of available sunlight.

Lays in the warm sand with its body flattened. It remains motionless

Absorbs water through skin.

Mitchell’s Hopping Mouse

Desert - Sweat Glands

- Fur

Is active from the late afternoon to the early morning

Fluffs up fur.

Corroboree Frog

Alpine Wet, slimy skin

It is only active on warm days in summer. It basks in the sun during the morning to warm

It feeds on small insects and other arthropods to accumulate fat tissue

up. for winter.Mountain Pigmy Possum

Alpine Thick fur and a round stocky body.

When hibernating during winter it rolls itself up into a furry ball, tucking its nose, ears, tail and feet into its body. It also slows down its metabolic rate.

It doubles its body weight through spring, summer and autumn to double its body weight so it can survive hibernation in winter.

DP9 “identify some responses of plants to temperature change” Plant response to high temperature:

o Evaporative cooling (transpiration), exposure to heat (and light) causes the stomata in plants to open, leading to a loss of water by transpiration (evaporation of water from the stomata of leaves). The advantage of this water loss is that it decreases the internal temperature in plants by evaporating cooling. However, the plants run the risk of dehydration due to water loss and so excessive heat in plants will cause stomata to close. This poses the threat of overheating. Plants have developed adaptations to cope with this.

o Turgor response – wilting some plants respond with changes in turgor pressure, which allows them to reduce the exposure of their surface area to the sun and its associated heat and light, for example a wilting response. In extreme heat, plants transpire and lost turgor in the palisade cells of leaves, as a result the leaves wilt, reducing the surface area that is exposed to the sun.

o Leaf orientation – to overcome the problems of overheating and excessive water loss, some plant for example eucalypts are able to change the concentration of their leaves so that they hang vertically downwards in hot weather. This reduced the surface area that is exposed to the sun during the heat of the noonday sun. The flat part of the leaf blade, with its large surface area, is exposed to the less intense rays of the early morning and late afternoon sun, but in the middle of the day when the sun is at its hottest, the sun’s rays strike the thin edge neat the leaf stalk of the vertical leaves.

o Leaf fall – many trees lose their leaves during the cold winter months, but eucalypts are evergreen trees that drop some of their leaves during the dry season in hot climates to reduce the surface area exposed to absorb heat. This also reduces the risk of loosing too much water by transpiration.

o Reseeding and resprouting (germination) in response to extreme high temperatures – fire:In Australia, one of the extreme temperature changes plants have to respond to is caused by bushfires. Plants have two general responses that ensure their survival after the fire – they may resprout or release seeds. Resprouters, such as the bottle brush, tea trees and eucalypts.

o Plants have several responses to cold temperatures: Organic ‘anti-freeze’

Dormancy – in response to cold temperatures, deciduous trees (those who drop their leaves annually) 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 the water shortages and lower availability of sunlight. For example, the deciduous beech (Nothofagus gunnii), found in Tasmania, is the only indigenous Australian deciduous tree.

Vernalisation – some plants flower in response to low temperatures; for example, tulip bulbs must be exposed to between 6 weeks and 3 months of intense cold before they will flower.

SC2 DP1 “identify data sources, plan, choose , equipment or resources and perform a first-hand investigation to test the effect of:”

Procedures to investigate the activity of an enzyme:A. To demonstrate the effect of increased temperature:

1. Make a rennin solution by dissolving a junket tablet in distilled water.2. Add the same amount of rennin solution to a number of test tubes of milk,

eg 7 test tubes.3. Place test tubes in different water baths at temperature ranges such as 0oC,

10oC, 20oC, 30oC, 40oC, 50oC and 60oC. Make sure each water bath is kept at the temperature it has been allocated.

4. Time the interval between adding the rennin and curdling of the milk for each temperature.

5. Note that the variables kept constant in each test tube are the junket solution, the pH of the solution, the type of milk and the quantity of milk in each test tube.

6. Comment on which temperature is the most effective in curdling the milk. Could a different temperature be better?

B. To demonstrate the effect of change in pH:1. Make a rennin solution the same as was done in A and add pH solution to

each with known concentrations of pH solutions from for example pH 3, pH 4, pH 5, pH 6, pH 7 and pH 8.

2. Add the same amount of rennin solution with the varying pH to six test tubes of milk.

3. Place in a water bath kept at a constant temperature of 37oC.4. Time the interval between adding the rennin and curdling of the milk in

each test tube.5. Note that the variables kept constant in each test tube are the junket

solution, the type of milk, the temperature of 37oC, and the quantity of milk in each test tube.

6. Comment on which pH is the most effective in curdling the milk.C. To demonstrate the effect of change in substrate concentration:

1. Make different concentrations of the substrate by diluting the milk using different amounts of powdered milk to get different concentrations.

2. Add the same amount of rennin solution to each test tube of milk.3. Place in a water bath kept at a constant temperature of 37oC.4. Time the interval between adding the rennin and curdling of the milk.

5. Note that the variables kept constant in each test tube are the type of milk, the temperature of 37oC, and the quantity of milk in each test tube.

6. Should smaller increments of milk concentrations have been used?

SC2 DP2 “gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism”Background:The body has some effective mechanisms to alter body temperature. To reduce temperature, heat can be expelled by sweating or radiation of heat from the skin. To increase heat, the body can respond by shivering or by contracting the skin. These responses can be activated by heat receptors. If a mechanism is activated, it will operate until receptors indicate that the optimum temperature has been reached.If receptors in the skin detect heat, they relay information via the nerves to the hypothalamus, which also contains receptors sensitive to the heat of passing blood. This triggers the sympathetic nervous system to dilate skin capillaries and activate sweat glands. When receptors in the skin detect a low temperature, a negative feedback mechanism is activated to stop the original action. If skin temperature is still low, the hypothalamus may activate thyroid hormones to increase metabolic rate, activate the sympathetic nervous system to shut down skin capillaries and sweat glands and activate food metabolism in the liver to produce heat. In this way, the body can maintain a stable body temperature.

Gather samples of feedback mechanisms from biology texts, from scientific journals or from the Internet. Often, analogies, such as the operation of a thermostat in a refrigerator or an air conditioning system, are used.

Process the samples to identify the common elements of each system. Evaluate the validity of your sources by checking the reputation of the sources and by looking to see how consistently the information compares.

Analyse and use the information to design a creative model to represent a feedback mechanism. The model might be a physical model, e.g. may be based on a see-saw action, or it might be a conceptual model, based on an analogy.

SC2 DP3 “analyse information from secondary sources to describe adaptations and responses that have occurred in Australian organisms to assist temperature regulation”Background:Endotherms derive most of their body heat from cell metabolism. Mammals and birds are endothermic animals. Australian endotherms include: the kangaroos and the platypus (temperate regions); the rabbit-eared bandicoot (desert dweller); and the alpine pygmy possum (alpine dweller)Ectotherms derive most of their body heat from their surroundings. All invertebrates and fish, reptiles and amphibians are ectothermic. Australian ectotherms include the blue-tongued lizard, the green tree frog and barramundi.

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

DP1 “identify the form(s) in which each of the following is carried in mammalian blood:”

Carbon Dioxide o Carbaminohaemoglobin o Red blood cellso Carbon dioxideo Dissolved in plasmao Hydrogen carbonate ionso Plasma

Oxygen o The form that oxygen is attached to is called oxyhaemoglobin

which is contained in the red blood cells. Water

o It transported through blood plasma and water molecules. Salts

o Ions o Dissolved in plasma

Lipids o Fatty acids and glycerolo Plasma

Nitrogenous Waste o Ureao Plasma

Other Products Of Digestion o Sugaro Glucoseo Plasmao Proteinso Amino acidso Vitamins

DP2 “explain the adaptive advantage of haemoglobin:” The red colour of the blood is due to the presence of a protein molecule

called haemoglobin, which is made up of four long amino acid chains, each assembled around an atom of iron.

Haemoglobin has a strong affinity for (great ability to pick up) oxygen when it is in higher concentrations that it is in the blood. This happens at the lungs. Haemoglobin can also release oxygen when it is in lower concentration than it is in the blood and this is why it is dropped off at body cells.

When haemoglobin picks up oxygen it becomes bright red, but changes back to purple once it has given it up. Oxygen chemically combines with haemoglobin to form oxyhaemoglobin. Each haemoglobin molecule combines with four molecules of oxygen. When all four binding sites are carrying oxygen, the oxygen saturation is said to be 100%.

Because it is released at the tissues, the haemoglobin can be used over and over again. The shape of the haemoglobin molecule changes slightly each time it binds to an oxygen molecule. The attachment of the first molecule makes the second easier and so on.

There are approximately 280 million haemoglobin molecules in each red blood cell.

DP3 “compare the structure of arteries, capillaries and veins in relation to their function”

Arteries carry blood away from the heart under high pressure and so must have a structure that can withstand the pressure. They have thick, but elastic walls, made up of three tissue layers: endothelium as a lining, smooth muscle to contract the vessel and connective tissue to allow for expansion. Arteries do not pump blood.

Veins carry blood back toward the heart. They carry the same quantity of blood as the arteries but not at the same high pressures. Veins have the same three layers as the arteries: endothelium, smooth muscle and connective tissue. However, the layers are not as thick. The veins also contain valves that prevent the backflow of blood.

Capillaries have walls that are only one endothelium cell thick, as they have to allow diffusion of materials through their wall to reach the cells found in the tissues in which the capillary is located.

DP4 “describe the main changes in the chemical composition of the blood as it moves around the body and identify tissues in which these changes occur”

Tissue Chemical Change Why the change occurs?Lungs - Increase in oxygen

- Decrease in carbon dioxide

- Needed by cells for respiration-Removal of waste (carbon dioxide has to be removed from the body)

Liver - Increase in nitrogenous waste (urea)- Increase or decrease in glucose (the liver can store or insert glucose into the blood)

- Deamination (breakdown) of amino acids- Change blood sugar level

Small Intestine - Increase in dissolved minerals, glucose, vitamins, protein (amino acids) as being absorbed

- Broken down and absorbed by the small intestine

Kidney - Decrease in urea- Decrease in water

- Urea is toxic- Filtration

Body Cells - Decrease in oxygen (when blood gives away- Decrease in glucose (when blood gives away)- Increase in CO2

Respiration

All tissues have a small decrease in oxygen because of respiration and in turn a small increase of carbon dioxide. Also all tissues use glucose to respirate.

DP5 “outline the need for oxygen in living cells and explain why removal of carbon dioxide from cells is essential”

Cells require oxygen in the process of respiration: Glucose + oxygen Right arrow 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, (after excess removal of carbon dioxide) the carbon dioxide - bicarbonate ion (HCO3-) equilibrium is an important mechanism for buffering the blood to maintain a constant pH.

DP6 “describe current theories about processes responsible for the movement of materials through plants in xylem and phloem tissue”

The transpiration stream in xylem occurs due to physical forces that result from water and ions being moved by passive transport. A column of water is sucked up the stream by the evaporative pull of transpiration and is known as transpiration water mineral ions) are carried by xylem tissue from the roots (the site of absorption) up to the leaves where they will be used for the manufacture of food (photosynthesis).

Most photosynthesis in plants occurs in the leaves. Phloem vessels are involved in the transport of organic nutrient products (particularly sugars, amino acids and plant hormones) to all parts of the plant. Movement occurs in two directions – up towards the flowers and down the roots.

The transpiration stream in xylem occurs due to physical forces that result from water (and ions) being moved by passive transport. A column of water is sucked up the stem by the evaporative pull of transpiration and is known as the transpiration stream.

Chemical substances that are needed for photosynthesis (such as water mineral ions) are carried by xylem tissue from the roots (the site of absorption) up to the leaves where they will be used for the manufacture of food (photosynthesis). Xylem tissue consists of xylem vessels, tracheids, fibres and parenchyma cells.

SC DP1 “perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water”

Perform your investigation, making sure you take readings of the initial pH of the distilled water.

Basic procedure:Using a data logger with a pH probe, take readings of the change in pH of 100 mL of distilled water as exhaled air is bubbled through it over a two-minute period. This experiment can also be performed using universal indicator paper and an indicator colour chart to estimate the pH at various stages of the experiment.SC DP2 “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”

SC DP3 “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”One method used by hospitals to monitor blood oxygen and carbon dioxide levels in patient's blood is to use a pulse oximeter. A small clip with a sensor is attached to the person's finger, earlobe or toe. A cable connects the sensor to the pulse oximeter machine. The colour of the blood changes according to the amount of oxygen that is dissolved in the blood. Blood that is high in oxygen is bright red while blood low in oxygen is a darker colour. The sensor emits a light signal that passes through the skin. The sensor measures the amount of light absorbed as it passes through the tissue and blood, and transmits the information to the pulse oximeter. A reading is given in a percentage form.

Pulse oximetry is used to monitor the level of oxygen in a person's blood during heavy sedation or anesthesia. This device is also used when a person is on a ventilator, artificial breathing machine, during stress testing, in sleep laboratories, when checking the body's response to different medications or to monitor a person with asthma or who is having trouble breathing.

Another method of analysing blood gases is with arterial blood gas (ABG) analysis machines. These can measure the amount of oxygen and carbon dioxide in a sample of blood by monitoring the rate of diffusion of these gases through artificial membranes which are permeable to these gases. When moving through a membrane, oxygen in the blood produces an electrical current while carbon dioxide changes the pH of the solution.SC DP4 “analyse information from secondary sources to identify the products extracted from donated blood and discuss the uses of these products”Background:When blood is donated, it can be used almost immediately as whole blood or it can be separated into its components. Whole blood is given to patients where major functions of the blood, such as oxygen carrying capacity, are impaired, or where more than 20% of blood has been lost and there is a decrease in blood pressure.Some blood products:

Red blood cells (RBCs)o RBCs help patients who need to be able to carry more oxygen.

RBCs may also be used to help replace cells lost following significant bleeding.

Platelet concentrateo Platelets are essential for the coagulation of blood and are used to

treat bleeding caused by conditions or diseases where the platelets are not functioning properly.

Fresh frozen plasma (FFP)o FFP is used mainly to provide blood components that coagulate the

blood. FFP contains all coagulation factors in normal amounts and is free of red cells, white blood cells and platelets. It is used for

patients who require immediate clotting effects, such as those undergoing warfarin therapy (blood thinning) or when massive transfusions have taken place.

Cryoprecipitate anti-haemophilic factoro Cryoprecipitate AHF is a concentrate of clotting proteins and is

used for the treatment of von Willebrand disease (similar to haemophilia), replacement of the clotting proteins, fibrinogen, Factor XIII and Factor VIII when no other option is successful.

SC DP5 “analyse and present information from secondary sources to report on progress in the production of artificial blood and use available evidence to propose reasons why such research is needed”Background:Blood transfusions have been the subject of medical research for centuries. In the early 1900s, successful transfusions were carried out as an understanding of blood components were understood. Up until the HIV crisis in the 1980s, there was little interest in artificial blood as there did not seem a great need. With the transmission of the virus during transfusions, there was nothing to replace donor blood, so artificial blood became a priority for research. Sensitive screening tests have now been developed for potential infective organisms, such as HIV and hepatitis, making donor blood much safer. There are now available safe and effective blood substitutes for certain applications, although they are still not ready for widespread use. Better blood substitutes are still needed. There is a continuing shortage of donor blood to help the victims of emergencies, civil and international conflicts and natural disasters. Furthermore, there is no guarantee that something similar to the HIV crisis will not occur in the future.

Why research on artificial blood is neededSome advantages of artificial blood could include the following:

Pasteurisation could be used to remove all pathogens. There would be no need for cross-matching and typing as the artificial

blood contains no blood-group antigens. This saves time and allows on-the-spot transfusion.

Artificial blood can be stored for more than one year, compared with about one month for donor blood using standard methods.

SC DP6 “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”Background:Xylem transports water and mineral ions upward only, from roots toward leaves. Phloem transports organic materials, in particular sugars, up and down to where the material is needed or for storage.

Xylem: The transpiration-cohesion-tension mechanism is currently the theory that accounts for the ascent of xylem sap. This sap is mainly pulled by transpiration rather than pushed by root pressure. Cohesion is the “sticking” together of water molecules so that they form a continuous stream of molecules extending from the leaves down to the roots. Water molecules also adhere to the cellulose molecules in the walls of the xylem. As water molecules are removed by transpiration in the leaf, the next

molecule moves upwards to take its place, pulling the stream of molecules continuously along. This is passive transport.

Phloem: The pressure-flow mechanism (or Source to Sink) is a model for phloem transport now widely accepted.The model has the following steps:

1. Step 1: Sugar is loaded into the phloem tube from the sugar source, e.g. the leaf (active transport)

2. Step 2: Water enters by osmosis due to a high solute concentration in the phloem tube. Water pressure is now raised at this end of the tube.

3. Step 3: At the sugar sink, where sugar is taken to be used or stored, it leaves the phloem tube. Water follows the sugar, leaving by osmosis and thus the water pressure in the tube drops.

The building up of pressure at the source end, and the reduction of pressure at the sink end, causes water to flow from source to sink. As sugar is dissolved in the water, it flows at the same rate as the water. Sieve tubes between phloem cells allow the movement of the phloem sap to continue relatively unimpeded.

3. Plants and animals regulate the concentration of gases, water and waste products of metabolism in cells and in interstitial fluid

DP1 “explain why the concentration of water in cells should be maintained within a narrow range for optimal function”

The concentration of water in the cells of the body should be maintained within a narrow range because it is essential to have water in your body so you can homeostaticly function. These include having enough water to transport substances around your body because water can act like a solvent, the right mix is essential to produce lubricating fluids such as mucous which is in your nose and stomach to help protect the body from unwanted substances. Water is also used for heat control and a watery substance surrounds the brain and protects it from colliding with the skull. Without the right concentrations of water none of this would be possible.

Solvent – transport substances Lubricating fluids – mucous Heat – not being able to control temperature Cushioning – water based liquid in the brain

DP2 “explain why the removal of wastes is essential for continued metabolic activity”

It is essential to remove wastes such as carbon dioxide and nitrogenous wastes from the body because it can affect metabolic activity, if they are left in the body for a prolonged period of time the pH of the cells would increase to an extent where the blood would become to acidic and damage cells.

DP3 “identify the role of the kidney in the excretory system of fish and mammals”

The kidney is an organ of the excretory system of both fish and mammals. It plays a central role in homeostasis, forming and excreting urine while regulating water and salt concentration in the blood. It maintains the precise balance between waste disposal and the animal's needs for water and salt.

The role of the kidney in fish is dependant on the environment of the fish:o In marine (salt water) environments, the kidneys excrete small

quantities of isotonic (same concentration as sea water) urine. This helps conserve water and excrete the excess salt they gain from their hyperosmotic environment.

o In freshwater fish, the kidneys work continuously to excrete copious quantities of dilute urine, which also has a very low salt concentration. This helps to remove excess water gained from the hypo-osmotic environment.

Excretion – This is the removal of metabolic waste. The kidneys remove nitrogenous wastes in the form of ammonia, urea, or uric acid.

Osmoregulation – This is the regulation of balanced water concentrations within the body.

DP4 “explain why the processes of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes”

Diffusion and osmosis are both examples of passive transport, relying on random movements of molecules. Diffusion is too slow for the normal functioning of the body and does not select for useful solutes. Osmosis only deals with the movement of water and thus would only allow water to move out of the body, not the nitrogenous wastes.

DP5 “distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney”

Active transport involves an expenditure of energy on the part of the organism, usually because the substance is moving against the concentration gradient, i.e. when a salt moves to an area of high salt concentration from an area of low salt concentration. Passive transport involves no expenditure of energy as the materials follow the natural concentration gradient, i.e. movement from an area of high concentration to an area of low concentration. Both diffusion and osmosis are examples of passive transport.

In the mammalian kidney, both active and passive transport processes occur.

o Passive transport: Once filtration has occurred in Bowman's capsule, water returns via the interstitial fluid from the tubule to the capillary in the process of osmosis. This occurs along the length of the tubule.

o Active transport: Depending on their concentration, the ions in the blood (Na+, K+, Cl- , H+ and HCO3) can be transported to cells in the nephron tubule and then secreted by the cells into the tubule. Some poisons and certain drugs are eliminated from the body in this manner.

DP6 “explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition”

Filtration of the blood occurs in Bowman's capsule where high blood pressure in the glomerulus forces all small molecules out of the blood into the capsule. Water, urea, ions (Na+, K+, Cl- , Ca2+, HCO3- ), glucose, amino acids and vitamins are all small enough to be moved into the glomerular filtrate. Blood cells and proteins are too large to be removed. This filtering process is non-selective and therefore many valuable components of the blood must be recovered by reabsorption.

Reabsorption takes place selectively at various points along the proximal tubule, loop of Henle and distal tubule.

All glucose molecules, amino acids and most vitamins are recovered, although the kidneys do not regulate their concentrations. The reabsorption of the ions Na+, K+, Cl- , Ca2+ and HCO3- occurs at different rates depending on feedback from the body. In some cases, active transport is required. Water is reabsorbed in all parts of the tubule except the ascending loop of Henle. The amount of water reabsorbed depends on feedback from the hypothalamus. If no water were reabsorbed human would soon dehydrate, losing water at a rate of around 7.5 L per hour.

The chemical composition of the body fluids is precisely regulated by the control of solute reabsorption from the glomerular filtrate.

The Nephron:

DP7 “outline the role of the hormones, aldosterone and ADH (anti-diuretic hormone), in the regulation of water and salt levels in blood”

Aldosterone is a steroid hormone secreted by the adrenal gland. Its function is to regulate the transfer of sodium and potassium ions in the kidney. When sodium levels are low, aldosterone is released into the blood causing more sodium to pass from the nephron to the blood. Water then flows from the nephron into the blood by osmosis. This results in the homeostatic balance of blood pressure.

Antidiuretic hormone (ADH or vasopressin) controls water reabsorption in the nephron. When levels of fluid in the blood drop, the hypothalamus causes the pituitary to release ADH. This increases the permeability of the collecting ducts to water, allowing more water to be absorbed from the urine into the blood. The resulting urine is more concentrated. When there is too much fluid in the blood, sensors in the heart cause the hypothalamus to reduce the production of ADH in the pituitary, decreasing the amount of water reabsorbed in the kidney. This results in a lower blood volume and larger quantities of more dilute urine.

DP8 “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

DP9 “describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss”

Plant and feature Diagram How feature minimises water loss

EucalyptsLeaves hang Vertically

If the leaves hang vertically they are reducing how much sunlight they receive therefore water will evaporate from the plant.

Spinifex grassLeaf can coil around underside

The grass leafs curl around leaving the stomates on the underside in turn reducing water loss.

Hakea multilineata (grass-leaf hakea)Leaves are long, thin Blades

They are long and thin reducing the surface area in the sun there reducing the rate of evaporation.

Carpobrotus rossii (pigface)Leaves are thick, succulent

Water will store water in the leaf and it takes longer to evaporate because it is thicker.

Actinotus spp (flannel flower)Leaves have dense covering of pale woolly hairs

The hairs on the leaf trap water, and as long as there is water on the top of the leaf the plant doesn’t have to evaporate any of it’s own water, so this is it’s water conservation technique.

Acacia sppHave extensive rootsystem with rootnodules

Collects water in a larger area and greater rate of osmosis to cool nodules.

OleanderDeep root system below the water table

Gets water at a lower level where other plants cannot get to.

SC DP1 “perform a first-hand investigation of the structure of a mammalian kidney by dissection, use of a model or visual resource and identify the regions involved in the excretion of waste products”

SC DP2 “gather, process and analyse information from secondary sources to compare the process of renal dialysis with the function of the kidney”Dialysis means separation in Greek, and, like the nephrons of the kidney, the dialysis machine separates molecules from the blood removing some and returning others. The patient's blood is pumped from an artery through tubes made of selectively permeable membrane. The artificial tubing allows only water and small solute molecules to pass through it into a dialysing solution that surrounds the tube. This dialysing solution is similar to the interstitial fluid found around nephrons. As the blood circulates through the dialysis tubing, urea and excess salts diffuse out of it instead of leaving by pressure filtration, as in the nephron. Those substances needed by the body, such as bicarbonate ions (HCO3

-) diffuse from the dialysing solution into the blood (reabsorption). The machine continually discards used dialysing solution as wastes build up in it.

Two healthy kidneys filter the blood volume about once every half-hour. Dialysis is a much slower and less efficient process than the natural processes found in a healthy kidney but it is a lifesaver for those people with damaged kidneys.

SC DP3 “present information to outline the general use of hormone replacement therapy in people who cannot secrete aldosterone”Hypoaldosteronism is a condition where people fail to secrete aldosterone. Addison's disease is the name of a disease with these symptoms which include high urine output with a resulting low blood volume. Eventually, as blood pressure falls, this can result in heart failure. A replacement hormone, fludrocortisone (Florinef), is used to treat this condition but a careful monitoring must be maintained to avoid fluid retention and high blood pressure.

SC DP4 “analyse information from secondary sources to compare and explain the differences in urine concentration of terrestrial mammals, marine fish and freshwater fish”

Terrestrial mammalsTerrestrial mammals must work to find water and they are surrounded by air into which water quickly evaporates. Water conservation is of prime concern and these animals cannot afford to excrete large quantities of water in the removal of metabolic waste.

Marine fishThe loss of water to the external environment is a problem that all marine fish must deal with. The marine environment in which the fish lives is hyperosmotic to the internal environment, i.e. there is a higher salt concentration in the water than inside the cells. This results in an osmotic gradient in which water is lost from the fish to the environment while ions are gained by diffusion. Ions are excreted by specialised glands.

Freshwater fishThe freshwater environment is hypo-osmotic to the internal environment of fish, i.e. there is a lower salt concentration in the water than inside the cells. This results in an osmotic gradient in which water is gained by the fish from the environment without drinking and salts are lost by diffusion. Ions are absorbed in the gut and by active uptake across the gills.

SC DP5 “use available evidence to 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 mammals”

SC DP6 “process and analyse information from secondary sources and use available evidence to discuss processes used by different plants for salt regulation in saline environments”

Coping with salt:Most plants cannot tolerate high salt concentrations in the root zone as it leads to water stress. The salt accumulates in the leaves and is toxic. Enzymes are inhibited by Na+ ions. Halophytes are plants that can tolerate higher levels of salt in their environment.

The grey mangrove, Avicennia marina, has special salt glands in its leaves that excrete salt. Other mangroves exclude salts at their roots through ultrafiltration and a third mechanism is to store salt in leaves and then drop the leaves.

Another mechanism involves the efficient control of transpiration. Some mangroves have small leaves hanging vertically to reduce the surface presented to the sun and thus reducing transpiration.

Salt marsh plants also have mechanisms for salt regulation. For example, Sarcocornia quinqueflora accumulates salt in the swollen leaf bases which fall off, thus removing excess salt and Sporobolus virginicus has salt glands on its leaves.

Another form of salt stress can occur in salt laden air such as in coastal environments. Some coastal plants, such as the Norfolk Island pine, have a mesh of cuticle over their stomates, which prevents small water droplets from entering the leaf.

SC DP7 “perform a first-hand investigation to gather information about structures in plants that assist in the conservation of water”