Biology:Maintaining a Balance
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Most organisms are active in a limited temperature range
Students learn to:
Identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates
- There are a large number of metabolic processes occurring in all living organisms, most of which would not occur at an efficient rate without enzymes. An efficient rate of metabolism is necessary for life processes to continue. Without enzymes, metabolism would be so slow at body temperature that insufficient energy would be available to maintain life.
- Enzymes are biological catalysts, and serve the purpose of making it possible for biological reactions to occur at the required rate by lowering the activation energy of the reactions.
- Enzymes are globular proteins – shapes are specialized so that other chemicals (substrates) can form temporary bonds with them.
They are made up of amino acids linked forming a polypeptide chain called a protein, which is folder in specific ways to produce a 3D protein structure that has specific active site.
- The most common model to explain enzyme specificity is the lock and key model. At a molecular level, the shape of an enzyme permits it to bind at a particular site (active site) to the substrate molecules, causing a reaction to occur. This can be thought of as a key (the substrates) fitting a lock (the enzyme). Unless a key is right for a particular lock it doesn’t work. Enzymes are specific because they will only fit particular substrates.
Diagram originally from hsc.csu.edu.au
- A modified version of the lock and key model known as the induced fit model posits that the active site shifts slightly to accomodate the substrate like a clasping handshake.
Diagram originally from hsc.csu.edu.au
- Further information on enzymes can be found at these sites:
Identify the pH as a way of describing the acidity of a substance
- The pH scale is a way of describing the acidity of a substance. A pH of less than 7 indicates that a substance is acidic, a pH equal to 7 indicates that a substance is neutral, and a pH of greater than 7 indicates that a substance is basic.[Further information is available here]
Explain why the maintenance of a stable internal environment is important for optimal metabolic efficiency
- Most metabolic reactions are governed by enzymes. Enzymes can only act within a limited temperature and pH range. If the temperature is too high then the enzyme’s shape will be permanently altered (denatured), rendering it useless for catalysing reactions. If the pH is outside the enzyme’s optimum range it will not act efficiently, if pH is too extreme then then enzymes will be denatured. If the enzymes are not working properly then reactions cannot be maintained at a stable rate then metabolic efficiency cannot be maintained.[Further information may be found here]
Describe homeostasis as the process by which organisms maintain a relatively stable internal environment
- Homeostasis is the process by which organisms maintain a stable internal environment by means of physiological or behavioral feedback responses . It is concerned with keeping aspects such as temperature, pH and substrate concentration constant in order to maintain the optimal metabolic conditions for organisms.[Further information on homeostasis may be found here and here]
Explain that homeostasis consists of two stages:
- detecting changes from the stable state
- counteracting changes from the stable state
- A receptor detects the change in the organism’s internal environment. For example heat receptors in the skin detect a change in temperature. An appropriate response occurs which counteracts the change. For example sweat glands in the skin will perspire to reduce the temperature.
Outline the role of the nervous system in detecting and responding to environmental changes
- When the receptor detects a change from the stable state it sends a nervous impulse to the control centre (eg hypothalamus). The control centre, which is often part of the central nervous system then decides on the appropriate response and sends more nervous impulses to the effector, which counteracts the change.
Identify the broad range of temperatures over which life is found compared with the narrow limits for specific species
- Life on Earth can exist over a broad range of temperatures, from around 0°C (bacteria living in Antarctica) to 100°C (bacteria living near underwater thermal vents). Individual species, however, have much narrower temperature bands within which they can survive (eg humans can only survive unclothed and unsheltered from 27°C to 43°C).
Compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
- Endotherms are organisms that use their internal metabolism to generate heat.
- Bilby-Large ears increase surface area to volume ratio for greater loss of heat. Bilbies create deep burrows to escape the heat. They are nocturnal, and dilate the blood vessels in their ears when hot to increase heat loss (vasodilation).
- Potoroo-Nocturnal, lives in relatively thick ground vegetation. When hot Potoroos increase their breathing rate to cool themselves more quickly.
- Emu-Covering of feathers to help insulate and retain body heat when needed. Covering of feathers minimises heat absorption to prevent overheating.It can hold its wings away from its sides and maximise evaporation of sweat as well as losing heat from blood vessels.
- Red Kangaroo-Licks forearms where the blood vessels are arranged close to the surface(evaporative cooling), occasionally nocturnal.
- Ectotherms are organisms which rely on behavioural adaptations to regulate their internal temperature through their environment.
- Bearded Dragon-When the bearded dragon detects low light levels a message is sent from the eye to the pituitary gland which secretes the melanocyte hormone which darkens the skin pigments so the animal can absorb more heat. Thermoreceptors in the skin can detect too much heat and cause the pigments to retract so the skin is lightened and more light is reflected.
- Alpine Grasshopper-Most commonly found near Thredbo. Hibernates in winter, emerges in spring, mates in December. It produces a frothy substance around it's eggs to insulate them.
- Waterholding frog-The frog lives in an underground clay burrow which helps insulate against temperature changes. The frog lives in an underground clay burrow which helps insulate against temperature changes. In hot conditions the frog becomes dormant which reduces heat production because metabolic rate is reduced. Can extract water from the soil around it to prevent overheating.
- Brown snake-exposes large surface area to sun, seeks shade in burrows, use anaerobic respiration for muscular activity, flattened body to increase Surface Area to Volume ratio, increased blood flow to skin vessels.
- Further information on some Australian ectotherms and endotherms may be found here:
Identify some responses of plants to temperature change
- Plants have many physical and physiological adaptations to help them survive over a range of temperatures.
- The alpine groundsel is found in the Kosciuszko area of NSW and Victoria, where temperatures range between –10°C and 3°C throughout the year. Some of its adaptations are:
- Groundsel is short so that when it snows it is covered completely. This snow helps to insulate the plant from the cold, keeping its temperature at around 0°C.
- Leaves and stems desiccate during winter to reduce the risk of damage being caused to cells due to the water inside them freezing.
- A hairy layer on the stems and leaves helps prevent freezing and water loss.
- The mulga tree lives in dry areas. Some of its adaptations are:
- Its leaves have a thick silvery cuticle to reflect and insulate against heat.
- The shape of the tree means that any water falling on the plant runs down to the base of the tree to be absorbed by the roots. Adequate water is essential to prevent overheating.
- The alpine groundsel is found in the Kosciuszko area of NSW and Victoria, where temperatures range between –10°C and 3°C throughout the year. Some of its adaptations are:
Students:
Identify data sources, plan, choose equipment or resources and perform a first hand investigation to test the effect of:
- increased temperature
- change in pH
- change in substrate concentrations on the activity of named enzyme(s)
Part A
- Aim
To test the effect of a change in temperature on the action of catalase.
- Method
1. Five test tubes were set up with equal volumes 10% hydrogen peroxide solution and maintained at temperatures of 5°C, 20°C, 35°C, 50°C and 60°C, using hot water or ice baths as appropriate, and using thermometers to make sure the temperature was kept constant.
2. Equal sized pieces of liver (containing catalase) were added to each test tube. After 5 minutes the height of bubbles produced was measured with a ruler and recorded in a table.
- Results and Conclusion
| Temperature (°C) | Height of bubbles produced |
|---|---|
| 5 | none |
| 20 | low |
| 35 | high |
| 50 | none |
| 65 | none |
It can be concluded that the test tube at 5°C had insufficient energy to activate the reaction, in the test tubes at 50°C and 65°C the catalase was denatured, and that 35°C was the optimum temperature for catalase. It was ensured that equal volumes of solution were put in all the test tubes.
Part B
- Aim
To test the effect of a change in pH on the action of catalase.
- Hazard Assessment
If acids or bases get into your eyes they can cause damage. For this reason protective goggles were worn.
- Method
1. Six test tubes were set up with equal volumes of 10% hydrogen peroxide solution at pH’s of 1, 3, 5, 7, 9 and 11. The test tubes were then labelled with their pH.
2. Equal size pieces of liver (containing catalase) were added to each test tube, and the test tubes were maintained at a constant temperature of 35°C. After 5 minutes had passed the height of bubbles produced was measured with a ruler and recorded in a table.
- Results and Conclusion
| pH | Height of bubbles produced |
|---|---|
| 1 | none |
| 3 | low |
| 5 | high |
| 7 | high |
| 9 | low |
| 11 | none |
It can be reasonably concluded that the optimum pH is somewhere between 5 and 7.
Part C
- Aim
To determine the effect of substrate concentration on the action of catalase.
- Method
1. Six test tubes were set up containing equal volumes of hydroxide peroxide solution, with concentrations of 0%, 4%, 8%, 12%, 16% and 20%.
2. Equal sized pieces of liver (containing catalase) were added to each test tube, the test tubes were maintained at a constant temperature of 35°C. They were then left for 5 minutes and the height of bubbles produced was measured with a ruler and recorded in a table.
- Results and Conclusion
It was noted that as the concentration was increased further and further the increases in the height of bubbles became less and less significant. It can be concluded that this is because as more enzyme active sites get filled it is harder for the substrate to find an available active site.
Gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism
Analyse information from secondary sources to describe adaptations and responses that have occurred in Australian organisms to assist temperature regulation
- See earlier dotpoint on native enodotherms and ectotherms.
Plants and animals transport dissolved nutrients and gases in a fluid medium
Students learn to:
Identify the form(s) in which each of the following is carried in mammalian blood:
•carbon dioxide
- Carbon dioxide can be carried in the blood by (in order of commonality):
- entering red blood cells and forming HCO3 (bicarbonate) ions which then diffuse into the plasma.
- attaching itself to haemoglobin, forming carbaminohaemoglobin.
- by being dissolved directly into the plasma.
•oxygen
- Oxygen is mostly carried in red blood cells attached to haemoglobin, forming a compound called oxyhaemoglobin (HbO2). A small amount is also carried dissolved in the plasma.
•water
- Liquid H20 is the solvent making up 90% of the plasma.
•salts
- Salts are carried as dissolved ions in the plasma.
•lipids
- Lipids do not dissolve in water therefore they need to be carried with phospholids and cholesterol in protein coated packages called chylomicron.
•nitrogenous waste
- Nitrogenous wastes (urea, uric acid, creatinine) are dissolved in blood plasma.
•other products of digestion
- Other products of digestion (eg sugars, amino acids and vitamins) are carried in the plasma.
Explain the adaptive advantage of haemoglobin
- Haemoglobin is a complex protein (globin) containing 4 haem units. A haem unit contains iron, which can attach to an oxygen molecule, forming oxyhaemoglobin. Each red blood cell can contain 280 million haemoglobin molecules.Having haemoglobin is an adaptive advantage because it is such an effective transporter of oxygen. Oxygen is almost insoluble in H2O which is the main component of plasma and thus if oxygen was carried only in the plasma then body cells would not get enough oxygen and the organism would die.
Compare the structure of arteries, capillaries and veins in relation to their function
- Arteries- Thick walled, elastic, muscular. Take blood away from heart. Elastic fibres maintain blood pressure and send blood in spurts toward body tissues. Thick walls withstand the high pressure of the blood.
- Capillaries- Walls are one cell thick, capillaries have a small diameter. Thinness of capillary walls allow chemicals to diffuse in and out of blood. Capillary network creates a large surface area. They surround tissue cells so that no cell is very far from a capillary.
- Veins- The walls of veins are thinner than artery walls, have a larger diameter and are less muscular. Veins carry blood back to the heart after it has passed through the capillaries. The blood is under low pressure. It is kept moving by one way valves in the veins and by surrounding muscles pressing on the veins.
- Links to further information on blood vessels:
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
- As the blood flows around the body chemical changes occur particularly in the various capillary beds. In the mammalian body blood circulated around two main systems, the pulmonary (lungs) and systemic (rest of body) systems.
- The pulmonary circuit provides the flow of blood from the heart to the lungs and back again. Blood is under lower pressure than in the systemic system. The blood has just returned from the body and contains high CO2 and low O2 levels. It loses it's CO2 in the lungs and gains O2 and returns to the heart as bright red oxygenated blood.
- In the systemic system blood flows under high pressure out of the left ventricle and some fluid is forced out of the blood to become part of the body fluid. The oxygenated blood gives up it's O2 as it reaches the tissues. Any ions or nutrients required by cells also leave the blood and waste products of metabolism (urea, CO2) enter the blood. Blood flowing through the kidneys loses it's urea and has it's water and salt composition balanced. Blood flowing to intestines collects products of digestion, which are carried to the liver where the level of many circulating substances is controlled. The blood returns to the heart dark red in colour, through the veins.
Outline the need for oxygen in living cells and explain why removal of carbon dioxide from cells is essential
- Living cells need energy. The most efficient form of energy production is aerobic respiration. This requires oxygen.
Glucose + Oxygen -------> Carbon Dioxide + Water
- Carbon Dioxide is a waste product produced from aerobic respiration. Aerobic respiration is essential to produce the energy required for cell metabolism. For the cell to survive CO2 must be produced. However the production of CO2 will form carbonic acid and lower the pH. This will deactivate enzymes and slow metabolism in the cell. Therefore to survive the cell must remove CO2 from the body.
Describe current theories about processes responsible for the movement of materials through plants in xylem and phloem tissue
- The xylem uses passive transport and it only carries water upwards. The main forces acting on the water are:
- the force of transpiration sucking water up.
- cohesion which means that water molecules stick together in a chain.
- adhesion to the cellulose walls of the xylem.
- The phloem uses active transport to carry sugar and other nutrients around the plant. The name of the model used is the pressure flow mechanism. This model consists of six steps:
- Sugars are moved into the phloem cells by active transport.
- The increased sugar concentration makes water in these cells less concentrated than in surrounding cells.
- Water moves out from surrounding cells into the phloem by osmosis.
- More water increases the pressure in the phloem cells.
- Increased pressure causes the substances in the phloem cell to flow to another cell in the phloem tissue and so on, so that the substances gradually move through phloem tissue.
- Dissolved substances, especially sugars, are removed from phloem tissue at another location in the plant so that the flow mechanism can continue.
Students:
Perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water
- Aim
To demonstrate the effect of dissolved carbon dioxide on the pH of water.
- Method
- Some limewater was added to a test tube and air was blown into it through a straw. Any change to the appearance of the limewater was recorded in a table.
- Some water was added to a test tube and 3 drops of universal indicator was also added. Air was blown into it through a straw. Any colour change in the indicator was recorded in a table.
- Results and Conclusion
| Chemical | Colour change |
|---|---|
| Limewater | Colourless -->cloudy |
| Universal Indicator | Green --> yellow |
- The fact that the limewater went cloudy indicated that carbon dioxide was present.
- The fact that the universal indicator turned yellow indicates that the carbon dioxide turns water acidic.
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 observe red and white blood cells under a microscope and estimate their size.
- Method
- The microscope was set to a magnification of 100x, and a ruler was put in the field of view so that one of the lines was at one edge of the field. The size of the field was then approximated and this was recorded into a table.
- The microscope’s magnification was changed to 400x and a slide containing a smear of blood was put under it.
- The number of red blood cells across the radius was counted and this was doubled to produce the number across the diameter.
- The size of the white blood cells was approximated relative to the size of the red blood cells.
- Results and Conclusion
| Diameter at 100x | x |
| Number of RBC across at 400x | y |
| Size of WBC/size of RBC | Z(approx 1.5) |
- The diameter at 400x was determined to be x/4.
- The size of the RBC was determined to be x/4y. (approx 8um)
- The size of the WBC was determined to be zx/4y. (approx 12um)
- The experiment could be improved by using a microscope with a higher magnification or a ruler with smaller increments.
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
- An arterial blood gas analysis machine measures the concentrations of oxygen and carbon dioxide in a freshly-taken sample of blood. Carbon dioxide is detected because it changes the pH of a test solution, and the machine then detects the magnitude of this change in pH. Oxygen that diffuses out of the sample causes an electric current to flow- the magnitude of this current indicates how much oxygen is present. The arterial blood gas analysis machine is very accurate and can be useful to detect heart and lung disorders which would otherwise be very difficult to identify and prevent.[Further information on arterial blood gas analysis may be found here and here.]
- A pulse oximeter works by detecting changes in the colour of blood, because it is a brighter red when it is saturated with oxygen. It clips onto the finger and shines infrared light through the finger and a detector underneath collects the information about the colour of blood in the capillaries. It gives its readout as a percentage of oxygen saturation and is useful for to constantly monitor patients with heart or breathing problems.
- Further information on pulse oximetry can be found at the following sites:
- A capnometer is a newer, non-invasive device that measures the concentrations of respired gases using an infrared beam of light. It takes a reading of the amount of light absorbed which depends on the number of CO2 molecules present, taken from exhaled air. It is used when monitoring changes in CO2 concentrations in patients who are haemodynamically stable.[Further information can be found here.]
Analyse information from secondary sources to identify the products extracted from donated blood and discuss the uses of these products
- Donated blood is a vital and important thing to the world’s health care systems it keeps many people alive each year. While whole blood is used for some transfusions, several different things are often extracted to make its usage more effective and efficient. These are:
- Red blood cells are extracted and used in people who have problems with transporting oxygen, or to help replace blood cells following significant bleeding from trauma or surgery.
- Platelets can be extracted and are used to promote blood clotting and control bleeding. It is often used for leukaemia and bone marrow transplant patients.
- Stable protein plasma is used in emergencies before whole blood becomes available. It is also used in patients with burns, who tend to lose fluid rather than whole blood. Plasma is also further processed to make:
- Cryoprecipitate which contains blood clotting proteins. Used for liver transplant patients, and patients who have deficiencies of the blood clotting proteins.
- Cryosupernate which undergoes further processing to produce Anti D (prevents Rhesus in newborns), Immunoglobulin (carries antibodies against common infectious diseases) and Intragam (boosts immune system, used in treatment of some muscle and nerve disorders).
- Clotting factors can be used in people with severe bleeding problems, such as haemophilia.
- Immunoglobins are antibodies used in people with immune system problems, such as AIDS.
- Serum albumin is used in people with low plasma protein levels, such as those with liver disease.
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
- At present artificial blood cannot be made, blood can only be replaced with a dextrose solution, which is a mixture of glucose, salts and water. This solution is used to prevent a patient’s blood pressure from falling too low. It is feasible that haemoglobin may be able to be produced in large quantities by micro organisms.
- Reasons why research into artificial blood is important are as follows:
- There is not always enough donated blood to meet our needs, and only a limited number of people donate blood.
- There can be issues with compatibility of blood type with regular blood transfusion, and it takes time to determine the recipient’s blood type to complete a successful transfusion, artificial blood has no such problems.
- Donated blood may contain diseases (eg HIV), artificial blood does not.
- Donated blood has a limited shelf life of about a month, artificial blood can be stored for up to a year.
- Further information may be found here and here.
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 gather first-hand data in order to draw a longitudinal and transverse sections of phloem and xylem.
- Method
- A stick of celery (with leaves still on it) was left standing overnight in a beaker of water containing red food dye.
- Using a sharp razor blade very thin lengths were cut both across the stalk (for the transverse section) and down the length of the stalk (for the longitudinal section).
- One of each type of slice was prepared as a wet mount and put under a microscope. Diagrams were drawn of what was visible under the microscope.
- Results and Conclusion
The dye rose up the xylem, staining it strongly, while the phloem was left unstained, making it easy to tell them apart.
Plants and animals regulate the concentration of gases, water and waste products of metabolism in cells and in interstitial fluid
Students learn to:
Explain why the concentration of water in cells should be maintained within a narrow range for optimal function
- The concentration of water is critical for most organisms. It must remain constant for the following reasons:
- water maintains the shape of the cell membrane, too much water can cause the cell to burst and too little can cause it to shrivel up.
- changes in the concentration of water will usually be accompanied by changes in the concentration of solutes. The concentrations of these substances must be kept constant for optimal metabolic efficiency. For example a decrease in water concentration leads to an effective increase in carbon dioxide concentration, which decreases the pH, which hinders the functioning of enzymes.
Explain why the removal of wastes is essential for continued metabolic activity
- Wastes from metabolic processes can be toxic to cells. For example carbon dioxide (from respiration) can change the pH of cells and hinder the function of enzymes, and nitrogenous wastes (eg ammonia and urea) must be excreted or else they poison cells and change the pH of cells. Even the accumulation of non-toxic wastes can be dangerous because increased concentration of products can interfere with reaction rates.
Identify the role of the kidney in the excretory system of fish and mammals
- In fish and mammals the role of the kidney is twofold:
- To excrete all the body’s waste products apart from carbon dioxide, especially nitrogenous wastes in the form of urea dissolved in water (called urine).
- To maintain a balance between water and salts in the body by altering urine concentration.
Explain why the processes of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes
- Diffusion and osmosis are both examples of passive transport. Diffusion is insufficient for the body’s disposal of nitrogenous wastes because if diffusion was the only process used the urine concentration in the collecting tube could never be greater than that in the blood vessels running into it, so the urine would be too dilute and too much water would be lost. Osmosis can only move water so it is not useful for the excretion of nitrogenous wastes.
Distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney
- Active transport works against the concentration gradient and thus requires the use of energy.
- Passive transport(osmosis and diffusion) does not oppose the concentration gradient and thus does not require energy.
- In the mammalian kidney water reabsorption is a passive process. Reabsorption of sodium salts, glucose and amino acids is an active process. Non waste products are actively reabsorbed into the blood in the Loop of Henle.
Explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition
- Bowman’s Capsule: Plasma is forced out of the blood and into the nephron. This filtration leaves blood cells and other fragments in the vessel. Water, dissolved nutrients, other chemicals needed by the body and wastes are in high concentration in the nephron.
- Proximal tubule: All glucose, most nutrients and most water and salts move out of the nephron and back into the blood vessel. This is called reabsorption. Urea is not reabsorbed at all.
- Loop of Henle: The changing balance of salts on either side of the loop of Henle promotes movement through it.
- Distal tubule: Most remaining salts are reabsorbed if required to maintain the salt level in body fluids.
- Collecting duct: The amount of water reabsorbed here is dependent upon how much is required by the body.
- Filtration and reabsorption regulate body fluid composition by preventing the loss of useful substances and filtering out toxic ones.
Outline the role of the hormones, aldosterone and ADH (anti-diuretic hormone), in the regulation of water and salt levels in blood
- Osmoregulation occurs due to coordination by the endocrine system (hormones). Two hormones are involved in the regulation of the levels of salt and water in the body. These are anti-diuretic hormone (ADH, aka vasopressin) and aldosterone:
- Aldosterone is a steroid hormone produced and secreted by the adrenal glands which increases the reabsorption of sodium ions and decreases the reabsorption of potassium in the loop of Henle and the distal tubules. When sodium ions re-enter the blood water follows by osmosis and so blood pressure is increased. So aldosterones role is to conserve sodium ions and maintain blood pressure.
- ADH increases the permeability of the collecting duct and thus increases water reabsorption. It is produced by the hypothalamus and secreted by the posterior pituitary gland when fluid levels in the body drop too low. Thus it has control over the concentration of urine.
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
- Enantiostasis is the maintenance of metabolic and physiological functions in response to variations in the environment. An example of this is organisms living in estuaries where the water is constantly changing from saltwater to freshwater. Enantiostasis is important to these organisms because they live in an environment that constantly changes, and they need to be able to maintain biological functions.
Describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss
- Some adaptations in Australian plants to minimise water loss are:
- thick and waxy cuticles and sunken stomates on leaves, leaves hang down to minimise evaporation(e.g in eucalypts).
- hairy leaves or stems to restrict air flow and evaporation.(e.g on alpine groundsel)
- leaves that droop or roll to minimise exposure of the stomates.(e.g spinifex)
- small leaves, altered shapes to reduce surface area.(e.g salt brush)
- thick bark prevents water loss.
- colour of leaf, lighter/shiny colours reflect light thus preventing leaf from becoming as hot.
Students:
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
Aim
To dissect a mammalian kidney.
Hazard Assessment
The kidney may be carrying dangerous disease causing bacteria and as such gloves were worn. Scalpels can also be dangerous so care was taken when doing the dissection.
Method
1. The kidney was dissected as shown below:
Gather, process and analyse information from secondary sources to compare the process of renal dialysis with the function of the kidney
- In renal dialysis, blood is diverted out of an artery into a machine where it flows inside tubing through dialysis fluid. The fluid is made up of salts, glucose and dissolved gases and serves the purpose of drawing water and some wastes (particularly urea and excess salts) out of the blood, returning the cleaned blood to the body.
- Both renal dialysis and the kidney use semipermeable membranes.
| Renal Dialysis | Kidney |
|---|---|
| artificial tubing - filtering | nephrons - filtering |
| homeostasis doesn't take place, the diet needs to be supplemented | homeostasis |
| dialasing solutions - remove metabolic wastes by diffusion, can't be recycled, a lot needed | interstitial fluid - removes metabolic wastes, can be recycled |
| used dialyasing fluid becomes 'urine' | urine is formed |
| passive transport only | passive and active transport |
| about 15 hrs a week | works 24/7 |
| no bowman's capsule function (filtration at high pressure) | Bowman's capsule |
| anti-clotting agent added to blood | not required |
Present information to outline the general use of hormone replacement therapy in people who cannot secrete aldosterone
- The main substitute for aldosterone is fludrocortisone.
- Hormone replacement for kidney function usually involves several hormones.
- Addison’s disease is where the adrenal cortex produces insufficient hormones.
- Hormone replacement therapy can enable patients to manage symptoms (such as fluid retention and high blood pressure).
Analyse information from secondary sources to compare and explain the differences in urine concentration of terrestrial mammals, marine fish and freshwater fish
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
Process and analyse information from secondary sources and use available evidence to discuss processes used by different plants for salt regulation in saline environments
- The Grey Mangrove uses salt-excreting glands in its leaves. Also uses salt accumulation in leaves and limbs of the tree - when they become saturated with salt, the leaf or limb drops off.
Perform a first-hand investigation to gather information about structures in plants that assist in the conservation of water
- Aim
To gather information about features of plants which help minimise water loss.
- Method
- Leaves, stems and roots of various plants were examined for features which may aid in minimising water loss.
- Results and Conclusion
- Some features which were seen to minimise water loss were:
- hair on leaves and stem.
- few stomata on top of leaves.
- waxy leaf cuticle.
- leaves rolled inward (spinifex grass).
- leaves reduced to spikes (spinifex).
- the sexual organs of the flower are almost totally enclosed by the petals.
- Some features which were seen to minimise water loss were:
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