1. Most organisms are active in a limited temperature range

Identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substances

Metabolism refers to all the chemical reactions occurring within an organism.

Enzymes are protein molecules within cells that act as biological catalysts. Enzymes speed up chemical reactions and enable reactions to occur at lower temperatures within the body (increasing the efficiency of metabolic processes). They aren’t consumed in the process and can be reused.

Enzymes are globular proteins (shaped like a sphere). They are composed of one or more polypeptides (long chains of amino acids) that are folded into a 3D structure.

The molecule on which an enzyme acts upon is called a substrate. Enzymes are substrate specific, meaning that one enzyme can only work on one type of substrate. This can be illustrated through the lock and key model:

The enzyme fits together with its substrate molecule at a precise place of the much larger enzyme molecule, called the active site. The active site is shaped specifically to work on only one substrate.

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

pH is a scale related to the concentration of hydrogen ions in a solution. It is therefore a measure of the acidity of a substance (0 – most acidic; 14 – most basic)

Explain why the maintenance of a constant internal environment is important for optimal metabolic efficiency

Enzymes, which control all the metabolic processes of a body, work best in an environment where their optimum temperature and pH conditions are met. At other temperatures and pH values, enzymes fail to work at optimum efficiency. By keeping a constant internal environment, enzymes work effectively and metabolic efficiency is maintained.

Describe homeostasis as the process by which organisms maintain a relatively stable internal environment

Homeostasis is the process by which an organism maintains a constant internal environment, despite fluctuations that may arise in its external surroundings. It involves an enormous amount of co-ordination and control – involving both the nervous system and endocrine system (hormones)

Explain that homeostasis consists of two stages: detecting changes from the stable state, counteracting changes from the stable state

Homeostasis is brought about in two stages:

1. Detecting change - sensory cells or receptors detect change in the temperature/chemical composition within the body. This change in the environment is called a stimulus.

2. Counteracting change - effector organs (e.g. muscles/glands) then work to reverse the change. A response that successfully reverses the change will return the body to homeostasis – its relatively constant state

Overall, homeostasis ensures that variables in the internal environment of an organism are maintained within a narrow range.

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

The nervous system provides rapid coordination of internal organ systems, detecting and responding to environmental changes. It consists of the central nervous system (brain, spinal chord) and peripheral nerves.

The function of the nervous system takes place in three steps:

1. Detects information via receptors2. Transmits information to a control centre This is done by generating nerve impulses which

travel along sensory neurones to the CNS3. Information is processed by the CNS, generating a response through the generation of nerve

impulses sent along motor neurones to stimulate effector organs (muscles/glands)

Summary: receptors that detect change transmit messages that are processed within the central nervous system and messages are then conveyed to effector organs.

Identify the broad range of temperatures over which life is found compared with the narrow limits for individual species

There is a diverse range of species living on Earth, existing across temperatures ranging from under 0oC to over 100oC. However, no single organism can remain active and thriving under the full range of the temperatures on Earth; in fact, most organisms can only function in a relatively narrow temperature range.

Compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation

Ambient temperature refers to the external or environmental temperature.

Ectotherms are organisms that rely on external sources of heat

Endotherms are organisms that rely on internal sources, such as metabolic activity, for heat

Australian Red Kangaroo (endotherm)

Cold conditions Hot conditionsPhysiological:

o Increased metabolic rate to create more body heat

Behavioural:o Basking in the sun

Physiological:o Decreased metabolic rate

Behavioural:o Panting and sweating (releasing heat)o Licking forelimbs to increase heat loss by

evaporationStructural:

o Exposed areas of skin on forelegs to increase evaporative cooling of blood

Australian Diamond Python (ectotherm)

Cold conditions Hot conditionsPhysiological:

o Shivers to create more heat within bodyStructural:

o Dark colour to absorb heatBehavioural:

o Basks in suno Hibernation in wintero Migration to warmer areas

Behavioural:o Nocturnal – hunts a night and burrows

during the day to avoid higher daytime temperatures

Identify some responses of plants to temperature change

On land, where temperature fluctuations are greater than in water, plant responses can include:

The ability to orientate leaves vertically to reduce SA exposed to the sun (therefore reducing heat exposure and supporting convective cooling)

The ability to drop their leaves if temperatures become too cold Budding as the temperature and length of day increases in spring Closing stomates in response to high temperatures to reduce water loss

Gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism:

Homeostasis involves the detection of the change in the environment and the response to that change

The mechanism that brings about this change is called feedback In feedback systems, the response alters the stimulus 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 body temperature The receptors send their information to the control centre. The temperature control centre

in mammals is the hypothalamus. The hypothalamus responds by initiating responses to increase or decrease temperature, until it goes back to the set value (which is 37ºC)

Temperature control responses:

Analyse information from secondary sources to describe adaptations and responses that have occurred in Australian organisms to assist temperature regulation

Adaptations ExamplesBehavioural: The main behavioural adaptation in animals is they alter the position of the body or decrease the amount of exposure of SA to sunlight. They may seek shade or shelter in burrows if the temperature exceeds their tolerance level.

Frill-necked lizards bask in the sun until they reach an adequate core temperature then they retreat into the shade

The bilby is nocturnal (inactive at day, active at night) so that it doesn’t generate additional metabolic body heat during the heat of the day.

Structural: Structural adaptations that assist with temperature control include insulation such as fur, hair, feathers etc.

The Australian fur seal has blubber – a form of insulation to reduce heat loss

Physiological: Physiological adaptations focus on the inner body functions. Metabolic activity is important for the survival of individuals, but this also generates. Thus, the rate of this activity has be altered according to temperature variations

The common wombat slows its metabolism down to a third of its normal rate during hot days when it shelters in its burrow

The bilby has an extensive network of capillaries throughout the ear which aid the release of heat to the surroundings (due to large SA)

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

Identify the form(s) in which each of the following is carried in mammalian blood: carbon dioxide, oxygen, water, salts, lipids, nitrogenous waste and other products of digestion

Oxygen – when blood in the lungs comes into contact with oxygen that has entered the body by diffusion, haemoglobin (in the red blood cells) bind with the oxygen and form a compound called oxyhaemoglobin. This compound gives the bright red colour to blood.

Carbon dioxide – when CO2 enters the blood, 70% of it is transported in the form of hydrogen carbonate ions – formed in red blood cells but carried in the plasma. The remaining CO2 is either dissolved in plasma (7%) or is combined with haemoglobin (23%)

Water is carried as blood plasma, which is 90% water.

Salts – carried in blood as ions dissolved in plasma.

Lipids – a small proportion of lipids (fatty acids and glycerol) are soluble and enter the bloodstream directly, but most need to be packaged into small droplets, which pass into the lymphatic system and then into the bloodstream.

Nitrogenous wastes – these include ammonia, urea and uric acid which are all carried dissolved in blood plasma

Other products of digestion (glucose, amino acids) – glucose and amino acids are water soluble and are transported in the bloodstream dissolved in plasma

Explain the adaptive advantage of haemoglobin

Haemoglobin is a complex molecule within red blood cells which enable them to carry oxygen.

Adaptive advantages

It increases the oxygen-carrying capacity in blood (relative to plasma) Haemoglobin contains four haem units – giving one molecule the ability to bond with four oxygen molecules. Thus, far more oxygen can be carried in blood cells by haemoglobin than would be carried dissolved in plasma

Its ability to bind oxygen increases once the first oxygen molecule binds with it. The binding of each oxygen molecule changes the shape of the haemoglobin – making it easier for each subsequent oxygen molecule to bind to it. This means that it can bind with a maximum amount of oxygen in the lungs (high oxygen concentrations)

Its capacity to release oxygen increases when CO2 is present. It is important for haemoglobin to release the oxygen from the blood in tissues where the oxygen concentration is low so that oxygen is delivered to the cells that need it. Metabolising cells release CO2 which (indirectly) causes more oxygen to be released from haemoglobin.

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

The function of arteries and veins is to carry blood over relatively long distances, from one organ to another, whereas capillaries form branching networks to carry blood over relatively short distances within organisms.

Arteries carry blood away from the heart

Veins return blood to the heart

Capillaries bring the blood into close contact with tissues, allowing for the exchange of gases, nutrients and wastes.

Structure Function related to structureArteries o Walls of arteries are

relatively thick (compared to veins)

o Walls of arteries have a large proportion of elastic fibres

o No valves

o The walls are thick to suit blood pumping out of the heart in regular bursts of high pressure

o Elastic fibres allow the arteries to expand and accommodate for the increases in blood volume with each heartbeat

o No valves – pressure of heartbeat ensures one way flow

Veins o Few elastic fibreso Thinner wall than arterieso Valves

o Few elastic fibres as no stretch or recoil necessary

o Thinner wall due to blood

flowing through is at a lower pressure than blood through arteries

o Valves ensure one way flow of blood

Capillaries o Very thin wallso Vast network

o Wall is only one-cell thick to allow efficient diffusion of nutrient/wastes and efficient gas exchange

o Vast network allows a large surface area of exchange with cells

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

An increase in oxygen and a decrease in carbon dioxide concentrations are evident in the blood that has passed through the lungs; whilst a decrease in oxygen and an increase in carbon dioxide is evident in blood that has passed through any organ other than the lungs (i.e. in any organ where cellular respiration has occurred)

An increase in digestive end products (e.g. glucose, fatty acids) is evident in blood that has passed through the small intestine (which absorbs digested food). These products then travel through the bloodstream to the liver

A decrease in digestive end products, and an increase in nitrogenous wastes (e.g. ammonia, urea) is evident once blood has passed through the liver

A decrease in nitrogenous wastes is evident in blood that has passed through the kidneys, since they filter nitrogenous wastes out the blood and excrete them

Outline the need for oxygen in living cells and explain why removal of carbon dioxide from cells is essential

Oxygen is necessary for respiration, a process by which cells release energy from glucose. Energy is needed for the growth, repair of tissues, movement, excretion and reproduction. Without oxygen, this chemical energy stored in glucose and other food molecules cannot be released; thus preventing the metabolic processes within cells.

Carbon dioxide is produced in cells as a waste product of cellular respiration. It must be removed from cells to prevent a change in the pH, as carbon dioxide reacts with water in the body to form carbonic acid. A build-up of carbon acid is toxic, as it lowers pH of cells – reducing the efficiency of enzymes and affecting the overall homeostatic balance within an organism. Therefore, the removal of carbon dioxide is essential for the normal functioning of cells.

Describe current theories about processes responsible for the movement of materials through plants in xylem and phloem tissue

Xylem

Transpiration is the loss of water from plant leaves. Transpiration stream is the movement of water in the xylem vessels up the plant, from the roots to the leaves

The processes involved in the transpiration stream can be explained by the transpiration (evaporation) - tension- cohesion mechanism. Transpiration: water is evaporated from the leaves through the stomates, pulling water

from cells and xylem tissue Cohesion: water molecules stick together and have the ability to instantaneously

transfer pressure and tension Tension: As water is evaporated from the leaves, it causes tension in the water column

within the xylem. Due to the cohesion of the water molecules, water moves up the xylem like a wire being pulled up, and replaces the water lost

Adhesion: when the pull stops, water sticks to the side of the xylem vessel and does not fall down

Phloem

In the phloem, sugars and small amounts of other nutrients are transported by translocation from sugar sources in the plant to sugar ‘sinks’

The current theory explaining translocation uses the pressure-flow mechanism and is called the ‘source to sink’ model. The sugars from the leaves (source) are loaded into the phloem by active transport,

causing the osmotic pressure to shift (due to the difference in sugar/water concentrations) and thus water follows in by osmosis.

The opposite occurs at the sugar ‘sink’. Sugar and materials are removed from the phloem by active transport, reducing osmotic pressure in the phloem (due to higher water concentration), and water moves out by osmosis.

These two processes produce a difference in hydrostatic pressure in the phloem, causing the sap (sugar solution) to move from source to sink. Pressure flow, therefore drives the sugars in the phloem from photosynthetic/storage sites to other parts of the plant

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

Current technologies that allow measurement of oxygen saturation and carbon dioxide concentrations in blood are:

Pulse oximeters Arterial blood gas (ABG) analysis

Pulse oximeters

Pulse oximeters are used to measure the amount of oxygen in the patient’s blood. A clip with a sensor is placed on the finger or earlobe and the sensor is connected to a monitor that shows the pulse rate and oxygen saturation level. Two wavelengths of light: red and infra-red pass through the finger from the light source to the photo detector. The amount of light absorbed by the haemoglobin (and consequently the amount of light reaching the detector) depends on its degree of saturation with oxygen.

Note that most oximeters don’t measure carbon-dioxide levels (it is only as recently as 2005 that some oximeters with a carbon dioxide sensor were developed)

Conditions under which it is used:

When a non-invasive technique is required When rapid, continuous monitoring of arterial blood is needed Examples: during anaesthesia, during recovery phase or in intensive care units during

mechanical ventilation. Oximeters are useful in such situations as it can quickly detect problems with oxygenation.

Arterial blood gas (ABG) analysis

Arterial blood gas analysis is a more invasive technique of analysis, and involves removing blood from an artery (usually in the arm) and performing a blood test using a sensor which translates the chemical properties of the blood into an electrical signal that can be measured. It reveals far more detail about the levels of chemicals in the blood, including partial pressure of oxygen and carbon dioxid, the pH and level of bicarbonate ions.

Conditions under which it is used

Invasive, and there could be delay between sampling and availability of results When more detailed information about oxygen, carbon dioxide and pH levels are required Examples: provides vital information for critically ill patients who are on ventilators or

respiratory therapy, studies of lung diseases, or in severe cases of breathing disturbance.

Analyse information from secondary sources to identify the products extracted from donated blood and discuss the uses of these products

Red blood cells – they help increase the amount of oxygen that can be carried to the body’s tissues (by increasing haemoglobin levels) while not increasing blood volume. They are given to people with anaemia (whose bone marrow doesn’t make enough red blood cells), those who have kidney failure or acute blood loss.

Platelets – essential for blood clotting. They are given to people who have cancer of the blood or lymph. Patients undergoing cancer therapy do not make enough platelets and are also given platelets from donated blood

Plasma – contains blood clotting factors. It us used to treat people with clotting disorders such as haemophilia. It can also be used to adjust the osmotic pressure of blood and to pull fluids out of the tissues.

White blood cells - infection fighting component of the blood. White blood cells are only used occasionally to treat life-threatening situations when the cell count is very low or the white blood cells are not functioning properly (in most cases, antibiotics is used rather than white blood cell transfusions)

Whole blood – only used when absolutely needed, for example when a person has lost more than 20% blood volume

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

Artificial blood or blood substitutes are designed to carry oxygen and carbon dioxide. They are not involved in clotting, coagulation and immune defence.

The need for research in the development of artificial blood is as follows:

It can be stored for long periods and time and is easily transported It does not need to be cross-matched for different blood types (i.e. it is universally accepted

by all blood groups) Can be produced at large quantities at low cost (meaning it can be readily available in large

supplies, solving the problem of a shortage of blood donors) It is completely safe (has no toxic effects, is free of disease and does not trigger an immune

response)

Proposed replacements for blood include:

Perfluorocarbons (PFC)

Biologically inert materials Relatively inexpensive to make Can be made without biological materials, eliminating possibility of spreading an infectious

disease via blood transfusion However, it is not soluble in water, meaning that they need to be combined with other

materials (emulsifiers) to mix with blood Also, it can carry much less oxygen than haemoglobin-base d products, meaning that a lot of

PFC must be used

Haemoglobin-based products

Unlike whole blood, haemoglobin products do not have the problem of blood typing Raw haemoglobin cannot be used because it breaks down into smaller, toxic compounds

within body. There are also problems with the stability of haemoglobin in solution

Modifications, such as cross-linking molecules or using recombinant DNA technology are currently undergoing trial phases for eventual commercial use.

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 70-90% of living things and is essential for life. It is the solvent for all metabolic reactions in living cells.

Chemical reactions in cells can proceed only if the reactants are dissolved in water. Water and solute concentration in cells and fluids in living organs therefore must be maintained at a relatively constant level, within a narrow range so that these cellular reactions can take place

The movement of water into and out of cells depends directly on the concentration of solutions both inside and outside of cells.

If too much water moved into cells, they could burst (e.g. in animal cells which have no cell wall). If too much water has moved out, the cell contents could shrink, and the cytoplasm would become too concentrated for normal cell functioning

Thus, to ensure the proper functioning of living cells, the concentration of water must be kept constant.

Explain why the removal of wastes is essential for continued metabolic activity

If metabolic wastes were left to accumulate within the body, it would alter the conditions in the internal environment – inhibiting enzyme functioning and preventing cells from undergoing normal metabolic activity

The build-up of nitrogenous wastes such as ammonia would cause an increase in the pH of cells; the build-up of carbon dioxide in the body would react with water in cells and become carbonic acid, which would lower the pH of the internal environment. These changes in pH would prevent optimal enzyme functioning

Accumulation of wastes that do not alter pH may cause other problems such as increased solute concentration interfering with reaction rates and an osmotic imbalance affecting membrane functioning

Therefore, metabolic wastes need to be removed in order to maintain homeostasis within an organism.

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

In mammals and fish, the kidney has a dual role of excreting nitrogenous wastes and maintaining water and salt concentrations (osmoregulation).

Fish do not excrete nitrogenous wastes through their kidneys; they use their gills.

Marine Fish: Their kidneys conserve water, excrete salts and nitrogenous wastes. These fish are in a hypertonic environment (concentration of solutes is greater outside the organism)

Freshwater Fish: Their kidneys conserve salt, excrete excess water and nitrogenous wastes (by producing large amounts of dilute urine). These fish are in a hypotonic environment (concentration of solutes is higher inside the organism

Mammals: Their kidneys conserve water and salts when required, excrete excess water and salts and excrete nitrogenous wastes. The mammalian kidney can adjust the reabsorption of nitrogenous wastes, water and salts – varying the concentration of urine produced.

The kidney ensures that both the concentration of blood and interstitial fluid are constant.

Explain why the processes of diffusion and osmosis are inadequate in removing dissolved nitrogenous wastes in some organisms

Osmosis is a selective form of diffusion in which the cell membrane acts as a selectively permeable barrier that allows the passage of water but not larger molecules.

Diffusion and osmosis are both types of passive transport that require no energy input but are slow (relying on differences in the concentration gradient). They slow down as the concentration gradient becomes smaller and stop once the concentration gradient reaches equilibrium.

Problems with diffusion

The rate of movement is too slow Not all wastes would be removed by diffusion. Once concentrations within blood and urine

equalised, no further wastes would be removed. Their accumulation would change pH of cells and become toxic.

Not all glucose and amino acids (needed by the body) would be reabsorbed

Problems with osmosis

Too much water would be lost in urine since urine contains a large number of nitrogenous wastes, water will be drawn in by osmosis (producing dilute urine). This loss of water cannot be afforded by many terrestrial animals.

Distinguish between active and passive transport and relate these to processes occurring in the mammalian kidney

Passive transport occurs spontaneously – requiring no input of energy. It involves substances moving along the concentration gradient (from an area where there are many particles to where there are few particles). Diffusion and osmosis are examples of passive transport

Active transport requires the input of energy as it involves substances moving against the concentration gradient

Passive Active

In a mammalian kidney, water reabsorption is a passive process (it follows the movement of salts)

Some nitrogenous wastes (urea and ammonia are moved into urine by diffusion

Reabsorption of salts is an active process.

Glucose and amino acids are actively reabsorbed

Additional nitrogenous wastes are added to urine through active transport

Explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition

The functional unit of the kidney is the nephron. Each nephron has three main parts: Bowman’s capsule, the glomerulus and a long, thin tubule.

Filtration occurs in the glomerulus, where blood pressure forces the movement of small molecules from the bloodstream into the Bowman’s capsule (urea, glucose, amino acids, salts and water). These form the glomerular filtrate.

Reabsorption occurs in the tubules (proximal, distal tubules and the Loop of Henle). It involves both passive and active transport – whereby solutes required by the body are moved back into the bloodstream via the capillary network (ALL glucose and amino acids, SOME ions and water)

Glucose and amino acid reabsorption takes mainly in the proximal tubule. At frist, movement of glucose and amino acids is by facilitated diffusion (as the concentration is higher in the glomerular filtrate than the bloodstream) but once the concentrations become equal, active transport is utilised, until all glucose and amino acids are eventually reabsorbed

Salt reabsorption occurs in the proximal, distal tubule and the loop of Henle (sodium, chloride, potassium, calcium and hydrogen bicarbonate ions – HCO3

-) Water is reabsorbed along the length of the tubule by the passive process of osmosis. As the

reabsorption of solutes occurs, osmotic pressure is altered and water flows out passively together with the solutes

Note this is for understanding; not part of syllabus:

Secretion involves the selective movement of further substances from the bloodstream across the wall of the nephron into the filtrate by the process of active transport (some drugs, hydrogen ions and toxin molecules). It occurs in the proximal and distal tubules and is highly selective.

Excretion is where excess water and solutes are eliminated via collecting tubules in the form of urine (passing into renal, pelvis, ureter and then bladder for storage)

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

Antidiuretic hormone (ADH) or vasopressin is produced by the hypothalamus and stored by the posterior pituitary gland. Osmoreceptor cells in the hypothalamus monitor water and salt levels in the blood; when the water levels become too low, ADH is released – changing the water permeability of collecting duct walls so that more water is reabsorbed into the bloodstream from the ducts. It also increases the permeability of the duct walls to urea, which diffuse in from the bloodstream. These two effects cause the urine concentration to increase

Aldosterone is a hormone produced by the adrenal cortex in the adrenal gland when a decrease in the concentration of sodium ions is detected. It increases the permeability of the nephron to sodium, causing more reabsorption sodium ions, and consequently increased reabsorption of chloride and water (which follows by osmosis) as they follow the sodium ions. Thus there is more salt conservation within the body causing in a rise in blood volume and pressure (and also a reduction of the salt concentration of urine)

Both ADH and Aldosterone help the kidney carry out its homeostatic functions of osmoregulation:

Regulation of solute concentration in blood – regulating the amount of sodium and other ions that are reabsorbed or secreted in urine

Regulation of blood volume – maintaining a constant fluid volume by producing either concentrated or dilute urine.

Aldosterone brings about conservation of salts (and consequently water) in the body; ADH brings about water conservation in the body

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 despite variations in the environment.

Living organisms employ one of two strategies in Enantiostasis:

Osmoregulators are organisms that avoid changes in their internal environment and have the ability to keep the solutes at an optimal level (i.e. ‘regulating’ solute concentrations within the body) regardless of differing external environment. They cannot tolerate a range of salt concentrations within their body fluids/cells.

Osmoconformers are organisms that tolerate the changes in environment by altering the concentration of their internal solutes to match the external environment (“conforming” to that of the environment)

Estuarine organisms

An estuary is where a river meets the sea, and freshwater mixes with saltwater. Enantiostasis is important for organisms living in estuarine environment where salinity varies greatly.

Factors such as tide and rainfall greatly alter the levels of salts in the water. At high tide, sea water flows into the river mouth, creating a higher salt concentration (higher osmotic pressure); at low tide, sea water flows out and fresh water flows in.

In order for estuarine organisms to survive, adjustments are made in their physiology, such as to keep enzymes functioning despite changes in the salt concentrations in the external environment. Generally, Osmoregulators have body fluids similar to that of the marine environment, so when exposed to water, their mechanisms try to maintain the higher osmotic pressure within the body. Osmoconformers generally use small organic molecules to vary solute concentration of cells to match that of the surroundings

Osmoregulators: - In salt water, salmon can drink continuously and eliminate salts through their gills;

whereas, in fresh water they stop drinking, absorb salt through gills and excrete very dilute urine like freshwater fish

- Mussels in rock pools close their valves when the tide is out to keep salt concentrations inside the body the same as the seawater

Osmoconformers:- Eels have special cells in their gills that can act as salt absorbers and salt excretors - Sharks use trimethylamine oxide to regulate osmotic pressure in cells to equal that of

the environment

Describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss

Mechanisms that minimise water loss:

Examples

Reducing the internal temperature Eucalyptus trees and banksias have coarse, leathery leaves with a thick cuticle to reduce evaporation (from the epidermal cells) which would occur with thinner leaf cuticles.

Reducing exposure of leaves to the sun

Australian she-oaks have cladodes, which are green needle-like structures that are modified stems. Tiny brown scale leaves occur at regular intervals along the cladodes, a feature to reduce the SA of leaves and their exposure to the sun – thus minimising water loss.

Reducing difference in water concentration between plant and outside air

The coastal banksia has epidermal hairs, which trap a moist layer of air – resulting in a smaller difference between concentration of water in the leaf tissue and water vapour in the layer of air trapped by the hairs.

Features related to water storage The desert plant parakeelya has fleshy stems and leaves which swell up and retain moisture when it becomes available, so that during dry periods, it can survive by using up this moisture.

Gather, process and analyse information from secondary sources to compare the process of renal dialysis with the function of the kidney

People with dysfunctional kidneys are not able to remove wastes such as urea and other toxins. They have to undergo renal dialysis to regulate their blood.

The process (haemodialysis): - The blood is extracted from the body from a vein (invasive) and passed into a dialyser,

which is a bundle of hollow fibres made of a semi permeable membrane. - The dialyser is in a solution of dialysing fluid, which has similar concentrations of

substances as blood. The fluid flows in the opposite direction to the blood to maximise diffusion rate.

- 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 dialysing fluid must constantly be replaced so that the concentration gradient of wastes is maintained away from the blood

- The blood is then returned to the body.

Kidney functioning Renal DialysisOverall process Natural process which filters our

blood-removing metabolic wastes so that they may be excreted via urination

Artificial process which removes metabolic wastes that have accumulated in the blood

Functioning Pair of kidneys filter wastes, regulates pH, blood volume, water and salt balance (osmoregulation)|

Haemodialysis – blood passes through tubules surrounded by dialysing fluid for filtering

Active/passive Both active and passive transport is Relies on passive transport only – wastes

transport used in moving wastes from the blood

diffuse across artificial, selectively permeable membrane of the dialysis tubes

Maintaining the concentration gradient

Active transport occurs, so the concentration gradient is not as important in ensuring the removal of wastes

Waste concentration is higher in the blood than in the dialysis tube so diffusion occurs. The dialysis fluid is constantly replaced to maintain the concentration gradient

Speed at which blood is filtered

Much faster than renal dialysis (active transport involved, millions of nephrons increase SA)

Slower as it relies on diffusion only and the tubules do not provide as much SA as nephrons do

Regulation process

Hormonal control/Negative feedback mechanisms regulate the process naturally

Process is artificially controlled by a computer linked to scissors

Outcome Effective, efficient removal of wastes, excess fluids/saltsNon-invasive

Less effective removal – only removes wastes; doesn’t regulate ions in blood. Takes longerInvasive and carries risks

Present information to outline the general use of hormone replacement therapy in people who cannot secrete aldosterone.

Aldosterone increases the amount of salt (and consequently water) reabsorbed from kidney tubules

A lack of aldosterone may be the result of: damage to the adrenal glands due to accident, surgery or disease or damage to the pituitary gland that controls the adrenal gland

Without aldosterone, the body would not be able to reabsorb salt (specifically sodium ions) and this would cause severe dehydration, and excessive potassium. Many functions are disrupted as a result of this aldosterone drop and can lead to death.

Hormone replacement therapy involves restoring the balance of the hormones at levels that are normal for the body, by giving the patients genetically engineered hormones such as fludrocortisone to replace the hormones that they no longer produce naturally

Administered properly, it can do the job of aldosterone and enable patients to manage symptoms such as fluid retention and high blood pressure, removing dangers of heart failure - allowing them to lead normal lives

Analyse information from secondary sources to compare and explain the differences in urine concentration of terrestrial mammals, marine fish and freshwater fish

Freshwater Fish: Osmotic Problem: They are hypotonic to their environment. Water will tend to diffuse INTO

their bodies. Salts will diffuse out. Role of Kidney: Removes excess water. Produces large amounts of dilute urine. Kidneys also

reabsorb salts. They also rarely drink water.

Urine: Large amount but dilute. Marine Fish:

Osmotic Problem: Hypertonic to environment. Water diffuses out. High salt levels present in the water

Role of Kidney: Continually drinks water. Kidneys reabsorb water, while actively secreting salts. Produces small amounts of concentrated urine. Salt is also excreted across gills.

Urine: Small, concentrated amountTerrestrial 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.

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

Animals face the challenge of achieving a fine balance between the use of water to remove nitrogenous wastes and conservation of water in the body

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 in its soluble form, requires large amounts of water for its excretion. Urea is toxic, but much less toxic than ammonia and it can be safely stored within the body for a limited time and expelled with the removal of less waterUric acid is less soluble than ammonia or urea and has low toxicity, meaning that little water is expended to remove it.

Terrestrial Animals Releasing ammonia would be impossible due to lack of water. Instead, land-dwellers change ammonia into less toxic forms and release it periodically. Mammals change it into urea and release it as urine. (e.g. Kangaroos, wallabies, hopping mice, koalas, etc.) 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 (e.g. Acacia psyllids).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.

Process and analyse information form secondary sources and use available evidence to discuss processes used by different plants for salt regulation in saline environments

Halophytes are plants that have adapted to saline environments. They are commonly found in estuaries.

Grey Mangroves:

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.

Saltbushes:

Salt Accumulation: This plant stores its excess salt in swollen leaf bases, which drop off, ridding the plant of salt.

Perform a first-hand investigation to gather information about structures in plants that assist in the conservation of water

Saltbush:- The saltbush has waxy leaves that reflect heat and light

Eucalyptus:- Waxy, hard leaves: Reduces water loss by reducing the rate of transpiration from the

leave surface. - The leaves hang vertically, and this reduces the water loss, conserving water.

Banksia:- Leaves have sunken stomates – this reduces transpiration.

Wattle:- Leaves are small and hairy – the small size means less evaporation of water, and the

hairy leaves reduce the transpiration by trapping water.