maintaining a balance (2).pdf

8/9/2019 Maintaining A Balance (2).pdf

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[MAINTAINING A BALANCE] Winson Lo

Most organisms are active in a limited temperature range

1.1 Identify the role of enzymes in metabolism , describe their chemical composition anduse a simple model to describe their specificity on substrates

Metabolism : The sum of all chemical reactions occurring in the bod y There are two types of metabolic reactions:Anabolic reactions: building up larger organic compounds from simple moleculesCatabolic reactions: breaking down of complex organic compounds to simple ones

Role of enzymes : Every metabolic reaction in your body is carried out by enzymes. Theyare an organic protein catalyst; their role in metabolism is to increase the rate of chemicalreactions by decreasing their activation energy.

Chemical Composition : Enzymes are proteins and are therefore made from amino acids.They are globular proteins meaning the polypeptide chains (i.e. amino acids) are foldedinto a three dimensional globular structure. Within their structure, enzymes have activesites that are usually composed of three or four amino acids. The active sites are theareas that substrates will bind to and catalyse chemical reactions. The substrate is themolecule on which an enzyme acts on.

Specificity : Enzymes are specific in their action, meaning they affect only one type ofreaction.

Model :

Lock and Key - The enzyme is a lock and the substrate is a key. It explains enzyme actionby likening the enzyme to a lock and substrates to a key. Only a specific key is able toopen its matching lock. Just as the key is specific to the lock so is a substrate specific toan enzyme. An enzyme will not work unless the substrate matches its active site. Onlythen will the reaction be catalysed. This assumes that enzymes have a rigid unchangingshape.

Induced Fit Theory - It was later discovered that the substrate enters in and binds to theenzyme shaping the active site and properly aligning the enzyme for the reaction to take

place. A reaction will not be catalysed unless the substrates are able to properly shapethe enzyme.


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

pH : Scale which measures the concentration of moles of hydrogen ions per litre ofsolution.↑ hydrogen ions = ↓ pH / ↓ hydrogen ions= ↑ pHRanges from 0-14Acidic: 0-7Neutral : 7Alkaline: 7-14

1.3 Explain why the maintenance of a constant internal temperature is important formetabolic efficiency

Enzymes control all the metabolic processes in the body. They work best under optimum

conditions of temperature and pH. Any variation above or below this point reduces theirrate of activity. Large variations from this optimum level will alter or denature theenzymes, changing their shape and blocking the active site. Once denatured, an enzymeis permanently damaged and can no longer catalyse reactions.Changes in temperature and pH can break bonds in the protein molecule and overalldisrupt their three-dimensional shape – making them unspecific to the substrate.Therefore, at temperatures and pH‟s that vary from the optimum point, enzymes fail tofunction as efficiently or don‟t function at all and the maintenance of a constantinternal temperature is important for optimal metabolic efficiency as it maintains theoptimum level at which the enzymes can react while maintaining their specificity.


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1.4 Describe homeostasis as the process by which organisms maintain a relativelystable internal environment

In an organism, enzymes control all the metabolic processes. Multicellular organismsfunction best, and at optimum metabolic efficiency, when the internal environmentprovided for their cells is maintained at a constant level. If the internal environment variesfrom this point, the rate of enzyme catalysed reactions decreases. This decreased ratecould affect an entire metabolic pathway could result in fatality!

In multicellular organisms, cells need to maintain their internal balance regardless of theexternal environment. External environment conditions may vary greatly but the internalenvironment can be kept relatively unchanging and stable. This is because organismshave processes that quickly act to counter any changes made to the optimum conditionsand return to the stable state. This counteracting of changes and returning the organismto the optimum state to help maintain a relatively stable internal environment is knownas homeostasis .

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

Negative Feedback System is where the response to the stimulus is to reduce andcounteract the change. It causes the body to respond so that a reversal in the direction ofa change occurs.

Positive Feedback System is where the response to a stimulus is to amplify the change

instead of reducing it. This does not result in homeostasis.

Detecting Changes: In this stage, a receptor detects a change in a specific variable from

the desired stable level of the variable.

Counteracting Changes: An effector receives the message that an undesirable changemust be counteracted and the variable restored to its desired level


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This is how the negative feedback system occurs:

Stimulus: All organisms receive information from the various parts of their bodies andfrom their environment in the form of stimuli. It can be either external or internal.Receptor: A variation in either the internal or external environment is detected by areceptor. Sight, sound, touch, taste and smell are all receptors.Control Centre (Central Nervous System – CNS): Once a variation is detected, amessage is sent to the control centre. This then replies by sending a message to theeffector to counteract the variation.Effector: The effector is normally either a muscle or gland that responds to the messageand counteracts the variation.Response: This is the action of counteracting the variation.

1.6 Outline the role of the nervous system in detecting and responding toenvironmental changes

The nervous system is made up of the brain, spinal chord and sensory and motorneurons. The nervous system enables the detection of external and internal environmentchanges to the body and then coordinates the responses the body will make tocounteract these changes. It is made up of two interacting elements:

Central Nervous System – is composed of the brain and spinal chord. The spinal chordtransmits messages from the receptor organs via the sensory neurons to special regionsof the brain (hypothalamus).When one of these regions receives stimuli from the sensoryneurons it then coordinates the correct response necessary to counteract the change by

sending out messages to the effector organs via the motor neurons.

Peripheral Nervous System – is composed of neurons outside the CNS. These includesensory and motor neurons. Sensory neurons transmit messages from the receptororgans to the brain. Motor neurons transmit messages from the brain to the effectororgans to activate a response.

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

Life is found over a broad range of temperatures on planet earth. Where climatictemperature can vary from -75 oC to above 50 oC. However, most individual species havenarrow temperature limits and they cannot exist in habitats that have great varyingtemperatures. Most species can tolerate only a narrow temperature range so theypossess behavioural and physiological adaptations that enable them to maintain theirtemperature within this narrow range.


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1.8 Compare responses of named Australian ectothermic and endothermic organisms tochanges in the ambient temperature and explain how these responses assisttemperature regulation

Ambient Temperature : The temperature of the surrounding environment

Ectotherms : are organisms whose body temperature is determined by theirsurroundings. They have limited ability to control their temperature because their owncellular activities generate little heat.e.g. Plants, invertebrates, fish, amphibians, reptiles

Endotherms : are organisms that have physiological structures that enable them tomaintain their body temperature within a narrow range irrespective of the ambienttemperature . Their body metabolism generates heat and maintains an internal bodytemperature that is independent of the external temperature. To do this takes energy somore food is required by endotherms.e.g. Birds, Mammals

If temperatures are too hot or too cold for an organism, it may die. Aquatic ectothermsremain at the temperature of the surrounding water; they do not show any specialisedadaptations to regulate their body temperature.However, terrestrial ectotherms and endotherms experience a greater range oftemperature changes and have receptors to detect these changes. They show a variety ofresponses or adaptations to regulate heat gain and loss from their bodies.

Behavioural adaptations (change in behaviour)

Migration: Move to avoid temperature extremes (e.g. Sharp tailed sandpiper breeds inSiberia, travels south to southern hemisphere for non-breeding period)

Hibernation: Metabolism slows to avoid cold conditions, endotherm body temperaturedrops. 60% of the annual energy requirement is reserved. Aestivation is when animalshibernate in hot conditions (e.g. Bogong Moth aestivates in cool caves in Australian Alpsfor summer)

Shelter: Dig burrows, caves etc. (e.g. Central netted dragon climbs trees to seek coolerconditions off the ground)

Nocturnal Activity: Active at night (e.g. Desert animals like hopping mice and desertbandicoots shelter from heat in day and feed at night)

Controlling Exposure: Ectotherms alter posture to expose larger or smaller surface area tosunlight. Endotherms huddle or curl up to reduce heat loss (e.g. Penguins/Bats huddle,small mammals curl up, tuck legs in and curl tail around body)


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Structural (morphology of features) and Physiological (regulate a function)Adaptations

Insulation: Fur in mammals and feathers in birds form an insulation layer of trapped airthat slows down heat exchange. Thickness of air layer increased by contracting muscles(e.g. Domestic cats have a thicker coat of fur in the winter, fat can also be used asinsulation like the Australian Fur Seal‟s layer of blubber)

Metabolic Activity: Heat generated as result of metabolic activity. Shivering increasesmuscle activity and produces heat.

Control of Blood Flow: Blood flow and route adjusted to lower skin temperature butmaintain normal internal body temperature.

Counter-current Exchange: Blood vessels leading to and from extremities of the body areplaced close together and chilled blood returning in veins picks up heat from arteriesgoing to extremities (e.g. Legs of arctic birds, fins of seals, feet of platypus). Someectotherms also use this system (e.g. Yellowfin tuna and Skipjack tuna use heat frommetabolic activity from blood vessels going to gills to blood vessels coming from gills.This maintains heat within the fish‟s body)

Evaporation: Rate of evaporation of water can keep organisms cool. (e.g. Dog pants,humans sweat, birds flutter a membrane in their throat, kangaroos lick forearms so thatthe moisture can evaporate and cool forearms thus cooling blood)

Australian Endotherm - Red Kangaroo (5 - 38 degrees Celsius in dry, arid centralAustralia)

Physiological Structural Behavioural

ColdConditions

Increased metabolismto create more heatwithin body

Basking in sun

WarmConditions Decrease in metabolicrate Panting to releaseheat, Shunting ofblood to exposedareas

Nocturnal, Sitting inshade, Licking forelegsto increase evaporation


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Australian Ectotherm - Diamond Python (rainforests, grasslands)

Physiological Structural Behavioural

ColdConditions

Lies on eggs and shivers toincrease temperature ofincubation

Dark colour toabsorb heat

Basking in sun, Hibernation,Migration to warmer areas

WarmConditions

Nocturnal, Burrowing atnight

Compare the responses of endotherms and ectotherms

Endotherms need to have a high metabolism rate to maintain this optimum temperaturerate in cold conditions and as a result need to eat large amounts . Ectotherms do notneed to do this however they have greater restrictions placed on their activity as a result.In hot conditions endotherms must have specific adaptations to these environmentalchanges to regulate heat gain so not to raise their temperature above their optimumtemperature level as this can cause severe damage. This is the same for both endothermsand ectotherms in relation to cold climates. Ectotherms are not found in extremely coldclimates.

1.9 Identify some responses of plants to temperature change

Plants are ectothermic and so cannot maintain a constant temperature. Therefore theyhave a range of adaptations to help them survive in a variety of temperatures, the mostcommon of which is by altering their growth rate. Apart from this, there are several otherways plants respond to temperature changes in their environment.

Leaf Fall: Many plants in hot conditions reduce their surface area that is exposed to thesun by dropping their leaves. This reduces the amount of water lost in transpiration.

Transpiration: The movement of water through the plant helps to cool the plant duringhot conditions. This is also effecting when evaporation of water occurs from the stomatesof the leaf.

Heat-Shock Proteins: Produced by plants when they are under stress from very hightemperatures. They are thought to stop the denaturing of the enzymes within the cell, soallow normal cell reactions to continue.

Reflective Surface: Some plants reduce the amount of heat received by having shinyleaves that reflect solar radiation.

Orientation of leaves : Some plants orientate their leaves in such a way that it reduces the

amount of sun rays that make contact with the surface area of the leaf. e.g. eucalyptus


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Die Back: In harsh conditions, shoots of a plant may die. However the soil and roots willbegin to grow again when favourable conditions returns

Ice formation between cell : Most plants are able to tolerate fairly low temperaturescompared to animals. This is due in part to their cell walls as when temperatures dropbellowing freezing, ice will form outside of the plant cells. This is because the solutionwithin the plant cells is higher in solutes (and therefore higher freezing point) than thesolution between the cells. Ice will therefore form between the plant cells, which areprotected from ice crystals by cell walls. However this is ineffective if temperatures droptoo quickly, such as during a frost.

1.11 Gather, process and analyse information from secondary sources and use availableevidence to develop a model of a feedback mechanism

An example of a feedback mechanism is a thermostat. It is a device that measurestemperature and senses when the temperature is too low. When it detects lowtemperature it initiates a response - a heating process which brings the temperatureback to the appropriate level.


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1.12 Analyse information from secondary sources to describe adaptations andresponses that have occurred in Australian organisms to assist temperatureregulation

Adaptation/Response How it assists temperature regulation AustralianExample

Migration Moves to avoid temperature extremes Sharp-tailedsandpiper

Hibernation Slows metabolism, drops heart rate and oxygenconsumption to avoid cold temperatures

Bogong Moth

Nocturnal Avoid heat of the day by being active at night Hoppingmouse

Controlling exposure Changing surface area and volume exposure tosun to control how much heat is lost

Brown snake

Control of blood flow toskin and extremities

Vasodilation/constriction - allowing moreblood to the surface allows heat loss throughradiation

Humans

Metabolic activity Metabolising generates heat. Reduced in hotweather and increased in cold weather

Humans

Evaporation As moisture evaporates, heat is lost with it e.g.sweating, panting. As kangaroos lick theirpaws, spit evaporates taking heat with it

Red kangaroos


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

Composition of Blood: If a sample of mammalian blood is taken and spun in a centrifuge, itwill separate into two parts: the plasma and the cellular matter. Plasma makes up about 55%of the volume of blood. In whole blood, red and white blood cells and small particles calledplatelets are suspended in this plasma

Plasma: is a sticky, straw-coloured, slightly salted liquid. It is made up of about 90% waterand various other substances carried in solution. It contains salts (carried as ions) and largeplasma proteins. These salts and proteins play a role in maintaining the pH of the blood.There are different types of plasma proteins including antibodies, clotting factors and lipidtransporters. Many substances are transported in the plasma and their amount changes asthe blood circulates. 55%

Red Blood Cells: also known as erythrocytes. They are disc shaped and biconcave and arethinner at the centre than at the edges. They contain the pigment haemoglobin. Theirfunction is to transport respiratory gases particularly oxygen (carried as oxyhaemoglobin)around the body as well as carbon dioxide (carried as carbaminohaemoglobin). One millilitreof blood contains about 5-6 million red blood cells. 45%

White Blood Cells: also known as leucocytes. There are between 4000-12000 white bloodcells in one millilitre of human blood. The two important types of white cell are phagocytesand lymphocytes. Phagocytes surround and ingest bacteria, foreign bodies and dead cellsand collect are areas of infection or injury. Lymphocytes act specifically against foreign

material. They make antibodies which help the body‟s defence against disease. 0.1%

Platelets: are fragments of cells made in the bone marrow. They play an important role inhelping the blood clot and are about 3 µm in diameter.


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2.1 Identify the form(s) in which each of the following is carried in mammalian blood:

Substance From To Form Carried By

Carbon Dioxide Body Cells Lung Carbaminohaemoglobin RBC &Plasma

Oxygen Lungs Body Cells Oxyhaemoglobin RBC

Water Digestive System &Body Cells

Body Cells Water molecules Plasma

Salts Digestive System &Body Cells

Body Cells Ions Plasma

Lipids Digestive System &Body Cells

Body Cells Chylomicrons Lymph &Plasma

NitrogenousWaste

Liver & Body Cells Kidney Urea, uric acid andcreatinine

Plasma

Other productsof digestion

Digestive System &Liver

Body Cells Separate molecules Plasma

2.2 Explain the adaptive advantage of haemoglobin

In mammals, red blood cells contain haemoglobin , a protein molecule comprising of fourpolypeptide chains (called globins) and each is bonded to a haem (iron-containing)group. Each haemoglobin molecule contains four active sites where oxygen moleculescan be attached.

Mammalian cells need a lot of energy and must have continual supply of oxygen forrespiration. Oxygen from air diffuses into blood in the lungs and is transported in thecirculatory system to all blood cells. Oxygen diffuses across respiratory surfaces intoblood because it is in a higher concentration in the air than in the blood.

Oxygen is not very soluble in water. Blood is a watery liquid, and a 100 ml of blood cancarry 0.2 ml of oxygen if it relied solely on oxygen being dissolved in the plasma. Thepresence of haemoglobin increases oxygen carrying capacity by 100 times. 20 ml ofoxygen can be carried in 100 ml of blood .

The adaptive advantage of haemoglobin is to give mammals the ability to transport largequantities of oxygen to the tissues giving an organism the ability to become morecomplex.


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Haemoglobin, the red pigment in blood, transports oxygen from lungs to body cellsaround the body. This in turn allows the organism to carry out certain metabolicfunctions such as cellular respiration.

In the lungs, when the oxygen concentration is high, oxygen combines with haemoglobinin the red blood cells in to form oxyhaemoglobin.haemoglobin + oxygen → oxyhaemoglobin

Oxygenated blood is bright red. It is transported to the tissues, where oxygen levels arelow. At this lower concentration the reverse reaction occurs, and the oxygen releaseddiffuses into blood cells.oxyhaemoglo bin → haemoglobin + oxygen (4H 2O)

Carbon dioxide occurs in high concentration in the body tissues. It diffuses intocirculatory system, where it may be carried in blood in different ways. 70% of carbondioxide combines with water to form hydrogen carbonate ions (HCO 3--) in red blood cells.These are then carried in the plasma.CO2 + H 2O → H2CO3 → H+ + HCO 3-

23% combines with haemoglobin to produce carbaminohaemoglobin (This does notprevent oxygen from combining with the haemoglobin molecule)7% directly dissolves into the plasma.

At respiratory surface, CO 2 levels are low so the reverse reaction occurs and the carbondioxide diffuses out of the blood and to the external environment.

Haemoglobin transports CO 2 from body lungs to cells. It allows organisms to maintainblood pH as excess CO 2 in the bloodstream can alter pH and have an adverse affect onthe organism. Each red blood cell contains 280-300 million haemoglobin molecules .This adaptive advantage indicates that a large proportion of oxygen can be transportedwithin an organism and the organism can function at the optimum level.Adaptive advantage: Allows 4 oxygen molecules to bind to iron ions with the

haemoglobin structure to form an oxyhaemoglobin molecule.

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

Arteries: Thick muscular walls: cope with the high pressure of blood being pumped out to thebodyElastic walls: enables expansion and contraction to adjust to the amount of blood flowingthrough at any one timeSmooth inner layer: allows blood to flow with ease

Arteries carry blood away from heart, blood pressure is high.They contain muscle fibres which contract and relax


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Main function is to carry oxygenated blood taken away from the heart

Capillaries: Endothelium: a single layer of flat overlapping cells that are one cell thick allowing asingle file of red blood cells to pass through, maximising the opportunity for theexchange of gases, nutrients and wastes between the blood and the tissue cells. In thisway the body‟s tissue are efficiently supplied with the substances they need while wastesare removed

Veins: Thin muscular walls- this is in response to the lessened amount of pressure as the bloodis not being pumped hard as it returns to the heartWider diameter- allows increased amounts of blood to flow through veins and return toheartValves- prevent blood from flowing backwards in the veinVeins carry blood to heart, blood pressure is lowThey contain no muscle and rely on valves and when large muscle contract they helppush the blood flow through veinsMain function is to carry deoxygenated blood taken to the heart

2.4 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

The chemical composition of blood changes as it moves around the body. This is due tocontinuous exchange of substances between blood and surrounding tissues . Blood

moving through the body‟s tissues delivers oxygen and glucose for cellular respiration aswell as nutrients. Blood moving away from the body‟s tissues carries carbon dioxide andnitrogenous wastes for disposal.

Pulmonary Circuit (Lungs) Blood flows from heart to lungs and then back to the heartBlood is under lower pressure than the systemic circuitThe rate of blood flow is fasterVery little body fluid is formedThe blood contains high levels of CO 2 and low oxygen levels

Systemic Circuit Blood flows from the heart to the body (except the lungs) and returns back to the heart.Blood is under high pressure due to contractions of the left ventricle of the heart, butpressure gradually decreases.

Kidneys Blood loses urea and has the composition of water and salt balanced (osmoregulation)

Intestines

Blood collects the products of digestionLevels of glucose, amino acids and lipids rise


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Liver Regulates the level of glucose in bloodExcess glucose is converted to glycogen and is storedConverts excess amino acids to urea

Tissue Main Changes in Blood

Lung - ↑ oxygen- ↓ carbon dioxide

Small intestine - ↑ glucose and other products of digestion (amino acids, lipids,vitamins, minerals, water)

Kidneys - ↓ nitrogenous wastes (salts and water to form urea)

Other bodytissues

- ↓ oxygen- ↓ glucose- ↑ carbon dioxide

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

Need for oxygen : Cells need oxygen so that the process of cell respiration can occur.Cell respiration is essential as it provides energy that is needed for metabolic process and

if these processes do not occur, it can result in fatality.

Need for removal of carbon dioxide : The products of respiration are carbon dioxideand water. When carbon dioxide dissolves in blood, it forms carbonic acid which lowerspH. For most living cells that do not photosynthesis, carbon dioxide is a waste and mustbe removed as it can become poisonous if too concentrated in a cell. If carbon dioxideaccumulates, it becomes more acidic resulting in the denaturing of enzymes in the celland lowering their activity which can result in fatality of the cell. Low pH reduceshaemoglobin oxygen saturation, depriving cells of oxygen.

↑ CO2 means ↓ pH means ↑ rate/depth of breathing

↓ CO2 means ↑ pH means ↓ rate/depth of breathing


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

Movement in xylem occurs via the transpiration -cohesion -tension mechanism

Transpiration : Gases enter and leave the leaf through the stomata. Most of the water lostby the plant is in transpiration through the stomata. As water evaporates, water movesout of the cells to ensure that the walls of the mesophyll are kept most. In turn, waterfrom the small xylem vessels into the mesophyll cells. This is called transpirationpull/initiates the pull of the transpiration stream.

Cohesion : Water is drawn up xylem tubes to replace the loss of water due totranspiration, by capillarity (cohesive forces between the water molecules and adhesiveforces between water and cellulose cell walls)

Tension : A high concentration of water in the soil is absorbed by the root hairs whichhave a lower concentration of water. This is caused by osmosis and is called osmoticpressure.

Root pressure: plays a minor role in causing water to rise up the stem. At night, mineralions may be actively taken in through the roots but transpiration is low. Pressure buildsup and water is gushed up the stem. It can be seen as drops on the ends of the leavesearly in the morning (guttation) when pressure puts water out of leaves. As water ispulled upwards, some leaks out through pits. More water is lost by leakage in smaller,finer branching vessels.

Movement in phloem occurs by a mechanism known as “source -path- sink” or “pressureflow mechanism” and is driven by a pressure gradient generated osmotically.Translocation is the movement of organic materials to wherever they‟re needed,especially to growing points and reproductive structures.

Phloem loading at the source: as sugars are actively transported into phloem, waterfollows and osmotic pressure at the “source” increases. There are 2 theories for hownutrients in a leaf are “loaded” into the phloem: Symplastic loading : sugars/nutrients move in cytoplasm from mesophyll cells to sieve

elements through plasmodesmata. This theory requires plasmodesmata between leafcells.Apoplastic loading : sugars and other nutrients move along cell walls until they reach thesieve element, then cross the cell membrane by active transport to entre phloem tube.

Phloem unloading at the sink: as sugars are actively removed from the phloem, waterfollows, and pressure is low. Sink is a region of the plant where sugars/nutrients are beingactively removed e.g. roots, stem, flowers, and storage areas. This reduces pressure at thesource and the reduction of pressure at the sink causes water to flow from source to sink.Near the source, water moves from xylem vessels to phloem; near the sink, water moves

from phloem and xylem vessels. Having reached a sink area and been unloaded,transported nutrients are either used in metabolism or stored.


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2.9 Analyse information from secondary sources to identify current technologies thatallow measurement of oxygen saturation and carbon dioxide concentrations inblood and describe and explain the conditions under which these technologies areused

Oxygen Saturation: relates to the measure amount of oxygen in the blood. Normaloxygen saturation in the human body is about 96%

Measuring these concentrations helps doctors in diagnosis of patients and in monitoringthem while in hospital. It gives information about the ability of lungs both in providingoxygen to the body and removing carbon dioxide from the body as well as informationon the kidney‟s ability to reabsorb or excrete bicarbonate ions to maintain normal bodypH.

People who need this tested/monitored are patients-undergoing any procedure thatrequires anaesthesia or sedation, with abnormal breathing in intensive care, in accidentand emergency facilities, who are premature new-born babies, who shows dangerouslylow oxygen levels or high levels of carbon dioxide. Advances in biotechnology andelectronics have resulted in the product of biosensors that have made analysing bloodmore accurate. A biosensor is a device that translates a physical or chemical property intoan electrical signal that can be measured. The key component is the transducer or signalconverting element that converts the property to be measure into a signal. In hospitals, aPulse Oximeter is used to monitor the oxygen saturation of the blood and in dramaticcases, blood is taken from an artery for Arterial Blood Gas Analysis .

Pulse Oximeter : Pulse oximeters measure the amount of oxygen in arterial blood (bloodbeing pumped from the heart to the body cells). They consist of a sensor or probe that isattached to a part of the body such as a fingertip. When oxygen combines withhaemoglobin the colour of the blood changes from dark red (unsaturated) to bright red(saturated). Light from two light emitting diodes is passed through the finger and theamount of light energy transmitted is detected by two light detecting sensors. The lightenergy varies depending on the level of oxygenation of haemoglobin in the blood. Twodiodes are commonly used, one emitting red light (650nm) and the other infrared(940nm). Oxygenated blood absorbs red light whereas deoxygenated blood absorbsmore infrared light. There is a large difference in the amount of red light absorbed by the

oxyhaemoglobin compared to haemoglobin. By calculating the absorption at the twowavelengths the processor can compute the proportion of haemoglobin which isoxygenated. The signal is first amplified, then the oxygen saturation is calculated and theresult displayed on the screen. An alarm rings if oxygen saturation falls below a certainlevel, usually about 90%. Oximeters give no information about the level of carbon dioxideand therefore have limitations in the assessment of patients developing respiratoryfailure due to carbon dioxide retention.

Condition : on patients who are undergoing procedures that require anaesthesia orsedation to alert staff to expected hypoxia, with patients who are on a ventilator (artificial

breathing machine), helps assess whether a patient‟s oxygen therapy is adequate , used insleep laboratories for patients who are having difficulty breathing when they sleep.


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Arterial Blood Gas Analysis : Arterial blood is taken from easily accessible artery; eitherthe wrist, upper arm or groin. The syringe that is used contains a small amount ofheparin, to prevent the blood from coagulating. Once the sample is obtained, care istaken to eliminate visible gas bubbles, as these bubbles can dissolve into the sample andcause inaccurate results. The sample is then packed in ice and taken to the laboratory.Here, the blood sample is put into a machine which measures the oxygen saturation, pH,the partial pressures of oxygen, carbon dioxide and the bicarbonate concentration(amount of carbon dioxide carried in blood). The pH is measured with a glass bulb thatcontains a known solution of known pH. When this sensor is placed in an unknown pHthe difference between the two solutions is calculated and so pH of the solution isdetermined. Blood pH is a reflection of the concentration of hydrogen ions in blood. Ahigh concentration gives a low pH (acidic) and a low concentration gives a high pH(alkaline). Partial pressure of oxygen shows the concentration of a gas in a medium andtherefore displays how much oxygen the lungs are delivering to the blood. It is measuredusing a Clark oxygen sensor. Oxygen from the blood sample diffuses through a gas-permeable membrane where it causes an electrical current to be generated. The amountof current generated is proportional is proportional to the concentration of oxygen in thesample. This is measured and the result reported. Carbon dioxide levels are tested by asensor, based on the design invented in 1965 by Severinghaus. The sensor detects pHchanges in a small volume of bicarbonate solution separated from the sample by a gaspermeable membrane. As carbon dioxide crosses the membrane, the following reactionsoccurs:carbon dioxide (CO 2) + water (H 2O) → carbonic acid (H 2CO3) + hydrogenions (H +) + hydrogen bicarbonate ions (HCO 3-)

Any change in hydrogen ion concentration changes the pH. This is measured by theinternal pH sensor. pH as a measure of the concentration of hydrogen ion can be relatedto the concentration of carbon dioxide. This calculation is made and the result reported.

Condition : monitoring a patient during therapy, diagnosis of a respiratory disease, toinvestigate function of kidneys intensive care units e.g. baby care units and labour wards.

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

Donors are screened for health, past medical history, and risk of viral infections. Usually470 mL of blood is collected in a plastic bag containing an anti-clotting agent, andstored for a maximum 35 days. Compatibility tests are carried out to make sure thereare no antibodies in recipient's blood that react with the donor‟s red cell antigens. Whole Blood: volume replacement in cases with large blood loss (emergencytransfusion)Red Blood Cells: treatment of anaemia and bleeding after trauma/surgery(Filtered red cells: for patients who have antibodies against white cells)White Blood Cells: for patients who are not producing their own white cells or who havea serious bacterial infection

Platelets: control of haemorrhage (severe bleeding); patients with low platelet count


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Modified Haemoglobin :Advantages - Haemoglobin has high oxygen carrying capacity, can be extracted fromdonor blood and used by itself (doesn‟t need to be cross matched) , can be sterilised toremove pathogens without affecting its function, can be stored as a stable dried powder

Problems - Cannot be used as a blood substitute in isolation from red blood cells astoxic changes occur to haemoglobin in isolation. Red blood cell membrane contains acofactor which is needed by haemoglobin to release oxygen as required. In circulation,haemoglobin is rapidly broken down and excreted by the kidneys. This is toxic to thekidneys. Researchers are attempting to stabilise isolated haemoglobin and make it safeto use as a blood substitute.

Advances :Encapsulated haemoglobin- Artificial red blood cells have been produced which havethe necessary cofactor, and hence an oxygen dissociation curve similar to real RBCsHaemoglobin is not broken down inside theseThese artificial RBCs have no blood group antigensHowever, these artificial cells are rapidly removed from circulation and current researchfocuses on improving circulation timeCrosslinkedhaemoglobin-A diacid is used to crosslink haemoglobin to makepolyhaemoglobin, which does not break down in isolationResearch is being done in both intramolecular and intermolecular cross linkingRecombinant haemoglobin- is also being investigated, using genetic engineering toproduct haemoglobin that does not break down in circulation

Perfluorocarbons : are compounds derived from hydrocarbons by replacement ofhydrogen atoms by fluorine atoms.Advantages- Oxygen and carbon dioxide are highly soluble in PFCs, since a PFCmicrodroplet is 70 times smaller than in red blood cells, these PFCs can carry oxygen toplaces in the body that red blood cells cannot, inert and can be sterilised, can be storedat room temperature, shelf life of 12 months or more, no matching of blood typesrequired, c an be used temporarily during surgery to partially replace patient‟s blood sothat blood loss during surgery is minimised (must be combined with lipids to form anemulsion that can mix with blood).

Problems- Maximum amount used is only 20% because of viscosity of PFC emulsion athigh concentrations. Because of this smaller amount used, and also oxygen is dissolvedin PFCs rather than bound to it, sufficient oxygen carriage can only take place whenpatients are breathing >70% oxygen, PFCs are rapidly removed from circulation, Theretention of PFCs in the reticuloendothelial system (RES) suppresses the system,resulting in lowered resistance in infection

Advances - One current PFC product, “Oxygent”, can be used in higher concentrationsthan normal. Oxygent is being used in clinical trials in surgical patients to offset blood

loss during surgery and in the future, the small PFC particles may also help affectedtissues in thromboses or embolisms


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Animal Waste produced Explanation

Fish(aquatic)

Ammonia Secrete ammonia directly into the waterSave energy by not having to convert it into a safe molecule

Mammals(terrestrial)

Urea Humans are not surrounded by water and must store theirwaste for a period of timeUrea has a much lower toxicity than ammonia and is solubleand can be excreted in a soluble formIt does not require as much energy to produce as uric acid

Birds(terrestrial)

Uric acid Because birds produce eggs they must produce a waste that isvirtually non-toxic so that it can sit in the egg for a long periodof timeUric acid requires a lot of energy but stay as a solid mass in the

egg until hatchingAdult birds also produce uric acid which is almost insoluble inwater and can be excreted as a paste, conserving water

Reptiles(terrestrial)

Ammonia or uricacid

Aquatic reptiles produce ammonia for the same reasons as fishTerrestrial reptiles produce uric acid for the same reason asbirds

Insects(terrestrial)

Uric acid crystals This preserves water- even less water than the paste excretedby birds and reptiles

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

Osmoregulation : maintenance of a constant concentration of salt ions and thereforewater levels within the body regardless of the concentrations of the externalenvironment.The kidney is part of the urinary system and is the main organ involved in the excretionof wastes and osmoregulation in fish and mammals.The role of the kidney is to excrete waste (e.g. hormones and vitamins), maintainosmoregulation, maintain appropriate pH levels in the blood, reabsorb nutrients that areneeded.In fish: Kidneys maintain constant concentration of internal fluid for the cellsIn mammals : Kidneys excrete urea and regulates internal salt/water concentrations


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3.4 Explain why the processes of diffusion and osmosis are inadequate in removingdissolved nitrogenous wastes in some organisms

Osmosis and diffusion are both examples of passive transport in that they do not requirethe expenditure of energy. In unicellular organisms, the process of excreting nitrogenouswastes occurs solely by these two processes. They are not selective processes; they resultin the movement of any substance small enough to cross the cell membrane where thereis a concentration gradient. The cell membrane of these unicellular organisms are semipermeable allowing water molecules to enter by osmosis when necessary andnitrogenous wastes to exit by diffusion.However multicellular organisms are made up of millions of cells and it is too difficult forthis same process of excretion to work. The processes are inadequate as they do notoccur fast enough to maintain the required solute concentrations in cells. To removethese wastes, the water in which they are dissolved must also be excreted. The waterrequired to remove these wastes is an important consideration for osmoregulation. Dueto these reasons, active transport is a mechanism that substitutes diffusion and osmosisin many multicellular organisms.

Diffusion is too slow to maintain normal functioning of the body. If removal isdependent only on diffusion, wastes would be able to move only if they were moreconcentrated inside cells/bloodstream than in fluids outside. As concentrations equalise,movement slows and eventually stops.Osmosis only deals with the movement of water and thus would only allow water tomove out of the body, not the nitrogenous wastes. Too much water may be lost in urine.If urine contains lots of nitrogenous wastes, water is drawn into urine by osmosis to dilute

wastes and equalise concentrations. The movement of water makes waste too dilute,slowing down the excretion by diffusion

3.5 Distinguish between active and passive transport and relate these to processesoccurring in the mammalian kidney

Passive transport : diffusion of molecules from regions of high concentration to lowconcentration without the expenditure of energy, This includes diffusion, facilitateddiffusion (specific carrier protein assists diffusion), osmosis and filtrations (caused byblood pressure).

Active transport : the net movement of particles against a concentration gradient from anarea of low concentration, with the expenditure of energy. Specific carrier proteinsmembrane may bind with substance and carry it across the membrane. This includesendocytosis where a pouch is formed that carries the matter through the membrane.

Mammalian kidney :Passive transport - 98% of water needs to be reabsorbed from the filtrate and returned tothe blood. It can move by osmosis only if there are more solutes outside the tubule thaninside the tubule. Solutes in the filtrate will tend to diffuse out through the tubule walls

into the tissue fluid and the blood, but once the concentration are equal there will be nofurther net diffusion. If all of a substance needs to be reabsorbed, then active uptake


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must occur. Osmosis of water moves out of the nephrons at the proximal tubule, loop ofHenle and collecting ducts.

Active transport - occurs in secretion of substances into the nephrons, reabsorption ofnutrients back into the blood, and selective reabsorption of salts required by the body.

3.6 Explain how the processes of filtration and reabsorption in the mammalian nephronregulate body fluid composition

The nephron is the functional unit of the kidney, it filters the blood of metabolic wastes,make and secrete urine and reabsorbs water to maintain homeostasis. There are millionsof nephrons in the kidney‟s cortex and medulla. The reabsorption of water from the urine allows the nephron to regulate body fluid composition. This reabsorption along withsecretion back into the nephron helps maintain constant composition of blood andinterstitial fluid. The purpose of nephrons is to reabsorb useful molecules, keep unwantedmolecules in the tubule, balance the pH of blood and to maintain the correct osmoticbalance in the blood (water/salt).

Part of theNephron

Main function

Glomerulus A bunch of capillaries in an area of high blood pressure which has a semi-permeable membrane allowing for the removal of small molecules and ionsfrom the bloodstream.

Bowman‟sCapsule

A cup shaped structure surrounding the glomerulus that collects materialgoing out of the blood

ProximalTube

Most of the bicarbonate ions are reabsorbed and some hydrogen ionssecreted which helps maintain constant pH of blood and body fluids. Drugsand poisons are secreted into the tubule. Nutrients such as glucose andamino acids are actively transported from the tubule back into the blood.Regulation of salts also occurs here.

Loop ofHenle

In the descending part, Walls are permeable to water but not to salt. Thisallows water to pass by osmosis. In the ascending part, the converse happensand the walls are permeable to salt but not water. The salt passing out makesthe interstitial fluid of the medulla concentrated.

Distal Tube Selective reabsorption and secretion occurs to adjust pH of the blood andlevel of salts. The walls of conducting ducts are permeable to water but notsalt. Water passes out by osmosis and the final filtrate or urine is formed.

CollectingDuct

The materials remaining after reabsorption of wastes move through thistubule. The waste in the tubule is urine which is passed into the pelvis of thekidney.


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

The kidneys play a major role in maintaining water and salt levels in the blood. They areaided by hormones (chemical control substances) product by the body‟s endocrinesystem. The two main hormones involved in osmoregulation are Aldosterone and Anti-diuretic hormone (ADH) .Note: High salt concentration=Increased blood volume/pressure

Aldosterone : hormones produced by the adrenal cortex that regulates the salt balance(increases salt retention). A consequence of low water levels is low blood pressure, as aresult of lessened blood volume. This change in blood pressure is detected by thereceptors in the kidneys, resulting in the release of Aldosterone. Aldosterone acts tocontrol the reabsorption of solutes, specifically sodium. The higher the level ofAldosterone, the more permeable the walls of the nephron are to the sodium. Sodiumions and water is reabsorbed back into the blood.

Low water = Low blood pressure → Release of Aldosterone → More sodium reabsorbedin kidneys → More Water returned to blood

High water = High blood pressure → Reduced Aldosterone output → Less sodiumreabsor bed in kidneys → More salt/water lost in urine

ADH: hormone produced by the hypothalamus that controls the reabsorption of water inthe kidneys (increased water retention)

Diuresis: loss of urineDiuretics: substances that increase the volume of urineHypothalamus has osmoreceptors that detect a rise in the concentrations of solutes inthe blood (low concentration of water). As a result, ADH is released into the bloodstreamby pituitary gland, travelling in blood to the distal tubule of the kidney. This increases thepermeability of distal and collecting tubule walls so that more water is reabsorbed. Thisresults in an increase in the amount of water returned to the blood and a decrease in theamount of urine produced.

Low water = High solute concentration → Release of ADH → More water absorbed in

kidneys and returned to blood

High water = Low solute concentration → Reduced ADH output → Water passed out inurine


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3.8 Define enantiostasis as the maintenance of metabolic and physiological functionsin response to variations in the environment and discuss its importance to estuarineorganisms in maintaining appropriate salt concentrations

Enantiostasis : the maintenance of metabolic and physiological functions in response tovariations in the environment. Enantiostasis is not a form of homeostasis for it involvesmaintaining only functionality in spite of external fluctuations, as opposed to themaintenance of stable ideal conditions in homeostasis

Estuary : are areas where the fresh water from one or more rivers mixes with the salt waterfrom the ocean. In this environment, fresh water draining from land mixes with salinewater from the sea. Due to tidal movements, the salt concentration is constantlyfluctuating. There is a salinity gradient in an estuary, with high salinity at the ocean endand low salinity in the other end.

Organisms that live in this habitat undergo enantiostasis , meaning they employ varioustactics to cope with changing salinity. Many estuarine animals use behaviouraladaptations. Some burrow into the sand or mud where the salinity changes are lesspronounced than in the water. However, plants are unable to avoid the salt fluctuationsso they must undergo enantiostasis .

Osmoregulator : organisms that have special physiological mechanisms that allow them tocontrol salt levels in their bodies. (e.g. marine mammals, most fish)Osmoconformers : organisms that tolerate environmental change by altering

concentration of internal solutes to match the external environment. It moves up anddown in parallel with the level of the environment. Osmotic pressure is then the sameinside and outside the body, therefore metabolism and cell function can continue. (sharksand various species of algae)Stenohaline: organisms can tolerate little or no change in the salinity of theirenvironmentEuryhaline: organisms can tolerate a wide range of salinities

Plant example - Avicennia marina (Grey Mangrove) It has special tissues in the roots and lower stem that are like barriers to the uptake of salt

that help the exclusion of salt.It is also able to concentrate and secrete salt through special glands on the underside ofits leaves.

Animal Example –Dugong Drinks seawater and actively secretes minimal amounts of concentrated urine.


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3.9 Describe adaptations of a range of terrestrial Australian plants that assist inminimising water loss

Xerophytes : Plants adapted to arid or dry conditionsWater loss generally occurs as a by-product of transpiration. If a plant needs to reducewater loss it must close its stomata to do this. However, this plant needs tophotosynthesis and respire, processes that need the stomata to be open for gasexchange. In general, plants which are well adapted to the arid climate have:

Ability to close stomates when temperatures rise at midday Hairs that reduce airflow over surface, thus reducing evaporation Woody petiole to reduce water loss Leaves close together to reduce air flow around leaves Hard leaves with waxy cuticle Extra thickening of cell walls throughout their branches, so they don‟t wilt even

though they may lose large amounts of water Thicker bark

Adaptation Plant How?

Phyllodes Acacia group Replaced leaves with a modified leaf stems called phyllodes.They are green and able to photosynthesise life a leaf butcontain fewer stomata per square centimetre than normal leaves.Therefore reduces transpiration and water loss for the plant.

Reduce size of

leaves

Casuarina

equisetifolia

Reduces the amount of stomata present on the leaf‟s surface

and therefore reduces transpiration stream.

Sunkenstomates

Wollemi Pine Leaves have stomates that are set into or „sunken‟ into the leaf.The stomates have no direct contact with the sunlight so waterevaporation is reduced.

Hairy Leaves Paper Daisy Leaves and sometimes stems are covered in hairs to reducewater loss. The hairs trap water that has evaporated from theplant, increasing the humidity around this area. This humiditydecreases the transpiration rate.

Leaf curl Flax Lilies Will curl their leaves when temperatures get too high. Most oftheir stomates are located on the upper side of their leaves sowhen the leaves roll up, the stomates are on the inside protectedfrom heat and evaporation.

Leaf shape Native PigFace

Grows on sand dunes so exposed to sunlight practically all day.Leaves are triangular in shape to reduce the surface areaexposed to sunlight and decreasing water loss.


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

Renal dialysis : Artificial process in which wastes in blood are removed by diffusionacross a partially permeable membraneRenal dialysis is used for people who have impaired kidney function, where products ofmetabolism (including urea, creatinine and uric acid) build up in the body. Highconcentration of these substances can cause symptoms such as tiredness, weakness,loss of appetite and vomiting. The level of creatinine in the blood is often used as ameasure of the degree of kidney failure.

Haemodialysis : Blood is drawn from an artery where Heparin, an anticlotting factor isadded. It passed through dialysis tubing made of semi-permeable material. The tubingpasses through a container of dialysis fluid (balanced salt solution). The membraneallows wastes to diffuse across into dialysis solution, but not bloods cells, platelets orproteins and excess water is removed by osmosis. Dialysing fluid is constant replaced tomaintain concentration gradients and to ensure maximum waste removal.Haemodialysis can be used only 4-5 hours at a time, 3 times a week. It is dangerous touse large quantities of Heparin, because blood cells may be damaged as they passthrough the plastic tubes and because there is a risk of infection.

Peritoneal Dialysis : Blood is purified inside the body using the peritoneum (membranethat lines the abdominal cavity) as a natural filter. The dialysis solution enters theabdominal cavity via a catheter. Natural membrane lining peritoneal cavity is a partiallypermeable membrane so wastes diffuse and excess water moves by osmosis from inside

peritoneum membrane down the concentration gradient into the fluid. The waste filledsolution is then drained from cavity and disposed of. This process is carried out daily,using four lots of dialysis solution totalling about 2 litres in volume. Each solution isallowed to take up wastes for about 4 hours.

A renal dialysis successfully replicates the passive transport components of the kidney‟sfunctions but cannot replicate the kidney‟s use of active transport. Urea and excesswater/salts diffuse from blood to dialysis fluid, instead of leaving by pressure filtrationas in the nephron. Dialysis is a slower and less efficient process than natural processesfound in a healthy kidney.


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

The pituitary produces a hormone that influences the secretion of hormones from theadrenal cortex, including aldosterone. If there is damage to the adrenal cortex gland, itcan result in the gland producing insufficient levels of all adrenal cortex hormones,including aldosterone.

Hypoaldosteronism : a condition where people fail to secrete aldosteroneAddison‟s disease : a disorder that occurs when the adrenal glands do not produceenough of their hormones; in this case, the inability to secrete aldosterone from theadrenal cortex, caused by shrinking/destruction of the adrenal gland.

The effect of low aldosterone level s due to Addison‟s disease includes excessiveamounts of sodium are excreted with high urine output, dehydration, low sodium levels,high potassium levels, high acid levels, lowered blood pressure/volume which can leadto heart failure. Symptoms include fatigue, muscle weakness, weight loss and skinchanges, As a result, people with insufficient levels of adrenal cortex hormone requiremultiple hormone replacement therapy, using a synthetic hormone calledfludrocortisone (Florinef). Careful monitoring is needed to avoid fluid retention and highblood pressure. Patients are advised to increase salt intake.

3.13 Analyse information from secondary sources to compare and explain thedifferences in urine concentration of terrestrial mammals , marine fish andfreshwater fish

Isotonic : When the two solutions have the same concentration of solutes. Thereforethere is no net movement of solutes by diffusion and no net movement of water byosmosisHypertonic : Concentration of solutes is greater outside the cell than inside. Water willflow out of this solution by osmosis. (less concentrated/less solutes than surroundings)Hypotonic : Concentration of solutes is greater inside the cell than outside. Water willflow into a hypertonic solution by osmosis. (more concentrated/more solutes thansurroundings)

Nitrogenous Waste Product Toxicity Solubility inwater

Animal

Ammonia High High Fish

Urea Medium Medium Terrestrialmammals

Uric Acid Low Low Insects,reptiles,birds


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Freshwater Fish: Tissues are hypertonic to surroundings. The concentration gradientresults in a loss of salts and an uptake of water. Therefore the fish must remove waterand keep salts to maintain homeostasis. They do not drink water, secretes copiousamounts of very dilute urine that contains ammonia, kidneys actively reabsorbs salts(NaCl) to prevent salt loss, gill membranes permeable to water, gill actively absorb ions(some ammonia leaves gills at the same time).

Saltwater Fish : Tissues are hypotonic to surroundings. The concentration gradient resultsin a loss of water and an uptake of salts. Therefore the fish must retain water to maintainhomeostasis. They constantly drink seawater to replace water losses, excrete smallamounts of concentrated urine , tubules actively secrete MgSO 4 ,gill membranes arerelatively impermeable to water, gills actively secrete sodium from chloride cells;chloride ions follow.

Note: Marine cartilaginous fish (sharks and rays) have tissues isotonic to seawater toavoid osmoregulation problems.

Note: Freshwater and saltwater fish are both osmoregulators.

Terrestrial Mammals : Mammals must produce urine to be able to excrete theirnitrogenous waste (urea). Oxidation of proteins results in urea, as well as carbon dioxideand water, causing water loss. The urine concentration changes with the availability ofwater, as well as temperature and water loss through sweat.

Desert Terrestrial Mammal : Little water loss occurs as most is retained through kidneys

(long loops of henle) and therefore produces very concentrated urine .

3.14 Use available evidence to explain the relationship between the conservation ofwater and the production and excretion of concentrated nitrogenous wastes in arange of Australian insects and terrestrial mammals

Australian insect Australianinsect

TerrestrialMammal

Terrestrial Mammal

Name Meat Ants Leichardt's

Grasshopper

Spinifex hopping

mouse

Common Wallaroo

Location Sand or gravel inurban, forest,woodland areasacross Australia

Sandstoneplateaus innorthernAustralia e.g.Arnhem land

Desert - centraland westernAustralia ingrasslandsdominated byspinifex or mulga

Arid inland ofAustralia. Dry areas

Type ofnitrogenouswaste

Uric acid Uric acid Urea inconcentratedform

Urea, concentratedurine


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Excretorysystem/H 2O

Malpighiantubules - blindending kidneytubules that open

directly into thehid part of thedigestive tract.Tubules collectwater and uricacid fromhaemolymphuseful substancesreabsorbed bythe intestines andwastes leavethrough the anus

Malpighiantubules closeto rectum sosolutes in the

tubules drawwater byosmosis acrossthe lining ofthe rectum sovery dry faecesproduced.Extremelyefficient inconservingwater

Females feedingyoung haveconcentrated milkand drink urine of

their young. Largeloop of Henle forgreaterreabsorption ofwater and smallerglomerulus andBowman's capsuleto reduce amountfiltered andtherefore waterlost.

Excrete concentratedurine via kidney.Large loop of Henle,small glomerulus

and bowman'scapsule. 70% offiltered urea isreabsorbed throughthe kidney filtrate.

Relationshipbetween H 2OConservationand wasteproduction

Uric acid isinsoluble in waterso little water islost duringexcretion.Important wherewater is scarce

Arnhem land isa very dry area.Efficientexcretorysystemminimiseswater loss

The animal livesin a very aridenvironment. Itdrinks very littlewater andexcretes urea in aconcentratedform, so thatwater can beconserved. It hasvery concentratedurine due tonephron structureand behaviouraladaptations toconserve water.

70% of filtered ureareabsorbed duringadequate diet. Up to90% urea filteredand reabsorbedduring dehydration.Urea urine to plasmaratio remainsconstant suggestingthat ureareabsorption ispassive. Wallarooshave a very efficientexcretory systemthat recyclesnitrogen and urea tomake veryconcentrated urine.

This allows them tosurvive in very aridenvironments.


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3.15 Process and analyse information from secondary sources and use availableevidence to discuss processes used by different plants for salt regulation in salineenvironments

Halophyte : A plant that successfully inhibits areas of high salinity. Possess variousadaptations to assist them in surviving high salt level in their surroundings. (e.g.Saltbushes ( genus Atriplex ) that have special salt excretion glands in their leaves and arethe dominant species in salt-marsh communities throughout Australia)Most plants cannot tolerate salty condition in saline environments the soluteconcentration in the soil is greater than it is inside the plant‟s root and so water tends tomove out by osmosis.An excess of sodium ions inside cells inhibits enzymes activity and can result in adecrease in the uptake of essential potassium ions and therefore it is important forplants to regulate salt.

Plants in saline environments use three main processes for salt regulation:

Secretion - plants are able to concentrate salt and remove it through glands on leaves(Grey Mangrove: the salt is washed off by rain)Exclusion - Special tissues in the roots prevent salt uptake but allow water.Accumulation - Some plants allow salt to accumulate in older tissues which are laterdiscarded (Mangrove concentrates salt in its old leaves which then fall off)

Plant Process of Salt Regulation

Salt marsh plant(Sarcocorniaquinqueflora)

Salt collected in swollen leaf bases then are shed from theplant

Atriplex (saltbush) Sodium ions are concentrated in salt glands within the leafwhich eventually expand and burst, releasing the excess salt.

Palmer‟s Grass(Distichlispalmeri )

Salt leaves the plant through the cells on the leaf, builds upon the leaf surface and is ultimately washed away

Northfolk Island Pine Exposed to salty air and prevent salt from entering theirleaves by covering the stomates with a thin layer of cuticle

Grey Mangrove Salt is secreted in from the cells of the plant onto the lowersurface of the leaf and into bark. The leaves are thendropped and water dissolves the salt off the bark.The endodermis in the roots forms a barrier against thepassage of most salt into the xylem so the xylem containsreasonable fresh desalinated water.

maintaining a balance (2).pdf

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