Biology multicellular organisms

MAINTAINING A BALANCE

Contextual Outline
Multicellular organisms have specialised organ systems that are adapted for the uptake and transport of essential nutrients from the environment, the utilisation or production of energy and the removal of waste products arising from cellular activities.
The basis of healthy body-functioning in all organisms is the health of their cells. The physical and chemical factors of the environment surrounding these cells must remain within narrow limits for cells to survive. These narrow limits need to be maintained and any deviation from these limits must be quickly corrected. A breakdown in the maintenance of this balance causes problems for the organism.
The nervous and endocrine systems in animals and the hormone system in plants bring about the coordinated functioning of these organ systems. They are able to monitor and provide the feedback necessary to maintain a constant internal environment. Enzyme action is a prime example of the need for this balance. Enzymes control all of the chemical reactions that constitute the body’s metabolism. As enzymes normally function only within a narrow temperature range, even a small rise in body temperature can result in the failure of many of the reactions of metabolism that are essential to life.
This module increases students’ understanding of the applications and uses of biology, implications for society and the environment and current issues, research and developments in biology.

• 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 substrates.

Things to consider:

• What does identify mean?
• What does describe mean?
• Understand what you are going to write before you write your answer down.

All chemical reactions taking place within a cell and all chemical processes within the organism is known as its metabolism. The organism’s metabolism is maintained by special large proteins called enzymes. The role of these enzymes is to catalyse steps in metabolic pathways as well as produce essential molecules for cells. (Maintaining a balance)
Other facts about enzymes:

• They can be used over and over again
• Only small quantities required in cells
• Made by the cell and controlled by nucleus
• Different cells make different enzymes

The major chemical composition of enzymes is proteins. These proteins are made up of amino acids which are joined by peptide bonds. Certain amino acids code for certain proteins. The chemical composition can determine the active site, which binds to the substrate.

Enzymes are highly specific which means that enzymes have a specific substrate and that substrate only can incur a reaction. The models below illustrate enzymes specificity to a substrate.

LOCK AND KEY MODEL
The above model shows that the enzyme is specific for only one type of substrate. The enzyme can only react with a substrate which is the reciprocal to its shape. The substrate binds to the enzyme at the active site whereby a reaction occurs. Once the reaction is complete the enzyme returns to its regular state and two products are formed.
It is called the lock and key model due to the substrate fitting to the enzyme like a key going into a lock.
INDUCED FIT MODEL
The above model shows that an enzyme is adaptable to the shape of the substrate. Once the substrate has attached itself to the enzyme at the active site the reaction occurs and the once complete the enzyme returns to its regular state and two products are formed.
It is called the induced fit model due to the enzyme changing its shape to accommodate the substrate. (Inducing itself)

Identify the pH as a way of describing the acidity of a substrate.

Things to consider:

• What does identify mean
• Be succinct in your answer

The pH scale is a scale which illustrates the hydrogen ion concentration within a substance. Acidity is when a substance has a large amount of hydrogen ions present in solution. Acidic substances fall between the pH ranges of 1 – 7. If a substance is neutral it is said to have a pH of 7. Alkalinity or a base is a substance that contains very little hydrogen ion’s. Basic substances fall between the pH range of 7 -14. If we use this scale we can determine how many hydrogen ions are present in a substrate therefore determining the optimum pH range for an enzyme.

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

Things to consider:

• What does explain mean?
• Underline key words
• Define key words. Know what they mean!

There are three main factors that affect the enzymes there activity and hence metabolic efficiency. These factors are:

• Temperature
• pH
• Substrate concentration

All enzymes have a specific temperature in which they function the best, (optimum temperature.) If the temperature is low enzymes are “sluggish,” and reactions occur at a slow rate. When the temperature increases, reaction rates increase until the enzyme is at its optimum temperature. If the temperature continually increases reactions rates dramatically decrease. This increase in temperature causes the peptide bonds to break, which in turn makes the active site inactive, effectively destroying the enzyme. This process is called denaturation.
All enzymes have an optimum pH. This means that if an enzyme carries a pH level of 6 it needs to be in an environment which has a pH of around 6. Changing the pH slightly will change the enzyme activity, while changing the pH dramatically will cause irreversible changes in the enzyme.
Substrate concentration also affects metabolic activity. If we increase the substrate concentration the enzyme activity increases to a certain point until all active sites are being occupied by a substrate. So how does the substrate concentration stay at a level which enables the enzyme to continually function at the optimum level? Enzymes are continually reacting with substrates to produce a product, these products are then metabolised by another enzyme. A process called feedback regulates enzyme activity, a key factor in metabolic efficiency. Feedback also controls temperature and pH.

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

Things to consider:

• A definition of homeostasis
• What does describe mean?
• Underline key words
• Be succinct in your answer

No matter what is happening on the external environment, the human body is capable of maintaining a constant internal environment. For example our blood sugar remains fairly constant, (90mg/100mL) body temperature (37 degrees Celsius) and pH of the blood (7.38 – 7.42). This constant internal environment is known as homeostasis. Homeostasis is the constant internal composition of a cell or an organism and the mechanisms that maintain it. In simple terms homeostasis is the steady state of an organism. Homeostasis does not merely occur. Certain stimuli that cause an imbalance will in effect illicit a response, in turn returning the organism to its steady state.
OTHER FACTS:

• Idea of homeostasis introduced by Claude Bernard in 1859, did not call the process homeostasis.
• Term homeostasis first coined by Walter Cannon 1929.

Explain that homeostasis consists of two stages:

• Detecting changes from the stable state
• counteracting changes from the stable state

Things to consider:

• What does explain mean?
• Determine the best way to answer the question
• Diagram?

The human body uses the homeostatic response to maintain a balance in a variety of ways including body temperature. The homeostatic system has three main parts; the receptor (detector), the control centre and an effector. The role of the receptor (detector) is to detect changes within the surrounding internal and external environment. These changes are known as stimuli. When and if a change takes place the receptor relays a message to the control centre. The control centre then determines whether or not to illicit a response or maintain the balance. This response or maintaining a balance is carried out by the effector. This process is known as feedback:
Receptor/detector à control centre à effector.
Therefore homeostasis is a two stage process whereby receptors detect changes from the stable state and counteract these changes to return to the stable state. (E.G. shivering/sweating)

 

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

Things to consider:

• What does outline mean?
• What does the nervous system contain?
• Underline key words and be succinct

The nervous system consists of two parts the central nervous system (CNS) and the peripheral nervous system (PNS). The role of the central nervous system is to coordinate all the organisms’ responses. The CNS receives the information, interprets the information and initiates a response. The PNS is a system of nerves that branches out and around the body. These nerves are connected to receptors and effectors. When the PNS detects a stimuli it rapidly relays the message to the CNS and to the control centre to illicit a response.
The endocrine system also plays a pivotal role in maintaining a balance. The endocrine system secretes certain hormones in response to certain stimuli.
E.G. Thermoreceptors detect a change in the surrounding air temperature, (hot). A message from the PNS is relayed to the CNS which in turn interprets the message. The CNS then initiates a response. Effectors start to produce sweat and dilate blood vessels in order to lose heat, and therefore maintain a balance.

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

Things to consider:

• What does identify mean?
• What does compare mean?
• Be succinct, make sure in your answer you include a variety of species

On Earth organisms face a vast variety of temperatures ranging from over 100 degrees to -70 degrees Celsius. All organisms have a certain optimum temperature range. When out of their temperature range the organism risks death or damage to their cells. For example most terrestrial organisms are found to function best between 0 – 45 degrees. Any higher or lower and the organism risks their cells and proteins denaturing, or their cells becoming frozen. In comparison thermoacidophiles love a hot climate around 100 degrees. If the temperature drops below 55 degrees the thermoacidophiles will eventually become inactive and die.  

 

 

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

Things to consider:

• What does compare and explain mean?
• Know the key words in this statement such as ectothermic and endothermic.

AUSTRALIAN ECTOTHERM - ENDOTHERM	RESPONSE TO CHANGE IN AMBIENT TEMPERATURE	EXPLANATION OF CONTROL
Frilled Neck Lizard	Flatten or narrow body shape. (Sunbaking)       Access areas of cooler ambient temperature (Shade/burrows.)     Dormant states of reduced metabolic activity.	Frilled neck lizards will flatten their body to absorb as much sun as possible in order to increase their body temperature. Frilled neck lizards will narrow their body if the ambient temperature is too high or if their own body temperature is too high. This is performed in order to reduce their surface area. Frilled neck lizards move into shades or burrows to cool down from the rising ambient temperature. The temperature in burrows is fairly constant, which enables the lizard to cool down. Burrows in particular also minimise water loss which is beneficial to the lizard. Due to the ambient temperature being too cold frilled neck lizards can go into a state of torpor whereby their body shuts down for the winter and their metabolic rate is slowed.
Kangaroos	Surface area to volume ratio.   Changing patterns in blood flow.       Cooling by evaporation of water.     Fur.         Regulating metabolic rates.	Kangaroos have a relatively large surface area. This larger surface area enables the kangaroo to maintain and lose body heat during periods of high temperatures. Kangaroos have a dense network of blood vessels particularly in their forearms. These blood vessels dilate when the ambient temperature is high. This dilation increases blood flow to the forearms and promotes heat loss. To increase cooling kangaroos lick their forearms. Kangaroos cool themselves by sweating. This evaporation of the water cools the organism down. However in times whereby the kangaroo needs to conserve water it will increase its body temperature a couple of degrees in order to maintain water. Kangaroo’s fur has two main processes when the ambient temperature increases/decreases. When the temperature decreases the fur stands on end in order to reduce heat loss and maintain body heat. When the ambient temperature increases the fur insulates the kangaroo from the hot air surrounding it. Kangaroos regulate their metabolic rates in order to regulate their body temperature. This is done by remaining crouched in the shade during times of extreme heat.

Identify some responses of plants to temperature change.

Things to consider:

• What does identify mean?
• Be succinct

Desert plants or plants which are exposed to high temperatures elicit a few responses due to temperature change. For example due to increasing temperature a desert plant will have smaller leaves which in turn decreases their surface area which leads to a decrease in water loss and solar radiation.
An Australian example where a plant reacts to temperature change is the eucalypt. The eucalypts leaves hang down, vertical in nature. This in turn provides a large surface area for the rising sun, and at this time of the day it is generally cool in nature. When the sun is higher in the sky around midday, the ambient temperature generally increases. At this time the eucalypts leaves are still hanging vertically which in turn reduces the surface area of the leaf as well as maximising water retention. In some very dry and hot conditions the eucalypt may even close its stomates in order to stop transpiration from occurring.
Therefore particularly in Australia there are numerous responses of plants to temperature change.

Identify data sources, plan, choose equipment or resources and perform a first-hand investigation to test the effect of:

• increased temperature
• change in pH
• change in substrate concentrations on the activity of named enzyme(s)

Things to consider:

• What does identify mean?
• This experiment is referred to frequently in past HSC papers. Understand the task when it is performed in class.
• Underline key words and know their definitions.

Part A: The effect of temperature on an enzyme

EQUIPMENT:
You need to know what equipment was used in this experiment, as this dot point asks you to “choose equipment.” Refer to page 274 for the equipment list.

METHOD:
Ensure you have written your own method. This dot point asks you to PLAN your experiment so in the HSC there is no reason why they can’t ask you to re-write the method you followed. Refer to pages 274 – 275 of the textbook.

RESULTS:

• Ensure that you have a table of results
• Construct a graph of your results and answer the following questions.

QUESTIONS:

• From your results which temperature clotted the quickest?
• From your results which temperature clotted the slowest?
• From your results what relationships can you describe between temperature change and enzyme activity. Include possible reasons as to why 10 degrees and 80 degrees did no clot as well as the phrases, “optimum temperature” and “denaturation.”
• What was the purpose of test tube “B?”
• Write down ONE safe working practice you used throughout this experiment.
• Write a conclusion. (Did your experiment answer your aim?)

WRITE UP PART B: EFFECT OF pH ON ENZYME ACTIVITY (Pg 275 – 276). It must be in your own words!

EQUIPMENT:
You need to know what equipment was used in this experiment, as this dot point asks you to “choose equipment.” Refer to page 275 for the equipment list.

METHOD:
Ensure you have written your own method. This dot point asks you to PLAN your experiment so in the HSC there is no reason why they can’t ask you to re-write the method you followed. Refer to pages 275 – 276 of the textbook.

RESULTS:

• Ensure that you have a table of results
• Construct a graph of your results and answer questions 1 – 3 on page 276.

 

 

 

WRITE UP PART C: EFFECT OF SUBSTRATE CONCENTRATION ON ENZYME ACTIVITY (Pg 276 – 277). It must be in your own words! (“PLAN”)

EQUIPMENT:
You need to know what equipment was used in this experiment, as this dot point asks you to “choose equipment.” Refer to page 276 for the equipment list.

METHOD:
Ensure you have written your own method. This dot point asks you to PLAN your experiment so in the HSC there is no reason why they can’t ask you to re-write the method you followed. Refer to pages 276 – 277 of the textbook.

RESULTS:

• Ensure that you have a table of results
• Construct a graph of your results and answer questions 1 – 3 on page 277.

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

Things to consider:

• What does gather, process and analyse information mean?
• What does use available evidence mean?
• Underline key words and be succinct in your answer, if you are unsure of what your answer should be ask another student or the teacher.

 

http://www.unisanet.unisa.edu.au/Information/12924info/Lecture%20Presentation%20-%20Homeostasis.ppt#264,9, Positive Feedback Systems good site

 

 

 

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

Things to consider:

• What does analyse mean?
• What does describe mean?
• What is an adaptation
• Underline key words and be succinct in your answer, if you are unsure of what your answer should be ask another student or the teacher.

ORGANISM	ECTOTHERM or ENDOTHERM	ADAPTATION	DESCRIPTION AND RESPONSE
Pygmy Possum	Endotherm	Fur	The pygmy possum is covered in dense fur. This is due to the fact that the pygmy possum inhabits areas where the ambient temperature is extremely low. The fur enables the pygmy possum to retain body heat and therefore maintain a healthy body temperature.
Red Kangaroo	Endotherm	Dense network of blood vessels in forearms. (Blood flow)	The dense network of blood vessels in the kangaroo’s forearms are an adaptation to the hot dry conditions they experience in Australia. The blood vessels allow the red kangaroo looses body heat from the forearms in hot conditions. For additional heat loss the red kangaroo will lick its forearms in an attempt to cool itself down. This adaptation assists the red kangaroo in regulating its own body temperature.
Blue Tongue Lizard	Ectotherm	Sun baking	The blue tongue lizard will generally sun bake in the sun when its core body temperature needs to be increased. This is due to the fact that the lizard is cold blooded. Due to the body shape of the lizard it will flatten itself out in order to increase its surface area and therefore increase its body temperature. In order to maintain its body temperature the lizard will move out of the sun into the shade. The lizard will repeat this process in order to regulate its own body temperature.

 

 

 

• 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
• other products of digestion

Things to consider:

• What does identify mean?
• Make sure you know all means of transport as the statement is form(s)

SUBSTANCE	FORM(S) IN WHICH IT IS CARRIED IN MAMMALIAN BLOOD
CARBON DIOXIDE (CO2)	Dissolved in blood plasma Bind to haemoglobin. Forming carbaminohaemoglobin. Hydrogen carbonate ions. (HCO3)
OXYGEN (O2)	Oxygen is carried by haemoglobin in red blood cells.
WATER (H2O)	Dissolved in blood plasma.
SALTS	Dissolved in blood plasma.
LIPIDS	Carried in a package called a chylomicron.
NITROGENOUS WASTE	Nitrogenous waste such as urea, uric acid and creatinine is dissolved in blood plasma.
OTHER PRODUCTS OF DIGESTION	Dissolved in blood plasma.

 

Explain the adaptive advantage of haemoglobin

Things to consider:

• What does explain mean?
• Be succinct in your answer

Haemoglobin is an adaptive advantage for organisms that contain haemoglobin in their blood for the following reasons:

• Haemoglobin, the red pigment in all red blood cells, transports oxygen from the lungs to body cells around the body. This in turn allows the organism to carry out certain metabolic functions such as cellular respiration.
• Haemoglobin transports some carbon dioxide from body cells to the lungs. This in turn allows the organism to maintain blood pH as excess carbon dioxide in the bloodstream can alter blood pH and have adverse effects on the organism.
• Each red blood cell contains approximately 280 million haemoglobin molecules. This adaptive advantage indicates that a large proportion of oxygen can be transported within the organism therefore the organism can function at an optimum level.
• The major role of haemoglobin is to transport oxygen. As oxygen is not very soluble in water, (meaning it does not dissolve in water) it therefore does not dissolve in blood plasma. The adaptive advantage of haemoglobin allows four oxygen molecules to bind with the iron ions within the haemoglobin structure. This forms a molecule known as oxyhaemoglobin.

(NOTE THE FOUR OXYGEN MOLECULES ATTACHED TO EACH HAEM UNIT.)

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

Things to consider:

• What does compare mean?
• What is the best way to represent this answer?
• Make sure you know the differences between the relative structures

BLOOD VESSEL	STRUCTURE/FUNCTION	DIAGRAM
ARTERIES	Arteries are composed of three layers; an outer layer of connective tissue, a layer of elastic fibres and smooth muscles and an inner endothelial layer. The elastic fibre/smooth muscle layer is much thicker in arteries compared to other blood vessels as it needs to transport blood around the body under high pressure. This layer enables the artery to stretch at times as well as return to its normal diameter according to blood pressure level.
VEINS	Veins are composed of three layers; an outer layer of connective tissue, a layer of elastic fibres and smooth muscles and an inner endothelial layer. Blood is transported in veins at low pressure. Due to this low pressure, and to prevent back flow of blood, veins have many valves. Valves open and close according to the blood flow. Blood continually flows in veins due to the contraction of surrounding muscles. These contractions also promote the opening and closing of valves.	CONNECTIVE TISSUE ELASTICFIBRES/SMOOTH MUSCLE ENDOTHELIAL LAYER NOTE THE VALVE
CAPILLARIES	Capillaries have a very thin structure to allow the transport of substances between blood and cells. The lumen (hole) is very small, only allowing one red blood cell at a time to move through.	NOTE THAT THE WALL OF THE CAPILLARY IS VERY THIN COMPARED TO THAT OF THE OTHER BLOOD VESSELS.

Describe the main changes in the chemical composition of the blood as it moves around the body and identify tissues in which these changes occur.

Things to consider:

• What does describe mean?
• What does identify mean?
• Understand what it means by chemical composition.

The main changes in the chemical composition of the blood as it moves around the body are due to two systems, the pulmonary system and the systemic system.

In the pulmonary system the blood flows from the heart to the lungs then back to the heart. The flow of blood is at a fast rate and is usually under low pressure. The blood has just returned from the body and contains large amounts of carbon dioxide. This carbon dioxide is then released from the blood into the alveoli of the lungs. Subsequently the carbon dioxide is breathed out. Oxygen, however, is diffused from the alveoli into the red blood cells. This oxygenated blood is then carried back to the heart. Therefore as part of the pulmonary circuit carbon dioxide levels are decreased and oxygen levels increased.

The systemic system pumps oxygenated blood to the rest of the body except the lungs. During this process oxygen is delivered to cells so they can function efficiently, while carbon dioxide is picked up. Urea is also picked up by the blood from the liver and is transported to the kidneys. Products of digestion are also picked up and returned to the liver for metabolising. The deoxygenated blood is then returned to the heart. Therefore as part of the systemic system oxygen levels decrease as it is delivered to certain tissues and cells, carbon dioxide levels increase as they it needs to be removed from the blood, urea levels increase until they are delivered and filtered by the kidneys and products of digestion increase until they are delivered and metabolised by the liver.

 

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

Things to consider:

• What does outline mean?
• What does explain mean?
• Underline key words

Oxygen is a necessity in living cells as it is a requirement for cellular respiration. Respiration is the process by which glucose is broken down using oxygen to produce energy, (ATP). Cellular respiration is outlined below.

Glucose + oxygen → carbon dioxide + water + energy (ATP)

As indicated by the equation above all living organisms require oxygen in order to break down glucose. Oxygen is supplied to cells via the haemoglobin.

It is essential for cells to breakdown glucose in order to obtain energy. However as the equation indicates a by – product of this process is carbon dioxide. Carbon dioxide is no longer required by the cell and must be removed from the cell and tissue in order to maintain a balance. Carbon dioxide is removed by the blood in the body in three main ways, dissolved in plasma, attached to haemoglobin or as hydrogen carbonate ions in plasma. The blood carries these forms to the lungs where carbon dioxide is breathed out. On the other hand if carbon dioxide is not removed there can be severe effects on body chemistry. For example if carbon dioxide is not removed it will affect the pH of blood, this in turn effects the ability of haemoglobin to bind to oxygen, a necessity for cellular respiration. Therefore it is essential that the body maintains a balance by removing all carbon dioxide from cells and tissue.

 

 

 

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

Things to consider:

• What does describe mean?
• Identify the correct theories and identify the characteristics as well as their differences.

The two processes responsible for the movement of materials through plants in xylem and phloem are the transpiration stream in the xylem and translocation in phloem.

BACKGROUND:
Transpiration is the loss of water through the leaves of plants. Water moves up the plant against gravity from the roots to the leaves. This process is known as the transpiration stream. Water enters the plant roots by osmosis and continues to move through the roots cells until it has reached the xylem. There is continual movement of water in xylem due to two reasons:

• There is a continual water potential meaning that water is constantly moving through the root cells due to the concentration gradient. (Moving from high to low.)
• Root pressure pushes the water towards the centre of the plant towards the xylem.

EVIDENCE: Eduard Strasburger’s research supported the transpiration stream hypothesis. He tested 20 meter tall plants and noted that the leaves “pull” water/dissolved nutrients up the plant, not the xylem itself.

The process of transpiration can be outlined below:

• Sunlight gives water molecules near the leaves surface enough energy to evaporate through the stomata. This process is known as transpiration.
• Transpiration causes tension within the xylem column. This tension causes water molecules further up the xylem to attract water molecules below them. This is known as cohesion.
• Xylem tubes are relatively thin. This means that water adheres to the walls of the xylem due to the attraction of water to other molecules. In smaller tubes this is known as capillarity and this also helps drag water up the xylem to the leaves.
• The transpiration stream is also known as the evaporation – tension – cohesion mechanism. Basically leaves lose water due to evaporation. This in turn causes tension further down the xylem. Cohesion then draws up water further down the xylem, eventually to the leaves.
• Therefore water and dissolved mineral ions moves from the roots to the leaves in one direction only due to the transpiration stream.

The process of translocation can be outlined below:

• Translocation is the movement of sugars in the phloem of all plants in any direction. Sugars are always translocated from an abundance of sugar (sugar source) to an area where sugar is required (sugar sink).
• Sugar is made as a product of photosynthesis, in the form of glucose. Sugar can also be stored as starch in cells.
• Complex sugars such as glucose are broken down into simpler molecules such as sucrose. These simpler molecules are much easier to transport, as they are smaller they find it easier to transport across biological membranes.
• Scientists documented the movement of sugars in plants using radioactive dye and carbon – 14. From this research the pressure – flow mechanism was developed.
• Consider the sugar source first. Sugar is loaded into phloem vessels from nearby cells by active transport, (ATP). This increases solute concentration in the phloem which in turn causes water to move into the phloem by osmosis.
• Now consider the sugar sink. Sugar is loaded from the phloem vessels into nearby cells by active transport, (ATP). Water also follows the sugar into the cell by osmosis.
• Now consider the phloem vessel as a whole. At the sugar source there is a large amount of solute and a large amount of water. The large amount of water exerts pressure within the vessel known as hydrostatic pressure. At the sugar sink there is a small amount of solute and a small amount of water. The small amount of water exerts low pressure or low hydrostatic pressure.
• Due to the pressure differences the water flows from high pressure to low pressure carrying the solute and nutrients with it.
• Therefore pressure flow drives the sugars from areas of high concentration (source) to areas of low concentration. (sink)

 

Perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water

Things to consider:

• Underline key words
• Write out an experiment that is controlled as well as an experiment that illustrates validity, reliability and accuracy.
• Identify variables
• Identify safe work practices

PRACTICAL INVESTIGATION

Perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water. (REFER TO PAGES 277 – 278)

AIM:
To investigate the effect of dissolved carbon dioxide on the pH of water.

HYPOTHESIS:
I think that the dissolved carbon dioxide will cause the water to turn acidic.

EQUIPMENT/MATERIALS:

• Solid calcium carbonate (CaCO3)
• Dilute hydrochloric acid (HCl)
• Distilled water
• A 100 mL measuring cylinder
• 2 test tubes
• Cork and bent glass tubing
• Test tube rack
• Universal indicator and a card to check the pH
• Lime water solution (calcium hydroxide = Ca(OH)2
• Straw

METHOD:
COMPLETE PART A FIRST: Detecting carbon dioxide
To ensure that the reaction we are performing contains carbon dioxide we must complete BOTH of the following depending on the reaction we choose:

TASK 1:

1. Using a measuring cylinder measure out 10 ml of limewater (calcium hydroxide) and pour it into a test tube.
2. To a second test tube add some calcium carbonate and hydrochloric acid. Attach a cork and bent glass tube to the calcium carbonate/hydrochloric acid test tube and run this to the test tube which contains limewater. (See figure 1 below.)
3. Observe any colour change in the limewater. If the limewater turns a milky colour there has been a chemical reaction with the limewater and carbon dioxide.

Figure 1: Limewater turns milky due a chemical reaction with carbon dioxide.

TASK 2:

1. Using a measuring cylinder measure out 10ml of limewater and pour it into a test tube.
2. Using a straw exhale into the limewater solution.
3. Observe what happens to the limewater. If the limewater turns a milky colour it means that the limewater has reacted with carbon dioxide, proving that our breath contains carbon dioxide.

PART A PROVES WHETHER OR NOT THE CHEMICAL REACTIONS YOU ARE PERFORMING CONTAIN CARBON DIOXIDE. THIS THEREFORE ENSURES THAT YOUR EXPERIMENT IS ACCURATE.

PART B: Ensure you complete BOTH tasks.
TASK 1:

1. Using a measuring cylinder measure out 10 ml of distilled water and add it to a test tube. Add 2 – 3 drops of universal indicator to the test tube. Using a pH card determine the pH of the distilled water and record your results in the results table below. Place this test tube back in the test tube rack.
2. To a second test tube add a small amount of calcium carbonate.
3. Using the measuring cylinder measure out 10 ml of dilute hydrochloric acid.
4. Add the dilute hydrochloric acid to the calcium carbonate solution and quickly insert the cork stopper and bent glass tubing as indicated by figure 1 above.
5. At every 30 second, for a total of 5 minutes, observe and record the pH change using the pH card in the results table below.
6. Repeat steps 1 – 5 three times to gather reliable results.

 

TASK 2:

1. Using a measuring cylinder measure out 10 ml of distilled water and add it to a test tube. Add 2 – 3 drops of universal indicator to the test tube. Using a pH card determine the pH of the distilled water and record your result in the results table below.
2. Using a straw continually exhale into the distilled water solution for a total of 5 minutes. At 30 second intervals note the colour change. Using your pH card determine the pH of the solution and record your results in the results table below.
3. Repeat steps 1 – 2 three times to gather reliable results.

 

RESULTS:

TASK 1:

pH	TIME (minutes/seconds)
	0	0:30	1:00	1:30	2:00	2:30	3:00	3:30	4:00	4:30	5:00
	7	7	6	6	5	5	5	5	5	5	5

TASK 2:

pH	TIME (minutes/seconds)
	0	0:30	1:00	1:30	2:00	2:30	3:00	3:30	4:00	4:30	5:00
	7	7	6	6	6	5	5	5	5	5	5

Depending on the exam question you may have to draw a graph.

DISCUSSION/QUESTIONS:

Consider the following as part of your discussion:

• Was your experiment accurate?
• What improvements could you make to the experiment? For example weighing out the calcium carbonate solution with a set of scales, having a smaller measuring cylinder in order to obtain a more accurate measurement.
• Are there any safety requirements for this experiment? Goggles?

Questions: Page 278 of the text book.

1a.) What was the effect of carbon dioxide on the pH of water?
The carbon dioxide caused the water to change from its neutral state (pH 7) to a more acidic state (pH 5).
b.) How does pH relate to hydrogen ion concentration?
The pH range directly relates to hydrogen ion concentration. Firstly hydrogen ions cause any solution to be acidic. The purpose of a pH test is to see how many hydrogen ions are present in that certain substance. We can relate this to the pH scale. A substance that has a pH of 1 has a high hydrogen ion concentration. A substance that has a pH of 14 is said to have a very low hydrogen ion concentration. Therefore pH relates to hydrogen ion concentration.
c.) From your knowledge of biology, explain how carbon dioxide changes the pH.
From my knowledge of biology carbon dioxide can lower the pH of the blood. When carbon dioxide diffuses into the bloodstream it reacts with an enzyme known as carbonic anhydrase, which in turn catalyses its reaction with water. (Indicated below)

 

 

 CO2  + H2O                                  H2CO3

Therefore an increase in carbon dioxide leads to an increase in carbonic acid which leads to an increase in hydrogen ions which leads to a decrease in pH which in turn lowers the binding rate of oxygen with haemoglobin.

2a.) What sources of carbon dioxide did you use?
The sources of carbon dioxide we used in this experiment was a chemical reaction between calcium carbonate and hydrochloric acid to produce carbon dioxide and using our own breath/exhaling.
b.) Which of these sources is relevant to body physiology? Explain how it is made in the body.
Our own breathing/exhaling is relevant to body physiology. Carbon dioxide is made in the body as a by product of cellular respiration. Cellular respiration is a process by which glucose and oxygen react to produce carbon dioxide, water and energy usually in the form of ATP. This is indicated below.

Glucose + Oxygen                              Carbon dioxide + water + energy (ATP)

It is important that the body “gets rid” of this waste. This is done exhalation. This in turn maintains a steady chemical state within the human body.
c.) Would the change in pH be dangerous for the body? Explain.
A change in the pH of blood composition would be detrimental to the human body. Excess carbon dioxide causes the bloodstream to turn more acidic, it also affects the binding of oxygen to haemoglobin to drop. Cells require oxygen to respire. If this can no longer occur cells will no longer function. On a larger scale excess carbon dioxide in the body will cause the person to die.
d.) If so, how does the body solve the problem?
The body solves this problem in a simple matter. As carbon dioxide is a waste product of the cell it is quickly diffused into the bloodstream. Carbon dioxide can be carried three ways in the blood; it can be carried dissolved in plasma, as carbonic acid or as carbaminohaemoglobin (attached to haemoglobin). As carbon dioxide diffuses in the bloodstream it is carried via the pulmonary circuit to the lungs. Here the carbon dioxide diffuses into the alveoli of the lungs and is subsequently breathed out.
3. What essential measurement did you have to make before testing the effect of carbon dioxide on the water? Why?
The essential measurement that we took before testing the effect of carbon dioxide was the pH of the distilled water. This was performed to ensure and to illustrate a pH change. If the original pH was not recorded we would not know if the carbon dioxide affected the pH of the dissolved water.
4. Having designed and performed this experiment, what do you think are the key points about it – assume you are explaining it to another student who has not done it before.
The key points from this experiment would be:

• Carbon dioxide does effect the pH of water
• We ensured that our chemical reactions were producing carbon dioxide. This was illustrated by testing our experiments with limewater which turns milky in the presence of carbon dioxide.
• This experiment can be linked to the human body.
• We repeated the experiment and got similar results. (Reliability)

CONCLUSION
The experiment performed illustrates that carbon dioxide has a direct effect on the pH of distilled water. This fact can be linked with the human body. We know that the pH of the human blood is in a narrow range being 7.35 - 7.45. This pH range is similar to that of the distilled water. The experiment therefore shows what could happen if carbon dioxide levels were too high in the bloodstream.

 

Perform a first-hand investigation using the light microscope and prepared slides to gather information to estimate the size of red and white blood cells and draw scaled diagrams of each

Things to consider:

• Before undertaking this experiment ensure you can estimate the size of red and white blood cells. There is no point performing this experiment if you can not calculate the size of the cells.
• Refer to pages 278 – 279 of the text book.

• To perform this experiment accurately you need to refer to the method on page 278 – 279 of the text book.
• The method tells you exactly what to do as well as how to measure the size of red and white blood cells. Ensure you know how to calculate the and draw a scaled diagram of red and white blood cells because there is no reason why in the HSC they can’t ask you to draw a scaled diagram or calculate the size of the cell based a diagram they give you.
• According to https://histo.life.uiuc.edu/histo/lab/lab1/text.htm red blood cells are 6 – 8 micrometers (µm) and white blood cells vary from 6 – 12 micrometers (µm).

 

 

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

Things to consider:

• What does analyse mean?
• What does identify mean?
• What does describe mean?
• What does explain mean?
• Ensure you account for all the verbs in your answer.

The two main current technologies that allow measurement of oxygen and carbon dioxide concentrations in blood are the blood gas analyser and the pulse oximeter. Their function(s) are outlined below.

BLOOD GAS ANALYSER and CONDITIONS WHERE IT IS USED

PULSE OXIMETER and CONDITIONS WHERE IT IS USED

Invasive technique. (Goes inside the body) Takes small samples of arterial blood. The analyser measures the oxygen using two electrodes. Oxygen diffuses through a membrane between the two electrodes. This produces a small electric current. This current is proportional to the amount of oxygen. E.G. certain values equal certain amounts of oxygen. Carbon dioxide levels are also measured by placing the blood specimen in one chamber and the other chamber a hydrogen electrode. Dissolved carbon dioxide diffuses into the hydrogen ion chamber. The pH is then measured. The hydrogen ion concentration is proportional to carbon dioxide levels. E.G. certain values equal certain amounts of carbon dioxide. Alternatively instead of taking a blood sample an arterial probe, which is inserted into the body, may take these measurements. Blood gas analysers are commonly used in intensive care units especially baby care units and labour wards. This is due to the fact that slight changes in carbon dioxide levels can affect the development of newly born babies. Excess carbon dioxide and poor oxygen saturation levels can have detrimental affects on the child. The analyser is used as a measuring tool to ensure the patient is looked after and if oxygen/carbon dioxide levels change a nurse/doctor can take necessary action to return oxygen/carbon dioxide levels to their optimum values.

The pulse oximeter is a non – invasive technique which measures the concentration of oxygen in the body. The device is either attached to the finger or ear lobe of the patient, which measures oxygen saturation with haemoglobin and pulse rate. The oximeter works in the following way: a light source passes through the blood. Different amounts of light are absorbed depending on the degree of saturation of oxygen to haemoglobin. A processor then calculates the light absorption rate and converts this to saturation of haemoglobin. Oximeters are used in many hospital situations even though they do not measure carbon dioxide levels. They are used as monitoring units during anaesthesia. They are very efficient because they can be used during surgery or after surgery to monitor oxygen saturation, pulse rate and blood flow. Oximeters can be used in the success of ventilation procedures, to see if the administration of oxygen is successful for the patient. Oximeters can also be used in intensive care units or after surgery to monitor unconscious patients and to notify nurses/doctors of any changes in oxygen levels. Therefore oximeters are an efficient monitoring system for oxygen, pulse and blood flow levels.

 

 

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

• What does analyse mean?
• What does discuss mean?
• What does identify mean?
• Determine whether the products from donated blood are a benefit or not.

The main products extracted from donated blood are:

• Red blood cells
• Platelets
• Plasma

These products are spun in a centrifuge to separate them into different products. Further products can be extracted from the plasma. The uses and further products that can be extracted are outlined by the table below:

BLOOD PRODUCT	USE/TREATMENT
Whole Blood	To replace large amounts of blood from sever injury.
Red Blood Cells	Given to patients suffering from anaemia, (iron deficiency in the blood) and in cases of severe bleeding.
White Blood Cells	Given to patients with a low white blood cell count or in cases of severe bacterial infection.
Plasma	Given to patients after trauma, or following after a surgical procedure.
Platelets	Given to patients with severe haemorrhaging (bleeding) or bleeding due to diseases such as leukemia.
Cryoprecipitate (contains blood clotting factors)	Given to patients suffering from haemophilia A. Alternatively severe bleeding.
Prothrombinex – HTTM (contains concentrated clotting factors.)	Given to patients with specific bleeding disorders. These specific disorders pertain to patients who are missing certain clotting factors.
Biostate (contains factor VIII clotting factor)	Given to patients with haemophilia B.
Monofix® - VF (contains Christmas factor)	Given to patients with haemophilia B
Thrombotrol® - VF	Given to patients in situations whereby their blood is clotting too quickly.
Albumin	Administered to patients who are suffering from burns, shock due to blood loss and kidney/liver diseases.
Intagram® P	Given to patients who suffer from immune disorders such as AIDS, this in turn reduces susceptibility to infections.
Hyper – immune globulins (contain – antibodies)	Given to patients to treat and/or prevent specific infections such as tetanus or chicken pox.
Rh(D) immunoglobulin (Anti – D)	This product prevents haemolytic disease in newborn babies of Rh negative babies. Haemolytic disease basically pertains to the mother producing certain antibodies that destroy the baby’s red blood cells.

 

 

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

Things to consider:

• What does present mean? Choose whatever means you think is appropriate for this set of information.
• Break to question into two parts.
• In the second half of your answer refer reliable resources as to why artificial blood requires further research

As stricter controls arise from blood donations, scientists have concentrated on developing a synthetic blood known as artificial blood. Research so far has highlighted the importance of carrying oxygen in the blood. Scientists have therefore concentrated on developing artificial blood that mimics the characteristics of real blood. The main areas of research into artificial blood so far are haemoglobin and perfluorocarbons.
Haemoglobin has been extracted from organisms such as cows and humans and has been used in the free state. This means that only the haemoglobin molecule has been used, no the whole blood product. Problems have arisen from using the haemoglobin molecule from other organisms. These include; the instability of the molecule itself, the molecule having a high affinity to oxygen (meaning it binds lots and lots of oxygen) but the inability to let the oxygen molecules go, (into tissues and cells) and the damage it causes to the kidney in its filtration products. These problems are continually researched to the extent that scientists have chemically changed the haemoglobin molecule to yield better results.
Perfluorocarbons (PFCs) are an advantageous alternative because oxygen is approximately 100 times more soluble in perfluorocarbons compared to that in blood plasma, which is about 1 percent. However the problem with PFCs is that they are not soluble in aqueous solutions meaning they can not dissolve in blood plasma. To overcome this problem scientists have added an emulsifying agent to the PFCs. This agent enables the PFC to form an emulsion when it is joined with the plasma. The first trial of emulsified PFC was called fluosol. This trial was unsuccessful as oxygen yields were poor. Subsequently further research has led to better emulsion technology. Scientists have developed a greater emulsified PFC which has a greater oxygen dissolving capacity.

It is only early days when it comes to artificial blood. Currently scientists have only developed “parts” of the blood (haemoglobin and perfluorocarbons) and used them as substitutes. These substitutes only account for the oxygen carrying characteristics of blood. Scientists are yet to create a whole artificial blood component which accounts for all characteristics of blood. Further research is needed in the development of artificial blood for the following reasons:

• It enables hospitals to have an ample supply of blood, not merely the blood supplied by donors.
• It can be used as a treatment tool. E.G. to increase oxygen carrying levels in the blood.
• Universally if it is successful donations would not be required.
• It could be mass produced
• Used in emergencies
• Maintaining organs before transplant

These reasons outline the prospects of further research and development of artificial blood and its benefits.

 

Choose equipment or resources to perform a first-hand investigation to gather first-hand data to draw transverse and longitudinal sections of phloem and xylem tissue

Things to consider:

• Choose your own resources for this experiment.
• Decide what data you need to collect in order to draw a transverse and longitudinal section of phloem and xylem tissue.

• To perform this experiment accurately you need to follow the method on page 279 of your textbook; titled: Investigation 4 – Microscope Examination of Phloem and Xylem.
• You must draw a longitudinal section and transverse section of phloem and xylem tissue. A longitudinal section is the equivalent of a SIDE VIEW. A transverse section is the equivalent of a TOP VIEW.
• You need to know the difference between side views and top views because in last years HSC they had a diagram of a longitudinal section of a plant and students had to identify the structure(s) of the plant.

 

Transverse section (top view) of a plant cell. Note the xylem which looks like a big x. The phloem bundles are indicated by the‘s.’

 

Longitudinal section (side view) of a plant cell. The xylem and phloem are indicated by different stains. Pink = xylem Black/purple = phloem.

 

• 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.

Things to consider:

• What does explain mean?
• Break down the question so you understand what it is asking.
• Underline/understand key words, such as optimal.

Water makes up a large proportion of all living things. The concentration of water in cells should be kept within a narrow range for the following reasons:

• It is an excellent solvent which means it can break down or suspend complex organic and inorganic molecules such as sugars in solution. Too much or not enough water can lead to slower reactions.
• For larger molecules such as proteins water acts as a hydration layer preventing the protein from breaking down. This is called a colloid.
• Water needs to be within a narrow range of concentration (Osmotic Balance) in order for cells to function efficiently. Too much water within the cell (hypotonic) causes the cell to swell and burst. Not enough water within the cell (hypertonic) causes the cell to shrivel. The correct concentration is called isotonic where the normal concentration of water is the same out of the cell as it is in the cell.
• Water is a lubricating substance. Right concentrations leads to the production of substances such as mucus.
• Water is important in metabolism. E.G. Hydrolysis.
• Water is the major transport medium for products around the body.
• Water plays an important role in maintaining body temperature.
• Water has a cushioning effect for the body.

From the points above it is necessary for water to be at its optimum level in order for chemical reactions and certain functions to take place. If this level is uneven reactions are too slow, cells becomes damaged (shrivelled/lysed) or reactions do not take place at all.

 

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

Things to consider:

• What does explain mean?
• Underline key words
• Metabolic????

The removal of wastes is essential for continued metabolic activity for the following reasons:

CAUSE

EFFECT

Wastes affect enzyme activity.   Damage to cellular components.       Excess Hydrogen ions.   Excess ammonia, urea, toxins and drugs.

Optimum enzyme activity not reached. Enzymes not catalysing reactions. Disrupts metabolism. Organelles damaged to the extent that they no longer function. Damage to organelles cause organelles to illicit no/incorrect response. Excessive damage may cause cell death. Makes surrounding ion increase in acidity. This in turn affects the reaction rate of enzymes and the saturation rate of haemoglobin. Brain associated problems.

 

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

Things to consider:

• What does identify mean?
• Underline key words → role?
• Be succinct; maybe use a table to represent your information.

•  

ORGANISM	ROLE OF THE KIDNEY
FISH	The main role of the kidneys is osmoregulation. Osmoregulation is the regulation of salt and water concentrations in the body. Fish excrete nitrogenous wastes across the gills. The kidneys adjust the level of water and mineral ions within the body in order to maintain a balance of internal fluid within the cells.
MAMMALS	Regulate the internal salt and water concentrations of the body. To excrete urea and nitrogenous waste.

 

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

Things to consider:

• What does explain me?
• What is diffusion and osmosis?
• Underline key words, understand the question

The processes of diffusion and osmosis are inadequate in removing nitrogenous waste in many organisms. Firstly diffusion and osmosis are slow processes. In order for organisms to function efficiently the quick removal of nitrogenous waste is a necessity. Diffusion and osmosis do not offer an efficient and fast removal system of nitrogenous wastes. Secondly nitrogenous wastes are predominately made up of large complex protein molecules. These molecules need to be broken down by the liver into simpler products such as urea. (This process is known as deamination.) Once broken down into simple substances diffusion may take place usually within the kidney, due to the nature of smaller molecules. Thirdly osmosis is the transport of water across a semi-permeable membrane. As nitrogenous wastes are a waste product they are not made up of water. Only products of metabolic reactions within the body that produce water would require osmosis. Therefore diffusion and osmosis are inadequate in removing dissolved nitrogenous waste.

 

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

Things to consider:

• What does distinguish mean?
• Ensure you relate these terms to only the mammalian kidney.
• Be succinct

PASSIVE TRANSPORT	ACTIVE TRANSPORT
The net movement of substances that does not require any cellular energy. Movement of substances is from high concentration to low concentration.	The net movement of substance requires cellular energy to be expended. Movement of substances is against the gradient meaning movement is from a low concentration to a high concentration.

Passive and active transport play an important role in the mammalian kidney. Filtration and reabsorption occur in thousands of tiny units known as nephrons. It is in these nephrons that active and passive transport take place. Active transport occurs in the proximal tubule, the ascending loop of henle and the distal tubule. It is at these areas that important nutrients are filtered and reabsorbed. Passive transport occurs in the proximal tubule, the descending loop of henle, the ascending loop of henle, the distal tubule and the collecting duct. Passive transport plays an important role in the mammalian kidney in removing waste and reabsorbing essential nutrients. (See diagram.)

 

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

Things to consider:

• What does explain mean?
• What is filtration and reabsorption?
• What is the nephron?
• Refer answer back to question.

Filtration in the mammalian nephron regulates body fluid composition in the following ways:

• Blood crosses from the glomerulus to the Bowman’s capsule by the process known as filtration.
• Blood pressure forces small molecules such as urea, amino acids, salts and water across and into the capsule.
• Blood cells and proteins are too large and are filtered out.
• When small molecules are filtered across they form glomerular fluid.

Filtration is essential in the mammalian kidney as it controls what molecules enter the nephron as well as regulating glomerular fluid composition.

Reabsorption in the mammalian nephron regulates body fluid composition in the following ways:

• Essential molecules in the filtrate are reabsorbed in the blood in the proximal and distal tubules. (Glucose, amino acids, salts and water.)
• Toxins are absorbed from the blood and secreted.
• Maintains a constant concentration of essential metabolites.

Reabsorption is essential in the mammalian kidney as essential metabolites are reabsorbed back into the blood stream. If this did not occur large portions of these metabolites would be secreted leaving the body unbalanced. Reabosrption maintains homeostasis within the kidney reabsorbing nutrients from the filtrate and secreting toxins.

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

Things to consider:

• What does outline mean?
• Know and understand the difference between aldosterone and ADH.
• Relate these hormones to salt and water.

ALDOSTERONE

ADH (Anti – Diuretic Hormone)

Aldosterone is one mechanism that controls glomerular blood pressure. Aldosterone is found in the adrenal cortex, above the kidney. The primary function of aldosterone is to regulate the salt levels in the blood. This is done by increasing the reabsorption of sodium ions in the loop of henle and the distal tubule. This therefore regulates the concentration of sodium in the blood and body fluids. Sodium ions enter the blood at the distal tubule. Water then follows by the process of osmosis. Water and sodium increase blood volume and therefore blood pressure. Aldosterone conserves sodium ions. Maintains blood pressure. This process enables for glomerular filtration to function efficiently.

ADH prevents water from being lost in the urine. (Diuresis) Its function is to make the collecting ducts more permeable so that water can be reabsorbed back into the blood and body tissues. ADH is released by the hypothalamus (brain.) Receptors in hypothalamus detect lowered water levels in the blood. ADH is then released. ADH then targets the collecting ducts. Collecting ducts become more permeable. Water retention is increased. When there is too much water, or low solute concentrations water needs to be excreted. Therefore less ADH is released.

 

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.

Things to consider:

• What does define mean?
• What does discuss mean?
• Underline key words
• Split the question into two separate parts. One for definition the other for discussion.

Enantiostasis is the maintenance of metabolic and physiological functions in response to variations in the environment. (Aubusson et al 2004) Enantiostasis is important for estuarine organisms in order to maintain appropriate salt level concentrations as their surrounding environment constantly varies in its salt and water concentration.

Marine fish and fresh - water fish are constantly maintaining their internal environment according to their external environment. Marine fish drink large amounts of water and excrete small amounts of concentrated urine. Fresh – water fish gain large amounts of water so they excrete copious amounts of dilute urine and absorb salts across the gills. As both marine and fresh – water fish regulate salt and water between their internal and external environments they are known as osmoregulators, meaning their internal environment differs to that of their external environment.

Another group of fish called the osmoconformers maintain their internal fluids at approximately the same concentration as their external environment.

In an estuarine environment the concentration of salt and water is constantly changing due to the changing of the tides. However many organisms whom live in this estuarine environment survive. These organisms are able to tolerate a range of salt concentrations. Crabs and sharks are osmoconformers who can tolerate large changes in salt concentrations. This is due to the fact that they use a small organic molecule to vary the concentrations in their cells to match the environment. Therefore it is important for osmoregulators and osmoconformers to maintain appropriate salt concentrations within their body as it maintains metabolic function.

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

Things to consider:

• What does describe mean?
• Underline key words
• Understand what the question is asking before you write an answer.

AUSTRALIAN PLANT	ADAPTATION
Banksia	A range of banksias contain woody fruits. These woody fruits are fire resistant enabling the banksia to survive tough dry seasons. The fruit is not fleshy which also enables the banksia to reduce water loss.
Hakeas	The hakea has an unusual adaptation in that it has sunken stomates. The stomates allow humid air to be concentrated above the stomate in turn reducing water loss.
Baobab	The baobab tree has a unique storage system. A baobab will store a large proportion of its water in the trunk, and sometimes the leaves. This allows conservation of water.
Eucalypt	Eucalypts have a variety of adaptations one of them being vertically hanging leaves. This allows the leaf to reduce its exposure to the sun and hence reducing water loss.
Mulga	The mulgas structure is unique as the stems and leaves are shaped in such a way that water runs down their surface towards the root of the plant, therefore optimising water consumption.

 

Perform a first-hand investigation of the structure of a mammalian kidney by dissection, use of a model or visual resource and identify the regions involved in the excretion of waste products.
Things to consider:

• What does identify mean?
• Underline key words that inform what your answer should require.
• Reference 279 – 280

 

Renal Medulla – Contains thousands of filtration units called nephrons.
Renal Cortex – Outer protective layer of the kidney.
Calyces – Individual tubing that connects to every medulla. The word calyces refers to the opening (hole) of the tube.
Ureter – The tube that collects all the urine and passes the urine to the urinary bladder.

 

 

 

 

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

Things to consider:

• What does gather, process, analyse and compare mean?
• Be succinct
• Ensure you know what dialysis is.

RENAL DIALYSIS

MAMMALIAN KIDNEY

Patients blood is past through a tube. This tube is separated from the dialysis tubing by a semi-permeable membrane. The dialysis tubing contains molecules and ions that are essential for the human body at the right concentration. Therefore only wastes such as urea pass through the membrane into the dialysis tubing. No reabsorption. ONLY filtration occurs in dialysis. Process takes 4 – 6 hours. Wastes are removed, dialysis fluid is discarded and blood which has been filtered returns to the body through a vein.

Blood is filtered through millions of nephrons. Nephrons contain membrane which is permeable to essential and non-essential wastes. Concentrations of essential molecules vary from person to person. Essential molecules are either passively or actively transported in or out of the nephron at the proximal tubule, the distal tubule and the loop of henle. Wastes pass through the nephron into the collecting duct and eventually into the bladder. Filtration and reabsorption occur in the kidney Process varies in time depending on the need for nutrients or for the removal of waste. Waste is removed in the form of urine. Filtered blood is returned to the body via the renal vein.

 

 

 

 

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

Things to consider:

• What does present mean?
• What does outline mean?
• Underline key words?
• What is the question asking?

People who do not secrete or secrete insufficient amounts of the hormone aldosterone usually suffer from the disease known as Addison’s disease. Addison’s disease is an inability of the adrenal cortex to secrete sufficient amounts of hormone, in this case aldosterone.

People who can not secrete aldosterone in sufficient amounts undergo hormone replacement therapy. The purpose of this therapy is to replace the hormone aldosterone. This is performed by the patient who takes a mineralocorticoid known as fludrocortisones (Florinef) orally once a day. People who suffer from Addison’s disease are also encouraged by their doctor to increase their salt intake.

If a patient has an Addisonian crisis, which can be life threatening, the patient is administered with hydrocortisone injections, saline solution and dextrose. Usually the patient recovers and is returned to their usual therapy which is fludrocortisones tablets.
Therefore it is important for patients who suffer from aldosterone secretion inefficiency to partake in hormone replacement therapy.

 

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

Things to consider:

• What does analyse mean?
• What does compare and explain mean?
• What would be a good way to present this information?

 

ORGANISM	URINE CONCENTRATION (CONCENTRATED/DILUTE)	EXPLANATION
Terrestrial Mammal	Concentrated	A terrestrial mammal’s urine is usually concentrated. This is due to the lack of water in its surrounding environment. This in turn causes the mammal to secrete concentrated amounts of urine and maintain a water and salt balance.
Marine Fish	Concentrated	A saltwater fish continually drinks water to avoid water loss from its body. The water is absorbed into their body while the salt is actively secreted by the gills and the kidneys. This results in the fish secreting concentrated amounts of urine. Therefore maintaining its water.
Freshwater Fish	Dilute	A fresh – water fish always excretes copious amounts of dilute urine. This is due to their surrounding environment. (Large amounts of fresh water) This causes their urine to be extremely dilute.

 

 

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.

Things to consider:

• What does explain mean?
• Underline key words?
• Be succinct. Understand what the question is asking so that you can answer the question correctly

ORGANISM	TYPE OF NITROGENOUS WASTE	HOW THIS CONSERVES WATER
Grasshopper	Uric Acid which is a paste like substance. Organisms which excrete uric acid are called uricotelic organisms. E.G. Insects and birds.	Grasshoppers contain tube like extensions in their digestive system called Malphigian tubes. Wastes and salts diffuse into these tubes and are followed by water through osmosis. The tubes increase the surface area for the transport of wastes into the digestive system. By the time the nitrogenous waste gets to the rectum most of the water and other important solutes have been returned to the blood. Products that are no longer needed by the insect are excreted in a dry paste form known as uric acid. This adaptation has led to the survival of the species within Australia’s harsh arid conditions.
Kangaroo	Main type of nitrogenous waste is urea in the form of urine. Organisms that mainly excrete urine are known as ureotelic. E.G. Most mammals.	Ammonia and other complex molecules are initially broken down in the liver into simpler substances, in this case urea. Urea is then transported to the kidney to be filtered. The kangaroo’s kidneys are unique as they enable the excretion of concentrated urine and the reabsorption of water. This in turn conserves water for the kangaroo. This adaptation has led to the survival of the species within Australia’s harsh arid conditions.

Other information:

• Fish excrete ammonia.
• Due to their surrounding environment the ammonia is easily broken down.
• These organisms are known as ammonotelic.

 

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

Things to consider:

• What does process mean?
• What does analyse mean?
• What does discuss mean?
• Read and re-read the question until you understand what the question is asking.

Mangroves play an important role in the life of an estuary. The majority of Australian waters contain mangroves. These mangroves are well adapted to survive within their ecosystem. This is due to many ingenious adaptations which enable the different species of mangroves to cope with varying salt and oxygen levels. All mangroves have adapted for the lack of oxygen within the soil. You may have seen the small protruding stumps that surround mangroves. These are called pneumatophores and their role is to absorb oxygen from the air. Mangroves in general have also adapted to the range in salt levels within their environment. The following are some different species of mangroves and their processes used for salt regulation:

The Grey Mangrove: The Grey mangrove (Avicennia marina) has special tissues in their roots and lower stems which prevent the uptake of salt but increase the uptake of water. This process is known as exclusion as the grey mangrove excludes the uptake of salt.
The River Mangrove: The River mangrove (Aegiceras corniculatum) is able to concentrate and excrete salt through special glands on the leaves. The salt then begins to build up on the outside of the leaf where it washed off the leaf during periods of rain. This process is known as secretion as the river mangrove secretes the salt out of their leaves.
The Milky Mangrove: The Milky mangrove (Excoecaria) accumulates salt in older tissues such as leaves, which is then discarded. This process of salt regulation is known as accumulation and it enables the Milky mangrove to accumulate large amounts of salts and then discard the large amounts of salts therefore maintaining a healthy level of salt.

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

Things to consider:

• What does perform mean?
• What does gather mean?
• Ensure you draw/outline the structures in plants that assist in the conservation of water.

• State an aim for this experiment.
• Copy out the materials and method on page 280 of the text book.
• Answer questions 1 – 3 on page 280 of the text book.
• Ensure you can identify and describe different adaptations in Australian plants that enable the conservation of water, for example the shape of eucalypt leaves and the way they hang.
• If you are unsure of certain adaptations refer to table 5.15.1 on page 270 of the text book.