1. Most organisms are active in a limited temperature range. 1.a) ENZYMESWhat are they?• Proteins which speed up chemical reactions (biological catalysts).
• They’re not used up in reaction (remain unchanged → can be reused).
How do they work?• Enzymes bind to substrates (the reactants) and transform them into products (they can either build substrates up into a new product or break one substrate down into many products) → this occurs on the ‘active site’ of the enzyme → the product is then released.
What does ‘specificity’ of enzymes mean?• Each enzyme typically only acts on ONE substrate i.e. each enzyme is specific to one substrate (the shape of the enzyme will match the shape of the substrate).
What factors affect enzyme activity:• Temperature
• pH
• Substrate concentration
*if these factors are not maintained within a narrow range, the enzymes will be
denatured (essentially killed – they can no longer function and the organism will die).
Models of enzyme activity• Lock and key model
-the shape of the enzyme’s active site will fit the shape of the substrate like a lock fits a key (→ shows specificity of enzymes).
-active site is rigid (shape does not change).
• Induced fit model
-enzyme’s active site is not entirely rigid (slightly altered to allow stronger bond between enzyme and substrate).
Lock and key model diagram:
1.b) HOMEOSTASISWhat is it?• The maintenance of an organism’s relatively stable internal environment.
• Controls body temp, blood pH, water/salt conc. etc.
Why is it important?• Enzymes can only function within a narrow temp/pH/substrate conc. range → if internal environment maintained, this allows optimal enzyme function → chemical reactions in body can occur at normal rates → optimal metabolic efficiency achieved.
How does it work?• Homeostasis is achieved via a process called
negative feedback: a corrective response which reduces/opposes changes to the internal conditions of an organism’s body in order to re-establish a homeostatic state.
• It occurs via 2 stages:
1. Detecting the change from the stable state
-receptors detect changes (stimuli) and send message to central nervous system (CNS – brain/spinal cord).
-e.g. detecting an increase in body temp.
2. CNS determines a response, and sends instructions to effectors (muscles and glands) → these carry out the response
-e.g. blood vessels dilate (come closer to surface) + sweat glands stimulated → body temp. cools to normal levels.
1.c) THE ROLE OF THE NERVOUS SYSTEMWhat is it?• The nervous system
coordinates the negative feedback system, which ultimately allows homeostasis to occur. So think about it like this:
negative feedback process (coordinated/carried out by nervous system) → homeostasis (a balanced internal environment within an organism i.e. ideal temp, pH levels etc.)
How does the nervous system coordinate the negative feedback system?• Via the stimulus → response pathway.
STIMULUS: any change in internal environment that is detected by receptors
e.g. increased body temp.
RECEPTOR: detects the change in the internal environment and sends message to CNS.
e.g. increased body temp. detected by hypothalamus in brain.
CENTRAL NERVOUS SYSTEM (CNS): made up of the brain + spinal cord, processes info about the stimulus and determines the response, sending it to effector.
MESSENGER: Motor nerves carry this info from the CNS to the effector.
EFFECTOR (muscle or gland): Receive instructions and carry out a response
e.g. sweat glands produce sweat to cool the body.
RESPONSE: a change within the body as a result of the initial stimulus
e.g. body temp is reduced.
1.d) RESPONSES OF AUSTRALIAN ECTOTHERMS AND ENDORTHERMS (TEMP. REGULATION)What is an ectotherm? • An organism whose internal body temp. is regulated by the external environment → greater fluctuations in body temp (so if it’s cold outside, their internal body temp. will generally be pretty low too).
• E.g. reptiles, amphibians, fish.
What is an endotherm?• An organism whose internal body temp. is regulated by internal body processes i.e. they generate heat from body metabolism (so whether its hot or cold outside, their internal body. temp. stays relatively constant → for humans, this is about 37 degrees).
• E.g. birds & mammals only.
What are some different types of adaptations organisms can have?• Structural - any physical characteristics
e.g. extra fat or feathers for insulation, being a certain colour to blend into the environment and hide from predators.
• Behavioural – the way an organism acts
e.g. bilbies are nocturnal (this way they can sleep during the day when it’s really hot, and be active during the cooler temp. at night).
• Physiological – the way an organism’s body functions – this means specific internal bodily processes
e.g. rate of metabolic activity (some organism’s hibernate, slowing their metabolic activity → conserves energy during cold winter months when food may be difficult to find, and then they are active during the warmer months).
Examples of how some plants respond to temperature changes?• Eucalypts (how they conserve water in hot temperatures)
-Change the orientation of their leaves so that they hang vertically downwards → reduces surface area of the leaf exposed to the sun.
-Remember, leaves lose water via the
stomata (little pores on the leaf’s surface), so if less stomata are exposed to the sun, less water will evaporate from the leaf i.e. more water conserved.
• Banksias
-During extremely hot temperatures (mostly bushfires), seed dispersal is triggered → new seeds fall on cleared, nutrient rich soil → new plants grow.
2. Transport in a fluid medium2.a) BloodFor this area, you need to know the 4 main components of blood, and each of their functions:
2.b) Forms in which substances are carried in the bloodAgain, this is just a bit of memorising, but still important (especially for multiple choice questions!)
2.c) Haemoglobin What?• A molecule found in the
red blood cells of humans → can combine loosely with oxygen molecules (to transport oxygen throughout the body to where it’s needed).
How?In high oxygen environments, the 2 will combine to form oxyhaemoglobin, so the area’s oxygen levels do not become too high.
In low oxygen environments, haemoglobin will release the oxygen it is carrying so that the area can have the oxygen it needs.
What are the ‘adaptive advantages’ of haemoglobin?2.d) Blood vessels2.e) Changes in the composition of blood as it traves around the bodyFor these 2 points, look here for my detailed study notes.
2.f) What is the need for oxygen in living cells, and why is the removal of carbon dioxide essential?Recall: glucose + oxygen → water + CO2 + energy (ATP)Oxygen?• We need oxygen for aerobic respiration. This is a process by which the cells in our body obtain energy from glucose (i.e. sugar) → this energy is necessary for all life-sustaining processes within our body that ensure we can survive.
*note: respiration CAN occur without oxygen (this is called
anaerobic respiration) BUT this is much slower and does not produce as much energy.
Carbon dioxide?• When cells are undergoing respiration, they produce carbon dioxide as a waste product.
• When carbon dioxide in present in cells, it reacts with water in the cells to form carbonic acid → this lowers the pH of cells (makes it more acidic) → a build up of this is toxic, because it will disrupt the homeostatic balance of the body (enzymes won’t be able to function properly anymore and the organism will be unable to survive!).
• Therefore, carbon dioxide needs to be removed to ensure all bodily processes can occur optimally.
2.g) Measuring blood gases with technologies
2.h) Blood donation
2.i) Artificial blood
2.j) Movement of materials in xylem and phloemThese are pretty detailed areas, so look to my study notes for the information.
3. Regulation of waste products3.a) WaterWhat is osmoregulation?• The regulation of water concentration within the body to maintain homeostasis.
Why do we need water in our body?• It’s a solvent! This means it can act as a transport medium for dissolved vitamins, minerals, nutrients, and wastes.
• It keeps cell membranes moist, which is necessary for the diffusion of materials into and out of cells e.g. efficient gas exchange.
• It also helps maintain our body temp. through cooling processes like sweating.
3.b) Removal of wastes + why it is essential for metabolic activityHow are wastes produced in the body?• Metabolic activity involves all the chemical reactions that take place within an organism → these produce wastes, which are toxic and need to be removed (otherwise will build up and kill cells).
How are wastes removed from the body?•
Excretion is the process by which metabolic wastes are removed from the body – this includes excess water, salts, carbon dioxide and nitrogenous wastes.
•
The main organs of excretion are the lungs and the kidneys.
Here are some examples of common metabolic waste products, why they need to be removed and how they are removed by the body:
3.c) Why diffusion and osmosis are not enoughWhat is diffusion?• The passive movement of any molecule along a concentration gradient (from a region of high concentration to a region of low concentration), until equilibrium is reached.
What is osmosis?• Osmosis is just the diffusion of water, so the molecules moving along the concentration gradient are water molecules.
How do unicellular organisms use diffusion and osmosis to survive?• They use these processes to remove metabolic wastes.
• This works because of 2 factors which make diffusion + osmosis effective:
1.They are small in size (have a large SA:V ratio).
2.They are in close contact with their external environment.
Some important facts about these processes:• They’re
passive movements, meaning they require no energy input from the organism. However, this means the process is quite
slow.It’s because of these reasons that diffusion + osmosis are not enough to sustain
multicellular organisms:Diffusion:
too slow + not all wastes would be removed.Osmosis:
too much water may be lost in urine + wastes may become too dilute for excretion.So what’s the solution?• Multicellular organisms require
active transport to remove their metabolic wastes.
• Active transport is
faster + more efficient BUT it requires energy input from the organism (e.g. glucose) → comes from food.
How do multicellular organisms use active transport?• They have specialised organs e.g. lungs, kidneys that do this.
3.d) The kidneyThe kidney can be a bit confusing and complicated, but if you read over the information a few times and use the diagrams, you’ll get it in the end. So please look over to my detailed notes for this section.
These notes include:
• Filtration + reabsorption in the nephron (active + passive transport)
• Prac: kidney dissection
• Regulation of water + salt level in the blood (hormone control of ADH + aldosterone)
• Addison’s disease
• Role of kidney + urine concentration
• Nitrogenous wastes (and their conservation/excretion in Aus. insects + mammals)
• Renal dialysis
3.e) EnantiostasisWhat is it?• The maintenance of metabolic + physiological functions in response to variations in the environment.
So how is that different from homeostasis?• Remember, homeostasis is about maintaining the
internal state of the organism (internal body temp., pH levels etc.), and as a result this maintains the
functional state. Enantiostasis is simply about maintaining the functional state – this means their internal state can fluctuate (i.e. they don’t need to maintain homeostasis), but in the end the organism can still maintain its normal functioning.
Here are some examples:
Grey mangrove-This is an example of an
osmoconformer – this means that it
changes to suit changes in the surrounding environment, because they’re able to tolerate internal changes in salinity to their cells.
They tolerate this change in 3 ways:
1.storing excess salt in their leaves, and then dropping them off.
2.excreting excess salt through salt glands on leaves.
3.special tissues in their roots which prevent uptake of salt but increase uptake of water.
*note: mangroves are
halophytes: plants that inhabit areas of high salinity e.g. deserts, salt marshes, and have various adaptations that allow them to live with such high salt levels in their surroundings.
-most other plants would die in such areas, because water would move out by osmosis + salt would move in → denature enzymes → death.
Bull sharks-They are an example of an
osmoregulator – this means that they
avoid changes in their internal environment by moving away from any environmental change. In this case, the sharks move away from the water when salt change occurs, to other areas with more desirable salt concentrations
-Most sharks cannot survive in freshwater because they’ll absorb too much water + lose too much salt and die. Bull sharks however, can adapt to freshwater, so less salts are removed and less water is absorbed.
Remember, if you have any questions feel free to ask!
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