Saturday, 17 March 2012

Predator Prey Populations

Predators influence the death rate, birth rate and survival rate of their prey. they influence the death rate by killing adults, the birth rate by eating eggs and hatchlings and survival rate by killing the juveniles. in nature, predators rarely completely eliminate their prey. if all prey die, the predator population us under threat of starvation. most predators miss more prey than they catch. 
if the population sizes of the predator are plot don't eh same graph as the prey, it can be seen that the total number of prey is greater than the total number of predators. and the predator cycle follows the prey cycle (predator-prey cycles). as numbers of prey increase, there is more food for the predator so the numbers of predator is increase. more predators means less prey can survive and so the number of prey begin to decrease. now there is less food so the number of predators decreases, which means more prey will survive and prey number numbers increase. thus the cycle continues. 
when ecologists interpret predator-prey cycles, they must also consider other variables such as migration, climate changes and other species. 

Friday, 16 March 2012

Trophic Levels:

in an ecosystem, there must be a flow of energy occurring. the sun is the ultimate source of energy but at each level energy is stored, used and lost.
these levels are called trophic levels (from the greek triphos meaning 'food).
all feeding relationships in an ecosystem show a one-way flow of energy. the energy is not recycled.
the sun supplies the energy to the plants. the process of photosynthesis captures the energy contained in sunlight and produces carbohydrates. the plant gains the energy that it requires to power its metabolism through the production of sugars. starches are formed which make up plant tissue. when an animal eats a plant, it use the energy stored in the plant to form its own body cells. at this level most energy is lost in the conversion from plant tissue to animal tissue. only 10 percent moves up to the next trophic level. this means that at each levels most of the energy is lost.
Feeding Relationships:
autotrophs or producers are organisms that amke their won food. example green plants and algae. heterotrophs or consumers must consum other organisms in order to gain the supply of energy they need for life.
primary consumers - herbivores.
- secondary or tertiary consumers.
- carnivores.
- omnivores.
scavengers: animals that eat dead organism.
detritivores: animals that ingest organic litter and detritus.
decomposers: fungi and bacteria that causes chemical decay of organic matter and absorb the broken down material.
primary consumers are eaten by secondary consumers, and secondary consumers are eaten by tertiary consumers. all herbivores, carnivores and omnivores are predators as well.
these animals maybe small (snail) or large (kangaroo). it takes a large amount of plant material to supply the energy to keep a herbivore alive.
because of this herbivores spend most of the day eating, they are more numerous than carnivores and it takes more herbivores to keep the carnivore alive.
producers -> consumers.
plant -> caterpillar -> bird.
the plant is a producer. caterpillar is a first order consumer or primary consumer. and the bird is a second order consumer or secondary consumer.
food chains:
a simple food chain can show the interactions of organisms in an ecosystem.
a food chain illustrates what eats what.
the arrow means eaten by.
producer -> herbivore -> carnivore.
a food chain always begins with a producer.
why must a food chain always begin with a producer? because sun is the ultimate source of energy and supplies plants, in which herbivores eat, and need to eat a lot of this to remain alive. it need it for photosynthesis. plants can make their own food, anything after plants, is dependent on other animals.
each step in the food chain is called a trophic level.
food webs: food chains are useful for identifying direct relationships. however, in ecosystems, the relationships may not be so straightforward. you can get a more detailed picture of th einteractions in an ecosystem if the food chains are combined to form a food web. a food web is a series of food chains combined together.

Food pyramids:
pyramids of numbers.
show the number of organisms at each trophic level. the pyramid has a base much greater than its top. this shows the normal ecosystem with more producers than herbivores and more herbivores than carnivores. why are there usually more producers than consumers in an ecosystem? it is because there is a loss of energy at every trophic level. at each level only one tenth of the matter consumed is used to make body cells. the rest is used to keep warm, to move, and to power all the living processes (metabolism) in the animals. some of the materials passes through undigested.
this means that you need more plants to support a number of herbivores and more herbivores than carnivores (because energy is lost at every trophic level).
Food Pyramid:
top carnivore
pyramid of biomass.
is the amount of organic/living matter in an organism. there are more plants than animals. the animals that eat plants (herbivores) are more abundant than the next level of consumers. the top consumers are usually the least abundant of any group in the ecosystem. in some circumstances, it is better to weigh the organisms instead of counting them. a gum tree obviously has more effect on the ecosystem than a tussock of grass.
in this case organisms are weighed to calculate the biomass (the biologically mass) to measure biomass the organism is usually dehydrated. this means that water is drained before weighing.
biomass in grass:
2g: teritary consumers.
10g: secondary consumers.
40g: consumers.
820g: producers.
Pyramid of biomass: from the diagram, it can be seen that it takes 820 g of a producer to support 40 g of first order consumer, 10 grams of secondary consumer which in turn supports 2g of teritary consumer. why does this happen?
if you think of a herbivore eating a plant it does not convert all of the matter contained in the plant into the herbivore. some of the material is indigestable and passes out of the animal as faeces. a lot of the material is consumed during respiration. this fuels the activities of the herbivore. only a small amount of biomass on one level becomes biomass on the next. much is lost through heat released during respiration. at each level there is a loss of up to 90 percent of biomass.
Pyramids of energy:
energy pyramids represent the flow of energy through the ecosystem. at each trophic level there is only 10 percent efficiency. that means that 90 percent of the energy is lost at each level. a plant uses 10 percent of the light energy available. when a herbivore consumes a plant there is only 10 percent of the energy stored in the plant tissue as sugar that is converted into energy in the herbivore and so on up the food chain. if humans were the top consumers and only ate plants, there would be energy loss in the food chain.
pyramid of energy (ks/m swuare year).

populations will continue to expand until the numbers are limited by one of the resources they require. examples of resources that organisms need are:
nesting sites
soil and weather.
where there is more than one species contending for the same limited resource, we say that the organisms are 'competing'.
usually one species has an advantage over the other and may limit the growth of that population.
on rock platforms in NSW there are 2 species of mollusc that feed on algae. one is the limpet cellena sp and the other melanerita sp melanertia moves faster than cellena if the algae are in short supply than melanerita has an advantage over the competitor. it can remove the algae form the rock before cellana.
Competitive exclusive principal:
proposes that 2 different species cannot coexist in the same place. if they are competing for the same limited resource.


Wednesday, 7 March 2012

Planning First-hand Investigations

Principles of experimentation:
the scientific knowledge we have today has been developed largely by subjecting hypotheses to strict and comprehensive testing. a hypothesis is a possible explanation for an observation, an educated guess to account for what is observed. when a hypothesis is tested under controlled conditions, the experimental results either support or disprove the hypothesis. when a hypothesis is supported by experimental data it does necessarily mean that it will always hold true. later evidence may disprove the hypothesis or provide new information that means the original hypothesis needs to be modified and retested. 
a controlled experiment involves setting up two trials, the same in every respect except one: the factor being examined. this factor is often called the experimental variable or simply the variable. in one trial, all factors are kept constant while measurements are taken. this set-up is called the control. in the other trial, one factor is varied. this will ensure that any results obtained are the results of the variable being tested, and not caused by some other random factor. that is, controlled experiments test one factor at a time. 
the reliability of testing does not just lie in the setting up of a single controlled experiment. experiments must be able to be conducted repeatedly with the same results. when the same results are obtained repeatedly by following the same procedures, the hypothesis being tested is supported further. repetition, especially by other scientists, is an important part of ensuring reliability in scientific testing. this because when the same results are obtained the objectively of the experiment is reinforced. 
scientists must be very careful to ensure that personal bias does not enter into their experimental method. valid conclusions can only be made when experimental procedures are controlled and objective (controlled links back to controlled experiments and objective means not influenced by personal feelings or opinions.)

real biological investigations often evolve as a result of a great deal of trial and error. they rarely start with logically developed 'step by step' procedures and clearly formulated recipes. 
the description that follows outlines a possible sequence of events in designing an experimental investigation:
scientific inquiry:
with only slight modifications, the approach to scientific inquiry described below will help you to design scientifically sound (means extra research for me) experiments.
making an observation:
scientific inquiry starts when you make an observation about something. 
asking a question:
ask a question or questions about the observation.
formulating a hypothesis:
a hypothesis is a simple statement that attempts to answer a question--it is not itself a question. a good hypothesis is really an educated guess, and it should be testable by experimentation.
designing an experiment:
when you have considered a suitable approach you should write out a step-by-step account of how you will proceed. in this instance you will also need to design a choice chamber in which to test your hypothesis. this should be relatively simple to do. 
controlling variables: 
in this experiment, slaters are given a choice between wet and dry conditions. in order to be certain that the slaters are really making a choice only between these two options, all other conditions must be identical (for example, just one plant pot and if show these two options might be cause by random factor get two and then is more reliable).

humidity is the experimental (or independent) variable, the one you are manipulating, and the behaviour of the slaters is the responding (or dependent) variable. this is the one that changes in response to the variable that is manipulated. all the other conditions that do not change but could are called fixed (or constant) variables.
it is essential that only one variable at at time is manipulated.

follow each step of the procedure you have designed.
recording data:
ensure that you record all the relevant data as you go. this includes any measurements and / or observations you make
summarising results:
this involves analysing the data you have collected and writing a summary statement. attempt to explain any unexpected results. 
evaluating experimental procedure:
outline the strengths and weaknesses of your experimental design, then describe the ways in which your procedure could be improved.
making a concluding statement:
make a concluding statement about your results in relation to the hypothesis you set out to test. did your results support the hypothesis?

accurate record-keeping is a vital part of the scientific process. it enables other scientists to read, analyse and repeat the experimental procedures that have been undertaken by their peers. it is particularly important when the results of experiments can have an impact on the well being of the community, such as in the development of medicinal drugs. no one in the community would be satisfied about the safety of a drug if the research scientist have committed the test results to memory instead of to paper or the microchip.

title: an appropriate name for the exercise conveys information about the topic being discussed.
purpose (aim in relation to designing experiments): a brief statement outlining what is being investigated, what you are setting out to discover, should be provided. some experiments require you to investigate more than one aspect of the topic. in this book each item under investigation is outlined in a separate statement under the purpose (equipment in relation to designing experiments).
materials: all items of laboratory equipment, chemicals, specimens and miscellaneous materials that are used in the completion of the activity should be listed.
procedure: the steps followed in completing practical activities must be carefully catalogued. a step by step approach is a useful way of producing a description of your method. a summary of your procedure is especially important to have as a reference when their is doubt about experimental error. it is also a clear recipe for others to follow if required. 
results and discussion: a summary of your experimental findings, together with your conclusion, forms the basis of your practical work. the discussion should contain a clear description of the results of your experimentation. this may be done in a range of forms, for example, in a written synopsis or in a table or in graphic form. analysis and interpretation (like for example a table--what should this finding be placed under etc) is an important feature of this section of your report.
answers to set questions also form part of the discussion. often the set questions help you to describe and interpret experimental results. drawings and diagrams are also included in the discussion section of your report.
other comments that you wish to make, including factors that have limited your work, are relevant here. so too are suggested explanations for unusual or unexpected results(these do not necessarily indicate error or flawed procedure).
conclusion: this is a statement outlining the results of your investigation. it should state what you discovered in relation to your purpose (so has to relate somewhat to your hypothesis--an educated guess, an answer to an observation). the conclusion is often covered by the discussion questions so it is not necessarily written as a seperate section.


Tuesday, 6 March 2012

Beneficial Interactions

Classification of interactions:
There are a large number of ways that organisms can interact.
classification of these interaction makes studying them easier.
two types of interactions.
1. detrimental -- when one or more organisms are harmed or disadvantaged from the relationship.
2. beneficial (symbionic): when one or more organism benefit from the relationship.

Predator Prey Relationship:
is a detrimental feeding relationship where the predator (consumer) obtain its food by killing an organism for example spiders eating flies or eagles eating bush rates.
predators affect the abundance of their prey.
as prey are consumed, their numbers decline, leading to a shortage of food for the predators whose numbers also decline.

Factors affecting predator-prey populations:
number of predators competing for same prey.
avaliability of preys food.
birth rate.
death rate.
number of males and females.
size of ecosystem for supporting the predator and prey numbers.

allellopathy is a plant relationship.
a plant produces chemicals that can be beneficial or detrimental to another plant.
many australian plants produce allelochemicals. these substances are released by the plants and concerntrate in the soil.
they inhibit the growth of other plants in the area and give the plant a competitive advantage.
soem pine trees are allelopathic. when their needles fall to the ground, they begin to decompose and release acid into the soil. this acid in the soil keeps unwanted plants from growing near the pine tree.
fern frons produce chemicals that prevent pine seeds from germinating. allelopathy can be used in agriculture as natural form of weed control.

symbiosis is the term used for interactions in which two organisms live together in a close relationship that is beneficial to at least one of them.
there are there types of beneficial or symbiotic interactions.
parasitism- one species benefit and the other is harmed.
mutualism- both species in the relationship benefit from the association.
commensalism: one species benefit and the other is unaffected.

parasitism is the close relation between two organisms where one is benefited and the other is disadvantaged.
the organism benefiting lives on or within the body of the disadvantaged organism (called the host). although the host is harmed, it is not usually killed by the parasite. the parasite is often smaller than their host and they may live on the surface of their host (endoparasites e.g: ticks, fleas and tinea) or internally (endoparasites e.g tapeworms).
other examples include disease-causing organisms like bacteria and viruses.
plant parasites are strangler fig and mistletoe.

mutualism is the relationship between two organisms where both organisms benefit from the relationship. neither can live without the other. a common example of mutualism is lichen.
lichen is a close relationship between a fungus and algae.
lichen is a close relationship between a fungus and algae. the fungus gains nourishment from the photoshynthetic algae. the algae are provided with a substrate to live within. lichen is found growing on rocks, trees and buildings.
-reef-builing corals have symbiotic algae within their tissues which provide the yellow-brown pigment that give the coral its colour.
-the algae live, reproduce and photosynthesise int he host and use the waste products of the heat.
-in turn, the coral uses oxygen and food produced by the algae during photosynthesis to grow, reproduce, and form its hard skeleton, which is the basis of the reef.
the formation of the great barrier reed depends n this mutualistic relationship.

commenalism is a loose relationship where neither organism is disadvantaged but one maybe advantaged. an example of commenalism is a remora attached to a shark. a remora is a small fish with suckers (modified dorsal fins) on its head.
it attaches to the shark and is carried around by the shark. the remora can feed on any scraps of food that the shark misses.
the shark does not seem to be affected by this
the bird nesting in a tree is another example of commensalism.
the bird gains a place to raise it's young and the tree is not affected.
lichen growing on a tree trunk show a common from of commensalism. the lichen gets a place to attach off the ground and the tree is not affected by the lichen.


Thursday, 1 March 2012

Classification of Interactions And More Information on Capture Recapture Method

Quadrant method cant be used, as animals move around the capture recapture method is used instead. by tagging and marking animals it is possible to work out an estimate of the population.
the total number in a population can be estimated using the following formula:
Population size: number of animals tagged x number of animals recaptured / average number of tagged animals recaptured. 
or for an abbreviation: MXN / N
the mark release recapture technique is based on a number of assumptions for accurate estimates of the total population to be calculated.
1. there is no population change through migration, births or deaths between the sampling periods.
2. all animals are equally able to be caught.
3. mark animals are not hampered in their ability to move and mix freely with the rest of the population.
there are problems with this method. if you are not careful with your tagging method you could cause the death of the animals that you tag. the tag may make the animal more likely to be caught by a predator. this could affect your result. when using traps to catch small mammals such as marsupial mice some of the animals become trap-shy and will not return to be captured. others enjoy the experience and return often to take the bait offered. other examples of tagging methods are leg bands on birds, paint spots on shell fish, colouring fur and ear tags. 
trends in population estimates can be seen easily when abundance values have been graphed. examining trends can lead to inferences about the species and what abiotic or biotic characteristics they are most suited to.


Sunday, 19 February 2012

Sampling Techniques

Sampling techniques are used to estimate population numbers when total counts cannot be made.

Capture Mark Recapture:
Is one of the several ways biologists estimate population size. It is a method which involves catching a certain number of individuals of a particular species, marking or tagging them in a way that does not affect their life expectancy then releasing them into the wild and after catching another group and counting the number of tagged amongst the recaptured. A formula can then be used to estimate the total size of the population. This method is suited for mobile populations where it is impossible to count all individuals at one time i.e: birds, fish, butterflies.
A quadrant is a defined area which measures the distribution or number in a population. The size of the quadrant is usually determined by the size of the organism being counted.
The quadrants can be placed randomly in the area and numbers of organisms in each quadrant is recorded.
Random quadrants are useful to estimate population size of stationary organisms, or organisms that do not rapidly move to other areas over long distances.
The more quadrants and the more you sample the more accurate the abundance. A tally of the numbers in each quadrant can be used to estimate the total number in one area, or the average number per quadrants. It can be used for the density.
A transect is a line, strip or profile for counting and mapping the number of individuals at different distances along the line. Quadrants are often placed specified distances along the transect and individuals counted in these quadrants. Transects are often used to show how the diversity of species changes across an area. Transects often include scale to show only the height of the plants but any change in topography such as valleys or mountains.
Percentage cover is a sampling technique which uses a 100 percent point guide to estimate abundance. It is used when it is extremely hard to count each individual or it is not clear how many individuals are present. The estimate is given as a percentage.

A data logger is a useful instrument that you can take on a field study. It will gather data that can be taken back to a computer and analysed.
Sampling techniques measuring abiotic factors:
Sampling is carried out when it is not possible to count every individual in a population. A small is area is counted in detail and then multiplied to get a estimate for the whole area.
Measuring Distribution: Transect Lines
A transect is a straight line usually a string is laid across and area and the organism along the line are recorded a transect is used to sample plant populations. Can be used for animals especially if they attached to one sport, for example larnicle on a rock platform.
The organism that lie on the transect line or string are recorded.
Continuous sampling along a transect records every organisms that touches the string. The transect can be designated width either side (for example, a 1 meter string of the line transect). Transects are particularly for studying the changing distribution as the abiotic factors change so does the vegetation. A transect is a good way of monitoring the change.
Measuring Abundance:
The quadrant method is used for population that does not move.
It can be made using 4 wooden stakes and string.
Quadrant (squares of a fixed area) are replaced randomly in an area.
The abundance of the organism in that area is counted.
This is then repeated several times and an average is taken
Then the size of the whole area is measured and multiplied by the average from the quadrant results. The quadrants are placed at random.
You can count the actual numbers of each plant or work out a percentage cover for each species. It is necessary to take enough samples to have a reasonable estimate of the population.
Sample size:
When studying an area you have to make a decision on the size of your quadrant.
The number of quadrants that you taken
Count the organisms that are completely within the quadrant
Count an organism if any part of it lies within the quadrant.


you will need a four meter length of string and four wooden pegs or a quadrant.
if you have a garden avaliable, use the lawn for the following practical.
1. select a random spot in lawn. you can do this by throwing a stick over your shoulder and starting one of your corners of the quadrant where the stick lands.
2. select a plant that you can recognise, such as dandelion, bindi eye, clover it does not matter if you don't know the name just as long as you can recognise it.
3. make your quadrant using the four pegs + the string. a good size is a meter X a meter but a smaller quadrant is acceptable. whatever size you use, make sure you can work out the size of your quadrant.
4. count the number of your chosen plants in the square.
5. repeat so that you have 10 measurements.
6. work out the average number of your plant in your samples.
you can now work out the total number of plants in the lawn by multiplying the density by the total area. measure or estimate the size of you are (multiply by the length of the breadth).
length of area:
width of area:
area in square meters:
multiply the area by the average number of plants in a quadrant.
this will give you an estimate of your chosen plant.
chosen plant per square meter.
Percentage cover:
in some cases when you are investigating an ecosystem it is more useful to record the percentage cover value than the actual number or organisms. a very small but dense plant is very difficult to count.
again you can use a quadrant to estimate the abundance of this type of plant of animal. this time the quadrant is divided into a grid using string.
to work out the percentage cover you have to count the number of squares that are covered by the plant. if the plants dosen't cover an entire square, you have to estimate the percentage of squares covered.
work out the percentage cover of the small plant from the following plan diagram.
rough estimate:
total number of squares: 10 X 10 = 100
number of squares covered: 3 + 2+ 2.4 + 4 11.5
percentage cover: number of squares covered / total number of squares x 100
11/5 /100 X 100 = 11.5%

Transects--plan sketches and profile sketches:
Rope or measure tape marks the line that is drawn to scale.
The area is selected at random across the ecosystem.
Species are plotted along the line, in surface view for a plan sketch or in side on view for a profile sketch.
Advantages: proves a quick, easy and inexpensive method for measuring species occurance.
Minimal disturbance to the environment.
Disadvantages: only suitable for plants or slow-moving animals. species occuring in low numbers may be missed.
Quadrant sampling:
Measuring tape, metre rulers or quadrants are used to randomly place the 1m X 1 m square areas.
The occurance of organisms in the quadrant is recorded and repeated a number of times.
Individual species can be counted if in small numbers or percentage cover can be calculated for larger numbers by estimating the percentage cover fro each quadrant and then finding an average of the of the quadrants taken.
Advantages: quadrants can also be used for determining the distribution of species along a transect. easy and inexpensive method for measuring abundance in large populations. minimal disturbance to the environment.
Disadvantages: only suited for plants and slow moving animals.
Animals are captured, tagged or marked and then released.
After a suitable time to mix with others, a sample is recaptured.
The number of tagged or marked animals recaptured is counted.
Numbers are then entered into the formula.
Abundance = number captured x number recaptured / number marked in recapture
Advantages: a simple method that provides an estimate of abundance for animals in large populations that are difficult to count.
Disadvantages: only suitable for mobile animals.
Can be time consuming depending on the type of species captured, method of tagging, and time Suitable for waiting while tagged group mix with others.
Can be disturbing to the environment.


Monday, 13 February 2012

Energy: Respiration & Photosynthesis

All living things need energy to remain alive.

Photosynthesis is the chemical process used by chlorophyll containing cells to convert inorganic raw materials into organic compounds, using light energy. All plants have chloroplasts which contain chlorophyll and carry out photosynthesis. Cyanobacteria also carries out photosynthesis.
Lighter energy from the sun is used to drive the photosynthesis reaction. The light energy is converted into chemical energy which is stored in complex organic molecules such as carbohydrates. When an animal eats a plant it obtains this chemical energy. Thus energy is passed along the food chain.
Photosynthesis has a dual role in ecosystems; it begins food chains by capturing light energy and converting it into chemical energy and it also releases oxygen as a by product. The oxygen can then be used by all organisms in respiration. 
All living organisms depend upon photosynthesis or organisms that photosynthesise for survival.

THE PHRASES (there are two stages for photosynthesis):

Light reaction: 
Light energy is trapped by chlorophyll and is used to split up water molecules into hydrogen and oxygen.

Dark reaction: 
Carbon dioxide form the air combines with the hydrogen to form carbohydrates.



There are two types of respiration
Aerobic: requires oxygen and forms carbon dioxide, water and energy.
Anaerobic: occurs without oxygen and its product depends on the situation.

Respiration is the breakdown of glucose with oxygen to release energy. The energy is held in the glucose bonds, when they are broken down energy is released.

Respiration is a series of chemical reactions which releases energy from complex carbohydrates. All living things respire. Aerobic respiration is the complete breakdown of molecules such as sugars, using oxygen to form carbon dioxide and water. Anaerobic respiration occurs when there is no oxygen avaliable, or the cell has insufficient oxygen. The products of anaerobic respiration depend upon the situation. 

Stages of respiration (aerobic respiration):
The general equation for aerobic respiration shows the reactants and the final products however, the process does not occur in one step. It occurs in a series of controlled chemical reactions with about 50 different stages, each catalysed by a different enzyme. An enzyme is a chemical made by living things and its function is to control the rate of a specific chemical reaction that occurs in the body.

glucose + oxygen -> carbon dioxide + water

Respiration can be divided into two main stages:
The first stage breaks down glucose, a 6 carbon sugar, into two 3-carbon molecules called pyruvate. A small amount of energy is released at this stage. 
The second stage is the breakdown of this 3 carbon molecule, pyruvate, into a 1 carbon molecule instead, carbon dioxide. This stage uses oxygen and releases a much larger amount of energy.

There are two stages in respiration (in which this information relates to the above stages):

—occurs in the cytoplasm
—2 ATP molecules are gained
—splits the 6 carbon glucose into two 3 carbon molecules (pyruvate).
—does not require oxygen.


-- occurs in the mitochondria
-- pyruvate is broken down into water and CO2 (one carbon) 
-- 36 ATP molecules are gained
-- oxygen is required

ATP -- adenosine triphosphate (one adenosine attached to three phosphate groups). This is the energy carrier of all cells.
For every glucose molecule 38 ATP molecules are produced.



According to the first law of thermodynamics, energy can neither be destroyed nor created; rather, it is converted from one from into another.

Energy can take many forms:
--potential energy
In cells the energy released in respiration comes from the carbon bonds in food molecules. If a cell is not given sufficient external food it will use any organic compound as the fuel source for respiration i.e: any carbohydrate, fat, protein etc.
The energy released by respiration can be used by the organism in several different ways. Some of the energy is released as heat and this is used to maintain body temperature. This is important for endotherms (warm-blooded animals). If a human gets cold, muscles will start to shiver, this is their way of increasing activity, respiring at a higher rate and releasing heat for the body. Heat is needed by the body for reactions as the enzymes in the body require an optimum temperature for maximum efficiency. At low temperatures the random movement of molecules decreases, reducing their chance of bumping into each other and hence having a reaction.

Use of energy by organisms:
--maintaining body temperature
--active transport
--cell maintenance
--synthesis of fats.

The released energy can also be used to cause other chemical reactions in cells to occur and for repair of damaged or old cells, or for active transport of materials across cell membranes.