Biology unit 4

All the topic of unit 4 aqa biology.

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Populations 1.1

1.1 Key words

Ecosystem- The abiotic and biotic features in a specific area.

Biotic-  a factor that makes up part of the living environment for an organism e.g food source.

Abiotic- a factor that makes up part of the non- biological envioronment of an organism e.g temperture.

Population- A group of interbredding organisms of one speices in a habitat.

Community- All the populations of different organisms living and interacting ina particular place at the same time.

Habitat- where a community of organisms lives.

Niche- how an organism fits into the enviroment. Where an organism lives and what it does there.  

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Populations 1.2

1.2.1 Investigation- methods

Quarats- considering size, number to sample, position of the quadrats.

Random sampling- used to avoid bias. Random number generation by co ordinates.

Systematic sampling aklong transects- A belt transect to measure the spread of the sample over the length of the area being investigated.

Mark, relaease, recapture- Animals are caught and marked. The number is recorded. The organisms are released and after a given period of time the animals in the same area are caught again. The amount of marked animals to none marked is measure and the popualtion size can be estimated by the following equation. 

Estimated population size = (total number of individuals inb the first sample X total number of individuals in the scond sample) / number of marked individuals recaptured.

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Populations 1.2

1.2.2 Investigation- ethics


-Organisms should be studied in 'situ' where possible to avoid disruption.

-Organisms removed from a site should be returned to the original habitat.

-A sufficient period of time should elapse before the same site is used again.

-Disturbance should be avoided.

-Marking techniques must not be damaging.  


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Populations 1.3

1.3 Variation in size

Biotic factors: Are lack of food source due to abiotic factors etc.

Abiotic factors:

- Temperture - Each species has a different optimum temperture slight changes to the overall temperature could lower the organisms metabolic rate and slow the population growth.

- Light- The energy for ecosystems comes from light. It effects the rate of photosynthesis.

-pH- Effects the actions of enzymes. All enzymes has a different optimum pH.

-Water- when water is scarce popualtions are small so only adapted organsims can live.

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Populations 1.4

1.4 Competition

Intraspecific- Organisms

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