3.4.1 Populations and the Environment (AQA A2 Biology)

Word doc including all areas of population section on the syllabus. Includes human populations, predation, competition, investigating populations, variations and equations.

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3.4.1 The dynamic equilibrium of populations is affected by a number of
factors



POPULATIONS AND ECOSYSTEMS
A population is all the organisms of one species in a habitat. Populations
of different species form a community.
Within a habitat a species occupies a niche governed by adaptation to
both biotic and…

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3.4.1 The dynamic equilibrium of populations is affected by a number of
factors


INVESTIGATING POPULATIONS
A critical appreciation of some of the ways in which the numbers and
distribution of organisms may be investigated.
Random sampling with quadrats and counting along transects to obtain
quantitative data.

To study a habitat…

Page 3

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3.4.1 The dynamic equilibrium of populations is affected by a number of
factors


Transects are a more systematic way of measuring the distribution of organisms,
particularly when there is some sort of regular change in the environment, e.g tidal
shore organisms depend on high or low tides which would affect…

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3.4.1 The dynamic equilibrium of populations is affected by a number of
factors


Mark-Release-Recapture Techniques
Measuring abundance is difficult with animals because they move around and tend to
hide away from potential risks which includes the presence of humans despite them
just doing an investigation. This is why it is…

Page 5

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3.4.1 The dynamic equilibrium of populations is affected by a number of
factors


VARIATION IN POPULATION SIZE
Population size may vary as a result of:
the effect of abiotic factors
biotic factors: interspecific, intraspecific competition and
predation

Population Growth Curves
1. Slow growth as individuals reproduce to grow numbers.
2.…

Page 6

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3.4.1 The dynamic equilibrium of populations is affected by a number of
factors


Predation
There is a relationship
between predator and prey as
when prey increases, so does
predator populations. The
raise in predation will cause
prey numbers to drop which
reduces resources for
predator so their population
size also…

Page 7

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3.4.1 The dynamic equilibrium of populations is affected by a number of
factors


Demographic transition is when a population goes from a low life expectancy and
high birth rates to low birth rates and high life expectancy. This is show through age
population pyramids.




Stable population: Birth and death rates…

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