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A population is the number of individual of a particular
species in an area
This area can be large or small
The world human population was about the same (or stable)
for hundreds of years
Since the beginning of the last century it has risen sharply
Reason for this rise include improved medical treatment
and better housing and nutrition
Within any habit organisms compete with each other; the
population of any species will depend on it ability to
The ability to compete will depend…read more

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Competition for resources (the amount of food, water and
shelter available to each individual)
Death rate (the number of individuals killed by predators
or disease
Successful organisms are able to increase their populations
relative to their competitors
Predator and prey relationships
Populations of predator and prey depend on one another
As prey population decreases, predator population
decreases after a delay
As prey population increases, predator population follows
after a time delay…read more

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Aphids (or greenflies) feed in garden plants, especially
Ladybirds feed on aphids
When the population of aphids goes up so does the
ladybird population after a short delay
The ladybird population depends on the aphid population
A parasite is an organism that feeds of another and a
parasite is an organism that lives in another, the host,
harming the host and very slowly killing it
If the host died to quickly the parasite would lose its food
The host gains no advantage…read more

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Mutualism (Symbiosis)
This is a relationship where both organisms benefit
e.g.…read more

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The sea anemone protects the hermit crab by
camouflaging it from its enemies
Plant mutualism
e.g. pulses (peas, beans and clovers)
These have nodules on the roots, which contain bacteria,
which are able to convert nitrogen from the air into
soluble nitrates that the plant can use for growth
In turn the plant provides the bacteria with sugar for food
Le gamious roots (e.g.…read more


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