Variation in Population Size

Abiotic Factors

Biotic Factors

What is Interspecific competition?

What is Intraspecific competition and Predation?

Different things may determine the population sizes within an ecosystem.

Abiotic Factors

Non-living factors such as light intensitytemperature and humidity determine the number of organisms that a habitat can sustain. All species have a varying degree of ability to withstand harsh or fluctuating conditions, called resilience. If an abiotic factor changes dramatically in favour of a population – for example, plenty more light in a field – then the population will increase provided no other factors are limiting. The opposite is true if an abiotic factor changes against the resilience limit of a population – it will decrease.

Biotic Factors

“Living factors” refer to all interactions between organisms, be it a bunny rabbit being predated, or two shrubs competing for sunlight. All individual actions between organisms form a web which impacts on all populations in an ecosystem, therefore determining their sizes.

Interspecific competition

Interspecific competition refers to competition between members of different species for the same resources (food, lightwater, etc.). Often when a new species is introduced in a habitat, say the American ladybird to the UK, if the invader species is better adapted, then the host population decreases in size. This may lead to extinction in some cases of the host species.

Can’t remember the difference between interspecific and intraspecific? Interspecific is like the internet – different things come together.

Intraspecific competition

Intraspecific competition refers to competition…..

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