, Sigmoid population growth curve
Carrying capacity- max population
size an environment can support.
No constraints
act to limit the Further population growth is
population prevented by external constraints.
Slow growth- explosion. During this time the population size
fluctuates, due to fluctuations in
Population size
shortage of
reproducing limiting factors e.g. predators, but
individuals but birth overall its size remains relatively
rate is still higher stable. Birth rates & death rates
than death rate so are approximately equal.
Rapid
population increases. growth. As
number of
breeding
individuals
Limiting factors are environmental
increases, the
total population resources or constraints that limit
multiplies population growth. (can be abiotic
exponentially or biotic factors)
Time
Migration & density independent factors (e.g. earthquakes) can also effect population size.
, Competition
Competition is a biotic limiting factor that is the result of interactions between living
organisms
• Interspecific competition- Competition between different species. This occurs when
2 or more different species of organisms compete for the same resource. This
interaction results in a reduction of the resource available to both populations. So if
both species are equally adapted to compete for the resource, there will be smaller
populations than if only one of the species had been present. However, if 2 species of
organism are competing for the same resource & one is better adapted, the less well
adapted species is likely to be outcompeted. This is known as the competitive
exclusion principle- where 2 species are competing for limited resources, the one
that uses the resources more effectively will ultimately eliminate the other, e.g. red
& grey squirrels in the UK.
• Intraspecific competition-
Competition between members
of the same species. The
availability of the resource
determines population size – the
greater the availability the
larger the population that can
be supported. This results in
fluctuations in the number of
organisms present in a
particular population over time.
Carrying capacity- max population
size an environment can support.
No constraints
act to limit the Further population growth is
population prevented by external constraints.
Slow growth- explosion. During this time the population size
fluctuates, due to fluctuations in
Population size
shortage of
reproducing limiting factors e.g. predators, but
individuals but birth overall its size remains relatively
rate is still higher stable. Birth rates & death rates
than death rate so are approximately equal.
Rapid
population increases. growth. As
number of
breeding
individuals
Limiting factors are environmental
increases, the
total population resources or constraints that limit
multiplies population growth. (can be abiotic
exponentially or biotic factors)
Time
Migration & density independent factors (e.g. earthquakes) can also effect population size.
, Competition
Competition is a biotic limiting factor that is the result of interactions between living
organisms
• Interspecific competition- Competition between different species. This occurs when
2 or more different species of organisms compete for the same resource. This
interaction results in a reduction of the resource available to both populations. So if
both species are equally adapted to compete for the resource, there will be smaller
populations than if only one of the species had been present. However, if 2 species of
organism are competing for the same resource & one is better adapted, the less well
adapted species is likely to be outcompeted. This is known as the competitive
exclusion principle- where 2 species are competing for limited resources, the one
that uses the resources more effectively will ultimately eliminate the other, e.g. red
& grey squirrels in the UK.
• Intraspecific competition-
Competition between members
of the same species. The
availability of the resource
determines population size – the
greater the availability the
larger the population that can
be supported. This results in
fluctuations in the number of
organisms present in a
particular population over time.
