14.3: Factors Affecting Population Change
pg. 671
Density – Dependent Factors: a factor that influences population regulation,
having a greater impact as the population density increases or decreases.
Intraspecific Competition: an ecological interaction in which individuals of
the same species or population compete for resources in their habitats.
Limitations in population growth occur when the population size increases,
causing the impact of the limitations to increase.
Matlhus’ essay expressed that organisms produce more offspring that the
environment can support; therefore individuals compete for limited
resources which leads to control of population size.
Examples of factors affecting the population size:
Competition, Predation, Diseases, and other biological effects.
Intraspecific Competition
Some species compete for the same resources. This will cause the growth
rate to decrease, and also the reproductive success is also affected. As the
competition for food increases, the amount of food per individual decreases
and this leads to a decrease in growth and reproduction.
Predation: is an ecological interaction in which predator (a member of one
species) catches, kills and consumes prey (usually a member of another
species).
Predators which prefer one prey over another and the prey has a large
population and is easier to catch can lead to density regulation of the prey.
Another density dependent factor is Disease. This will limit the population
size, in large populations, a pathogen is easily passed from one individual to
another, and then the population will decrease in size because there is an
increase in the death rate.
Allele Effect: is a density dependent phenomenon that occurs when a
population cannot survive or fails to reproduce enough to offset mortality
once the population density it to low; such populations usually do not
survive.
If the population is too small, it may become difficult to find mates or there
will be low reproduction success.
Density – Independent Factors
Density independent factors are factors that influence population regulation
regardless of population density.
Limiting Factors: are essential resources that are in short supply or
unavailable.
Human intervention or extreme weather changes are examples of density
independent factors. An increase in temperatures may impact species that
prefer certain temperatures to breed.
Insecticides applied by humans can cause Bioaccumulation and lead to a
decrease in population size along a food chain.
Resources which are in short supply are known as limiting factors can
influence the growth rate.