Population growth curves / predation

What 4 factors affect the size of a population

• births

• Deaths

• Emigration

• Immigration

What is emigration

Individuals leaving a population

What is immigration

Individuals joining a population

what does a logistic growth graph look like

what are the 4 phases of a population growth curve

• lag phase

• log phase

• stationary phase

• death phase

what happens in the lag phase of population growth

a species colonises an area, and there is no increase in population size

what happens in the log phase of population growth

• there is no limiting factors and more resources available, so there is exponential growth

• max growth rate occurs here

what happens in the stationary phase of population growth

• the carrying capacity is reached, so no more individuals can be held by the resources

• a plateau is reached

• rate of cell division=rate of cell death

what happens in the death phase of population growth

• a sudden change in environment (eg drought or food storage) causes an exponential decrease in population

when are logarithmic scales useful

• when investigating bacteria

• when managing experimental data relating to large scales

what is interspecific competition

competition between different species

what is intraspecific competition between species

competition within same species

what is the competitive exclusion principle

• if conditions remain the same, this will lead to the complete removal of one species

• the species that uses the resources most effectively will ultimately eliminate the other

• the 2 species can’t occupy the same niche indefinitely

what does an increased food supply lead to

increased birth rate or bigger individuals

explain the cyclical nature of a predator/prey relationship

• predators eat prey so prey numbers reduced

• fewer prey= greater predator competition

• predator population reduces

• prey population increases

• more prey available so predator population increases, repeats