POPULATION STUDIES
Ecology the study of the interactions of organisms with their physical and
biological environments
Population ecology concerned with the irregular rising and falling size of a
population, and both the physical and social aspects that regulate these fluctuations
FACTORS AFFECTING SIZE OF A POPULATION
Natality – birth rate in animals or the production of
seeds in a plant
Mortality – death rate
Immigration – individuals moving (In)to a population and
stay
Emigration – individuals leave (Exit) a population and do
not return
Humans birth rate, number of births per 1000 people
peryear
death rate, number of deaths per 1000
people peryear
Populations grow when birth and immigration exceed
death and emigration
Populations decline when death and emigration exceed
birth and immigration
Remain stable when birth and immigration
approximately equal death and emigration
In a closed population i.e. a fishpond, there is no
immigration or emigration, the only factors affecting
change in population numbers will be births and deaths
REGULATION OF POPULATIONS
If a few individuals enter an unoccupied area, where there is no shortage of
food or any other resources and no predators - they will reproduce and grow
exponentially in population.
As the numbers increase – there is more pressure on the available resources
builds up environmental resistance, which causes birth rate and
immigration to decrease and the death and emigration to increase.
ENVIRONMENTAL RESISTANCE – the total number of factors that stop a
population from reproducing at its maximum rate
A balance is reached population stabilizes at a particular point, this is the
carrying capacity
CARRYING CAPACITY the population density that the environment can
support
Ecology the study of the interactions of organisms with their physical and
biological environments
Population ecology concerned with the irregular rising and falling size of a
population, and both the physical and social aspects that regulate these fluctuations
FACTORS AFFECTING SIZE OF A POPULATION
Natality – birth rate in animals or the production of
seeds in a plant
Mortality – death rate
Immigration – individuals moving (In)to a population and
stay
Emigration – individuals leave (Exit) a population and do
not return
Humans birth rate, number of births per 1000 people
peryear
death rate, number of deaths per 1000
people peryear
Populations grow when birth and immigration exceed
death and emigration
Populations decline when death and emigration exceed
birth and immigration
Remain stable when birth and immigration
approximately equal death and emigration
In a closed population i.e. a fishpond, there is no
immigration or emigration, the only factors affecting
change in population numbers will be births and deaths
REGULATION OF POPULATIONS
If a few individuals enter an unoccupied area, where there is no shortage of
food or any other resources and no predators - they will reproduce and grow
exponentially in population.
As the numbers increase – there is more pressure on the available resources
builds up environmental resistance, which causes birth rate and
immigration to decrease and the death and emigration to increase.
ENVIRONMENTAL RESISTANCE – the total number of factors that stop a
population from reproducing at its maximum rate
A balance is reached population stabilizes at a particular point, this is the
carrying capacity
CARRYING CAPACITY the population density that the environment can
support
