ENVIRONMENTAL
STUDIES:
Population
and
community
ecology
Ecology is the study of the interactions of organisms with their physical
and biological environments and how these determine the distribution
and make up of populations within an ecosystem. Population ecology is
concerned with fluctuations in the size of a population and the physical
and social factors that regulate these fluctuations
,Terminology
biosphere - the part of the earth where living organisms are found
ecosystem - consists of groups of different species of organisms that interact with
each other and the with the environment
organism - an individual form of life such as bacterium, protist, fungus, plant or
animal composed of a single cell or a complex of cells that are capable of growing
and reproducing
community - a group of different species that inhabit and interact in a particular
area
individual - a single organism capable of independent existence
population - a group of organisms of the same species that occupy the same area
and can breed freely with each other
What affects the size of a population ?
natality - birth rate in animals or the production of seeds in plants
mortality - death rate
immigration - individuals move into a population and stay
emigration - individuals leave a population and don't return Population
For humans the:
size is the
birth rate = the number of births per 1 000 people in a year total number
death rate = the number of deaths per 1 000 people in a year of individuals
in a
Populations will therefore: population.
grow when birth and immigration > death and emmigration
decline when death and emigration > birth and immigration
remain stable when birth and immigration = death and emmigration
In a closed population, with not immigration or emmigration, the only
parameters affecting any change in population numbers will be births or deaths,
eg. fish in a small pond
, How is the growth of a population regulated ?
If a few individuals enter an unoccupied area where there is no shortage of food or
other resources and no predators, they will reproduce and the number of individuals
will increase exponentially.
As the numbers increase, more demands are made on the available resources and
this builds up environmental resistance which causes the birth and immigration
rates to decrease and the death and emmigration rates to increase.
Eventually a balance is reached and the population stabilizes at a particular size or
number. This number is the carrying capacity of the ecosystem
environmental resistance: the total
number of factors that stop a
population from reproducing at its
maximum rate
carrying capacity: the population
density that the environment can
support
Population size = self regualting = negative-
feedback mechanism
The population fluctuates around the carrying capacity until the environment chanegs
again. Population size fluctuates seasonally and annually depending on the resources
available.
STUDIES:
Population
and
community
ecology
Ecology is the study of the interactions of organisms with their physical
and biological environments and how these determine the distribution
and make up of populations within an ecosystem. Population ecology is
concerned with fluctuations in the size of a population and the physical
and social factors that regulate these fluctuations
,Terminology
biosphere - the part of the earth where living organisms are found
ecosystem - consists of groups of different species of organisms that interact with
each other and the with the environment
organism - an individual form of life such as bacterium, protist, fungus, plant or
animal composed of a single cell or a complex of cells that are capable of growing
and reproducing
community - a group of different species that inhabit and interact in a particular
area
individual - a single organism capable of independent existence
population - a group of organisms of the same species that occupy the same area
and can breed freely with each other
What affects the size of a population ?
natality - birth rate in animals or the production of seeds in plants
mortality - death rate
immigration - individuals move into a population and stay
emigration - individuals leave a population and don't return Population
For humans the:
size is the
birth rate = the number of births per 1 000 people in a year total number
death rate = the number of deaths per 1 000 people in a year of individuals
in a
Populations will therefore: population.
grow when birth and immigration > death and emmigration
decline when death and emigration > birth and immigration
remain stable when birth and immigration = death and emmigration
In a closed population, with not immigration or emmigration, the only
parameters affecting any change in population numbers will be births or deaths,
eg. fish in a small pond
, How is the growth of a population regulated ?
If a few individuals enter an unoccupied area where there is no shortage of food or
other resources and no predators, they will reproduce and the number of individuals
will increase exponentially.
As the numbers increase, more demands are made on the available resources and
this builds up environmental resistance which causes the birth and immigration
rates to decrease and the death and emmigration rates to increase.
Eventually a balance is reached and the population stabilizes at a particular size or
number. This number is the carrying capacity of the ecosystem
environmental resistance: the total
number of factors that stop a
population from reproducing at its
maximum rate
carrying capacity: the population
density that the environment can
support
Population size = self regualting = negative-
feedback mechanism
The population fluctuates around the carrying capacity until the environment chanegs
again. Population size fluctuates seasonally and annually depending on the resources
available.
