IEB Grade 12 Population ecology notes and summary

↳ and
the
study of the interactions of organisms with their
physical biological environment

and how these determine the distribution and make up of populations within an
ecosystem
↳
concerned with fluctuations in size of a population and the factors (physical and social )

that these fluctuations
regulate


Definitions
individual
single organism capable of independent existence
•
-




species group of organisms with similar characteristics that are capable of breeding with
•
-




one another and
producing fertile offspring
groups of different species of organisms that interact with each other and the
ecosystem
•
-




environment

group of different species that inhabit and interact in a particular area
-




community
•




population individuals of the same species that
group of the same area and can
° -




occupy
breed with one another
freely

Populationparameters
↳
factors that affect the size of the population (total number of individual in a population)
birth / natality increases population size
•
-




death / decreases population
mortality size
°
-




•



immigration
-

increases population size as individuals move into an area

decreases population individuals of
emigration size as move out an area
-
•




↳
population remain stable when birth and immigration approximately equal death and

emigration
↳ in a closed population ,
with no
immigration /emigration ,
the only parameters affecting any
change in population numbers will be births 1deaths leg .
fish in a small pond )

,Howisgrowthofapopulationregulated.tl
Environmental resistance : factors that stop a

←
population from reproducing at a maximum rate




←
carrying capacity : the population
density that the
environment can support



←
Exponential growth : increasing more
rapidly


Stablepopulation
↳
if individuals enter unoccupied area where there is no of food / resources and
an shortage 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 cause the birth /immigration rate to decrease and the death /


emigration rate to increase

↳
eventually a balance is reached and the population stabilizes at particular number / size (carrying

capacity )
↳
population fluctuates around carrying capacity until the environment changes
↳
and available resources
population size fluctuates seasonally annually depending on the


feedback )
↳
population size is
self-regulating leg negative
.




Unstablepopulation
Carrying capacity of an environment can
change :
if a population exceeds carrying capacity seen in the
•



.




graph on the left

•


if a drought occurs ,
this can reduce
carrying capacity
This results in the habitat :




deteriorating rapidly which reduces
•




,
carrying capacity
eventually not being able to support the population
'




,




which will decrease
rapidly and become exinct
.