Science 20F
Carrying Capacity of an Ecosystem
When a population reaches the carrying capacity of its environment, certain factors
prevent the population from increasing any further. At this point, the population
has reached the steady state or dynamic equilibrium. While the average growth
rate of a population in the steady state is zero, fluctuations in the population size
do occur.
The carrying capacity is the maximum number of individuals of a species that can
be supported indefinitely by an ecosystem.
The carrying capacity for any species is determined by the availability of
resources, such as food and water (abiotic and biotic factors).
Populations
Population is all the members of a species living in the same ecosystem or habitat.
Some factors that could influence the population of a species are:
Biotic Potential – is the maximum number of offspring that a species could produce,
if resources were unlimited. Biotic potential is regulated by four important factors:

Birth Potential: The maximum number of offspring per birth.
Whooping crane females lay two eggs per year, and only one chick survives.

Capacity for Survival: The number of offspring that reach reproductive age.
The female sea turtle lays many eggs, but only a few of her offspring even
reach the sea, and fewer still reach maturity.

Procreation: The number of times that a species reproduces each year.
Elk mate only once per year, during the fall.

Length of Reproductive Life: The age of sexual maturity and the number of
years the individual can reproduce.
African elephants reach sexual maturity at about 15 years of age, but may
reproduce until they are 90.
Limiting Factors – The environment provides factors that prevent populations from
attaining their biotic potential. Any resource that is in short supply is a limiting
factor on a population.
Science 20F
Carrying Capacity Assignment
1) Cedar waxwings are one of the few birds that can withstand the cold and lack of
available food during our winters. To ease the strains of winter, bird watchers
in Barrie provide cedar waxwings with seeds during winter months.
a) Would the seeds alter the carrying capacity of the ecosystem?
b) Provide a hypothesis that explains why bird watchers have noted an increase
in the falcon population in recent years.
2) Classify the following information in the table below:
A) Larger mammals generally live longer than smaller ones.
B) Pregnant female elephants carry their young for nearly 18 months.
C) Elephants reach sexual maturity at 15 years.
D) Elephants usually produce one offspring each birth.
E) Most elephants wait more than 5 years between births.
F) Female elephants care for their young for more than 10 years.
G) Mice often produce litters of 6 or more.
H) After about 6 weeks, mice reach sexual maturity.
I) In a natural setting, few mice are older than 2 years.
J) A pregnant female mouse will carry her young for 22 days.
K) Mice will breed every 6 weeks or less
Biotic Potential
Offspring per birth
Capacity for survival
Procreation
Maturity
Elephant
Mouse