Download 2.7 Biotic and Abiotic Influences on Ecosystems

2.7 Biotic and Abiotic Influences
on Ecosystems
Limiting Factors
and
Carrying Capacity
Limiting Factors
• The population size of a species can be limited by abiotic
and biotic factors
Density dependent: factors that are based on the size of
the population.
• Disease
• Predation (When one species preys (feeds) on another)
• Competition (for resources such as nesting sites, water, or
food)
Example of Predation: a lynx and hare, if the lynx eat too
many hares, the lynx population declines also.
Example of Competition: birds may compete for nesting
space
Density independent:
affect population growth
regardless of population
size
• natural disasters
• old age
• hunting
Ex) A flood will wipe out
the same percentage of
population regardless of
its size
Symbiosis
• is the close and often long-term interaction between two
different biological species.
Mutualism
• both species benefit from each other
ex) Clownfish and sea anemone
• the clownfish cleans the
anemone and the anemone
protects the clownfish
Parasitism
• one organism lives on/feeds on host.
• one organism benefits while the other is harmed
ex) Humans and mosquitoes
• mosquitoes bite humans
to get food, while humans
are harmed by blood loss,
itching, and sometimes
even disease
Commensalism
• one organism benefits while the other is unharmed.
ex) a whale and a barnacle
• the barnacle attaches to
the whale and gets a
habitat and a free ride to
a new food source while
the whale is not harmed
Population Calculation
• Population numbers can be determined by the following
equation:
(Birth rate + Immigration) – (Death Rate + Emigration)
Immigration = species moving into a region
Emigration = species moving out of a region
Influence of Biotic Factors on Population
Carrying Capacity
• The maximum population size of a particular species
that a given ecosystem can sustain.
• As population's size increases, the demand for
resources, such as food, water, shelter, and space
also increase.
• Eventually, there will not be enough resources for
each individual.
Limiting Factors
Carrying Capacity
Types of Population Growth
Human Population Trend
Earth’s
Population is
approximately
7.349 billion as
of July 1, 2015.
What’s our
limit?
8 billion
9 billion
10 billion
Are we headed
for a crash?
Class/Homework
• Pg. 55 # 1-8