1. 2.7 Biotic and Abiotic Influences on Ecosystems
Limiting Factors
and
Carrying Capacity

2. Limiting Factors
The population size of a species can be limited by abiotic and biotic factors

3. 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)

4. Example of Predation: a lynx and hare, if the lynx eat too many hares, the lynx population declines also.

5. Example of Competition: birds may compete for nesting space

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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.

13. Limiting Factors
Carrying Capacity

14. Types of Population Growth

15. 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?

16. Class/Homework
Pg. 55 # 1-8