Download Examples of limiting factors

Biotic and Abiotic Population
Influences within Ecosystems
• Limiting factors
• Tolerance
• Biotic & Abiotic population
influences
• Symbiosis
• Predator-Prey relationships
• Population equation
• Exponential growth
Limiting Factor
• Abiotic factors determine where a species can
live (temperature, precipitation, etc.)
• Biotic factors determine the species’ success
(number of predators, available food, etc.)
• A limiting factor is any factor that places an
upper limit on the size of a population.
Examples of limiting factors:
– Availability of water & food would affect how many, if
any, organisms can live in an area
– Predators to an area would affect the number of
organisms (prey) living in the area
– Temperature of the area affects which animals live there
(ex., polar bears will not be in a desert because they
would overheat)
• Factors that limit one
population in a community
may also have an indirect
effect on another population.
• Example:
lack of water limits the growth of
flowers
less flowers = less food for caterpillars
 less caterpillars
less caterpillars = less food for frogs
 less frogs
less frogs  less snakes
less snakes  less owls
Tolerance
• The ability of an
organism to
withstand a range of
biotic and abiotic
factors.
• Different species
have different ranges
of tolerance.
Tolerance
• Optimal Zone = best
conditions for the
organism to survive
• The further you go
from the optimum
zone, the lower your
population
• The range of tolerance are the conditions
that the organism can continue to exist in.
• Outside the range of tolerance, the
organism will not survive.
Abiotic Impacts on the Biomes of the World
Biotic Influences
Carrying capacity number of
organisms of one
species that an
environment
can support
indefinitely
(forever).
Do all organisms get along with
each other?
•
How organisms live together in an ecosystem
is called symbiosis.
•
There are 3 types of symbiosis:
1. Mutualism
2. Parasitism
3. Commensalism
Mutualism
• Both species benefit from the relationship.
• E.g. Clown fish and sea anemones. Clown fish
are protected from predators by the stinging
tentacles of the sea anemones and in return,
the anemone receives protection from animals
that would prey upon it.
Parasitism
• One species benefits at the expense of another species.
• Parasites usually don’t kill their host (the animal they live
on). Why would they kill the thing that is providing them
food and a home?
• Example – ticks on a dog
– A tick is a parasite that feeds off the nutrients in the
dog’s blood. The dog doesn’t get the nutrients so it is
harmed.
Commensalism
• Occurs when one species benefits from a
partnership (gets food, protection, etc.) without
benefiting or harming the other.
• E.g. Tigers and golden jackals. These jackals will
attach themselves to a particular tiger, trailing it
at a safe distance in order to feed on the big cat's
kills.
Symbiosis: Mutualism, Commensalism, and Parasitism
Predator – Prey Relationship
• Predator – a type of consumer that will seek
out and eat other organisms.
• Prey – the animal that the predator eats.
• Examples – cat & mouse; lion & antelope
Predator – Prey!!
Predator – Prey Relationship
• In many cases they act to regulate each other.
• E.g. If there are more predators, the population
of prey will decrease. If prey numbers
decrease, there is less food for the predators so
their population decreases.
Predator = Lynx, Prey = Hare
Predator = Wolf
Prey = Moose
Population Factors
• How a populations change (increase or
decrease)
•
•
•
•
Natality (Births)
Mortality (Deaths)
Immigration (Animals coming in)
Emigration (Animals leaving)
Population Factors
The Population equation
New Population =
Old Population + Natality + Immigration – Mortality – Emigration
Exponential Growth
• Rapid, uncharacteristic growth which only occurs
under certain circumstances for a short period of
time
• Can be seen when an organism enters a new
habitat that has a lot of resources or when
predators are removed
• E.g. In South Africa, elephants became
protected after many years of hunting for
their tusks. This graph shows the result of the
hunting ban instituted in 1960.