18.3 Types of Interactions
Limiting Factors & Carrying Capacity
 Limiting Factor – something that limits the
size of a population
 Ex: Food, Water, Space
 Carrying Capacity – the largest population
that an environment can support.
 Limiting factors influence the carrying
capacity.
Competition
Competition occurs when two organisms
try to use the same resources.
Can be within a population or a community
Predation
 Prey – organism that is
killed & eaten by another
 Predator – organism that
kills another for food.
 Predators have adaptations
that help them capture
their prey (i.e. speed,
sharp teeth, claws).
 Prey also have adaptations
to protect themselves (i.e.
camouflage, poison).
Symbiosis
 Symbiosis is the long term association or
relationship between organisms that
benefits at least 1 organism.
 3 Types: Mutualism, Commensalism,
Parasitism
Mutualism
 Symbiotic relationship in which both
organisms benefit.

Example:
 Egyptian Plover &
the crocodile
Commensalism
 Symbiotic relationship in which one organism
benefits and the other is unaffected.

 Example:
 Whale Shark &
Golden Trevallys
Parasitism
 Symbiotic relationship in which one
organism benefits and the other is
harmed.

 Example:
 Ant & Parasitic Fungus
Video Time
Comprehension Check
 How do limiting factors affect the carrying capacity?
 How are the three types of symbiosis different?
 How are predation and parasitism different?