NICHES AND COMMUNITY INTERACTIONSWhat is a niche?How does competition shape communities?How do predation and herbivory shape communities?What are the three primary ways that organisms depend on each other?

Tolerance• Species have a range of conditions under which they can

live and grow• “Tolerance” is the ability to survive and reproduce

• Example: Temperature

Habitat• There are upper and lower

limits of tolerance for every environmental factor• What is an environmental factor?

• Tolerance determines “Habitat”, or general place where something lives

The Niche• Niche is like the organisms environmental job, how does it

fit into the community?• Two aspects of it’s niche

• Physical (abiotic)• Biological (biotic)

• What is your Niche? How do you fit into the community?

Resources• Essentials for survival biotic and abiotic

• What are ours?

• Give an animal example what does it need to survive?

Competition• Think about Food Webs

• There are multiple animals competing for the same resource sometimes.

• Example?• Intraspecific and Interspecific

Competitive Exclusion Principle• Competition between different species will usually cause

one to die out. Winner and Loser.• Usually less competitive species die out• “No two species can occupy exactly the same niche in

exactly the same habitat at exactly the same time.”• We don’t usually find species whose niches overlap too

much

Dividing Resources• Birds occupying different levels of the tree the birds divide

the resources available

Predator-Prey Relationships• Predator what does it do?• Predators determine where prey can live and feed• Predators play a role in determining the size of prey

populations• Example of a predator/prey relationship

Herbivore-Plant Relationship• Affect size and distribution of plant populations in a

community places plants can grow and survive

Keystone Species• Changes in a population of a species• They cause dramatic change in community

• Example: Sea Otters that eat urchins in the pacific coast, urchins eat kelp, kelp becomes over populated making kelp beds.• Sea otters were hunted for furs, when their population decreased kelp

almost vanished too. Why?

What Happened?• Without the predators, the urchins ate all the kelp. • Without kelp habitat many seabirds disappeared too, they

lost kelp habitat• Sea otters became a protected species, now urchins are

dying, and kelp beds are prospering

Symbiosis• A relationship where species live closely together• Symbiosis means “Living Together”

• Mutualism• Parasitism• Commensalism

Mutualism• A relationship where both species gain something from

the relationship• Clown Fish “Nemo” and the Sea Anemone

Parasitism• One species benefits while other is harmed or weakened

• Tape Worm and Human• Dog and Flea

Commensalism• One organism benefits while other is neither harmed nor

benefits from the relationship• Whale and Barnacle