1.Review- What is a niche
Use Analogies- How is a niche like a profession. In
ecological terms, describe your niche.
2.Review- What is symbiosis. What are the major type
of symbiosis.
Explain- Bacteria living in a cow’s stomach help the
cow break down the cellulose in grass, gaining
nutrients in the process. Is this an example of
commensalism or mutualism- explain.
Apply Concepts- What is the difference between a
predator and a parasite- explain
3.Review- What is a keystone species.
Infer- How might a dramatic decrease in vegetation
lead to a decrease in a predator species.
CH 4 ECOSYSTEMS AND COMMUNITIES
4.2 Niches and
Community Interactions

Community
 Interacting

populations at the same time and place
Ecosystem
 The
community and its environment (abiotic factors).

Niche
 Role
in community, it’s job or what it does
 Includes biotic and abiotic factors

Habitat
 Physical


place where it lives
No two organisms share exactly the same niche in
the same habitat
Niche and Habitat of
 Your
pet dog Spot
 Oak tree
 You.
Tolerance

Ability to survive and reproduce under a range of
environmental circumstances
 Farther
than the optimal the greater the stress
 More energy to maintain homeostasis and less energy
left for growth and reproduction.
Competition


Occurs when organisms attempt to use the same
limited ecological resource in the same place at the
same time
Intraspecific Competition
 Between

members of the same species
Interspecific Competition
 Between
members of different species.
The Competitive Exclusion Principle


No two species can occupy exactly the same niche
in exactly the same habitat at exactly the same
time
One species will be better at competing for limited
resources and will eventually exclude the other
species.
The Competitive Exclusion Principle


Dashed Lines- Cultures grown separately
Solid Lines- Cultures grown together.
Dividing Resources


Species usually divide
resources rather than
compete over them
Using slightly different
resources results in
different niches.
Predator-Prey Relationships

Predation
 One

organism kills and eats the other one
Predators can affect the size of prey populations in
a community and determine the places prey can
live and feed.
Herbivore-Plant Relationships

Herbivory
 Interaction
where a herbivore feeds on producers
 Can affect both the size and distribution of plant
populations and determine where certain plants can
survive and grow.
Keystone Species

Species that plays major role in the structure of the
entire community
 Beaver.
Relationships Review

Symbiosis


Organisms of different species that live in direct physical
contact
Predator-prey
Relationship where one organism kills and eats the other
one
 Win/lose (+,-)


Parasitism
Relationship where one organism lives off another one
without trying to kill it
 Win/lose (+,-).

Relationships Review

Competition
Relationship where both organism want the same resourcefood, habitat
 Lose/lose (-,-)


Mutualism
Relationship where both organisms benefit
 Win/win (+,+)


Commensalisms
Relationship where one organism benefits and the other is
unaffected
 Win/nothing (+,0)


More types

Lose/win (-,+).