IV. Interactions in the Ecosystem (5.2 – Species Interactions)
A. Niche
1. Definition- An organism’s use of resources and it’s
functional role in a community.
2. A summary of everything an organism does and
when & where it does it
3. Includes what food, how & when reproduction,
interactions with others
4. Example – your seat in this classroom – your
personal space, materials, climate, and
resources… AND what you do with everything!
5. All members of a species are adapted to
similar niches, but not the SAME niche
a. Two species in same niche?
Compete for resources – one either has
to move out or die!
b. example of similar niches –
Anolis lizard, you and your table
partner’s seat
6. Fundamental niche
Definition - the full (possible) niche of a species the niche an organism COULD occupy
7. Realized niche Definition- a niche restricted by competition where an organism actually lives.
8. Competitive exclusion
Definition – when one species completely excludes
another species from any/all resource use
due to direct competition for the same niche
a. Example: You and a roach for your seat in class
b. Zebra Mussels (pg. 134) – Lake Erie & Hudson
B. Competition (pg. 48)
1. Definition –when organisms fight for the same
limited resource
2. Needed resources – food, water, shelter…
a. Intraspecific - same species
Ex: Two male lions for control of pride
b. Interspecific - different species
Ex: Lion & Leopard or Cheetah for Zebra
C. Predators & Prey
1. Prey
a. Definition – organism that gets eaten by
another (predators)
2. Predator
a. Definition – organism that hunts, captures kills
and consumes an individual of another
species
b. Top of food chain – rarely hunted or eaten
c. Can be herbivores (depends on definition!)
example – a cow kills and eats grass
d. Keep prey populations in check
e. Increase niche diversity by lowering a prey
population
1.) creates open niches for other species.
2.) Increases resources
f. Keystone Predator –a species that has strong or
wide-reaching impact on a community
(the Otter – figure 27, pg 148)
3. Population Cycles
a. The changing population size of the prey species
controls the population size of the predator
species
example - Lynx and Snowshoe Hare
Lynx
Snowshoe Hare
Snowshoe Hare
Kill the bunnies