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