Lecture 29

Question 1

What is a biological community?

Answer 1

Populations of different species living and interacting in the same area.

Question 2

: Three major interspecific interactions?

Answer 2

Predation/Herbivory (+/-)
Competition (-/-)
Symbiosis: parasitism (+/-), mutualism (+/+), commensalism (+/0)

Question 3

What is facilitation in ecology?

Answer 3

When one species indirectly benefits another without direct contact (e.g., black rush improving soil).

Question 4

What is an ecological niche?

Answer 4

A: The role and resource use of an organism in its environment.

Question 5

Difference between fundamental and realized niche?

Answer 5

Fundamental: potential niche
Realized: actual niche after competition

Question 6

What is resource partitioning?

Answer 6

A: Species coexist by using resources differently (e.g., lizards using different tree zones).

Question 7

Two components of species diversity?

Answer 7

Richness: number of species
Evenness: relative abundance

Question 8

Why do food chains rarely exceed 5 levels?.

Answer 8

Only ~10% of energy transfers to the next level; higher levels need more energy and are less stable

Question 9

What is a keystone species?).

Answer 9

A species that has a large impact on its community despite not being the most abundant (e.g., sea otters

Question 10

What caused the 1990s sea otter decline?

Answer 10

Killer whale predation after changes in their food availability.

Question 11

Difference between bottom-up and top-down control?

Answer 11

Bottom-up: nutrients → plants → herbivores → predators
Top-down (trophic cascade): predators control herbivores → protect plants