community ecology

Question 1

Interactions between species:

Answer 1

1. Competition (-/-)
2. Exploitation (+/-)
   a. Predation
   b. Herbivory
   c. Parasitism
3. Positive (+/+, +/o)
   a. Mutualism
   b. Commensalism

Question 2

Competition (-/-)

Answer 2

a) Niche Overlap - two species have similar requirements in the same habitat
b) Competitive Exclusion two species competing for the same resources cannot coexist
c) Resource Partitioning - Species use resources differently to minimize overlap. Reduces competition, avoiding exclusion.
d) Character Displacement - Characteristics diverge more in sympatric populations of two species than in allopatric populations of the same two species

Question 3

Exploitation (+/-)

Answer 3

a. Predation
b. Herbivory
c. Parasitism

Question 4

Predator Adaptations:

Answer 4

a) Pursuit
b) Ambush = sit-and-wait predators.
c) Chemical Attack – stinging predators paralyzing prey
d) Mimicry – looking like another species to approach prey. Mimic octopus.

Question 5

Prey Adaptations:

Answer 5

a) Escape – RUN!!!
b) Chemical defenses – poison, irritation, repellency, reflex bleeding
c) Thanatosis – play dead
d) Cryptic coloration = Camouflage – hide by disguise
e) Aposematic coloration - warning coloration
f) Mimicry

Question 6

Mimicry

Answer 6

1. Batesian mimicry - the mimic lacks the defensive capabilities of its model
2. Müllerian mimicry - two organisms share the same anti-predation defense and mimic each other

Question 7

Mutualism

Answer 7

• an interaction between two species that benefits each of them (+/+).
  1) Obligate mutualism (species cannot live without each other). e.g. gut symbionts, lichens. Symbiosis.
  2) Facultative mutualism (both species can survive alone) e.g. cleaner fish, ant plants

Question 8

Commensalism

Answer 8

one organism benefits without affecting the other. (+/0 )
e.g. 360 species in gopher tortoise burrow; cattle egrets and their cattle

Question 9

dominant species

Answer 9

The most abundant or highest biomas in a community
Two hypotheses: a) good competitors or b) good at avoiding predators

Question 10

Keystone species

Answer 10

a species that has a great effect on the structure of the community it is a part of. Removal of the keystone species leads to community collapse.

Question 11

Ecosystem Engineers

Answer 11

“Foundation species” change ecosystem
* Beavers and their dams

Question 12

bottom-up model

Answer 12

model of community organization proposes a unidirectional influence from lower to higher trophic levels.
Nutrients >Producers>Herbivore>Predator

Question 13

top-down model

Answer 13

trophic cascade model. Control comes from the trophic level above. (some freshwater communities)
Nutrients<Producers<Herbivore<Predator

Question 14

Disturbance

Answer 14

influences diversity and stability something that alters ecosystems by removing organisms or altering resource availability. eg. Storm, fire, flood, drought, humans…