Ch. 54: Community Ecology

Question 1

How do two similar species co-exist in same niche without defying the competitive exclusion principle? (there is more than one possible answer here)

Answer 1

Resource partitioning: differentiation of ecological niches, enabling similar species to coexist in a community

Character displacement: a tendency for characteristics to be more divergent in sympatric population of two species than in allopatric populations of the same two species

Question 2

How are species restricted to a realized niche versus their potential niche?

Answer 2

Realized niche: the niche actually occupied by that species during resource partitioning

Potential (fundamental) niche: the area a niche could potentially occupy with no competition

Question 3

What is the advantage of Mullerian mimicry?

Answer 3

Mullerian mimicry: 2 or more unpalatable species resemble each other

• protection/safety
• reinforce a pattern for predators (so they have less to learn)

Question 4

How can plants defend themselves against predation if they can’t run away or hide?

Answer 4

mechanical or chemical

- thorns vs toxin (bitter taste)

Question 5

Is facilitation an example of symbiosis? Why or why not?

Answer 5

facilitation is an example of indirect symbiosis

Facilitation (+/+ or +/0): one species can have a positive effects on another species without direct and intimate contact

i. e. salt marsh with Juncus (foreground)
i. e. black rush makes the soil more hospitable for other plant species

Question 6

Which community is more resistance to environmental stress? Why?

Answer 6

The more richly diverse a community is, the more resistance it has to environmental stresses.

Question 7

Community interactions are classified by

Answer 7

whether they help, harm, or have no effect on the species involved

Question 8

Diversity and trophic structures characterize

Answer 8

biological communities

Question 9

Disturbance influences a species’

Answer 9

diversity and composition

Question 10

Biogeographic factors affect

Answer 10

community diversity

Question 11

Pathogens alter

Answer 11

community structure locally and globally

Question 12

(biological) community

Answer 12

an assemblage of populations of various species living close enough for potential interaction

i.e. carrier crab and sea urchin

Question 13

interspecific interactions

Answer 13

relationships between species in a community

• competition, predation, herbivory, symbiosis (parasitism, mutualism, commensalism) and facilitation
• can affect survival and reproduction of each species, and the effects can be summarized as positive (+), negative (-), or no change (0)

Question 14

Interspecific competition

Answer 14

(-/- interaction)

species compete for a resource in short supply

Question 15

Competitive exclusion

Answer 15

local elimination of a competing species

Principle: two species competing for the same limiting resources cannot coexist in the same place

Question 16

Ecological niche

Answer 16

the total of a species’ use of biotic and abiotic resources

AKA organim’s ecological role

ecologically similar species can coexist in a community if there are one or more significant differences in their niches

Question 17

Resource Partitioning

Answer 17

the differentiation of ecological niches, enabling similar species to coexist in a community

Question 18

Species’ fundamental niche

Answer 18

niche potentially occupied by that species

Question 19

Species’ realized niche

Answer 19

the niche actually occupied by that species

a species’ fundamental niche may differ from its realized niche
i.e. barnacles, spiny and golden mice

Question 20

Character Displacement

Answer 20

a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species

i.e. variation in beak size between Galapagos finches

Question 21

Predation

Answer 21

(+/- interaction)
- interaction where one species, the predator, kills and eats the other, the prey

• some feeding adaptions of predators: claws, teeth, fangs, stingers, poison
• prey defensive adaptions:
  = Behavioral: hiding, fleeing, forming herds or schools, self-defense, alarm calls
  = Morphological and physiological defense adaptions
  = cryptic coloration

Question 22

Cryptic coloration

Answer 22

AKA camouflages

makes prey difficult to spot

Question 23

Aposematic coloration

Answer 23

animals with effective chemical defense often exhibit bright warning coloration

Question 24

Batesian mimicry

Answer 24

a palatable or harmless species mimics an unpalatable or harmful model

Question 25

Mullerian mimicry

Answer 25

2 or more unpalatable species resemble each other

Question 26

Herbivory

Answer 26

(+/- interaction)

• an interaction in which an herbivore eats parts of a plant or alga
• led to the evolution of plant mechanical and chemical defenses and adaptations by herbivores

Question 27

Symbiosis

Answer 27

a relationship where two or more species live in direct and intimate contact with one another

Question 28

Parasitism

Answer 28

(+/- interaction)
- one organism, the parasite, derives nourishments from another organism, the host, which is harmed in the process

• many parasites have a complex life cycle involving a number of hosts
• some parasites change the behavior of the host to increase their own fitness

Question 29

Endoparasite

Answer 29

parasites that live within the body of their host

Question 30

Ectoparasite

Answer 30

parasites that live on the external surface of a host

Question 31

Mutualism

Answer 31

(+/+ interaction)
AKA mutualistic symbiosis

• an interspecific interaction that benefits both species

can be obligate or facultative

Question 32

Obligate Mutualism

Answer 32

one species cannot survive without the other

Question 33

Facultative Mutualism

Answer 33

both species can survive alone

Question 34

Commensalism

Answer 34

(+/0 interaction)
- one species benefits and the other is neither harmed nor helped

• hard to document in nature because any close association likely affects both species
• i.e. cows and birds ?

Question 35

Facilitation

Answer 35

(+/+ or +/0 interaction)
indirect symbiosis

• one species can have positive effects on another species without direct and intimate contact
  i. e. black rush makes the soil more hospitable for other plant species

Question 36

Species diversity

Answer 36

the variety of organisms that make up the community

• two components: species richness and relative abundance

Question 37

Species Richness

Answer 37

the total number of different species in the community

Question 38

Relative Abundance

Answer 38

the proportion each species represents of the total individuals in the community