Community Ecology

Question 1

What is a biological community?

Answer 1

Assemblage of populations of various species living close enough for potential interactions

Question 2

What is the species richness of a community?

Answer 2

The number of species present

Question 3

What is the primary productivity of a community?

Answer 3

The amount of energy produced by it

Question 4

What are the two views of structure and functioning of communities (and who is responsible for each of them)?

Answer 4

The individualistic concept; H.A. Gleason

The holistic concept; F.E. Clements

Question 5

What is the individualistic concept?

Answer 5

A community is nothing more than an aggregation of species that happen to occur together at one place. Favored by most ecologists today.

Question 6

What is the holistic concept?

Answer 6

A community is an integrated unit; more like a superorganism than the sum of its parts.

Question 7

How do the species from a community respond to changing environmental conditions?

Answer 7

They respond independently from one another.

Question 8

What are the two types of interactions that can occur within a community?

Answer 8

Interspecific interactions and intraspecific interactions

Question 9

What are the symbols used for the effects of interspecific interactions?

Answer 9

+ or - or 0 (no effect in any known way)

Question 10

What is an ecological niche?

Answer 10

The total of an organism’s use of biotic and abiotic resources in its environment. Combination of habitat, how the organism makes a living and the role performed in the community.

Question 11

What is interspecific competition?

Answer 11

A +/- interaction that arises from competition for a resource that is in short supply.

Question 12

What are the two types of interspecific competition (with short description)?

Answer 12

Interference competition (from physical interactions) `
Exploitative competition (from consommation of the same resources)

Question 13

What is the difference between the fundamental and realized niche?

Answer 13

The realized niche is the actual niche, which may be smaller than the fundamental niche due to competition.

Question 14

Give an example of competition for niche occupancy (and who is responsible for the study)?I

Answer 14

Competition of Chthamalus stellatus and Semibalanus balanoides for rocky shores. Jo Connell found that for the second, fundamental and realized niches are the same but not for the first.

Question 15

What is the competitive exclusion principle?

Answer 15

Principle that states that two species competing for limiting resources cannot coexist indefinitely in the same place. One will eliminate the other locally.

Question 16

Who is responsible for the experiments on competitive exclusion and what were they on?

Answer 16

Experiments by Gause (walmart version of Gauss) and experiments on three species of Paramecium

Question 17

What is a niche overlap?

Answer 17

The fact that species can coexist if their realized niches do not overlap.

Question 18

What is resource partitioning and what does it result from?

Answer 18

The fact that species can avoid competition by living in different portions of the habitat or by using different resources. It results from natural selection.

Question 19

Who studied resource partioning, on what, and what did he observe?

Answer 19

MacArthur studied it on five species of warblers (birds). They all evolved to utilize a different portion of the tree.

Question 20

3 possible outcomes from predation for Didnium vs Paramecium

Answer 20

1: Predator eliminates prey and then dies due to lack of food.
2: Prey hides in sediment but predator eats those in clear fluid and then dies because no more food.
3: Prey introduced in successive intervals and there is a cyclical pattern.

Question 21

Give 4 examples of adaption by the prey to diminish the probability of capture

Answer 21

Cryptic coloration (or camouflage), chemical defenses, warning coloration, and mimicry.

Question 22

What are the two types of mimicry and what is the difference between the two?

Answer 22

Batesian mimicry and mullerian mimicry. In batesian, a harmless specie mimics a dangerous one but in mullerian, several species resemble one another and the predators learn to avoid them.

Question 23

What is herbivory?

Answer 23

Type of predation (+/-) where herbivore eats plants.

Question 24

2 plant adaptations against herbivores

Answer 24

Morphological defenses (like spines and thorns) and chemical defenses.

Question 25

What is symbiosis?

Answer 25

When two organisms interact in elaborate (and more or less permanent) way.

Question 26

What are the three types of symbiosis?

Answer 26

Commensalism, mutualism and parasitism

Question 27

What is commensalism and one example?

Answer 27

Interaction that benefits one but does not harm or benefit the other (+/0). E.g. barnacles living on whales.

Question 28

What is mutualism and one example?

Answer 28

Interaction that benefits the two species (+/+). e.g., clowifish and anemones

Question 29

What is parasitism and one example?

Answer 29

A +/- interaction where the parasite nourishes itself from the host (harmed). e.g., humans and hook worms

Question 30

What are the two types of parasites with simple description?

Answer 30

Endoparasites (within body host) and ectoparasites (on external surface of the host).

Question 31

What is coevolution?

Answer 31

The fact that the predator and the prey may each one evolve to get better at eating the other or not being eaten. Like an “arms race.”

Question 32

What is succession and what are the two types?

Answer 32

The fact that communities change (often from simple to more complex) after disturbances. Two types are primary and secondary succession.

Question 33

What is stablilty?

Answer 33

The ability of a community to persist in the face of a disturbance.

Question 34

What are disturbances?

Answer 34

Events like fire, weather, or human activities that can alter communities. Some are routine.

Question 35

What is primary succession?

Answer 35

Succession that begins in a lifeless area where soil has not yet formed. Initially, only prokaryotes may be there, but then mosses and lichens colonize and develop soil. After soil development, grasses, tree sprouts and seeds are blown or carried from neary areas and then a forest may eventually be established (climax community).

Question 36

What are eutrophic and oligotrophic lakes?

Answer 36

Oligotrophic lakes are poor in nutrients. Eutrophic lakes are rich in nutrients and eventually fill in sediments, which may result in the development of forests.

Question 37

What is secondary succession?

Answer 37

Occurs in an area where the community has been removed due to a disturbance but the soil is still intact. Then, herbaceous species brought from wind grow. Then, woody shrubs replace the herbaceous species and these can be repaced by forest trees.

Question 38

Why does succession happen?

Answer 38

Species alter the habitat and resources available in ways that favour other species.

Question 39

What is tolerance concept?

Answer 39

Early successional species characterized by r-species tolerant of harsh conditions.

Question 40

What is facilitation?

Answer 40

K-selected species replace r-selected species.

Question 41

What is inhibition?

Answer 41

Changes in habitat caused by one species inhibit the growth of the original species