Community Ecology

Question 1

What is a community?

Answer 1

-Community: interacting populations at a particular location

Question 2

What is species richness and primary productivity?

Answer 2

• Species richness: number of species present

- Primary productivity: amount of energy produced in a system

Question 3

What is a niche?

Answer 3

The total of all the ways an organism uses the resources of its environment
-ex. space utilization, food consumption, temperature range

Question 4

Describe the different kinds of competition?

Answer 4

• Interspecific: occurs when two species attempt to use the same resources and there is not enough resources to satisfy both
• Intraspecific: same species fight over same resources
• Interference: physical interactions over access to resources
• Exploitation: consuming same resource

Question 5

What are the two kinds of niche?

Answer 5

• Fundamental: entire niche that a species is capable of using based on physiological tolerance limits and resource needs
• Realized: actual set of environmental conditions, presence or absence of other species, in which species can establish a stable population

Question 6

What is the competitive exclusion principle?

Answer 6

-Species with identical resource requirements cannot coexist

Question 7

Describe resource partitioning?

Answer 7

• The niche is subdivided to avoid direct competition
• Often seen in similar species that occupy same geometric area
  ex. Lizards are on different parts of tree to obtain food and not have to compete

Question 8

What is character displacement?

Answer 8

-Differences in morphology evident between sympatric species

Question 9

What is predation?

Answer 9

• Consuming of one predator by another

- It strongly influences prey populations

Question 10

What is coevolution?

Answer 10

• Both a predator and prey evolve due to each other

ex. gazel and cheetah evolve to run faster

Question 11

Describe chemical defenses?

Answer 11

-May make toxins to make predators sick

Question 12

Describe defense coloration?

Answer 12

-Poisonous animals may have warning coloration

Question 13

Describe the two kinds of mimicry?

Answer 13

• Batesian mimicry: mimics look like distasteful or predatory species
• Mullerian mimicry: several unrelated but poisonous species come to resemble one another

Question 14

What are the three kinds of species interactions?

Answer 14

• Commensalism: one species benefits, one is not effected
• Mutualism: both species benefit
• Parasitism: benefits one species and harms the other

Question 15

What are the kinds of external parasites?

Answer 15

• Ectoparasites: feed on exterior surface of an organism

- Parasitoids: insects that lay eggs on living hosts

Question 16

Describe internal parasites?

Answer 16

• Endoparasites: live inside host
• extreme specialization by the parasite as tow which host it invades
• many have complex life cycles that involve more than one host
  ex. Dicroceoelium dendriticum is a flatworm that lives in ants and causes them to climb to the top of grass blades so that they’ll get eaten by cattle

Question 17

Describe how predation reduces competition?

Answer 17

• Predators choice depends partially on relative abundance of the prey options
• Superior predators may be reduced in number by predation
• Allows other species to survive when they could have been outcompeted
  ex. starfish eat barnacles which allows other species to thrive instead of being overcrowded by explosive population of barnacles

Question 18

Describe indirect effects?

Answer 18

-Presence of one species may effect a second by the way of interaction with a third species

Question 19

What is a Keystone species?

Answer 19

• species whose effects on the composition of communities are greater than one might expect based on their abundance
• they can manipulate the environment in ways that create new habitats for other species
  ex. beavers

Question 20

Describe succession?

Answer 20

• communities have tendency to change from simple to complex

- organisms gradually move into an area and change its nature

Question 21

What is the difference between primary and secondary succession?

Answer 21

• Primary: occurs on bare, lifeless substrate
• Secondary: occurs in areas where an existing community has been disturbed but organisms still remain (ex. forest after a fire)

Question 22

What causes communities to constantly be changing?

Answer 22

• climate change
• species invasions
• disturbance events

Question 23

What is the intermediate disturbance hypothesis?

Answer 23

-communities experiencing moderate amounts of disturbance will have higher levels of species richness than communities experiencing either little or great amounts of disturbance