Lecture 10 - DA

Question 1

What kind of interaction is competition?

Answer 1

Harms both parties involved.

Question 2

What kind of interaction is predation/parasitism?

Answer 2

Harms one, benefits the other.

Question 3

What kind of interaction is mutualism?

Answer 3

Benefits both parties.

Question 4

What kind of interaction is commensalism?

Answer 4

Benefits one, doesnt affect the other.

Question 5

What kind of interaction is ammensalism?

Answer 5

Harms one, doesnt affect the other.

Question 6

Define intraspecific competition and interspecific competition.

Answer 6

Intra - competition between individuals of a single species for resources.
Inter - competition between two different species for resources.

Question 7

Define resource exploitation.

Answer 7

Reducing resources available for a competitor.

Question 8

Define interference competition.

Answer 8

Preventing a competitor from accessing a resource.

Question 9

Define symmetrical competition.

Answer 9

When the magnitude of impact on each species is the same.

Question 10

Define asymmetrical competition. What does this mean for one of the species?

Answer 10

When the magnitude of impact on each species is the different. Therefore one species is competitively different.

Question 11

What is the zero growth isocline? What happens if above or below the isocline?

Answer 11

Is a solid linear relationship, where the two axes represent abundances. If above the isocline, growth will be negative and will drop to the isocline. If below, the growth is positive, and will rise to the isocline.

Question 12

If species 1 isocline is above species 2, what 2 things can be said?

Answer 12

Species 1 always excludes species 2

Species 1 is always a superior competitor

Question 13

What can be said if two species isoclines are in stable equilibria? What determines where things will go eventually, and where is the site of unstable equilibria? What does this kind of relationship indicate about intra/interspecific competition, and what does this suggest about which species can exclude the other?

Answer 13

Species at an initial disadvantage will be excluded. The intersection is the site of unstable equilibrium, and a slight deviation will send it off on a trajectory.
Indicates individuals of a species compete more strongly with other species versus members of their own species.
Therefore both species can exclude each other, depending on who has the initial disadvantage.

Question 14

What is coexistence on an isocline? What does this suggest about inter/intraspecific competition?

Answer 14

Is similar to a stable equilibrium, but there is no initial disadvantage, and therefore there is no capability to exclude one another.
Individuals of a species compete amongst themselves more strongly versus members of another species.

Question 15

Name the four outcomes in terms of isoclines.

Answer 15

Predictable exclusion of one species x2
Exclusion dependent on initial density
Stable coexistence

Question 16

When does stable coexistence occur?

Answer 16

Only when interspecific competition is weaker than intraspecific competition in both species.

Question 17

What is interspecific competiton created by?

Answer 17

Niche overlap.

Question 18

Define the competitive exclusion principle.

Answer 18

If the niche of two species overlaps entirely, one species will exclude the other.

Question 19

What does coexistence require in terms of niches? What allows for coexistence aside (aside from competition parameters)?

Answer 19

Niche differentiation.

Environmental heterogeneity allows coexistence.

Question 20

Define character displacement. Give an example.

Answer 20

Morphiological difference between populations of a species that are allotropic or sympatric with a competitor. Finches with different beak sizes allow for a different diet.

Question 21

What effect does evolution have on competition?

Answer 21

Evolution acts to reduce competition.

Question 22

What effect does niche differenciation have on competition?

Answer 22

Reduces competition.

Question 23

What happens to a competitor when exclusion occurs?

Answer 23

Exclusion eliminates a competitor.

Question 24

What can mask the presence of competition?

Answer 24

The consequences of competition.

Question 25

Define a true predator.

Answer 25

Consumes prey entirely, kills them quickly.

Question 26

How does a grazer treat prey?

Answer 26

Partially consumes prey, rarely kills them.

Question 27

How does a parasite treat prey?

Answer 27

Partially consumes prey, rarely kills them.

Question 28

Define parasitoid.

Answer 28

Insects whose larvae develop in a single prey/host and will eventually kill and consume it.

Question 29

In the predator-prey relationship, there is a lag where prey grow unchecked for a while before predator numbers catch up. Explain 2 reasons why this is the case.

Answer 29

Due to the numerical response of the predator - longer generation time than prey
Functional response of the predator - saturation of individual predator numbers allows the prey population until predator numbers begin to grow.

Question 30

Why do prey rebound rather than go extinct in the predator-prey relationship?

Answer 30

Reduced predation pressure due to predator decline when prey numbers become rare.
The threshold provides a refuge for prey.

Question 31

Are two species ever in relative isolation?

Give an example using foxes, pigs, and eagles.

Answer 31

They are rarely ever in isolation, due to indirect effects.
For example, pigs are introduced, and their introduction supports a higher eagle population.
Therefore more eagles to prey on foxes.
Therefore an indirect negative effect of foxes by pigs despite no shared resources between the two.

Question 32

Define apparent competition.

Answer 32

Indirect interaction via a shared enemy, or other species on the same trophic level.

Question 33

Define a superpredator.

Answer 33

Organism with a direct negative effect on two prey species at different trophic levels.

Question 34

What effect does a superpredator have on lower level prey?

Answer 34

Indirect positive effect by reducing their predators.

Question 35

How is an omnivore truly defined?

Answer 35

Feeding on two different trophic levels.

Question 36

What competitor do predators consume, and what does this prevent?

Answer 36

Consumes the dominant competitor, preventing it from driving other species to competitive exclusion.