Populations - Competition

Question 1

Explain the theory of competition

Answer 1

Negative interactions between organisms for a limited resource drives selection - the winners of competition will increase their fitness

Question 2

Predict the outcomes of competitive interactions using graphs and competition coefficients

Answer 2

If alpha = 1, species are equally good competitors

If alpha > 1, species two is a better competitor

If alpha < 1, species one is a better competitor

If alpha = 0, there is no competition

Question 3

Define different competitive interactions

Answer 3

Scramble/exploitation: Indirect, reduces access to resources by using them

Interference: Direct, intentionally acts to reduce access to resources

Apparent competition: Caused by a third party, indirect, negative interaction without competition for resources

Question 4

Link concepts between physical environment, populations & competition

Question 5

Intraspecific competition

Answer 5

Between individuals of the same species

Question 6

Interspecific competition

Answer 6

Between individuals of different species

Question 7

What are the three types of competition?

Answer 7

Scramble/exploitation, interference, and apparent competition

Question 8

Scramble/exploitation competition

Answer 8

Indirect, reduce access to resource by using it

Question 9

Interference competition

Answer 9

Direct, actions intentionally reduce access to a resource

Question 10

Apparent competition

Answer 10

Looks like competition, but is really caused by a third factor (ex. parasites). An indirect, negative interaction without competition for a resource

Question 11

How can we test for competition?

Answer 11

Either observe behaviour and draw an inference, or experiment using the scientific method

(ex. grow plants separately and apart - is growth hindered? Supplement to determine what they are competing for)

Question 12

Competition coefficient

Answer 12

Converts numbers of species 1 into equivalent numbers of species 2 based on competitive ability

Question 13

State-space graph

Answer 13

Bivariate plots - density of one species vs. another, they increase in opposite directions

Question 14

Isocline

Answer 14

Single line with a negative slope on a state-space graph

Question 15

Know how to interpret state-space graphs - which species is the better competitor? Will they outcompete or coexist?

Answer 15

Whichever isocline is closest to the top right is the better competitor, unless the isoclines cross - this means that the species will coexist. If they converge to a single point the equilibrium is stable. If they do not converge, the coexistence in unstable and the outcome depends on the initial concentration of the species.