Competition

Question 1

How does competition affect each competing population?

Answer 1

-ve for both

anything 1 species takes makes it worse for the other & visa versa

Question 2

What is Liebig’s law of the minimum?

Answer 2

Each population should increase until the supply of most limiting resource constrains further growth

(Growth isn’t dictated by total resources available but the limiting factor)

Question 3

What are the 2 types of competition?

Answer 3

Intraspecific
- same species

Interspecific
- 2 or more species

Question 4

Which type of competition explains logistic growth?

Answer 4

Intraspecific

= 1 of the density-dependent factors that controls population growth

Question 5

In which 2 ways can competition occur?

Answer 5

Directly - through defending resources
–> interference competition e.g. releasing toxic chemicals or physical combat

Indirectly - through shared resources
–>exploitative competition e.g. plants compete for light

Question 6

What was the experiment used to test whether 2 species can coexist if they share the same resource?

Answer 6

Gause’s experimental test in Paramecium (protozoans)

Question 7

Describe Gause’s Paramecium experiment

Answer 7

Grew 2 species separately = both grew to max. capacity

Grew together
= couldn’t coexist

Question 8

The Lotka-Volterra model for the effect on growth of population 1 in presence of population 2 takes what into account?

Answer 8

The no. of species 2 present
&
The relative amount fo resource species 2 takes away compared to species 1

Question 9

What would happen if 2 species could coexist?

Answer 9

Both would reach a no. where their population would be stable
(dN/dt =0 for both species)

Question 10

What is an isocline?

Answer 10

Line connecting points of equal gradient

- regions where pop is stable & growth = 0

Question 11

What happens when 2 populations of diff species compete for the same resource?

Answer 11

Reduce each other’s growth

Question 12

What is the most common equilibrium when 2 populations of diff species compete for the same resource?

Answer 12

When pop 1 drives pop 2 to extinct or vice versa

Question 13

How can a stable coexistence be reached?

Answer 13

When each population limits its growth more than the growth of its competitor
(interspecific is smaller than intraspecific competition)

Question 14

What is competitive exclusion?

Answer 14

If 2 species use the same resource & share the same habitat
–> 1 competing species will eventually exclude the other

If 2 species co-exist in a stable enviro
- must be using somewhat different resources

Question 15

What is a fundamental niche?

Answer 15

The range of resources a species can survive & reproduce within

Question 16

What is a realised niche?

Answer 16

The actual resources a species use

- competitors & predators restrict the potential range

Question 17

What does a niche overlap show?

Answer 17

Similarity in how 2 species use resources

= intensity of competition when resources are limiting

Question 18

What is niche partitioning?

Answer 18

Species using the enviro differently in order to coexist

Question 19

What are the problems w/ assuming Competitive Exclusion Principle explains geographic distribution?

Answer 19

> Observed diff may be due to separate evolution that allows species to coexist
OR diffs among species are irrelevant to competition
- perhaps they never competed?
- resources may not be limiting?

Question 20

What was the experiment used to test the Competitive Exclusion Principle?

What did they find?

Answer 20

Tansley’s experiment on bedstraws

Competition - not diffs in niche - explains species distribution

Question 21

What are the evolutionary consequences of competition?

Answer 21

> if genetic variation within population for increased competitivity, competitiveness can evolve

> if variation in resource use exists, selection within population may favour avoidance of competition by evolving diff traits

Question 22

What is the character displacement hypothesis?

Answer 22

When 2 species utilise the same resource & have an overlapping geographic distribution…
their morphology may shift to avoid competition