Competition Fundamentals

Question 1

E.g.s of resources

Answer 1

Something that can be used up/consumed

• food
• mates
• space
• refuges (e.g. nest sites)

Question 2

What are the forms of competition

Answer 2

Scramble/exploitative
Interference/ contest
Apparent

Question 3

Scramble/exploitative competition

Answer 3

Indirect
E.g. caterpillars eating
Approximately equal resource division available to all organisms

Question 4

Interference/contest competition

Answer 4

Direct
E.g. fighting for mates
Occurs between individuals via aggression
Can help to stabilise dynamics

Question 5

Apparent competition

Answer 5

Between two orgs. Not mediated by a resource
Indirect
E.g. shared predator or parasites

Question 6

Example of apparent competition

Answer 6

Native red squirrel replaced by grey squirrel:

• grey squirrels carry paradox virus but are unaffected
• red squirrels have severe reaction (similar to myxomatosis) and usually die of secondary infection
• they compete directly too but wouldn’t decline so quick without paradox

Question 7

Outcomes of competition

Answer 7

Proximate effects
- lost food, mates and territory
Ultimate effects
- reduced fecundity, survivorship

Question 8

Intraspecific competition

Answer 8

within a species

• density dependent control of pop size
• can drive evolutionary changes (speciation)

Question 9

Interspecific competition

Answer 9

Between species

• usually reduced populations of both competitors
• can cause extinction of one species
• competitive exclusion principle (Gause’s law) = two species with same resources cant coexist.

Question 10

Common outcomes of inter-specific resource competition modelling

Answer 10

• normally one species will out compete the other
• ecological consequences = drives niche expansion
• evolutionary diversification
• often the species that thrives better or has better carrying capacity alone, does less well when in competition = density dependent