E6

Question 1

What is competition?

Answer 1

An interaction between individuals, brought about by a shared requirement for a resource, leading to a reduction in survivorship, growth, and/or reproduction of at least some of the competing individuals concerned.

Question 2

What is intraspecific competition?

Answer 2

Organism grow reproduce and die, they are affected by the conditions in which they live and the resources they obtain, but no organism lives in isolation. Each is a member of a pop composed of individuals of its own species, each therefore has similar requirements, their combined demand for a resource may exceed immediate supply therefore they have intraspecific competition.

Question 3

What does intraspecific competition lead to?

Answer 3

Decreased resource intake per individual, and consequently decreased growth rate, fecundity, or survivorship. Therefore is survival of the fittest.

Question 4

In intraspecific competition what factors may play out?

Answer 4

Exploitation - each individual affected by the amount of resource that remains, interference - direct interaction. Individuals respond to the level of the resource. One individual may prevent another from exploiting a resource.

Question 5

In intraspecific competition what is one sided competition?

Answer 5

A strong early seedling will shade a stunted late one. A larger coral will grow over a small one. Weak competitions make a smaller contribution to the next generation - survival of the fittest

Question 6

How does density dependent mortality and fecundity play out with intraspecific competition?

Answer 6

High densities leads to intraspecific competition and therefore mortality. Intensity of intraspecific competition experienced is determined by the extent to which it is crowded or inhibited by immediate neighbours. Organism weighted densities. Unequal exploitation of resource.

Question 7

In intraspecific competition what is the law of constant final yield with density dependent growth?

Answer 7

When density is sufficiently high and resources become limited, the effects of competition will result in a constant biomass due to a proportional decrease in the size of the individuals.

Question 8

What is territoriality?

Answer 8

Active interference between individuals to defend an exclusive area against intruders using a recognisable pattern of behaviour. Territory availability varies by year depending on environmental conditions. Failure to occupy a territory = failure to reproduce.

Question 9

Territoriality is a…?

Answer 9

Cost-benefit strategy. Territory defence must be offset against the benefit of occupation. Sometimes fierce combat or more subtle mutual recognition. Still require energy to maintain. Need to benefit to be favoured by natural selection. Not just winners and losers as not all territory are equally valuable. Habitat quality and patch availability.

Question 10

What is interspecific competition?

Answer 10

One individual of a species deprives another of a different species of a vital resource, leading to slower growth, fewer progeny or greater risk of death of the inferior competitor.

Question 11

How can interspecific competition occur?

Answer 11

Resource can be consumed to depletion, species also influenced by factors such as temp, pH, salinity. Physical factors affect population growth rates but are not consumed or depleted

Question 12

What is an example of how interspecific competition can occur?

Answer 12

Tansley, two species of bedstraw, when grown alone each species could survive on both acidic and calcareous soils. When grown together soil type determined which could survive.
Tilman, diatoms when each species grown alone, stable pop size reached and silica concentrations reduced, when grown together competition ensued.
Wilson and tilman, comp should increase in intensity when resources are scarce

Question 13

How important is competition in ecological communities?

Answer 13

Has significant effects on wide range of organisms

Question 14

What is exploitation competition?

Answer 14

Species compete indirectly through their mutual effects on the availability of a shared resource.

Question 15

What is interference competition?

Answer 15

Species compete directly to access to a resource. Can occur in sessile species e.g. barnacle

Question 16

What is allelopathy?

Answer 16

A form of interference competition in which individuals of one species release toxins that harm another. E.g. spotted knapweed, released toxin to surrounding soils, which reduces germination and growth of native grasses.

Question 17

How is competition asymmetrical?

Answer 17

One species harmed more than another. Competition can also occur between distantly related species. Ants and rodents and seeds

Question 18

How can competition limit distribution and abundance of species?

Answer 18

Distribution of barnacle larvae overlapped throughout the upper and middle intertidal zones. Adult distribution did not overlap. Chthamalus stellatus in top and semibalanus balanoides found throughout rest of intertidal zone.

Question 19

What is competitive exclusion?

Answer 19

Competing species are more likely to coexist when they use resources in different ways. If the overall ecological niche requirements of a species are very similar to those of a superior competitor, the competition may drive it to extinction. Two species that use a limiting resource in the same way cannot coexist

Question 20

What is resource partitioning?

Answer 20

When species use a limited resource in different ways. E.g. lizard species live together in trees and shrubs and eat similar food, lizards used the space in different ways, resulting in reduction in competition.

Question 21

What factors affect the outcome of competition?

Answer 21

Environmental conditions, species interactions, disturbance and evolution. Environmental conditions can result in competitive reversal - the species that was the inferior competition in one habitat becomes the superior competitor in another.

Question 22

What impact do disturbances such as fires or storms have on interspecific competition?

Answer 22

Can kill or damaged individuals but create opportunities for others. E.g. some forest plant species require abundant sunlight and are found only where disturbance has opened the tree canopy. As trees recolonise and create shade, these plants cannot persist in the patch. Such species are fugitive species because they must disperse as conditions change.

Question 23

What can competition cause?

Answer 23

Evolutionary change, evolution has the potential to alter the outcome of competition.

Question 24

What can natural selection change?

Answer 24

Morphology of competing species and result in character displacement. NS results in the forms of competition species becoming more different over time. E.g. finches on Galapagos, sticklebacks in lakes.

Question 25

In spite of competition what occurs?

Answer 25

Communities which contain many species share scarce resources, resource partitioning is the only explanation for this. Species may also coexist if different species are superior competitors under different environmental conditions.