Intraspecific Population Regulation

Question 1

What is competition?

Answer 1

An interaction between individuals in which each is harmed by their shared use of a limiting resource.

Question 2

What consequences does competition have for…

Answer 2

Population dynamics (stability, abundance, etc.)
Spatial distribution of individuals and species Community structure (coexistence or extinction of species and their relative abundance)
Species evolution

Question 3

What is intraspecific?

Answer 3

population regulation can be seen in terms of competition between individuals of the same species, especially because such individuals compete for precisely the same resources.

Question 4

What is interspecific?

Answer 4

competition also occurs between individuals of different species, but can be diminished by niche differentiation (a key concept in community ecology)

Question 5

What does population regulation involve?

Answer 5

Density dependance.

Question 6

Why do populations not increase indefiniately?

Answer 6

• As resources become less available to an increasing number of individuals, birthrates decrease, mortality increases, and population growth slows.
• If the population declines, mortality decreases, births increase and population growth speeds up
• Positive and negative feedbacks function to regulate the population. Density dependent effects influence a population in proportion to its size.
• Density independent effects influence a population without regard to the number of individuals. For example, bad weather conditions.

Question 7

What is intraspecific competition?

Answer 7

competition among individuals of the same species.

Question 8

What is scramble competition?

Answer 8

when growth and reproduction are depressed equally across individuals in a population as the intensity of the competition increases.

Question 9

What is contest competition?

Answer 9

when some individuals claim enough resources while denying others a share.

Question 10

What is exlpoitation competition?

Answer 10

competing individuals don’t interact directly but use up the resource (zebras eating grass; plants using up water).

Question 11

What is interference compitition?

Answer 11

competing individuals interact directly, denying access to the resource (territory defence).
Chemical – chemicals produced by one individual inhibit(allelopathy) or kill another
Territoriality – defence of an area limits access to a resource by others; can regulate population growth (also intraspecific)

Question 12

What is self-thinning?

Answer 12

Decline in density and increase in biomass of the remaining population individuals.

Question 13

Population vs rate in K-scenarios

Answer 13

constant birth rate with increasing mortality
constant mortality with decreased birth rate
increased mortality with a decreasing birht rate.

Question 14

how does Intraspecific competition affects growth and development?

Question 15

how does intraspecific competition influecnes mortality rates?

Answer 15

Self-thinning
mortality increases as density increases.

Question 16

how does intraspecific competition reduce reproduction?

Answer 16

In dense populations it is more difficult to find enough food to sustain the organism and therefore it takes longer for the organism to reach sexual maturity.
Fertility is desity-dependant.
same for plants, more dense population = less seeds produced.

Question 17

Why is high density stressful to individuals?

Answer 17

One hypothesis of population regulation in animals is that increased crowding and social contact cause stress:
- stress triggers hormonal changes that can suppress growth,
- curtail reproductive functions,
- and delay sexual activity
- Pheromones in the urine of Female house mice (Mus musculus) from high density populations delayed puberty in juvenile females

In mammals, social stress among pregnant females may
- increase mortality of the young in the fetal stage (unborn)
- cause inadequate lactation, stunting the growth and development of nursing young

Increase chances of diseases.
Instead of trying to cope with the stress organisms disperse leaving the organisms to find vacant habitats.

Question 18

How can dispersal be density dependant?

Answer 18

Dispersal is a constant phenomenon in populations:

• Dispersal does not function directly as a mechanism of population regulation in response to the overexploitation of resources or crowding.
  [For example, lemmings do not fling themselves into the ocean to make space for the other lemmings]
• Dispersal can function to regulate population growth if the dispersal increases as population increases.

When intraspecific competition at home is intense, dispersers can relocate to habitats where resources are more accessible, breeding sites more available, and competition less intense.
- reduces the risk of inbreeding
- incur risks that come with living in unfamiliar terrain.

Question 19

how does social behaviour function to limit populations?

Answer 19

• Many species live in groups with some kind of social organization
• In some populations, the group structure is crucial to acquiring resources (as with predators that hunt in packs) and maintaining defence
• The organization, however, is often based on aggressiveness, intolerance, and the dominance of one individual over another. Two opposing forces are at work. One is mutual attraction of individuals; the other is a negative reaction against crowding—the need for individual space.

Question 20

What is home range?

Answer 20

The area that an animal normally uses during a year.

Question 21

What is a territory?

Answer 21

an area that an animal defends. The result of defended territories is a regular distribution pattern.

Question 22

What is the role of environmental stress?

Answer 22

In white-tailed deer living in Minnesota, the average number of fawns produced decreases with the amount of snow.

The annual change in population is inversely related to the previous winter’s snow accumulation

Density Independent Factors