L12 - Abundance and regulation

Question 1

If density-dependent biotic interactions determine population size, what does this mean?

Answer 1

That the population fluctuates due to their density, limited from either above or below

Question 2

Define a) regulation b) abundance

Answer 2

a) regulation - can only occur as a result of density-dependent processes
b) Abundance is determined by all factors and all processes, whether they are dependent or independent of density

Question 3

If a population were unregulated what would occur?

Answer 3

Extinction or unrestrained growth

Question 4

How could we tell what factors are causing population fluctuations?

Answer 4

sampling, and comparing the numbers to the total population size you can see how important the factors is

Question 5

Is the key-factor always population regulating?

Answer 5

No, actually the key-factor is not normally regulating and in fact it is other smaller factors that are the density dependent ones

Question 6

What is a community?

Answer 6

A community is a unit of the natural world, a range of different species of different proportions doing different things.

Question 7

What is a community the sum of?

Answer 7

The constituent species + their interactions

Question 8

By what 2 factors can we assess a community?

Answer 8

a) species richness - the number of species

b) equitability - their relative abundance

Question 9

Define succession

Answer 9

The directional and continuous pattern of colonisation and extinction on a site by species populations

Question 10

Describe the pattern of succession

Answer 10

Early succession: few species as there are only a few resources
Late succession: previous species have died and degraded, increasing the nutrient content of the soil, this allows for more complex species to colonise