populations and ecosystems (TO)

Question 1

Within a population of a species, there can be a wide
range of phenotypes. State the two overall causes of
this:

Answer 1

environmental factors
genetic factors

Question 2

Name 3 selection pressures that can drive natural
selection.

Answer 2

predation
disease
competition

Question 3

Define evolution

Answer 3

The change in the allele frequency over many
generations in a given population

Question 4

define genetic drift

Answer 4

The change in the allele frequency within a population
between generations.

Question 5

What are the three types of selection that occur?

Answer 5

stabilising
directional
distruptive

Question 6

Which type of selection leads to speciation?

Answer 6

disruptive

Question 7

Does genetic drift have a bigger impact on smaller
or larger populations and explain your answer?

Answer 7

The smaller a population, the greater the proportional
impact changes in allele frequencies will have. This is
why evolution often occurs more rapidly in smaller
populations.

Question 8

define speciation

Answer 8

Speciation is the process that results in the creation of
new species.

Question 9

Different species of palm tree, all located on the
same island, flower at different times of the year. All
these palm trees have a common ancestor. Describe
how new species of palm trees would have arisen
(5 marks)

Answer 9

1.occurs in the same habitat / environment /
population;
2.Mutation/s cause different flowering times;
3.Reproductive separation / isolation or no gene
flow
4.Different allele/s passed on / selected OR change
in frequency of allele/s
5.Disruptive (natural) selection;
6.Eventually different species cannot (inter)breed
to produce fertile offspring;

Question 10

Define succession

Answer 10

The change in an ecological community over time.

Question 11

What is the difference between a primary and
secondary succession?

Answer 11

A primary succession starts with a pioneer species
colonising bare rock or sand. In a secondary succession,
there is disruption and the plants are destroyed.
Succession starts again, but the soil is already created.

Question 12

What is a pioneer species and give an example?

Answer 12

The first organism to colonise e.g. lichen

Question 13

what is meant by climax community?

Answer 13

The final seral stage where the ecosystem is most stable

Question 14

What causes the abiotic factors to become less harsh during a succession?

Answer 14

as organisms die and decompose it creates thicker and more nutrient-rich soil (humus).

Question 15

Why do species become outcompeted during a
succession?

Answer 15

The new species are better adapted to the environment

Question 16

What happens to the biodiversity as succession
progresses?

Answer 16

it increases

Question 17

how can managing succession be used to conserve
habitats?

Answer 17

By maintaining earlier stages in succession, and
preventing a climax community, a greater variety of
habitats are conserved and therefore a greater range of species.