selection and speciation

Question 1

Describe what is meant by speciation (allopatric)

Answer 1

• Geographical isolation;
• Separate gene pools / no interbreeding (between populations);
• Variation due to mutation;
• Different environmental/abiotic/biotic conditions / selection pressures;
• Selection for different/advantageous, features/characteristics/mutation/ /allele;
• Differential reproductive success / (selected) organisms survive and reproduce;
• Leads to change in allelic frequencies;
• Cannot breed/mate to produce fertile offspring;
• each population has become separate species each with its own gene pool.

Question 2

Describe what is meant by speciation (sympatric)

Answer 2

• NOT Geographical isolation;
• Leads to reproductive isolation
• Separate gene pools / no interbreeding (between populations);
• Selection for different/advantageous, features/characteristics/mutation/ /allele;
• Differential reproductive success / (selected) organisms survive and reproduce;
• Leads to change in allelic frequencies;
  Cannot breed/mate to produce fertile offspring.

Question 3

Changes in ecosystems can lead to speciation. In Southern California 10 000 years ago a number of interconnecting lakes contained a single species of pupfish.
Increasing temperatures caused evaporation and the formation of separate, smaller lakes and streams. This led to the formation of a number of different species of pupfish.
Explain how these different species evolved.

Answer 3

1. Geographical isolation;
2. Separate gene pools / no interbreeding (between populations);
3. Variation due to mutation;
4. Different environmental/abiotic/biotic conditions / selection pressures;
5. Selection for different/advantageous, features/characteristics/mutation/ /allele;
6. Differential reproductive success / (selected) organisms survive and reproduce;
7. Leads to change in allele frequency;
8. Occurs over a long period of time;

Question 4

Changes in ecosystems can lead to speciation.
A high concentration of copper in soil is toxic to
most plants. In some areas where the soil is
polluted with copper, populations of grasses are
found to be growing. These populations of grass
belong to a species also found growing on
unpolluted soils.
It has been suggested that a new species of
grass may evolve on soil that has been polluted
with copper.
Explain how this new species might evolve.

Answer 4

1. Variation/variety;
2. (caused by) Mutation;
3. Some plants have allele to survive/grow/live in high concentration of copper/polluted soils;
4. (Differential) reproductive success / adapted organisms reproduce;
5. Increase in frequency of advantageous allele;
6. No interbreeding (with other populations) / separate gene pool / gene pool differs (from other populations);

Question 5

Lord Howe Island in the Tasman Sea possesses two species of palm tree which have arisen via sympatric speciation. The two species diverged from each other after the island was formed 6.5 million years ago. The flowering times of the two species are different.
Using this information, suggest how these two species of palm tree arose by sympatric speciation.

Answer 5

1. Occurs in the same habitat / environment / population;
2. Mutation/s cause different flowering times;
3. Reproductive seperation / isolation
   OR
   No gene flow
   OR
   Gene pools remain separate;
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 6

What is genetic drift?

Answer 6

• Bottleneck;
• Random increase or decrease in allelic frequency;

Question 7

What is gene flow?

Answer 7

• Founder effect;
• Change in allelic frequency due to the migration of fertile individuals