Genetic Diversity

Question 1

Q6.The Amazonian forest today contains a very high diversity of bird species.
• Over the last 2 000 000 years, long periods of dry climate caused this forest to
separate into a number of smaller forests.
• Different plant communities developed in each of these smaller forests.
• Each time the climate became wetter again, the smaller forests grew in size and merged to reform the Amazonian forest.
(a) Use the information provided to explain how a very high diversity of bird species has developed in the Amazonian forest.

Answer 1

M6.(a)
1.
No interbreeding / gene pools are separate / geographic(al) isolation; Page 5
Neutral: allows a comparison
Neutral: ensures results are due to the independent variable Reject: ‘insecticide’
Accept: ‘pesticide’
(More) weeds killed so more crops / plants survive / higher yield / less competition;
High concentrations (of herbicide) harm / damage / kill / are toxic to crops / plants;
1
Accept: ‘pesticide’
Neutral: ‘insecticide’
Accept: use of figures (eg 400+)
Reduced plant diversity / fewer plant species / fewer varieties of plant;
Accept: ‘weed’ for ‘plant’
Neutral: fewer plants
Accept: only one crop species remains
Fewer habitats / niches;
Q Neutral: fewer homes / shelters Fewer food sources / varieties of food;
Neutral: less food
2
3
[8]

(b)
Accept: all marks if answer written in context of producing increased diversity of plants
1 Do not award this mark in context of new species being formed and then not interbreeding
1 Accept reproductive isolation as an alternative to no interbreeding
2. Mutation;
2 Accept: genetic variation
3. Different selection pressures / different foods / niches / habitats;
3 Accept: different environment / biotic / abiotic conditions or named condition
3 Neutral: different climates
4. Adapted organisms survive and breed / differential reproductive success;
5. Change / increase in allele frequency / frequencies;
5

Question 2

Speciation is far less frequent in the reformed Amazonian forest. Suggest one reason for this.

Answer 2

Similar / same environmental / abiotic / biotic factors / similar / same selection pressures / no isolation / gene flow can occur (within a species);

Question 3

Explain the relationship between the concentration of herbicide and the mean index of diversity of insects.

Answer 3

Reduced plant diversity / fewer plant species / fewer varieties of plant;
Accept: ‘weed’ for ‘plant’
Neutral: fewer plants
Accept: only one crop species remains
Fewer habitats / niches;
Q Neutral: fewer homes / shelters Fewer food sources / varieties of food;
Neutral: less food