7) Genetics, populations, evolution, and ecosystems

Question 1

Define phenotype

Answer 1

• Expression of genetic constitution of an organism/genotype;
• And its interaction with the environment;

Question 2

Define genotype

Answer 2

The genetic constitution of an organism;

Question 3

Define population

Answer 3

1. A group of organisms of the same species;
2. Occupying a particular space at a particular time;
3. That can potentially interbreed

Question 4

Define gene pool

Answer 4

All the alleles in a population

Question 5

The conditions under which the
Hardy-Weinberg Principle applies

Answer 5

• no mutation
• random mating
• large population
• population is isolated ( no flow of alleles into or out of population)
• no selection - (all alleles equally likely to be passed on to next generation)

Question 6

Evolution leading to allopatric
speciation

Answer 6

• Geographic(al) isolation
• Separate gene pools
• variation due to mutation
• different selection pressures
• Differential reproductive success
• Leads to change/ increase in allele frequency

Question 7

Why does speciation take a long time?

Answer 7

1. Initially one/few animals with favourable mutation/allele;
2. Individuals with (favourable) mutation/allele will have more offspring;
3. Takes many generations for (favourable) mutation/allele to become the most common allele (of this gene)

Question 8

Natural Selection in Resistant Strains

Answer 8

1. Some individuals in population naturally resistant/not killed by pesticide/antibiotic;
2. Due to mutation;
3. These survive when pesticide/antibiotic applied/non-resistant ones are killed;
4. To reproduce and pass on allele/gene (for resistance);
5. Increase in frequency of allele for resistance

Question 9

Effect of increased plant/animal diversity on
ecosystem

Answer 9

1. Increase in plant diversity leads to more types of food for animals;
2. Increase in variety of animals leads to increase in predator species;
3. Increase in niche/habitat;

Question 10

Define niche

Answer 10

1. Niche is the role that a species plays in within a community;
2. Includes food resources;
3. No two species can occupy identical niche;

Question 11

Predator-Prey Relationship

Answer 11

1. As pest numbers increase more food or predators, so they increase;
2. Increased predation of pests reduces numbers;
3. Low number of pests results in less food for predators, so their numbers decrease;
4. Low predator numbers allow pest population to rise as fewer are eaten

Question 12

Succession

Answer 12

1. colonisation/pioneering;
2. microscopic plants at start;
3. death / decomposition;
4. named change in environment e.g. increase in organic matter/stabilisation;
5. new species colonise once there is a change;
6. increase in number of species/diversity;
7. increase in total amount of living material/biomass/ more niches;
8. increase in nutrient availability;
9. change from more extreme conditions / more stability;
10. climax community;

Question 13

Succession - competition

Answer 13

1. Pioneer species increases then decreases;
2. Principle of a species changing the conditions / a species makes the conditions;
3. New/named species better competitor / pioneer species outcompeted