4.4 Genetic Diversity And Adaptation

Question 1

What is genetic diversity?

Answer 1

• number of different alleles of genes in a population

Question 2

What are alleles and how do they arise?

Answer 2

• variations of a particular gene (same locus) -> different DNA base sequence
• arise by mutation

Question 3

What is a population?

Answer 3

• a group of organisms of the same species in a particular space at a particular time
• that can potentially interbreed to produced fertile offspring

Question 4

Explain the importance of genetic diversity

Answer 4

• enables natural selection to occur
• as in certain behaviours, a new allele of a gene might benefit its possessor
• by resulting in a change in the polypeptide coded for that positively changes its properties
• giving possessor a selective advantage (increased chances of survival and reproductive success)

Question 5

What is evolution?

Answer 5

• change in allele fréquence over many generations in a population
• occurring through the process of natural selection

Question 6

Explain the principles of natural selection in the evolution of populations

Answer 6

1. Mutation
   - random gene mutations can result in new alleles of a gene
2. Advantage
   - in certain environments, the new allele might benefit its possessor -> organism has a selective advantage
3. Reproduction
   - possessors are more likely to survive and have increased reproductive success
4. Inheritance
   - advantageous allele is inherited by members of the next generation (offspring)
5. Allele frequency
   - over many generations, allele increases in frequency in the population

Question 7

Describe 3 types of adaptations

Answer 7

Natural selection results in species that are better adapted to their environment
- anatomical - structural/physical features that increase chance of survival
- physiological - processes / chemical reactions that increase chance of survival
- behavioural - ways in which an organism acts that increase chance of survival

Question 8

Explain directional selection

Answer 8

Example - antibiotic resistance in bacteria
Key feature - organisms with an extreme variation of a trait has selective advantage
Environment - often a change
Effect on population over many generations:
- increased frequency of organisms with / alleles for extreme trait
- normal distribution curve shifts towards extreme trait

Question 9

Explain stabilising selection

Answer 9

Example - human birth weight
Key feature - organisms with an average / model variation of a trait has selective advantage
Environment - usually stable
Effect on population over many generations:
- increased frequency of organisms with / alleles for average trait
- normal distribution curve similar, less variation around the mean