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 produce fertile offspring)

Question 4

explain the importance of genetic diversity

Answer 4

● enables natural selection to occur
● as in certain environments, a new allele of a gene might benefit its possessor
● by resulting in a change in the polypeptide (protein) 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 frequency (how common an allele is) 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 [named] new alleles of a gene
2. Advantage
   - in certain [named] environments, the new allele might benefit its possessor [explain why] → 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, [named] allele increases in frequency in the population

Question 7

describe 3 types of adaptations

Answer 7

● 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, with examples

Answer 8

●eg=antibiotic resistance in bacteria
●key feature = organisms with an extreme variation of a trait eg. bacteria with high level of resistance to a particular antibiotic
●environment = often a change, eg. antibiotic introduced
●effect on population =
-increased frequency of organisms with / alleles for extreme trait
-normal distribution curve shifts towards extreme trait

Question 9

explain stabilising selection, with examples

Answer 9

●eg = human birth weight
●key feature = organisms with an average / modal variation of a trait eg. babies with an average weight
●environment = usually stable
●effect on population=
- increased frequency of organisms with / alleles for average trait
- normal distribution curve similar, less variation around the mean