Selection and evolution Flashcards
Explain what is meant by stabilising selection.
Individuals in a population with intermediate phenotypes are more likely to survive and reproduce.
Individuals in a population with extreme phenotypes will die.
Assuming there is no change in environment.
Explain what is meant by genetic drift.
It is a random change of allele frequency. It has a larger influence in smaller population.
What are the five conditions for Hardy-Weinberg principle?
- Large population
- Random mating
- No mutation
- No gene migration
- No natural selection
Give two disadvantages of selective breeding.
Inbreeding depression.
Loss of hybrid vigour.
Outline the steps involved in the introduction of disease resistance to a certain plant species.
Expose plants to disease.
Select disease resistance plants that are not affected by disease.
Breed selected plants.
Select offsprings with disease resistance and breed together.
Repeat for many generations.
Outline how bacteria evolve to become resistant to antibiotics.
It happens due to natural selection.
Antibiotics act as selection pressure.
Antibiotics resistance gene occurs due to random mutation.
When exposed to antibiotics, bacteria with mutation will survive and reproduce.
They will pass down the antibiotic resistance gene.
They can also pass on the gene to another bacteria by horizontal transmission.
Explain what is meant by continuous variation and how it can be caused.
Phenotype has a range of values.
Phenotype is not discrete.
Phenotype is controlled by many genes.
Phenotype affected by environmental factors.
Explain why natural selection occurs in population.
Genetic variation occurs due to mutations and random fertilisation.
Selection favour acts in the favour of certain genotypes.
Individuals with advantageous adaptations will survive and reproduce.
Advantageous alleles are passed on.
Frequency of advantages alleles increases.
