3.4.4 Genetic diversity and adaptation Flashcards
What is genetic diversity?
The number of different alleles of genes in a population.
How does genetic diversity enable natural selection?
Provides variation allowing differential reproductive success.
State the first principle of natural selection.
Random mutation can result in new alleles of a gene.
Why are many mutations harmful?
They may reduce the organism’s chance of survival and reproduction.
In what circumstance might a new allele benefit its possessor?
In certain environments the new allele might increase survival or reproductive success.
What happens to advantageous alleles in future generations?
The advantageous allele is inherited by members of the next generation.
Over many generations what happens to the frequency of a beneficial allele?
The beneficial allele increases in frequency in the population.
What is directional selection?
Selection that favours individuals with an extreme phenotype.
Give an example of directional selection.
Antibiotic resistance in bacteria.
What is stabilising selection?
Selection that favours individuals with a phenotype closest to the mean.
Give an example of stabilising selection.
Human birth weights.
What does natural selection result in?
Species better adapted to their environment.
Name three types of adaptations resulting from natural selection.
Anatomical physiological behavioural.
Define genetic diversity
the number of different alleles of genes in a population.
Describe how a student made a 1 in 10 dilution and then used this to make a 1 in 1000 dilution of the original liquid culture of bacteria.
- 1 part bacterial culture to 9 parts water
- Mix
- Repeat using 9 parts fresh (sterile) liquid and 1 part of 10–1 and 10–2 dilutions to make 10–3 dilution;
Why would a 1 in 10 dilution not be appropriate to use to determine cell numbers?
- Count unlikely to be accurate / repeatable / reproducible / reliable
- Because too many cells; Or cells will be overlapping
Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria.
- Some bacteria have alleles for resistance
- Exposure to antibiotics creates a selection pressure
- Antibiotics kill bacteria that are not resistant
- Resistance strains survive and reproduce
Describe the aseptic techniques used to transfer bacterial culture onto an agar plate.
- Use sterile pipette/syringe
- Flame top of the bottle
- Lift lid of agar plate at an angle
- Use sterile spreader
- Place pipette/spreader onto disinfectant
Describe the principles of natural selection in the evolution of a population.
Random mutation can result in new alleles of a genes.
Many mutations are harmful but, in certain environments, the new allele of a gene might benefit its possessor, leading to increased reproductive success.
The advantageous allele is inherited by members of the next generation.
over many generations, the new allele increases in frequency in the population
