Genetic diversity and adaptation Flashcards
What is genetic diversity?
The number of different alleles of all the genes in a population.
What is a gene pool?
All the alleles in a population
Why is genetic diversity important for natural selection?
Having a variety of alleles for a gene in the population gives a variety of phenotypes. Some of these may have a selective advantage or disadvantage over others. In this way natural selection can occur.
What is the result of natural selection in evolution of populations?
Over many generations allele frequencies will change, for example a new advantageous allele will increase in frequency.
Describe how natural selection is a process in the evolution of populations.
Random mutations can result in new alleles of a gene. Many mutations are harmful but, in certain environments the new allele of a gene might be advantageous to the organism. This will lead to increased survival and reproductive success over other members of the population. The advantageous allele is more frequently inherited by members of the next generation. Over many generations the frequency of the new advantageous allele increases in the population.
What is directional selection?
When one extreme phenotype is selected for. The normal distribution curve shifts to either the left or the right.
Describe directional selection using antibiotic resistance in bacteria as an example.
A mutation; Results in bacteria with allele for resistance to antibiotic; This cell survives and passes the allele for resistance to offspring; through binary fission; There is an increase in frequency of the allele for antibiotic resistance in the population;
What is stabilising selection?
When the extremes of a phenotype are selected against. The normal distribution curve narrows.
Describe stabilising selection using human birth weight as an example.
Babies born with extreme mass (both high and low) are least likely to survive to reproduce and so less likely to pass on their alleles for extreme mass at birth; Alleles for extreme mass at birth decrease in frequency in the population;
Why is natural selection an advantage to a species?
It results in the species being better adapted to their environment, so more organisms will survive and breed.
What adaptations may natural selection confer on an organism?
Adaptations may be anatomical (smaller ears, thicker fur,etc.), physiological (production of antifreeze proteins, higher rate of metabolism, etc.) or behavioural (migration or nocturnal/diurnal organisms).
How can the dominant/recessive nature of an allele impact natural selection.
The dominant allele is always expressed in the phenotype, so the frequency would more rapidly increase than if the allele was recessive.
Why is a logarithmic scale used when using data of bacterial population increases.
To account for large difference between numbers. So they can be plotted on the same graph axis.
Describe the aseptic techniques that should be used when culturing bacteria to investigate their resistance to antibiotics.
- Flame the neck of the culture bottle as soon as you open it and again before closing the lid.
- Use a sterile pipette to transfer the culture onto agar and place the pipette into disinfectant after use.
- Only lift the lid of the agar plate a little and for a short time period-close immediately after transferring the culture.
- Use a sterile spreader then place the spreader in disinfectant after use.
