Genetic Diversity and Natural Selection Flashcards
What is genetic diversity?
The number of alleles in a species or population. It also allows natural selection to occur
Why is a higher genetic diversity in a species more favourable?
It means that the species is able to adapt to changing environmental conditions as there’s a higher probability that some individuals will have better alleles suited to the new environment
How is genetic diversity increased in a population?
➣Mutations that form new alleles
➣Different alleles being introduced into a population when individuals from another population migrate into them and reproduce, known as gene flow.
How do genetic bottlenecks reduce genetic diversity?`
➣It’s an event that causes a big reduction in a population which reduces the number of different alleles in the gene pool and so reduces genetic diversity
➣The survivors reproduce and a larger population is created from a few individuals, however the genetic diversity is restricted to very few alleles
What is the founder effect?
➣A type of genetic bottleneck that occurs when just a few organisms from a population start a new colony. There are only a small number of different alleles in the initial gene pool which aren’t representative of the original population. The new population will thus show less variance.
What is selective breeding?
Breeding individuals with desired characteristics to produce the next generation
What are the ethics of selective breeding in domesticated animals?
➣Main issue is inbreeding, which reduces the variety of alleles and genetic diversity so less able to adapt
➣Inbreeding increases the risk of harmful genetic conditions and similar immune systems so a single pathogen could wipe out a whole population
➣Desired characteristics could cause the animal harm, udder size in cows
➣Irreversible loss of alleles that may be of benefit
What are the advantages of selective breeding?
➣More efficient food production
➣Lower prices
➣It can improve resistance to disease
What is natural selection? What is differential reproductive success?
Organisms with a beneficial allele survive and breed, passing on the allele whilst those without the allele don’t- differential reproductive success. The frequency of the beneficial allele increases in the gene pool from generation to generation as selection for the organism continues.
What are behavioural adaptations?
Ways an organism acts that increases its chance in survival and reproduction, e.g. possums playing dead to escape attack from a predator
What are physiological adaptations?
Processes inside an organism’s body that increases its chance of survival such as brown bears hibernating over winter.
What are anatomical adaptations?
Structural features of an organism’s body that increases its chance in survival, e.g. whales have a thick layer of blubber which helps it to keep warm in the cold sea.
What is stabilising selection?
When the environment isn’t changing and so individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce, reducing the range of possible characteristics.
What is an example of stabilising selection?
➣Humans have a range of birth weights
➣Very small babies are less likely to survive, partly because they find it hard to maintain their body temperature.
➣Giving birth to large babies can be difficult, so large babies are less likely to survive too.
➣Conditions are most favourable for medium-sized babies, so the weight shifts to the middle.
What is directional selection?
Where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.
