4b diversity and selection Flashcards
What are alleles?
These code for different versions of the same characteristic
What is genetic diversity?
The number of different alleles of genes in a species or population
How is genetic diversity in a population increased?
Mutations forming new advantageous alleles
Different alleles being introduced into a pop when individuals from another pop migrate and reproduce = gene flow
What is a genetic bottleneck?
An event that causes a big reduction in a population which reduces the number of different alleles so reducing diversity
What is the consequence of a genetic bottleneck?
The survivors reproducing and a larger pop being created from fewer individuals
What is the founder effect?
When just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool
What causes the founder effect?
Migration leading to geographical separation
New colony is separated from the original population for another reason
What is natural selection?
When an allele codes for a characteristic that increases the chances of an organism surviving, its frequency within a pop increases
What are the steps to natural selection?
- Individuals that have an allele that increases chance of survival, reproduce and pass on their genes
- The next generation have a greater proportion inheriting the allele
- They survive, reproduce and pass on
- Frequency of beneficial allele in the population increases from generation to generation
- This leads to evolution as the advantageous alleles become more common in the pop
What are the 3 types of adaptations?
- Behavourial adaptations eg the way an organisms acts
- Physiological adaptaions eg processes inside the body eg hibernation
- Anatomical eg structural features of an organisms body that increases chance of survival eg blubber
What are the types of selection and examples ?
Directional - individuals with alleles for certain characteristics of an extreme type are more likely to reproduce and survive eg antibiotioc resistance
Stabilising - Individuals with alleles in the middle of the range will survive and reproduce, this occurs when environment isnt changing eg birthweight
What is the name of a chromosome mutation?
Chromosome non disjunction - failure of chromosomes to separate properly
What is the difference between haploid and diploid?
Haploid cells have half the number of chromosomes as they only contain one copy of each chromosome in a homologous pair
-> in humans this is 23 (gametes)
Diploid cells have the full set as each cell contains two of each chromosome
-> in humans this is 46
What is independant segregation?
When the homologous pair have been seperated, it is a random process for which chromosome ends up in which daughter cell
What is crossing over?
The chromatids cross over each other and bits of chromatids swap over (the chromosomes contain the same genes but a different combination of alleles)
One chromosomes from each homologous pair ends up in each cell
The four daughter cells will contain chromatids with different alleles