Week 2 - Population genetics and evolution of genomes Flashcards
What is the difference between macroevolution and microevolution?
Microevolution refers to change under species level, described as changes in allele frequencies- natural selection. Where as, macroevolution refers to change that occurs above species level (e.g. phylogenies)
What are Darwin’s 6 observations?
- There is variation amongst traits in a population
- Traits are inherited by offspring
- More offspring is produced than an environment can support
- Inherited variations affect survival and reproduction
- Individuals who’s inherited traits increase their survival normally leave more offspring
- Over generations this leads to an accumulation of favourable characteristics
What is the definition of a mutation?
Changes in the nucleotide sequence of DNA, cause new genes and alleles to rise
What is a point mutation?
The change in one base in a gene, significantly impacts phenotype.
Can be silent, nonsense, missense
Which 3 mechanisms act on the variability generated by mutations?
Natural selection
Genetic drift
Gene flow (migration)
Which of the 3 mechanisms consistently causes adaptive evolution?
Natural selection
What is meant by adaptive evolution?
It occurs as the match between a species and its environment increases
What is meant by relative fitness?
It is the contribution an individual makes to the gene pool of the next generation, relative to other individuals
Which type of selection favours birds with larger beaks ?
Directional - favours individuals at [one end] of the [phenotypic range].
Which type of selection favours small and large beaks in an environment with large hard seeds and small delicate ones.
Disruptive selection- favours individuals at both extremes of the {phenotypic range}
Which type of selection favours babies with an average birth weight?
Stabilizing selection - favours intermediate variants, acting [against extreme phenotypes]
What is an example of artificial selection?
Humans selecting certain dogs and breeding them
What is genetic drift ?
The change in the frequency of alleles due to random sampling of organisms.
Why is genetic drift non-adaptive?
Because it occurs randomly, so the phenotypes do not matter.
It tends to reduce genetic variation through losses of alleles.
What are the 2 types of genetic drift ?
Bottleneck effect (time)
Founder effect (space)
What is meant by The Bottleneck Effect?
When a reduction in population size occurs due to a non-selective (random) change in the environment- like a natural disaster.
Reducing the size of the gene pool
What is meant by The Founder Effect?
When individuals become isolated from a larger population - e.g. migration
Allele frequencies may be different in the small founder population compared to the parent population.
What is meant by Gene flow and how does it influence variation and adaption of a population?
The movement of alleles among populations (e.g. migration).
It can reduce variation by homogenizing the genetic make up of different populations.
It can also increase the spread of alleles for resistance - increasing the adaptability of a population.
What is meant by the term “Ring of species” ?
The gene flow between different species/populations that usually can’t reproduce due to [geographical isolation].
What does introgression mean?
The insertion of an allele specific to one species in another one, produced by “Ring of species” .
What is the definition of a species?
A group of organisms [capable] of [reproducing fertile offspring], typically using [sexual reproduction].
What is a population?
A [localized] group of individuals [capable] of interbreeding and [producing fertile offspring].
What is meant by the term population genetics?
How populations change genetically over time
What is a gene pool?
The [total aggregate of genes in a population] at any one time.
