Types of evolution Flashcards
(15 cards)
Why is it important to study evolution?
To understand aspects of the natural world, including climate change, pathogen resistance, emerging diseases, and mass extinction
The ‘6th mass extinction’ refers to the current biodiversity crisis where 2,000,000 species are threatened with extinction.
What is mutation in the context of evolution?
Changes in the DNA sequence of a cell’s genome that can increase genetic variation/diversity
Mutations can occur spontaneously or be induced by external factors.
What are some forms of mutation?
- Substitution
- Indels
- Slippage
- Gene duplication
- Deletion
- Transposable elements
What is the general effect of mutations on fitness?
Usually reduces the fitness of an organism
How do mutations contribute to evolution?
They provide the raw material needed for new genes to evolve, often from pre-existing genes that share common ancestors
What is recombination and its role in evolution?
Variation is ‘shuffled’ around, generating new variation very quickly
It occurs within or between genes and is often associated with sexual reproduction.
What is the two-fold cost of sex?
Only one of the two sexes can bear young, and any individual reproducing sexually can only pass on 50% of its genes
What is gene flow?
The transfer/exchange of genes between species and across populations, generating new variation quickly
It can occur through migration or establishment in new habitats.
What is natural selection?
A process that actively ‘shapes’ variation at a genetic level and increases fitness
It is often summarized as ‘survival of the fittest’.
What is fitness in evolutionary terms?
An organism’s ability to survive and reproduce, determining its genetic contribution to the next generation
What is sexual selection?
A mode of natural selection where members of one biological sex choose mates or compete for access to mates
It includes intersexual and intrasexual selection.
What is genetic drift?
A change in the frequency of an existing allele in a population, usually reducing genetic variation
It is more pronounced in small populations.
What happens during a population bottleneck?
Genetic drift may eliminate some alleles from a population due to chance alone
What occurs when selective forces are weak or absent?
Allele frequencies are equally likely to drift up or down at each generation
What is the outcome of genetic drift?
Drift stops when an allele becomes fixed, either disappearing or completely replacing other alleles
