Population Genetics
Introduced| English |
|---|
| population/ˌpɒpjʊˈleɪʃn/ |
| gene pool/dʒiːn puːl/ |
| allele frequency/əˈliːl ˈfriːkwənsi/ |
Evolution seen in a population
- A single organism cannot evolve — it lives and dies with the genes it was born with.
- Evolution only shows up when you look at a whole population over time.
- To study it, biologists track the mix of alleles in that population.
- This is the field of population genetics.
The gene pool
- A population 种群 is a group of the same species living together.
- All the alleles in that population make up its gene pool 基因库.
- The gene pool is like a giant shared box of genetic variety.
- Every new offspring is dealt its genes from this pool.
A gene pool is…
A gene pool is the whole collection of alleles in a population at a given time.
Allele frequency
- Allele frequency 等位基因频率 is how common each allele is in the gene pool.
- If an allele is in 70% of the copies, its frequency is 0.7.
- Frequencies show which versions of a gene dominate the population.
- Tracking them lets us measure evolution precisely.
Evolution as changing allele frequency
Step through how selection changes the mix of alleles in a gene pool over generations.
Allele frequency describes…
Allele frequency is the proportion of a gene pool made up of one particular allele.
Evolution = changing frequencies
- When an allele becomes more or less common, the gene pool has changed.
- Evolution, at this level, is a change in allele frequency over generations.
- Selection, migration, mutation, and chance can all shift the frequencies.
- Add up these shifts over time, and a population evolves.
At the population level, evolution is a change in allele ____ over generations.
Evolution is defined as a change in allele frequency in a population over time.
Natural selection, migration, and mutation can all change allele frequencies.
Selection, migration, mutation, and chance (genetic drift) all shift allele frequencies.
Select all true statements about population genetics.
Individuals do not evolve; populations do, as allele frequencies change. The other three are correct.
Individuals do not evolve — populations do. Your own alleles are fixed for life. Evolution is the change in allele frequency across a whole population over generations, not a change inside one organism.
Counting a colour allele:
- Suppose a beetle population is 40% dark alleles, 60% light.
- Birds eat the light beetles more easily, so fewer light alleles get passed on.
- Next generation the dark allele frequency rises to 55% — the population has evolved.
Population genetics studies the gene pool — all the alleles in a population. Allele frequency measures how common each allele is. Evolution at this level is a change in allele frequency over generations, driven by selection, migration, mutation, and chance. Populations evolve; individuals do not.