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Evolution
of Populations
| Question | Answer |
|---|---|
| What is a genotype? | the particular combination of alleles it carries |
| Does natural selection act as a genotype or a phenotype? | phenotype |
| What does it mean for natural selection to act on phenotype? | natural selection never acts directly on genes, because it is an entire organism that survives and reproduces, not a single gene |
| What is a gene pool? | the combination of all the genes (including alleles) present in a reproducing population or species |
| What is allele frequency? | the number of times an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene |
| What is evolution, in genetic terms? | a change of frequency in a population over time |
| What are three sources of genetic variation? | mutation, genetic recombination during sexual reproduction, and lateral gene transfer |
| What is a mutation? | any change in the genetic material of a cell; can involve changes in individual genes or larger pieces of chromosomes |
| What are most heritable differences due to? | genetic recombination |
| What is lateral gene transfer? | the passing of genes from one organism to another organism that is not its offspring; this process is important in the evolution of antibiotic resistance in bacteria |
| What does the number of phenotypes produced for a trait depend on? | how many genes control the trait |
| How many genes is a single-gene controlled by? | one |
| How many genes is a polygenic controlled by? | two or more |
| What is evolutionary fitness? | the success in passing genes to the next generation |
| What can natural selection on single-gene traits lead to? | changes in allele frequencies |
| What can natural selection on polygenic traits lead to? | it can affect the relative fitness of phenotypes and thereby produce one of three types of selection: directional selection, stabilizing selection, or disruptive selection |
| What is directional selection? | when individuals at one of the statistical bell curve have higher fitness than individuals in the middle or at the other end |
| What is stabilizing selection? | when individuals near the center of the curve have higher fitness than individuals at either end, making the bell curve narrow |
| What is disruptive selection? | when individuals at the outer ends of the curve have higher fitness than individuals near the middle of the curve |
| What is genetic drift? | when a random change in allele frequency becomes more or less common |
| What is bottleneck effect? | a change in allele frequency following a dramatic reduction in size of a population |
| What is founder effect? | a change in allele frequency as a result of the migration of a small subgroup of a population |
| What is genetic equilibrium? | when allele frequencies in a gene pool do not change and the population is not evolving |
| What does the Hardy-Weinberg principle state? | that allele frequencies in a population should remain constant unless one or more factors cause those frequencies to change |
| What are the five conditions that can disturb genetic equilibrium and cause evolution to occur(predicted by HWP)? | nonrandom mating, small population size, immigration or emigration, mutations, or natural selection |
| What is sexual selection? | when individuals choose mates based on heritable traits |
| What is considered a species? | a population or group of populations whose members can interbreed and produce fertile offspring |
| What is speciation? | the formation of a new species |
| When does reproductive isolation occur? | when two populations no longer interbreed; when populations become reproductively isolated, they can evolve into two separate species |
| How does reproductive isolation develop? | a variety of ways, including behavorial isolation, geographic isolation, and temporal isolation |
| When does behavioral isolation occur? | when two populations that are capable of interbreeding develop differences in courtship rituals |
| When does geographic isolation occur? | when two populations are separated by geographic barriers |
| When does temporal isolation occur? | when two or more species reproduce at different times |
| What do researchers use molecular clocks and compare stretches of DNA to do? | mark the passage of evolutionary time |
| What does a molecular clock do? | uses mutation rates in DNA to estimate the time that two species have been evolving independently |
Created by:
alov9636
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