Microevolution
What is microevolution?
A change in allele frequencies within a population over generations.
What is natural selection?
The process where individuals with advantageous heritable traits have greater survival and reproductive success, causing those alleles to become more common.
What is macroevolution?
Large-scale evolutionary change occurring over long periods, including speciation and diversification.
What is speciation?
The evolutionary process through which new species form.
What does a cladogram show?
The evolutionary relationships and common ancestry between organisms.
What process introduces new alleles into a population through changes in DNA?
Mutations
What type of selection favours the intermediate phenotype?
Stabilising
What type of evolution occurs when related species become increasingly different?
Divergent
What type of speciation occurs when a geographic barrier separates populations?
Allopatric
On a cladogram, what does a node represent?
A common ancestor where evolutionary lineages diverged.
What process changes allele frequencies when individuals move between populations and reproduce?
Gene flow
What type of selection favours individuals at both extremes of a phenotype?
Disruptive
Sharks and dolphins independently evolved streamlined bodies. What type of evolution is this?
Convergent
Two plant populations live in the same area but flower at different times. What type of isolation is occurring?
Sympatric
Species A and B have 2 DNA differences, while A and C have 15. Which species is most closely related to A?
Species B
A storm randomly kills most individuals in a population. The surviving population has different allele frequencies. Name the process and specific effect.
Genetic drift through the bottleneck effect.
A pesticide kills most insects, but insects carrying allele R survive and reproduce. Is allele R experiencing positive or negative selection?
Positive
Two closely related species independently develop similar adaptations in similar environments. What evolutionary pattern does this represent?
Parallel
Two populations live in neighbouring habitats and experience different selection pressures, with limited gene flow between them. What type of speciation could result?
Parapatric
Why are conserved DNA sequences useful for determining evolutionary relationships?
Conserved sequences change relatively slowly over time. Closely related species generally have fewer differences in these sequences, allowing scientists to infer common ancestry and evolutionary relationships.
A population contains 40 AA, 50 Aa and 10 aa individuals. What is the frequency of allele A?
0.65
After a drought, the frequency of allele B increases from 0.25 to 0.72. Explain how natural selection could cause this change.
The drought acted as a selection pressure. If allele B produced an advantageous phenotype, individuals carrying B were more likely to survive and reproduce. They passed B to their offspring, causing its frequency to increase over generations.
Explain how microevolutionary changes can eventually produce macroevolutionary change.
Mutation, natural selection, genetic drift, and gene flow cause changes in allele frequencies within populations. When populations become isolated, differences can accumulate over many generations. Eventually, reproductive isolation and speciation may occur. Repeated speciation and evolutionary change over long periods produce macroevolutionary patterns.
Explain how reproductive isolation can eventually result in the formation of a new species.
Reproductive isolation reduces or prevents gene flow between populations. Mutation, natural selection and genetic drift then cause the populations to accumulate different alleles. Over many generations, they may become genetically different enough that they can no longer successfully interbreed, resulting in speciation.
Explain how molecular sequence data can be used to estimate when two species diverged from a common ancestor.
Scientists compare homologous DNA sequences between species. Mutations accumulate over generations, so species that diverged longer ago generally have more sequence differences. If the mutation rate is known or estimated, these differences can be used as a molecular clock to estimate when the species diverged from their common ancestor.