Natural Selection Basics
This process explains how individuals with favorable traits survive and reproduce more than others.
What is natural selection?
This type of selection favors one extreme phenotype.
What is directional selection?
This evidence compares DNA or amino acid sequences to determine relatedness.
What is molecular (biochemical) evidence?
Random changes in DNA that introduce new alleles are called this.
What are mutations?
The formation of new species is called this.
What is speciation?
Natural selection acts on these traits, even though genes are what get passed on.
What are phenotypes? (physical traits)
This type of selection favors both extreme phenotypes and selects against the average.
What is disruptive selection?
Similar structures with different functions that come from a common ancestor are called these.
What are homologous structures?
The movement of alleles between populations is called this.
What is gene flow?
This must occur for speciation to happen.
What is reproductive isolation?
Evolution does NOT occur in individuals because evolution is defined as a change in this over time.
What are allele frequencies in a population? (trait frequency, commonality)
Gray bark trees dominate an environment. Which type of selection is most likely acting on moth color?
What is stabilizing selection?
This evidence includes transitional fossils showing traits of both ancestral and modern species.
What is the fossil record?
Why does gene flow increase genetic diversity within a population?
It introduces new alleles into the gene pool.
Physical separation of populations that leads to genetic divergence is called this.
What is geographic isolation?
This type of selection favors the average individual and selects against extreme traits.
What is stabilizing selection?
An environment shifts from light to dark due to pollution, causing moths to become mostly dark-colored.
What is directional selection?
Similarities in early embryos suggest this evolutionary concept.
What is shared ancestry? (common ancestors)
This evolutionary mechanism has a stronger effect in small populations due to random chance.
What is genetic drift?
Different mating calls or courtship behaviors preventing interbreeding is known as this.
What is behavioral isolation?
Explain why natural selection can act on individuals, but evolution is seen in populations.
Natural selection affects individual survival and reproduction, but evolution is the change in allele frequencies across generations in a population.
In an environment with both light and dark trees, which moth colors are favored and why?
White and black moths are favored because they blend into different backgrounds, indicating disruptive selection.
Bat wings and butterfly wings are examples of these structures.
What are analogous structures?
Why does the founder effect often cause unusual traits to become common?
Because a small founding population may randomly carry rare alleles that increase in frequency.
Why can populations living in the same area still become separate species?
Because reproductive barriers (behavioral, temporal, ecological) can reduce gene flow, leading to sympatric speciation.