Evidence for Natural Selection
How do fossils provide evidence for evolution?
They show gradual changes in species over time, including transitional forms.
What is genetic drift?
A change in allele frequencies due to random chance, not selection
What happens in directional selection?
One extreme trait is favored (ex. giraffes with longer necks).
What does the Hardy-Weinberg principle state?
Allele frequencies stay constant unless evolutionary forces act on them
What enxyme is used to digest lactose?
Lactase
What do similar embryonic structures in different species suggest?
They share a common ancestor.
What type of population is most affected by genetic drift?
Small Populations
What happens in stabilizing selection?
The average trait is favored (ex. human birth weight).
What is the Hardy-Weinberg allele frequency equation?
p+q=1
What happenes to most people after infancy in terms of lactose digestion?
They stop producing lactase and become lactose intolerant
What are homologous structures?
Similar structures in different species that evolved from a common ancestor but have different functions.
What is the bottleneck effect?
A drastic reduction in population size causes a shift in allele frequencies
What happens in disruptive selection?
Both extremes are favored over the average (ex. large and small bird beaks).
What is the Hardy Weinberg genotype frequency equation?
p^2 + 2pq + q^2 =1
Why did lactose persistence evolve?
In populations with dairy farming, natural selection favored individuals who could digest milk.
What are vestigial structures?
Body parts that have lost their original function but remain as evolutionary leftovers (e.g., human appendix, whale pelvis).
What is the founder effect?
A small group starts a new population with different allele frequencies from the original?
Which type of selection leads to a more uniform population?
Stabalizing Selection
If q^2 = 0.16, what is q?
q = 0.4
What regions have the highest lactose persistence?
Northern Europe, East Africa, Middle East
How does molecular evidence support evolution?
DNA and protein similarities show how closely related species are.
How can genetic drift lead to speciation?
Random allele changes can make 2 groups so different that they can no longer interbreed.
Which type of selection can lead to speciation?
Disruptive selection, because the two extreme groups may become separate species.
What five conditions must be met for Hardy-Weinberg equilibrium?
No mutation, no natural selection, random mating, no migration, and a large population
What type of genetic change led to lactose persistence?
Mutation in the LCT gene that allows lactase production into adulthood.