Unit 7 Natural Selection

What factors would increase the frequency of a genotype in a population over time?

• Increased reproduction rates in a population

• Selective pressures that make the trait favorable

• Genetic drift

• Mutations in the population

Why would the presence of a particular genotype or phenotype decrease in a population over time?

• Due to increased competition

• Reproductive isolation

• Changes in the environment that now make the trait less favorable

• Gene flow

What are selection pressures?

• Conditions that prevent a population from evolving

• Organisms that shape and influence the ecosystem

• Random changes in allele frequencies in a population

• Any changes in biotic or abiotic factors that influence survivability

What is artificial selection?

• When humans selectively breed organisms together to select for traits most desirable to us

• When a new species has formed

• When new organisms migrate into an area and introduce new genes

• When organisms are separated from other members of their population due to new geographic barriers

What is the founder effect?

• When survivors of a natural disaster repopulate the environment

• When a small population breaks off of an existing population

• Changes in the genetic makeup of a population over time

• The migration of organisms between two similar populations

How does genetic drift usually affect a population?

• Usually it increases the size of a population

• Usually it increases the selective pressures on a population

• Usually it decreases the genetic variation of the population

• Usually it introduces new genes into a population

What are the two types of genetic drift commonly seen?

• Temporal isolation and hybrid sterility

• Disruptive selection and convergent evolution

• Founder effect and bottleneck effect

• Gene flow and artificial selection

According to this cladogram, which animal has the closest common ancestor to a crocodile?

• Mammals

• Lizards and Snakes

• Turtles

• Birds

Which animal is the out-group?

• Mammals

• Turtles

• Crocodiles

• Birds

What is the bottleneck effect?

• When survivors of a natural disaster repopulate the area

• When selective pressures change and new traits become the most fit for an area.

• When members of one population migrate to another population

• When new organisms migrate to an area and start a new population