Exam Review Unit 6 Flashcards
Natural Selection
Mechanism for how evolution occurs; “survival of the fittest;” some organisms will survive and reproduce better than others, causing changes in the population over time by acting on traits that are heritable.
Four principles of Natural Selection
- Overproduction of Offspring
- Variation
- Adaptation
- Descent with Modification
Overproduction of Offspring
lots of offspring and limited resources 🡪 competition
Variation
differences in physical traits of organisms (caused by mutations, genetic recombination, and gene flow)
Adaptation
some organisms have traits that allow them to survive and reproduce better than other organisms
Descent with Modification
over time, selection will favor traits that increase survival and reproduction so those traits should become more common over time 🡪 a change in gene frequency
One of the major elements of natural selection is that all species have genetic
A. digression.
B. melanism.
C. stability.
D. variation.
Variation
One of the biggest ways that a species evolves is because some organisms with some traits survive and reproduce better than others. This process is known as
A. natural selection.
B. convergent evolution.
C. coevolution.
D. sexual selection.
natural selection
An adaptation is
A. any trait an organism possesses.
B. how an organism evolves during its own lifetime.
C. a gene an organism has.
D. a trait that helps an organism fit its environment.
A trait that helps an organism fit its environment.
A population of bacteria is treated with hand sanitizer. Because of genetic variation in the population, what is a possible outcome?
A. The population will grow quickly.
B. All of the bacteria are already resistant.
C. They will get better at obtaining a food source.
D. Some may be resistant and survive.
Some may be resistant and survive.
Genes for traits that help an organism be more successful reproductively can be expected to cause it to
A. evolve into a new species.
B. become more common in the future.
C. cause the extinction of the species.
D. eventually be eliminated by natural selection.
Become more common in the future
A botanist is investigating a population of plants whose petal color is either purple or brown. She finds 170 plants that are homozygous brown, 340 plants that are homozygous purple, and 20 plants whose petals are heterozygous. Brown is dominant to purple. Is this population in Hardy- Weinberg equilibrium?
- If the population WAS in HWE, what would the frequency of the homozygous recessive genotype be?
- If the population WAS in HWE, what would the frequency of the heterozygous genotype be?
- If the population WAS in HWE, what would the frequency of the homozygous dominant genotype be?
- Compare answers a-c to f-h. Is this population in HWE?
- If not, which trait is favored? Also, what mode of selection is occurring?
- If the population WAS in HWE, what would the frequency of the homozygous recessive genotype be?
- 0.44
If the population WAS in HWE, what would the frequency of the heterozygous genotype be?
- 0.45
If the population WAS in HWE, what would the frequency of the homozygous dominant genotype be?
- 0.12
Compare answers a-c to f-h. Is this population in HWE?
- No
If not, which trait is favored? Also, what mode of selection is occurring?
- Two extremes are favored therefore disruptive selection is occurring
Homologous Structures
- Result from divergent evolution
- Similar ancestry, therefore similar structure
- Different environment, therefore evolved different use
- Ex. Human arm and dog leg
Analogous Structure
- Result from convergent evolution
- Different ancestry, therefore different structure
- Similar environment, therefore evolved similar use
- Ex. Bat wing and butterfly wing
Vestigial Structure
- Result from divergent evolution
- Structure not useful to organism but is leftover from an ancestor the organism evolved from
- Useful for ancestor
- Ex. Ostrich wings; leg bones in whales
