Study Guide: Exam 1 Ch. 13 Flashcards
What is natural selection?
Natural selection is a mechanism of evolution. The theory is based around the fact that organisms with favorable traits, for their environment, are more likely to survive long enough to reproduce and pass down those favorable traits.
What is evolution?
Evolution is the change in
genetic composition of
populations over time.
A cockroach has a diploid genome of 1.8 billion base pairs. Assume that there are about 300,000
individuals in the population and that the mutation rate is one per 150 million base pairs. On average,
how many new mutations will occur in an individual cockroach?
12 mutations per 150 million base pairs
What is the maximum number of alleles that a given human adult (with 23 pairs of chromosomes)
can have at any particular genetic locus?
2 alleles
What is an adaptation? Give examples.
Adaptation a favored trait that evolves through natural selection. Some types of adaptation are physical and behavioral adaptations.
Define: Genetic drift. Gene flow. Reproductive isolation.
Genetic drift - random changes in allele frequencies from one generation to the next
Gene flow - the result of the migration of individuals or movement of gametes (e.g., pollen) between populations
Reproductive isolation - two groups of organisms can no longer exchange genes
What was Darwin’s explanation for the evolution of bright colors and other apparently useless (and
potentially deleterious) but conspicuous characters in males of many species?
Darwin believes that sexual selection is the reason for the presence of useless and conspicuous characters in the males of many species.
If p is the frequency of allele a, and q is the frequency of allele A, then p+q=____.
1
Assuming that there are only two alleles at a given locus, if the frequency of one allele is 0.6, what
is the frequency of the other allele?
0.4, 1 - 0.6 = 0.4
What are the assumptions of the Hardy-Weinberg Equilibrium?
There must be random mating and infinite population size, but no mutation, no gene flow, and no selection of genotypes (natural selection)
If a population is at Hardy-Weinberg equilibrium, how do the allele frequencies change from one
generation to the next? (Do they change from one generation to the next?)
No, if a population is at Hardy Weinberg equilibrium then the allele frequencies would not change from one generation to the next.
What is the difference between stabilizing selection, directional selection, positive selection,
disruptive selection, and purifying selection?
Stabilizing selection - favors average individuals
Directional selection - favors individuals that vary in one direction from the mean
Positive selection - For a single gene locus, directional selection may favor a particular variant
Disruptive selection - favors individuals that vary in both directions from the mean
Purifying selection - selection against any deleterious mutations to the usual gene sequence
What are synonymous DNA substitutions?
Synonymous DNA substitutions are point mutations that do not change the encoded amino acid, as most amino acids are specified by more than one codon
What are non-synonymous DNA substitutions?
Non-synonymous DNA substitutions are point mutations that are usually deleterious (negative) but can be selectively neutral or advantageous
What evolutionary forces are responsible for the
high frequencies of sickle cell anemia in parts of the
African continent?
Natural selection is the cause of the high frequencies of sickle cell anemia because of a mutation made to defend red blood cells from malaria, a major cause of death in Africa.
What is the main advantage of sexual reproduction?
What are some major disadvantages?
The main advantage of sexual reproduction is that it results in new gene combinations and produces genetic variety that increases evolutionary potential. However, recombination can break up adaptive combinations of genes, reduce the rate at which females pass genes to offspring, and divide offspring into genders reduces the overall reproductive rate.
This question (number 33) has a figure to refer to go back to the study guide to answer!
Refer to the study guide
