Download Answers Lectures 2 and 3, Exam IV

Answers, Lectures 2 and 3, Exam IV
Warm Up
1. Population- localized group of individuals of the same species.
2. Species- a group of population that interbreeds and produces fertile offspring.
3. Fitness- Contribution an individual makes to a gene pool of the next generation, relative to the
contribution of other individuals. An organism is more fit if it can produce more offspring than
another competing organism.
4. Discrete characters- can be classified on an either/or basis. Usually determined by a single gene
locus with different alleles that produce distinct phenotypes. Quantitative characters- most
heritable variation; vary along a continuum in a population. Usually results from the influence of
two or more genes on a single phenotypic character. Height is quantitative. Blood type is
discrete. Skin color is quantitative. Wing color, in this case, is discrete.
5. Defined what each meant and matched to its example:
a.) In population genetics, directional selection is a mode of natural selection in which a
single phenotype is favored, causing the allele frequency to continuously shift in one
direction
b.) Disruptive selection, also called diversifying selection, describes changes in population
genetics in which extreme values for a trait are favored over intermediate values.
c.) Stabilizing Selection is the opposite of disruptive selection, instead of favoring
individuals with extreme phenotypes, it favors the intermediate variants.
Worksheet
1. Convergent evolution- the same environmental factors can influence two unrelated organisms
to have similar characteristics.
2. Molecular phylogeny, (also used with groups that DO leave fossil records, but this is the only
way that organisms without fossil records can be classified, such as sea urchins). It is looking at
how close nucleotide sequences in genes are between two or more various organisms in order
to see how closely they are related.
3. Adaptations are characteristics that help organisms survive/ reproduce more efficiently
depending on their particular environment. Natural selection which is a process in which
individuals with these certain inherited traits (the adaptations) are able to leave more offspring
than individuals with other traits. Descent with modification describes life’s unity and diversity:
all organisms are united by common ancestors, and the diversity among various organisms has
arisen by the adaptations through descending generations, from that particular ancestor, that
enabled them to survive better.
4. Great deal; able; beneficial; fittest
5. Heritable (gametic cells), populations, NO.
6. Mutations; Only those in gametic cell lines and those that are advantageous. C would be the
only one maintained. A would not be advantageous; B is in the somatic cell line.
7. Asexual reproduction allows for more offspring than sexual reproduction. For sexual
reproduction only females can make offspring. 1. Resistance to pathogens: enables more
genetic variation that can protect against these, evolution. 2. Ability to combine beneficial
mutations (mutations from mom and dad combine). 3. Ability to more quickly get rid of
deleterious mutations through genetic recombination (the shuffling of genes). Crossing over(
genetic recombination).
8. Heterozygote advantage- The heterozygote’s phenotype is more advantageous than either
recessive or dominant ones. Example is sickle-cell anemia.
Frequency-dependent selection- the rate of fitness of a particular phenotype declines if it
becomes too common in the population *scale-eating fish, left and right mouthed.