Natural Selection & Population Genetics
True or False: there are traits that are positive for survival and reproduction irrespective of the natural environment at the time
False
A trait is only positive or negative for survival in the context of a specific environment
Name one of the major assumptions about a population in Hardy Weinberg equilibrium.
random mating, no evolution/selection, large population size, no gene flow, etc.
True or False: extinction is a relatively rare event, since endangered species are often rescued.
False: while today many endangered species have the aid of human intervention, biodiversity on the Earth is nonetheless decreasing, and extinctions occur all the time. 99% of the species that have ever existed are extinct.
What is the term used to describe the model of lengthy periods of gradual evolutionary change alternating with brief periods of accelerated evolutionary change?
punctuated equilibrium
What does "the heavy bombardment" refer to?
meteors frequently hitting Earth, billions of years ago
True or False: Natural Selection creates beneficial mutations in the context of the environment
False: Mutations arise randomly, and once in existence those mutations are selected for or selected against.
At a particular locus in the genome on chromosome 3, there are two alleles possible: allele "A" and allele "a". 25% of the population is homozygous dominant, 25% of the population is homozygous recessive, and 50% of the population is heterozygous. What is the frequency of allele "A" in the population?
both alleles have a frequency of 50%
Provide one example of evidence for the relatedness of all species.
nucleic acids to store hereditary information, ribosomes, etc.
How could carbon-14 dating be useful in assisting a biologist in constructing a phylogeny?
Determine the relative ages of fossilized remains, which can be compared with the hypotheses presented in the cladogram
Life requires biological macromolecules such as lipids, proteins, carbohydrates, and nucleic acids. What are the two hypotheses about the source of the initial biological macromolecules?
2. Sufficient organic macromolecules arrived via meteors to Earth.
What is evolutionary fitness?
Reproductive success
If the frequency of the dominant allele at a specific locus is 40%, what percentage of the corresponding population will exhibit the recessive trait?
0.6 squared = 36%
Genetic drift
Order the following from MOST useful in constructing a cladogram to LEAST useful in constructing a cladogram: a list of homologous structures, a list of molecular sequences, a list of analogous structures
1. Molecular Sequences
2. Homologous Structures
3. Analogous Structures
True or False: Classical experiments regarding the origins of life on Earth, such as those of Miller and i Florensa, were notable because of the production of nucleic acids from inorganic precursors and energy.
False. Building blocks (such as nucleobases or amino acids) were formed in the experiments mentioned, rather than complete proteins or complete nucleic acids.
True or False: Humans breeding plants for traits that humans deem to be desirable is an example of natural selection
False: this example would be classified as artificial selection
If 64% of the population is homozygous dominant at a particular locus, what is the frequency of the recessive allele in that population?
square root of 0.64 = 0.8 = p
so q = 0.2
Evolution would occur as the B allele is selected against. One would see a lower B allele frequency in the population all else equal, and hence fewer individuals of Type B and Type AB.
What do the nodes in a cladogram represent?
The most recent common ancestor of the species connected to the node.
What aspects of RNA are critical to its central role in the "RNA World" hypothesis?
It can act as an enzyme (ribozymes are RNA's with enzymatic function) AND it can store hereditary information in a sequence of nucleotide bases.
Neither DNA nor protein can individually accomplish both of these functions.
True or False: Natural Selection is responsible for changes in frequencies of alleles within an individual over time.
False: changes in the allele frequencies of a POPULATION over time. An individual can alter GENE EXPRESSION in response to the environment, but not the underlying genetic code in a directed way (i.e. the environment may cause mutations but the specifics of the mutations are still random)
The allele frequencies at a particular locus in a population of island finches are "A" = 0.8 and "a" = 0.2. There are 1000 members of the population. 100 members of the population migrate to a different island. The allele frequencies in the 100 members of the initial population that migrated (at the same genetic locus) are "A" = 0.65 and "a" = 0.35. If there is natural selection towards the "a" allele on the second island, what can be said of the percentage of homozygous recessive individuals in the next generation on the second island?
homozygous recessive = q squared = 0.35 squared = 0.1225. So the migrating population would be expected to have 12 out of 100 individuals that are homozygous recessive. If the corresponding allele is selected for, one would expect greater than 12.25% of the members of the next generation to be homozygous recessive.
The phenomenon of components of a population becoming geographically isolated and developing into two different species over time is referred to specifically as
allopatric speciation
The following are nucleotide sequences for the same enzyme in differing species:
Lamprey: A-T-C-G-A-G-T-G
Bear: A-A-C-C-A-T-C-G
Sunfish: A-A-C-C-A-A-G-C
Newt: A-T-C-G-A-T-C-G
Human: A-A-C-C-A-T-C-G
Lizard: A-A-C-C-A-T-T-G
Draw the cladogram and name the outgroup
Starting with outgroup: lamprey, sunfish, newt, lizard, bear, human
What are the living components of stromatolites, and what major change in the Earth's environment do we attribute to the living components of stromatolites?
The living components of stromatolites are cyanobacteria, and the major change in Earth's environment attributed to cyanobacteria is the oxygenation of the Earth's atmosphere. Oxygen is a waste product of photosynthesis, and photosynthesis by cyanobacteria eventually gave off enough oxygen to alter the percentage of oxygen in the atmosphere.