Question

5 multiple choice 6.25 points
the bottleneck effect is used to describe an event where a population decreases. one example involves the northern elephant seal. they have a reduced genetic variation due to a population bottleneck humans inflicted on them in the 1890s. hunting reduced their population size to as few as 20 individuals at the end of the 19th century. their population has since rebounded to over 30,000, but they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted. which phrase best explains this change in gene frequency?
natural selection
genetic drift
gene flow
speciation
6 multiple choice 6.25 points
when the first antibiotics became available in the late 1940s and early 1950s, these antibiotics were effective against all bacterial infections. today however, there are a multitude of antibiotic resistant bacterial infections. what conclusion can be drawn?
antibiotics of today are not as strong as those in the past.
antibiotics cause dna mutations in bacteria, and over time, this has led to resistance.
over time, bacteria have turned into viruses, and antibiotics have no affect over viruses.
bacteria have become resistant to antibiotics over time due to evolution by means of natural selection.
7 multiple choice 6.25 points
scientists estimate that the earth formed some 4.6 billion years ago with the first forms of life appearing around 3.5 billion years ago. these first forms of life were simple prokaryotes. later, the first photosynthetic organisms resulted in more ______ in the atmosphere. this allowed for more higher level organisms to appear on earth.
oxygen
sulfur
carbon
nitrogen

Explanation:

• Question 5: The bottleneck effect is a type of genetic drift. Genetic drift is a change in allele frequencies in a population due to random sampling (like a drastic population reduction). Natural selection is based on traits being favorable or not. Gene flow is the transfer of genes between populations. Speciation is the formation of new species.
• Question 6: Bacteria becoming resistant to antibiotics over time is due to natural selection. Some bacteria may have mutations that make them resistant. When antibiotics are used, non - resistant bacteria die, and resistant ones survive and reproduce. Antibiotics today are often stronger. Antibiotics do not cause mutations in the way described (mutations are random). Bacteria do not turn into viruses.
• Question 7: Photosynthetic organisms (like cyanobacteria) produce oxygen as a by - product of photosynthesis. Sulfur, carbon, and nitrogen are not the main products of photosynthesis that led to higher - level organism evolution in the way described.

Answer:

• Question 5: genetic drift
• Question 6: Bacteria have become resistant to antibiotics over time due to evolution by means of natural selection.
• Question 7: oxygen