BIOL 117 EXAM 2 PRACTICE QUESTIONS WITH
DETAILED EXPLANATIONS 2026
◉ A woman recently completed a regimen of antibiotics. Which of
the following is most likely?
Answer: Her gut microbiome is less diverse.
◉ Which of the following is true?
Answer: Over time, the human gut microbiome has decreased in
diversity.
◉ Based on current research, a future where which of the following
groups is given a gut microbiome supplement is most likely?
Answer: Babies born via C-section.
◉ If trends continue, which of the following is most likely?
Answer: Fecal transplants will be done more frequently.
◉ You aim to improve your gut microbiome. Which of the following
would be best for you to achieve your goal?
Answer: Eat fresh plant foods and fermented foods.
,◉ How do humans benefit from the gut microbiome?
Answer: The microbiome can help create vitamins useful for
humans.
◉ This phylogenetic tree shows the relationships among different
species of garter snakes. The colored banches show which snakes
have TTX-resistant sodium channels. Different colors represent
different amino acid sequences in the sodium channels. Is TTX-
resistance in garter snakes an example of homology (shared
ancestry) or homoplasy (convergent evolution)?
Answer: Homoplasy, because TTX-resistant sodium channels arose
independently in different snakes.
◉ The enzyme lactase breaks the sugar lactose into which
compound(s)?
Answer: galactose and glucose
◉ How does the term "lactase persistent" relate to the term "lactose
tolerant"?
Answer: A lactase-persistent person is lactose tolerant.
◉ Four individuals measured their baseline blood glucose, then
drank a litre of milk. They then measured their blood glucose levels
at regular 15 minute intervals for 60 minutes. The results are shown
in the graph below. Which individuals are lactase-persistent?
,Answer: When the blood glucose stays low
◉ What did researchers discover about the genetic mutation causing
lactase persistence?
Answer: It is found in a regulatory region (a "switch") upstream of
the lactase gene.
◉ Which discovery supports the hypothesis that evolution of the
lactase-persistence trait was driven by the use of milk in pastoralist
cultures?
Answer: Ancient pots used to hold milk are about the same age as
the lactase-persistence mutations.
◉ How could milk-drinking have provided strong favorable selection
for lactase persistence?
Answer: Milk is protein and fat-rich and therefore could have been
an important, high-quality food source.
Milk was safer to drink than water and reduced exposure to
pathogens.
Milk may have been a critical food source during times of famine.
◉ Suppose that a mutation for lactase-persistence occurred in each
of the populations described below. In which populations would the
mutation be more likely to increase in frequency over time because
of natural selection?
, Answer: a population that raises wheat and sheep
◉ Which of these are the two major sources of nitrate pollution in
rivers?
Answer: animal wastes and fertilizers
◉ Aquatic nitrate pollution can result in _____.
Answer: an algal bloom that, when the algae die and are
decomposed by bacteria, leads to hypoxia and the death of fish
◉ Which of the following groups of organisms is among the most
abundant on Earth?
Answer: Bacteria
◉ Which group was not described in Woese's tree of life analysis?
Answer: Prokarya
◉ What characteristics were used to classify organisms before
Woese's tree of life analysis?
Answer: Presence of a membrane-bound nucleus
◉ True or false? Data showing that the Bacteria were the first
lineage to diverge from the common ancestor of all living organisms
DETAILED EXPLANATIONS 2026
◉ A woman recently completed a regimen of antibiotics. Which of
the following is most likely?
Answer: Her gut microbiome is less diverse.
◉ Which of the following is true?
Answer: Over time, the human gut microbiome has decreased in
diversity.
◉ Based on current research, a future where which of the following
groups is given a gut microbiome supplement is most likely?
Answer: Babies born via C-section.
◉ If trends continue, which of the following is most likely?
Answer: Fecal transplants will be done more frequently.
◉ You aim to improve your gut microbiome. Which of the following
would be best for you to achieve your goal?
Answer: Eat fresh plant foods and fermented foods.
,◉ How do humans benefit from the gut microbiome?
Answer: The microbiome can help create vitamins useful for
humans.
◉ This phylogenetic tree shows the relationships among different
species of garter snakes. The colored banches show which snakes
have TTX-resistant sodium channels. Different colors represent
different amino acid sequences in the sodium channels. Is TTX-
resistance in garter snakes an example of homology (shared
ancestry) or homoplasy (convergent evolution)?
Answer: Homoplasy, because TTX-resistant sodium channels arose
independently in different snakes.
◉ The enzyme lactase breaks the sugar lactose into which
compound(s)?
Answer: galactose and glucose
◉ How does the term "lactase persistent" relate to the term "lactose
tolerant"?
Answer: A lactase-persistent person is lactose tolerant.
◉ Four individuals measured their baseline blood glucose, then
drank a litre of milk. They then measured their blood glucose levels
at regular 15 minute intervals for 60 minutes. The results are shown
in the graph below. Which individuals are lactase-persistent?
,Answer: When the blood glucose stays low
◉ What did researchers discover about the genetic mutation causing
lactase persistence?
Answer: It is found in a regulatory region (a "switch") upstream of
the lactase gene.
◉ Which discovery supports the hypothesis that evolution of the
lactase-persistence trait was driven by the use of milk in pastoralist
cultures?
Answer: Ancient pots used to hold milk are about the same age as
the lactase-persistence mutations.
◉ How could milk-drinking have provided strong favorable selection
for lactase persistence?
Answer: Milk is protein and fat-rich and therefore could have been
an important, high-quality food source.
Milk was safer to drink than water and reduced exposure to
pathogens.
Milk may have been a critical food source during times of famine.
◉ Suppose that a mutation for lactase-persistence occurred in each
of the populations described below. In which populations would the
mutation be more likely to increase in frequency over time because
of natural selection?
, Answer: a population that raises wheat and sheep
◉ Which of these are the two major sources of nitrate pollution in
rivers?
Answer: animal wastes and fertilizers
◉ Aquatic nitrate pollution can result in _____.
Answer: an algal bloom that, when the algae die and are
decomposed by bacteria, leads to hypoxia and the death of fish
◉ Which of the following groups of organisms is among the most
abundant on Earth?
Answer: Bacteria
◉ Which group was not described in Woese's tree of life analysis?
Answer: Prokarya
◉ What characteristics were used to classify organisms before
Woese's tree of life analysis?
Answer: Presence of a membrane-bound nucleus
◉ True or false? Data showing that the Bacteria were the first
lineage to diverge from the common ancestor of all living organisms
