Question 23
Domestication is the act of separating a small group of organisms (wolves, in this case) from the main population, and select for their desired traits through breeding. Over thousands of years, the domestication of wolves resulted in the loss of some of the more aggressive traits, like the instinctual, defensive behavior in the presence of humans (barking or howling, bearing their teeth, poising to attack, or running away), and the size and shape of their teeth. Now humans select for a variety of traits in dogs based on personal preference and companionship, instead of as a way to increase human survival. What type of selection does this scenario represent; Natural or Artificial?
a
Artificial Selection
b
Natural Selection
Question 24
Which of these statements about natural selection is correct?
Natural selection on Make a GIF
a
The fittest organisms are better able to survive and reproduce in an environment.
b
Populations tend to produce fewer individuals than the environment can support.
c
Traits that negatively affect survival are more likely to be common in the population.
d
A stable environment helps shift a population’s genetic variance toward a new trait.
Question 25
Read the passage about stem cells.
Present in all kinds of tissues, stem cells have the unique ability to develop into other kinds of cells if necessary. An organism's stem cells can transform into brain cells, blood cells, muscle cells, or any other specialized cell found in the organism. Planarian worms have an extremely high stem cell count throughout their bodies.
Which answer best describes an advantage to a planarian worm from having a high stem cell count?
a
a planarian worm's cells can never truly die
b
planarian worms can adapt to any environmental changes
c
planarian worms are able to evolve faster than other organisms
d
a whole new planarian worm can grow from a tiny piece of another
d
a whole new planarian worm can grow from a tiny piece of another