Question 1

Which of the following best describes Darwin's main conclusion from his observations of animals and plants on the Galapagos Islands?

Accepted Answer

Animals and plants on the Galapagos Islands originated from South America but became modified on each island.

Question 2

Which of the following is NOT a necessary condition for natural selection to occur, according to Darwin's mechanism?

Accepted Answer

All variation among individuals is heritable.

Question 3

A population of beetles has two alleles for shell color: green (G, dominant) and brown (g, recessive). If the frequency of the recessive allele ($$q) is 0.3$$, what is the expected frequency of homozygous recessive individuals ($$q^2) $$under Hardy-Weinberg equilibrium?

Accepted Answer

$$q^2 = 0.09$

Question 4

Which scenario best illustrates frequency-dependent selection?

Accepted Answer

A rare mouth-handedness allele in cichlid fish becomes more advantageous as it becomes less common.

Question 5

In the context of balancing selection, which equation correctly represents the frequency of a recessive allele ($$q) $$under heterozygote advantage, given selection coefficients $$s$$ and $$t$$?

Accepted Answer

$$q = \frac{s}{s+t}$$

Question 6

Which of the following is an example of intrinsic reproductive isolation?

Accepted Answer

Two populations of frogs breed at different times of the year.

Question 7

A marine fish lives in seawater where the salt concentration is higher than in its body fluids. Which of the following is a physiological adaptation that helps the fish maintain osmotic balance?

Accepted Answer

Actively transporting excess salt out through the gills.

Question 8

Which of the following best describes the difference between osmoregulators and water conformers?

Accepted Answer

Osmoregulators actively maintain internal osmolarity, while water conformers allow their internal osmolarity to match the environment.

Question 9

Which of the following is an example of sympatric speciation?

Accepted Answer

A population of fruit flies becomes reproductively isolated due to a shift in host plant preference within the same geographic area.

Question 10

Which reproductive isolating mechanism is illustrated when two closely related species of plants release pollen at different times of the year?

Accepted Answer

Temporal isolation

Question 11

If a population is under directional selection against a dominant allele, what is the expected change in frequency of the dominant allele ($$D) $$after one generation, given a selection coefficient $$s$$?

Accepted Answer

$$D = 1 - s$$

Question 12

Which of the following best explains why recessive alleles are rarely eliminated from a population, even under directional selection against them?

Accepted Answer

Recessive alleles can be hidden in heterozygotes, making them less exposed to selection.

Question 13

A population of marine invertebrates is isotonic to its environment. What does this mean for its water and solute balance?

Accepted Answer

Its internal osmolarity matches the environment, so there is minimal net water or solute movement.

Question 14

Which of the following is an example of mechanical isolation as a reproductive barrier?

Accepted Answer

Two insect species cannot mate because their reproductive organs do not fit together.

Question 15

Which of the following best describes the process of allopatric speciation?

Accepted Answer

A population is divided by a geographic barrier, leading to reproductive isolation and divergence.

Question 16

Which of the following is a real-world example of heterozygote advantage?

Accepted Answer

Individuals heterozygous for the sickle cell allele are more resistant to malaria.

Question 17

Which of the following best explains why population sizes remain relatively constant over time, despite organisms' great potential fertility?

Accepted Answer

Limited resources and competition prevent exponential population growth.

Question 18

Which of the following is NOT a possible output route for water in osmoregulators?

Accepted Answer

Absorption through the skin

Evolution, Speciation, and Osmoregulation: Key Concepts in Biology

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