Measuring Populations

Question 1

Explain how and why natural selection has allowed species such as sharks and alligators to remain genetically stable for thousands of years.

Revolt · Accepted Answer

These species have experienced long-term stabilizing selection; individuals with extreme phenotypes are selected against, keeping the population near an already-optimal mean and producing little net genetic change over time.

Question 2

What distinguishes disruptive and directional selection pressures when both select for extreme genetic traits?

Revolt · Accepted Answer

Directional selection favors only one phenotypic extreme and shifts the population mean; disruptive selection favors both extremes and can split the population into two divergent groups.

Question 3

Natural selection is best described as _______.a.disruptive selectionb.stabilizing selectionc.a mechanism of evolutiond.directional selection

Revolt · Accepted Answer

C

Question 4

Among humans more boys are born than girls, but women have significantly higher life expectancies. What is the significance of this?

Revolt · Accepted Answer

The higher male birth rate is offset by higher male mortality, resulting in an approximately 1:1 sex ratio among reproductive-age adults.

Question 5

Adaptive melanism describes selection for _______.a.mottled pigmentationb.lighter pigmentationc.darker pigmentationd.more colorful pigmentation

Revolt · Accepted Answer

C

Question 6

Regular distribution is observed for many organisms due to _______.a.the need to maximize exposure to sunlightb.the need to avoid predatorsc.interactions between individualsd.the plentiful availability of water

Revolt · Accepted Answer

C

Question 7

Contrast disruptive and stabilizing selections.

Revolt · Accepted Answer

While stabilizing selection selects for the most common, normal traits in a population, disruptive selection selects for extremes. Disruptive selection eliminates the very intermediate traits that stabilizing selection preserves.

Question 8

The most common type of distribution pattern(s) in nature is(are) _______.a.regularb.randomc.clusterd.a and b

Revolt · Accepted Answer

C

Question 9

Explain why random distribution patterns for species are the rarest in nature.

Revolt · Accepted Answer

Resources and conditions in nature are rarely uniform, so organisms tend to cluster around favorable patches or space themselves regularly through interactions; truly random placement is therefore uncommon.

Question 10

Which of the following is not true about the distribution of species?a.A species’ native range does not include areas where it was introduced by humans.b.Some species have a range they inhabit only for breeding.c.Seasonal ranges include areas where species are found for part of the year.d.All the organisms in an ecosystem share distribution patterns.

Revolt · Accepted Answer

D

Measuring Populations Answers

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