Two of the three requirements for evolution by natural selection are strongly supported by the data. Which two, and how are they demonstrated?

The pre-storm distribution of toepad size across multiple values demonstrates ( 1. )while the change in that distribution from before to after the storm, toward larger toepad sizes, demonstrates ( 2. ) . The other requirement has not been demonstrated by this data set, but could be supported by other data.

Q3.15. Which of the following statements about genes and alleles is TRUE?

Quantitative traits are each determined by a single gene that has a small number of alleles.

When a gene has two alleles, the allele frequencies in a population move toward equilibrium values of 0.5 for each allele.

All else being equal, alleles associated with higher reproductive success increase in frequency.

If the frequency of an allele in a population has changed, then natural selection has necessarily occurred.


A. variation (requirement 1)

B. heritability (requirement 2)


A. heritability (requirement 2)

B. selective survival (requirement 3)

Q4.15. DDT is an insecticide that was used extensively in agriculture in the mid-1900s to kill many insect pests, including the boll weevil (pictured below), another pest of commercial cotton. DDT was initially effective at controlling boll weevil outbreaks, but after about a decade DDT became much less effective, because many populations of boll weevil had evolved resistance to DDT. Which of the following conditions would biologists say was required for the evolution of DDT resistance in a population of boll weevils?

Boll weevils in the population learned to adapt to the high levels of DDT in the environment.

The boll weevil population needed to evolve DDT resistance in order to avoid extinction.

A few boll weevils in the population were resistant to DDT before it was ever used.

Exposure to DDT caused specific, nonrandom mutations for DDT resistance within the population.

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