Standard 4.4 Retake

As the ocean becomes slightly more acidic over the next hundred years, the sea urchin population will contain....

• only sea urchins that tolerate low pH water

• more sea urchins that tolerate high pH water than low pH water

• equal amounts of sea urchins that tolerate high pH and low pH water

• more sea urchins that tolerate low pH water than high pH water

Based on Figure A, how will sea urchin larvae change as the ocean becomes more acidic?

• They will get shorter

• There is no way to tell

• They will not change

• They will get longer

Which of these pieces of information would tell us whether larval size differences are due to natural selection?

• the differences are genetic

• the differences are due to changes in pH

• the differences are environmental

• the differences are temporary

Suppose it can be shown that the difference in larval size is determined by multiple genes. What is most likely to happen over time to the allele frequencies in the population as ocean acidification increases.

• the allele frequencies for shorter larvae remain constant

• the allele frequencies for shorter larvae increases

• the allele frequencies for shorter larvae change seasonally

• the allele frequencies for shorter larvae decreases

Which of the following statements BEST describes the relationship between natural selection and adaptation for sea urchins experiencing ocean acidification, and is supported by evidence in Figure A?

• The experiment doesn't show the relationship between natural selection and adaptation because there isn't one. Adaptation is the result of organisms learning to express different traits in different environments.

• Adaptation depends on natural selection, which depends on genetic variation and selective pressure from a changing environment; sea urchins who are best suited to survive and reproduce pass on their traits to the next generation, and so the populations adapt.

• Natural selection will always force the smallest individuals to die off in any population. Therefore, the shorter sea urchin larvae will not survive and so most populations will adapt to have longer larvae.

• Sea urchin larvae will adapt to the changing ocean environment because otherwise they won't survive. This is called natural selection.

Explain how natural selection leads to adaptation in populations when environmental conditions change, using the given data about sea urchin larvae and ocean acidification as evidence.