Background: The theory of evolution by natural selection was proposed at about the same time by both Charles Darwin and Alfred Russel Wallace, shown in Figure below , and was set out in detail in Darwin's 1859 book On the Origin of Species . Natural selection is a process that causes heritable traits that are helpful for survival and reproduction to become more common, and harmful traits, or traits that are not helpful or advantageous for survival to become more rare in a population of organisms. This occurs because organisms with advantageous traits are more "fit" to survive in a particular environment and have "adapted" to the conditions of that environment. These individuals will have greater reproductive success than organisms less fit for survival in the environment. This will lead to an increase in the number of organisms with the advantageous trait(s) over time. Over many generations, adaptations occur through a combination of successive, small, random changes in traits, and natural selection of those variants best-suited for their environment. Natural selection is one of the cornerstones of modern biology.

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Which species' traits would be more common, species A or species B?
Answer: species A

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Which species' traits would be less common, species A or species B?
Answer: species B

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Would species A's traits be more or less common than species B's?
Answer: more

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Would species B's traits be more or less common than species A's?
Answer: less

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Which species would increase in number, species A and species B?
Answer: species A

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Which species would decrease in number, species A and species B?
Answer: species B

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Would species A be less or more in number than species B?
Answer: more

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Would species B be less or more in number than species A?
Answer: less

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Which species would have greater reproductive success, species A or species B?
Answer: species A

Situation: David wants to revisit the theory of evolution proposed by Darwin and Wallace. He is particularly interested in two species of deer, species A and species B. Species A has some helpful traits, but species B has some harmful traits. He is planning to write a paper on why some species are greater in number while others are smaller in number.

Question: Which species would have lesser reproductive success, species A or species B?
Answer: species B