The oxygen level of a lake suddenly starts decreasing. A biologist believes that photosynthetic organisms in the community have become less efficient at producing oxygen. A geologist believes that changes in the ground have increased the inflow of water into the lake. Why are both of these options valid scientific hypotheses

Which of the following statements is accurate about evolution? question 10 options: natural selection only eliminates odd individuals. evolution means that a population never has changes in its genetic frequencies. mutations are always harmful. evolution means that a population undergoes changes in its gene frequencies over time.

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.

Which process takes place last in the human being which process takes place last in the development of a human being