In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

Question: What are produced in both the male and female reproductive systems in humans? Answer: sex cells
Sex cells are produced in both the male and female reproductive systems in humans.

Question: During which phase does dna replication occur in the cell cycle? Answer: synthesis
During the synthesis phase in the cell cycle, dna replication occurs.

Question: What phenomenon is crowding out other species and making all the other causes of extinction worse? Answer: human overpopulation

Human overpopulation is crowding out other species and making all the other causes of extinction worse.