What cellular structure is used in this process?

Could someone me with number one you

What would be the result if crossing over did not happen during meiosis in humans? a. there would be less genetic variation in humans. b. parents would be more likely to look like their children. c. the human population could not reproduce. d. children would have more chromosomes.

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?