What prevents multiple sperm from fertilizing an egg?

List two limitations of natural selection

An ecologist studied the same species of deer during the summer and the winter. she noticed that during the summer, when there was plenty of food, the deer were energetic and playful. however, during winter when food was scarce, the deer moved more slowly and did not run unless they needed to escape a predator. which scientific fact is best supported by her observations?

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic