What needs to happen for a species to form

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important

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

Azoologist is studying four very closely related feline species. she wishes to compare their gestation periods. an observational study is conducted where the zoologist observes the gestation period of 50 randomly selected felines in each species. a one-way anova test is run to test the hypothesis that the average gestation period is the same for each of the four species. a level of significance of 0.05 is used, and a p-value of 0.01 is calculated. based on this result, the conclusion that can be drawn is that: