Atree of life depicting the hypothetical phylogeny of the three domains is shown above. at which letter is located the common ancestor that would contain membrane-bound organelles?
a) a
b) b
c) c
d) d

Milk production during breastfeeding is increased by the suckling of a newborn from his mother's nipple. this type of feedback mechanism best describes a positive or negative

This is the interaction of two organisms where one is and the other is neither nor harmed.

1. in what ways have non-native species been beneficial? 2. what are some of the hypotheses for the collapse of honeybee colonies? 3. distinguish between regional and functional extinction. 4. why is it difficult to measure background extinction rates? 5. what three factors are most important in causing extinction rates to climb?