The cell membrane consists of two layers of that have embedded to allow certain molecules to pass through.

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

In which of the following relationships is one organism always benefited while the other organism is always harmed

This is a biological reaction due to a stimulus. i need this quickly !