What is the attraction between molecules of the same substance

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

Urgent. the table shows the relative blood flow through some organs in the human body that is, the percentage of blood that flows through a given organ, through which organ(s) does all the blood flow? explain the effect of exercise on blood flow to skeletal muscles.

During photosynthesis, hydrogen ions are most directly used to in the chloroplast pictured above. a) make glucose b) make chlorophyll c) produce carbon dioxide d) drive the production of atp