What is an explanation of why producers are always found at the lowest trophic level?

What environmental cues and landmarks do the geese use to determine the timing and direction of their migration over the mountains? how do they find their way?

Cladistics is a way of classifying organisms by examining the characteristics of their ancestors and descendants and depicting the relationships in a cladogram. which of the following best describes a challenge in classifying organisms this way? a. there are millions of species on earth, and a cladogram is not a practical means for classifying all of them. b. it is impossible to tell which organisms are most closely related to each other using a cladogram. c. cladograms are detail-oriented and do not provide a useful understanding of evolutionary relationships. d. there is a limited number of ways to organize the information, so most cladograms end up looking very similar.

Which substance contains thylakoids? a) nadph b)atp c)stroma d)chloroplast