What are the three reasons?
asked Apr 19, 2012 by anonymous

Your answer

Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:

To avoid this verification in future, please log in or register.

1 Answer


Some energy is used by organisms at each trophic level for their vital life processes such as cellular respiration and corresponding cellular functions which require ATP.

Some energy rich molecules are indigestible by consumers on the upper trophic levels because they lack the correct digestive enzymes. For example, humans are unable to digest many fibrous plants. 

Absorption is never 100% efficient. There is always some material which has the potential to be digested but is not absorbed. It is excreted as waste.

answered Apr 20, 2012 by mshelton Level 3 User (8,500 points)
1,815 questions
1,124 answers
111,021 users