What happens to the amount of biomass at each tropic level ?

Describe the layers of the suns atmosphere?

What goes in and out of a cell respiration?

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.