What is the difference in the rate of carbon exchange (in gigatons per year of carbon) between photosynthesis and respiration in the marine environment?
A. 2 gigatons/year
B. 1 gigaton/year
C. 1 gigaton/year
D. 2 gigatons/year

How does the molecular clock work? a. it analyzes the brain functionality of two different species. b. it examines and compares the physical characteristics of two different species. c. it illustrates relationships between two different species. d. it compares the number of mutations that exist in the dna of two different species.

Which statement is true for bacteria a. bacteria have complex internal structures b. all bacteria are spiral in shape c. all bacteria cause disease in animals d. bacteria break down some foods

The cretaceous period spanned the time interval between and 65 million years ago. 250 million 144 million 75 million 200 million