What is true of mass extinctions?
a all life on earth dies when a mass extinction happens
b in each mass extinction, over 50% of animal species died.
c mass extinctions happen frequently.
d there is no evidence for past mass extinctions.

This is the amino acid cysteine. circle the amine group, put a box aroundthe carboxylic acid group and use a different colored pencil/pen to circle the sidechain (r group). h o | ||nh2— c- c-oh | ch2 | sh

Identify the examples in which sam interacts only with natural resources

Which statement is the best summary of the model? a-a series of aerobic and anaerobic reactions take place in cells b- the sun's energy moves through trophic levels in a food chain c-light energy is converted into stored chemical energy plants.d- food molecules are broken down in the cells if living things.