The element was poisonous to the first forms of life on earth until they evolved to take advantage of it by using cellular respiration. what is it? a. hydrogen b. nitrogen c. oxygen d. sulfur

Which of the following examples can cause gene flow between populations? a.an increase in predators to a population of zebra b.a volcanic eruption that kills half of a population of mice c.bird droppings that contain seeds from a different location d.a person that sprays a toxin on a group of mosquitoes

Which animal is a producer in this ecosystem

Moving down the ramp from 6 meters to