Which of these is a characteristic of index fossils?
a/found in the topmost rock layer.
b/found in many layers of the same rock.
c/have already established relative age.
d/are limited to a particular geographic location. (hu)

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.

the growth of the plants is affected by the heat of the light. what is the student doing?