What is the main idea behind the model of a molecular clock?
a. that neutral mutations accumulate at a steady rate
b. that certain traits are under the pressure of natural selection
c. that segments of DNA can be compared with segments of RNA
d. that phenotypes, not genotypes, are affected by natural selection

Which type of neuroglia is found outside of the brain?

How do tides affect the organisms living in intertidal zones? a. no organisms live in intertidal zones due to the tumultuous environment. b. the mechanical forces of the waves keeps the organisms clean. c. only plants live in intertidal zones because the animals float away with the waves and never return. d. the mechanical forces of the waves can dislodge the organisms from their habitat.

What was the land like over 500 million years ago? what was under the sea?