Evolution best explains O
the biological changes in species over time
O
how organisms obtain energy
why organisms originally came into existence
O
O
the ways organisms grow and develop

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

When you run, you begin to breathe heavier and faster. your heart beats more quickly, bringing more oxygen to your cells. which organ systems are working together here?

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.