16.How are rocks grouped within each unit of geologic time similar? 17. A unit of geologic time is usually characterized by
of a dominant life-form.
18. What does the abbreviation Ma stand for?
19. When did Precambrian time begin?
20. What species were common during the Cambrian Period?

Which would prevent a plant from growing

Which sentence best describes the relationship between chlorophyll and the chloroplast? a.) chlorophyll is a chemical found in a chloroplast. b.) chloroplast is a chemical found in a chlorophyll. c.) both chlorophyll and chloroplasts are found in animals. d.) both chlorophyll and chloroplasts make carbon dioxide.

Explain the significance of the increased cell specialization of the volvocine line