1. what are all living things composed of?

a. only one cell

b. one or more cells

c. at least 100 cells

d. at least a trillion cells

2. about how much of the human body is water?

a. 10%

b. 50%

c. 70%

d. 99%

3. which of the following is not a stimulus that living things sense and respond to?

a. dna

b. light

c. hunger

d. sound

4. what is dna?

a. carbohydrate

b. protein

c. nucleic acids

b. amino acids

5. what is true of all organisms?

a. organisms grow and develop.

b. organisms always remain the same size.

c. organisms grow but never develop.

d. organisms always shrink and divide.

6. which of the following characteristics is shared by all organisms?
a. all organisms are composed of two cells.

c. all organisms can move.
b. all organisms can smell and taste.

d. all organisms have cells that contain dna.

7. what is the smallest functional and structural unit of life?
a. the membrane

b. the cell

c. the stimulus

d. the metabolism

8. how do organisms carry out chemical activities of life?
a. through sexual reproduction

c. by using energy
b. through asexual reproduction

d. by increasing metabolism

fill in the blanks below using the following terms:

asexual reproduction sexual reproduction

9. most single-celled organisms produce offspring by

10. in the process of two parents produce offspring with traits of both parents.

Our planet has experienced five major extinctions in the four billion year history of life. the first, 450 million years ago, occurred shortly after the evolution of the first land-based plants and 100 million years after the cambrian explosion. the second extinction occurred 350 million years ago, causing the formation of coal forests. next earth experienced two mass extinctions during the triassic period, between 250 and 200 million years ago. the fifth mass extinction occurred 65 million years ago, ending the reptilian dominance of the earth. according to richard leakey, the sixth mass extinction is happening right now. leakey suggests that we, the human race, are the cause. each year, at our hand, approximately 50,000 species vanish from earth. he believes that man is destroying earth at a rate comparable with the impact of a giant asteroid. leakey's statistics indicate that 50% of earth's species will become extinct within the next 100 years assuming leakey's hypothesis of a sixth mass extinction to be true, how will we expect the model to change? a) a sharp spike in the graph approximately 100 million years from now b) a dip in the graph, followed by a sharp spike about 100 million years from now c) a sharp spike in the graph immediately following the "0" location of the x axis d) a plateau following the "0" mark on the x axis, followed by a gradual rise to a new peak