2. A. They cause a harmful change. B. They cause a helpful change and the soil firms up around them. C. They cause a helpful change since their digested materials enrich the soil. D. They cause a harmful change since their digested materials pollute the soil.

3. A. They have no natural predators. B. They release toxins that pollute the water. C. They are predators of many native species. D. They release gases that hurt other species.

4. A. It increases the population of others plants. B. It decreases the population of fish and other animals. C. It increases the amount of oxygen reaching other aquatic plants. D. It decreases the amount of sunlight reaching other aquatic plants.

5. A. Familial adaptation B. Structural adaptation C. Behavioral adaptation D. Environmental adaptation

6. A. A frog has slimy green skin B. A flamingo is born with white feathers C. A snowshoe hare turns white in the winter D. A dog has a different fur color than its mother

8. A. behavior B. mutation C. alteration D. adaptation

9. A. 2/3 B. ¾ C. ¼ D. ½

10. A. It attracts insects that nest in the mane. B. The mane blows in the wind to help keep the lion cool. C. The mane makes the lion look bigger and protects its neck. D. The mane allows lions to recognize other males in the same pride.

11. A. Every generation has some bacteria resistant to antibiotics B. A new generation of bacteria developed with a natural resistance to antibiotics C. Some bacteria adapted to living with antibiotics and passed their genes to their offspring D. Bacteria changed their environment so they would no longer live where antibiotics are used.

12. A. Increased home building B. Decreased amount of prey C. Widespread use of pesticides D. Introduction of new predators

13. A. The insect population increases. B. The insect population decreases. C. The entire insect population dies. D. The entire insect population mutates.

14. A. The habitat will remain unchanged. B. The habitat will become more polluted. C. The habitat will immediately be exactly like it previously was. D. The habitat will gradually become more like it previously was.

15. A. Extinct B. Vulnerable C. Endangered D. Jeopardized