*Question*
Answer the following question given this paragraph: Practically all surfaces. Bacteria can live and grow in practically any environment. It is this ability that has made bacteria the most numerous species on the planet. Q: What is the most numerous species on the planet? Choices: - trees - viruses - humans - bacteria A:
**Answer**
bacteria

*Question*
Answer the following question given this paragraph: Caffeine is an example of a psychoactive drug. It is found in coffee and many other products (see Table below ). Caffeine is a central nervous system stimulant . Like other stimulant drugs, it makes you feel more awake and alert. Other psychoactive drugs include alcohol, nicotine, and marijuana. Each has a different effect on the central nervous system. Alcohol, for example, is a depressant . It has the opposite effects of a stimulant like caffeine. Q: What term describes a drug that has an effect on the central nervous system? Choices: - nonaddictive drug - elemental drug - steroidal drug - psychoactive drug A:
**Answer**
psychoactive drug

*Question*
Answer the following question given this paragraph: Q: Some earthworms can also reproduce asexually by fragmentation followed by what? Choices: - fertilization - germination - digestion - regeneration A:
**Answer**
regeneration

*Question*
Answer the following question given this paragraph: Some predator species are known as keystone species. A keystone species is one that plays an especially important role in its community. Major changes in the numbers of a keystone species affect the populations of many other species in the community. For example, some sea star species are keystone species in coral reef communities. The sea stars prey on mussels and sea urchins, which have no other natural predators. If sea stars were removed from a coral reef community, mussel and sea urchin populations would have explosive growth. This, in turn, would drive out most other species. In the end, the coral reef community would be destroyed. Q: What is a species that plays an especially important role in it's community called? Choices: - complement - Invasive - Leader - keystone A:
**Answer**
keystone