__________________________ is built across a river. It changes the way the water flows.

• dam

• sun

• moon

• body

Dams have been helpful to humans, but they get in the way of salmon __________________________.

• sun

• body

• trace

• migration

​ (a)   are traces of organisms that lived at least 10,000 years ago. Tooth marks and leaf prints are examples of ​ (b)   fossils. Bones and teeth are examples of ​ (c)   fossils.

• Fossils
• trace
• body

When an organism is ________, all its members are gone forever.

• extinct

• dead

• migrate

• trace

The ​ (a)   can be visible during the day and at night. However, the ​ (b)   is visible only during the day.

• moon
• sun

Match each organism with an environment where it will do well.

• seaweed

• desert

• saguaro cactus

• ocean

• rose bush

• city garden

A sunfish would not be able to survive in a forest because ________.

• a sunfish needs to live in water
• an animal must live in a place that meets its needs

• both A and B

A structure built to block the flow of water is called a _______.

• dam

• bridge

• tunnel

• canal

The seasonal movement of animals from one region to another is known as _______.

• migration

• hibernation

• estivation

• nomadism

_______ are the preserved remains or traces of living things from the past.

• Fossils

• Artifacts

• Minerals

• Crystals