Learning about the Past helps us learn about the present

A ____ is any evidence of an organism that lived in the past.

• trace
• remnant
• artifact
• fossil

Fossils are often ____ preserved in rock.

• found
• hidden
• skeletons

• buried

Scientists must study how ____ change over time.

• organisms

• constants
• experiments
• variables

1. Scientists compare _______________ to understand what is similar and what is different about organisms.

• species.
• limbs

• genes.
• organisms

An underdeveloped animal or plant is called an _____________________.

• embryo
• mature
• adolescent
• infant

Vertebrates have a back ________________.

• bone
• organ
• muscle
• skin

Many organisms are ____________________, or no longer alive.

• alive
• living
• breathing
• extinct

99 out of _________ animals are extinct.

• Cannot be determined
• 50
• 100
• 10

1. It is believed a great __________________________ hit the earth to cause dinosaur extinction.

• volcano
• earthquake
• tsunami
• asteroid

Species can become ___________________________ or in danger of extinction.

• endangered
• vulnerable
• threatened
• extinct