•A cell is the _____ structural and functional unit of all living things.

• basic

• secondary

• unimportant

•The human body consists of ____________ of cells.

• millions and millions

• thousands and thousands

• trillions and trillions

•Cells are too ____ to see with the human eye.

• big

• small

• ample

•The invention of the microscope allowed scientists to discover that cells existed.

• True

• False

•In ____, an English scientist named __________ made a simple microscope.

• 1665, Robert Hooke

• 1600, Anton Van Leeuwenhoek

• 1838, Matthias Schleiden

•Hooke used the microscope to look at a _________, which is the dead cells of oak bark.

• piece of rock

• piece of paper

• piece of cork

•Hooke saw small, box-shaped structures in the cork, which he called cellulae.

• False

• True

•In the late _____, ________________, a Dutch scientist, made another microscope.

• 1838, Shleiden

• 1665, Hooke

• 1600s, Anton van Leeuwenhoek

Leeuwenhoek examined pond water, milk, and other substances.

• True

• False

Leeuwenhoek was surprised to find _________ in these substances.

• dead organisms

• living organisms

• nothing