1. What important function do microorganisms have in an ecosystem?

They produce food from sunlight.
They reduce the number of large animals.
They decompose dead organisms.
They help to clean the air.

2. What does yeast do in bread dough and cheese?

It grows and releases waste products.
It absorbs sugars and changes them to starch.
It acts like a spice and flavors the food.
It breaks down into parts.

3. Viruses sometimes cause a disease because viruses ______.

take over the host cell
are made of bacteria
are not a part of the natural world
are found everywhere in the world

4. Louis Pasteur discovered that ______.

Bacteria can enter the food from the air
Heating is sometimes enough to kill bacteria
Bacteria in food comes from somewhere outside the food
Bacteria can cause food to spoil

5. By noticing that some organisms didn't grow near mold, Alexander Fleming discovered penicillin. What kind of organism does penicillin kill?

Viruses
HIV
Influenza
Bacteria

6. Bacteria are useful in protecting the environment.

They have no effect on the environment.
The cost of bacteria is too high to use it.
Some forms of bacteria break down pollutants.
No one knows what effect some bacteria have.