What is the function of heart valves?

They return blood to the heart.

They force blood to flow out of the heart.

They regulate the heart rhythm.

They prevent blood from flowing backwards.

Which statement describes renewable resources?

The barn above looks red because certain rays of light are absorbed by the barn and other rays of light are reflected by the barn. What must be true about the original sunlight before it hits the barn?

A scientist hypothesizes that all trees in warm areas produce flowers before the rainy season begins. Which is a limitation to testing this hypothesis?

Does anybody have the answers for lesson 19: the human body unit test biology B unit 4: the human body

Which group of living things can move energy from consumers at the top of an energy pyramid back to producers at the bottom? * A. decomposers B. producers C. consumers D. Nothing can move energy back to the bottom of an energy pyramid.

What chance did you have of being born with cystic fibrosis

What is the 2 type of variable are being used in a controlled experiment?

Abiotic factors are the nonliving components of the biosphere. Which of the following is an abiotic factor that adversely affects human populations?

What is the genetic code? How is the genetic code similar to a "language"?

A metamorphic rock can form when rock comes in contact with lava or magma. Do you think the rock gets hot enough to melt? Why or why not?