The first organisms on Earth were able to transform the carbon dioxide in the air into what essential element needed for modern life?

A. Hydrogen

B. Helium

C. Nitrogen

D. Oxygen

In urban areas, fine particles caused by dust or pollution often cloud the air close to the ground. Which of the following terms best defines this event? a. ozone b. smoke pollution c. haze d. acid rain

Enzymes are used in which types of cells? plant cells animal cells both of the above neither of the above

What are the functions of the skeletal system? define hematopoiesis. where does it occur?

What is one criteria that must be met in order for an ecosystem to be stable

Explain what factors might work together to allow a great soccer player to kick a ball far.

What would you expect to happen if sea otters were removed from this food web? Check all that apply. The population of elephant seals would decrease. The population of kelp crabs would increase. The population of kelp would increase.

When blockages in the bloodstream read the Brian it can cause blank?

A gazelle is born with slightly longer legs which allow it to run faster than the other gazelles in the herd. This adaptation came may have come about because a. the gazelle needed to be able to run faster. b.

In a population of deer mice, the allele for white hair is recessive and the allele for brown hair is dominant.

What makes a molecule a saturated fat?