Before there was life on earth, which gas was absent from the ancient atmosphere?

A. ammonia

B. methane

C. nitrogen

D. Oxygen

Many insects have become resistant to pesticides. in which population of insects would you most expect pesticide resistance to develop?

Prior to c-section surgeries, what outcome would best describe the natural section forces acting on the size of human head? directional selection disruptive selection fathead selection stabalizing selection

Mixtures are very different from compounds. Mixtures can be physically separated into different components and compounds cannot be physically separated. Which of the following is NOT a mixture? A. salt water B. air C. soil D. sugar

What is a scientist called who observes animals in order to explain their behavior? ecologist ethologist environmentalist psychologist

One example of how natural selection can change the distributuion of a atrait

The statement, "Energy can neither be created nor destroyed, but can change from one form to another," is the first law of thermodynamics the second law of thermodynamics the third law of thermodynamics scientifically unproven

How do plants living in deep shade manage to make their food

What can cells can be defined as

What brings greater concentration of dissolved nutrients to the ocean floor?

The power was off last night, and the yeast cultures in your incubator cooled down from 25 degrees to 20 degrees centigrade in temperature. to your great relief, you find that the yeast cells did not die.