Which were the earliest oxygen-producing life-forms?

a. cyanobacteria.

b. seaweed.

c. dinosaurs.

d. ferns.

Each heart muscle cell is coupled to its neighbors electrically by tiny holes called:

What organelle packages materials that will be shipped out of the cell?

Food handlers who cut raw vegetables and raw poultry on different cutting surfaces are taking steps to prevent the

Some nutrients and other types of particles can be taken into a cell when the cell's plasma membrane encloses the particles and pinches off. True or False

Which division of the nervous system regulates the activity of smooth muscle

Which of the following correctly arranges the planets by the size of their diameter? A) Uranus < Neptune < Mercury < Earth B) Earth < Mercury < Neptune < Uranus C) Mercury < Earth < Saturn < Jupiter D) Jupiter < Saturn < Earth < Mercury

How does ultra radiation cause skin cancer

How many ribose molecules are found in ATP?

Would a person be squashed by extreme gravity, float with ease, freeze, burn up, or something else

According to "Life Without Gravity," why can astronauts' muscles become weak? A. Without gravity, the blood is rerouted from the legs to the head. B. Without gravity, the body "grows" by as much as several inches. C.