Where do fossil fuels come from?
a. from cellular respiration
b. from heat energy
c. from minerals
d. the remains of living things

Drag the tiles to the correct boxes to complete the pairs. match each cell organelle with its description.

If a young male's body is just beginning the process of producing sperm, when is it likely that he would ejaculate mature, viable sperm"

Red blood cells are responsible for transporting oxygen in the blood. people with sickle cell anemia were born with a defective gene that results in sickle-shaped red blood cells. individuals with the disease often suffer pain in their extremities due to the build-up of these cells causing blockages in the blood vessels. the shape of the blood cells also reduces the amount of oxygen transported in the blood.