The mechanism of urine formation involves three processes: filtration, reabsorption, and secretion. primary urine is formed by filtration from the blood. in primary urine, certain substances are reabsorbed into the blood and other substances are secreted into the primary urine from the blood.

Several bird species feed in a certain species of tree. each bird species feeds in a different part of the tree. which statement is true of these bird species? a. they have adapted to different niches due to competition b. they have a carnivorous relationship with the tree species. c. they have adapted to different niches due to predation d. they have a symbiotic relationship with the tree species.

Which greenhouse gas is emitted when burn fossil fuels for energy? a.nitrogen b.oxygen c.carbon dioxide d.helium

How do the sperm cells get from the stigma to the ovules?