projections on either side of a bird's feather.
teeth in frogs used to hold prey.
the interior of an organism containing the organs of digestion, excretion, and reproduction.
a metabolic waste product formed in the liver.
the phase of the heartbeat in which the ventricles contract and force blood into the arteries.
a tiny hard particle shaped like a star or spike that forms the skeleton of sponges.
an underground stem of a fern.
the nerve that carries impulses from the retina to the occipital lobe of the brain.
an immature form of some invertebrates.
the bursting of an infected cell.
an organism's function within its environment.
a coiled tube in the inner ear filled with fluid and lined with hair cells.
the site where waste materials and eggs leave the body in a shark.
a plant hormone that regulates cell elongation.
in plants and algae, it is a reproductive structure that produces sperm.