a membrane protein activated by the hormone first messenger to activate formation of cyclic AMP

cell-surface receptor that activates membrane-bound G-proteins to transmit a signal from the receptor to nearby membrane components

appearance of a plant tumor

organ that stores and concentrates bile

structure on the gametophyte in which gametes are produced

prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs and sperm) prevent fertilization from taking place

a multicellular haploid life-cycle stage that produces gametes

multicellular stage of the plant that gives rise to haploid gametes or spores

channel between two adjacent animal cells that allows ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate

hormone secreted by the small intestine in the presence of fatty acids and sugars; it also inhibits acid production and peristalsis in order to slow down the rate at which food enters the small intestine

digestive phase beginning once food enters the stomach; gastric acids and enzymes process the ingested materials

hormone which stimulates hydrochloric acid secretion in the stomach

inner layer (from endoderm) that lines the digestive cavity

opening that serves as both a mouth and an anus, which is termed an incomplete digestive system

digestive system consisting of a single opening