BIOL 2312 Lecture Notes - Lecture 47: Salivary Gland, Gastric Acid, Common Bile Duct
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3 groups of heterotrophs based on food source: herbivores: eat only plants (ex. Algae-eating snails, sapsucking insects, cows, horses, rabbits, sparrows: carnivores: eat only meat (ex. Crabs, squid, many insects, cats, eagles, trout, frogs: omnivores: eat both plants and meat (ex. Single celled organisms: digest food intracellularly (also sponges) Multi-cellular organisms: digest extracellularly in a digestive cavity + digestive enzymes released into the cavity. Gastrovascular cavity (cnidarians + flatworms-planarians): digestive cavity has one opening = mouth + anus) Alimentary canal: has a separate mouth and anus (one-way food transport). Most primitive tract: phylum nematode (tubular gut lined by epithelial membrane, has mouth, pharynx, intestine, anus) Earthworms: digestive tract specialized in different regions for ingestion, storage, fragmentation, digestion, absorption. (mouth, pharynx, crop, gizzard, intestine, anus) Ingested food can be stored in digestive tract or fragmented (by mouth or grinding action of pebbles in gizzard of birds and earthworms) (crop stores food in birds)
