BIOL 202 Chapter Notes - Chapter 6: Gastrointestinal Tract, Internal Fertilization, Cestoda
18 Jun 2015
School
Department
Course
Professor
Document Summary
Pedal locomotion (muscular: waves across the body. Cephalization: concentration of bundles of nerves around the sensory organs. Subepidermal nerve plexus resembles nerve net of cnidarians. Mechanoreceptor (receptor excited by pressure: detects tubellerian"s body position in reference to the direction of gravity, like georeceptors. Photoreceptors: two simple eyespots called ocelli, orient animal in direction of light. Diffusion: provide oxygen to tissues at adequate pressure and remove waste products. Pharynx functions as ingestive organ, free end of tube lies in a pharyngeal sheath and can project out of mouth when feeding. Pharyngeal glands secrete enzymes that help break down food into smaller units that can be taken into the pharynx. In the digestive cavity, phagocytic cells engulf small units of food and digestion is completed in intracellular vesicles. Many reproduce asexually by transverse fission: fission begins are constriction behind the pharynx, two or more animals that result from fission are called zooids, regenerate missing parts after separating from each other.
