Animal Biology Exam 2 study guide

Animal Biology Exam 2 study guide - Animal Biology Exam 2...

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Animal Biology Exam 2 study guide. Chapter 7 Cnidaria All aquatic (most marine a few freshwater) Dipoblastic (having a body derived from only two embryonic cell layers (ectoderm and endoderm, but no mesoderm) Tissues present (true tissue) Radial symmetry in most Acoelomate (no body cavity) Feeding and digestion Gastrovascular cavity- primary organ of digestion and circulation Mouth only no anus Tentacles- capture and pass to mouth Gland cells- extracellular digestion Intracellular digestion continues in gastrodermis Gastrodermis- the inner layer of cells that serves as a lining membrane of the gastrovascular cavity Respiration and Excretion Diffusion Nervous system Nerve net - consists of interconnected neurons lacking a brain or any form of cephalization. Respond to local stimuli Locomotion Float/ drift/propulsion Hydrostatic skeleton/ muscles Somersault Glide Walk on tentacles Osmoregulation Marine forms- isotonic Freshwater forms- must get rid of excess water (usually by contractile vacuoles) NO CILRCULATORY SYSTEM Cnidocytes Specialized cells for protection, locomotion, attachment. Located on epidermis Nematocyst (stinging version of a cnidocytes) Ecological and Economical importance Reefs Stings- painful but most not life threatening Possible pharmaceutical uses (treat multiple sclerosis) Some are edible Jewelry and ornaments (cultures) Coral (Anthozoa) (cultures) Form hard coral reefs Reefs provide habitat help reproduction for a number of species.
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4-8 million tons of commercial fish come from these reefs. Helps lower erosion on shores buffers crashing waves 2 types Polyp Medusa Polyp vs. medusa How do they differ structurally, reproductively, oral versus aboral? Polyp Fix (rarly free) attach to rocks (sessile- stationary) Aboral and oral end Hydranth- the terminal part of a hydroid polyp that bears the mouth and tentacles and contains the stomach region Oral disc- the more or less flattened upper or free end of the body bearing the mouth in its center and tentacles near or at its border in most polyps Tubular Velum is absent Sense organs absent
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Gonads absent Reproduces asexurally by budding Dioecious- Male and female members in a colony Medusa Free swimming Bell shape or umbrella Velum is present Mouth is in the center Mesoglea is thicker Mesoglea - non-living, jelly-like substance found between the two epithelial cell layers Statocyst is present at the base of eight tentacles balance sensory receptor Four gonads Reproduces sexurally Monoecious Class Hydrozoa Small Most marine, few freshwater Most colonial polyps (Colonial or solitary) Medusa stage usually has velum. ( velum- a membrane, typically bordering a cavity) Hydra- freshwater species with no medusa Asexual polyps and sexual medusae
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