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Animals Chapter 2 Sponges, Cnidarians, and Worms Sections 1 and 2 Definitions • Nerves – carry signals throughout the body • Ganglia – groups of nerves bundled together. Animals can have a brain and ganglia or just have ganglia depending on how advanced the animal is • Gut – pouch lined with digestive enzymes • Coelom – cavity that allows organs such as the gut, heart etc to work without interference from body movement Coelom Ganglion Symmetry Sponges • Phylum Porifera • 1st animals on earth Phylum Porifera • • • • Simplest of all animals Asymmetrical No head, nervous system, gut or coelom Spicules are needle-like splinters that make up the skeleton • If cells are separated, they can come back together • Both asexual and sexual reproduction Sponge Anatomy • Pores - used to pump water into sponge • Collar Cells – filters particles of food from water and digests them • Osculum – hole at the top of the sponge Anatomy of a Sponge Cnidarians • • • • Jellyfish Hydra Sea anenome corals Phylum Cnidaria • • • • • • • • Radial symmetry Complex tissues Gut Nerve net and nerve ring in medusa form If cells get separated, they come back together Tentacles – covered with nematocysts Nematocysts – stinging cells Sexual and asexual reproduction Body Forms • Medusa – free swimming, mushroom shaped • Polyp – vase shaped, attached to a surface • Most spend life as polyps but some are born polyps and turn into medusas Flatworms Platyhelmenthes • Planaria • Flukes • Tapeworms Characteristics • • • • • • Bilateral symmetry Nervous system Ganglia acts as a brain Sensory lobes to detect light and food Planaria have a gut Fluke and tapeworms are parasites and have no gut Reproduction of Fluke Reproduction of Tapeworms • Sexual • Can go from uncooked meat to human Roundworms - Nematoda Roundworm • Pseudocoelom – tube within a tube • Bilateral symmetry • Can pick up through the soles of feet, through dirty hands, through some foods Segmented Worms Annelida • Includes earthworms, bristle worms and leeches • Can live in water or on land Earthworms, Bristle Worms, Leeches Earthworms – aerate soil (makes tunnels) to allow water and air in, break down organic matter into elements that can be used Bristle Worms – all live in water Leeches – can be scavengers, predators or parasites, and can be used in medicine Next… • Earthworm dissection • Earthworm questions powerpoint Mollusks • Phylum Mollusca • Soft bodied usually with a shell or shells • Three classes: • Gastropods – snails and slugs • Bivalves – 2 shells- clams, mussels, etc. • Cephalopods – squid and octopus Similarities Between Mollusks Feeding • Different depending on species: • Gastropods have a radula which is like a really rough tongue and scraps algae, leaves etc. • Bivalves filter feed • Cephalopods use tentacles to grab prey Circulatory System • Most mollusks have an open system • Open system - A simple heart pumps blood into sinuses • Cephalopods have a closed system • Closed system – blood is circulated through a closed loop Brains • Most mollusks have ganglia spread throughout their body • Cephalopods have a brain where all of the ganglia are connected Next • Squid Dissection
