Chapter 23 Animal Diversity I Invertebrates Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 23 At a Glance 23 1 What Are the Key Features of Animals 23 3 What Are the Major Animal Phyla Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 1 What Are the Key Features of Animals Animals possess all of the following characteristics Multicellularity Their cells lack a cell wall They obtain energy by consuming other organisms Most reproduce sexually They are motile at some point in the life cycle They are able to respond rapidly to external stimuli Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Animals probably originated from ancestral Present day biologists recognize about 27 phyla colonial protists of animals Most animals are invertebrates lack a vertebral column Less than 3 of all known animals are vertebrates possess a vertebral column Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Sponges have a simple body plan Sponges belong to the phylum Porifera and are found in most marine and aquatic environments Sponges do not move but occur in a variety of sizes and shapes They may reproduce asexually by budding where the adult produces miniature versions of itself that drop off and assume an independent existence They may reproduce sexually through fusion of sperm and eggs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Sponges lack true tissues and organs The sponge body is perforated by tiny pores through which water passes and by fewer large openings through which water is expelled As water passes through the sponge oxygen is extracted and microorganisms are filtered out and digested by individual cells Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Sponge cells are specialized for different functions Epithelial cells are flat cells that cover the outer body surface Pore cells are modified epithelial cells that regulate the flow of water through pores Collar cells are flagellated cells that maintain water flow through the sponge Amoeboid cells are motile cells that digest and distribute nutrients produce reproductive cells and secrete skeletal projections called spicules Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Some sponges contain chemicals useful to humans A number of chemicals within sponges have proved to be valuable medicines The drug spongistatin is an emerging treatment for the fungal infections that sicken AIDS patients Some medicines derived from sponges include some promising new cancer drugs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Cnidarians are well armed predators Sea jellies sea anemones corals and hydrozoans belong to the phylum Cnidaria These animals are mostly marine and are all carnivorous predators The cells of cnidarians are arranged into distinct tissues including a contractile muscle like tissue and an organized nerve net Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Cnidarians are well armed predators continued The nerve net of cnidarians branches throughout the body and controls the contractile tissue to bring about movement and feeding behavior Most cnidarians lack true organs and have no brain Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Cnidarians have two body plans the polyp and the medusa Many species have life cycles that include both body plans Polyps and medusae develop from two germ layers the endoderm and the ectoderm with a jelly like substance between the layers The polyp is attached to rocks while the medusa floats in the water both have tentacles with cnidocytes specialized cells that function in defense and the capture of prey Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Cnidarians have stinging cells called cnidocytes that are used to capture prey and for defense Cnidocytes contain a finely coiled filament that is explosively expelled when the trigger is touched Some filaments inject poison into the prey Others either stick to or entangle small prey The venom of some can cause extreme pain or death in humans Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Comb jellies belong to the phylum Ctenophora These animals resemble some cnidarians but form instead a distinct evolutionary lineage The comb jellies use cilia to move All comb jellies are carnivorous eating tiny invertebrate animals that they capture with sticky tentacles Most comb jellies are hermaphroditic and can release both eggs and sperm into seawater fertilized eggs gradually develop into larvae and then adults Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Flatworms may be parasitic or free living Flatworms are bilaterally symmetrical and belong to the phylum Platyhelminthes Many species are parasites organisms that live in or on the body of another organism Non parasitic free living flatworms inhabit aquatic marine and moist terrestrial habitats Flatworms can reproduce both sexually and asexually most are hermaphroditic having both male and female sexual organs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Flatworms have organs but lack respiratory and circulatory systems They possess a distinct head along with sensory organs The eyespots of freshwater planarians detect light and dark Their nervous system consist of clusters of nerve cells called ganglia singular ganglion bundle of nerves in the head forming a simple brain They have paired nerve chords that extend the length of the body and conduct nerve signals to and from the ganglia Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What Are the Major Animal Phyla Flatworms are bilaterally symmetrical rather than radially symmetrical This body plan is accompanied by cephalization where sense organs are concentrated in the anterior portion of the body This enhances an animal s ability to respond appropriately to any stimuli that it encounters Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 23 3 What
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