The Evolution of Animal Diversity Dr. Stephen J. Salek Biology 130 Fayetteville State University
Create your own animal? Start with a basic plant. Make the plant into a simple animal such as a worm. Consider: Body form, cell types, feeding, reproduction, movement, lifespan, size, growth, development
What is an animal? Multicellular, ingestive heterotrophs without cell walls Many have flagella and cilia Have unique intercellular junctions Digestion in an internal space or tract Dominant diploid phase Unique embryonic phases sometimes including larva
Animal Phyla Phyla Porifora Cnidaria Platyhelminthes Nematoda Annelida Arthropoda Mollusca Echinodermata Chordata Example Sponges Jellyfish Flatworms Roundworms Segmented worms Crabs, insects Snails, squid, clams Starfish, sand dollars Mammals, birds etc.
Some animals alternate generations Diploid adult is dominant Sperm or eggs produced by meiosis Campbell 18.1
Development and Evolution Campbell 18.2 Animals go through stages of development Zygote - blastula - gastrula- larvae
Animals Digest food inside multicellular bodies Composed of diploid cells except gametes
Animals evolved from Choanoflagellate Ancestors Campbell Fig. 18.3 D nucleic acids match large colonies of choanoflagellates, turned outside-in, would resemble sponges small choanoflagellate colony
Porifera Sponges, the Simplest Animal Design
Choanocyte of a Sponge Campbell 18.3C Sponges are simple multicellular animals Have porous bodies Filter feed using chonaocytes and phagocytosis
Main Cell Types Campbell 18.3C Choanocytescreate water flow and trap food Amoebocytes- pick up food, digest it, carry it to other cells
Sponges exhibit radial symmetry Radial symmetry- Mirror images around a central axis Campbell 18.3B
Other Sponge Body Forms
Spicules mineral needles may be calcium carbonate or silica (glass) for skeletal support and defense
Phylum Cnidaria Radially symmetrical animals that sting
Cnidarians Major Characteristics Radial symmetry Have two body types and a larval form Polyp, medusa, and planula body forms Two tissue layers epidermis and gastrodermis, Incomplete gut - gastrovascular cavity Cnidocytes - stinging cells
Two Types of Bodies Campbell Fig. 18.4 A-C polyp (attached, mouth-up) medusa (free-drifting, mouth-down)
Tissue layers and gastrovascular cavity food in gastrovascular cavity epidermis gastrodermis cnidocytes
Cnidocyte Campbell Fig. 18.4 D nucleus cnidocil or trigger
Pop Quiz List 3 distinguishing characteristics of the following two animal phya A) Porifera B) Cnidaria
Phylum Platyhelminthes Flatworms - the Simplest Bilateral Animals
Bilateral Body Design cephalized sensory organs concentrated in head body directions:
Simplest Bilateral Animals Move through environment headfirst not drifting like radial symmetric animals Gastrovascular cavity Free living, parasitic flukes, tapeworms Campbell 18.6A
adults (unusual because diecious) eggs Schistosome Fluke Life Cycle Campbell Fig. 18.6B cercaria miracidium sporocyst reproduces asexually
Tapeworm Adult Anatomy compare Campbell 18.6 Scolex -anchors worm, buds asexually Gravid Proglottids - break off and release eggs testes uterus ovaries gonopore Proglottid - reproduces sexually
acoelomate pseudocoelomate (muscles, not peritoneum) eucoelomate peritoneum Eucoelomate Body Design compare Campbell Fig. 18.7C ectoderm mesoderm endoderm Coelom: fluid-filled cavity between gut and body wall that is lined with mesodermal cells (peritoneum).
Most animals have a body cavity Solid, no body cavity except for gastro vascular cavity flatworms, cnidaria Pseudocoelomateinternal space in contact with digestive tract, roundworms True coelom - internal space lined by tissue - all other animals