Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 18 The Evolution of Animal Diversity

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings What Am I? Of some 1.5 million species of organisms known to science –Over two-thirds are animals Humans have a long history of studying animal diversity –But classifying an animal isn’t always easy

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Imagine you were the first person to encounter the animal pictured here –With all of its varying characteristics, what would you think it is?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Biologists often encounter classification problems –When evolution creates organisms with similar characteristics A Tasmanian tiger, 1928

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ANIMAL EVOLUTION AND DIVERSITY 18.1 What is an animal? Animals are eukaryotic, multicellular heterotrophs –That ingest their food Figure 18.1A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Animal development –May include a blastula, gastrula, and lar val stage Key Meiosis Metamorphosis Haploid (n) Diploid (2n) Sperm Egg Zygote (fertilized egg) Adult Blastula (cross section) Eight-cell stage Digestive tract Ectoderm Larva Early gastrula (cross section) Future mesoderm Later gastrula (cross section) Internal sac Endoderm Figure 18.1B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Reproductive cells Somatic cells Digestive cavity 1 Colonial protist, an aggregate of identical cells 2 Hollow sphere of unspecialized cells (shown in cross section) 3 Beginning of cell specialization (cross section) 4 Infolding (cross section) 5 Gastrula-like “proto-animal” (cross section) 18.2 The ancestor of animals was probably a colonial, flagellated protist Cells in these protists –Gradually became more specialized and layered Figure 18.2A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Animal diversity –Exploded during the Cambrian period Figure 18.2B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.3 Animals can be characterized by basic features of their “body plan” Animal body plans –May vary in symmetr y Top Bottom Dorsal surface Anterior end Posterior end Ventral surface Figure 18.3A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Body covering (from ectoderm) Tissue-filled region (from mesoderm) Digestive tract (from endoderm) Body covering (from ectoderm) Muscle layer (from mesoderm) Digestive tract (from endoderm) Pseudocoelom Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Coelom Digestive tract (from endoderm) Figure 18.3B–D –Vary in body cavity

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Development as either protostomes or deuterostomes

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.4 The body plans of animals can be used to build phylogenetic trees One hypothesis of animal phylogeny –Is based on morphological comparisons Ancestral colonial protist No true tissuesTrue tissues Bilateral symmetry Radial symmetry Eumetazoans Bilaterians Protostomes Deuterostomes Sponges Cnidarians Echinoderms Chordates Flatworms MolluscsAnnelids Arthropods Nematodes Figure 18.4

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.5 Sponges have a relatively simple, porous body Sponges, phylum Porifera –Are the simplest animals and have no true tissues INVERTEBRATES Figure 18.5A–C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Pores Amoebocyte Skeletal fiber Central cavity Choanocyte in contact with an amoebocyte Choanocyte Water flow Flagella Figure 18.5D Flagellated choanocytes –Filter food from the water passing through the porous body

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.6 Cnidarians are radial animals with tentacles and stinging cells Cnidarians, phylum Cnidaria –Have true tissues and radial symmetry

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Their two body forms are –Polyps, such as hydra –Medusae, the jellies Figure 18.6A–C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings They have a gastrovascular cavity –And cnidocytes on tentacles that sting prey Tentacle “Trigger” Coiled thread Capsule (nematocyst) Discharge of thread Cnidocyte Prey Figure 18.6D

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.7 Flatworms are the simplest bilateral animals Flatworms, phylum Platyhelminthes –Are bilateral animals with no body cavity

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A planarian has a gastrovascular cavity –And a simple ner vous system Bilateral symmetry Gastrovascular cavity Nerve cords Mouth Eyespots Nervous tissue clusters Figure 18.7A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Flukes and tapeworms –Are parasitic flatworms with complex life cycles Units with reproductive structures Scolex (anterior end) Hooks Sucker Colorized SEM 80  Figure 18.7B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.8 Nematodes have a pseudocoelom and a complete digestive tract Nematodes, phylum Nematoda –Have a pseudocoelom and a complete digestive tract –Are covered by a protective cuticle

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Many nematodes are free-living –And others are plant or animal parasites Trichinella juvenile LM 350  Muscle tissue Colorized SEM 400  Mouth Figure18.8A, B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.9 Diverse molluscs are variations on a common body plan All molluscs have a muscular foot and a mantle –Which may secrete a shell that encloses the visceral mass Many mollusks –Feed with a rasping radula Visceral mass Mantle Radula Mouth Nerve cords Foot Mouth Radula Digestive tract Shell Digestive tract Reproductive organs Heart Coelom Kidney Mantle cavity Anus Gill Figure 18.9A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Gastropods Gastropods are the largest group of molluscs –And include the snails and slugs Figure 18.9B, C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Bivalves The bivalves have shells divided into two halves –And include clams, oysters, mussels, and scallops Figure 18.9D

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Cephalopods Cephalopods are adapted to be agile predators –And include squids and octopuses Figure 18.9E, F

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Annelids are segmented worms The segmented bodies of phylum Annelida –Give them added mobility for swimming and burrowing

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ear thworms and Their Relatives Ear thworms –Eat their way through soil –Have a closed circulatory system Giant Australian earthworm Mouth Brain Dorsal vessel Coelom Digestive tract Mucus-secreting organ Segment wall Anus Bristles Segment wall Blood vessels Nerve cord Pumping segmental vessels Nerve cord Ventral vessel Bristles Excretory organ Segment wall (partition between segments) Epidermis Circular muscle Longitudinal muscle Dorsal vessel Intestine Excretory organ Figure 18.10A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Polychaetes The polychaetes –Form the largest group of annelids –Search for prey on the seafloor or live in tubes and filter food par ticles Figure 18.10B, C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Leeches Most leeches –Are free-living carnivores, but some suck blood Figurer 18.10D

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ar thropods are segmented animals with jointed appendages and an exoskeleton The diversity and success of ar thropods –Are largely related to their segmentation, exoskeleton, and jointed appendages Antennae (sensory reception) Head Thorax Cephalothorax Abdomen Swimming appendages Walking legs Mouthparts (feeding) Pincer (defense) Figure 18.11A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Chelicerates Chelicerates include –Horseshoe crabs –Arachnids, such as spiders, scorpions, mites, and ticks A scorpion (about 8 cm long) A black widow spider (about 1 cm wide) A dust mite (about 420 µm long) Colorized SEM 900  Figure 18.11B, C

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Millipedes and Centipedes Millipedes and centipedes –Are identified by the number of jointed legs per body segment Figure 18.11D

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Crustaceans The crustaceans –Are nearly all aquatic –Include crabs, shrimps, and barnacles Figure 18.11E