Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Chapter 18 The Evolution of Invertebrate Diversity Lecture by Joan Sharp

 The mimic octopus can look like a highly venomous sea snake, a toxic flatfish, a sea anemone, or a jellyfish  Many animals have antipredator defenses such as mimicry, but only the mimic octopus can mimic multiple toxic animals Introduction: Fatal or Fake? Copyright © 2009 Pearson Education, Inc.

ANIMAL EVOLUTION AND DIVERSITY Copyright © 2009 Pearson Education, Inc.

 Animals are eukaryotic, multicellular heterotrophs that ingest their food  Animal cells lack cell walls 18.1 What is an animal? Copyright © 2009 Pearson Education, Inc.

Video: Sea Urchin Embryonic Development  Most adult animals are diploid, producing short- lived gametes by meiosis –Two gametes fuse to produce a diploid zygote, which grows to maturity by mitosis  The life cycle of most animals includes a blastula, gastrula, and larval stage  Hox genes control transformation of the zygote into an adult animal Copyright © 2009 Pearson Education, Inc What is an animal?

Egg Meiosis 1 Sperm Adult Haploid (n) Diploid (2n) Key

Egg Meiosis 1 2 Sperm Zygote (fertilized egg) Haploid (n) Diploid (2n) Key Adult

Egg Meiosis Sperm Zygote (fertilized egg) Eight-cell stage Adult Haploid (n) Diploid (2n) Key

Egg Meiosis Sperm Zygote (fertilized egg) Eight-cell stage Adult Blastula (cross section) Haploid (n) Diploid (2n) Key

Egg Meiosis Sperm Zygote (fertilized egg) Eight-cell stage Adult Blastula (cross section) Early gastrula (cross section) Haploid (n) Diploid (2n) Key

Egg Meiosis Sperm Zygote (fertilized egg) Eight-cell stage Adult Blastula (cross section) Ectoderm Endoderm Internal sac Later gastrula (cross section) Future mesoderm Early gastrula (cross section) Haploid (n) Diploid (2n) Key

Egg Meiosis Sperm Zygote (fertilized egg) Eight-cell stage Adult Blastula (cross section) Digestive tract Larva Ectoderm Endoderm Internal sac Later gastrula (cross section) Future mesoderm Early gastrula (cross section) Haploid (n) Diploid (2n) Key

Egg Meiosis Sperm Zygote (fertilized egg) Eight-cell stage Adult Metamorphosis Blastula (cross section) Digestive tract Larva Ectoderm Endoderm Internal sac Later gastrula (cross section) Future mesoderm Early gastrula (cross section) Haploid (n) Diploid (2n) Key

Colonial protist, an aggregate of identical cells Hollow sphere of unspecial- ized cells Reproductive cells Beginning of cell specialization Infolding Gastrula-like “proto-animal” Somatic cells Digestive cavity

 542 million years ago, an adaptive radiation known as the Cambrian explosion produced a varied and complex animal fauna  Many animal plans and new phyla appeared in a short time span 18.2 The ancestor of animals was probably a colonial, flagellated protist Copyright © 2009 Pearson Education, Inc.

 What explains the Cambrian explosion? –Ecological causes: The evolution of hard body coverings led to increasingly complex predator-prey relationships and diverse adaptations for feeding, motility, and protection –Geological causes: Atmospheric oxygen reached a high enough concentration to support the metabolism of more active, mobile animals –Genetic causes: The genetic framework for complex bodies was already in place in the Hox complex of regulatory genes; variation in these genes produced animal diversity Copyright © 2009 Pearson Education, Inc The ancestor of animals was probably a colonial, flagellated protist

 Animal body plans vary in symmetry, body cavity, and number of germ layers  With radial symmetry, any slice through the central axis divides the animal into mirror image halves –A radially symmetrical animal has a top and bottom but lacks back and front or right and left sides –Animals with bilateral symmetry have mirror-image right and left sides, a distinct head and tail, and a back (dorsal) and belly (ventral) surface 18.3 Animals can be characterized by basic features of their “body plan” Copyright © 2009 Pearson Education, Inc.

Top Bottom Anterior end Dorsal surface Ventral surface Posterior end

 Animal body plans vary in organization of tissues –Sponges lack true tissues –In other animals, cell layers formed during gastrulation give rise to tissues and organs –Some animals have only ectoderm and endoderm, but most animals also have mesoderm Copyright © 2009 Pearson Education, Inc Animals can be characterized by basic features of their “body plan”

 The body cavities of animals vary –Flatworms have a solid body and lack a coelom –A pseudocoelom is partially lined by tissue derived from mesoderm –A true coelom is completely lined by tissue derived from mesoderm Copyright © 2009 Pearson Education, Inc Animals can be characterized by basic features of their “body plan”

Digestive sac (from endoderm) Body covering (from ectoderm) Tissue-filled region (from mesoderm)

Body covering (from ectoderm) Muscle layer (from mesoderm) Digestive tract (from endoderm) Pseudocoelom

Coelom Digestive tract (from endoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm)

 A phylogenetic tree is a hypothesis for the evolutionary history of the groups involved  This phylogenetic tree is based on comparative morphology of animal taxa 18.4 The body plans of animals can be used to build phylogenetic trees Copyright © 2009 Pearson Education, Inc.

Ancestral colonial protist No true tissues Radial symmetry True tissues Bilateral symmetry Eumetazoans Bilaterians Protostomes Deuterostomes Sponges Cnidarians Echinoderms Chordates Flatworms Molluscs Annelids Arthropods Nematodes

INVERTEBRATE DIVERSITY Copyright © 2009 Pearson Education, Inc.

 Sponges (phylum Porifera) are simple, sedentary animals without true tissues –Water is drawn in through pores in the body wall into a central cavity, and then flows out through a larger opening  The body of a sponge consists of two layers of cells separated by a gelatinous region –The inner layer of flagellated choanocytes filters food and engulfs it by phagocytosis –Amoebocytes wander through the middle body region and produce skeletal fibers 18.5 Sponges have a relatively simple, porous body Copyright © 2009 Pearson Education, Inc.

Pores Amoebocyte Skeletal fiber Central cavity Choanocyte in contact with an amoebocyte Flagella Water flow Choanocyte

 Sponges are suspension feeders, filtering food particles from water passed through food-trapping equipment –To grow by 100 g, a sponge must filter 1,000 kg of water  Adult sponges are sessile and cannot escape from predators –They produce defensive toxins and antibiotics that deter pathogens, parasites, and predators Copyright © 2009 Pearson Education, Inc Sponges have a relatively simple, porous body

 Cnidarians (phylum Cnidaria) have two tissue layers: an outer epidermis and an inner cell layer lining the digestive cavity –A jelly-filled middle region may have scattered amoeboid cells  Cnidarians use tentacles to capture prey and push them into their mouths –The mouth leads to the gastrovascular cavity, which functions in digestion and circulation and as a hydrostatic skeleton –Cnidocytes on tentacles sting prey and function in defense 18.6 Cnidarians are radial animals with tentacles and stinging cells Copyright © 2009 Pearson Education, Inc.

 Cnidarians have two kinds of radially symmetrical body forms—polyp and medusa –Some cnidarians have alternating polyp and medusa forms in their life cycle, while others exist only as polyp or medusa forms Copyright © 2009 Pearson Education, Inc Cnidarians are radial animals with tentacles and stinging cells Video: Hydra Releasing Sperm Video: Hydra Eating Daphnia (time lapse) Video: Hydra Budding Video: Jelly Swimming Video: Clownfish and Anemone Video: Thimble Jellies Video: Coral Reef

Tentacle Prey “Trigger” Discharge of thread Cnidocyte Coiled thread Capsule (nematocyst)

 Flatworms (phylum Platyhelminthes) are the simplest bilateral animals  There are three major groups of flatworms –Free-living flatworms (planarians) have heads with light-sensitive eyespots and flaps to detect chemicals –Dense clusters of nerve cells form a simple brain, and a pair of nerve cords runs the length of the body –Planarians have a branched gastrovascular cavity with a single opening 18.7 Flatworms are the simplest bilateral animals Copyright © 2009 Pearson Education, Inc.

Gastrovascular cavity Mouth Nerve cords Eyespots Nervous tissue clusters Bilateral symmetry

 Flukes and tapeworms are parasitic flatworms with complex life cycles  Flukes live as parasites, with suckers to attach to their hosts  Tapeworms inhabit the digestive tracts of vertebrates –They consist of a ribbon-like body with repeated units –The anterior scolex is armed with hooks and suckers for attachment, while posterior units are full of eggs and sperm –Tapeworms lack a digestive tract and absorb nutrients from the intestines of their hosts Copyright © 2009 Pearson Education, Inc Flatworms are the simplest bilateral animals

Units with reproductive structures Scolex (anterior end) Hooks Sucker

 Roundworms (phylum Nematoda) have bilateral symmetry and three tissue layers –They are abundant and diverse, with an estimated 500,000 species –The body cavity is a pseudocoelom, which functions to distribute nutrients and as a hydroskeleton –The complete digestive tract has a mouth and anus  Humans host at least 50 species of nematodes 18.8 Nematodes have a pseudocoelom and a complete digestive tract Copyright © 2009 Pearson Education, Inc. Video: C. elegans Embryo Development (time lapse) Video: C. elegans Crawling

Mouth

 Molluscs (phylum Mollusca) have a true coelom and a circulatory system  Many molluscs feed with a rasping radula, used to scrape up food  All molluscs have –A muscular foot that functions in locomotion –A visceral mass containing most of the internal organs –A mantle, which may secrete a shell that encloses the visceral mass 18.9 Diverse molluscs are variations on a common body plan Copyright © 2009 Pearson Education, Inc.

Visceral mass Coelom Kidney Mantle cavity Anus Heart Gill Foot Nerve cords Mouth Radula Shell Digestive tract Reproductive organs Radula Digestive tract Mouth

Anus Mouth

 Gastropods are the largest group of molluscs and include the snails and slugs –Most snails are protected by a single, spiral shell –In land snails, the lining of the mantle cavity functions as a lung –Slugs have lost their mantle and shell and have long colorful projections that function as gills Copyright © 2009 Pearson Education, Inc Diverse molluscs are variations on a common body plan Video: Nudibranchs

 Bivalves have shells divided into two halves that are hinged together –Bivalves include clams, oysters, mussels, and scallops –Most bivalves are sedentary suspension feeders, attached to the substrate by strong threads Copyright © 2009 Pearson Education, Inc Diverse molluscs are variations on a common body plan

Eyes

 Cephalopods are fast, agile predators and include squids and octopuses  Cephalopods have large brains and sophisticated sense organs, including complex image-focusing eyes  In most cephalopods, the shell is small and internal (squid) or missing (octopuses) –Squid are fast, streamlined predators that use a muscular siphon for jet propulsion –Octopuses live on the seafloor, where they creep about in search of food Copyright © 2009 Pearson Education, Inc Diverse molluscs are variations on a common body plan

 Annelids (phylum Annelida) have a closed circulatory system in which blood is enclosed in vessels –Their nervous system includes a simple brain and ventral nerve cord with cluster of nerve cells in each segment –The true coelom functions as hydrostatic skeleton  Earthworms ingest soil and extract nutrients, aerating soil and improving its texture Annelids are segmented worms Copyright © 2009 Pearson Education, Inc. Video: Tubeworms Video: Earthworm Locomotion

Anus Segment wall Mucus-secreting organ Brain Dorsal blood vessel Coelom Digestive tract Mouth Pumping segmental vessels Nerve cord Ventral blood vessel Segment wall Excretory organ Nerve cord Bristles Intestine Dorsal blood vessel Longitudinal muscle Ventral blood vessel Bristles Excretory organ Circular muscle Epidermis Segment wall (partition between segments) Giant Australian earthworm

Anus Segment wall Mucus-secreting organ Brain Dorsal blood vessel Coelom Digestive tract Mouth Pumping segmental vessels Nerve cord Ventral blood vessel Segment wall Excretory organ Bristles

Epidermis Circular muscle Longitudinal muscle Dorsal blood vessel Intestine Nerve cord Segment wall (partition between segments) Excretory organ Bristles Ventral blood vessel

Giant Australian earthworm

 Polychaetes are the largest group of annelids –Each polychaete segment has a pair of fleshy appendages with stiff bristles or chaetae –Polychaetes search for prey on the seafloor or live in tubes and filter food particles  Most leeches are free-living carnivores, but some suck blood –Blood-sucking leeches use razor-like jaws, secrete an anesthetic and an anticoagulant, and suck up to 10 times their own weight in blood Copyright © 2009 Pearson Education, Inc Annelids are segmented worms

 There are over a million species of arthropods (phylum Arthropoda), including crayfish, lobsters, crabs, barnacles, spiders, ticks, and insects  The diversity and success of arthropods are due to segmentation, a hard exoskeleton, and jointed appendages  Arthropods have an open circulatory system  The body of most arthropods includes a head, thorax, and abdomen Arthropods are segmented animals with jointed appendages and an exoskeleton Copyright © 2009 Pearson Education, Inc. Video: Lobster Mouth Parts

Cephalothorax Abdomen HeadThorax Antennae (sensory reception) Swimming appendages Pincer (defense) Mouthparts (feeding) Walking legs

 Living arthropods represent four major lineages  Chelicerates include horseshoe crabs and arachnids, such as spiders, scorpions, mites, and ticks  Most are terrestrial  Scorpions are nocturnal hunters, while spiders hunt or trap prey during the day Copyright © 2009 Pearson Education, Inc Arthropods are segmented animals with jointed appendages and an exoskeleton

A scorpion (about 8 cm long) A black widow spider (about 1 cm wide) A dust mite (about 420  m long)

A scorpion (about 8 cm long)

A black widow spider (about 1 cm wide)

A dust mite (about 420  m long)

 Millipedes and centipedes are identified by the number of jointed legs per body segment –2 in herbivorous millipedes, 1 in carnivorous centipedes Copyright © 2009 Pearson Education, Inc Arthropods are segmented animals with jointed appendages and an exoskeleton

 Crustaceans are nearly all aquatic –They include crabs, shrimps, and barnacles, which feed with jointed appendages Copyright © 2009 Pearson Education, Inc Arthropods are segmented animals with jointed appendages and an exoskeleton

 70% of all animal species are insects –There may be as many as 30 million insect species  The body of an insect includes a head, thorax, and abdomen; three sets of legs; and (in most insects) wings EVOLUTION CONNECTION: Insects are the most successful group of animals Copyright © 2009 Pearson Education, Inc.

Head Thorax Abdomen Antenna Forewing Eye Mouthparts Hindwing

 The success of insects is due to –Body segmentation –An exoskeleton –Jointed appendages –Flight –A waterproof cuticle –A complex life cycle with short generations and large numbers of offspring Copyright © 2009 Pearson Education, Inc EVOLUTION CONNECTION: Insects are the most successful group of animals

 Insect life cycles –Many insects undergo incomplete or complete metamorphosis, with different body forms specialized for different roles –Larval stage is specialized for eating and growing –Adult stage is specialized for reproduction and dispersal Copyright © 2009 Pearson Education, Inc EVOLUTION CONNECTION: Insects are the most successful group of animals Video: Butterfly Emerging Video: Bee Pollinating

 Modular body plan of insects –Homeotic genes act to modify the structure of insect segments and their appendages –Insect mouthparts are adapted for various types of feeding, such as chewing (grasshoppers), biting and tearing prey (mantids), lapping up fluids (houseflies), piercing and sucking fluids of plants (aphids) and animals (mosquitoes) –Insects have three pairs of legs, which are adapted for walking, jumping, grasping prey, digging in soil, or paddling on water –Most adult insects have one or two pairs of wings, allowing dispersal and escape from predators Copyright © 2009 Pearson Education, Inc EVOLUTION CONNECTION: Insects are the most successful group of animals

 Protective color patterns –Many insects have protective color patterns and disguises, including modifications to antennae, wings, and bodies Copyright © 2009 Pearson Education, Inc EVOLUTION CONNECTION: Insects are the most successful group of animals

 Echinoderms (phylum Echinodermata) include slow-moving or sessile radially symmetrical organisms such as sea stars and sea urchins –The water vascular system has water-filled canals branching into tube feet, which are used for respiration, feeding, and locomotion  Echinoderms have an endoskeleton of hard calcareous plates under a thin skin  Echinoderms and chordates belong to a clade of bilateral animals called deuterostomes Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement Copyright © 2009 Pearson Education, Inc.

18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement Video: Echinoderm Tube Feet

Anus Spines Stomach Canals Tube feet

Tube foot

Spines Tube feet

 Chordates (phylum Chordata) have –A dorsal hollow nerve cord –A flexible, supportive notochord –Pharyngeal slits –A muscular post-anal tail Our own phylum, Chordata, is distinguished by four features Copyright © 2009 Pearson Education, Inc.

 The simplest chordates are tunicates and lancelets, which use their pharyngeal slits for suspension feeding –Adult tunicates are stationary and attached, while the tunicate larva is a tadpole-like organism –Tunicates represent the deepest branch of the chordate lineage  Lancelets are small, bladelike chordates that live in marine sands –Lancelets are the closest living relatives of vertebrates Copyright © 2009 Pearson Education, Inc Our own phylum, Chordata, is distinguished by four features

Excurrent siphon Adult (about 3 cm high) Post-anal tail Dorsal, hollow nerve cord Pharyngeal slits Mouth Larva Notochord Muscle segments

Post-anal tail Dorsal, hollow nerve cord Pharyngeal slits Mouth Larva Notochord Muscle segments

Mouth Head Pharynx Pharyngeal slits Digestive tract Water exit Segmental muscles Anus Notochord Dorsal, hollow nerve cord Post-anal tail

Head Mouth Pharynx Pharyngeal slits Digestive tract Water exit Segmental muscles Anus Notochord Dorsal, hollow nerve cord Post-anal tail

ANIMAL PHYLOGENY AND DIVERSITY REVISITED Copyright © 2009 Pearson Education, Inc.

 This phylogenetic tree is based on molecular data An animal phylogenetic tree is a work in progress Copyright © 2009 Pearson Education, Inc.

Ancestral colonial protist No true tissues True tissues Radial symmetry Eumetazoans Bilaterians Bilateral symmetry Ecdysozoans Lophotrochozoans Deuterostomes Sponges Cnidarians Echinoderms Chordates Flatworms Molluscs Annelids Arthropods Nematodes

 Sean Carroll, a pioneer in the new field of evolutionary developmental biology, has said: “The genes that build the bodies and body parts and organs of fruit flies are shared with us and with virtually every other animal in the kingdom.” TALKING ABOUT SCIENCE: Sean Carroll talks about the evolution of animal diversity Copyright © 2009 Pearson Education, Inc.

Ancestral colonial protist No true tissues True tissues Radial symmetry Bilateral symmetry Eumetazoans Bilaterians Deuterostomes Protostomes Sponges Cnidarians Echinoderms Chordates Flatworms Molluscs Annelids Arthropods Nematodes

No true tissues Ancestral colonial protist True tissues Radial symmetry Bilateral symmetry Eumetazoans Bilaterians Ecdysozoans Lophotrochozoans Deuterostomes Sponges Cnidarians Echinoderms Chordates Flatworms Molluscs Annelids Arthropods Nematodes

1.Describe the defining characteristics of animals 2.Describe the general animal life cycle and the basic body plan 3.Describe the Cambrian explosion and explain two hypotheses to explain its occurrence 4.Explain how a hydrostatic skeleton helps an animal move and keep its shape You should now be able to Copyright © 2009 Pearson Education, Inc.

5.Compare the nine animal phyla discussed in this chapter with respect to the following traits: (a) presence of true tissues; (b) no symmetry, radial symmetry, or bilateral symmetry; (c) no coelom, a pseudocoelom, or a true coelom; and (d) protostome or deuterostome 6.Define segmentation, explain its functions, and note the animal phyla where it occurs 7.Compare the characteristics of the four major arthropod lineages; note examples of each Copyright © 2009 Pearson Education, Inc. You should now be able to

8.Describe the common characteristics of insects 9.Describe the process and significance of complete metamorphosis 10.Compare the phylogenetic relationships shown in Figures 18.4 and 18.15, noting similarities and differences Copyright © 2009 Pearson Education, Inc. You should now be able to