Chapter 18. The Evolution of Invertebrate Diversity. Lecture by Joan Sharp

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

2 Introduction: Fatal or Fake? 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 Copyright 2009 Pearson Education, Inc.

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

8 18.1 What is an animal? Animals are eukaryotic, multicellular heterotrophs that ingest their food Animal cells lack cell walls Copyright 2009 Pearson Education, Inc.

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10 18.1 What is an animal? Most adult animals are diploid, producing shortlived 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 Video: Sea Urchin Embryonic Development Copyright 2009 Pearson Education, Inc.

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

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

13 Egg Sperm 2 1 Key Haploid (n) Meiosis Zygote (fertilized egg) 3 Diploid (2n) Adult Eight-cell stage

14 Egg Sperm 2 1 Key Haploid (n) Meiosis Zygote (fertilized egg) 3 Diploid (2n) Adult Eight-cell stage Blastula (cross section) 4

15 Egg Sperm 2 1 Key Haploid (n) Meiosis Zygote (fertilized egg) 3 Diploid (2n) Adult Eight-cell stage Blastula (cross section) 4 5 Early gastrula (cross section)

16 Egg Sperm 2 1 Key Haploid (n) Meiosis Zygote (fertilized egg) 3 Diploid (2n) Adult Eight-cell stage Blastula (cross section) 4 Ectoderm 5 Endoderm Internal sac Later gastrula (cross section) 6 Early gastrula (cross section) Future mesoderm

17 Egg Sperm 2 1 Key Haploid (n) Meiosis Zygote (fertilized egg) 3 Diploid (2n) Adult Eight-cell stage Digestive tract Blastula (cross section) 4 Larva Ectoderm 5 7 Endoderm Internal sac Later gastrula (cross section) 6 Early gastrula (cross section) Future mesoderm

18 Egg Sperm 2 1 Key Haploid (n) Meiosis Zygote (fertilized egg) 3 Diploid (2n) 8 Adult Eight-cell stage Metamorphosis Digestive tract Blastula (cross section) 4 Larva Ectoderm 5 7 Endoderm Internal sac Later gastrula (cross section) 6 Early gastrula (cross section) Future mesoderm

19 Somatic cells Digestive cavity Reproductive cells Colonial protist, an aggregate of identical cells Hollow sphere of unspecialized cells Beginning of cell specialization Infolding Gastrula-like proto-animal

20 18.2 The ancestor of animals was probably a colonial, flagellated protist 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 Copyright 2009 Pearson Education, Inc.

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22 18.2 The ancestor of animals was probably a colonial, flagellated protist 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.

23 18.3 Animals can be characterized by basic features of their body plan 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 Copyright 2009 Pearson Education, Inc.

24 Top Dorsal surface Anterior end Posterior end Bottom Ventral surface

25 18.3 Animals can be characterized by basic features of their body plan 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.

26 18.3 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.

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

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

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

30 18.4 The body plans of animals can be used to build phylogenetic trees 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 Copyright 2009 Pearson Education, Inc.

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

32 INVERTEBRATE DIVERSITY Copyright 2009 Pearson Education, Inc.

33 18.5 Sponges have a relatively simple, porous body 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 Copyright 2009 Pearson Education, Inc.

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

38 18.5 Sponges have a relatively simple, porous body 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.

39 18.6 Cnidarians are radial animals with tentacles and stinging cells 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 Copyright 2009 Pearson Education, Inc.

40 18.6 Cnidarians are radial animals with tentacles and stinging cells 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 Video: Hydra Budding Video: Hydra Eating Daphnia (time lapse) Video: Thimble Jellies Video: Hydra Releasing Sperm Video: Clownfish and Anemone Video: Jelly Swimming Video: Coral Reef Copyright 2009 Pearson Education, Inc.

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

45 18.7 Flatworms are the simplest bilateral animals 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 Copyright 2009 Pearson Education, Inc.

46 Gastrovascular cavity Nerve cords Mouth Eyespots Nervous tissue clusters Bilateral symmetry

47 18.7 Flatworms are the simplest bilateral animals 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.

48 Units with reproductive structures Hooks Sucker Scolex (anterior end)

49 18.8 Nematodes have a pseudocoelom and a complete digestive tract 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 Video: C. elegans Crawling Video: C. elegans Embryo Development (time lapse) Copyright 2009 Pearson Education, Inc.

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52 18.9 Diverse molluscs are variations on a common body plan 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 Copyright 2009 Pearson Education, Inc.

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

54 Mouth Anus

55 18.9 Diverse molluscs are variations on a common body plan 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 Video: Nudibranchs Copyright 2009 Pearson Education, Inc.

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58 18.9 Diverse molluscs are variations on a common body plan 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.

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61 18.9 Diverse molluscs are variations on a common body plan 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.

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63 18.10 Annelids are segmented worms 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 Video: Tubeworms Video: Earthworm Locomotion Copyright 2009 Pearson Education, Inc.

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

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

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

67 Giant Australian earthworm

68 18.10 Annelids are segmented worms 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.

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72 18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton 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 Video: Lobster Mouth Parts Copyright 2009 Pearson Education, Inc.

73 Cephalothorax Abdomen Head Thorax Antennae (sensory reception) Swimming appendages Walking legs Pincer (defense) Mouthparts (feeding)

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75 18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton 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.

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

77 A scorpion (about 8 cm long)

78 A black widow spider (about 1 cm wide)

79 A dust mite (about 420 m long)

80 18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton 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.

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83 18.11 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.

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85 18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals 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 Copyright 2009 Pearson Education, Inc.

86 Head Thorax Abdomen Antenna Forewing Eye Mouthparts Hindwing

87 18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals 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.

88 18.12 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 Video: Butterfly Emerging Video: Bee Pollinating Copyright 2009 Pearson Education, Inc.

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93 18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals 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.

94 18.12 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.

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103 18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement 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 Copyright 2009 Pearson Education, Inc.

104 18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement Video: Echinoderm Tube Feet Copyright 2009 Pearson Education, Inc.

105 Anus Spines Stomach Tube feet Canals

106 Tube foot

107 Tube feet Spines

108 18.14 Our own phylum, Chordata, is distinguished by four features Chordates (phylum Chordata) have A dorsal hollow nerve cord A flexible, supportive notochord Pharyngeal slits A muscular post-anal tail Copyright 2009 Pearson Education, Inc.

109 18.14 Our own phylum, Chordata, is distinguished by four features 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.

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

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

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

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

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

115 18.15 An animal phylogenetic tree is a work in progress This phylogenetic tree is based on molecular data Copyright 2009 Pearson Education, Inc.

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

117 18.16 TALKING ABOUT SCIENCE: Sean Carroll talks about the evolution of animal diversity 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. Copyright 2009 Pearson Education, Inc.

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

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

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122 You should now be able to 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 Copyright 2009 Pearson Education, Inc.

123 You should now be able to 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.

124 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.