chapter 18 the evolution of invertebrate diversitynapavalley.edu/people/briddell/documents/biol...
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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
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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?
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ANIMAL EVOLUTION AND DIVERSITY
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Animals are eukaryotic, multicellular heterotrophs that ingest their food
Animal cells lack cell walls
18.1 What is an animal?
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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
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18.1 What is an animal?
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Egg
Meiosis
1
Sperm
Adult
Haploid (n)
Diploid (2n)
Key
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Egg
Meiosis
1
2
Sperm
Zygote(fertilizedegg)
Haploid (n)
Diploid (2n)
Key
Adult
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Egg
Meiosis
1
3
2
Sperm
Zygote(fertilizedegg)
Eight-cellstageAdult
Haploid (n)
Diploid (2n)
Key
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Egg
Meiosis
1
4
3
2
Sperm
Zygote(fertilizedegg)
Eight-cellstageAdult
Blastula(crosssection)
Haploid (n)
Diploid (2n)
Key
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Egg
Meiosis
1
5
4
3
2
Sperm
Zygote(fertilizedegg)
Eight-cellstageAdult
Blastula(crosssection)
Early gastrula(cross section)
Haploid (n)
Diploid (2n)
Key
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Egg
Meiosis
1
6
5
4
3
2
Sperm
Zygote(fertilizedegg)
Eight-cellstageAdult
Blastula(crosssection)
Ectoderm
Endoderm
Internal sac
Later gastrula(cross section)
Future mesoderm
Early gastrula(cross section)
Haploid (n)
Diploid (2n)
Key
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Egg
Meiosis
1
7
6
5
4
3
2
Sperm
Zygote(fertilizedegg)
Eight-cellstageAdult
Blastula(crosssection)Digestive
tract
LarvaEctoderm
Endoderm
Internal sac
Later gastrula(cross section)
Future mesoderm
Early gastrula(cross section)
Haploid (n)
Diploid (2n)
Key
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Egg
Meiosis
1
8
7
6
5
4
3
2
Sperm
Zygote(fertilizedegg)
Eight-cellstageAdult
Metamorphosis
Blastula(crosssection)Digestive
tract
LarvaEctoderm
Endoderm
Internal sac
Later gastrula(cross section)
Future mesoderm
Early gastrula(cross section)
Haploid (n)
Diploid (2n)
Key
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1 2 3 4 5Colonial protist,an aggregateof identical cells
Hollow sphereof unspecial-ized cells
Reproductive cells
Beginning of cellspecialization
Infolding Gastrula-like“proto-animal”
Somaticcells
Digestivecavity
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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
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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
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18.2 The ancestor of animals was probably a colonial, flagellated protist
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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”
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Top
Bottom
Anteriorend
Dorsal surface
Ventral surface
Posteriorend
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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
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18.3 Animals can be characterized by basic features of their “body plan”
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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
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18.3 Animals can be characterized by basic features of their “body plan”
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Digestive sac
(from endoderm)
Body covering
(from ectoderm)
Tissue-filled region
(from mesoderm)
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Body covering
(from ectoderm)
Muscle layer(from mesoderm)
Digestive tract
(from endoderm)
Pseudocoelom
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Coelom
Digestive tract(from endoderm)
Body covering
(from ectoderm)
Tissue layerlining coelomand suspendinginternal organs
(from mesoderm)
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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
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Ancestral
colonialprotist
No truetissues
Radialsymmetry
Truetissues
Bilateralsymmetry
Eu
me
tazo
an
s Bila
teria
ns
Pro
tos
tom
es
De
ute
ros
tom
es
Sponges
Cnidarians
Echinoderms
Chordates
Flatworms
Molluscs
Annelids
Arthropods
Nematodes
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INVERTEBRATE DIVERSITY
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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
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Pores
Amoebocyte
Skeletalfiber
Centralcavity
Choanocytein contact
with anamoebocyte
Flagella
Waterflow
Choanocyte
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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
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18.5 Sponges have a relatively simple, porous body
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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
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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
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18.6 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
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Tentacle
Prey
“Trigger”
Dischargeof thread
Cnidocyte
Coiled
thread
Capsule(nematocyst)
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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
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Gastrovascularcavity
Mouth
Nerve cords
Eyespots
Nervoustissueclusters
Bilateral symmetry
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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
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18.7 Flatworms are the simplest bilateral animals
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Units withreproductivestructures
Scolex(anteriorend)
Hooks
Sucker
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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
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Video: C. elegans Embryo Development (time lapse)
Video: C. elegans Crawling
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Mouth
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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
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Visceral mass
Coelom
Kidney
Mantle
Mantle
cavity
Anus
Heart
Gill
Foot Nervecords
Mouth
Radula
Shell
Digestivetract
Reproductiveorgans
Radula
Digestive tract
Mouth
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Anus
Mouth
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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
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18.9 Diverse molluscs are variations on a common body plan
Video: Nudibranchs
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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
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18.9 Diverse molluscs are variations on a common body plan
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Eyes
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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
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18.9 Diverse molluscs are variations on a common body plan
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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
18.10 Annelids are segmented worms
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Video: Tubeworms Video: Earthworm Locomotion
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Anus
Segmentwall
Mucus-secretingorgan
Brain
Dorsalbloodvessel
CoelomDigestive
tract
Mouth
Pumpingsegmentalvessels
Nerve cord
Ventral blood vessel
Segmentwall
Excretoryorgan
Nerve cord
BristlesIntestine
Dorsalblood vessel
Longitudinalmuscle
Ventral blood vessel
Bristles
Excretoryorgan
Circularmuscle
Epidermis
Segment wall(partitionbetweensegments)
GiantAustralianearthworm
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Anus
Segmentwall
Mucus-secreting
organ
Brain
Dorsalblood
vesselCoelom
Digestivetract
Mouth
Pumping segmental vessels
Nerve cord
Ventral blood vessel
Segmentwall
Excretoryorgan
Bristles
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Epidermis
Circularmuscle
Longitudinalmuscle
Dorsalbloodvessel
Intestine
Nerve cord
Segment wall(partition betweensegments)
Excretoryorgan
Bristles
Ventral blood vessel
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Giant Australian earthworm
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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
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18.10 Annelids are segmented worms
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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
18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton
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Video: Lobster Mouth Parts
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Cephalothorax Abdomen
Head Thorax
Antennae(sensoryreception)
Swimmingappendages
Pincer (defense) Mouthparts (feeding)
Walking legs
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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
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18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton
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A scorpion
(about 8 cm long)
A black widowspider (about1 cm wide)
A dust mite(about 420 mlong)
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A scorpion (about 8 cm long)
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A black widow spider (about 1 cm wide)
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A dust mite (about 420 m long)
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Millipedes and centipedes are identified by the number of jointed legs per body segment
– 2 in herbivorous millipedes, 1 in carnivorous centipedes
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18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton
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Crustaceans are nearly all aquatic
– They include crabs, shrimps, and barnacles, which feed with jointed appendages
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18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton
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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
18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals
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Head Thorax Abdomen
Antenna Forewing
Eye
Mouthparts Hindwing
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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
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18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals
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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
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18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals
Video: Butterfly Emerging
Video: Bee Pollinating
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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
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18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals
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Protective color patterns
– Many insects have protective color patterns and disguises, including modifications to antennae, wings, and bodies
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18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals
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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
18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement
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18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement
Video: Echinoderm Tube Feet
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Anus
Spines
Stomach
Canals
Tube feet
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Tube foot
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Spines
Tubefeet
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Chordates (phylum Chordata) have
– A dorsal hollow nerve cord
– A flexible, supportive notochord
– Pharyngeal slits
– A muscular post-anal tail
18.14 Our own phylum, Chordata, is distinguished by four features
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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
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18.14 Our own phylum, Chordata, is distinguished by four features
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Excurrentsiphon
Adult
(about 3 cm high)
Post-anal tail
Dorsal, hollow
nerve cord
Pharyngeal
slits
Mouth
Larva
Notochord
Muscle
segments
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Post-anal tail
Dorsal, hollownerve cord
Pharyngealslits
Mouth
Larva
Notochord
Musclesegments
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Mouth
Head
Pharynx
Pharyngeal
slits
Digestive tract
Water exit
Segmental
muscles
Anus
Notochord
Dorsal,
hollownerve cord
Post-anal
tail
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Head
Mouth
Pharynx
Pharyngeal
slits
Digestive tract
Water exit
Segmental
muscles
Anus
Notochord
Dorsal,hollownerve cord
Post-anal
tail
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ANIMAL PHYLOGENY AND DIVERSITY REVISITED
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This phylogenetic tree is based on molecular data
18.15 An animal phylogenetic tree is a work in progress
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Ancestral
colonialprotist
No truetissues
True
tissues
Radial
symmetry
Eu
meta
zo
an
s Bila
teria
nsBilateral
symmetry
Ecd
yso
zo
an
sL
op
ho
troch
ozo
an
sD
eu
tero
sto
mes
Sponges
Cnidarians
Echinoderms
Chordates
Flatworms
Molluscs
Annelids
Arthropods
Nematodes
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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.‖
18.16 TALKING ABOUT SCIENCE: Sean Carroll talks about the evolution of animal diversity
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Ancestral
colonialprotist
No truetissues
True
tissues
Radial
symmetry
Bilateral
symmetry
Eu
me
tazo
an
s
Bila
teria
ns
De
ute
ros
tom
es
Pro
tos
tom
es
Sponges
Cnidarians
Echinoderms
Chordates
Flatworms
Molluscs
Annelids
Arthropods
Nematodes
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No truetissues
Ancestral
colonialprotist
True
tissues
Radial
symmetry
Bilateral
symmetry
Eu
meta
zo
an
s Bila
teria
ns
Ecd
yso
zo
an
sL
op
ho
troc
ho
zo
an
sD
eu
tero
sto
me
s
Sponges
Cnidarians
Echinoderms
Chordates
Flatworms
Molluscs
Annelids
Arthropods
Nematodes
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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
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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
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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
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You should now be able to