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Transcript of © 2010 Pearson Education, Inc. The Evolution of Animals The Origins of Animal Diversity Major...
© 2010 Pearson Education, Inc.
The Evolution of Animals
The Origins of Animal Diversity
Major invertebrate Phyla
Vertebrate Evolution and Diversity
The Human Ancestry
Figure 17.00
© 2010 Pearson Education, Inc.
– Some scientists think that these bones represent pygmies of a previously unknown human species, named Homo floresiensis.
– Other scientists suggest that the bones are from diseased Homo sapiens.
© 2010 Pearson Education, Inc.
THE ORIGINS OF ANIMAL DIVERSITY
– Animal life began in Precambrian seas with the evolution of multicellular creatures that ate other organisms.
© 2010 Pearson Education, Inc.
What Is an Animal?– Animals are:
• Eukaryotic
• Multicellular
• Heterotrophic organisms that obtain nutrients by ingestion
• Able to digest their food within their bodies
– Animal cells lack the cell walls that provide strong support in the bodies of plants and fungi.
© 2010 Pearson Education, Inc.
Figure 17.1
© 2010 Pearson Education, Inc.
– Most animals have:• Muscle cells • Nerve cells that control the muscles• Are diploid• Reproduce sexually• Proceed through a series of typically similar developmental
stages
MEIOSIS
Sperm
Egg
Adult
Key
FERTILIZATION
MITOSIS
Eight-cell stage
Internal sac
Digestive tract
Larva
METAMORPHOSIS
Haploid (n)
Diploid (2n)
Outer cell layer(ectoderm)
Later gastrula(cross section)
Future middlelayer of cells(mesoderm)
Inner cell layer(endoderm)
Early gastrula(cross section)
Blastula(cross section)
Zygote(fertilized egg)
Figure 17.2-8
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Early Animals and the Cambrian Explosion
– Animals probably evolved from a colonial flagellated protist that lived in Precambrian seas about 600–700 million years ago.
Reproductive cells
Digestivecavity
Figure 17.3-5
© 2010 Pearson Education, Inc.
– At the beginning of the Cambrian period, 542 million years ago, animals underwent a rapid diversification.
– During a span of about 15 million years:• All major animal body plans we see today evolved• Many of these animals seem bizarre
Figure 17.4
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– What ignited the Cambrian explosion?• One hypothesis emphasizes increasingly complex
predator-prey relationships that led to diverse adaptations to feed, move, and provide protection.
• Another hypothesis, studying evolution and development, called evo-devo, focuses on the evolution of genes that control the development of animal forms.
© 2010 Pearson Education, Inc.
Animal Phylogeny– Biologists categorize animals by:
• General features of body structure• More recently, using genetic data
– One major branch point distinguishes sponges from all other animals because, unlike more complex animals, sponges lack true tissues.
Ancestralprotist
No true tissues
Radial symmetry
Tissues
Bilateral symmetry
Sponges
Cnidarians
Molluscs
Flatworms
Annelids
Roundworms
Arthropods
Echinoderms
Chordates
Figure 17.5
© 2010 Pearson Education, Inc.
– A second major evolutionary split is based on body symmetry.
• Radial symmetry refers to animals that are identical all around a central axis.
• Bilateral symmetry exists where there is only one way to split the animal into equal halves.
Radial symmetry. Parts radiate from the center, so any slicethrough the central axis divides into mirror images.
Bilateral symmetry. Only one slice can divide left and rightsides into mirror-image halves.
Figure 17.6
© 2010 Pearson Education, Inc.
– Animals also vary according to the presence and type of body cavity, a fluid-filled space separating the digestive tract from the outer body wall.
– There are differences in how the body cavity forms.• If the body cavity is not completely lined by tissue derived from mesoderm, it is a pseudocoelom.• A true coelom is completely lined by tissue derived from mesoderm.
(a) No body cavity
(b) Pseudocoelom
(c) True coelom
Body covering(from ectoderm)
Tissue-filledregion (frommesoderm)
Body covering(from ectoderm)
Body covering(from ectoderm)
Musclelayer (frommesoderm)
Tissue layer liningcoelom andsuspendinginternal organs(from mesoderm)
Digestive tract(from endoderm)
Digestive tract(from endoderm)
Digestive tract(from endoderm)
Pseudocoelom
Coelom
Figure 17.7
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MAJOR INVERTEBRATE PHYLA– Invertebrates:
• Are animals without backbones• Represent 95% of the animal kingdom
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Sponges– Sponges represent multiple phyla.– Sponges include sessile animals that lack true tissues and that were once believed to be plants.– The body of a sponge resembles a sac perforated with holes.– Choanocyte cells draw water through the walls of the sponge where food is collected.
Choanocyte(feeding cell)
Waterflow
Skeletalfiber
Centralcavity
Choanocytein contactwith anamoebocyte
Amoebocyte
Flagella
Pores
Figure 17.8
© 2010 Pearson Education, Inc.
Cnidarians– Cnidarians (phylum Cnidaria) are characterized by:
• The presence of “true” body tissues • Radial symmetry • Tentacles with stinging cells
– The basic body plan of a cnidarian is a sac with a gastrovascular cavity, a central digestive compartment with only one opening.
– The body plan has two variations:
• The sessile polyp – not able to move about• The floating medusa – the “mobile stage”
– Cnidarians are carnivores that use tentacles, armed with cnidocytes (“stinging cells”), to capture prey.
Mouth/anus
Tentacle
Polyp form
Gastrovascularcavity
Coral Hydra
Sea anemone
Gastrovascularcavity
Mouth/anusTentacle
Medusa form
JellyFigure 17.9
Tentacle
Trigger
Capsule
Cnidocyte
Dischargeof thread
Prey
Coiledthread
Figure 17.10
© 2010 Pearson Education, Inc.
Molluscs– Molluscs (phylum Mollusca) are represented by soft-bodied animals,
usually protected by a hard shell.
– Many molluscs feed by using a file-like organ called a radula to scrape up food.
– The body of a mollusc has three main parts:
• A muscular foot used for movement
• A visceral mass housing most of the internal organs
• A mantle, which secretes the shell if present
– The three major groups of molluscs are:
• Gastropods, protected by a single, spiraled shell
• Bivalves, with a shell divided into two halves hinged together
• And cephalopods
– Typically lacking an external shell
– Built for speed and agility
Visceral mass
Reproductiveorgans
Digestivetract
Mantlecavity
Nervecords
Digestivetract
Coelom
Radula
Radula
Kidney Heart
Shell
Mouth
Mouth
Anus
Gill
Foot
Mantle
Figure 17.11
Gastropods
Snail (spiraled shell)
Sea slug (no shell)Figure 17.12a
Bivalves(hinged shell)
ScallopFigure 17.12b
Cephalopods(large brain and tentacles)
Octopus Squid
Figure 17.12c
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Flatworms– Flatworms (phylum Platyhelminthes) are the
simplest bilateral animals.– Have “true” tissues– Flatworms include forms that are:
• Parasites or• Free-living in marine, freshwater, or damp habitats
– The gastrovascular cavity of flatworms• Is highly branched • Provides an extensive surface area for absorption of
nutrients
Digestive tract(gastrovascularcavity)
Nerve cords
Mouth
Eyespots (detect light)
Nervous tissue clusters(simple brain)
Planarian
Bilateral symmetry
Figure 17.13a
© 2010 Pearson Education, Inc.
Annelids– Annelids (phylum Annelida) have:
• Body segmentation, a subdivision of the body along its length into a series of repeated parts
• A coelom• A complete digestive tract with
– Two openings, a mouth and anus– One-way movement of food
– The three main groups of annelids are:• Earthworms, which eat their way through soil• Polychaetes, marine worms with segmental
appendages for movement and gas exchange• Leeches, typically free-living carnivores but with
some bloodsucking forms
Mouth
Brain
Coelom
Nerve cord
Blood vesselsWaste disposal organ
Anus
Accessoryhearts
Mainheart
Digestivetract
Segmentwalls
Figure 17.15
Earthworms Polychaetes Leeches
MAJOR GROUPS OF ANNELIDS
Christmas tree wormGiant Australian earthworm European freshwater leech
Figure 17.14
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Roundworms– Roundworms (phylum Nematoda) are:
• Cylindrical in shape, tapered at both ends• The most diverse and widespread of all animals
– Roundworms (also called nematodes) are:• Important decomposers • Dangerous parasites in plants, humans, and other
animals
(a) A free-livingroundworm
(b) Parasiticroundworms in pork
(c) Canine heartInfected with parasiticroundworms
Figure 17.16
© 2010 Pearson Education, Inc.
Arthropods– Arthropods (phylum Arthropoda) are named for their
jointed appendages.– There are about one million arthropod species identified,
mostly insects.– Arthropods are a very diverse and successful group,
occurring in nearly all habitats in the biosphere.– There are four main groups of arthropods. Insects,
crustaceans, arachnids (spiders) and millipedes and centipedes
– Arthropods are segmented animals with specialized segments and appendages for an efficient division of labor among body regions. This allows for their great success as a phylum.
MAJOR GROUPS OF ARTHROPODS
Arachnids
Crustaceans
Millipedes and Centipedes
Insects
Figure 17.17
© 2010 Pearson Education, Inc.
– The body of arthropods is completely covered by an exoskeleton, an external skeleton that provides:
• Protection • Points of attachment for the muscles that move appendages
AbdomenCephalothorax
(head and thorax)
Swimmingappendage
Antenna(sensory reception)
Eyes onmovable stalks
Mouthparts (feeding)
Walking leg
Walking legs
Figure 17.18
an arthropod of the large, mainly aquatic group Crustacea, such as a crab, lobster, shrimp, or barnacle.
© 2010 Pearson Education, Inc.
– Arachnids:• Live on land• Usually have four pairs of walking legs and a
specialized pair of feeding appendages• Include spiders, scorpions, ticks, and mites
Arachnids
Two feedingappendages
Leg (four pairs)
Black widow spider Wood tick
Dust miteScorpion
Figure 17.19
© 2010 Pearson Education, Inc.
– Crustaceans:• Are nearly all aquatic
• Have multiple pairs of specialized appendages
• Include crabs, lobsters, crayfish, shrimps, and barnacles
Crustaceans
Two feedingappendages Leg (three or more pairs)
Antennae
BarnaclesCrayfish
Pill bugShrimp
Crab
Figure 17.20
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– Millipedes and centipedes have similar segments over most of the body.
– Millipedes:• Eat decaying plant matter • Have two pairs of short legs per body segment
– Centipedes:• Are terrestrial carnivores with poison claws • Have one pair of short legs per body segment
Millipedes and Centipedes
One pair of legs per segment
Two pairs of legsper segment
Millipede Centipede
Figure 17.21
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– Insects typically have a three-part body:• Head• Thorax• Abdomen
– The insect head usually bears:• A pair of sensory antennae • A pair of eyes
– The mouthparts are adapted for particular kinds of eating.
– Flight is one key to the great success of insects.
Insect Anatomy
Antenna
Head Thorax Abdomen
Eye
Mouthparts
Figure 17.22
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– Insects outnumber all other forms of life combined.
– Insects live in:• Almost every terrestrial habitat • Freshwater• The air
Insect Diversity
Banded OrangeHeliconian
PrayingmantisGiraffe weevil
Yellow jacket wasp Leaf beetle
Leaf roller
Peacock katydid
Longhorn beetleFigure 17.23
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– Many insects undergo metamorphosis in their development.– Young insects may:
• Appear to be smaller forms of the adult or• Change from a larval form to something much different as an adult
The larva (caterpillar) spendsits time eating and growing,molting as it grows.
After several molts, thelarva becomes a pupaencased in a cocoon.
Within the pupa, the larval organs breakdown and adult organs develop fromcells that were dormant in the larva.
Finally, the adult emergesfrom the cocoon.
The butterfly flies off and reproduces, nourished mainlyby calories stored when it was a caterpillar.
Figure 17.24-5
Monarch butterflies
Figure 17.24a
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Echinoderms– Echinoderms (phylum Echinodermata):
• Lack body segments• Typically show radial symmetry as adults but bilateral
symmetry as larvae • Have an endoskeleton• Have a water vascular system that facilitates
movement and gas exchange
– Echinoderms are a very diverse group.
Sea star
Sea urchin
Sea cucumber Sand dollar
Tube feet
Figure 17.25
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VERTEBRATE EVOLUTION AND DIVERSITY
– Vertebrates have unique endoskeletons composed of:
• A cranium (skull) • A backbone made of a series of bones called
vertebrae
Vertebra
Cranium(protects brain)
Figure 17.26
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Characteristics of Chordates– Chordates (phylum Chordata) all share four key
features that appear in the embryo and sometimes the adult:
• A dorsal, hollow nerve cord• A notochord• Pharyngeal slits• A post-anal tail
• A lancelet is an invertebrate chordate
Muscle segments
Notochord
Dorsal,
hollow
nerve cord
Pharyngeal
slits
Brain
Mouth
Anus
Post-anal
tail
Figure 17.27
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– Another chordate characteristic is body segmentation, apparent in the:
• Backbone of vertebrates • Segmental muscles of all chordates
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– Chordates consists of three groups of invertebrates:• Lancelets are bladelike animals without a cranium.• Tunicates, or sea squirts, also lack a cranium.• Hagfishes are eel-like forms that have a cranium.
– All other chordates are vertebrates.
Mouth
Tail
Lancelet Tunicates
Figure 17.28
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– An overview of chordate and vertebrate evolution
Ancestralchordate
Tunicates
Lancelets
Hagfishes
Lampreys
Cartilaginousfishes
Bony fishes
Amphibians
Reptiles
Mammals
Ch
ord
ate
s
Ve
rteb
rate
s
Te
trap
od
sAm
nio
tes
Figure 17.29
© 2010 Pearson Education, Inc.
Fishes– The first vertebrates were aquatic and probably evolved
during the early Cambrian period, about 542 million years ago. They:
• Lacked jaws • Are represented today by hagfishes
(a) Hagfish (inset: slime)
Figure 17.30a
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– Lampreys:• Are vertebrates• Have a cranium• But lack jaws
(b) Lamprey (inset: mouth)Figure 17.30b
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– The two major groups of living fishes are the:• Cartilaginous fishes (sharks and rays) with a flexible
skeleton made of cartilage
(c) Shark, a cartilaginous fish
Lateral line
Figure 17.30c
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• And bony fishes with a skeleton reinforced by hard calcium salts
– Bony fishes include:• Ray-finned fishes• Lungfishes• Lobe-finned fishes
(d) Bony fish
Lateral line
Operculum
Figure 17.30d
(a) Hagfish(inset: slime)
(b) Lamprey(inset: mouth)
(c) Shark, acartilaginous fish
(d) Bony fish
Lateral line
Operculum
Figure 17.30
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– Cartilaginous and bony fishes have a lateral line system that detects minor vibrations in the water.
– To provide lift off the bottom:• Cartilaginous fish must swim but
• Bony fish have swim bladders, gas-filled sacs that make them buoyant
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Amphibians– Amphibians:
• Exhibit a mixture of aquatic and terrestrial adaptations• Usually need water to reproduce• Typically undergo metamorphosis from an aquatic
larva to a terrestrial adult
(a) Tadpole and adult golden palm tree frog
(b) Frogs and salamanders: the two major groups of amphibians
Red-eyed tree frog Texas barred tiger salamander
Figure 17.31
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– Amphibians:• Were the first vertebrates to colonize land • Descended from fishes that had lungs and fins with muscles
Lobe-finned fish
Early amphibianFigure 17.32
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– Terrestrial vertebrates are collectively called tetrapods, which means “four feet.”
– Tetrapods include:• Amphibians• Reptiles• Mammals
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Reptiles– Reptiles (including birds) and mammals are amniotes,
which produce amniotic eggs that consist of a fluid-filled shell inside of which the embryo develops.
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– Reptiles include:• Snakes• Lizards• Turtles• Crocodiles• Alligators• Birds
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– Reptile adaptations to living on land include:• Amniotic eggs • Scaled, waterproof skin
Video: Galápagos Tortoise
Snake
Crocodile
Lizard
Turtle
Dinosaur
Birds
Figure 17.33
© 2010 Pearson Education, Inc.
– Nonbird reptiles are ectotherms, sometimes referred to as “cold-blooded,” which means that they obtain their body heat from the environment.
– A nonbird reptile can survive on less than 10% of the calories required by a bird or mammal of equivalent size.
– Dinosaurs were the largest animals ever to live on land.
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Birds– Recent genetic evidence shows that birds
evolved from a lineage of small, two-legged dinosaurs during the great reptilian radiation of the Mesozoic era.
– Birds have many adaptations that make them lighter in flight:
• Honeycombed bones• One instead of two ovaries• A beak instead of teeth
– Unlike other reptiles, birds are endotherms, maintaining a warmer and steady body temperature.
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– Birds wings adapted for flight are airfoils, powered by breast muscles anchored to a keel-like breastbone.
Lower air pressure
Higher air pressure
Airfoil
Figure 17.34
© 2010 Pearson Education, Inc.
Mammals– The first true mammals:
• Arose about 200 million years ago • Were probably small, nocturnal insect-eaters
– Most mammals are terrestrial although dolphins, porpoises, and whales are totally aquatic.
– Mammalian hallmarks are:• Hair • Mammary glands that produce milk, which nourishes the young
– There are three major groups of mammals:• Monotremes, egg-laying mammals• Marsupials, pouched mammals with a placenta• And eutherians, placental mammals
MAJOR GROUPS OF MAMMALS
Monotremes(hatched from eggs)
Marsupials(embryonic at birth)
Eutherians(fully developed at birth)
Echidna adultand egg Kangaroo newborn and mother
Wildebeest newbornand mother
Figure 17.35
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– Eutherian placentas provide more intimate and long-lasting association between the mother and her developing young than do marsupial placentas.
© 2010 Pearson Education, Inc.
THE HUMAN ANCESTRY– Humans are primates, the mammalian group
that also includes:• Lorises• Pottos• Lemurs• Tarsiers• Monkeys• Apes
Ancestralprimate
Lemurs, lorises,and pottos
Tarsiers
New World monkeys
Old World monkeys
Gibbons
Orangutans
Gorillas
Chimpanzees
Humans
An
thro
po
ids
Mo
nk
ey
sA
pe
s
Figure 17.36
© 2010 Pearson Education, Inc.
– Primates evolved from insect-eating mammals during the late Cretaceous period.– Primates are distinguished by characteristics that were shaped by the demands of living in trees. These characteristics include:
• Limber shoulder joints
• Eyes in front of the face
• Excellent eye-hand coordination
• Extensive parental care
The Evolution of Primates
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– Taxonomists divide the primates into three main groups:– The first group of primates includes:
• Lorises• Pottos• Lemurs• Tarsiers form the second group.
– The third group, anthropoids, includes:• Monkeys
Ring-tailed lemurFigure 17.37a
TarsierFigure 17.37b
Patas monkey (Old World monkey)Figure 17.37d
Black spider monkey(New World monkey)
Figure 17.37c
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• Hominoids, the ape relatives of humans
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• And humans
Ring-tailedlemur
Tarsier
Black spider monkey(New World monkey)
Patas monkey (Old World monkey)
Gorilla (ape)
Gibbon (ape)
Chimpanzee (ape)
Orangutan (ape)
HumanFigure 17.37
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The Emergence of Humankind– Humans and chimpanzees have shared a common
African ancestry for all but the last 5–7 million years.
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Some Common Misconceptions– Chimpanzees and humans represent two divergent
branches of the anthropoid tree that each evolved from a common, less specialized ancestor.
– Our ancestors were not chimpanzees or any other modern apes.
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– Human evolution is not a ladder with a parade of fossil hominids (members of the human family) leading directly to modern humans.
– Instead, human evolution is more like a multibranched bush than a ladder.
– At times in hominid history, several different human species coexisted.
Ardipithecusramidus
Australopithecusafarensis
Australopithecusafricanus
Paranthropusrobustus
Paranthropusboisei
Homoneanderthalensis
Homosapiens
Homohabilis
Homo erectus
?M
illi
on
s o
f y
ea
rs a
go
6.0
5.0
5.5
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
Figure 17.38
© 2010 Pearson Education, Inc.
– Upright posture and an enlarged brain appeared at separate times during human evolution.
– Different human features evolved at different rates.
– Upright posture was the first human characteristic to evolve.
© 2010 Pearson Education, Inc.
Australopithecus and the Antiquity of Bipedalism
– Before there was the genus Homo, several hominid species of the genus Australopithecus walked the African savanna.
– Fossil evidence pushes bipedalism in A. afarensis back to at least 4 million years ago.
(a) Australopithecusafarensis skeleton
(b) Ancient footprints (c) Model of anAustralopithecusafarensis male
Figure 17.39
© 2010 Pearson Education, Inc.
Homo Habilis and the Evolution of Inventive Minds
– Homo habilis, “handy-man”:• Had a larger brain, intermediate in size between
Australopithecus and modern humans• Walked upright• Made stone tools that enhanced hunting, gathering,
and scavenging on the African savanna
Homo Erectus and the Global Dispersal of Humanity
– Homo erectus was the first species to extend humanity’s range from Africa to other continents.
– The global dispersal began about 1.8 million years ago.
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
– Homo erectus:• Was taller than H. habilis• Had a larger brain• Gave rise to Neanderthals
Tunicates
Lancelets
Hagfishes
Lampreys
Cartilaginous fishes
Bony fishes
Amphibians
Reptiles
MammalsFigure 17.UN11
Ancestralprotist
True tissues
Bilateral symmetry
Sponges
Cnidarians
Molluscs
Flatworms
Annelids
Roundworms
Arthropods
Echinoderms
Chordates
Figure 17.UN15
Ancestralchordate
Tunicates
Lancelets
Hagfishes
Lampreys
Cartilaginousfishes
Bony fishes
Amphibians
Reptiles
Mammals
Ch
ord
ate
s
Ve
rteb
rate
s
Te
trap
od
s
Am
nio
tes
Figure 17.UN16
Gastropods Bivalves Cephalopods
MOLLUSCS
Figure 17.UN19
Arachnids
ARTHROPODS
Crustaceans InsectsMillipedesand Centipedes
Figure 17.UN20
Monotremes
MAMMALS
Marsupials Eutherians
Figure 17.UN21