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© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko
PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Chapter 17Chapter 17The Evolution of Animals
1
THE ORIGINS OF ANIMAL DIVERSITY
• Animal life began in Precambrian seas with the
evolution of multicellular creatures that ate other
organisms.
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2
What Is an Animal?
• Animals are
– eukaryotic,
– multicellular,
– heterotrophic organisms that obtain nutrients by ingestion, and
– able to digest their food within their bodies.
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• Animal cells do not have
– cell walls that provide strong support in the bodies of plants and fungi.
• Most animals have
– muscle cells and
– nerve cells that control the muscles.
What Is an Animal?
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• Most animals
– are diploid,
– reproduce sexually, and
– proceed through a series of typically similar developmental stages.
What Is an Animal?
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Figure 17.2
MEIOSIS
Sperm
Egg
Adult
Key
Haploid (n)
Diploid (2n)
FERTILIZATION
MITOSIS
METAMORPHOSIS
Zygote(fertilized egg)
Eight-cell stage
Blastula(cross section)
Digestive tract
Outer cell layer(ectoderm)
Larva
Inner cell layer(endoderm)
Internal sac Later gastrula(cross section)
Future middlelayer of cells(mesoderm)
Early gastrula(cross section)
1
2
3
8
4
7
6
5
7
Figure 17.2a-2
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Sperm
Egg
Adult
1
FERTILIZATION
Zygote(fertilized egg)
2
9
Figure 17.2a-3
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Sperm
Egg
Adult
1
MITOSIS
FERTILIZATION
Zygote(fertilized egg)
Eight-cell stage
2
3
10
Figure 17.2a-4
Key
Haploid (n)
Diploid (2n)
MEIOSIS
Sperm
Egg
Adult
1
MITOSIS
FERTILIZATION
Zygote(fertilized egg)
Eight-cell stage
Blastula(cross section)
2
3
4
11
Figure 17.2b-1
Key
Haploid (n)
Diploid (2n)
4
5
Blastula
(cross section)
Early gastrula
(cross section)
12
Figure 17.2b-2
Key
Haploid (n)
Diploid (2n)
4
5
6
Blastula
(cross section)
Outer cell layer
(ectoderm)
Inner cell layer
(endoderm)
Internal sacLater gastrula
(cross section)
Future middle layer
of cells (mesoderm)
Early gastrula
(cross section)
13
Figure 17.2b-3
Key
Haploid (n)
Diploid (2n)
4
5
6
7
Larva
Digestive tract
Blastula
(cross section)
Outer cell layer
(ectoderm)
Inner cell layer
(endoderm)
Internal sacLater gastrula
(cross section)
Future middle layer
of cells (mesoderm)
Early gastrula
(cross section)
14
Figure 17.2b-4
Key
Haploid (n)
Diploid (2n)
METAMORPHOSIS
8
4
5
6
7
Adult
Larva
Digestive tract
Blastula
(cross section)
Outer cell layer
(ectoderm)
Inner cell layer
(endoderm)
Internal sacLater gastrula
(cross section)
Future middle layer
of cells (mesoderm)
Early gastrula
(cross section)
15
Early Animals and the Cambrian Explosion
• Scientists hypothesize that animals evolved from a
colonial flagellated protist.
• The oldest animal fossils found are 550–575
million years old.
• The molecular data suggest a much earlier origin
for animals.
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• Animal diversification appears to have accelerated
rapidly from 525-535 million years ago, during the
Cambrian period.
• Because so many animal body plans and new
phyla appear in the fossils from such an
evolutionarily short time span, biologists call this
episode the Cambrian explosion.
Early Animals and the Cambrian Explosion
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• The Cambrian explosion may have been ignited by
– increasingly complex predator-prey relationships and/or
– an increase in atmospheric oxygen.
• The genetic framework for complex bodies, a set of
“master control” genes, was already in place.
Early Animals and the Cambrian Explosion
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19
Animal Phylogeny
• Biologists categorize animals by
– “body plan,” general features of body structure and,
– more recently, genetic data.
• One major branch point distinguishes sponges
from all other animals because, unlike more
complex animals, sponges lack true tissues.
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Figure 17.6
Ancestralprotist
No true tissues
Radial symmetry
Tissues
Bilateral symmetry
Sponges
Cnidarians
Molluscs
Flatworms
Annelids
Roundworms
Arthropods
Echinoderms
Chordates
22
• 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.
Animal Phylogeny
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• 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.
Animal Phylogeny
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Arthropods
• Arthropods (phylum Arthropoda) are named for
their jointed appendages.
• There are over 1 million arthropod species
identified, mostly insects.
• Arthropods are a very diverse and successful
group, occurring in nearly all habitats in the
biosphere.
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• There are four main groups of arthropods:
1. arachnids,
2. crustaceans,
3. millipedes and centipedes, and
4. insects.
Arthropods
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General Characteristics of Arthropods
• Arthropods are segmented animals with
– specialized segments and
– appendages for an efficient division of labor among body regions.
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General Characteristics of Arthropods
• The body of arthropods is completely covered by an exoskeleton, an external skeleton that provides
– protection and
– points of attachment for the muscles that move appendages.
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Figure 17.19
AbdomenCephalothorax
(head and thorax)
Swimmingappendage
Antenna(sensory reception)
Eyes on movable stalks
Mouthparts (feeding)
Walking leg
Walking legs
Pincer (defense)
58
• Arachnids
– usually live on land,
– usually have four pairs of walking legs and a specialized pair of feeding appendages, and
– include spiders, scorpions, ticks, and mites.
Arachnids
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Figure 17.20
Pair of feedingappendages
Leg (four pairs)
Spider Wood tick
Dust miteScorpionPair of silk-spinningappendages
60
• Crustaceans
– are nearly all aquatic,
– have multiple pairs of specialized appendages, and
– include crabs, lobsters, crayfish, shrimp, and barnacles.
Crustaceans
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Figure 17.21
Two feedingappendages
Leg (three or more pairs)
Antennae
BarnaclesCrayfish
Pill bug
Shrimp
Crab
62
• Millipedes and centipedes have similar segments
over most of the body.
• Millipedes
– eat decaying plant matter and
– have two pairs of short legs per body segment.
• Centipedes
– are terrestrial carnivores with poison claws and
– have one pair of short legs per body segment.
Millipedes and Centipedes
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• Insects typically have a three-part body
consisting of
1. head,
2. thorax, and
3. abdomen.
Insect Anatomy
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• The insect head usually bears
– a pair of sensory antennae and
– 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
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• Insects outnumber all other forms of life combined
in terms of species diversity.
• Insects live in
– almost every terrestrial habitat,
– fresh water, and
– the air.
Insect Diversity
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Figure 17.24
Rhinoceros beetle
Praying mantisRed-and-black-striped stink bug
Jeweled beetle Buckeye butterfly
Trilobite beetle
Greater arid-land katydid
Rainbow bush locust
69
• 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.
Insect Diversity
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Figure 17.25
The larva spends itstime eatingand growing.
After severalmolts, the larvabecomes a pupa.
Larval organsbreak downand adultorgans develop. The adult
emerges fromthe cocoon.
The butterflyflies off andreproduces.
71
VERTEBRATE EVOLUTION AND DIVERSITY
• Vertebrates have unique endoskeletons
composed of
– a cranium (skull) and
– a backbone made of a series of bones called vertebrae.
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• Chordates consists of three groups of
invertebrates:
1. lancelets are bladelike animals without a cranium,
2. tunicates, or sea squirts, also lack a cranium, and
3. hagfishes are eel-like forms that have a cranium.
• All other chordates are vertebrates.
Characteristics of Chordates
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• An overview of chordate and vertebrate evolution
Characteristics of Chordates
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Figure 17.30
Ancestralchordate
Tunicates
Lancelets
Hagfishes
Lampreys
Cartilaginousfishes
Bony fishes
Amphibians
Reptiles
Mammals
Ch
ord
ate
s
Verte
bra
tes
Tetra
po
ds
Am
nio
tes
83
Fishes
• The first vertebrates were aquatic and probably
evolved during the early Cambrian period, about
542 million years ago. They
– lacked jaws and
– are represented today by lampreys.
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Figure 17.31
(a) Hagfish(b) Lamprey (inset: mouth)
(c) Shark, a cartilaginous fish
(d) Bony fish
Lateral line Operculum
85
• The two major groups of living fishes are the
1. cartilaginous fishes (sharks and rays), with a flexible skeleton made of cartilage, and
2. bony fishes, with a skeleton reinforced by hard calcium salts.
• Bony fishes include
– ray-finned fishes and
– lobe-finned fishes.
Fishes
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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 help them be buoyant.
Fishes
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Amphibians
• Amphibians
– exhibit a mixture of aquatic and terrestrial adaptations,
– usually need water to reproduce, and
– typically undergo metamorphosis from an aquatic larva to a terrestrial adult.
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Figure 17.32
Gray tree frog tadpole
Malaysian horned frog
Gray tree frog
Texas barred tiger salamander
89
• Amphibians
– were the first vertebrates to colonize land and
– descended from fishes that had
– lungs,
– fins with muscles, and
– skeletal supports strong enough to enable some
movement on land.
Amphibians
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