Biology in Focus - Chapter 27
Transcript of Biology in Focus - Chapter 27
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CAMPBELL BIOLOGY IN FOCUS
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Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge
27The Rise of Animal Diversity
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Overview: Life Becomes Dangerous
Most animals are mobile and use traits such as strength, speed, toxins, or camouflage to detect, capture, and eat other organisms For example, the chameleon captures insect prey with
its long, sticky, fast-moving tongue
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Figure 27.1
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Current evidence indicates that animals evolved from single-celled eukaryotes similar to present-day choanoflagellates
More than 1.3 million animal species have been named to date; the actual number of species is estimated to be nearly 8 million
Concept 27.1: Animals originated more than 700 million years ago
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Fossil and Molecular Evidence
Fossil biochemical evidence and molecular clock studies date the common ancestor of all living animals to the period between 700 and 770 million years ago
Early members of the animal fossil record include the Ediacaran biota, which dates from about 560 million years ago
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Figure 27.2
(a) Dickinsoniacostata(taxonomic affiliationunknown)
2.5 cm
(b) The fossilmolluscKimberella
1 cm
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Figure 27.2a
(a) Dickinsoniacostata(taxonomic affiliationunknown)
2.5 cm
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Figure 27.2b
(b) The fossilmolluscKimberella
1 cm
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Early-Diverging Animal Groups
Sponges and cnidarians are two early-diverging groups of animals
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Figure 27.UN01
Other animalgroups
SpongesCnidarians
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Animals in the phylum Porifera are known informally as sponges
Sponges are filter feeders, capturing food particles suspended in the water that passes through their body
Water is drawn through pores into a central cavity and out through an opening at the top
Sponges lack true tissues, groups of cells that function as a unit
Sponges
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Figure 27.3
Waterflow
Pores
Choanocyte
Flagellum
Food particlesin mucus
CollarChoanocyte
Phagocytosis offood particles
Amoebocyte
Amoebocytes
Azure vase sponge(Callyspongia plicifera)
Spicules
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Figure 27.3a
Azure vase sponge(Callyspongia plicifera)
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Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food
Morphological similarities between choanocytes and choanoflagellates are consistent with the hypothesis that animals evolved from a choanoflagellate-like ancestor
Amoebocytes are mobile cells that play roles in digestion and structure
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Like most animals, members of the phylum Cnidaria have true tissues
Cnidarians are one of the oldest groups of animals, dating back to 680 million years ago
Cnidarians have diversified into a wide range of both sessile and motile forms, including hydrozoans, jellies, and sea anemones
Cnidarians
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Video: Clownfish Anemone
Video: Coral Reef
Video: Hydra Budding
Video: Hydra Eating
Video: Jelly Swimming
Video: Thimble Jellies
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Figure 27.4
(c) Anthozoa(a) Hydrozoa (b) Scyphozoa
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Figure 27.4a
(a) Hydrozoa
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Figure 27.4b
(b) Scyphozoa
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Figure 27.4c
(c) Anthozoa
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The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity
A single opening functions as mouth and anus Cnidarians are carnivores that use tentacles to
capture prey Cnidarians have no brain, but instead have a
noncentralized nerve net associated with sensory structures distributed throughout the body
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Concept 27.2: The diversity of large animals increased dramatically during the “Cambrian explosion”
The Cambrian explosion (535 to 525 million years ago) marks the earliest fossil appearance of many major groups of living animals
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Strata formed during the Cambrian explosion contain the oldest fossils of about half of all extant animal phyla
Evolutionary Change in the Cambrian Explosion
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Figure 27.5
Echinoderms
Sponges
Cnidarians
Chordates
Brachiopods
Annelids
Molluscs
Ediacaran
Arthropods
635CambrianPALEOZOICPROTEROZOIC
605Time (millions of years age)
575 545 515 485 0
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Fossils from the Cambrian period include the first hard, mineralized skeletons
Most fossils from this period are of bilaterians, a clade whose members have a complete digestive tract and a bilaterally symmetric form
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Figure 27.6
Hallucigenia fossil(530 mya)
1 cm
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Figure 27.6a
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Figure 27.6b
Hallucigenia fossil(530 mya)
1 cm
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There are several hypotheses regarding the cause of the Cambrian explosion and decline of Ediacaran biota New predator-prey relationships A rise in atmospheric oxygen The evolution of the Hox gene complex
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Dating the Origin of Bilaterians
Molecular clock estimates date the bilaterians to 100 million years earlier than the oldest fossil, which lived 560 million years ago
The appearance of larger, well-defended eukaryotes 635–542 million years ago indicates that bilaterian predators may have originated by that time
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Figure 27.7
15 m
(a) Valeria (800 mya):roughly spherical, nostructural defenses,soft-bodied
(b) Spiny acritarch(575 mya): about fivetimes larger thanValeria and covered inhard spines
75 m
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Figure 27.7a
15 m
(a) Valeria (800 mya):roughly spherical, nostructural defenses,soft-bodied
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Figure 27.7b
(b) Spiny acritarch(575 mya): about fivetimes larger thanValeria and covered inhard spines
75 m
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Concept 27.3: Diverse animal groups radiated in aquatic environments
Animals in the early Cambrian oceans were very diverse in morphology, way of life, and taxonomic affiliation
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Animal Body Plans
Zoologists sometimes categorize animals according to a body plan, a set of morphological and developmental traits
There are three important aspects of animal body plans Symmetry Tissues Body cavities
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Symmetry
Animals can be categorized according to the symmetry of their bodies or lack of it
Some animals have radial symmetry, with no front and back or left and right
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Figure 27.8
(b) Bilateral symmetry
(a) Radial symmetry
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Two-sided symmetry is called bilateral symmetry Bilaterally symmetrical animals have
A dorsal (top) side and a ventral (bottom) side A right and left side Anterior (head) and posterior (tail) ends
Many also have sensory equipment concentrated in the anterior end, including a brain in the head
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Radial animals are often sessile or planktonic (drifting or weakly swimming)
Bilateral animals often move actively and have a central nervous system enabling coordinated movement
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Tissues
Animal body plans also vary according to the organization of the animal’s tissues
Tissues are collections of specialized cells isolated from other tissues by membranous layers
During development, three germ layers give rise to the tissues and organs of the animal embryo
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Figure 27.9
Digestive tract(from endoderm)
Body covering(from ectoderm)
Tissue layerlining body cavityand suspendinginternal organs(from mesoderm)
Body cavity
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Ectoderm is the germ layer covering the embryo’s surface
Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron
Cnidarians have only these two germ layers Mesoderm is a third germ layer that fills the space
between the ectoderm and the endoderm in all bilaterally symmetric animals
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Body Cavities
Most bilaterians possess a body cavity (coelom), a fluid- or air-filled space between the digestive tract and the outer body wall
The body cavity may Cushion suspended organs Act as a hydrostatic skeleton Enable internal organs to move independently of the
body wall
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The Diversification of Animals
Zoologists recognize about three dozen animal phyla
Phylogenies now combine molecular data from multiple sources with morphological data to determine the relationships among animal phyla
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Video: C. Elegans Crawling
Video: Earthworm Locomotion
Video: Echinoderm Tubefeet
Video: Nudibranchs
Video: Rotifer
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Figure 27.10
ANCESTRALPROTIST
770 millionyears ago
680 millionyears ago
670 millionyears ago
Arthropoda
Nematoda
Annelida
Mollusca
Brachiopoda
Ectoprocta
Rotifera
Platyhelminthes
Chordata
Echinodermata
Metazoa
Hemichordata
Cnidaria
Ctenophora
Porifera
EcdysozoaLophotrochozoa
Bilateria
Deuterostom
ia
Eumetazoa
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The following points are reflected in the animal phylogeny
1. All animals share a common ancestor2. Sponges are basal animals3. Eumetazoa is a clade of animals (eumetazoans) with
true tissues4. Most animal phyla belong to the clade Bilateria and are
called bilaterians5. Most animals are invertebrates, lacking a backbone;
Chordata is the only phylum that includes vertebrates, animals with a backbone
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Bilaterian Radiation I: Diverse Invertebrates
Bilaterians have diversified into three major clades Lophotrochozoa Ecdysozoa Deuterostomia
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An Overview of Invertebrate Diversity
Bilaterian invertebrates account for 95% of known animal species
They are morphologically diverse and occupy almost every habitat on Earth
This morphological diversity is mirrored by extensive taxonomic diversity
The vast majority of invertebrate species belong to the Lophotrochozoa and Ecdysozoa; a few belong to the Deuterostomia
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Figure 27.11
Arthropoda(1,000,000 species)
Nematoda(25,000 species)
Annelida (16,500 species)
Mollusca(93,000 species)
Ectoprocta(4,500 species)
Ectoprocts
EcdysozoaLophotrochozoa
Echinodermata(7,000 species)
Hemichordata(85 species)
Deuterostomia
An octopus A roundworm
A web-building spider(an arachnid)
Sea urchins and asea starAn acorn worm
A fireworm, a marine annelid
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Figure 27.11a
Annelida (16,500 species)
Mollusca(93,000 species)
Ectoprocta(4,500 species)
Ectoprocts
Lophotrochozoa
An octopus
A fireworm, a marine annelid
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Figure 27.11aa
Ectoprocta(4,500 species)
Ectoprocts
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Figure 27.11ab
Mollusca(93,000 species)
An octopus
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Figure 27.11ac
Annelida (16,500 species)
A fireworm, a marine annelid
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Figure 27.11b
Arthropoda(1,000,000 species)
Nematoda(25,000 species)
Ecdysozoa
A roundworm
A web-building spider(an arachnid)
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Figure 27.11ba
Nematoda(25,000 species)
A roundworm
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Figure 27.11bb
Arthropoda(1,000,000 species)
A web-building spider(an arachnid)
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Figure 27.11c
Echinodermata(7,000 species
Hemichordata(85 species)
Deuterostomia
Sea urchins and asea starAn acorn worm
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Figure 27.11ca
Hemichordata(85 species)
An acorn worm
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Figure 27.11cb
Echinodermata(7,000 species)
Sea urchins and asea star
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Arthropod Origins
Two out of every three known species of animals are arthropods
Members of the phylum Arthropoda are found in nearly all habitats of the biosphere
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The arthropod body plan consists of a segmented body, hard exoskeleton, and jointed appendages
This body plan dates to the Cambrian explosion (535–525 million years ago)
Early arthropods show little variation from segment to segment
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Figure 27.UN02
A fossil trilobite
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Arthropod evolution is characterized by a decrease in the number of segments and an increase in appendage specialization
These changes may have been caused by changes in Hox gene sequence or regulation
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Figure 27.12
Red indicates regionsin which Ubx orabd-A genes wereexpressed.
Otherecdysozoans
Arthropods
OnychophoransCommon ancestor
Origin of Ubx andabd-A Hox genes?
Ant antennaJ jawsL1–L15 body segments
Experiment
Results
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Figure 27.12a
Red indicates regionsin which Ubx orabd-A genes wereexpressed.
Ant antennaJ jawsL1–L15 body segments
Results
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Bilaterian Radiation II: Aquatic Vertebrates
The appearance of large predatory animals and the explosive radiation of bilaterian invertebrates radically altered life in the oceans
One type of animal gave rise to vertebrates, one of the most successful groups of animals
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Figure 27.13
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The animals called vertebrates get their name from vertebrae, the series of bones that make up the backbone
Vertebrates are members of phylum Chordata Chordates are bilaterian animals that belong to the
clade of animals known as Deuterostomia
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Early Chordate Evolution
All chordates share a set of derived characters Some species have some of these traits only during
embryonic development Four key characters of chordates
Notochord, a flexible rod providing support Dorsal, hollow nerve cord Pharyngeal slits or pharyngeal clefts, which function
in filter feeding, as gills, or as parts of the head Muscular, post-anal tail
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Video: Clownfish Anemone
Video: Coral Reef
Video: Manta Ray
Video: Sea Horses
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Figure 27.14
Musclesegments
Notochord
Post-anal tail
Anus
Mouth
Dorsal, hollow nerve cord
Pharyngeal slits or clefts
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Lancelets are a basal group of extant, blade-shaped animals that closely resemble the idealized chordate
Tunicates are another early diverging chordate group, but they only display key chordate traits during their larval stage
The ancestral chordate may have looked similar to a lancelet
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Figure 27.15
(a) Lancelet (b) Tunicate
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Figure 27.15a
(a) Lancelet
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Figure 27.15b
(b) Tunicate
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In addition to the features of all chordates, early vertebrates had a backbone and a well-defined head with sensory organs and a skull
Fossils representing the transition to vertebrates formed during the Cambrian explosion
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The Rise of Vertebrates
Early vertebrates were more efficient at capturing food and evading predators than their ancestors
The earliest vertebrates were conodonts, soft-bodied, jawless animals that hunted prey using a set of barbed hooks in their mouth
There are only two extant lineages of jawless vertebrates, the hagfishes and lampreys
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Figure 27.16
Chondrichthyes ActinistiaActinopterygii
Myxini
Tetrapoda
Petromyzontida
Dipnoi
Chondrichthyes(sharks, rays, chimaeras)
Actinistia(coelacanths)
Actinopterygii(ray-finned fishes)
Myxini(hagfishes)
Tetrapoda(amphibians,reptiles,mammals)
Petromyzontida(lampreys)
Dipnoi(lungfishes)
Limbs with digits
Lobedfins
Lungsor lung derivatives
Jaws,mineralized
skeleton
Vertebralcolumn
Commonancestor ofvertebrates
TetrapodsLobe-fins
Osteichthyans
Gnathostom
esVertebrates
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© 2014 Pearson Education, Inc.
Figure 27.16a
Chondrichthyes(sharks, rays, chimaeras)
Actinistia(coelacanths)
Actinopterygii(ray-finned fishes)
Myxini(hagfishes)
Tetrapoda(amphibians,reptiles,mammals)
Petromyzontida(lampreys)
Dipnoi(lungfishes)
Limbs with digits
Lobedfins
Lungsor lung derivatives
Jaws,mineralized
skeleton
Vertebralcolumn
Commonancestor ofvertebrates
Tetrapods
Lobe-finsO
steichthyansG
nathostomes
Vertebrates
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Figure 27.16b
Chondrichthyes
ActinistiaActinopterygiiMyxini
Tetrapoda
Petromyzontida
Dipnoi
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Figure 27.16ba
Myxini
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Figure 27.16bb
Petromyzontida
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Figure 27.16bba
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Figure 27.16bbb
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Figure 27.16bc
Chondrichthyes
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Figure 27.16bd
Actinopterygii
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Figure 27.16be
Actinistia
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Figure 27.16bf
Dipnoi
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Figure 27.16bg
Tetrapoda
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Today, jawed vertebrates, or gnathostomes, outnumber jawless vertebrates
Early gnathostome success is likely due to adaptations for predation including paired fins and tails for efficient swimming and jaws for grasping prey
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Video: Lobster Mouth Parts
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Figure 27.17
0.5 m
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Gnathostomes diverged into three surviving lineages, chondrichthyans, ray-finned fishes, and lobe-fins
Humans and other terrestrial animals are included in the lobe-fins
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Chondrichthyans include sharks, rays, and their relatives
The skeletons of chondrichthyans are composed primarily of cartilage
This group includes some of the largest and most successful vertebrate predators
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Ray-finned fishes include nearly all the familiar aquatic osteichthyans
The vast majority of vertebrates belong to the clade of gnathostomes called Osteichthyes
Nearly all living osteichthyans have a bony endoskeleton
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Lobe-fins are the other major lineage of osteichthyans
A key derived trait in the lobe-fins is the presence of rod-shaped bones surrounded by a thick layer of muscle in their pectoral and pelvic fins
Three lineages survive: the coelacanths, lungfishes, and tetrapods, terrestrial vertebrates with limbs and digits
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Concept 27.4: Several animal groups had features facilitating their colonization of land
Some bilaterian animals colonized land following the Cambrian explosion, causing profound changes in terrestrial communities
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Early Land Animals
Members of many animal groups made the transition to terrestrial life
Arthropods were among the first animals to colonize the land about 450 million years ago
Vertebrates colonized land 365 million years ago
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The evolutionary changes that accompanied the transition to terrestrial life were much less extensive in animals than in plants
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Video: Bee Pollinating
Video: Butterfly Emerging
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Figure 27.18
GREEN ALGA MARINE CRUSTACEAN AQUATIC LOBE-FIN
Derived (roots) N/A N/A
LAND PLANTS INSECTS TERRESTRIALVERTEBRATES
N/A
Derived (lignin/stems)
Derived (vascular system)
Derived (cuticle)
Derived (stomata) Derived (tracheal system)
Ancestral
Ancestral
Ancestral
Ancestral
Derived(amniotic egg/scales)
Ancestral
Ancestral
Ancestral (skeletal system)Derived (limbs)
Ancestral
Anchoringstructure
Supportstructure
Internaltransport
Muscle/nerve cells
Protectionagainst
desiccation
Gas exchange
TER
RES
TRIA
LO
RG
AN
ISM
CH
AR
AC
TER
AQ
UA
TIC
AN
CES
TOR
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© 2014 Pearson Education, Inc.
Figure 27.18a
GREEN ALGA
Derived (roots)
LAND PLANTS
N/A
Derived (lignin/stems)
Derived (vascular system)
Derived (cuticle)
Derived (stomata)
Anchoring structure
Support structure
Internal transport
Muscle/nerve cellsProtection against
desiccationGas exchange
TER
RES
TRIA
LO
RG
AN
ISM
CH
AR
AC
TER
AQ
UA
TIC
AN
CES
TOR
![Page 101: Biology in Focus - Chapter 27](https://reader034.fdocuments.in/reader034/viewer/2022042502/587a4d031a28ab00148b6aa7/html5/thumbnails/101.jpg)
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Figure 27.18b
Anchoring structure
Support structure
Internal transport
Muscle/nerve cellsProtection against
desiccationGas exchange
TER
RES
TRIA
LO
RG
AN
ISM
CH
AR
AC
TER
AQ
UA
TIC
AN
CES
TOR
MARINE CRUSTACEAN
N/A
INSECTS
Derived (tracheal system)
Ancestral
Ancestral
Ancestral
Ancestral
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Figure 27.18c
Anchoring structure
Support structure
Internal transportMuscle/nerve cellsProtection against
desiccationGas exchange
TER
RES
TRIA
LO
RG
AN
ISM
CH
AR
AC
TER
AQ
UA
TIC
AN
CES
TOR
AQUATIC LOBE-FIN
N/A
TERRESTRIALVERTEBRATES
Derived(amniotic egg/scales)
AncestralAncestral
Ancestral (skeletal system)Derived (limbs)
Ancestral
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Colonization of Land by Arthropods
Terrestrial lineages have arisen in several different arthropod groups, including millipedes, spiders, crabs, and insects
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General Characteristics of Arthropods
The appendages of some living arthropods are modified for functions such as walking, feeding, sensory reception, reproduction, and defense
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Figure 27.19
Cephalothorax
Swimming appen-dages (one pair perabdominal segment)
Abdomen
Antennae(sensoryreception)
ThoraxHead
Pincer(defense)
Mouthparts(feeding)
Walking legs
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The body of an arthropod is completely covered by the cuticle, an exoskeleton made of layers of protein and the polysaccharide chitin
The exoskeleton provides structural support and protection from physical harm and desiccation
A variety of organs specialized for gas exchange have evolved in arthropods
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Insects
The insects and their relatives include more species than all other forms of life combined
They live in almost every terrestrial habitat and in fresh water
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Figure 27.20
Lepidopterans
Hymenopterans Hemipterans
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Figure 27.20a
Lepidopterans
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Figure 27.20aa
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Figure 27.20ab
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Figure 27.20b
Hymenopterans
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Figure 27.20c
Hemipterans
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Insects diversified several times following the evolution of flight, adaptation to feeding on gymnosperms, and the expansion of angiosperms
Insect and plant diversity declined during the Cretaceous extinction, but has been increasing in the 65 million years since
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Flight is one key to the great success of insects An animal that can fly can escape predators, find
food, and disperse to new habitats much faster than organisms that can only crawl
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Figure 27.21
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Terrestrial Vertebrates
One of the most significant events in vertebrate history was when the fins of some lobe-fins evolved into the limbs and feet of tetrapods
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The Origin of Tetrapods
Tiktaalik, nicknamed a “fishapod,” shows both fish and tetrapod characteristics
It had Fins, gills, lungs, and scales Ribs to breathe air and support its body A neck and shoulders Fins with the bone pattern of a tetrapod limb
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Figure 27.22
FishCharacters
Neck Shoulder bones
Head
Fin
Ulna Flat skull
Eyes on top of skull
Humerus
Ribs Scales
Fin skeleton
Elbow Radius
“Wrist”
TetrapodCharacters
ScalesFinsGills and lungs
NeckRibsFin skeletonFlat skullEyes on top of skull
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Figure 27.22a
Neck Shoulder bones
Head
Fin
Flat skull
Eyes on top of skull
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Figure 27.22b
Ribs
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Figure 27.22c
Scales
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Figure 27.22d
Ulna Humerus
Fin skeleton
Elbow Radius
“Wrist”
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Tiktaalik could most likely prop itself on its fins, but not walk
Fins became progressively more limb-like over evolutionary time, leading to the first appearance of tetrapods 365 million years ago
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Figure 27.23
Lungfishes
Eusthenopteron
Panderichthys
Tiktaalik
Acanthostega
Tulerpeton
Amphibians
Amniotes
Limbswith digits
Silurian Permian Carboniferous Devonian
PALEOZOIC
Key tolimb bones
Time (millions of years ago) 415 340 355 370 385 400 325 280 295 310 265 0
UlnaRadiusHumerus
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Figure 27.23a
Silurian Permian Carboniferous Devonian
PALEOZOIC
Key tolimb bones
Time (millions of years ago) 415 340 355 370 385 400 325 280 295 310 265 0
UlnaRadiusHumerus
Lungfishes
Eusthenopteron
Panderichthys
Tiktaalik
Lobe-fins with limbs with digits
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Figure 27.23b
Silurian Permian Carboniferous Devonian
PALEOZOIC
Key tolimb bones
Time (millions of years ago) 415 340 355 370 385 400 325 280 295 310 265 0
UlnaRadiusHumerus
Acanthostega
Tulerpeton
Amphibians
Amniotes
Limbswith digits
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Amphibians
Amphibians are represented by about 6,150 species including salamanders, frogs, and caecilians
Amphibians are restricted to moist areas within their terrestrial habitats
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Video: Marine Iguana
Video: Flapping Geese
Video: Snake Wrestling
Video: Soaring Hawk
Video: Swans Taking Flight
Video: Tortoise
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Figure 27.24
Salamandersretain their tailsas adults.
Caecilians haveno legs and aremainly burrowinganimals.
Frogs and toadslack tails as adults.
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Figure 27.24a
Salamanders retain their tails asadults.
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Figure 27.24b
Frogs and toads lack tails as adults.
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Figure 27.24c
Caecilians have no legs and aremainly burrowing animals.
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Terrestrial Adaptations in Amniotes
Amniotes are a group of tetrapods whose living members are the reptiles, including birds, and mammals
Amniotes are named for the major derived character of the clade, the amniotic egg, which contains membranes that protect the embryo
The extraembryonic membranes are the amnion, chorion, yolk sac, and allantois
The amniotic eggs of most reptiles and some mammals have a shell
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Video: Bat Licking
Video: Bat Pollinating
Video: Chimp Agonistic
Video: Chimp Cracking Nut
Video: Gibbon Brachiating
Video: Sea Lion
Video: Shark Eating Seal
Video: Wolves Agonistic
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Figure 27.25
Amnioticcavity withamniotic fluid Yolk
(nutrients)
Albumen
Yolk sac
Shell
ChorionAllantoisAmnion
Embryo
Extraembryonic membranes
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The Origin and Radiation of Amniotes
Living amphibians and amniotes split from a common ancestor about 350 million years ago
Early amniotes were more tolerant of dry conditions than early tetrapods
The earliest amniotes were small predators with sharp teeth and long jaws
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Reptiles are one of two living lineages of amniotes Members of the reptile clade includes the tuataras,
lizards, snakes, turtles, crocodilians, birds, and some extinct groups
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Figure 27.26
Tuataras
Squamates
Birds
Crocodilians
Turtles
†Plesiosaurs
†Pterosaurs
†Ornithischiandinosaurs
†Saurischiandinosaurs otherthan birds
Crocodilians
Birds
Turtles
Tuataras
Squamates
Commonancestorof dinosaurs
Commonancestorof reptiles
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Figure 27.26a
†Plesiosaurs
†Pterosaurs
†Ornithischiandinosaurs
†Saurischiandinosaurs otherthan birds
Crocodilians
Birds
Turtles
Tuataras
Squamates
Commonancestorof dinosaurs
Commonancestorof reptiles
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Figure 27.26b
Tuataras Squamates
Birds
Crocodilians
Turtles
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Figure 27.26ba
Crocodilians
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Figure 27.26bb
Birds
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Figure 27.26bba
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Figure 27.26bbb
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Figure 27.26bc
Turtles
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Figure 27.26bd
Tuataras
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Figure 27.26be
Squamates
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Reptiles have scales that create a waterproof barrier Most reptiles lay shelled eggs on land Most reptiles are ectothermic, absorbing external
heat as the main source of body heat Birds are endothermic, capable of keeping the body
warm through metabolism
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Mammals are the other extant lineage of amniotes There are many distinctive traits of mammals
including Mammary glands that produce milk Hair A fat layer under the skin A high metabolic rate, due to endothermy Differentiated teeth
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The first true mammals evolved from synapsids and arose about 180 million years ago
By 140 million years ago, the three living lineages of mammals had emerged Monotremes, egg-laying mammals Marsupials, mammals with a pouch Eutherians, placental mammals
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Figure 27.27
Monotremes Marsupials
Eutherians
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Figure 27.27a
Monotremes
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Figure 27.27aa
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Figure 27.27ab
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Figure 27.27b
Marsupials
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Figure 27.27c
Eutherians
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Human Evolution
Humans (Homo sapiens) are primates, nested within a group informally called apes
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Figure 27.28
New World monkeys
Old World monkeys
Humans
Chimpanzeesand bonobos
Gorillas
Orangutans
Gibbons
“Apes”
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A number of characters distinguish humans from other apes Upright posture and bipedal locomotion Larger brains capable of language, symbolic thought,
artistic expression, and the use of complex tools
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The evolution of bipedalism preceded the evolution of increased brain size in early human ancestors
Brain size, body size, and tool use increased over time in Homo species
Modern humans, H. sapiens, originated in Africa about 200,000 years ago and colonized the rest of the world from there
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Figure 27.29
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Concept 27.5: Animals have transformed ecosystems and altered the course of evolution
The rise of animals from a microbe-only world affected all aspects of ecological communities, in the sea and on land
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Ecological Effects of Animals
The oceans of early Earth likely had very different properties than the oceans of today
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Figure 27.30
(b) Changes to ocean conditions by 530 mya
(a) Ocean conditions before 600 mya
Murky, poorly-mixedLow oxygenCyanobacteria
Clear, well-mixedHigh oxygenEukaryotic algae
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Marine Ecosystems
The rise of filter-feeding animals likely caused the decline of cyanobacteria and other suspended particles in the oceans during the early Cambrian
This resulted in a shift to algae as the dominant producers and changed the feeding relationships in marine ecosystems
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Terrestrial ecosystems were transformed with the move of animals to land
Herbivores, such as the lesser snow goose, can improve the growth of plants at low population sizes through additions of nutrient-rich wastes
At high population sizes herbivores can defoliate large tracts of land
Terrestrial Ecosystems
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Figure 27.31
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Evolutionary Effects of Animals
The origin of mobile, heterotrophic animals with a complete digestive tract drove some species to extinction and initiated ongoing “arms races” between bilaterian predators and prey
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Evolutionary Radiations
Two species that interact can exert strong, reciprocal selective pressures on one another For example, flower form can be influenced by the
structure of its pollinators’ mouth parts, and vice versa
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Figure 27.32
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Reciprocal selection pressures can also occur when the origin of new species in one group stimulates further radiation in another group For example, the origin of a new group of
animals provides new food sources for parasites, resulting in radiations in parasite groups
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Human Impacts on Evolution
Humans have made large changes to the environment that have altered the selective pressures faced by many species For example, human targeting of large fish for
harvesting has led to the reduction in age and size at which individuals reach sexual maturity
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Figure 27.33
1960 1970 1980 1990 2000Year
7.0
6.5
6.0
5.5
5.0
Age
at m
atur
ity (y
ears
)
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Figure 27.33a
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Rapid species declines over the past 400 years indicate that human activities may be driving a sixth mass extinction
Molluscs, including pearl mussels, have suffered the greatest impact of human-caused extinctions
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Figure 27.34
Workers on a mound of pearlmussels killed to make buttons(ca. 1919)
An endangeredPacific islandland snail,Partula suturalis
Recorded extinctions of animalspecies
Otherinvertebrates
Reptiles (excludingbirds)
Molluscs
Insects
Fishes Birds
Mammals
Amphibians
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Figure 27.34a
Recorded extinctions of animal species
Otherinvertebrates
Reptiles (excludingbirds)
Molluscs
Insects
Fishes Birds
Mammals
Amphibians
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Figure 27.34b
An endangeredPacific islandland snail,Partula suturalis
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Figure 27.43c
Workers on a mound of pearlmussels killed to make buttons(ca. 1919)
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The major threats imposed on species by human activities include habitat loss, pollution, and competition or predation by introduced, non-native species
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Figure 27.UN03
SouthernperiwinklesNorthernperiwinkles
Southern Northern
Ave
rage
num
ber o
f p
eriw
inkl
es k
illed
Source population of crab
6
4
2
0
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Figure 27.UN04
Origin anddiversification
of dinosaurs365 mya:Early land
animalsDiversification
of mammals
535–525 mya:Cambrian explosion
560 mya:Ediacaran animals
Millions of years age (mya)
Neo-proterozoic Paleozoic
1,000
Era
542 251
Mesozoic
65.5
Ceno- zoic
0
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Figure 27.UN05