Deuterostomate Animals

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Deuterostomate Animals
2
Deuterostomate Animals

• Deuterostome Ancestors
• Echinoderms Pentaradial Symmetry
• Hemichordates Conservative Evolution
• Chordates New Ways of Feeding
• Colonizing the Land Obtaining Oxygen from the
  Air
• Birds More Feathers and Better Flight
• The Origin and Diversity of Mammals
• Primates and the Origin of Humans
• Deuterostomes and Protostomes Shared
  Evolutionary Themes

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Deuterostome Ancestors

• A group of extinct animals known as the
  yunnanozoans are the likely ancestors of all
  deuterostomes.
• These animals had a large mouth, six pairs of
  external gills, and a lightly cuticularized,
  segmented posterior body section.

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Figure 34.1 The Ancestral Deuterostomes Had
External Gills
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Deuterostome Ancestors

• Modern deuterostomes fall into two major clades.
• The echinoderms and hemichordates compose one
  clade.
• This group is characterized by a three-part
  coelom and bilaterally symmetrical, ciliated
  larvae.
• The other clade includes the chordates.
• The ancestors of this clade had nonfeeding,
  tadpole-like larvae and a unique dorsal
  supporting structure.

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Figure 34.2 A Current Phylogeny of the
Deuterostomes
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Echinoderms Pentaradial Symmetry

• Two major structural features evolved in the
  echinoderms (phylum Echinodermata).
• One was a system of calcified internal plates
  covered by thin layers of skin and some muscles.
• In some early echinoderm ancestors, these plates
  became fused inside the entire body, giving rise
  to an internal skeleton.
• The other feature was a water vascular system, a
  network of calcified hydraulic canals leading to
  extensions called tube feet.
• This system functions in gas exchange,
  locomotion, and feeding.

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Figure 34.4 Echinoderms Display Two Evolutionary
Innovations (Part 1)
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Figure 34.4 Echinoderms Display Two Evolutionary
Innovations (Part 2)
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Echinoderms Pentaradial Symmetry

• The development of these two structural
  innovations led to a striking evolutionary
  radiation.
• There have been about 23 echinoderm classes
  described. Only 6 classes survive today, with a
  total of about 7,000 species.
• Nearly all living species have a bilaterally
  symmetrical, ciliated larva that feeds for some
  time as a planktonic organism before transforming
  into an adult with pentaradial symmetry.
• Living echinoderms are divided into two lineages
  the subphylum Pelmatozoa and the subphylum
  Eleutherozoa.

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Echinoderms Pentaradial Symmetry

• The arms are used for feeding. They are oriented
  in passing water currents so that food particles
  stick to tube feet on the arms, which transfer
  them to a groove that runs down the arm to the
  mouth.
• Feather stars are similar to sea-lilies, but they
  have flexible appendages with which they grasp
  the substratum.

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Figure 34.4 Diversity among the Echinoderms
(Part 1)
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Echinoderms Pentaradial Symmetry

• Most of the surviving echinoderms are members of
  the eleutherozoan lineage.
• The sea urchins and the sand dollars (class
  Echinoidea) lack arms but they share a five-part
  body plan with all other echinoderms.
• Sea urchins are hemispherical animals covered
  with spines attached to an underlying skeleton.
• Sand dollars are flattened or disc-shaped animals
  that feed on algae and fragments of organic
  matter on the seafloor.

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Figure 34.4 Diversity among the Echinoderms
(Part 2)
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Echinoderms Pentaradial Symmetry

• The class Holothuroidea, the sea cucumbers, have
  tube feet that are used primarily for attaching
  to a substrate rather than for moving.
• They have anterior tube feet that are modified
  into tentacles used for feeding.
• The body of sea cucumbers is oriented differently
  from other echinoderms. The mouth is anterior and
  the anus is posterior, not ventral and dorsal as
  in other echinoderms.

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Figure 34.4 Diversity among the Echinoderms
(Part 3)
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Echinoderms Pentaradial Symmetry

• The sea stars (class Asteroidea) are the most
  familiar echinoderms.
• Their tube feet serve as organs of locomotion and
  sites for gas exchange.
• Tube feet are moved by expansion and contraction
  of circular and longitudinal muscles in the tube.
• Sea stars are important predators in many marine
  environments, preying on polychaetes, gastropods,
  bivalves, and fishes.

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Figure 34.4 Diversity among the Echinoderms
(Part 4)
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Echinoderms Pentaradial Symmetry

• The brittle stars (class Ophiuroidea) are similar
  in structure to the sea stars, but they have
  flexible arms that are composed of jointed hard
  plates.
• Most feed by ingesting particles from the
  surfaces of sediments and assimilating the
  organic material from them, although some feed by
  capturing small animals.
• Unlike most other echinoderms, they have only one
  opening to the digestive tract.

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Figure 34.4 Diversity among the Echinoderms
(Part 5)
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Chordates New Ways of Feeding

• The phylum Chordata is the second major lineage
  of deuterostomes.
• This phylum evolved several different
  modifications of the coelomic cavity that
  provided new ways for capturing and handling
  food.
• They also evolved a different body plan
  characterized by an internal dorsal supporting
  structure.
• The pharyngeal slits that originally served as
  sites for gas exchange and eliminating water
  became enlarged in the chordates.

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Chordates New Ways of Feeding

• Number of Species 49,530
• Notable Features Bilateral symmetry complete
  gut coelomate.
• Dorsal, hollow or tubular nerve cord
  cartilaginous notochord..
• Pharyngeal gill slits.
• Larval tunicates have nerve cord, notochord, tail
  and gill slits.
• Adult forms retain only gill slits. Lancelets
  resemble larval sea squirts with the addition of
  myotomes (muscles).
• In vertebrates the notochord is replaced by the
  vertebal column or backbone and there is cranial
  brain development.

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Figure 34.7 Lancelets (Part 1)
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Figure 34.7 Lancelets (Part 2)
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Chordates New Ways of Feeding

• In the lineage that gave rise to the vertebrates
  (subphylum Vertebrata), the enlarged pharyngeal
  basket came to be used to extract prey from mud.
• The vertebrates have a jointed, dorsal vertebral
  column that replaced the notochord as their
  primary support.

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Figure 34.8 A Current Phylogeny of the
Vertebrates
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Chordates New Ways of Feeding

• The following traits characterize the vertebrate
  body plan
• A rigid internal skeleton, with the vertebral
  column as the anchor that provides support and
  mobility
• Two pairs of appendages attached to the vertebral
  column
• An anterior skull with a large brain
• Internal organs suspended in a large coelom
• A well-developed circulatory system, driven by
  contractions of a ventral heart

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Figure 34.9 The Vertebrate Body Plan
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Chordates New Ways of Feeding

• Filter-feeding ancestral vertebrates lacked jaws
  and gave rise to the jawless fishes.
• The ostracoderms were a group of jawless fishes
  that evolved a bony external armor that protected
  them from predators.
• The hagfishes and the lampreys are the only
  jawless fishes (class Agnatha) to survive beyond
  the Devonian period. They have tough skins
  instead of external armor.
• They lack paired appendages and have a round
  mouth that acts as a sucking organ by attaching
  to their prey and rasping at its flesh.

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Figure 34.10 Modern Jawless Fishes (Part 1)
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Figure 34.10 Modern Jawless Fishes (Part 2)
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Chordates New Ways of Feeding

• Many new kinds of fishes evolved during the
  Devonian period.
• Members of one lineage evolved jaws from some of
  the skeletal arches that supported the gill
  region.
• Jaws allowed fish to catch and subdue relatively
  large, living prey. The ability to chew aided in
  chemical digestion.

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Figure 34.11 Jaws from Gill Arches
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Chordates New Ways of Feeding

• The cartilaginous fishes (class Chondrichthyes)
  became abundant during the Devonian period.
• They include the sharks, skates and rays, and
  chimaeras.
• They have a skeleton composed entirely of a firm
  but pliable material called cartilage.
• Their skin is flexible and leathery the loss of
  external armor increased their mobility and their
  ability to escape from predators.

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Figure 34.12 Cartilaginous Fishes (Part 2)
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Chordates New Ways of Feeding

• Pairs of unjointed appendages called fins control
  swimming.
• These fins include the pectoral, pelvic, and
  dorsal fins.
• Sharks move forward by means of their tail and
  pelvic fins.
• Skates and rays propel themselves by means of
  undulating movements of their enlarged pectoral
  fins.
• Nearly all cartilaginous fishes live in the
  oceans.

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Figure 34.12 Cartilaginous Fishes (Part 1)
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Chordates New Ways of Feeding

• Class Osteichthyes - bony fish
• Notable Features
• Bony skeleton.
• Bony operculum covering gill.
• Two chambered heart swim bladder scales, mucous
  secretions to reduce friction.
• Paired pectoral and pelvic fins

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Chordates New Ways of Feeding

• The early ray-finned fishes evolved gas-filled
  sacs to supplement the action of gills in
  respiration, enabling them to live in areas where
  oxygen was periodically in short supply.
• In most species, these lunglike sacs evolved into
  swim bladders, which serve as organs of buoyancy.
• Some fishes form large aggregations, called
  schools, in open waters.
• Many species perform complex behaviors.

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Figure 34.13 Diversity among Ray-Finned Fishes
(Part 1)
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Figure 34.13 Diversity among Ray-Finned Fishes
(Part 2)
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Figure 34.13 Diversity among Ray-Finned Fishes
(Part 3)
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Figure 34.13 Diversity among Ray-Finned Fishes
(Part 4)
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Colonizing the LandObtaining Oxygen from the Air

• The evolution of lunglike sacs in response to the
  inadequacy of gills for respiration in
  oxygen-poor waters set the stage for the invasion
  of land.
• Some bony fishes were able to supplement their
  gills with lung sacs when oxygen levels were low.
• This ability allowed them to breathe air and to
  leave the water temporarily.

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Colonizing the LandObtaining Oxygen from the Air

• The amphibians (class Amphibia) arose during the
  Devonian period.
• The jointed fins of their ancestors evolved into
  walking legs.
• Finlike legs probably allowed Devonian
  predecessors of amphibians to crawl from one body
  of water to another.
• Eventually they evolved the ability to live on
  dry land.
• Most amphibian species have small lungs and
  exchange gases through their skin, and are
  confined to moist environments.

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Colonizing the LandObtaining Oxygen from the Air

• There are about 4,500 species of amphibians alive
  on Earth today.
• The living amphibians are divided into three
  orders
• Order - Caudata - Salamanders, Newts
• Order Anura - Frogs, Toads
• Class Reptilia - Reptiles
• Most species live in water at some time in their
  lives.

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Figure 34.15 Diversity among the Amphibians
(Part 1)
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Figure 34.15 Diversity among the Amphibians
(Part 2)
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Figure 34.15 Diversity among the Amphibians
(Part 3)
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Colonizing the LandObtaining Oxygen from the Air

• In a typical amphibian life cycle, adults spend
  part of all of their time on land, but return to
  fresh water to lay eggs.
• Amphibian eggs can only survive in moist
  environments.
• Fertilized eggs develop into larvae that live in
  water until they undergo metamorphosis to an
  adult.
• Some amphibians are entirely aquatic, others
  entirely terrestrial.

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Figure 34.16 In and Out of the Water
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Colonizing the LandObtaining Oxygen from the Air

• Two morphological changes contributed to the
  ability of one vertebrate lineage to control
  water loss and exploit a wider variety of
  terrestrial habitats
• The evolution of an egg with a shell impermeable
  to water
• A combination of traits that reduced water loss,
  such as skin that is impermeable to water and
  kidneys that could excrete concentrated urine
• The vertebrates that evolved these traits are
  called amniotes.

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Colonizing the LandObtaining Oxygen from the Air

• Amniote eggs have a calcium-impregnated shell
  that prevents the evaporation of fluids inside
  but allows O2 and CO2 to pass through.
• These eggs store large quantities of yolk that
  allow the embryo to attain a relatively advanced
  state of development before it hatches.

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Figure 34.17 An Egg for Dry Places
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Colonizing the LandObtaining Oxygen from the Air

• The reptiles (class Reptilia) are an early
  amniote lineage that arose from the tetrapods
  during the Carboniferous period.
• Although called a class, the reptiles are a
  paraphyletic group.
• Some species have eggs that do not develop shells
  and are retained inside the females body until
  they hatch. Some of these species evolved
  placentas that nourish the developing embryos.
• Reptiles have skin covered with horny scales that
  reduce water loss, exchange gas by the lungs, and
  have a heart divided into chambers that separate
  oxygenated from unoxygenated blood.

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Figure 34.18 The Reptiles Form a Paraphyletic
Group
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Figure 34.19 Reptilian Diversity (Part 1)
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Colonizing the LandObtaining Oxygen from the Air

• The subclass Squamata includes lizards, snakes,
  and the amphisbaenians, a group of legless
  burrowing animals with greatly reduced eyes.
• The tuataras (subclass Sphenodontida) are a
  sister group to the lizards. This group was
  diverse in the Mesozoic, but only two species
  exist today.
• Sphenodontids resemble lizards but differ in
  anatomical features.

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Figure 34.19 Reptilian Diversity (Part 2)
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Colonizing the LandObtaining Oxygen from the Air

• The crocodilians (subclass Crocodylia) are
  confined to tropical and warm temperate
  environments.
• They spend much of their time in water but build
  nests on land or on floating piles of vegetation.
• Order Chelonia - turtles, tortoises

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Figure 34.19 Reptilian Diversity (Part 3)
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Colonizing the LandObtaining Oxygen from the Air

• The dinosaurs dominated terrestrial environments
  from 215 mya until about 65 mya.
• The ability to breathe and run simultaneously was
  a major innovation in the evolution of
  terrestrial vertebrates.
• In the lineages leading to the mammals,
  dinosaurs, and birds, the legs assumed a vertical
  position.
• Muscles that enabled the lungs to be filled and
  emptied while the limbs moved also evolved.
• These muscles are present in living birds and
  mammals, and their existence can be inferred in
  dinosaurs from their fossils.

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Colonizing the LandObtaining Oxygen from the Air

• Dinosaur fossils recently discovered in China
  show that in some small predatory dinosaurs, the
  scales had been highly modified to form feathers.
• Microraptor gui had feathers on all four limbs,
  very similar in structure to modern bird feathers.

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Figure 34.20 Mesozoic Birds and Their Ancestors
(Part 1)
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Birds More Feathers and Better Flight

• A dinosaur lineage gave rise to the birds
  (subclass Aves) during the Mesozoic era.
• The oldest known avian fossil is Archaeopteryx,
  (150 mya) which had feathers virtually identical
  to those of modern birds.
• Archaeopteryx also had well-developed wings, a
  wishbone, and typical perching bird claws.
• Another early bird known only from fossils is
  Confuciuornis sanctus fossilized remains were
  discovered in 120125-million-year-old fossil
  beds in China.

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Figure 34.20 Mesozoic Birds and Their Ancestors
(Part 2)
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Figure 34.20 Mesozoic Birds and Their Ancestors
(Part 3)
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Birds More Feathers and Better Flight

• Most paleontologists believe that birds evolved
  from terrestrial bipedal dinosaurs that used
  their forelimbs for capturing prey.
• These dinosaurs may have initially developed
  feathers for insulation or display, and
  eventually were able to become airborne for short
  distances.
• There are about 9,600 species of birds today,
  ranging in size from the 2-gram bee hummingbird
  to the 150-kilogram ostrich.

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Class Aves

• Class Aves - Birds
• Notable Features
• Four chambered heart.
• Scales modified into feathers.
• Internal fertilization.
• Hard amniotic eggs.
• Wings.
• Endothermic.
• Hollow bones

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Figure 34.21 Diversity among the Birds (Part 1)
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Figure 34.21 Diversity among the Birds (Part 2)
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Figure 34.21 Diversity among the Birds (Part 3)
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Figure 34.21 Diversity among the Birds (Part 4)
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Birds More Feathers and Better Flight

• As a group, birds eat almost all types of animal
  and plant material.
• They serve as a major agent of seed dispersal by
  eating the seeds of plants.
• Feathers function not only in flight, but also in
  thermoregulatory and display functions.
• The bones of birds are modified for flight they
  are hollow and have internal struts for strength.
• The breastbone forms a large, vertical keel to
  which pectoral muscles are attached. These
  muscles pull the wings downward during the
  propulsive movement in flight.

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Birds More Feathers and Better Flight

• Flight is metabolically expensive, and thus birds
  have very high metabolic rates.
• As a consequence, they generate large amounts of
  heat, whose loss is controlled by feathers that
  can trap or release warm air.
• Birds have an enlarged cerebellum, the center of
  sight and muscular coordination.
• Most birds lay eggs in a nest, where the young
  are usually cared for by the parents after
  hatching.

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The Origin and Diversity of Mammals

• Mammals (class Mammalia) appeared in the early
  part of the Mesozoic era.
• Notable Features
• Four chambered heart.
• Fur or hair.
• Internal fertilization.
• Mammary glands.
• Endothermic
• Small mammals coexisted with reptiles and
  dinosaurs for at least 150 million years.
• Todays mammals range in size from tiny shrews
  and bats that weigh only 2 grams to the
  endangered blue whale, which can measure up to 33
  meters long and weigh up to 160,000 kilograms.

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The Origin and Diversity of Mammals

• Skeletal modifications accompanied the evolution
  of the small mammals from their larger reptilian
  ancestors
• Bones from the lower jaw were incorporated into
  the middle ear, leaving a single bone in the
  lower jaw.
• The number of bones in the skull was decreased.
• The bulk of the limbs and the bony girdles from
  which they are suspended were reduced.
• Mammals have fewer teeth than reptiles, but
  mammal teeth are more differentiated.

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The Origin and Diversity of Mammals

• Skeletal features are readily preserved as
  fossils, so these developments can be traced in
  the fossil record.
• Soft parts of animals are seldom fossilized
  thus, it is difficult to tell when mammalian
  features such as mammary glands, sweat glands,
  hair, and a four-chambered heart evolved.
• The mammals are unique in providing their young
  with milk secreted by mammary glands.
• Mammalian eggs are fertilized within the females
  body, and prior to birth, embryos undergo a
  period of development called gestation within a
  uterus.

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The Origin and Diversity of Mammals

• The approximately 4,000 species of living mammals
  are divided into two major subclasses
  Prototheria and Theria.
• The subclass Prototheria contains a single order,
  the Monotrema, which contains only three species.
  
• The monotremes differ from other mammals in that
  they lack a placenta, lay eggs, and have legs
  that poke out to the side.

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Figure 34.22 Monotremes
81
The Origin and Diversity of Mammals

• Two major groups of mammals, the marsupials and
  the eutherians, are members of the subclass
  Theria.
• Females of the group Marsupialia have a ventral
  pouch in which they carry and feed their
  offspring.
• Gestation in marsupials is short early stages of
  offspring development take place in the pouch.
• There are about 240 living species of marsupials.

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Figure 34.23 Marsupials (Part 1)
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Figure 34.23 Marsupials (Part 2)
84
The Origin and Diversity of Mammals

• Most living mammals are eutherians.
• Eutherians are more highly developed at birth
  than marsupials, and no external pouch houses
  them after birth.
• There are about 4,000 living species of
  eutherians in 16 different groups.

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Figure 34.24 Diversity among the Eutherians
(Part 1)
86
Figure 34.24 Diversity among the Eutherians
(Part 2)
87
Figure 34.24 Diversity among the Eutherians
(Part 3)
88
Primates and the Origin of Humans

• Humans belong to another eutherian lineage, the
  primates.
• The primates likely descended from small
  tree-living insectivores during the Cretaceous
  period.
• A nearly complete fossil found in Wyoming of an
  ancient primate species, Carpolestes, dates to 56
  mya.
• This early primate had grasping feet with an
  opposable big toe that had a nail rather than a
  claw.
• These grasping limbs are one of the major
  adaptations that distinguish primates from other
  animals.

89
Primates and the Origin of Humans

• The primate lineage split into two main branches
  early in its evolutionary history the prosimians
  and the anthropoids.
• The prosimians include the lemurs, pottos, and
  lorises.
• The mainland prosimian species are arboreal and
  nocturnal.
• Diurnal and terrestrial prosimian species are
  present on the island of Madagascar.

90
Figure 34.25 A Current Phylogeny of the Primates
91
Figure 34.26 Prosimians
92
Primates and the Origin of Humans

• The anthropoids include the tarsiers, monkeys,
  apes, and humans.
• They evolved from an early primate lineage about
  55 mya in Africa or Asia.
• The New World monkeys probably reached South
  America from Africa when those two continents
  were still touching.
• All New World monkeys are arboreal many having
  long, prehensile tails.
• Old World monkeys are terrestrial and arboreal,
  but none have prehensile tails. They often live
  in social groups.

93
Figure 34.27 Monkeys
94
Primates and the Origin of Humans

• About 22 mya, the lineage leading to modern apes
  separated from other Old World primates.
• About 9 mya, members of one European ape lineage
  migrated to Africa and became ancestors of modern
  African apes and of humans.

95
Figure 34.28 Apes (Part 1)
96
Figure 34.28 Apes (Part 2)
97
Primates and the Origin of Humans

• The hominids separated from other ape lineages
  about 6 mya in Africa.
• The earliest protohominids are known as the
  ardipithecines.
• These apes had morphological adaptations for
  bipedalism.
• Bipedal locomotion frees the hands to manipulate
  objects and carry them while walking.
• It also elevates the eyes, enabling animals to
  spot predators and prey.
• Bipedal movement is more energetically economical
  than quadruped movement.

98
Primates and the Origin of Humans

• The ardipithecines gave rise to the
  australopithecines.
• The most complete fossil skeleton of an
  australopithecine was discovered in Ethiopia in
  1974 and is known as Lucy.
• Lucy is about 3.5 million years old and belongs
  to the species Australopithecus afarensis.
• Experts disagree over how many species are
  represented by the different australopithecine
  fossils that have been found, but it is clear
  that at least two distinct types lived together
  over much of eastern Africa.

99
Primates and the Origin of Humans

• Early hominidsmembers of the genus Homolived
  contemporaneously with australopithecines for
  about a half million years.
• The oldest fossils belong to the extinct species
  Homo habilis, estimated to have lived about 2
  mya.
• Homo erectus evolved in Africa about 1.6 mya and
  may have exterminated H. habilis.
• H. erectus used fire and made tools that were
  probably used for digging, capturing animals,
  cleaning and cutting meat, scraping hides, and
  cutting wood.
• H. erectus was replaced in tropical regions by
  Homo sapiens about 200,000 years ago.

100
Figure 34.29 A Current Phylogeny of Homo sapiens
101
Primates and the Origin of Humans

• Large brain size evolved in the Homo lineage as
  social lives became increasingly complex.
• The human brain has large amounts of omega-3 and
  omega-6 fatty acids, which cannot be synthesized
  they must be obtained from the diet.
• Access to fat-rich foods from aquatic
  environments may have been the key factor that
  supported the expansion of the human brain.
• The archeological record of the past 100,000
  years includes large piles of mollusk shells and
  fish bones, as well as carved points used for
  fishing, supporting this idea.

102
Primates and the Origin of Humans

• Several Homo species existed during the
  mid-Pleistocene epoch and were skilled hunters of
  large mammals.
• H. neanderthalensis was widespread in Europe and
  Asia between 75,000 and 30,000 years ago. They
  hunted large mammals and made a variety of tools.
• Many scientists believe that they were
  exterminated by the H. sapiens known as the
  Cro-Magnons.
• Cro-Magnon people spread across Asia and reached
  North America perhaps as early as 20,000 years
  ago.

103
Figure 34.30 Hunting Inspires Art
104
Primates and the Origin of Humans

• The evolution of larger brains increased the
  behavioral capacity of our ancestors, especially
  the capacity for language.
• Our expanded mental abilities are largely
  responsible for the development of culture, the
  process by which knowledge and traditions are
  passed from one generation to another by teaching
  and observation.
• Cultural learning greatly facilitated the spread
  of domesticated plants and animals.
• Human societies converted from those that were
  based on hunting and gathering to those that were
  pastoral and agricultural.

105
Deuterostomes and ProtostomesShared
Evolutionary Themes

• Deuterostome evolution paralleled protostome
  evolution in several ways.
• Both groups exploited abundant food in soft
  marine sediments attached to rock or suspended in
  water.
• In lineages of both groups, the body became
  compartmentalized.
• Planktonic larval stages evolved in both groups.
• Both groups colonized the land, but the internal
  skeletons of deuterostomes were able to support
  much larger animals.
• The terrestrial deuterostomes recolonized aquatic
  environments a number of times.