Bio 215 Chapter 34 Vertebrate Evolution and Diversity Ch 34 Vertebrate Evolution and Diversity



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Bio 215 Chapter 34 Vertebrate Evolution and Diversity

Ch 34 Vertebrate Evolution and Diversity
Lecture notes:

  1. Be able to describe the four unique anatomical features of chordates.

  2. Describe the specialized characteristics found in the Subphylum Vertebrata and explain how each is beneficial to the survival of the organism.

  3. List and explain the distinguishing characteristics of all the classes of Subphylum Vertebrata.

  4. Describe the difference between monotreme, marsupial and placental mammals.

  5. Describe the characteristics found in early primates.




  1. Vertebrates belong to the phylum Chordata




  1. This phylum contains 3 subphyla

  1. Urochordata

  2. Cephalochordata

  3. Vertebrata

  1. Characteristics of Chordates (deuterostomes)(appear at some time in the organisms life)

  1. Notochord = longitudinal, flexible rod between gut and nerve cord

  1. present in all chordate embryos

  2. extends through the length of the animal as a simple skeleton

  3. in higher vertebrates this cord becomes intervertebral disks

  1. Dorsal, Hollow nerve Cord

  1. unique to chordates

  2. central nervous system (brain, spinal cord) develops from this

  1. Pharyngeal Slits (posterior to mouth, opens to outside of animal)

  1. permits water to exit before the digestive system

  2. suspension feeding in invertebrate chordates

  3. became modified for gas exchange in higher vertebrates

  1. Muscular Postanal Tail

  1. extends beyond the anus, used for locomotion




  1. Invertebrate chordates provide clues to origin of vertebrates

  1. Subphylum Urochordata (Tunicates) sea squirts

  1. most are planktonic, marine animals which adhere to rocks

  2. Most are filter feeders

  3. Adult forms:

  1. lack notochord, nerve cord and tail

  2. posses only pharyngeal slits

  1. Larva (immature) forms:

  1. Are free swimmers and have all four chordate characteristics

  2. attach by head to a surface and undergo metamorphosis

5) the Manx gene (after the tailess cat) is required for the tail to form.

  1. Subphylum Cephalochordata (lancelets)

  1. adult characteristics

  1. Have all 4 chordate characteristics

  1. marine filter feeders (mucus net, cilia move food to mouth, water exits)

  2. burrow tail first into sand only mouth shows

  3. Move with fish like motions, but swim poorly

  4. Segmentation developed independently of annelids and arthropods (in debate)

  1. Relationship of invertebrate chordates to vertebrates

  1. first fossils were found in Cambrian rocks 550mya

  2. vertebrate ancestors possessed all four chordate characteristics and were suspension feeders

  1. similar in shape to lancelets

  1. urochordates were progenitors to Cephalochordates and vertebrates

  1. Paedogenesis = early sexual maturity in larvae

  2. This is the reason why we do not have metamorphosis in vertebrae life cycle




  1. The evolution of vertebrate characteristics is associated with increased size and activity

  1. The vertebrate body plan retained chordate features with added specialization’s

  1. greater degree of cephalization (brain and sense organs near the anterior, which contacts environment sooner)

  2. skeleton including cranium and vertebral column replaces notochord

  1. axial skeleton made larger size and stronger faster movement possible

  1. Skeleton composed of bone and/or cartilage

  1. skeleton can grow with the organism, unlike arthropods

  2. protects brain, allows movement.

  3. made for stronger faster organisms

  4. most have ribs and an appendicular skeleton with two pairs of appendages.

  1. neural crest group of embryonic cells found only in vertebrate embryos

  2. respiration and circulation develop to support the mitochondria of muscles and other active tissues

  3. vertebrates have a closed circulatory system with a ventral chambered heart (2 to 4)

  4. Have an increased efficiency of digestion (peristalsis muscles move food along the digestive system.




  1. 1. vertebrate diversity and phylogeny

  1. Vertebrates are divided into two major groups (superclasses

  1. Superclass Agantha whos members lack jaws.

  2. Gnathastomata members possess jaws. are divided into 6 classes

  1. Chondrichthyes

  2. Osteichthyes

  3. Amphibia

  4. Reptilia

  5. Aves

  6. Mammalia

  1. the last 4 are tetrapods= animals possessing two pairs of limbs that support it on land.

  2. other adaptations for a terrestrial lifestyle not found in amphibians are

  • amniotic egg (a shelled, water resistant egg) allows completion on fhte life cycle on land.

  • most mamals do not lay eggs bru retain other featurs of the amniotic condition, so they are still considered amniotes.

5. Superclass Agantha: Agnathans (jawless vertebrates) 400-500 million years old

  1. Are represented by the earliest fossils some characteristics include: ( about 60 species)

  1. small 50cm in length

  2. jawless, slitlike mouths, bottom dwellers, no paired fins

  3. armor plated ostracoderms became extinct

  4. mostly filter feeders, trapped organic debris in gill slits

  1. Lampreys eel-shaped , feed by clamping mouth onto live fish

  1. use rasping tongue to make wound and feed on blood

  2. spend larval development in freshwater streams, migrate to larger water when mature

  3. larvae are suspension feeders that resemble lancelets

  4. some feed only as larvae

  1. Hagfishes (look like lampreys)

  1. scavenger without rasping mouthparts

  2. lack a larval stage and are entirely marine

  3. the only vertebrate that is a true osmoconformer




  1. The extinct class placoderms replaced Agnathans, armored fishes with jaws and paired fins

  1. paired fins enhanced swimming, jaws allowed varied feeding

  2. Evolution of jaws from modification of skeletal rods that used to support anterior pharyngeal (gill) slits

  1. remaining slits function as gills

  2. vertebrates work in up and down, arthropods work form side to side

  1. gave rise to early sharks (Chondrichthyes) and bony fish

Superclass Gnathostomata: The fishers

The agnathans wer gradully replaced by vertebrtates with jaws (late silurian and early devonian)



  • vertebrate jwas evolved form skeletal supports of the pharyngeal slits.

  • evolved independantly of arthropods (whose jaws work in a side to side motion)




  1. Chondrichthyes: cartilaginous fishes with adaptations for powerful swimming (750 species)




  1. flexible skeletons of cartilage, well developed jaws, paired fins

  1. ancestors had bony skeletons

  2. initial skeleton does not become ossified

  3. cartilage is more elastic, and lighter than bone

  1. Sharks: stream lined bodies for fast swimming

  1. tail provides propulsion

  2. Dorsal fins are stabilizers

  3. pectoral and pelvic fins produce lift

  4. buoyancy due to oil in liver

  5. swim continuously, otherwise sink

(1) keep water flowing over gills

  1. most are carnivorous, largest is filter feeder

(1) teeth evolved as modified scales

(2) short digestive tract

(3) has spiral valve to slow food movement increase surface area


  1. Shark sensory options

  1. sharp vision (not color)

  2. olfactory system well developed

  3. Electric sensory regions detect muscle contractions of prey

  4. lateral line system, detect water pressure changes and vibrations

  5. auditory organs (pair) detect sound waves

  1. Shark reproduction

  1. claspers on pelvic fins of males transfers sperm into female reproductive tract

  2. have cloaca (common chamber for reproductive, digestive and excretory systems)

  3. egg laying to live births

  1. Rays

  1. adapted to bottom dwelling life style

  2. dorsoventrally flattened bodies

  3. jaws crush mollusks and crustaceans

  4. pectoral fins provide propulsion for swimming

  5. tail is whiplike and has barbs




  1. Osteichthyes bony fishes are most abundant and diverse (over 30,000 species)

  1. Some characteristics of this class

  1. Abundant in Marine and fresh water

  2. skeleton is bony, reinforced with a matrix of calcium phosphate

  3. skin is covered with flattened bony scales

  4. skin glands produce mucus that reduces drag when swimming

  1. Gas exchange

  1. draws water over 5 pairs of gills covered by an operculum

  2. swim bladder dorsal to digestive system provides buoyancy

  1. Fish sex

  1. most are oviparous and utilize external fertilization

  1. can display complex mating behavior

  1. Two subclasses that diverged at the end of the Devonian

  1. Subclass Actinopterygii

  1. have fins supported by flexible rays

  2. spread from fresh water to the seas

  3. salmon can reproduce in fresh water and mature in the ocean

  1. Subclass Sarcopterygii includes 3 orders

  1. Coelocanths- Lob finned fishes

(1) have fleshy, muscular fins that are extensions of the bony skeleton

(2) used fins to walk on bottom of the ocean, were bottom feeders

(3) only one existent species


  1. Lungfishes

(1) live in southern hemispheres

(2)live in stagnant ponds

(3) can gulp air and dig burrows to aestivate


  1. rhipidistians are all extinct

Superclass Gnathostomata: The tetrapods


  1. Amphibians are the oldest class of tetrapods (about 4000 species)

  1. Were the first to move onto land

  1. Early amphibians

  1. evolved from lobe finned fishes

  2. early amphibians were predators that ate terrestrial invertebrates

  1. Modern Amphibians (3 existing orders)

  1. Order Urodela salamanders

  1. aquatic and terrestrial forms

  2. walk with a side to side motion of the body

  3. swim sinusoidally or walk along the bottom

  1. Order Anura toads and frogs better suited for terrestrial environment than Urodela

  1. enlarged hind legs for hopping

  2. anteriorly attached tongue for capturing prey

  3. predator avoidance by camouflage or poisons

  1. Order Apoda (caecilians)

  1. legless and almost blind

  2. burrow in moist tropical soils some in streams and ponds

  1. The life cycle of a typical Anura.

  1. exhibit metamorphosis form larval to adult stage

  1. tadpole (larval stage)

(4) aquatic, herbivorous and possesses internal gills, a lateral line and long ginned tail

  1. swims by undulating it's tail

  2. during metamorphosis, legs develop and aquatic forms disappear

  1. young frog is tetrapod, has lungs and external eardrums and digestive system that can digest animal protein

  2. Adult is terrestrial semiaquatic and a predator

  1. Some species may not have tadpole stage

  2. keep close association with water

  1. must have water to reproduce

  2. must have high humidity to keep skin moist

  1. Amphibians are dioecious

  1. produce unshelled eggs that are fertilized as they are hatched by the male

  1. Some frogs exhibit parental behavior, and produce fewer eggs

2. Evolution of the amniotic egg



  1. Development of amniotic egg breaks the ties with the aquatic environment

  2. Extraembryonic membranes develop from tissues layers of the embryo

  1. specialized membranes function in gas exchange, transfer stored nutrients to embryo, and store waster

  2. the amnion forms a closed compartment that bathes the embryo and provides cushion against shock

  1. Birds and mammals developed form reptiles,



  1. reptilian heritage is evident in all amniotes

  1. reptiles possess several adaptations to live on land not found in amphibians, and shared by other terrestrial animals

  2. are defined byt the absence of features that distinguish birds (feathers) and mammals (hair and mammary glands)

  1. Reptilian adaptations

  1. scales with keratin help prevent dehydration

  2. gas exchange via the lungs

  3. Dioecious with sexual reproduction and internal fertilization

  1. most are oviparous and produce an amniotic egg

  2. some are viviparous and have a form of a placenta

  1. Ectotherms = use behavior to absorb solar energy and regulate its body temp(body heat from external sources)

  1. have a much lower energy requirement than endotherms




  1. The age of the reptiles (Mesozoic era) (300 mya)

  1. Origin and Early evolution

  1. evolved form Devonian amphibians

  2. were dominant terrestrial vertebrates for 200 million years

  3. reptilian radiation gave rise to two main evolutionary branches

  1. Synapsids

  • gave rise to therapsid line (mammalian like reptiles

  • dog sized predators

  1. Sauropsids

  • gave rise to modern amniote groups

  1. i) anapsids (turtles)

  2. ii) Diapsids (everything else including dinosaurs

  1. The Dinosaurs

  1. late Triassic when several lineages of giant reptiles evolved

  2. Two groups were important

  1. Dinosaurs

  2. pterosaurs (flying reptiles)

  1. developed Endothermy = ability to keep the body warm through the animals own metabolism

  2. Became extinct during the cretaceous (65mya) period due to a number of hypothesis

  1. climate becomes cooler and more variable

  2. asteroid kills everything

  1. dino AIDS ect, Mammals eat all the dino eggs

  1. Modern reptiles

  1. order chelonia evolved form anapsids

  1. little change, still a turtle

  2. protected form predators by a hard shell

  3. all turtles lay their eggs on land

  1. Order Squamata Lizards and snakes

  1. Lizards

  1. diapsid lineage

  2. most are small

  3. nest in crevices and decrease activity during cold periods

  1. Snakes (descendants of burrowing lizards)

  1. limbless

  2. vestigial pelvic and limb bones in primitive snakes are evidence of a limbed ancestor

  3. are hunters that have many adaptations for detecting prey

  • acute chemical sensors

  • can detect ground vibrations

  • have heat detecting organs

  • can inject poisons into their prey

  1. Crocodiles

  1. evolved form diapsid lineage

  2. spend most of their time in water

  3. confined to warm regions

  4. are largest and most closely related to dinosaurs




  1. Birds began as flying reptiles (amniotic egg and scales on legs)

  1. Characteristics of birds

  1. anatomy is modified to enhance flight

  1. bones are hollow and honeycombed to retain strength

  2. organ systems reduced (one ovary in females)

  3. no teeth, beak made of keratin

  1. active metabolism to produce energy for flight

  1. endothermic with insulating feathers and fat

  2. four chambered heart segregates oxygenated from unoxygenated blood

  3. efficient lungs

  1. well developed nervous system

  1. acute vision to aid in flying

  2. complex behavior especially during the breading season

  1. Bird reproduction

  1. Dioecious with sexual reproduction and internal fertilization

  2. sperm transferred form cloaca of male to female cloaca

  3. eggs are kept warm through breeding

  1. Wings are airfoils formed by shape and arrangement of feathers

  1. feathers make of keratin and are light and strong

  1. evolved from scales of reptiles

  1. advantages to adaptations to flight

  1. aerial reconnaissance enhances hunting and scavenging

  2. feed on flying insects

  3. escape mechanism

  4. migration to utilize different food resources

  1. Origin of Birds

  1. birds shared a common ancestor with Archaeopteryx lithographica

  2. clawed forelimbs, teeth and long tail with vertebra and feathers

  3. birds did not evolve from Archaeopteryx, but have a shared ancestor that has not been discovered

  1. Modern birds

  1. ratites

  1. flightless birds, lack the breastbone and large pectoral muscles

  1. carinates

  1. have sternal keel (carina) that supports the large pectoral flying muscles

  2. most birds belong to this class including penguins




  1. Mammals diversified at the end of the Cretaceous period

  1. Mammalian characteristics

  1. posses hair made of keratin: provides insulation

  2. Endotherms with an active metabolism

  1. diaphragm for ventilation of lungs that support metabolism

  2. four chambered heart segregates oxygenated and unoxygenated blood

  1. Mammary glands produce milk to nourish the young

  2. Teeth are differentiated and adapted to many types of food

  3. Dioecious with sexual reproduction and internal fertilization

  1. viviparous with embryo receiving nutrients from the female across the placenta

  2. a few are oviparous

  1. Have large brains and are capable of learning

  1. parental care is long allowing the young to learn from the parents

  1. Evolution of the Mammals

  1. Evolved form therapsid ancestors during Triassic

  2. coexisted with dinosaurs

  3. small insectivorous and nocturnal

  4. radiated after the mass extinction of dinosaurs at end of Mesozoic

The three major groups of mammals




  1. Monotremes

  1. characterized by platypuses and echidnas

  2. Oviparity

  3. reptilian like with large amounts of yolk that nourishes the developing embryos

  4. hair

  5. milk production, but lack nipples

  6. possibly early mammals

  7. only in Australia and New Guinea

  1. Marsupials

  1. include opossums, kangaroos, koalas and other mammals

  2. Marsupium (maternal pouch)

  3. Marsupial eggs contain a moderate amount of yolk that nourishes the embryo during the early development in the mother's reproductive tract

  4. young are born early in development

  5. must climb to marsupium

  6. in marsupium attaches to teat and completes development while nursing

  7. present in Australia and some in south America

  1. Placental mammals

  1. embryonic development is completed within the uterus where embryo is joined to mother by placenta

  2. 4 main evolutionary lines (representative orders)

  1. Chiropters (bats) and Insectivores (shrews_

  1. early mammals




  1. Medium sized herbivores that underwent a massive adaptive radiation during the Tertiary period

  1. led to

  1. Lagomorpha (rabbits)

  2. Perissodactyla (odd toed ungulates)

  3. Artiodactyla (even toed ungulates)

  4. Sirenia (sea cows)

  5. Proboscidea (elephants)

  6. Cetacea (whales, porpoises)

  1. Order Carnivors

(1) cats, dogs, raccoons, skunks and pinnipeds (sea lions, walruses)

  1. The primate rodent complex

  1. rodentia (rats, squirrels, beavers)

  2. Primates (monkeys, apes, humans)




  1. Primate evolution provides a context for understanding human origins

  1. Evolutionary Trends in Primates

  1. First primates were small, arboreal and were similar to insectivorous

  1. Primate characteristics

  1. Brachiate (swing from one limb to next) because of limber shoulder

  2. dexterous hands for manipulating foods

  3. sensitive fingers with nails not claws

  4. eyes together in front of head, good depth of vision

  5. excellent hand eye coordination

  6. parental care of single births, with long nurturing


Questions to think about:


  1. Which of the following are characteristics of the chordates

  1. A nerve cord and central nervous system

  2. A flexible rod between the gut and the nerve chord

  3. Extensions beyond the anus used for locomotion

  4. Cephalization and a central nervous system

  5. One structure for taking in food and water with slits posterior to the mouth that remove water allowing for suspension feeding.

  1. Which of the following characteristics that provided the vertebrates the ability to increase their size and activity?

  1. A skeleton made of bone and cartilage that could grow with the organism

  2. Mitochondria that would work under very low oxygen conditions.

  3. A closed circulatory system with a multichambered heart.

  4. External digestion

  5. Simple cephalization

  1. Which of the following lists contain all of the classes that make up subphylum vertebrata.

  1. Agnatha, Osteichthyes, Chondrichthyes, Amphibia, Reptilia, Aves, Mammalia

  2. Agnatha, Ossicles, Chondrichthyes, Amphibia, Reptilia, Aves, Mammalia

  3. Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptile, Aves, Mammalia

  4. Agnatha, Chondrichthyes, Amphibia, Reptilia, Aves, Osteichthyes, Mammalia

  5. Agnatha, Amphibia, Chondrichthyes, Aves, Reptilia, Osteichthyes, Mammalia



  1. The evolution of the amniotic egg allowed for:

  1. A link from reptiles to birds and mammals

  2. Organisms to live and reproduce far from large bodies of water

  3. Motility of sperm in an aquatic environment

  4. A closed compartment that would bathe the embryo and provide cushion against shock

  5. Extraembryonic membranes that develop from tissues of the mother

  1. If an organism is to fly, it must reduce its weight as much as possible. Which of the following are adaptations that birds have used to reduce their weight

  1. Bones are reduced or not present

  2. Reduce the number of redundant organ systems

  3. Replace hard substances in the body with hollow lighter keratin

  4. Reduce the number of teeth

  5. Make bones hollow and honeycombed for strength.

3) C, 4) A,B,D 5) B,C,E



Ch 34 p.(1





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