Ch. 34 -  Vertebrates – Part 1

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540 mya, lots of animals in oceans;  2 cm long animal with vertebrae swam in the oceans.  About 360 mya, evolution of legs and feet in one lineage of vertebrates allowed move to land.  (herps).  There are about 52 k spp of vertebrates on earth, but largest, most wide ranging, tools, language, music, etc.  (Fig. 34.2)

   I.  Phylum Chordata- our phylum.  all are bilateral, and deuterostomes. 

            A.  4 distinctive features in embryos

                        1.  dorsal hollow nerve cord

                        2.  notochord - flexible longitudinal rod btn digestive tract and nerve cord

                        3.  gill structures-  or pharyngeal gill slits in pharynx, region of digestive tube behind mouth

                        4.  post anal tail (posterior to anus).  (Fig. 34.3)

                                    a.  vertebrates - subphylum of chordates

                                    b.  invertebrates

                                                1). tunicates- Phylum Urochordata.  large gill apparatus; adhere to rocks and boats.

                                                tunicate larvae exhibit the above 4.   Eat fine organic matter caught by mucus

                                                around gills

                                                2).  lancelets- Phylum Cephalochordates - marine chordates- feed on suspended

                                                particles;  have segmented muscles to flex body side to side.  Gill apparatus traps

                                                food.  (organic food particles get trapped in mucous surrounding gills. somites are

                                                muscle segments fund alsong each side of the notochord in all chordate embryos

II.  Craniates are chordates with a head

            A.  Derived characters of craniates

                        1.  2 clusters of hox genes - lancelets and tunicates have only 1

                                    a.  additional genes added lots of complexity

                        2.  neural crest - collection of cells  in dorsal margins of closing neural tube in embryo

                                    a.  cells of crest disperse thru out embryo, give rise to teeth, bones, skull cartilage, sense

                                    organs, several types of neurons

                        3.  pharyngeal slits evolved into gill slits- actively pump to suck in food, facilitate gas exchange

                        4.  craniates are more active , have higher metabolism and much more extensive musculature,

                        some of which aid digestion

                                    a.  craniate hearts have at least 2 chambers, rbcs and hemoglobin, and kidneys

            B.  Myxini - hagfishes : have skulls but  no jaws

                        1.  retain notochord, no vertebrae

                        2.  small brains, eyes ears and nasal opening;  toothlike structure made of keratin

                        3.  all are marine, feed on worms or dead fish

                        4.  slime glands repulse predators - up to several liters of slime in less than a minute

                        5.  coats gills of attacking fish

                        6.  not really fish

III.  Vertebrates- craniates w/ a backbone

            A. skull and backbone- repeating segments called vertebrae.  Skeleton encloses main part of

            nervous system

            1.  most vertebrates have skeletal parts supporting appendages; made of bone and/or cartilage; 

            mostly nonliving cells, but some are living to secrete nonliving material, so skeleton can grow

            with the animal, unlike arthropods nonliving skeleton which must be shed.

                        2.  family of genes evolved shared by all vertebrates - Dlx- assoc. w/ more extensive skull and

                        vertebrae

                        3.  some are prongs of cartilage, in most vertebrates, bone surrounds nerve cord

                        4. replaced mechanical function of notochord

            B.  Cephalospidomorphi - lampreys - represent oldest lineage of vertebrates

                        1.   marine and freshwater

                        2,  parasitic - clamp round, jawless mouth onto a fish;  rasp with tongue and suck blood

                        3. have a notochord and cartilaginous vertebrae

IV.  Gnathostomes are vertebrates that have hinged jaws

            A.  jaws help animals grip food items and slice them up (Fig. 34.13)

                        1.  origins of jaws - hypothesis  that they derived from structures holding phayngeal gill slits

                        2.  jaws evolved from skeletal rods supporting the gills- hinged mouths allow wide variety                  

                        of prey, not just feeding on suspended particles

            B.  Chondrichthyes - (cartilage fish) sharks, rays and relations

                        1.  skeleton is composed primarily of cartlage, often impregnated with calcium

                                    a.  dorsal fin functions as stabilizer,  pectoral and pelvic fins provide lift

                                    b.  less buouyant than water, swim continually or will sink

                                    c. continuous swimming ensures water flowing over gills

                                    d.  if resting on seafloor, use muscles of jaws and pharynx to pump water

                        2.  largest sharks and rays are suspension feeders that consume plankton

                        3.  most are predators

                                    a.  sharp vision, can’t distinguish colors

                                    b.  nostrils only for smelling, not breathing; great sense of smell

                                    c.  electric sensors in heads for detecting other fish’s muscle contractions

                                    d. sounds transmitted to hearing organs w/ entire body

                                    e. lateral line system:  along side of body; can detect change in water pressure-                                                           animals swimming nearby

                                    f.  shark eggs fertilized internally-

                                                1.  oviparous - lay eggs to hatch outside of body

                                                2.  ovoviparous - retain fertilized eggs in oviduct; young nourished by egg yolk

                                                3.  a few are viviparous - fertilized by mother’s placenta, born live

                                    g.  cloaca- chamber for excretion of digestive and reproductive products

                        4.  have changed little in 300 million yrs; but in 2003, researchers reported decline of some of 75 %

            C.  Fish- Osteichthyes - jawed vertebrates with gills and paired fins; include ray-finned and lobe-finned

            fishes.  Skeleton reinforced by hard calcium salts.

                        1.  features

                                    a.  lateral line system

                                    b.  great smell

                                    c.  excellent eyesight

                                    d.  operculum- protective flap over gill that can pass water thru gill when fish is                                                 stationary.  sharks don’t have this.

                                    e.  swim bladder- gas filled sac for buoyancy;  transfer gases to blood and back

                        2.  Class Actinopterygii -  ray finned- fins supported by thin, flexible skeletal rays - goldfish, trout, etc

                        3.  Class Actinistia - fins are rod shaped, surrounded by thick layer of muscle

                                    a.   lobe finned- fins are muscular, supported by stout bones- extinct except for coelacanth; 

                                    uses fins to waddle on ocean floor

                        4.  Class Dipnoi - lungfishes - come to surface to gulp air

V.  Tetrapods- gnathostomes with lims and feet

            A.  derived characters

                        1.  pelvic girdle attached to backbone - allows running

                        2.  gill slits in embryos give rise to ears, glands and other structures

                        3.  ears adapted for airborne sounds

            B.  Class Amphibia- mixture of terrestrial and aquatic adaptations;  part of life cycle must be completed in             water.  

                        1. Order Anura -  frogs- adult spends much time on land, lays eggs in water,

                                    a.  tadpole stage in water;  gills, lateral line system, long finned tail.

                                    b.  metamorphosis into adult- terrestrial insect eater, 4 legs, external eardrums and lungs. 

                                    No lateral lines

                        2.  Order Apoda - legless burrowing amphibians, most tropical;  adults and juves carnivores

                        3.  Order Urodela - salamanders - most on land exhibit side to side bending to walk - inherited from

                        early tetrapods

                                    a.  some aquatic, some land livers

                                    b.  adults and juveniles carnivores

                        4.  Amphibians today account for only 8% of all vertebrae, but were first terrestrial vertebrates.                               Possibly land vertebrates evolved from lobefins, who have lungs and gills; or, they evolved from                               lungfishes.  Amphibians means 2 lives- a reference to metamorphosis of many frog                                     species.  there are both terrestrial and aquatic amphibs, but their skin loses water - no                                waterproofing - used for gas exchange

            1.  some have no lungs and use diffusion exclusively

                                    a.  many have social behaviors for courtship or other purposes

                                                1.  males may sing for territory or courtship

                                                2.  migration to specific breeding sites may involve vocal communication,

                                                celestial navigation or chemical signaling

                                    b.  alarming decline -

                                                1. habitat degradation

                                                2.  spread of fungal pathogen

                                                3.  acid precipitation - amphibians require water to complete life cycle

VI.  Amniotes are tetrapods with terrestrially adapted eggs - reptiles, birds and mammals

            A.  Derived characters of amniotes

                        1.  named for amniotic egg - membranes that protect embryos

                                    a.  function in gas exchange, waste storage and transfer of stored nutrients to embryo

                                    b.  amnion itself is one of the membranes that encloses the embryo in fluid filled

                                    compartment

                                    c.  no shells on amphibian eggs, but reptiles, birds and some mammals have shells

                                                1.  birds eggs are calcareous

                                                2.  reptile eggs are leathery and flexible

                                                3.  shell slows dehydration in air; allowed amniotes to colonize lots of habitats

                                                4.  most mammals dispensed with shells, embryo develops in mother

                        2.  amniotes also have less permeable skin than amphibs, and rib cage ventilates lungs

                        3.  most other amniotes have elevated stance where amphibs splay legs out

VII.  Amniotes are tetrapods with terrestrially adapted eggs - reptiles, birds, mammals

            A.  Derived characters of amniotes

                        1.  amniotic eggs have membranes that protect embryo, keep it from drying out

                        2.  Extraembryonic- not part of the embryo - grow out from tissue layers produced by

                        embryo

                        3.  one of these, the amnion, encloses embryo in bath of fluid, acts as hydraulic shock

                        absorber

                        4.  most reptiles and some mammals have leathery eggs, while birds are calcareous

                                    a.  these shells slow dehydration

                                    b.  allow amniotes to occupy more niches

                        5.  less permeable skin than amphibs

                        6.  use of rib cage to ventilate lungs

            B.  Reptiles

                        1.  includes tuataras, lizards, snakes, turtles, crocodilians, and birds

                        2.  skin has scales  with protein keratin to prevent dehydration

                                    a.  prevent breathing through skin

                                    b. most reptiles have lungs for gas exchange, except turtles who use cloaca

                        3.  lay eggs on land;  fertilization must occur internally before shell is secreted

                        4.  ectothermic - use behavior to modify body heat

                                    a.  can survive on 10% calories of same sized mammals because of this

                        5.  skin covered with scales waterproofed with keratin (protein)                                   

                        6.  eggs covered with parchment shells to retain water- full life cycle on land

                                    a.  fluid filled sac called amnion

                                    b.  yolk- nourishment

                        7.  ectothermic- do not use metabolism to control body temperature (cold blooded)

                                    a.  sit on warm rocks

                                    b.  go into shade if it gets too hot

                        8.  historically very successful- dinosaurs

                                    a. vegetarians and carnivores

                                    b.  may have been endothermic, none left today

                        9.  snakes and lizards

                        10.  tuataras

                        11.  turtles

                        12.  crocodiles and alligators

                        13.  dinosaur lineage survives today as birds

            C.  Class Aves-  Birds - 8600 spp. Worldwide, evolved from 2 legged reptiles 150-200 mya

                        1.  closely related to reptiles, esp.  crocodilians;  modified for flying

                                    a.  females have one ovary

                                    b.  no urinary bladder

                                    c.  toothless

                                    d.  gonads disappear till breeding season

                                    e.  skull is especially light

                                    f.  feathers and wings;  feathers have keratin, found in other reptiles

                        2.  inherited scales on legs

                        3.  amniotic eggs,

                        4.  toenails containing keratin

                        5.  general body form

                        6.  feathers were derived from dinosaur scales, a few dinos had downlike feathers;  birds are                                endothermic, feathers provide insulation

                        7.  Archaeopteryx (= ancient wing, gk)

                                    a.  teeth

                                    b.  winged claws

                                    c.  tail w/ many vertebrae

                                    d.  not an ancestor of modern birds, extinct side lineage

                        8.  Birds bodies are adapted for flight

                                    a.  lack teeth (extra weight)

                                    b.  tail- few small vertebrae

                                    c.  wings lack claws

                                    d.  feathers- hollow shafts

                                    e.  bones are hollow

                                    f.  large breast (flight) muscles (white meat)

                                    g.  some soar (turkey vultures) others beat wings really fast (hummers)

                                    h.  flightless species (emu) evolved from flying ancestors

VIII.  Mammals are amiotes that produce milk and have hair - 5000 known spp.

            A.  Derived characters of mammals

                        1.  mammary glands that produce milk for offspring

                        2.  hair and fat layer under skin help mammals retain heat

                        3.  endothermic with circulatory and respiratory systems for high metabolism

                        4.  diaphragm to help ventilate lungs

                        5.  differentiation of teeth; not found in reptiles

            B.  Monotremes

                        1.  found only in Australia, NZ

                        2.  1 sp. of platypus and 2 echidnas- spiny anteaters

                        3.  lay eggs, have hair and milk, but no nipples- glands on belly of mom

                                    a.  babys suck milk from moms fur

            C.  Marsupials

                        1.  opossums, kangaroos and koalas

                        2.  marsupials and eutherians both give birth to live young

                                    a.  embryo develops inside mom’s uterus

                                    b.  placenta - tissue that delivers nutrients  to embryo from mom’s bloodstream

                                    c.  marsupials born very early in development, completes development while

                                    nursing in pouch

                                                1.  red kangaroo is about the size of honeybee when born, 33 days after

                                                fertilization

            D.  Eutherians (placental mammals)

                        1.  longer pregnancy than marsupials

                        2.  young eutherians complete development in uterus, joined to mom by placenta -

                                    a.  intimacy and connection between mom and young

                        3.  Primates - lemurs, tarsiers, monkeys and apes

                                    a.  derived characters

                                                1.  hands and feet adapted for grasping, digits have flat nails (life in trees)

                                                2.  skin ridges on hands (fingerprints)

                                                3.  large brain and short jaws- flat face

                                                4.  well developed parental care and social structure

                                                5.  mobile or opposable thumbs

                                                6.  excellent eye-hand coordination and depth perception for brachiating

VIII.  Humans are bipedal hominids with a large brain - Homo sapiens are 160,000 years old

            A.  Derived characters

                        1.  stand upright, walk on 2 legs

                        2.  much larger brain

                                    a.  capable of language

                                    b. tool use

                                    c.  symbolic thought

                        3.  reduced jaws

                        4.  shorter digestive tract

Lesson Objectives – Ch. 34 Part 1

1. Distinguish between the phyla of deuterostomes.

2. Describe the four derived traits that define the phylum Chordata.

3. Distinguish among the three subphyla of the phylum Chordata and give examples of each.

4. Explain what lancelets suggest about the evolution of the chordate brain.      

5. Explain the fate of the neural crest cells in craniate development.

6. Describe the way of life and unique characters of the lamprey.

7. Explain one hypothesis for the evolution of the jaws of gnathostomes.

8. List the shared, derived characters that characterize gnathostomes

9. Describe the features of sharks that are adaptive for their active, predatory lifestyle.

10. Describe and distinguish between Chondrichthyes and Osteichthyes, noting the main traits of each group.

11. Identify and describe the main subgroups of Osteichthyes.

12. Define and distinguish between gnathostomes, tetrapods, and amniotes.

13. Describe the common traits of amphibians and distinguish among the three orders of living amphibians.

14.  Explain why the reptile clade includes birds.

15.  Describe a number of reptile features that are adaptive for life on land

16.  Explain why non-bird reptiles should be called “ectothermic” rather than “cold-blooded.”

17.  Describe the specialized adaptations of snakes that make them successful predators.

18.  List the modifications of birds that are adaptive for flight.

19.  Summarize the evidence supporting the hypothesis that birds evolved from theropod dinosaur ancestors.

20.  Describe the characteristic derived characters of mammals

21.  Distinguish among monotreme, marsupial, and eutherian mammals.

22.  Describe the adaptive radiation of mammals during the Cretaceous and early Tertiary periods

23.  Compare and contrast the four main evolutionary clades of eutherian mammals

24.  Describe the general characteristics of primates. Note in particular the features associated with an arboreal existence.

25.  Distinguish between the two subgroups of primates and describe their early evolutionary relationship.