Vertebrate Evolution and Diversity

Chapter 34

• Vertebrates belong to phylum Chordata.

• Includes 3 subphyla, vertebrates and 2 phyla of invertebrates, urochordates and cephalochordates.

• 4 characteristics: notochord; dorsal, hollow nerve cord; pharyngeal slits; and muscular, postanal tail.

• Notochord, present in all chordate embryos - flexible rod between digestive tube and nerve cord.

• Dorsal, hollow nerve cord develops in vertebrate embryo from plate of ectoderm that rolls into tube dorsal to notochord - can develop into spinal cord.

http://www-biol.paisley.ac.uk/courses/tatner/biomedia/jpegs/hypchrdb.jpg

• Pharyngeal gill slits connect pharynx, just posterior to mouth, to outside of animal.

• Most chordates have muscular tail extending posterior to anus.

http://science.kennesaw.edu/biophys/biodiversity/animalia/cephal.gif

Tunicates

• Sessile marine animals that adhere to rocks, docks, and boats.

• Invertebrates - urochordates.• Chordate characteristics are

present as larva.• Suspension-feeders.

http://www.aboututila.com/Reviews/Charlie-Johnson/Photos/Bluebell-Tunicates.jpg

Lancets

• Cephalochordates - have chordate characteristics in adult.

• Suspension-feeders.

Lancet

Vertebrates

• Neural crest, pronounced cephalization, vertebral column, closed circulatory system - subphylum Vertebrata.

• Neural crests start of formation of cranium; cephalization - collection of nervous tissue that forms brain.

http://bio1151.nicerweb.com/doc/class/bio1151/Locked/media/ch34/34_07NeuralCrest_L.jpg

• Have appendicular skeleton, supporting 2 pairs of appendages (fins, legs, or arms).

• Can be made of either bone, cartilage, or both.

http://sciencecity.oupchina.com.hk/biology/student/glossary/img/appendicular_skeleton.jpg

Jawless vertebrate

• 2 classes of jawless vertebrates still living: Class Myxini (hagfish) and Class Cephalaspidomorphi (lampreys).

• Hagfish - skeletons made of cartilage making them flexible, but no backbone.

Hagfish

• Lampreys - parasites with cartilage skeletons.

• Lack backbone - have notochord.

Jawed fish

• Jawed fish broken into 2 classes (extant).

• Chondrichthyes (cartilaginous fishes: sharks, rays), Osteichthyes (bony fishes: ray-finned fishes, lobe-finned fishes, lungfishes).

http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Chondrichthyes/megalodon.jpg

• Chondrichthyes - skeleton made of cartilage.

• Cartilaginous skeleton usually replaced by bone; chondrichthyes - process prevented.

• Fertilize internally; some lay eggs (oviparous), few give birth to live young (viviparous)

• Osteichthyes - bony fish - endoskeleton made of bone.

• Bony fish have swim bladder not found in cartilaginous fish - helps control buoyancy of fish.

• Bony fish actually broken down into 3 groups: ray-finned fishes, lobe-finned fishes, lungfishes.

Ray-finned fishes

Lobe-finned fish

http://www.cartage.org.lb/en/themes/Sciences/Zoology/Biologicaldiverstity/AnimalsIII/coelacanth.jpg

Lungfish

Tetrapods

• Tetrapods -land animals - walk on all fours - transition from water animals to land animals - amphibians.

• Class Amphibia - amphibians - salamanders, frogs, caecilians (legless animals that burrow)

• Fertilization external - lay eggs.• Most amphibians rely heavily on

moist skin to carry out gas exchange with environment - still tied to water.

• Some adult frogs have lungs.

Caecilian

Amniotes

• Mammals, birds, reptiles, including turtles, lizards, snakes, crocodiles.

• Transition to land - adaptations were needed: amniotic egg, waterproof skin, increasing use of rib cage to ventilate lungs.

http://content.answers.com/main/content/wp/en-commons/thumb/f/fc/250px-Tortoise-Hatchling.jpg

• Amniotic eggs of most amniotes have shell that retains water - can be laid in dry place.

• Inside shell of amniotic egg - several extraembryonic membranes that function in gas exchange, waste storage, and transfer of stored nutrients to embryo.

Reptiles• Class Reptilia divided into 4

orders.• Reptiles - several adaptations for

terrestrial life not found in amphibians - leathery skin to prevent dehydration, lungs.

• Fertilization internal, eggs laid (amniotic eggs)

http://www.dnr.state.wi.us/org/caer/ce/eek/critter/reptile/images/turtleHatching.jpg

• Reptiles - ectotherms - cannot maintain own internal temperature (cold-blooded).

• Turtles return to water to lay eggs; have not evolved since 1st appearance.

• Lizards - most numerous reptiles.

• Snakes - limbless reptiles - still have pelvic bones - evidence that they evolved from reptiles with legs.

• Crocodiles and alligators - largest living reptiles.

• Breathe through their nostrils that are pointed upward out of water.

Birds• Birds - class Aves - broken down

into 28 orders (few flightless birds)

• Birds evolved to have hollow bones to allow for flight and feathers.

• Modern birds - toothless - grind food in muscular gizzard near stomach.

• Large brains of birds (proportionately larger than reptiles or amphibians) support very complex behavior.

• Birds - endotherms - metabolism allows them to regulate internal temperature.

Mammals• Mammals - class Mammalia -

identified by mammary glands.• Most mammals give birth to live

young after internal fertilization.• Nutrition done via placenta.• Most mammals capable of

learning due to larger brains.

• Monotremes - duck-billed platypus and echindas - lay eggs that have yolks to support embryo.

• Marsupials - born early in development crawl into pouch in mother to complete development.

• Eutherians - placental mammals.

http://cache.eb.com/eb/image?id=94548&rendTypeId=4

Echinda

http://marsupials.org/koalaalb.jpg

Opposum

http://www.ucmp.berkeley.edu/mammal/eutheria/rat.jpg

• Primates - most advanced of eutherians.

• Opposable thumb characteristic of most advanced primates.

• Divided into 2 groups: prosimians (lemurs), anthropoids (apes, humans).

http://www.dumondconservancy.org/dc2005/images/web/troy%20originals/lemur8.jpg

http://www.dkimages.com/discover/previews/920/55048736.JPG

• New World monkeys - arboreal (live in trees) - tails used for grasping.

• Hominoid - great apes and humans collectively.

• Hominid - group closely related to humans.

• Human evolution included many adaptations - larger brains, ability to stand upright.

http://www.nhc.ed.ac.uk/images/vertebrates/primates/HominoidSkulls.jpg