BIOL 112 Unit 4

Phylum Chordata includes…

amphibians, reptiles (including birds), and mammals

Phylum Chordata characteristics…

1. Notochord —> develops into vertebrae

2. Dorsal hollow nerve cord —> develops into spinal chord

3. Pharyngeal slits —> gill or jaw support

4. Post-anal tail

Chordata Subphylems…

cephalochordata, urochordata, and vertebrate

Cephalochordata

• Lancelets

• key chordate features in adults

• burrows tail-in & filters feed

• gas exchange across skin

Urochordata

• Tunicates (“sea squirts”)

• key chordate features in larva

• suspension-feeds with pharyngeal slits

Vertebrate characteristics…

• cartilage &/or bone vertebrae

• 2+ sets of Hox genes

Vertabrate endoskeleton…

• Axial skeleton: skull, vertebrae, & ribs

• Appendicular skeleton: pectoral & pelvic area

Cyclostomes

• Jawless vertebrae

• reduced vertebrae

• eel like bodies

• No lateral fins

• slime glands

• keratin teeth

Hagfish

• Cyclostome Vertebrate

• marine scavenger

• cartilage skull & notochord

Lamprey

• Cyclostome Vertebrate

• jawless parasire in fish

• cartilage skeleton & notochord

Gnathostomes

vertebrates with hinged jaws & larger forebrain. 2 pairs lateral fins/limbs.

Chondichthyes

• Gnathostomes made of cartilage!

• sharks, rays, skates

• bone minterals lost to decrease density and increase buoyancy

• Bony teeth (tooth-like scales)

• Internal fertilization

Oviparous

eggs laid & hatched outside mother’s body; embryo filled with yolk

Vivparous

young develop in uterus, get nutrience from mother’s blood through yolk sac placenta, live birth

Ovoviviparous

egg hatches inside mother’s body, embryo fed by yolk, live birth

Osteichthyes

• Gnathostomes made of bone!

• ray-fin fish & lobe-finned fish

• oviparious w/ external fertilization

• skeleton mostly ossified (mineralized by hydroxyapatite)

• flat scales & slime

• operculim to cover gills

• lungs —> swim bladder for buoyancy

Types Osteichthyes

Actinopterygii, sarcoptherygii, actinistia, dipnio

Actinopterygii

• Osterichthyes: ray-finned fishes!

• thin fins supported by flexible rays

• most diverse group of all vertebrates

  • marine & freshwater

Sarcopyerygii

• Osterichthyes: lobe-finned fish!

• pelvic & pectoral fins supported by bones & muscles

Actinistia

• Osteichthyes: marine coelocanths

• ancient relic species thought to be extinct

• lobe-fins

• swim bladder full of lipids

Dipnoi

• Osteichthyes: freshwater lungfishes!

• gulps air into lungs in stagnent ponds

  • so no swim bladder!

• lobe fins

Tetrapods

• 4 limbs w/ wrist & digits

• neck

• pelvic girdle fused to backbone

• lung-breathing as adults

• ears

Tetrapods come from…

lobe-finned, lung-breathing fish

Amphibia

• type of tetrapod

• thin & moist skin; loses water easily

• gas exhange across moist skin & lungs

• gulps air like fish to fill lungs

• oviparious

• 3-chambered heart

Urodela

• Amphibia: salamanders!

• 4 legs & tail as adult

Anura

• Amphibia: frogs!

• 4 legs but no tail as adult

Apoda

• Amphibia: caecilians!

• snake like, no legs as adulr

Aminotes

• type of tetrapod

• aminotic egg: reproduction freed from water

• porous egg shell for O₂ / CO₂ exchange

• internal fertilization

Reptiles

• tetrapod: Aminotes

• scaley skin w/ protein keratin & waxy lipids

• breathe w/ lungs & negative pressure breathing

Turtles

upper & lower bony shells fused to ribs & vertebrae

Lepidosaurs: Tuataras

• ancient lizard-like reptile

• lizard clade but w/ unusual features

Lepidosaurs: Squamates

• lizards & snakes!

• snakes descended from lizards

Archosaurs: Crocodiliaus

• crocodiles & alligators

• gizzard

• 4 chambered heart

• oviparous

Archosaurs: Birds

• diverged from theropods (feathered dinosaurs)

• forelimbs —> wings w/ keratin contour feathers

• no teeth, keratin beak over bone

• no bladder/ urethra

• 1 ovary

• 4 chambered heart

  • airsacs

• muscular gizzard

Mammals

• type of tetrapod

• descended from synapsid amnitotes

• synapsid jaw-joint reduced to middle ear bones

• mammary glands secrete milk

• hair/fur

• varying teeth

• highly developed brain/behavior

• muscular daphram aids ribcage breathing; alveoli

• cecum has mutualistic microbes (ruminants)

Monotreme

• type of mammal: echidnas & platypus!

• egg laying mammal!

• young lap milk, no nipples

Marsupials

• type of mammals: kangaroos, koala, etc.!

• maternal pouch

• embryo starts in uterus w/ placenta —> crawls to pouch

• young latches to nipple to finish development in pouch

Eutherians

• type of mammals: “placenta mammals”

• better placenta for longer gestation

• young more developed at birth

Primates

• type of Eutherians

• hands & feet adapted for grasping

• flat nails

• large brains

• eyes forward

• flat face

Primate groups…

1. Lemurs & co: arboreal

2. Tarsiers: arboreal

3. Anthropoids: monkeys, apes, & humans

Constitutive skin color

genetic pigment

Facultative (inclucible) skin color

tanning

Eumelanin

black/brown pigment

Pheomelanin

red/yellow pigment

Folate B-vitamin

dark skin

Vitamin D

light skin