chordates

Identifying structures

1. notochord

2. dorsal hollow nerve cord

3. pharyngeal slits

4. post anal tail

5. closed circulatory system

notochord

A rod of tough, flexible material that runs the length of a creature's body, providing the majority of its support

dorsal hollow nerve cord

nerve cord found in all chordates that forms the spinal cord and brain

chain of nervous tissue that runs down the back

pharyngeal slits

usually develop into gills

Post anal tail

a tail that extends beyond the anus

closed circulatory system

A circulatory system in which the oxygen-carrying blood cells never leave the blood vessels

neoteny

the retention of juvenile features in the adult animal

axial twist

torsion

head twists around 180 degrees

Lancelets

very simple

lacking a true heart, brain, skill

filter feeding

agnathans

hagfish, lampreys

have true, multichambered heart, skull and brain, more advanced sensory structures

no spine, jaws

Chondricthyes

sharks, skates, rays

first chordates with jaws

first vertebrates - encase dorsall hollow nerve chord with skeletal structure - vertebra (for increased complexity - anchoring point for more tissue)

gnathostomata

Osteichthyes

Bony fish

Mineralize skeletons using calcium

Ray finned fish (feathery bones)

Lobe finned fish

challenges of leaving water

not drying out

cant rely on buoyancy to support

tetrapods

vertebrate animals having four feet, legs or leglike appendages

lissamphibia

amphibians

skin only partially keratinized

3 chambered heart - gas exchange w/ air is less efficient than water, need more and faster moving blood - maximizes blood pressure through body

metamorphosis

need to return to water to breed - eggs are thin, dry out easily

frogs, salamanders, caecillians

amnion

Membrane that encloses the embryo in protective amniotic fluid

waterproof membrane

Amniotes

all animals with an amniotic egg

reptiles, mammals

4 chamber heart

chordata, tetrapods

4 chamber heart

advanced circulation to promote increased activity

heart now divided in 2

right half - deoxygenated blood to lungs

left half - oxygenated blood to body

no mixing

before birth, they resemble amphibian hearts, but the ventricle is split in two

- sometimes never develops wall

sauropsids

reptiles and birds

2 holes in skull behind eye hole (orbit)

lepidosaurs (lizards)

archosarus (crocodiles, dinosaurs, birds)

mammals

ancestral features

1. milk - to feed young, made by modified sweat glands

2. fur - temp control, waterproofing, display, camo, etc

Monotremes - platypus

- egg laying

marsupials

- first with placenta

- shell-less egg, yolk sac becomes vascular placenta - gas, nutrients exchange between fetus and mother

Placental mammals

- much more specialized placenta

- more blood supply, allows for placentals to grow much larger at birth