chordates

Phylum: Chordata

Key features

1.) notochord

2.) dorsal hollow, nerve cord

3.) Pharyngeal swift

4.) postanal tail

notochord

flexible rod, extends along chordates back

most vertebrates notochord does not persist in adulthood usually replaced by backbone that surrounds the spinal cord

dorsal, hollow nerve cord

a cord that runs parallel to notochord (on dorsal/ back side)

in many nerve cord develops into spinal cord

enlarges at head end forming a brain

pharyngeal slits

in embryos slits or pouches form in pharynx

can develop to have multiple functions

invertebrates use for feeding (straining food particles out of water)

vertebrates pouches can develop into gill, middle ear cavity or other structures

postanal tail

muscular tail extends post anus in all chordate embryos

most chordates retain tails as adults (fishes, salamanders, lizards, felines, and many others)

all great apes (humans, monkeys) absorb most of tail before birth

tail bone (coccyx bone) remains as a vestige

phylum: chordata

>65k species

common ancestor was most likely aquatic invertebrate

vertebrates are a group of animals found only in the phylum chordata

all vertebrates are chordates but not all chordates are vertebrates (there are invertebrate chordates)

cranium

most chordates have a cranium

bony or cartilage rich case that surrounds and protects the brain

hagfishes and vertebrates form 2 classes of craniates (animals that have a cranium)

vertebral column

a protective flexible segmented backbone

made up of a series of small bones (vertebrae) or cartilage structures

protects spinal cord

also provide attachment points for muscles

gives animal greater range of movement

jaws

pair of bones that frame the entrance of mouth

usually include teeth or a beak and used for biting grasping food and chewing

development of hinged jaws evolved from modified gill support bones

enhance ability to grasp prey or gather food items expended ways vertebrates could feed

lungs

fishes have gills that absorb O2 from water and release CO2

air breathing vertebrates have internal saclike lungs for respiration

lungs homologous to swim bladders of bony fishes

swim bladders help control buoyancy in fishes but some fishes gulped air in shallow waters

developed into air breathing lungs in ancestors or terrestrial vertebrates

limbs

tetrapods “4 legs”

vertebrates with 2 pairs of limbs (legs, arms, wings’

sturdy limbs enabled animals to walk on land

includes birds, mammals, reptiles, amphibians

some have less than 4

snakes and caecilians have no limbs

limbs of whales, dolphins and sea lions are modified into flippers or too small to project from body

amniotic egg

shelled egg with serval membranes

amnion: fluid filled sac that cushions embryo from shock

chorion: helps with gas exchange between embryo and air outside the egg

allantois: collect and store metabolic wastes for embryo

yolk: contain nutrients for embryo

shelled eggs: leathery or hard outer layer that allowed animals to reproduce entirely on land (embryo does not dry out)

amniotes include: birds, reptiles, mammals

internal membranes of amniotic egg homologous to protective structures that surround fetus in uterus of mammals

thermoregulation

ectotherms and endotherms

ectotherms

body temperature fluctuate with environment

lack internal mechanisms to keep their body temperature within narrow range

employ many behaviors (such as basking in sun or burrowing into ground) to help adjust temperature

ex: invertebrates, fishes, most amphibians, most reptiles

endotherms

maintain a constant body temperature using heat generated from own metabolism

requires enormous amount of energy to maintain

explains why birds and mammals must eat so much more food than ectotherms of same size

ex: birds and mammals are endotherms

heart chambers

fishes: 2 chambers (1 atrium, 1 ventricle)

amphibians, most reptiles: 3 chambers ( 2 atrium, 1 ventricle

crocodilians, birds, mammals: 4 chambers (2 atrium, 2 ventricles) because they need better respiration and more oxygen (more oxygen = more energy)

more heart chambers means better separation of O2 rich blood from O2 poor blood

greater efficiency for blood delivery O2 to tissues

prochordates invertebrate chordates

notochord persists throughout life (not replaced by a vertebral column)

sea squirts/ tunicates (subphylum urochordata)

lancelets (subphylum cephalochordata)

tunicates

3k species most live in shallow ocean waters

“sea squirts”

marine invertebrate

sessile filter feeders

name from tunic (protective flexible body covering)

free swimming larva resembles tadpole

adults retain only pharyngeal slits

lancelets

small eyeless translucent

live in shallow seas

tail buried in sediment mouth extend into water

gas exchange occurs directly across the skin

clearly display all 4 major chordates characteristics as well as inklings of organs systems that appear in vertebrates

agnathans (hagfishes and lampreys)

have cranium

lack jaws (jawless fishes)

long slender bodies with gills

specialized sense organs clustered near head end

~ 70 species of hagfishes

~ 38 species of lampreys

not true fishes

hagfishes (slime hags)

cartilage makes up cranium

invertebrate! vertebrae do not surround nerve cord

live in cold ocean waters

eat marine invertebrates (shrimps worms or use raspy tongues to scavenge soft tissues of dead animals)

eyes poorly developed

touch and chemical sensitive tentacles near mouth to locate food

have some unusual abilities

can slide flexible bodies in and out of knots to pull food escape predation or clean themselves

lampreys

simplest vertebrates

live in salty or fresh water

spend most of life as larvae

adults eat small invertebrates

some species use suckers to consume blood of fish (parasitic)

in last century, lampreys ventured beyond natural lake Ontario range into other great lakes

responsible for population decline of lake trout and whitefish

vertebrates characteristics

vertebrate (replaced notochord)

spinal cord (replaced dorsal hollow nerve cord)

pharyngeal gill slits

postanal tail

fishes

aquatic vertebrates with jaws, gills, fins

most diverse and abundant vertebrates

>30k species

lateral line (on side of fishes): sense organs clustered near detects vibration nearby and helps animals find prey escape predation

2 main clades:

1. cartilaginous fishes

2. bony fishes

   1. ray finned fishes

   2. lobe finned fishes

play important roles in aquatic habitat

graze on algae scavenge dead organic matter prey on other animals

eat everything from mosquito larvae other small invertebrates to one another

catfish, cod, salmon, trout, mackerel, halibut, snapper, drum, and other fish species are important sources of dietary protein for people

many species are popular for sport fishing (tuna, bass, pike, grouper, etc)

cartilaginous fishes (chondrichthyes)

skeleton made of cartilage

800 species

most ancient claude of fishes

lack gill cover of bony fish (5-7 gill slits)

no swim bladder

skin covered by placoid scales

includes sharks, skates, rays

skates and rays

marine predators

dorsoventrally flattened

swim by undulating enlarged pectoral fins

most are bottom dwellers

often lie partially buried in sand

deed on hard shelled invertebrates, crush with massive flattened teeth

some have electric organs to stun prey (up to 200 volts)

largest species: manta ray (6m) feed on plankton

sharks

among ocean’s most dominant predators

flexible fins lightweight skeletons streamlined bodies absence of armored body

allow sharks to pursue prey rapidly

great white shark (carcharodon carcharias) largest predatory species

whale shark (rhincodon typus) largest fish known (18m) feeds on plankton