Chordates

What is a Chordate? Chordates are animals that are

characterized by a notochord, a dorsal hollow nerve chord, and pharyngeal slits at some stage of their development.

Characteristics

Notochord: Flexible rod of specialized cells along its dorsal

side Becomes the vertebral column (in vertebrates)

Dorsal Nerve Chord: Hollow tube just above the notochord Eventually becomes the brain and spinal cord

Pharyngeal Slits: Eventually becomes gills in aquatic organisms Becomes throat and ear structures in

terrestrial organisms

Contains 3 subphlya: Urochordates (inverts) Cephalochordates (inverts) Vertebrates (verts)

Invertebrate Chordates: Urochordates 2,000 species Have gill slits as larvae and adults Have notochord and dorsal nerve cord as larvae Metamorphosis results in loss of notochord and

tail, and the nerve chord shortens Examples: tunicates (sea squirts)

Invertebrate Chordates: Cephalochordates 28 species Small fishlike creatures Have notochord, dorsal nerve cord, and

gill slits as adults Lancelet is the closest living relative to

early animals

Vertebrate Chordates: Vertebrates 41,ooo species – 95% of chordates Bones or cartilage surround the dorsal nerve cord Contain skull and endoskeleton Have organs organized into systems

How Vertebrates Regulate Body Temperature Endothermic – warm-blooded

An animal that generates its own body heat Examples – birds and mammals

Ectothermic – cold-blooded Body temperature is determined by the environment Examples – reptiles, fish, and amphibians

Vertebrate Reproductive Development:

How long the eggs remain within the female

Oviparous – “egg birth” Lay eggs and eggs hatch outside mother’s body Examples – Most fish, most reptiles, all birds,

and 3 species of mammals Ovoviviparous – “egg-live birth”

Fertilized eggs remain inside of mother Nourished by egg yolk – not the mom May lay the eggs and then hatch shortly

thereafter OR eggs hatch inside of mother and young are born live

Examples – Some fish, some reptiles Viviparous – “live birth”

Young develop within the uterus Nourished by placenta Example – Placental mammals (humans)

Taxonomy of VertebratesClass Major Characteristics Examples

Agnatha Jawless fish Lamprey, hagfish

Chondrichthyes Cartilaginous fish Sharks, stingrays

Osteichthyes Bony fish Flounder, trout, etc.

Amphibians Part life in water, part life on land

Frogs, toads, salamanders

Reptiles Amniote egg and scales Turtles, alligators, snakes

Aves Feathers, hollow bones Birds

Mammals Warm blooded, hair, produce milk

Humans, primates, dogs, etc.

Agnatha – Jawless Fish AKA cyclostomes (round

mouth) Most primitive living

vertebrates Ostracoderms (extinct);

lamprey (extant) Lack paired appendages cartilaginous skeleton rasping mouth to suck

blood

Chondrichthyes – Cartilaginous Fish Sharks, skates, rays Well developed jaws and paired fins; continual

water flow over gills (gas exchange); lateral line system (detects water pressure changes)

Sexual reproduction with internal fertilization

Osteichthyes – Bony Fish Ossified (bony) endoskeleton; scales; operculum

(gill covering); swim bladder (buoyancy); 2 chambered heart with a single circulatory circuit through body

Most numerous vertebrate Sexual Reproduction, most with external

fertilization

Amphibians – “Double Life” 1st tetrapods on land Frogs, toads, salamanders 3 chambered heart with a

double circulatory circuit (travels twice through body for complete trip)

Double life & metamorphosis- aquatic (larva) & terrestrial (adult)

Must have moist skin for gas exchange

Must use WATER for reproduction

Reptiles Lizards, snakes, turtles, crocs and gators Amniote (shelled) egg with extraembryonic membranes

(gas exchange, waste storage, nutrient transfer) Waterproof scales of the protein keratin Well-developed lungs for gas exchange Most have 3 1/2 chambered heart; crocodilians have 4 No WATER needed for reproduction- first to truly adapt to

life on land

Aves – Birds (Flighted Reptiles) Flight adaptations: wings

(honeycombed bone) and feathers (keratin)

Toothless Airfoil wing Evolved from reptiles

(amniote egg and leg scales) 4-chambered heart – double

circuit Internal fertilization Archaeopteryx (evolutionary

link between reptiles & birds)

Mammals Mammary glands that

produce milk hair (keratin) 4-chambered heart large brain teeth differentiation Monotremes (egg-laying):

duck-billed platypus and echidnas (spiny anteater),

Marsupials (pouch): opossums, kangaroos, koalas

Eutherian (placenta):all other mammals

Vertebrate ChordatesEndo/Ecto-therm

Circulation (# of chambers)

Respiration Fertilization (where sperm unites w/egg)

Fish Ectotherms Single loop (2) Gills Internal or external

Amphibians Ectotherm Double loop (3) Larvae-gillsAdult- lungs & skin

External

Reptiles Ectotherm Double loop(most 3 1/2 Crocodilians-4)

Lungs Internal (some external)

Birds Endotherm Double loop (4) Lungs (more complex)

Internal

Mammals Endotherm Double loop (4) Lungs (most complex)

Internal