Mr. Bastin - ZooBot Study Material on Chordates and Fishes

Chordates Taxonomy

Domain: Eukarya

Kingdom: Animalia

Phylum: Chordata

Chordates Basics (the four characteristics)

Four unifying characteristics:

1) hollow, dorsal nerve cord

-branching nerves at regular intervals

2) Notochord

-long supporting rod running through body just below nerve chord

3)Pharyngeal pouches

-paired structures in throat region

-may develop into gills

4) tail extends beyond anus

Chordate Groups

Subphylum Vertebrae, Subphylum Urochordata, Subphylum Cephalochordata

Subphylum Vertebrae

-have backbones

-99%of all chordates

>nerve cord = spinal cord

>notochord = backbone

>>composed of individual segments (vertebrae)

>>part of endoskeleton

>>>grows with organism unlike an exoskeleton

Nonvertebrate Chordates

-two subphyla: Subphylum Urochordata and Subphylum Cephalochordata

-no backbone

-all soft-bodied marine

Subphylum Urochordata

nonvertebrate

-tunicates (sea squirts)

-larvae have chordate characteristics

Subphylum Cephalochordata

nonvertebrate

-lancelets

>>no fins/legs

>>live on sandy ocean bottom

Fishes - Structure

-backbones

-organ systems

Fishes - Feeding

varies

-filter feeders with gill rakers

-herbivores

-carnivores

Fishes - Respiration

Gills:

-composed of filaments

>large surface area

-pump oxygen-rich water through mouth over filaments

-push oxygen poor water out openings on lateral sides

Fishes - Circulation

closed system

Osmoregulation

Saltwater fish lose water via osmosis

-Kidneys concentrate waste and return water to blood

Freshwater fish gain water via osmosis

-Kidneys pump out dilute urine

Some fishes move between salt/fresh water (adjust their kidney function)

Fishes - Response

Brain - well developed

Eyes - color vision equal/better than humans

Chemoreceptors - exceptional sense of smell and taste

Internal ears - limited ability to hear

Lateral line system - detects currents and vibrations in water (motion of other fish/prey)

Electroreception - some generate electric fields (detect disruptions by prey/inanimate objects)

Fishes - Movement

-Contract muscles along spine in "S" motion

>curve travels from head to tail and creates a backward force on water to propel fish forward

-Fins

> Propulsion and maneuverability

-Swim bladder

> Gas-filled organ to adjust buoyancy

Fishes - Reproduction

Fertilize externally or internally depending on species

Types:

-Oviparous

>eggs hatch outside body

>embryos obtain food from yolk within eggs

>ex. Salmon

-Ovoviviparous

>eggs stay within female after fertilization

>embryos obtain food from yolk

>live birth

>ex. guppies

-Viviparous

>embryos within female

> Obtain nutrition directly from female

>live birth

>ex. some sharks

Fishes - Three main groups

Jawless (subgroups: lampreys and hagfish), Cartilaginous (sharks, skates, rays), and Bony/Class Osteichthyes

Fishes - Group Jawless

no true teeth/jaws

-skeletons of cartilage and fiber

2 subgroups

-lampreys

>sucking disk saws hole into fish prey

-hagfish

>lack eyes

>feed upon dead fish

>secrete slime

>>clogs gills of predators

>>tie themselves into a knot and pass down body to remove their own slime

Fishes - Group Cartilaginous

-sharks, skates, rays

-skeletons of cartilage

-rough scales

-most harmless to humans

Fishes - Group Bony

Class Osteichthyes

-bony skeletons

-shape defines function

>streamlined, flat, narrow/disk, misc

Streamlined fish shape

fast swimmers

ex. tuna

-fins fit into grooves in body for speed

-powerful half-moon tail

-slightly warm blooded

Flat fish shape

-generally for camouflage on bottom

-mouths typically point down

> ex. halibut

Narrow/disk fish shape

maneuverable to escape predators

Misc. fish shape

-change shape

>ex. Puffer fish

-camouflage