Phylum Chordata & Types of FishKingdom Animalia

Phylum ChordataSubphylum UrochordataSubphylum CephalochordataSubphylum Vertebrata

Class AgnathaClass ChondrichthyesClass Osteichthyes

Phylum Chordata“Chordates”Contains

invertebrate and vertebrate species

All have bilateral symmetry

All at one point have a notochord, dorsal nerve cord, pharynx, and gill slits

NotochordA long rod of

stiffened tissueNot bone or

cartilage

Nerve CordTube found on

the dorsal side that runs parallel to the notochord and gut

Anterior end enlarges during development to form brain

PharynxA muscular tube

that acts in feeding, respiration, or both

Gill SlitsA means of

removing oxygen from a liquid environment for respiration

Subphylum UrochodataIncludes: Tunicates or

Sea SquirtsSimilar niche to

sponges but far more complex animal

Filter feeder, diatoms and other bits of food caught in gill slits

Leathery “tunic” secreted and covers the body

Subphylum CephalochordataIncludes: Lancelets (called

due to shape)Shows the four distinct

characteristics of chordatesClosed circulatory systemRespiratory gases diffuse

across the bodyFilter feeders

Subphylum Vertebrata7 Current Classes:

◦ Agnatha – jawless fish◦ Chondrichthyes – Cartilaginous fish◦ Osteichthyes – Bony fish◦ Amphibia – Amphibians◦ Reptilia – Reptiles◦ Aves – Birds◦ Mammalia - Mammals

Characteristics of Vertebrates:Many chordata characteristics seen in

embryo stageNerve cord develops into a spinal cord

and a brain

Two Large Advances:Spinal cord is protected by a bony

vertebraeBrain is protected by a bony skull

Other Evolutionary AdvancementsExpansion of species began with the

evolution of a jaw developed from the structure supporting the gill slits

This lead to the ability to hunt other animals and thus led to advances in the nervous system and other body system processes

Other Evolutionary AdvancementsDevelopment of

fleshy and skeleton fins that became the starting point for arms, legs, and wings

Evolution of gills allowed for better diffusion of oxygen

Gills developed into pouches then developed into lungs

Ichthyology

The study of fishes

Class Agnatha

“Jawless Fishes”

Most primitive fish

Lacks jaws and feed by suction

Cylindrical and elongated body

Lack paired fins and scales

Hagfish & Lampreys

Hagfish ◦ Feed mostly on

dead or dying fish

Lampreys◦ Mostly freshwater◦ Attach to other

fish and suck their blood

Class Chondrichthyes“Cartilaginous

Fish”Skeleton made of

cartilageMovable jaws

with well-developed teeth

Rough sand paper like scales made of the same composition of the teeth

Sharks & Ratfish

Sharks◦ Adapted for fast

swimming and to be predators

Ratfish or Chimeras◦ Bottom dwellers ◦ Have long “rat-like”

tails

Rays and Skates

Rays◦ Flattened bodies

with gills on the bottom of their bodies

◦ Whip-like tail with stinging spines (venomous)

Skates◦ Very similar to

rays but with out the long tail or stinging spines

Class Osteichthyes“Bony Fish”Make of 98% of all

fish and over half the vertebrates

Skeleton at least made partially of bone

Thin, flexible, overlapping scales

Mouth located at end of body

Presence of gas-filled sac called a swim bladder

Body Shape

Body shape is varied and linked to its lifestyle

Fast swimmer need elongated bodies

Body Shape

Short, compressed bodies good for navigating tight places like reefs

Bottom dwellers tend to have flattened shapes

Body Shape

Elongated shapes are need for life in narrow spaces

Some have less generalized shapes

Body Shape

Some shapes are conducive to camouflage with their environment

Exterior Layer

Locomotion

Fish swim with rhythmic side to side motion of the body or tail

Rhythmic contractions produced by bands of muscle called myomeres

Locomotion

Swim bladder – specialized organ filled with gas that assists in floating due to a heavier bone structure (found in bony fish)

Pectoral Fins

Oversized in sharks to provide lift due to no swim bladder, provide tight maneuverability in bony fish

Dorsal & Anal Fins

Employed as rudders used to steer and provide stability

Pelvic fin

Help the fish turn, balance, and brake

Caudal (tail) fin

Used in steering and force production

Lobe-Finned FishLink between water

based fish and land dwelling amphibians

Developed bone/cartilage appendages that allowed them to move in mud and shallow waters

Developed primitive lungs as well

Digestion

Food passed through esophagus into the stomach for digestion and on into an intestine

Digestion

Pancreas, liver, and the pyloric caeca secrete digestive enzymes

Respiratory System

Fish get oxygen that is dissolved in the water

They must get water to flow over gills to do this, called irrigation

Gill StructureThe gill is

supported by cartilaginous or bony structure called gill arch

Gill rakers are used as filters to stop food from entering gills

Gill filaments contain the capillaries

Circulatory System

Closed circulatory system

Two chambered heart

Gas exchange happens in the gills

Lungfish

Uses actual lungs to breathe and has reduced gills

Regulating Internal EnvironmentThe blood of marine fish is less

salty than the water, therefore they lose water through osmosis

To replace it they must drink seawater

Nervous System

Central nervous system consisting of brain

Highly developed sense of smell due to olfactory bulb/sacs which open to the nostrils

Nervous System

Some bottom feeders like catfish have whisker like organs called barbels

Lateral Line

Unique sense organ that enables them to detect vibrations in the water

Canals inside the body connected to surface by pores

Ampullae of Lorenzini

Can detect very weak electrical fields

Used to locate prey and navigate