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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
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