This document summarizes the phylum Chordata and types of fish. It describes the three subphyla of Chordata: Urochordata, Cephalochordata, and Vertebrata. Vertebrata contains seven classes of organisms including Agnatha (jawless fish), Chondrichthyes (cartilaginous fish), and Osteichthyes (bony fish). Key characteristics of fish are described such as their notochord, nerve cord, pharynx, gills, and circulatory, digestive, respiratory and nervous systems. Evolutionary adaptations that enabled fish to transition to land are also outlined.

1. Phylum Chordata & Types of FishKingdom Animalia Phylum Chordata Subphylum Urochordata Subphylum Cephalochordata Subphylum Vertebrata Class Agnatha Class Chondrichthyes Class Osteichthyes

2. Phylum Chordata“Chordates”Contains invertebrate and vertebrate speciesAll have bilateral symmetryAll at one point have a notochord, dorsal nerve cord, pharynx, and gill slits

3. NotochordA long rod of stiffened tissueNot bone or cartilage

4. Nerve CordTube found on the dorsal side that runs parallel to the notochord and gutAnterior end enlarges during development to form brain

5. PharynxA muscular tube that acts in feeding, respiration, or both

6. Gill SlitsA means of removing oxygen from a liquid environment for respiration

7. Subphylum UrochodataIncludes: Tunicates or Sea SquirtsSimilar niche to sponges but far more complex animalFilter feeder, diatoms and other bits of food caught in gill slitsLeathery “tunic” secreted and covers the body

8. Subphylum CephalochordataIncludes: Lancelets (called due to shape)Shows the four distinct characteristics of chordatesClosed circulatory systemRespiratory gases diffuse across the bodyFilter feeders

9. Subphylum Vertebrata7 Current Classes:Agnatha – jawless fishChondrichthyes – Cartilaginous fishOsteichthyes – Bony fishAmphibia – AmphibiansReptilia – ReptilesAves – BirdsMammalia - Mammals

10. Characteristics of Vertebrates:Many chordata characteristics seen in embryo stageNerve cord develops into a spinal cord and a brain

11. Two Large Advances:Spinal cord is protected by a bony vertebraeBrain is protected by a bony skull

12. Other Evolutionary AdvancementsExpansion of species began with the evolution of a jaw developed from the structure supporting the gill slitsThis lead to the ability to hunt other animals and thus led to advances in the nervous system and other body system processes

13. Other Evolutionary AdvancementsDevelopment of fleshy and skeleton fins that became the starting point for arms, legs, and wingsEvolution of gills allowed for better diffusion of oxygenGills developed into pouches then developed into lungs

14. IchthyologyThe study of fishes

15. Class Agnatha“Jawless Fishes”Most primitive fishLacks jaws and feed by suctionCylindrical and elongated bodyLack paired fins and scales

16. Hagfish & LampreysHagfish Feed mostly on dead or dying fishLampreysMostly freshwaterAttach to other fish and suck their blood

17. Class Chondrichthyes“Cartilaginous Fish”Skeleton made of cartilageMovable jaws with well-developed teethRough sand paper like scales made of the same composition of the teeth

18. Sharks & RatfishSharksAdapted for fast swimming and to be predatorsRatfish or ChimerasBottom dwellers Have long “rat-like” tails

19. Rays and SkatesRaysFlattened bodies with gills on the bottom of their bodiesWhip-like tail with stinging spines (venomous)SkatesVery similar to rays but with out the long tail or stinging spines

20. Class Osteichthyes“Bony Fish”Make of 98% of all fish and over half the vertebratesSkeleton at least made partially of boneThin, flexible, overlapping scalesMouth located at end of bodyPresence of gas-filled sac called a swim bladder

21. Body ShapeBody shape is varied and linked to its lifestyleFast swimmer need elongated bodies

22. Body ShapeShort, compressed bodies good for navigating tight places like reefs Bottom dwellers tend to have flattened shapes

23. Body ShapeElongated shapes are need for life in narrow spacesSome have less generalized shapes

24. Body ShapeSome shapes are conducive to camouflage with their environment

25. Exterior Layer

26. LocomotionFish swim with rhythmic side to side motion of the body or tailRhythmic contractions produced by bands of muscle called myomeres

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

29. Pectoral FinsOversized in sharks to provide lift due to no swim bladder, provide tight maneuverability in bony fish

30. Dorsal & Anal FinsEmployed as rudders used to steer and provide stability

31. Pelvic finHelp the fish turn, balance, and brake

32. Caudal (tail) finUsed in steering and force production

34. Lobe-Finned FishLink between water based fish and land dwelling amphibiansDeveloped bone/cartilage appendages that allowed them to move in mud and shallow watersDeveloped primitive lungs as well

35. DigestionFood passed through esophagus into the stomach for digestion and on into an intestine

36. DigestionPancreas, liver, and the pyloric caeca secrete digestive enzymes

38. Respiratory SystemFish get oxygen that is dissolved in the waterThey must get water to flow over gills to do this, called irrigation

40. Gill StructureThe gill is supported by cartilaginous or bony structure called gill archGill rakers are used as filters to stop food from entering gillsGill filaments contain the capillaries

41. Circulatory SystemClosed circulatory systemTwo chambered heartGas exchange happens in the gills

42. LungfishUses actual lungs to breathe and has reduced gills

43. Regulating Internal EnvironmentThe blood of marine fish is less salty than the water, therefore they lose water through osmosisTo replace it they must drink seawater

44. Nervous SystemCentral nervous system consisting of brain Highly developed sense of smell due to olfactory bulb/sacs which open to the nostrils

45. Nervous SystemSome bottom feeders like catfish have whisker like organs called barbels

46. Lateral LineUnique sense organ that enables them to detect vibrations in the waterCanals inside the body connected to surface by pores

47. Ampullae of LorenziniCan detect very weak electrical fieldsUsed to locate prey and navigate