Directional Terms You Must Know

1. Directional Terms You Must Know • Caudal – towards the tail • Ventral – towards the belly • Dorsal – towards the back • Anterior – towards the head • Posterior – towards the rear • Lateral – to the sides • Medial – towards the middle

2. Distal – farther from the core of the body • Proximal – closer to the core of the body • Buccal – mouth region • Pharyngeal – muscular swallowing region of throat • Integumentary – the skin system • Respiratory – dealing with gas exchange • Cardiovascular – dealing with circulation of blood

3. Chordate Evolution

4. Four defining characteristics of the phylum Chordata • Notochord • Post-anal tail • Pharyngeal gill slits or pouches • Dorsal hollow nerve cord

5. Advantages of Chordate Characteristics • Notochord – provides stabilizing structure and muscle attachment = mobility in water • Gill slits/pouches – efficient oxygen delivery system in large bodied organisms • Post-anal tail – propulsion • DHNC – No clear hypothesis why dorsal would be any better than ventral

6. Subphyla of the Chordates • Urochordata – tunicates (sea squirts) • Cephalochordata – Lancelets (amphioxus) • Vertebrata – more accurately called “Craniata”, including anything with a cranium

7. Hypotheses on Vertebrate Evolution • Urochordate Ancestor: (1928) proposes larval tunicates are ancestor; larval forms retained form into adulthood and gained gonads to reproduce (“paedomorphosis”) • Cephalochordate Ancestor: (1991) proposes a lancelet ancestor due to many fossil forms that show notochord, myomeres, gill structure, and caudal projections.

8. Vertebrata Groups • Agnathans – lampreys and hagfish • Gnathostomes – “jaw opening” cartilaginous fish, bony fish, amphibians, reptiles, birds, & mammals

9. No jaws Cartilaginous skeleton No paired or dorsal fins No eyes Many mucus glands No jaws Cartilaginous skeleton No paired fins, but dorsal fin present Eyes well developed No mucus glands AGNATHA Hagfish vs Lampreys

10. Hagfish

11. Lampreys

12. Gnathostomes – Animals with Jaws • Hinged jaws were the most important evolutionary development • Jaw structure is thought to be derived from the first gill arch • Jaw was probably at first a hinged mechanism that prevented reflux of water during breathing • Jaws allowed new sources of food and new niches MORE FOOD = BETTER SURVIVAL = MORE BABIES = MORE REPRESENTATIVES WITH THOSE GENES FOR THE “GOOD” TRAIT

13. Jaw Development

14. Development of Paired Fins • Paired fins include the pectoral and pelvic fins. • Pectoral fins are used for balancing and turning • Pelvic fins are for stabilizing motion • Both kinds help control pitch, yaw, and roll

15. Pitch, Yaw, and Roll?!?

16. Origin of Paired Fins • Paired fins might have evolved from the most posterior gill arch, folds of the body wall, or from spiny appendages along the body. • The fossil record provides no clear answer to which hypothesis is accurate or if more than one may be accurate.

17. Acanthoidians (“spiny sharks”) that support the idea of fins from spines

18. Paired Fins – continued • Once paired fins arose, wide radiation of fish groups occurred. • Many fish groups are now extinct, but fish are still the most abundant and widespread vertebrate

19. Chondrichthyes Osteichthyes

20. Placoderms – Mean and Extinct

21. Class Chondrichthyes – cartilaginous fish Sharks Chimaeras (Ratfish) Rays Skates

22. Chondrichthyan characteristics • Cartilaginous skeleton • No bony structures except in the teeth and scales • Placoid scales (hooked from the side view) • Approximately 850 living species, mostly marine

23. Subclasses of the Chondrichthyes • Elasmobranchii – sharks, skates, rays • Holocephali – chimaeras (also called ratfish)

24. Skates vs Rays

25. Dorsoventrally flattened Hugely enlarged pectoral fins More muscular tail Usually 2 dorsal fins Lay eggs in cases Pelvic fin is one lobe Dorsoventrally flattened Hugely enlarged pectoral fins Whip-like tail Sometimes poisonous Dorsal fins usually absent Pelvic fin is 2 lobed Skates vs Rays

26. Chimaera Facts • Males have a single clasper on the head used for clenching the female during mating. • The gills are covered with a fleshy flap. • They have grinding plates rather than separate teeth. • Deep-sea dwellers

27. Shark Facts • Have 5 to 7 gill slits. • Range in size from 7 inches long (dwarf lanternshark) to 39 feet long (whale shark)

28. Birth Patterns • Oviparous – laying eggs outside of the body, most often with external fertilization (salmon, gray nurse shark) • Ovoviviparous – eggs are retained in the female body but are not connected to her during development, internal fertilization (dogfish, hammerheads, coelacanths) • Viviparous – egg is fertilized internally and retains a connection to the mother for nutrients until birth (bull sharks, surf perch, guppies, mollies)

29. Structures Unique to Fish that Chondrichthyes and Osteichthyes Share • Lateral line system to detect pressure waves. • Two chambered heart with single atrium and ventricle. • Have a range of birth patterns from oviparous, ovoviviparous, to viviparous birth.

30. Osteichthyes – The Bony Fish • “Bony Fish” have skeletons made of bone. • The two subclasses exist: the-ray finned fish (Actinopterygii) and the lobe-finned fish (Sarcopterygii) • The ray-finned fish comprise 97% of all living species of fish.

31. Sarcoptyergii • Lobe-finned fish have fleshy fins with internal bones. • Lungfish and coelacanths belong to this group.

33. Lungfish • “Lung” is a highly vascularized swim bladder. • They do also have gills. • Gulp air at surface when oxygen levels drop. • Can survive droughts by burying themselves into mucus-lined burrows.

34. The Ray-Finned Fish • “Ray finned” means the fins are webs of membrane supported by internal bony spines called fin rays. • Have a bony plate covering the gills, called the operculum. • Have a symmetrical homocercal tail. • Have a swim bladder used for buoyancy and gas exchange.