BIOL 152 1st Edition Lecture 15 Outline of Last Lecture - Invertebrates Outline of Current Lecture - VertebratesCurrent Lecture- Vertebrates Shared Characteristics of Chordates1. Notochord2. Dorsal, hollow nerve cord3. Pharyngeal slits4. Muscular, post-anal tailUrochordates:- Marine suspension feedersCephalochordate: - Free swimming larva and adult - Retain chordate characters as adult - Segmented muscle - somitesChordate EvolutionGarstang’s hypothesis – paedomorphorosis, species born in aquatic environment and became sexually aquatic in water - FALSEChordate Evolution: - Appearance of the brain- Lancelets have an enlarged nerve cord tip- Similar gene expression of Hox genes in the lancelet nerve cord and the vertebrate brain These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Craniates: - Skull, brain, eyes, other sensory organs- No jaws, no vertebrae- Contain duplicated pairs of Hox genes- Neural crest cells- Pharyngeal cleft become gill slits- Higher metabolism and more extensive muscular tissue- Two-chambered heart and hemoglobinVertebrates: - More complex nervous system and skeleton- Another Hox gene duplication- Vertebrae- Appendages (fins in aquatic species)Basal vertebrates: - Lampreys- Suspension feeders as larvae and parasites as adults- Cartilaginous skeletonOrigins of bone and teeth- Unmineralized cartilage – lampreys and before- Transition to scavenging and predation (conodont ‘teeth’)- Mineralization began in mouth and then skullGnathostomes- Hinged jaws- Four clusters of Hox genes- Paired appendages- Enlarged forebrain- Lateral line system- Mineralized axial skeletonOrigin of jaws- Mutations and natural selection changed the size and orientation of gill archesSupporting evidence:1. Both consists of flattened bars of bony tissue that hinge and bend forward 2. Both derived from neural crests3. Muscels that move both are derived from same embryonic cellsChondrichthyes:- “Cartilage fish”- Carnivores with sharp vision, olfaction, and hearing- Can detect electric fields- Can adapt for buoyancyChondrichthyes conservation- Over 300,000 are severely threatened today from overfishing - Factor in coral reef decline – indirect effectInternal fertilization with secondary distinctions:- Oviparous: lay eggs that hatch outside mothers body- Viviparous: young develop within uterus- Ovoviviparous: fertilized eggs that remain within mothers body. Young born after
View Full Document
Unlocking...