1.-Lecture-_1-_-Introduction-to-Comparative-Anatomy.pptx

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1. Introduction to Comparative Anatomy of Vertebrates Vertebrate Characteristics Vertebrate Classes

2. Anatomy – description and observation of structures Morphology – relating and interpreting structures Phylogeny – evolutionary history of a group or structure Embryology – study of development of structures in embryo

3. Homology and analogy Homology – shared common ancestry; related Analogy – shared common function Homoplasty – shared anatomy, but not homologous; for example, the wing of a bird and the wing of a grasshopper

4. Adaptation and preadaptation Adaptation – function first, then form; for example, there was food on land, so a fish with “funny fins” crawled to it Preadaptation – form first, then function; for example, fish with “funny fins” had fins first and came to land

5. Theory of natural selection Natural selection is often described as “survival of the fittest;” it maintains that the organisms best suited to survive in their environment are more likely to reproduce and pass their genetic material to the next generation, while those with less advantageous traits are less likely to survive long enough to reproduce

6. divergent, convergent, parallel and organic evolution Divergent – the evolutionary pattern in which two related species gradually become increasingly different; often occurs when closely related species diversify to new habitats Convergent – the pattern that takes place when species of different ancestry begin to share analogous traits because of a shared environment or other selection pressure; for example, whales and fish have some similar characteristics since both had to evolve methods of moving through the same medium, water Parallel – the pattern that occurs when two species evolve independently of each other, maintaining the same level of similarity; usually occurs between species that do not occupy the same or similar niches in a given habitat Organic – a concept that embodies the belief that existing animals and plants developed by a process of gradual, continuous change from previously existing forms

7. vestigial structure rudimentary structure Vestigial – structures better developed in ancestors Rudimentary – structures better developed in descendents

8. Ontogeny an individual’s life history from fertilization to death

9. Ontogeny an individual’s life history from fertilization to death

10. Heterochrony – changes in relative rates of development Paedogenesis – gonads develop fast Paedomorphosis – immature features of ancestor become characteristics of future species; for example, the gills of mudpuppies Neoteny – type of paedomorphosis in which larval features are retained in the individual

11. VERTEBRATE CHARACTERISTICS F our main chordate features. - Dorsal hollow nerve cord, notocord , pharyngeal gill slits/arches, postanal tail

12. Origin of vertebrates Through comparative embryology, scientists now believe that the chordates arose from a primitive sessile-benthic arm-feeding echinoderm. Tunicates are small marine invertebrate chordates quite common today; they may hold the key to vertebrate origins. Tunicates have a sessile adult stage in which they are filter-feeders with gill slits but no notochord or dorsal nerve tube. Tunicate larvae, though, are free-swimming filter-feeders; they are characterized by a notochord and dorsal nerve tube lost later when they metamorphose into sessile adults. It is possible that a tunicate-like organism evolved by way of neoteny into a free-swimming adult chordate. In this case, the juvenile features of tunicate-like organisms (notochord, dorsal nerve tube, and swimming ability) may have been evolutionarily retained in the succeeding chordates. The lancelet is a chordate with a free-swimming adult stage, and also a filter-feeding bottom-dweller. We may predict, then, that the first vertebrates were free-swimming, bottom-dwelling filter feeders, probably during the Ordovician Period, 500 million years ago.

13. Vertebrate characteristics Vertebral column – bone or cartilaginous vertebrae Bilateral symmetry – characteristic features on both sides Ventral chambered heart – “closed” heart Closed circulatory system – blood in heart or tubes; for example, veins and arteries Complete digestive tract – from mouth to anus Cephalization – sensory/nerve structures on “head” end

14. Vertebrate Classification Tetrapod – four-limbed animal Fish – any of numerous cold-blooded aquatic vertebrates, characteristically having fins, gills, and a streamlined body and including specifically any of the Osteichthyes , having a bony skeleton and any of the class Chondrichthyes , having a cartilaginous skeleton and including the sharks, rays, and skates; any of various primitive aquatic vertebrates of Cyclostomata , lacking jaws and including the lampreys and hagfishes. Agnathosotme – jawless vertebrates Gnathostome – jawed vertebrates

15. Endothermic – generate own heat Homeothermic – maintain steady temperature Example – mammals, birds Ectothermic – heat from environment Poikilothermic – temperature varies Example – snakes, fish

16. amniote and anamniote Amniote – an animal whose eggs contain an amnion, a membrane that surrounds the embryo and helps retain fluids and cushions embryo Anamniote – an animal whose eggs lacking embryonic membranes or amnion