!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Lecture!15!!Outline(of(Last(Lecture((I. Transitional!Forms!a. Organism!that!represent!intermediates!between!groups!b. Fishes!!7!tetrapods!c. Vertebrate!life:!water!to!land!Outline(of(Current(Lecture((II. Transitional!forms,!continues!Current(Lecture!I. Fish(vs.(Tetrapods(a. Ray7finned!fish!vs.!Modern!reptile(i. Pectoral!muscles!vs.!pectoral!fins,!shoulder!girdle,!etc.(b. Ray!fin!vs.!Lobe!fin(i. Lobe!fins!were!an!extremely!common!form!of!fishes.!(ii. Ceolacanth:!a!“living!fossil”!(1. Lobe!fin s!are!fleshy,!with!bo ne!arrangement!similar!to!th at!of!bone!sin!limbs!of!tetrapods(2. Lobe!fin s!are!not!al l!th at!di fferent!structurally/anatomi cally!than!tetrapods(iii. Living!lungfish:!Neoceradotus(1. Primitive!lungs!!(II. Devonian:!time!of!experimentation!in!fish7tetrapod!transition.!(a. None!were!fully!marine(b. “Fishapod”(c. Fish!characters:!fish7like!skull,!tail!fin(d. What!was!present!in!the!Devonian?(i. Ray!fins!–!but!not!very!common(ii. Lung!fishes(e. Change!in!shape!of!skull(III. Origin!of!tetrapods(a. Intermediates!“fishapods”!were!amphibious:!lived!in!rivers!and!swamps(i. primarily!aquatic(ii. Swimming!tail(iii. Internal!gills(b. Did!they!spend!much!time!on!land?(i. Probably!not.!They!were!ill7equipped!for!carrying!rather!large!bodies!on!land.!(!!(((((((((Earth(125(((1st(Edition(! !1. But,!probably!l ived!in !swamps!an d!marshes(2. Lots!of!b io logi cal!prod ucti vity!there(3. Yet!water!(in!these!environments)!gets!depleted!of!o xygen(a. Hence!the!lungs!and.gills(c. Carboniferous.Period:.Land!plants:!extensive!forests.!Land!animals:!giant!insects,!indisputable,!fully!terrestrial,!tetrapods!i. Devonian.Period:.360.my.1. Land!p lants :!first!radiati on! of!l and! plan ts,!free7sporing!vascular!plants,!several!groups!of!plants!evolve!leaves!and!true!roots,!first!seed7bearing!plants!appear!2. Land!an imals:!arthropo ds,!terrestrial.tetrapods:.few.or.none!d. Why!move!onto!land?!!i. Hypothesis:!Resources!–!availability!of!new,!easily!accessible!resources!ii. Hypothesis:!Escape!from!aquatic!predators,!move!across!land!to!lay!eggs!so!other!fish!don’t!consume!them!iii. Hypothesis:!environmental!stress!–!life!in!shallow!pools!which!could!occasionally!dry!up;!those!“fish”!able!to!handle!drought!survive!iv. Strategies!to!succeed!reproductively!e. Metamorphosis!is!very!common!among!amphibians!f. Reproduction!in!advanced!tetrapods!–!amniotic!egg!i. early!amniotes!still!retain!some!important!characteristics!of!water7dwelling!ancestors!(locomotion)!ii. Sprawling!gait!–!side7to7side!twisting!in!locomotion!1. amphibi an!( salamand er)!and!p rimitive!reptiles!(l izard)!iii. Carrier’s!constraint:!stamina!1. Sprawlin g!postu re!and!respiration !a. Primitive!reptiles!(lizards)!both!lungs!used!simultaneously!undulation!of!trunk!–!twisting!of!thorax!2. Locomotio n!i n!more!advanced!tetrapods! (horses)!–!u
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