adaptive radiations in reptiles........pptx

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Adaptive radiations in reptiles

Adaptive radiations in reptilesWhat is adaptive radiation?It is the phenomenon in which the same genera or different but closely related genera become adapted to different kinds of environment or habitat.It is the formation of different species from a common ancestor getting adapted to different kinds of environment i.e. habitats by adopting various modifications.

Flourishing reptilesEnd of devonian produces organisms amniotaMesozoic era = age of reptilesfirst reptile (ancestor of reptilia)-cotylosauria(stem reptiles)Durind late Triassic period arose Dinosaur and Pterosaur belonging to archosauriaDuring late cretaceous period all of these giant reptiles disappeared

Reptilian ancestor-CotylosaurLizard like creature about 2 feet long It used to live on other larger animalsIntermediate characteristics

Early adaptive radiations during Permian periodSynapsids and Thecodonts evolved

synapsid thecodont

Synapsids Therapsids Mammals Thecodonts

Dinosaurs Crocodiles

Some stem reptiles returned to water

Ichthyosaurs Plesiosaurs

Second major adaptive radiations during Triassic periodDinosaurs and Pterosaurs evolved from Thecodonts DINOSAURSLargest animals everCarnivorous and HerbivorousThey can be divided into Reptile-like(Saurischians eg:-Tyrannosaurus Rex) and Bird-like(Ornithischians eg:-Camptosaurs) PTEROSAURSSmall sized flying reptilesPowerful forelimbs supporting wingsEg:- Pteranodons

Third major adaptive radiations during Cretaceous periodPeriod of mass extinctionNearly all dinosaurs and many invertebrates disappearedFew reptilian groups survived SquamataCheloniaCrocodiliaRhynchocephalia

Classification of reptiliaSubclass: anapsidaOrder-cotylosauriaOrder-cheloniasubclass: synaptosauriaOrder-sauropterygiaSubclass: ichthyopterygiaOrder-ichthyosauriaSublass: lepidosauriaOrder-rhynchocephaliaOrder-squamataSubclass: archosauriaOrder-crocodiliaOrder-pterosauriaOrder-saurischiaOrder-ornithoschiaSubclass:synapsidaOrder-pelycosauriaOrder-therapsida

Adaptive radiations in order-squamata(lizards and snakes)LizardsVarious habitats such as forests, grasslands, deserts and even below soilLizards have adapted to various habitats such asAdaptations to aboreal habitatAdaptations for flyingAdaptations for runningAdaptations for fossorial habitatAdaptations for desert habitat

Adaptations to aboreal habitat(living on trees)

Short limbsPrehensile tail eg:- chameleonDigits with adhesive discs & pads/claws eg:-geckoAdaptations for flying(gliding)Development of petagia supported by ribs(5-6)Slender and tapering tail eg:-draco

Adaptations for running

Narrow body for least resistanceWell developed hind limbs for upright postureReduced number of digitsEg:- calotesAdaptations for fossorial habitatNarrow cylindrical body Limbs absentEyes are degenerated (eg:-anguis)

Adaptations for desert habitat

Body covered by numerous spinesUreotelicSkin-hygroscopicEg:uromastyx and phrynosoma

SnakesBurrow and also live on landVestigial organsAdapted to various habitats such as trapical and temperate forests, grasslands, in desserts, in alpine medows and also living undergroundSmallest species (brahming blind) and largest species(reticulated python)Carnivorous snakes show following adaptations:-Loosely articulated jawsPresence of Venom apparatusPython & boas squeeze their preyPresence of prey is easily detected by vibrations of air and waterPresence of forked tongueAboreal snakes show following adaptations:-Laterally compressed bodyPrehensile tailExhibit protective colourationFlying snake can glide from tree to tree

Aquatic snakes show following adaptations:-Flat tailNostrils on the top of snoutHighly venomousFeed on fish particularly eelProtective colouration such as yellow bellied sea snake and black banded kraitFresh water snakes are semi-aquaticThey overhang on tree branches on a stream to catch their preythey also hunt in water

Adaptive radiations in order- chelonia(turtles and tortoises)Oldest living reptiles on the earth evolved from stem-reptilesTortoise = landforms (short limbs with 5 digits each)Turtles = aquatic forms (limbs modified to form flippers)Outer shell(plastron) fused with ribs called plastronSlow metabolic rateCan remain for long time under water Reproductive behaviour

Adaptive radiations in order-crocodilia(crocodiles, alligators and gavialis)Evolved from thecodontsKins of dinosaursOnly archosaurs survivingSemi-aquaticHabitats- rivers, lakes, ponds, swamps, estuaries, seas etcLocomotion- long and powerful tailBreathing:- development of false palateNostrils present in the front of the mouth in the primitive land dewelling animalsAquatic forms- nostrils towards the back of their headIn crocodilians nostrils are on the tip of snout but underneath lies a partion running along the entire length of the mouthNasal opening are opened by constrictor muscles and closed by dialator muscles

Food habits:-Feed on insects, crustaceans, fishes, small frogs, birds, other reptiles and mammals.Also developed a method of crushing and grinding their prey.Reproduction:-Oviparous

Adaptive radiations in order-rhynchocephalia (tuatara)Rhynchocephalians evolved during permian period of paleozoic era and survived upto jurassic periodSphenodon (Tuatara) living fossilTuatara means lightening back in native Maori languageSurvival instincts:-Crest of large erect spines on their backThick tail with spinesHead relatively larger than body proportionJaws are chisel-likeThird eye on the top of head. This eye has lens, retina, and also nerve connection to brain.Habitat- burrowsPenis is absent in males.Female lays eggs only once in 4 years.

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