Vertebrate Movement to Land SZ2- Students will explain evolutionary history of animals over the history of life on earth. • Tetrapods- Animals with 4 limbs • Amphibians • Reptiles • Birds • Mammals • Evolved from fish
Why did vertebrates begin to move onto land 380 million years ago? • Competition for food and habitat in aquatic ecosystems • Escape predators • Availability of new food source and terrestrial niches
Tiktaalik http://www.youtube.com/watch?v=HyJAV-Jf9do http://tiktaalik.uchicago.edu/index.html
Transitional Tetrapods Skull, teeth, limbs similar to lobe-finned fish Acanthostega Ichthyostega
Struggles to Survive On Land • Water conservation • Gas exchange • Reproduction • Gravity • Separation of head, flexion of a neck to pick up food
Adaptations to live on land • Gills are usually lost • Lungs function • Breathe through skin • Secrete mucus • Prevent dehydration • Aids in respiration
More Adaptations to live on land • Skeleton • Fins evolve into limbs • Vertebral column supports body underneath it AIR IS NOT AS BOUYANT AS WATER.
Evolution of Circulation Fish Amphibian
Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Amphibia 1stland vertebrates Ex: frogs, toads, & salamanders
Class Amphibia– “Double Life”frogs, toads, salamanders, & newts Characteristics • “Double Life” -lives part of its life in water and part on land • Ectothermic- “outside heat”- body temp. regulated by environment • no scales or claws • Have thin, moist skin
AMPHIBIAN METAMORPHOSIS Egg- tadpole- adult • external fertilization with no parental care • lay eggs without shells in water • larvae are herbivores, adults carnivores • larva have tails to move in water
Amphibian Body Plan • Bilateral symmetry • 3 chambered heart • Larvae breathe through gills; adults breathe through lungs • Breathe through thin, moist skin (produces mucus) • Changes from larva to adult through the process of metamorphosis
Class AmphibiaOrder Anura • Anura- an=without, ura= tail • Tailless as adults • Specialized Hindlegs adapted for jumping and swimming- frogs running- toads • Tympanum (ear drum) and larynx well developed Ex. Frogs and toads frog dissection intro- http://www.kiz-oyunlari.com/files/file/kurbaga_ameliyat.swf
Class AmphibiaOrder Caudata • Caudata- “have a tail” • 2 pairs walking legs • Live in freshwater or leaf litter Ex. Salamanders and newts
Class Amphibia:Order Gymnophiona(Apoda) Gymnos- naked ophis- snake live in tropics in soil Elongated body Limbless Carnivores- eat invertebrates Ex. Caecilians – “blind”-small eyes
Kingdom Animalia Phylum Chordata Class Reptilia Ex: snake, turtle, lizards crocodile, dinosaurs
Reptilian Traits: 3 chambered heart (except for crocodilians- imperfect 4) Ectothermic Paired limbs with five toes and claws Tough, dry, scaly skin (horny epidermal scales) Jaws adapted for crushing and gripping Breathe with lungs metanephric kidney- produces uric acid to reduce water loss Large cerebrum as compared to rest of brain- behaviors- 1. instinct 2. learned
Reptile Legs • Short tetrapods for walking • Positioning of the legs more directly under the animal. This position provided more support than the splayed arrangement of the Amphibian legs.
Reproduction: Internal fertilization (to avoid desiccation of gametes), oviparous Lay amniotic eggs on land- no dependence on water Shells leathery, sometimes calcareous
Amniotic Egg Structures & Functions • Chorion provides a special hard covering that is permeable to respiratory gases (O2 and CO2) while being impermeable to water vapor. • Allantois is a storage reservoir for metabolic waste products such as nitrogenous compoundsand gas exchange. • Amnion is a fluid filled sac that acts as a cushion for the embryo and also prevents desiccation. • Yolk saccontains food for the embryo, thus eliminating the need for a larval stage.
Checkpoint List basic traits of reptiles. How do reptiles reproduce? Explain fertilization type, type of eggs, egg development. Which class of animals is better adapted for life on land, Amphibia or Reptilia? 4. Explain how your chosen class of vertebrates is better adapted for life in terrestrial ecosystems.
Phylum Chordata Subphylum Vertebrata Class Reptilia Order Testudine: • Body in a bony case • dorsal carapace(top of shell) • ventral plastron(bottom of shell) • Jaws with a horny beak, no teeth • Vertebrae and ribs fused • Ex. Turtles and tortoises
Phylum ChordataSubphylum VertebrataClass ReptiliaOrder Sphenodonta • Primitive reptile • closely related to dinosaur • Looks like lizard • Diapsid skull Ex. Tuatara- only living species
Phylum Chordata Subphylum Vertebrata Class Reptilia Order Squamata Diapsid skull with two temporal openings Skin is shed with horny epidermal scales Jacobson’s organ- sense of smell Movable skin, kinetic skull Poisonous- hemotoxins (blood) , neurotoxins(nervous system) EX. Snakes and lizards Lizards have movable eyelids Snakes- descended from tetrapod ancestor dichotomous key
Evidence suggests that Snakes descended from tetrapod ancestor • Pythons, and other species of snakes are sometimes born with vestigial hindlimbs • Snakes have DNA to code for a pelvis, and limbs, but genes are turned off early in development
Phylum ChordataSubphylum VertebrataClass ReptiliaOrder Crocodilia • Elongated massive skull • Imperfect 4 chambered heart • crocodiles, alligators, and caimans, gavials
Crocodilians Crocodiles, Alligators, Caimans, & Gavials
Gavial(gharial) Carnivores, “ghara”- pot- bulb on snout 12.25- 15.5 ft. long Rivers of India, Nepal, Pakistan, Bhutan, Bangladesh Critically Endangered