Vertebrates The Origin of Tetrapods The first vertebrates

Vertebrates

The Origin of Tetrapods The first vertebrates on land were amphibians in the Devonian u May have arose from the rhipidistian (features) or a lungfish (DNA) u

Origin of Tetrapods

Classification u Phylum: Chordata u Subphylum: Vertebrata u Superclass: Gnathostomata u Class: Amphibia – Order: Urodela (Salamanders) – Order: Anurans (Frogs and Toads) – Order: Apodans (Caecilians)

Class: Amphibia u Two lives – refers to metamorphosis of many frogs u u u Skin smooth and moist (cutaneous respiration) Three chambered heart with a double circulation system Mesolecithal eggs with jelly-like membrane

Order: Urodela 400 species u Salamanders u Retain their tail as adults u Limbs are at right angles to the body u Carnivorous u

Order: Anurans 3500 species u Frogs and Toads u Lose their tail as adults u Hind limbs are adapted for jumping u Tongue connected to front of mouth u Secrete mucus u

Order: Apodans 150 species u Caecilians u Legless and blind u

Evolution of the Amniotic Egg u Allows animals to complete their entire life cycle on land u Has shell that retains water (or is lost when kept inside mammals) u Specialized extraembryonic membranes (not part of the animal)

Evolution of the Amniotic Egg u Amnion - Protects from dehydration and mechanical shock u Yolk Sac - Nutrient storage u Albumin - Nutrient storage u Allantois - stores waste, gas exchange u Chorion - gas exchange

Amniotes

How Reptiles differ from Amphibians Tough, dry skin u Amniotic egg u Crushing or gripping jaws u Copulatory organs u More efficient circulatory system with a higher blood pressure u More developed lungs (thoracic breathing) u Better water conservation u Better body support and limbs u Better nervous system u

Classification u Phylum: Chordata u Subphylum: Vertebrata u Superclass: Gnathostomata u Class: Reptilia (not real) – Class: Testudines (Turtles and Tortoises) – Class: Spenodontia (Tuataras) – Class: Squamata (Lizards and Snakes) – Class: Crocodilia (Crocodiles and Alligators)

Reptile Radiation Synapsids (therapsids) - led to mammals u Sauropsids u – Anapsids (turtles) – Diapsids (all others)

Class: Testudines (Chelonia) Evolved on land returned to water (lay eggs on land) u Protective Shell u – Carapace – Plastron

Class: Sphenodontia u Tuataras – Two living species (New Zealand) – Not a True Lizard (no external ears) – Very Primitive (similar to mesozoic reptiles – Well developed eye below skin?

Class: Squamata u Lizards – geckos, iguanas, skinks, chameleons u u terrestrial, burrowing, aquatic, arboreal moveable eyelids Paired copulatory organs Lower jaw not attached to skull

Class: Squamata

Class: Squamata Snakes u Lack limbs u Lack moveable eyelids u Jacobson’s organ u Pit Vipers (heat) u Venom u – neurotoxins – hemolytic enzymes

Class: Squamata

Feeding Adaptations u Teeth curved and pointed inward u Hinged Quadrate bone u Bones of jaw are attached by muscles and ligaments u Moveable palate u Elastic skin u No sternum

Largest living reptiles u Most closely related to dinosaurs u Complete secondary palate u Four chambered heart u Nest temperature u Class: Crocodilia

Dinosaurs and Pterosaurs u Dinosaurs – Ornithischian – Saurischian (closely related to birds) u Pterosaurs – flying reptiles

Class: Aves

Class: Aves Feathers u Hollow Bones u Wings u Endotherm u Organs reduced u Beak without teeth u No bladder u

Class: Aves u Wishbone – Called a Furcula made up of the fused clavicles.

Class: Aves u Muscles – – Pectoralis muscle pulls wing down – Supracoideus raises wing

The Origin of Birds Feathers u Beak with teeth u Long Tail u Wing with claw u

The Origin of Birds Sinoauropteryx protofeathers? u Caudipteryx - true feathers u

Bird Classification u 8600 species of bird (28 orders) – 60% are passeriformes (perching birds) u Two major Types – Ratites u Ostriches, Emus – Carinates u Song birds

Class: Mammalia Hair u Endothermic u Mammary glands u Live birth (2 exceptions) u Teeth differentiation u Jaw modified to incorporate bones into inner ear u

The Evolution of the Mammal u u u Reptile’s lower jaw made up of several bones Reptile’s middle ear made up of one bone Mammal’s lower jaw made up of one bone Mammal’s jaw joint has shifted Mammal’s middle ear made up of three bones

Mammal Classification u Monotremes – lay eggs – no nipples

Monotreme

Mammal Classification u Marsupials – born early – develops in pouch

Marsupials

Mammal Classification u Placentals – Eutherian mammals – development in uterus joined by placenta

Proboscidea

Sirenia

Edentata

Rodentia

Lagomorpha

Carnivora

Artiodactyla

Cetacea

Perissodactyla

Chiroptera

Insectivora

Primate Evolution u Ancestral primate (arboreal) (65 mya) – binocular vision – opposable thumb u Prosimians – lemurs, tarsiers pottos

Primate Evolution u Ancestral primate (arboreal) (47 mya) – binocular vision – opposable thumb u “Ida” – Missing Link – – – No claws Lack a tooth comb Short limbs Short face Talus – corner of leg/foot

Primate Evolution u Anthropoids (50 mya) – Monkeys u Old World – External nares close together – Opposable thumbs – Calloused ischial tuberosities

Primate Evolution u Anthropoids (50 mya) – Monkeys u New World – Broad flat nasal septum – Nonopposable thumb – Prehensile tail

Primate Evolution u Hominoids (30 mya) – apes

Human Evolution Brain Size u Jaw Size u Bipedalism u Reduced Size difference in sexes u Family Structure u

Human Evolution Sahelanthropus u (6. 5 million years ago) u

Human Evolution Laetoli Footprints u (3. 5 million years ago) u

Human Evolution Australopithecus u (3. 24 million years ago) u

Primate Evolution u Homo genus (2. 4 -1. 6 mya) – Homo sapiens (200, 000 years ago)

Primate Evolution u Neanderthals (40, 000 years old)

Human Evolution Turkana Boy (Homo ergaster) u (1. 7 million years ago) u Between H. habilis and H. erectus u

Origin of Modern Humans u Out of Africa (monogeneus) – all races of humans evolved from an ancestor in Africa u Multiregional – Each race evolved from regional populations of Homo erectus