Vertebrates The Origin of Tetrapods The first vertebrates
Vertebrates
The Origin of Tetrapods The first vertebrates on land were amphibians in the Devonian (400 mya) u May have arose from the rhipidistian (features). u Arose in coastal or brackish marine environment u
Origin of Tetrapods
Origin of Tetrapods
Tetrapods Advantages of Terrestriality • An increase in metabolism and development due to higher body temperature. • Energy – An increase of 10 degrees Celsius (from 20 degrees (water temp) to 30 degrees (air temp) would allow for a doubling of their metabolic rates
Tetrapods Lungs – To breath air, it required an increased vascularization of the air -filled cavity (a pouch from the posterior pharynx similar to the swim bladder), with a rich capillary network to form a lung.
Tetrapods Double circulatory system • Fish have a single circuit system – low blood pressure • The double circulation system allows for higher pressure with one circuit going to the lungs and another going to the body.
Tetrapods Nasal Openings • • Bony fish have 4 external nares (2 on each side) which allows water to run across the olfactory tissue. Tetrapods have two external and two internal nares in the palate. This allows air to be drawn in through the nose.
Tetrapods – General Characteristics Body Density - Limbs Air is 1000 times less buoyant then water • counter the effects of gravity • homologous structures (bones – humerus, ulna and radius).
Tetrapods – General Characteristics Body Density - Girdles – • In fish, the pectoral girdle is attached to the skull. • Early tetrapods developed a stronger shoulder girdle, bulky limb bones and well developed muscles. • The pelvic girdle is fused to the backbone to increase the force that can be generated by the hind legs.
Tetrapods – General Characteristics Body Density Vertebrae and Ribs – • Vertebrae have developed zygapophyses. • The development of ribs can also protect the lungs.
Tetrapods – General Characteristics Body Density - Skull and Neck • • • The skull has been shortened and the snout elongated. The head becomes separated from the body by a neck (a cervical vertebrae) that allows the head to be lifted. A second vertebrae was then added to allow for a side to side movement.
Tetrapods – Evolutionary History 1. Fish
Tetrapods – Evolutionary History u u “Fishapod” – Tiktaalik (375 mya) A fish with tetrapod features, this animal probably could not walk on land but could lift itself out of the water. 1. 2. Fish Characteristics – Scales – Fins – Gills and lungs Tetrapod Characteristics – Neck – Ribs – Fin skeleton – Flat skull – Eyes on top of skull
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, moist (cutaneous respiration), and glandular (toxins) 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
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
Class: Squamata
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
Class: Squamata
Class: Squamata
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
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
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