Amniotes through Eutherians Chapter 34.6-34.8 By: Francisco Berrios and Siria Arzuaga

Amniotes A group of tetrapods that trace back to the same common ancestor. The only animals that have amniotic eggs. pods that retain water for vertebrates to complete their life cycles on land. Developed the ability to use the ribcage to ventilate lungs Early amniotes were herbivorous. Examples: Reptiles, birds, and mammals

Phylogeny of amniotes

The Amniotic Egg Exists inside mother’s belly or in a shell outside the mother. Extraembryonic membranes provide protection and nourishment 4 layers: Allantois, chorion, amnion, yolk sac Develop through tissue layers Has a shell

Amniotic Egg

Similarities and Differences Some Tetrapod's evolved and became 2 footed. Reptiles are ectotherms (cold blooded), while mammals and birds are endotherms (warm blooded) – Ectotherms have body temperatures determined by their environment. – Endotherms use metabolic heat to keep tissues warm.

Circulatory systems 4 chambered heart 3 chambered heart Provides high metabolism rate Mammals and birds 3 chambered heart Reptiles

Reptiles Traced back to the diapsids and anapsids. Parareptiles- dermal plates Proposed linkage with turtles All reptiles have: 3 chambered hearts ectothermic Covered with hard dry scales prevent dehydration amniotic eggs Rely on lungs for gas exchange

Reptile Anatomy

Diapsids Pair of holes behind eye socket Lepidosaurs Archosaurs Lizards, snakes, tuatara Marine reptiles (plesiosaurs) Archosaurs Crocodilians, dinosaurs Pterosaurs – first tetrapods to fly Presence of muscles, blood vessels, and nerves in the wing membranes

3 main groups of reptiles Turtles (Archosaurs) Over 200 species May live on sea or on land Huge shells to protect their bodies Crocodilians (Archosaurs) 23 species Semi-aquatic predators Huge teeth to attack big prey Lizards and Snakes (Lepidosaurs) Thousands of species Flexible skulls shed skin frequently Sea and land habitats

Last Living Dinosaurs There are 8,600 species of birds in the world. Similarities: Hollow bones Feathers V-shaped wishbone only 3 fingers Differences: Beak shape Feet/talons Feather structure

Why Can Birds Fly? Unique features Wings to produce flight Strong flight muscles to move the wings Active metabolism that provides energy to the muscles. Hollow bone structure to minimize weight. Lack a urinary bladder A wing is a remodeled version of the tetrapod forelimb.

Exceptions Ratites (non-flying) Flightless because… Ex: emu, ostrich, rhea, kiwi Flightless because… Sternal keel (bone) is absent, and the pectoral muscles (wing control) are not greatly enlarged.

Mammals (Synapsids) 3 types of mammals: Active, large-brained, endotherms with complex social, feeding, and reproductive behaviors. 5 characteristics: Hair to retain heat Mammary glands Milk production Middle ears Temporal fenestra Single jaw bone for faster and stronger chewing 3 types of mammals: Monotremes, Marsupials, Eutherians

Monotremes (egg-laying) Found in Australia and New Guinea Very unique: Offspring fully develop within egg. Lack nipples. After hatching, the baby sucks the milk from the mother’s fur. Echidna and platypus

Marsupials (pouch) Opossums, kangaroos, and koalas Young born very early in development Continue development in the pouch of the mother, called a marsupium. Produce milk and have nipples, higher metabolic rates Placenta nutrients diffuse into the embryo from the mothers blood when inside the mother

Eutherians (placental) Same characteristics of a marsupial but consists of a more complex placenta Longer pregnancy and stays inside the mother’s uterus. Primates are the most common. Include:lemurs, monkeys, apes (humans), and tarsiers.

Phylogeny of Ancestral Mammal

Primates Earliest primates lived in trees Had a thumb that was able to grasp Large brain, short jaw, flat face, forward looking eyes No claws but flat nails Omnivorous The 3 main groups of living primates lemurs, lorises, pottos; the tarsiers; and the anthropoids. Anthropoids include hominoids and monkeys opposable thumbs. more diversity

Cerebral Cortex Thought processes, consciousness perception, language, memory

Phylogeny of the Ancestral Primate

Apes Hominoids branch off of anthropoids. Include humans, gorillas, orangutans, and chimpanzees Have bigger brains compared to their size and their behavior is more flexible.

Sources: http://www.bio.sdsu.edu/faculty/archibald/Archibald05ELS.pdf http://www.ucmp.berkeley.edu/mammal/eutheria/placental.html http://www.ucmp.berkeley.edu/vertebrates/tetrapods/amniota.html http://wps.aw.com/bc_campbell_biology_7/26/6665/1706306.cw/index.html; http://wps.aw.com/wps/media/objects/1668/1708348/ebook/htm/campbell7e.htm?34.06