mammals and primate evo

Mammals and their immediate ancestors are synapsids First mammals appeared in the triassic, over 200 million years ago Modern mammals consist of three lineages; monotremes, marsupials, and placental mammals

1)Hair: Follicles in the dermis; shaft made of keratin For insulation, camouflage, defense, and sensory (whiskers) even whales have hair/hair follicles 2) mammary glands, females produce milk for offspring 3)Endothermy-body temp internally regulated (homeothermic with exceptions) Fat and fur provide insulation 4)Placenta(in most)-organ serves as provisional lungs, intestines, and kidneys of the fetus without mixing maternal and fetal blood (not present in monotremes or marsupials) placenta is a modification of a membrane of the amniotic egg 5) Specialized teeth; carnivore- canines herbivore-premolars and molars omnivores-molars, canines premolars and incisors 6)Hooves and horns, are all derived from keratine. Horns have a core bone surrounded by a sheath of certain, don’t shed. Antlers, made of bone and shed annually. Rhino horns are made from certain, are not attached to skull.

Amnion remains unchanged, yolk sac greatly reduced allantois contributes to the umbilical cord chorion forms the placenta

Canines in mammals are homologous, but the saber tooth configuration is a result of convergent evolution

convergent evolution

synapomorphy(evolved once)

-pouched mammals -brief gestation; no implantation of the embryo in the uterus -offspring live and feed in pouch ex)kangaroos, koalas, opossums

-Lay shelled eggs; young drink milk but do not suckle -Represented by echidnas and the platypus

1) Grasping fingers and toes; most with an opposable first digit; most with nails 2)binocular vision (eyes in front of the head) is good for depth perception

-long gestation period during which the embryo remains attached to the mother’s placenta to develop Young suckle following birth

1)Prosimians- Primarily nocturnal;color blind (lemus, tarsiets ect) 2)anthropoids: virtual, color vision, larger brain -monkeys-most have tails, -Apes, no tail, gibbons, humans, gorillas chimpanzees

primate group 1)Prosimians- Primarily nocturnal;color blind (lemus, tarsiets ect)

Primate group anthropoids: virtual, color vision, larger brain -monkeys-most have tails, -Apes, no tail, gibbons, humans, gorillas chimpanzees Chimp genome is 99% identical to humans

Species more closely related to humans than chimps Brain size: -Early hominins had chimp-sized brains, -Brain size increased considerably with the genus homo Bipedalism: -4mya, preceded larger brain size 2mya

Chimps: Skull attaches posteriorly(back of skull), spine slightly curved, arms longer than legs used for walking, long, narrow pelvis, femur angled out Hominin: skull attaches inferiorly(middle of skull), s s-shaped spine, arms shorter than legs, bowl-shaped pelvis, femur angled in