Biology 111- Mammals
Eutharians
-94% of mammals -viviparous (birth live young) -no shell or eggs -amniotic egg retained in female reproductive tract -embryo nourished by mother via placenta -often referred to as placental mammals but some marsupials have placentas. -Most species can be found in the rodent category
Features of mammals that are not unique
-endothermic -advanced nervous system -internal fertilization -heterodonty, different teeth for different tasks (unlike reptiles and fish) -specialized teeth reflect varied diet -4-chambered heart -mammals tend to have larger brains. Humans, dolphins and chimps have the largest brain relative to size and sperm whales have the largest brain.
Echidna
-short and long nose spiny anteaters -insectivores -long, sticky tongue -temp pouch for eggs -eggs hatch in 8 days -spines form in pouch at about 3 weeks -Independant origin of hair being used as spines -live 50 years
peripheral nervous system
-system of lateral nerves -cranial nerve from brain -spinal nerves from spinal cord Parasympathetic nerves "rest and digest" Sympathetic nerves "fight or flight"
What makes mammals unique?
-hair (insulation, camouflage, sensory and defence) -milk produced in mammary glands -placenta (although some other animals still have a placenta) -sweat glands -5000 species -Diverged from reptiles around 350 mya (carboniferous time period)
Tasmanian devil
-largest marsupial carnivore (size of a small dog) -scavenger -When extinct on mainland Australia due to hunting and the dingo and is now only found on Tasmania. Convergent evolution to look like dogs due to fact that they are carnivores (not related)
New world vs Old world Monkeys
New world are found in South America and Old world are found in Africa and Asia. -Split happened a long time ago New world monkeys have a prehensile tail unlike old world that can be used to grasp and hold objects. New world monkeys also have a flat nose and tend to be arboreal.
Frontal lobe
Phones Gage was shot through frontal lobe with a rod. He lived but his personality was vastly different. Went from very nice to very rude. This proves that frontal lobe controls personality.
Homo Floresiensis
Recently found on the island of Flored, Indonesia. review until 17000 years ago. Very small humans, much smaller height and brain size. Volcanic eruption likely caused extinction. Nicknamed hobbit.
Molecular movement across placenta
Small molecules move via diffusion ex. oxygen and carbon dioxide -fetal hemoglobin has a higher oxygen affinity then adult hemoglobin and there for moves to the fetus. -Also transmits urea, nutrients (sugar, vitamins and minerals), hormones an alcohol and drugs.
Homosapians
Theory that there has been an increased juvenilezation of apes as humans resemble juvenile apes and gorillas. -Arose in Africa 0.2 mya and spread out of Africa across Eurasia and over the rest of the world. -larger brain than earlier homo species -favouring increasingly complex social lives
Limbic System
amygdala, hippocampus and nucleus accumbent Pleasure and pain centre. Basic Physiological drives like hunger, thirst, emotions and long term memory. Amygdala controls if we find sounds annoying or pleasurable. hippocampus controls spacial memory.
Ambulocetus
ancestor of whales that lived 50 mya. 3 meters long and had ears similar to whales and could hear well underwater. Also had similar teeth to whales.
Cerebrum
conscious though, memories, most enlarged in humans compared to other mammals. Intellect, learning and language. Top layer is the cerebral cortex rich in cell bodies, grooves and ridges. Increased surface area is essential to humans intellect. Different parts of the cortex correspond to different actions and body parts. Motor cortex- large part of the brain associated with hands and tongue(speaking and face movement) SomatoSensory cortex- how we sense outside environment. Large part associated with hands and face again
prosimians
ex. bush babies, lemurs and loris -mostly arboreal and nocturnal -once found on all continents, but now only Madagascar and south east Africa (bush babies and loris) -Madagascar lemurs of evolved and radiated, not all live in trees and some live during the day. -many species are threatened or endangered.
Tasmanian tiger (Thylacine)
extinct now, last living one in 1933. Hunted to extinction
Megatherium
giant ground sloth herbivore 2 million years ago to 8000 years elephant sized
Evolution of mammals
mammals originally coexisted with dinosaurs but became dominant after they became sexting 65 mya. Mammals diversified and began filling empty terrestrial and marine niches (large herbivores and carnivores). Many mammals returned to the sea independently.
Placenta
organ formed by embryo and mother after implantation -formed by extra embryonic membranes and uterus lining -site of gas, nutrient and waste exchange between mother and embryo -produces hormones necessary to maintain pregnancy -blood is not exchanged between fetus and mother. Capillaries of both come very close and things are transferred from one to another through diffusion. 3 fetal blood vessels in umbilical cord. 2 arteries carry deoxygenated blood to mother (away from heart) and vein carries oxygenated blood towards heart from mother. Opposite of adults were arteries have oxygenated blood.
Smilodon
sabre-toothed tiger 1.5mya- 11000 -lived with human, giant sloths and mammoths. At this time North America looked like Africa. Most likely went extinct due to humans. Pleistocene time period
sexual dimorphism
sexes appear different in size, colour or morphology. ex. elephant seals and lions.
Tarsier
-An anthropoid -among the smallest primates -only entirely carnivorous primate -eyes bigger then any other mammal relative to size. -cannot rotate eyes and must look ahead.
Homo neaderthalensis
-Discovered in Neander Valley in Germany -Recent homo species -coexisted with homo sapiens -disappeared 30 000 years ago, possibly due to extinction from homo sapians -short, stocky but powerful build -brain larger than homosapians
Australopithecus
-One may our direct ancestor -Hominid -Brain 35% size of modern human brain -"Lucy" found in Ethiopia has the most complete skeleton -Provided evidence that bipedalism evolved before our brains did
Platypus
-eastern Australia -use bill to dig for crustaceans and worms. -build nest in riverbank -lay 2-4 eggs that hatch after 8 days. -nurse for 5 months -poisonous spine on the back foot of males.
Prototherians
-egg laying mammals -egg is incubated by parents until it hatches and females lack placenta. -Have mammary glands but lack nipples and young suck milk from fur. ex. Platypus and Echidna found in Australia and New Guinea.
Primates
-arboreal ancestors -230-270 species -Grasping limbs with opposable thumbs -forward facing eyes and depth perception -big cerebrum -highly social with reduced brood size and extended parental care. Two major groups: Prosmians and anthropoids
Homo erectus "standing"
-believe to be the first hominids to leave Africa (spread to Eurasia) -1.6 million years ago -250 000 years ago -first to use fire -As large as modern humans but smaller bran and thicker skull
Marsupials
-do not lay eggs, viviparous (birth life young) and some have placenta -short gestation and long nursing period in pouch -birth after short internal development -newborns crawl over mothers body and into the pouch, where they attach to the nipple in the pouch and complete development -350 species (kangaroos, koalas, opossums ) -Found in north and South America and Australia -Diverged from other mammals 100 mya. Marsupials in North America are extinct except opossums
Central Nervous system
-dorsal hollow tube of nervous tissue -large cephalic ganglion (brain) -long tube inferior to brain is the spinal chord -protected by bone Incoming are hormones, unconscious physiological info (blood pressure, internal body temp) and conscious sensory info (sight, sound and smell) and out coming info is our voluntary control, nerve hormones and autonomic commands (heart rate, sweating and salivation)
Homo habilis "Handy/skillful"
-early homo species -Lived in Africa 2.5-1.5 mya -first to use tools 2 million years ago -shorter jaw and bigger brain
Interbreeding of homo species
1.5-2.1% of DNA in non africans in neanderthal. Humans most likely came across other human groups that we haven't found fossils of yet. Example: Denisovians that we have only found teeth for, but 4-6% of Melanesian DNA (Australia and New Guinea) is Denisovan. Africans have 2% of DNA from an unidentified archaic species. Percent of Neanderthral DNA has decreased over the years do to natural selection against it (many disease and genetic defects). Some things can also be helpful , ex denisovan DNA helps tibetans at high altitudes.
First mammals
First true mammals evolve 225 million years ago (triassic) and loved during the time of dinosaurs. They were small arboreal, shrew like creatures that ate insects and were nocturnal based on eye size. Had improvements to middle ear and better hearing. ex. Hadrocodium wui that was found in china and existed 195 million years ago. Was 32mm long and weighed 2g. Had a large brain in comparison to its eyes. Had middle ear derived from jaw and modern day representation would be the elephant shrew.
Ardipithecus
Homonids (not necessarily direct ancestor of humans) -In 2009 fossil were uncovered dating back to 4.4 million years ago -walked upright and dint use arms for walking as chimps do but retained primitive big toe for grasping.
Apes
In the anthropoid group -lack tails Gibbons: lesser apes, smaller than the others and tend to be arboreal. Orangutangs: too large to cross from one tree to another by branches and must go down to the ground and climb up another. African apes (gorillas, chimpanzees, bonobos, Homonids) Genetically humans are most closely related to bonobos.
Skull morphology
Key difference in skulls is present between amniotes. Variation in size and temporal fenestae (holes) that provide more surface area for muscle attachment. Anapsids (turtles)- eye and nostril hole Synpsids (mammals)- eye, nostril and extra hole. Diapsids (dinosaurs and birds)- eye, nostril and two extra holes
