Arch 131 Studyguide.docx

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Simon Fraser University
ARCH 131
Birute Galdikas

1 The differences between Reptiles and Mammals illuminate something about human beings something about primates and the sweep of human evolution The Differences between ReptilesMammals 1 Warmblooded o Mammals maintain a constant body temperature o This means that they are adapted to survive in more cold environments o If you have a metabolism like a mammal does that means you have energy it doesnt matter what happens in environment you have energy you have a high metabolic rate o With energy you can scurry around fight mate you can do a lot of things not at the sufferance of the environment but whenever you feel like it or whenever its opportunistico But theres a cost that they pay to have a high metabolic rate which is you need a constant food supply o Theres a cost and theres a benefit lots of reptiles survived the cretaceousthere are thousands of species of reptilesamphibians who are terrestrial or semi terrestrial obviously in evolution some decided to pay the cost and others decided not to pay the cost o But when you pay the cost you are freed from the environment in one way activities but you are stuck to the environment in another way you constantly need to find food o A students python Reptile coldblooded could be left alone for a long time 2 week vacation without being fed and when the student came back from vacation the python was very interested in the student because it needed to be fed o The longest record for a snake not having food and having survived three years thats the benefit of being cold blooded o Thats why one of the reasons its been proposed that all the big predators in Australia are reptiles because we know that Australia is one of the continents that has been increasingly drying up and has had very unpredictable weather patterns o So you pay a cost but get a benefit2 Reproductive economy o Mammals produce few offspring relatively speaking o So a pigs may produce 10 in her litter a tiger may produce 2 cubs so mammals dont produce very many offspring at one timeo World record One woman had 27 kids in Indonesiathats an awful lot for any mammal o Reptiles lay eggs they can produce hundreds of offsprings they may not survivebut they produce hundreds of offspring o This reproductive economy is connected to the fact that in addition to the few births most mammals undergo prolonged growth period associated to the production of milk in their mothers this means they are dependent on their mothers for a longer period of time than a reptile o Most reptiles once the eggs hatch thats it in fact most reptiles dont care for their eggs o So this reproductive economy is not just that mammals produce fewer offspring but mammals have post partition or birth care and this is associated with the milk producing glands that characterize the mammalian class 23 Mammals have a more complex and bigger brains o Mammals play mammals scheme mammals deceive mammals do all kinds of things that a reptile simply cant do o Reptiles have a basic brain they dont have a cerebral cortex perhaps they dont even dream we dont knowo Mammals definitely have more complex and bigger brains o Even an ordinary snake to a mouse the differences are overwhelmingThese three characteristics have been seen before when we discussed what characterizes the primate orderThe saying common expression more fun than a barrel of monkeys we know that monkeys are very active they dont sit still so primates are very active that might not be the characteristic that totally distinguishes them from the rest of the mammalian order but it is one of their defining characteristicsPrimates probably produce less offspring than other mammalsA wild female orangutan may have only four offspring in her entire life and live to be 50 or 60 thats reproductive economyOur brains are so big that they literally cant get any bigger and they cant get any bigger because if our infant brains got any bigger human babies would not be able to pass through the birth canal even now human babies are basically fetusesA monkey baby baboon baby leaves the mothers birth canal and is clambering about and jumping a human baby leaves the mothers birth canal and the baby is virtually helpless and this is because we have these big brains if we waited until comparatively the human infants brain was the same size relatively speaking of the baboons brain the infants would be born at the equivalent of 18 months and destroy the mothers birth canalIf you think about this Primates are the Hyper Mammals Super MammalsBecause we took these trends that foreshadowed were foreshadowed when the earliest mammals evolved from reptiles and we took them to the greatest extremeHumans are who they are because they are primates and primates are who they are because they took these mammalian trends that differentiated them from the reptiles and carried them to extremes Why are we discussing the reptiles Because the difference between reptiles and mammals is what makes us different what makes primates who they are3 Mesozoic Began 225 MYA million years agoThe Mesozoic is the Age of Reptiles The first egg laying mammals appeared sometime in the first period of the MesozoicThis is really where our story begins our story as primates During the Mesozoic there were mammal like reptiles called Therapsidsthese were like a cross between a dog and a lizardDuring the Mesozoic the Therapsids were crowded out and they were crowded out by the Dinosaurs so clearly they Therapsids who were mammals in the making did not successfully compete with the dinosaurs Why We dont know At the end of the CretaceousCretaceous is the last Period of the Era Mesozoic That there were little mammals and some of these mammals were insectivores and recent research indicates that there was a greater variety of mammals and some of them even bigger than we thought At the end of the cretaceous what do you haveWarm moist swampy worldDinosaurs are reigning supremeYou have little mammals that even the biggest of the mammals are medium sized by modern standards maybe the biggest one is the size of the beaver or house catBut you have them they evolved but they dont seem to be going anywhere like the Therapsids there around very mammal like but didnt go anywhereBut then something happens at the end of the Cretaceous the dinosaurs go extinctWhy did the dinosaurs go extinct Mary Larsen Cartoon two dinosaurs smoking cigarettes the real reason why dinosaurs went extinct An asteroid or something from outer space hit the earth and produced the equivalent of a nuclear winter probably a lot of smoke and dust in the air temperatures changed global climate change but much more drastic than what we are talking about nowDinosaurs went extinct and the reasons why had to do with their own particular adaptationsbut those little creatures didnt go extinct so suddenly the world was laid open to them
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