Lecture'23'Bio''Movie'Introduction2''Takes'place'in'the'high'arctic2'drops'to'50'degrees'below'freezing.''Arctic'fox2'the'only'reason'it'doesn’t'freeze'to'death'is'because'it'is'mammals'and'that'is'has'the'ability'to'use'the'food'it'eats'to'keep'its'body'warm.'Mammals,'including'humans'are'warm'blooded.'Its'body'is'insulated'with'fur.'Warm'bloodedness'is'the'reason'why'mammals'are'so'successful'on'earth'''Mammals2''• Smallest'class'of'the'five'classes'of'vertebrates'• Only'about'5,500'species'• Humans'are'mammals'• Mammals'get'very'big'• Both'largest'land'mammal'is'the'elephant'• Largest'aquatic'mammal'is'the'blue'whale'• Over'70%'of'mammals'are'rodents,'bats,'etc.'SMALL''Mammal'History:'• Have'been'around'for'a'while,'since'the'a ge'of'the'reptiles'• Around'220'MYA,'our'mammalian'ancestors'were'mostly'small,'shrew2like,'insectivorous'(only'ate'insects)','arboreal'(confined'to'trees),'and'nocturnal'• We'believe'that'Mammals'survived'the'extinction'of'the'dinosaurs'(specific'time'period)'because'we'are'endothermic.'• Without'competition'of'the'dinosaurs,'mammals'actually'diversified'and'they'gained'prominence'in'terrestrial'ecosystems.'• The'climates'varied'greatly'during'this'period'when'mammals'were'at'their'peak'(6522'MYA),'ranging'from'tropical'and'true'ice'ages.''• During'the'last'15'million'years,'mammal'numbers'have'been'decreasing'• 'Some'species'are'no'longer'here,'Woolly'Mammoth,'Giant'ground2sloth'(fossils'found'by'Darwin'in'South'America),'Cave2bears,'Sabertooth'Cats.'• Different'theories'as'to'why'these'large'mammals'have'died'out.'We'think'it'is'most'likely'due'to'the'rising'predominance'of'humans''5'Common'Mammal'Traits:'Mammals'are'unified'by:'• Hair'o Even'whales'and'dolphins'have'sensitive'hairy'bristles'on'their'snouts.'o Hair'or'fur'is'insolating'o Along'with'endothermy,'hair'allows'mammals'to'occupy'lands'that'were'never'available'to'ectothermic'reptiles,'like'the'arctic'fox.''o Truly'furry'animals'often'have'a'dense'undercoat'of'fur'covered'with'a'fluffy'overcoat.''o The'undercoat'prevents'heat'loss'o Animals'without'a'lot'of'hair'like'whales'and'dolphins,'and'humans…'other'methods'must'be'had'to'keep'warm'o One'example'is'blubber,'thick'layer'of'insolating'fat…'used'in'whales'and'dolphins'o Humans'have'learned'to'wear'clothes'and'stay'indoors'and'warm'our'houses'etc.'o Hair'can'also'serve'other'purposes'like'camouflage.'o A'mammals'coat'is'often'closely'matched'with'to'its'background,'this'is'even'true'for'coats'that'appear'flashy.''o Good'camouflage'hides'patterns'as'well'as'solids'o What'might'be'camouflage'can'be'unclear'to'humans'because'of'our'visual'systems'may'be'different'to'other'animals'o Ex:'orange'antelopes,'easily'spotted'in'green'grass'that'they'graze'on,'but'their'predators,'are'typically'red2green'colorblineded'organisms'and'they'cant'tell'the'difference'between'the'antelopes'and'the'background.'Its'different'to''each'animals.''o Hair'can'also'be'sensory.'–'another'use.''o Whales'and'dolphins'have'lost'most'of'their'hairs'except'for'their'stiff'sensory'hairs'on'their'snouts'o Hairs'often'serve'as'sensory'structures'like'on'cats,'who'uses'them'to'avoid'colliding'with'objects'in'the'dark.''o Hair'can'also'defensive.''o Hairs'found'on'Echidna,'porcupine'and'hea dhoge'o Thicken,'sharp'stiff'hairs.'''• Mammary'Glands:'o All'female'mammals'have'mammary'glands'o Specialized'structures'that'produce'milk,'These'are'typically'in'the'form'of'mammary'glands'that'lead'to'nipples.''o Newborns'are'born'without'teeth'to'facilitate'the'suckling,'and'milk'is'an'amazing'high'calorie'food,'which'is'critical'for'a'rapidly'growing'mammal.'o About'50%'of'the'energy'in'milk'comes'from'fat,'which'is'important'for'the'development'of'the'brain'o Milk'changes'as'the'infant'grows,'to'perfectly'match'the'nutritional'needs'of'the'developing'baby,'whether'it’s'a'mouse,'a'wildebeest,'or'a'manatee.'''• Endothermy'o Has'allowed'mammals'to'survive'these'extreme'environments'from'desserts'to'the'arctic'because'we'can'control'our'own'body'temp.'o The'blood'circulatory'system2'the'more'efficient'blood'circulation'that’s'found'in'four'chambered'heart,'and'mammalian'diaphragm'that'facilitates'improved'respiration'and'therefore'improved'oxygen'delivery'makes'the'high'metabolic'rates'associates'with'endothermy'possible.''o Endothermy'is'also'found'in'birds.''o Endothermy'is'homoplasious'in'mammals'and'birds,'evolved'in'parallel.'''Sweat'Glands:''o All'mammals'have'sweat'glands'o The'sweat'glands'secrete'liquids'that'cool'mammals'via'evaporation'o Important'for'endortherms'that'not'only'have'to'keep'themselves'warm,'but'make'sure'that'they'don’t'get'themselves'too'warm.'''Placentas:'o Mammals'have'specialized'organs,'that'develops'during'pregnancy'to'nourish'their'young2'placenta.'o The'placenta'allows'for'the'developing'babies'blood'to'come'into'close'enough'contact'with'the'mother’s'blood'to'absorb'nutrients'like'water'and'oxygen'while'also'passing'on'the'waste'to'be'cleared'by'the'mother’s'blood'stream.'o This'organ'is'delivered'soon'after'the'baby'is'born.'''In'addition'to'these'5'traits,'mammals'have'some'pretty'spectacular'specialized'adaptations'are'are'present'in'some,'but'not'all'mammals:'• Mammals'have'specialized'teeth'• Mammals'have'fewer'teeth'than'fish,'amphibians'and'reptiles.''• Have'amazing'diverse'teeth'that'closely'match'to'their'typical'diet'• You'can'find'out'what'a'mammal'eats'just'by'look'at'its'teeth.'• Humans'are'omnivorous.''• Many'mammals'are'herbivores,'or'are'highly'dependent'on'plant'matter'for'digestion'• Cellulose,'a'long'polymer'of'glucose…'is'a'major'component'of'most'plants'• 'Mammals'do'not'have'the'enzymes'that'are'necessary'to'break'down'these'long'chains'• Herbivorous'mammals'have'developed'symbiosis'with'bacteria'that'reside'in'the'mammals'gut'and'that'can'break'down'the'cellulose'so'that'the'mammals'and'bacteria'have'access'to'glucose.'• Mammals'also'use'the'protein'keratin'in'many'ways.'• Keratin'is'the'main'component'in'hair,'claws,'fingernails'hooves,'and'horns.''• Hooves'are'specialized'pads'to'protect'the'toes'of'animals'that'run'a'lot'• Hooves'lessen'the'impact'of'repeatingly'landing'on'the'foot.''• Horns,'for'example…'on'an'Impala,'they'are'composed'of'a'core'of'bone'that'are'surrounded'by'keratin.'• Horns'are'attached'to'the'skull'and'are'NEVER'shed.'•
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