mammals – Flashcard
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mammals are what?
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amniotes with hair and milk
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characteristics of mammals
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mammary glands, large brain, differentiated tooth shapes
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mammary glands
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produce milk for offspring that contains fat, sugars, proteins, minerals, and vitamins
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shearing
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incisors and canines
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grinding
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premolars and molars
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how to mammals retain body heat?
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endothermic, hair, layer of fat
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heart
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four-chambererd
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diaphragm
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assists with ventilation
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parental care
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relatively longer
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how do offspring learn survival skills
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observing their parents
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what do they learn from parents
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foraging for food, hunting, locomotor skills, migratory pathways
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early evolution of mammals
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are amniote synapsids
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synapsids all have a what?
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a single, temporal fenestra (a hole behind each eye socket.) in humans, jaw muscles pass through this hole and anchor on the temple
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how were synapsid jaws remodeled?
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two bones that formerly made up the jaw joint (quadrate and articular) were incorporated into the mammalian middle ear (incus and malleus)
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permian period
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299-251 million years ago. synapsids evolve into large herbivores and carnivores
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triassic period
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251-200 million years ago. extinctions cause synapsid diversity to decrease
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jurassic period
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200-145 million years ago. first true mammals arise
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cretaceous period
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140 million years ago. three major lineages emerge
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three major lineages of mammals
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monotremes, marsupials, eutherians
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monotremes
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egg-laying mammals
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marsupials
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mammals with a pouch
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eutherians
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placental mammals
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when did mammals undergo a significant adaptive radiation
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after the cretaceous period
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after the cretaceous period, mammals diverged into what
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carnivores, herbivores, omnivores, terrestrial, flying, and aquatic
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monotremes are only where
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in australia
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how do monotremes secrete milk
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via glands on the belly
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monotremes include what
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four species of spiny anteaters, one species of platypus
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monotreme: spiny ant eater is found where?
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only in australia and new guinea
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monotreme: spiny ant eater beak is specialized for what
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inserting into holes in rotting wood to obtain insects and earthworms
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monotreme: spiny ant eater have what kind of smell and hearing
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gr8
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monotreme: spiny ant eater females lay eggs where
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into their own pouches after about 10 days and young remain in pouch for about 50 days
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monotreme: platypus characteristics
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duck bill, duck feet, beaver tail, otter body and fur
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monotreme: platypus stingers
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venomous stingers on their feet
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monotreme: platypus teeth
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no teeth, they feed on insects, larvae, shellfish, and worms
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monotreme: platypus grinding food
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pebbles and gravel taken in the mouth along with the food help to grind it
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monotreme: platypus eggs
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lay 1-2 and keep them warm against her body inside a burrow
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monotreme: platypus nursing
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bean-sized and nurse for 3-4 months
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marsupials include what
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oppossums, kangaroos, and koalas
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marsupial embryo development
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embryo develops in the female uterus within a placenta and receives nutrients from the mother's blood. they are born before completing development and then crawl inside the mother's pouch and continue development while nursing from the mother's nipple
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break up of pangea: marsupials diversified in isolation
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australia is thought to have been isolated from the rest of the other continents beginning 65 million years ago. south america was much less isolated and experienced immigration when north and south america were joined at the PANAMANIAN ISTHMUS
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supercontinent pangea
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australia broke away and marsupials diversified in isolation
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eutherians have what kind of placenta
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a more complex one that marsupials
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where do young eutherians complete their embryonic development
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within a uterus, joined to the mother by the placenta
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what do molecular and morphological data give on the diversification of eutherians
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conflicting data. molecular: 100 million years ago. morphological: 60 million years ago
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convergent evolution: marsupials and eutherians
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resemble one another because they fill similar ecological niches in their respective habitats
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primates include
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lemurs, tarsiers, monkeys, and apes
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humans are what
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apes
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characteristics of primates
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opposable thumb for grasping, big toe, flat nails, fingerprints, large brain, short jaws, forward-looking eyes, gr8 hand-eye coordination, complex social behavior with high level of parental care
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three main groups of living primates
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lemurs, lorises, and bush babies tarsiers anthropoids: new and old world monkeys, apes
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primates: anthropoids evolved where and when
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in the old world (africa and asia) perhaps 45 million years ago
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primates: anthropoids include what 2 kinds of species
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arboreal and ground-dwelling
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in the new world (south america), when did monkeys first appear
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25 million years ago
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new world and old world monkeys underwent what
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separate adaptive radiations during their many millions of years of separation
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primate anthropoid monkeys
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most are dirunal, most live in social groups
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diurnal
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active during the day
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anthropoid primates: apes includes
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gibbons, orangutans, gorillas, chimpanzees, and bonobos
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gibbons and orangutans are primarily what
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arboreal
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gorillas and chimpanzees are highly what
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social
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when did apes diverge from old world monkeys
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25-30 million years ago
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the last common ancestor of monkeys and apes lived about how many years ago
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25 million
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the last common ancestor of chimpanzees, bonobos, and humans lived about how many million years ago
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6-8
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considering only the base substitutions in genes shared by humans and the other apes, humans and chimpanzee and humans and bonobo DNA differ by what
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1.2%
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human, chimpanzee, and bonobo DNA differ by what percent with gorilla, orangutans, and rhesus monkeys?
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1.6% 3.1% 7%
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analysis of the entire genome including DNA sequences that have undergone duplications, deletions, and insertions show what
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human DNA differs from bonobo and chimpanzee DNA by 4-5%
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more than __ of the human genome is more closely related to the ___ or __ genome than either the __ or __ are to each other
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3% chimpanzee or bonobo
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human DNA varies from other humans by
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around 0.1%
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2 common misconceptions about human evolution and their corrections
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1. early hominins were chimpanzees - hominins and chimpanzees shared a common ancestor 2. human evolution is like a ladder leading directly to homo sapients - hominin evolution included many branches and co-existinf species differing in shape, body size and diet; but only humans survive today
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paleoanthropology
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study of human origins
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the earliest hominins are more closely related to humans than to
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chimpanzees
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fossils of how many different species of hominins have been unearthed
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20
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oldest known hominin fossil dates back to how many mya
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6,5
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most of the fossils have been unearthed where
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in eastern and southern africa
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characteristics of early hominins
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reduced number of canine teeth, flat faces, flat jaw, foramen magnum, shape of pelvis and leg bones suggest tendency towards bipedalism, small brains, small stature
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foramen magnum
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large hole through which the spinal cord passes. is located underneath the skull
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the earlies hominins
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ardipithecus
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ardi is how old
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4.4 my
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ardipithecus ramidus bones suggest what
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increasing dependence on bipedalism for movement
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hominin diversity increased dramatically when
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2-4 million years ago
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australopith
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diverse paraphyletic group of hominins. fossils first discovered in 1925. two categories: gracile and robust
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gracil australopiths
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slender, jaws adapted for chewing foods
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robust australopiths
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sturdy skulls with powerful jaws and large teeth for grinding and chewing hard food
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gracile australopiths: australopithecus anamensis
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the earliest member, closest time to ardipithecus
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gracile australopiths: australopithecus afarensis
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discovered in ethiopia in 1974, known as lucy. 1m tall, softball sized brain, long jaw, bipedal, longer arms for arboreal locomotion
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gracile australopiths: australopithecus africanus
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fully erect with human-like hands and feet but brain was only 1/3 our size
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the laetoli footprints of tanzania
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made about 3.6 million years ago. A. afarensis fossils were found in the same sediment layer. trail is 88 feet long and contains 70 footprints made by 2 short hominins. prints were discovered by leakey's team in 1978. show bipedalism. big toes were in line with the rest of the foot. gait consisted of heel-strike
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advantages of bipedalism
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10 million years ago, himalayan mountain range was formed. drier climate caused forests of africa and asia to be replaced by savanna grassland with few trees, chimpanzees expend 4 times as much energy moving across an open expanse of ground, bipedal walking is energy efficient in the arid environments inhabited by himins at the time
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hominins began to walk long distances on 2 legs around how many mya
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1.9
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robust australiopith include and are characterized by
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paranthropus bpisei and paranthropus robustus. characterized by much sturdier jaws and wide cheek bones
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robust australiopith: paranthropus boisei
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massive cheek teeth and cheek bones for powerful chewing muscles, widely flaring zygomatic arches, 510cm^3 brain, ate fruit and other soft foods but could eat tougher plants when preferred foods were scarce
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robust australiopith: paranthropus robustus
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flat face, anterior facing cheekbones allows more space for chewing muscles to pass behind, large molars and premolars for grinding tough foods, tool use is evident such as bone use to dig termites out of mounds
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tool use in great apes
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orangutans and chimpanzees use sticks to probe for insects, chimpanzees use rocks to smash shells or hard fruit, chimpanzees chew leaves until the leaves can soak up water like sponges and cover thorny surfaces with leaves before walking across it
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stone tools were used when and how
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used 2.5 mya by hominins to cut flesh from animals. these hominins had small brains
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tool use may have originated before the evolution of what
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large-brained homins
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homo habilis
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earliest homo genus, 2.4 to 1.6 mya. stone tools have been found with it, giving its name "handy man." shorter jaw and larger brain volume than earlier hominins
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homo ergsater
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first fully bipedal, large brained hominin. discovered in arid environments. associated with complex tools. burnt bone suggest it may have used fire to cook food. existed between 1.9-1.5 mya. shows a decrease in sexual dimorphism. more pair-bonding
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sexual dimorphism
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size difference between sexes
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homo erectus
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originated in africa by 1.8 mya. first hominin to leave africa. appears to have migrated as far as indonesia
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turkana boy: homo erectus fossil
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a boy age 8-9, had a disease of the spine, elongated legs and shorter arms, erectus is associated with the first hand axes
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neanderthals
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lived in europe and the near east from 350000 to 28000 years ago. thick bones and stocky with larger brain: they buried their dead with flowers. gene flow occurred between neanderthals and homo sapiens: genome identical at 99.7% of the nucleotide sites
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neanderthals behavior
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hunters of reindeer, seals, molluscs, dolphins, and fish. fashioned spears for hunting. cooked with fire. made sophisticated flake tools and ornamental objects from stone and bone. made sewing needles from bone and scraped the flesh from animal hide to make fitted clothing.
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earliest neanderthal fossil
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the old man of la chappelle: male with severe osteoarthritis. gave early reconstructions of neanderthals a slouched appearance with bent knees and an opposable big toe
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characteristics of homo sapiens
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upright posture with bipedal locomotion, larger brains capable of language, symbolic thought, artistic expression, manual dexterity, reduced jawbones and jaw muscles, shorter digestive tract
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humans homo sapiens
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200000 years old. oldest fossils dates back 115000 years ago and are from the middle east. humans first arrived in the new world 15000 years ago
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homo sapiens were the first group to show what
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symbolic and sophisticated thought. in 2002, a 77000 year old artistic carving was found in south africa
