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83 Cards in this Set
- Front
- Back
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What are the four main tenants of Darwin's theory of natural selection?
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1. In each generation, more offspring are born than can survive.
2. These offspring exhibit variation. 3. Some of these variations are better suited for survival. 4. The competition that exists between these offspring for limited resources results in differential survival in favor of the better suited. |
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Fitness
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The relative reproductive success of an individual. Get food, survive, mate, AND reproduce.
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Adaptation (Process)
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The functional response of populations to the environment that results from natural selection and enhances fitness.
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Adaptation (State/Feature)
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A feature produced by natural selection for its current function.
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What makes a feature an adaptation?
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Must be: heritable, functional, adaptive, and evolved for its current function.
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Preadaptation
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A feature that fortuitously serves a new function. (Kea parrot using beaks to tear into sheep, rather than shells and nuts.)
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Exaptation
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A feature evolved for a different function (or no function at all) that has been co-opted for a new purpose. (Skeleton started out in fish as calcium storage, ours is for support and organ protection.)
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Historical Artifact
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When a specific character or trait can be explained just by saying that it goes back to a common ancestor, and it worked for them. (5 Fingers)
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Out-dated Adaptation
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An adaptation for a past environment and not the current one. (Calabash tree has a hard-shelled fruit that evolved along with the gomphothere, but they went extinct 10,000 ya; seed dispersal is now out-dated.)
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Constraint through character correlation
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A characteristic that changes because it has to in conjunction with another. (Bird beak width and depth are linked this way.)
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Physical Constraint
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Any adaptation must obey the laws of physics. (No land mammals the size of whales.)
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Genetic Constraint
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When a population has low genetic diversity. (Cheetahs are all almost completely genetically identical because they were repopulated by a small group, causing a genetic bottleneck.)
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Directional Selection
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Pushes the distribution of a trait in a certain direction. Example: butterflies that are lighter don't get eaten as much, so the frequency in the population of darker ones declines.
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Stabilizing Selection
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When natural selection is taking out the extremes and variability goes down. Example: very low or high birth weigh will be selected out because both can cause death.
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Disruptional Selection
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When the average is being selected out; all that will remain are the outliers. Example: 3 type of butterfly in a population; A specializes on one flower, B specializes on a different one, and AB is mediocre at feeding from both flowers. A and B will outcompete AB.
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How is artificial selection evidence for natural selection?
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It shows large amount of morphological change in short periods of time; it operates the same way, but the selecting pressures are human preference instead of nature.
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How does nested hierarchy support evolution?
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The way life has evolved can be organized into nested groups on a tree by patterns of variation and their relation to one another. (The tip of two branches from the same limb are closely related.)
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Homology
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A similarity due to common ancestry.
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Five types of homologies
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1. Comparative biology: tetrapod forelimbs
2. Comparative behavior: nest building in birds 3. Developmental Biology: human embryos with tails 4. Molecular biology: genetic homology (humans 25% alike with roundworm) 5. Vestigial structures: useless items that still exist (feathers on an ostrich) |
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Occam's Razor
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All things being equal, the simplest solution is the best.
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Ambulocetans natans
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A whale with legs that had a hoof on each toe. Probably lived and moved somewhat like an alligator.
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Sexual Selection
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The effects of the struggle between the individuals of one sex, generally the males, for sexual access to the females. Happens when direct competition or mate preference play a role in selection of mates.
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Sexual Dimorphism
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Differences in size or color between the males and females of a species. Ex. Peacock and Peahen
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How males compete for mates
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1. Direct competition; fighting
2. Mate preference; being attractive |
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Female role in sexual selection
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Sit back and pick the best mate
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Run-away Sexual Selection
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When female selection of traits breeds disadvantage into a species. Ex. birds with long tails get more mates, long tails are selected for; keep getting longer to the point of being a hindrance to the individual, but the trait survives because that is what the females want.
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"Good-genes" Model
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When ornamentation is seen as an indicator of genetic quality. Ex. if bird has costly super-long tail he must be more well suited for survival.
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"Pre-existing Bias" Model
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When females just like the look of something; a sensory bias is built into their genes for preference for a specific trait.
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Human characteristics caused by sexual selection
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Males: facial hair, muscle mass, penis size.
Females: fat deposition, relative hairlessness, permanent breast swelling, concealed ovulation. |
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Macroevolution
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It entails the processes by which species and the high taxa are created.
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Biological Species Concept
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Groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups, and can produce fertile offspring. This theory ignores appearance (happy face spiders).
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Ecological Species Concept
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Natural selection creates and maintains species in nature. Because they fit into the world in different ways, hybrids are not well suited for a niche, so they are selected out.
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Recognition Species Concept
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When two organisms recognize each other as mates. Ex. the eastern and western meadowlark look exactly the same, but do not recognize each other as mates because they have different mating calls.
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Phylogenetic Species Concept
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A species is a tip on a phylogeny; the smallest set of organisms that share an ancestor and can be distinguished from other branches.
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Morphological Species Concept
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Organisms are classified in the same species if they appear identical by anatomical criteria. This is used when species do not reproduce sexually; some are known only from fossils.
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Speciation
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A lineage splitting event that produces two or more separate species.
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Allopatric Speciation
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Populations that become physically separated begin to diverge. If populations are isolated long enough, new species emerge when genetic differences prevent interbreeding.
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Parapatric Speciation
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Differences in mate choice and selective pressure causes speciation. (The individuals on the edges begin to diverge.)
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Sympatric Speciation
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Happens with one population all living in the same place diverges solely due to selective pressure. (Flies mating preferences.)
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Anagenesis
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The transformation of a single species into another over time. A to B to C.
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Cladogenesis
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The formation of a species where one or more new species branches off from an original. Species A - Species B - Species C.
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Punctuated Equilibrium
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Proposed by Gould and Eldrige in the 1970s as an explanation for the sudden changes found in the fossil record. Species go through long periods of stasis until something changes, and then they rapidly change with it. (Cladogenesis)
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Adaptive Radiation
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A huge burst of speciation where one root species branches out into five or six species. Happens when there are suddenly unoccupied niches; like extinction of the dinosaurs. Ex. Cichlid fish
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Phylogeny
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The study of evolutionary history and relationships between organisms. Hypothesized relationships can be tested and falsified.
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Classification
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Classification is organizing taxa into hierarchical groups.
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Character
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Any heritable trait.
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Phenetic Approach to Phylogeny
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By recording as many characters as possible, evolutionary relationships should emerge. This theory doesn’t work because you have to take genetics into account. You have to use characters that are evolutionarily informative and tell us about relationships.
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Evolutionary Approach to Phylogeny
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These people believe that the strange species with autapomorphies (like humans) should be in their own groups (not in the same group as the other great apes).
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Cladistic Approach to Phylogeny
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Cladists think that autapomorphies should not affect classification. Humans belong with the great apes, despite our huge differences from nearest relatives. (Birds then, would be dinosaurs or reptiles.)
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Synapomorphy
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A character that is a shared derived character; one thing that two lineages have in common from a common ancestor whose ancestor, in turn did not have. Examples: plants are grouped together by their leaves; tails in old world monkeys, no tails with great apes.
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Symplesiomorphy
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A trait which is shared between two or more taxa, but which is also shared with other taxa which have an earlier last common ancestor with the taxa under consideration. They are therefore not an indication that the taxa considered are more closely related to each other than to the more distant taxa, as all share the more primitive trait. (Most are homologies; this depends on what level of the phylogeny you are looking at.
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Autapomorphy
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A derived trait that is not present in the closest related species and therefore was not a trait that came from the common ancestor of the species. (Humans)
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Convergent Character
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A character with separate evolutionary origins, but are superficially similar because they evolved to do the same function. Examples: bird and bat wings; body shapes of sharks and dolphins.
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Monophyletic Group
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A common ancestor and all of its descendants; also called a clade. (What we want.)
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Paraphyletic Group
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A group that does not contain a common ancestor and all of its descendants (i.e. including all the great apes except humans, hominin or hominid; what the evolutionary approach people think). (What we aren’t sure about.)
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Polyphyletic Group
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A group that doesn’t contain the most recent common ancestor and all of its members (like grouping by warm-blooded-ness). (What we REALLY don’t want)
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East African Geology
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Plate tectonics are tearing east Africa apart and creating sites like the Olduvai Gorge where millions of years of strata can be seen. Volcanoes also help in dating fossils by allowing argon-argon dating to bracket fossils found in the layers between the ash.
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Breccia
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A natural form of concrete that many African fossils are trapped in. Fossils encased in breccia have to be bathed in acid to remove most of it, then micro-scribes have to be used to remove the rest by hand.
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“Little Foot”
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An Australopithecus Africanus fossil found at Sterkfontein in South Africa. It is an incredibly complete specimen that has been stuck in breccia for 15 years!
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Differences in South Africa and East Africa
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There is no volcanic activity or plate tectonic separation going on in South Africa like there is in East Africa. In S. Africa, fossils are found mostly in limestone caves.
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What are the major evolutionary changes that account for differences between apes and humans in the cranium?
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The brain size increasing caused the need for a larger brain case, so for example the post-orbital constriction is no longer seen in humans. Bipedalism required a change in the location of the foramen magnum from the back of the head to underneath it, pointing down towards the torso. Change in diet also resulted in changes to the shape of the skull; we no longer need large muscle attachments on the skull for increased jaw/chewing power, and changes in dentition change the shape of the face and mandible.
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17 differences between the cranium of apes and that of humans
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1) Brain size 350-400 cc & 1400 cc; face projection prognathic (muzzle-like) & orognathic (flat); post-orbital constriction lots & none; temporal fossae (hole behind cheek bone) big & small; foramen magnum orientation back & under; widest part of skull bottom & near top; rear skull shape nuchal crest (big crest for muscle attachment) & smooth with small occipital protuberance; brow ridges large with supraorbital sulcus & small with no sulcus; nose no projection & projection; diastema (space between canines) large & none; mandible shape u-shaped & parabolic; temporalist muscle attachment strong, may form sagittal crest & weak temporal lines; face height long & short, canines large, sexually dimorphic & small not very dimorphic; canine fossa (dent in cheekbones) none & present; premolar shape semisectorial & not semisectorial (premolars slide against canine -- that fits into the diastema-- and sharpens it), chin none & present. *Enamel is thin on apes and thick on humans.
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What are the major evolutionary changes that account for differences between apes and humans in the postcrania?
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Bipedalism caused shift in center of gravity, changed shape of pelvis, valgus angle in legs, arches in feet. Manipulation changes altered the arm and hand structure.
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What are the specific differences between apes and humans in the postcranium?
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Thorax shape (ribs) wide at bottom & curved in at bottom to help support organs; pelvic shape narrow and tall & broad and flaring; valgus angle (angle of thigh bone outward-- allows transfer of weight) none & large, big toe totally opposable & in line with the rest of the toes, foot arch none & high, toe length long & short, body proportions relatively long arms and short legs & short arms and long legs, thumbs short, unable to touch tips of other fingers & long and fully opposable, and finger length long & short.
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Taphonomy
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Literally means “law of burial.” It is all the processes behind how a living organism becomes part of the fossil record. It reconstructs all the processes from the fossil you find back to the original community of plants and animals.
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Osteodontokeratic Culture
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A South African australopithecine culture proposed by Raymond Dart; they supposedly used “bone, tooth, and horn” tools. He hypothesized this culture because of all the instances of human and animal bones found together in caves; he thought that hominids had to have been bringing the animals there, therefore they had to have weapons of some sort. He was wrong.
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How did the study of taphonomy alter the interpretation of South African sites?
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Taphonomy proved that in the caves and pits where all the human and animal bones were that they were actually the leftovers from big cats who would drag their prey up into trees that would grow close to deep fissures in the ground (because of the gases coming up out of them, they grew better there). When the cats were done eating their kills, the bones would drop down into the cracks and pile up in the caves.
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What does carnivore damage look like?
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Carnivore damage follows a particular sequence of events. The ends are chewed off the bone, then the marrow is sucked out. This type of chewing leaves U-shaped grooves in the bone.
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What does rodent damage look like?
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Two U-shaped grooves with flattened bottoms next to each other.
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What does a cut mark look like?
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Straight lines gouged into bone. (When looking at a cross-section of the bone, the indents are more v-shaped.)
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What are oxygen isotope stages? How are they determined? What oxygen isotopes are involved? What is a deep sea core?
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Isotope stages: warm and cold phases in the earth’s paleoclimate
Determined by: using deep sea core samples to measure the oxygen isotope ratios. What isotopes: 16O and 18O Deep sea core: a narrow column of sediments taken by drilling into the sea-bed with a piston-corer. Such cores can provide a more or less complete record of climatic changes through the Quaternary system. The superimposed layers of detritus include sediments and the fossil skeletons of sea creatures. |
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How do carbon isotopes help us reconstruct paleoecology? What carbon
isotopes are used? |
Carbon isotopes can be used to determine what was going on in regards to climate because all plants pick up carbon dioxide from the air, but they photosynthesize the carbon in different two different ways. C4 plants are grasses and their carbon signal is 12% carbon, C3 plants are trees, shrubs, and tubers and their carbon signal is about 26% carbon. By looking at the fossils of herbivores that ate the plants, and the carnivores that ate the herbivores that ate the plants, we can see what the environment was like based on the carbon isotope ratios present in the bones.
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What are the age limits of the Miocene, Pliocene, and Pleistocene?
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*Holocene: 10,000 kya ~
Pleistocene: 1.6 - 10,000 kya Pliocene: 5.3 - 1.6 mya Miocene: ~ 5.3 mya |
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Relative Dating Techniques
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Paleomagnetics, Fluorine, and biostratigraphy
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Absolute Dating Techniques
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Radiometric, TL, ESR, Amino-acid racemization
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Fluorine Dating
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Fossils absorb fluorine from the groundwater, so a fossil that has more fluorine in it than another from the same area would be older. This is specific to the area; you have to know how much fluorine is present in the water because it varies.
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Biostratigraphy
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Dates a fossil based on known dates for other fossils with it. So, if you find a fossil hominid with a fossil horse that has been radiometrically dated to 2 - 3 my; then it is safe to say (usually) that the hominid is around the same age. *The species you are using to date your fossil cannot be in stasis -- this is all based on the assumption that species evolved at the same rates in different places.
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Paleomagnetic Dating
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Paleomagnetic dating is based on changes in the orientation and intensity of the earth's magnetic field that have occurred over time. The magnetic characteristics of the object or area (e.g., a section of the sea floor) in question are matched to a date range in which the characteristics of the earth's magnetism were similar. Paleomagnetic dating is also based on the fact that the earth periodically reverses the polarity of its magnetism. Different igneous and sedimentary rocks are rich in magnetic particles and provide a record of the polarity of the earth when they were formed. These patterns will be reflected in various geological contexts, such as stratigraphic sequences. Scientists date these changes in polarity through another technique, such as potassium-argon radioactive dating. This has resulted in the calibration of the pattern of changes in the earth's polarity over many millions of years. Scientists can date a new profile by measuring for changes in polarity within the strata and then matching the sequence to the calibrated master stratigraphic sequence of geomagnetic polarity reversals.
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Underlying Principles of Radiometric Dating
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Naturally occurring radioactive materials break down into other materials at known rates. This is known as radioactive decay. Radioactive parent elements decay to stable daughter elements. Many radioactive elements can be used as geologic clocks. Each radioactive element decays at its own nearly constant rate. Once this rate is known, geologists can estimate the length of time over which decay has been occurring by measuring the amount of radioactive parent element and the amount of stable daughter elements.
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What are the different types of radiometric dating?
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1. Potassium/argon using the potassium-40 isotope which slowly decays to argon-40.
2. Fission track dating (which is often used in combination with radio-potassium methods). This uses the isotope uranium-238, which decays through powerful fission. 3. Radiocarbon dating is the best known method of all radiometric dating, but because of its short time-depth, can only be applied to the latest phases of human evolution. This dating method uses the isotope carbon-14 that decays into carbon-12. 4. Uranium series technique, which relies on the decay of the radioisotopes uranium-238, uranium-235, and thorium-232, all of which decay to stable isotopes of lead. |
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Half-life
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The amount of time that it takes for half of one parent isotope to decay into the daughter isotope.
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How does fission track dating differ?
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Fission track dating is a radioisotopic dating method that differs from other absolute dating methods because it depends on the spontaneous fission (breaking apart) of the nucleus, which blasts little tracks into rock, as well as the usual decay process. We can date this rock by counting the tracks, the more tracks, the older. This technique can only be applied to material (obsidian, pottery) that has been fired, because the clock has to be set back to zero by the heat produced in that fire.
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How does amino-acid racemization work?
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After death proteins in bone break down into free floating amino acids. L amino acids exist in living animals, D amino acids mostly do not occur in living animals. You can look at the remains of something once living, and compare the ratio of L aminos to D aminos to tell how old something is. Amino acid racemization works on fossil bone, shell and egg shell. A problem with this method is that the process of L aminos changing into D aminos speeds up when the weather is hot and slows down when the weather is cold. You have to have an understanding of the climate from the past; works well on things that have been in a constant environment like a cave.
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