exam-1-study-guide-human-evolution.pdf

lOMoARcPSD|46591595 Exam 1 Study Guide- Human Evolution Introduction To Human Evolution (Washington University in St. Louis) Scan to open on Studocu Studocu is not sponsored or endorsed by any co...

lOMoARcPSD|46591595 Exam 1 Study Guide- Human Evolution Introduction To Human Evolution (Washington University in St. Louis) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 Exam 1 Study Guide Lecture 1- Class Introduction to Human Evolution Fields of Anthropology: Cultural Anthropology Linguists (languages, and how they evolve) Archaeology (behavior as revealed by material culture) Biological Anthropology (biology of people) ○ Paleoanthropology (human fossil record) ○ Functional Morphology (anatomical systems + their evolution) ○ Primatology (living primates) ○ Paleoecology (reconstruction of past environments) ○ Osteology (skeletons) ○ Paleopathology (archaeological skeletal remains) ○ Growth and Development ○ Genetics/Genomics (evolutionary history + adaptation of humans) ○ Demography (population trends) ○ Population Genetics ○ Human Biology (contemporary human populations + environmental interactions) Why are humans unique? Adaptations (such as…) ○ Ability for manual dexterity ○ Intelligence (large brains) ○ Bipedal ○ Speech and language ○ Conscience/morality/complex cognition/culture ○ Make and use tools Lecture 2- Darwin and Natural Selection Evolution: Define: Change over time Scales of Evolution ○ Microevolution: change in the genetic composition of a population over time Very hard to see ○ Macroevolution: change in the properties of species over time Their appearance, anatomy, physiology (their existence, extinction) ○ Definition has two main components: change and time What was believed? Was unimaginable in the 18th century because of living beliefs ○ Fixity of species: idea that species were created by a deity to be in the form that they are perfect and DO NOT change ○ Short history of the world: the world was created at a certain point in recent history so not enough time to intuitively imagine the organisms around us changing ○ These two ideas EXCLUDE the possibility of evolution Late 18th century ○ But then came out a few environmental scientists who started to believe that humans could evolve Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ “Nothing in biology makes sense except in light of evolution” Darwin did not event the idea of evolution ○ His great achievement was not inventing the idea of evolution BUT rather explaining how evolution worked Jean Baptiste de Lamarck: First person to propose a mechanism for evolution (before darwin) ○ Came up with the statement that things could change over time and came up with the mechanism behind it ○ French natural scientist Lamarckianism: inheritance of acquired characteristics ○ Change occurs in species through what is called THE INHERITANCE OF ACQUIRED CHARACTERISTICS So if you acquire characteristics on your body in your lifetime then those can be passed on Favourable traits develop during life and are passed to offspring Intuitive explanation for evolutionary change Darwin even accepted this - of course disproved ○ He did come up with this idea but used this to explain how things change over time ○ For the most part, Lamarckian is NOT true Alternative Explanation for how Species Evolve -- Charles Darwin and Alfred Russel Wallace: Darwin and Wallace Darwin's Book: On the Origin of Species by Means of Natural Selection (1859) ○ Shortened to: origin of species ○ Proposed an additional mechanism to inheritance of acquired characteristics ○ Both naturalists and used this from the natural world What Darwin did systematically in this book ○ (a) Provided documentation that evolution was a real phenomenon ○ (b) Provided a mechanism to explain how this change occurred This mechanism is Natural Selection All of this through observations of the natural world Example w Sheep ○ The sheep become more wooly over time ○ It is because the farmers have selectively bred the sheep ○ Darwin calls this Artificial Selection Takes place where there are domestic animals Darwin realized that this process organized by people can also occur in the natural world without external forces This is called NATURAL SELECTION Natural Selection: Occurs under four conditions - is an outcome of processes that take place IF conditions are met 1. Variation a. Raw material of evolution/natural selection i. Doesn’t take place without variation ii. And must have a certain quality…. 2. Heritable a. The variation in the population must be heritable Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 b. Passed on to the next generation 3. Competition within the population with respect to a selective pressure a. Between individuals in the population b. Aka. the sheep are kind of competing with each other in that some can reproduce and some will be hunted i. This competition come from pressure from the farmer who is the one selecting 4. Differential reproductive success (fitness) a. Favourable genetic variant spreading through a population b. Might be a mechanic, evade predators, attract males etc. c. Depending on fitness variation (frequency with which an individual reproduces) d. Thar variant will be present in greater frequency in the population and will spread and become prevalent --- ADAPTATION → all of these lead to a process what we call ADAPTATION (allowing individuals with a trait to reproduce more frequency) Slides Examples: Selective pressure on zebras = predators Zebras avoid being eaten by running away → based on the legs (length of legs) X axis = leg length Y axis = frequency in population The shaded in area is called is the positive selection Types of Selection Directional Selection ○ Shift in population average towards a specific variation of the trait Stabilizing ○ No directional shift of population - average becomes stabilized Disruptive Selection Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ Average of traits change but essentially the population splits into TWO morphologies Natural selection is not about survivability it is about REPRODUCTION (not about living or dying) -- competition takes place between individuals in the same population Peacock Example: Females are attracted to male with elaborate feathers ○ But this makes them more prone to predation Inverse relationship between feather length and life expectancy Can also plot feather length with number of offspring ○ Long tail feathers = more offspring ○ Short tail feathers (even if they live through more breeding seasons) = less offspring Ultimately, short feathers live longer than long feathers, but long one’s live for enough time to leave more offspring because of mating presence Antibiotics Example: Some bacteria are predisposed to being resistant to antibiotics So then after 1 week of using it: the resistant bacteria are still alive After 2 weeks: might be able to kill the relative resistant bacteria But if you stop after 1 week (thinking you feel ok) then you do not kill them all, they continue to reproduce and create a strain of RESISTANT bacteria Lecture 3- More on Inheritance Natural Selection: Outcome and naturally occuring consequence when four conditions are met ○ Variation (present in the population) ○ Heritable (variation must be heritable) Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ Competition ○ Differential Reproductive Success (differential fitness) These all lead to ADAPTATION People understood that characteristics are heritable but no one understood HOW heritability worked ○ Mechanism was not completely understand Blending Inheritance: At first it was thought it was a blending of traits from the parents… ○ But here, blending destroys variation (aka the first condition) Example: Can of red and white paint = two cans of pink -- cross these = more pink ○ Blending inheritance is INCOMPATIBLE with Darwin's theory ○ This leads to no variation Without variation there is NOTHING to select ○ Blending inheritance was a major threat to Darwin’s evolutionary theory Gregor Mendel: Mendel went to explain how inheritance worked -- found patterns that other people did not see and published a paper that was discovered 40 years later 1 paper which took 8 years Series of experiments with peas ○ Parent: Round peas (x) wrinkled peas (50% each) F1: ALL round (NOT consistent with blending) (x) ALL round F2: 75% round and 25% wrinkled Aka RR x rr = Rr ○ Weird because something that had disappeared came to reappear (does not agree with the blending theory) Assumptions made ○ Each trait was controlled by a single gene (unit of inheritance) ○ Genetic signal was not identical to the morphology observed Genetic signal: genotype is NOT equal to phenotype Genetic signal underlying a trait = genotype ○ Has to be two parts to the genotype -- parts being contributed had to come together and then be split apart ○ Realized that inheritance is particulate = MENDEL’S LAW OF SEGREGATION ○ Assumption that there is a gene that contributes to the shape of pea Within this there are two alleles (round and wrinkled) RR = homozygous Rr = heterozygous R = dominant r= recessive For each gene there must be multiple ways of expressing the trait called alleles ○ Mendel did not use this trait ○ Dominant allele: one that is expressed phenotypically in a heterozygote ○ Recessive Allele: one that is NOT expressed phenotypically in a heterozygote Based on these assumptions, it shows that inheritance is particulate and based on mathematical characteristics (blending is untrue) Chi Square: Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 Codominance: Red flower x white flower = pink flower ○ Neither allele is dominant Pink carnation is in between the red and white F2: Red (25%), pink (50%) and white (25%) Thought that this was against Mendelian genetics because it happened so fast Other things: traits affected by many genes, or genes that affect many traits Final Notes: Overall, the rediscovery of Mendel’s theories proved the accuracy of natural inheritance ○ At first was thought to be contradictory but eventually mendelian mathematics proved to be fully compatible with natural selection (1930s-40s) period called modern synthesis Birth of population genetics Evolution is defined by microevolution ○ Evolution: changes in allele frequencies in a population over time Modern Synthesis: Population genetics Identify the potential causes of evolution Identified the term MICROEVOLUTIOn ○ Define: Change in allele frequencies over time ○ Change in the genetic composition of a population over time PERCENTAGES OF ALLELES IN FLOWER POPULATION DONT CHANGE Lecture 4- Molecular Basis of Heredity Causes of Evolution: Reminder: change in allele frequency over time 1. Mutation a. Error in the genetic code (code not copied in the correct way) b. Source of new genetic variation that occurs in a population 2. Migration a. Gene flow b. Aka, fish came through a water way in the lake, or fruit flies blown from one island to the next island Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 c. So the alleles might spread 3. Genetic Drift a. Random events that remove individuals in a population from the breeding population i. Ex. bug hits the windshield and dies (random events) 4. Selection a. Alleles which are heritable (which represent favourable variations) spread in the population, these allele frequencies increases b. Unfavourable variations = allele frequency declines Eukaryotic Cell: Contains a nucleus with nuclear material contained in a membrane, other organelles in the cell Mechanisms of Inheritance: Poorly understood until recently Discovered under microscopy In 1677, van Leeuvonhoek discovered sperm cells for the first time Mammalian egg cells discovered by von Baer in 1826 Contents of nucleus discovered to be high in phosphorus by Mieschner in 1868, who can estimate the chemical composition of the material of “nuclein” Fertilization of egg by sperm shown in sea urchins discovered by Hertwig in 1876 Chromatin (chromosomes) formally identified by Flemming in 1879, recognized as nuclein ○ Can see them inside ○ Nuclein = thought to be the material of heredity Chromosomes: We have 46 22 Homologous (Autosomes) and then 2 Sex Chromosomes Was well understood that heredity happens here ○ There was already this idea of the gene ○ Some sense that genes must live on these things Watson and Crick ○ Present a theoretical model about how the chemical is constructed ○ Describes the double helix Rosalind Franklin ○ Worked on ways of visualizing the chromosomes ○ Published in the same set of papers in Nature, has not been forgotten in Science but got screwed in her lifetime and not the full credit she deserved (not the Nobel prize) X-Ray Diffraction: Helped to document the structure of DNA Shadows = caused by parts of the DNA molecule The angle of the lines = the angle of the pitch of the helix Photograph 51—x-ray diffraction of DNA From this was able to measure the distance between the helix (34 fl) and the angle/orientation of that axis ○ Shadows in photograph proved that the double helix was the structure of DNA This discovery was published in the same paper as Watson and cricks description of the double helix structure (exact molecular structure) ○ Watson and crick were shown photograph 51 before their work was completed Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ From that they were able to reconstruct the molecule DNA (Deoxyribonucleic Acid): Anti-parallel Consists of a phosphate, sugar and a nitrogenous base (nucleotide) ○ Phosphates and sugar = strong bonds, which do not break apart ○ Nitrogenous bases form hydrogen bonds with other nitrogenous bases ○ Rails of the ladder Nitrogenous Bases ○ A- T and C-G ○ Hydrogen bonds are weak, which separate during cell division ○ Resulting in strands which can be replicated for the daughter strands ○ Corresponds to building a protein Two sides of the molecule are not identical but preserve the same patterned information Can either partially or fully unzip to expose base pairs of free flowing nucleotides ○ Partially:degree that it unzips corresponds roughly to a gene: segment of DNA that codes for production of some sort of cellular product free floating RNA (ribonucleic acid)—mRNA then join up with template forms from DNA strand and then DNA strand gets replicated mRNA then detaches and DNA rezips and mRNA exits TRANSCRIPTION Transcription: Unzips part of its length ○ Other nucleotides floating around = RNA nucleotides ○ Inverse of template strand means its a duplicate of the strand on the other side This new strand can go through the ribosome ○ First transfer RNA comes with anticodon ○ Moves to the next, another one comes in ○ Amino acid -- dipeptide -- polypeptide chain -- protein ○ Shape and folding = very important to function Extra notes ○ Reads 3 BP at a time (each triplet is called a codon, sequence for a BP) ○ Same DNA sequence is copied ○ tRNA then moves into first position and most with corresponding triplet (second codon is read) AUG - UAC Each tRNA brings an amino acid - protein is the result ○ Gene = sequence of DNA that encloses information for forming a protein Example. Hemoglobin molecule ○ One base pair change = changes the entire shape The molecule changes, then the cell cannot form correctly and oxygen is no longer attracted to the RBC This is called Sickle Cell Anemia ○ Hb attracts oxygen Mitochondrial DNA: Explained by endosymbiosis Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ At some point it thought the cell membrane folded in on itself and then enclosed genetic material inside ○ So this prokaryotic cell is transformed into a eukaryote ○ At some point, some channel of this cell must have engulfed an aerobic heterotrophic prokaryote Formed a symbiotic relationship - producing energy for the outer cell Lineage left it in there and thrived = giving rise to animal cells Other cells that form lineage absorbed other photosynthetic prokaryotes Giving rise to plant cells These are called heterotrophs So these cells survive by eating other cells Thought that they are heterotrophic bacteria Then produced a symbiotic relationship So it provides energy for the cell and then was not digested -- could be dependent on the parent cell Structure of Mitochondrial DNA ○ Two circular loops (only 16569 BP) Only code for 13 proteins ○ Genes do not account for all mitochondrial functions, so the mitochondria are dependent on nuclear gene products ○ Multiple copies in each mitochondrion ○ Not enveloped in a membrane ○ All or nearly all mitochondria in a cell are inherited from the mother Vast majority Some small amount might come from sperm Because egg cell has own mitochondria and sperm’s mitochondria are left behind during fertilization (look at maternal lineage) ○ Subject to high mutation rate Two Types of DNA: 1. Nuclear DNA 2. Mitochondrial DNA Mutation = change in base pair Lecture 5- Biological Species Concept Ernst Mayr- Biological Species Concept: Define: A species is a population of actually or potentially interbreeding organisms that are reproductively isolated from other groups “Isolating mechanism” Reproductive Isolation Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ Horse and a donkey mating to create a mule which is reproductively STERILE ○ Isolating mechanism: fitness characteristic, sterility There is interbreeding taking place between polar bears and brown bears ○ These are examples that are messy? ○ Babboon species can also ○ SO the definition is not wrong but there are messy situations So it works pretty well until there are further complications We have a problem with the biological species concept.. in terms of fossils ○ Reproductive behavior is not fossilized We cannot know if things interbred So it might work for today but does not really work for us in the past George Gaylord Simpson- Evolutionary Species Concept: Was a paleontologist - contemporary to Mayr and proposed the Evolutionary Species Concept ○ Like the biological species concept but ADD time ○ Species: unbroken lineage of populations linked by ancestry and descent ○ Maintaining its identity from other species in space and time ○ Almost certainly true that species are lineage segments indepdent from one another (which in theory makes sense) ○ Problem is application) B time A Anatomy So these things in the black lineage = same species but changing over time ○ But at a certain point in time you might discover there is a divergence that takes place ○ Might give rise to a different evolutionary history ○ So then there become boundaries between species So then we are left with like 2 species There is a difficulty with this model ○ Even though it incorporates time and change over time there is a problem with it But what if it was like this Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ ○ Epistemologically it is hard to know how things link together As paleontologist, we know that a species should be a lineage of populations but we need to find a practical solution to finding these species knowing that we could be wrong We cannot be sure that we are detecting these lineages Only tool we can use to be sure: morphology and anatomy and time Phylogenetic Species Concept: Define: Species is a group of organisms that share a unique suite of primitive and derived traits and that is diagnosably distinct from other such groups We are looking for things that are similar and different and essentially using anatomy to define our groups ○ Basically defining based on morphology ○ Practical but slightly problematic If things belong to the same lineage then they should actually look the same ○ Because they are sharing genes freely between them ○ So these characteristics defining a group should be distinct between lineages The ethos behind this definition = try to approximate the evolutionary species concept Modes of Evolution- Species form in 2 Modalities: 1. Anagenesis: Transformation within a lineage a. Start with an ancestral species changing over time into a descent species b. Or it is one species changing over time c. Mechanism is where new forms appear (a → b) d. Changing from one population into another 2. Cladogenesis: splitting of images a. Ancestral species gives rise to TWO decendants Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 b. Rate at Which Evolution Takes Place: 1. Phyletic Gradualism a. Evolution taking place in a slow gradual steady place b. Slow accumulation of incremental change throughout the lineage that leads to new species/lineage - slow morphological change over time (often associated with anagensis) c. (Diagonal on a graph) 2. Punctuated Equilibrium a. New species occur through a very rapid accumulation of morphological change over a short period of time i. Hard to disern in fossil record because might happen so fast b. Some times of little to no change c. Punctuated by times of rapid change B c Systematics: Define: Science of diversity (consisting of two major parts) 1. Taxonomy a. System of classifying organisms into groups 2. Phylogeny a. Reconstructing the evolutionary relationship between groups Taxonomy: Name things using the Linnaean hierarchy Naming Example: Kingdoms ○ Animalia/Metazoa (multicellular, eukaryotic, move, ingest food and DO not photosynthesize) Phylum ○ Chordata (characteristics: notochord) Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 Important evolutionary feature - lived in the ocean and had a body axis, the notochord was the cellular rod that imparted stiffness to the body and when the muscles contract they could produce rapid movements because they had these Metazoans with a notochord Subphylum: ○ Vertebrata Chordates that have a spinal column and a bony skull Class ○ Mammalia Give birth to live young, suckle their young (production of milk), chew their food, warm blooded, have mammary glands, have hair Order ○ Primates Suborder ○ Haplorhini - tersiars, monkey, ape, Superfamily ○ Hominoidea- apes and humans Family ○ Hominidae- great apes and humans Tribe ○ Hominini- humans and their extinct relatives Informally referred to as: hominin Genus ○ Homo Trivial ○ Sapiens Species (always composed of two parts: genius and trivial) ○ Homo Sapiens There is only one species with this combination of taxonomic names Lecture 6 - Taxonomy and Phylogeny Systematics: 1. Taxonomy a. Naming and categorization of each species into its own unique part of Linnaean hierarchy 2. Phylogeny a. Pattern of evolutionary relationships between species b. How we figure out if species are closely or similarly related to each other c. The most common way of depicting evolutionary relationships is in the form of tree like diagrams which come in two forms d. Reconstructing and depicting the pattern of evolutionary relationships between species + other taxa Type 1 of Phylogeny - Phyletic Tree: Two Important Characteristics: Note: the vertical axis is time from past to present Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 1. Specific information about time 2. Explicit information about ancestry and descent recent C D B Time A past Type 2 of Phylogeny - Cladogram: 1. No direct information about time 2. No explicit information about ancestry and descent 3. Talks about recency of common ancestry a. Only information really depicted C D A B Each branching point = the last common ancestor of all the species that branch out above it (node) ○ Aka where C and D intersect = last common ancestor of C and D ○ Where B and D intersect = LCA of B, C and D ○ Where A and D intersect = LCA of A, B, C, D From this we can see ○ C and D are more closely related to each other than A and D Because C and D share a RECENT last common ancestor Can also use the pattern in the cladogram to define GROUPS of species / taxa ○ Look at all of the descendants of all of the last common ancestor This is called a CLADE Clade: Define: A group that includes ALL of the descendants of a single last common ancestor (also called = a monophyletic group) “Natural” groups ○ Groups that we can put together because they are unified by their pattern of common ancestors Referring to photo above Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ C + D = a clade ○ B + C + D = a clade (a different LCA) ○ A + B + C + D = a clade (an even different LCA) Taxonomic names should correspond to clades ○ Increasingly smaller and smaller ○ Not the only types of groups that could be recognized Paraphyletic Group: Define: A group that DOES NOT include all of the descendants of a single last common ancestor -- unnatural group NOT the same as a monophyletic group “Unnatural groups” Notes from Diagram below: Individuals closer to top of cladogram (aka monkey and humans) lived more recently than earlier ones Can use this to identify clades ○ Monkey, Humans = Primates ○ Horses, Monkey, Humans = Mammilia Paraphyletic Groups ○ Shark and Trout = taxonomic group of pices (fish) ○ Turtles and Lizards = Reptilia ○ Why? They do not represent all of the descendants of the last common ancestor Even if they look the same, they have very different evolutionary histories ○ Often approximate what we call GRADES (not clades) How do we know that this cladogram is real? ○ Morphology + Genetics Genetics is much more recent ○ Clue = things that look similar should be more closely related to each other ○ Only certain types of similarities ACTUALLY represent evolutionary relationships Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 Shark Trout Frog Turtle Lizard Bird Horse Monkey Human LCA of primate s LCA of mammals (hair, warm blooded, mammary glands, chew food, live birth) LCA of amniotes (have a water tight amnion -- LCA of can lay eggs) tetrapods LCA of (four weight vertebrates (have bearing limbs) a bony skull and vertebrae) Cladistics: Homology: Character shared by taxa that are inherited from a common ancestor (An inherited similarity) -- informative most of the time ○ Synaopomorphy Shared, derived character inherited from a last common ancestor ○ Symplesiomorphy Shared, but PRIMITIVE character inherited from a distant common ancestor What does this mean: ○ These are both types of homologies and show something about evolutionary relationships but its really only synapomorphy ○ Ex. if you look at horses, monkeys and humans relative to other vertebrates They have a number of homologies that they have inherited from the last common ancestor of mammals These mammals also have 4 weight bearing limbs ○ But this doesn’t say they are more closely related to each other than they are to frogs BECAUSE all of these groups have inherited 4 weight bearing limbs from a distant common ancestor It's only the homologies from the LCA that tells you if things are related to each other ○ Each one of these groups have Synapomorphies Homoplasy: Define: shared character (similarity) that was NOT inherited from a common ancestor Ex. whales ○ Look like fish ○ But this body shape = homoplasy It is a shared characteristic with fish but NOT from a common ancestor They just evolved this body shape in parallel ○ They're-evolved their fusiform body shape in parallel to what happened in fish Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 Lecture 7- Geological Record + Time + Evolution Geological Records: Mapping out layers of the earth and attempts to understand earth’s history ○ What is below = younger ○ Try to understand what was alive during that period Organizing geological records into categories of time Geological Chart:; Era Period Epoch Time (MYA) Events Holocene: Origin of “ Age of Mammals” Quaternary: agriculture, cities Evidence of Early humans 12,000 Years occur in tertiary period (7MYA) Pleistocene: Ice age, origin of Homo (our own genus) Human evolution begins at the end of the Miocene 2.6 Cenazoic Pliocene: Origin of australopiths 5.5 Tertiary: Miocene: Origin of apes- origin of hominins (end) 23 Oligocene: Earliest monkey like primates ( anthropoid primates) 34 Eocene: Radiation of primates 55 Paleocene: Origin of primates Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 65 "Age of Dinosaurs" Cretaceous Origin of Mammals Mesozoic Meteor hits at 65 MYA (A lot 145 of stuff dies) lit, sad boi Jurassic 201 Triassic 251 Origin of modern phyla Earliest vertebrates Earliest chordates Earliest representation of modern phyla Paleozoic -- Vertebrates evolved, fish evolved 542 Origin of life Precambrian 4.8 BYA Origin of World Boundary between Cretaceous and Tertiary = KT boundary Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 Points about Geology: Fossils: hard parts of organisms that turn into rocks within the Earth Three Types of Rocks: 1. Igneous Rock (Heat) a. Much of the depth of the earth = molten layer = hot liquid rock b. Form from being super heated c. Erupt and form mountains (volcanoes) and eventually erode from wind and water 2. Sedimentary Rocks (Slow pressure) a. Fine material that gets moved from one place and settled somewhere else b. These fine particles then become compressed to form hard layers c. = Fine sediments eroded off of the volcanoes d. Fine grained geological materials that get settled down and compressed, pressure causes them to consolidate e. Ex. sand stone 3. Metamorphic Rocks (Pressure and Heat) a. Tectonic events where parts of the Earth move around, causing sediments to buckle and fold on each other, generates enormous pressure + heat b. Folding with sediments in combination with high heat + high pressure c. Combination of heat and pressure Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 d. Were sedimentary rocks at one point and then morphed e. Ex. marble These are the three categorizations of rock. You will NOT find fossils in igneous rocks, but these become important for dating fossils. Metamorphic rocks are morphed and high heat so also NO fossils. Fossils found in sedimentary rocks. Lecture #8- Dating Methods Fossilization What is a fossil? ○ Fossil: a rock that is in the shape of a bone because there was some hard part of an organism was in place and minerals replace existing minerals inside of it so they then take on the shape of that organism A lot of the world’s fossils are marine fossils Some geological process causes sediments burying the fossil to go away and expose the fossil o Is a geological process that occurs to the tissues of the organs—tissues that are preserved are more commonly already kind of hard i.e. bones - Imagine you are a creature that lives in the ocean and dies: will come to rest on ocean floor: soft tissue disappears and hard tissue remains exposed on sediment: sediments floating through water will slowly cover up the fossil until it is completely layered: usually the shell also gets mineralized by the sediments surrounding the fossil: either quickly or slowly: structure will be converted to rock given the properties of what surrounds it: fossil may be exposed to the environment and could be destroyed by erosions or the elements - Process of Fossilization - 1. Organism dies, falls to the bottom of the ocean - 2. Overtime layers of sediment cover the organism’s remains - 3. Minerals and sediment around the organism leach into its shell or bones and replace the organic material. This is the process by which the organism literally becomes rock. - 4. High pressure pushes sediment around the shell and sedimentary rock forms. - *Fossilization is a geological process that happens to the tissues of organisms… often these tissues are already hard (shells, bones, etc.) Dating: Study the time sequence in which early organisms lived ○ Relative dating: are able to make the conclusion that “this fossil is older than that fossil”Date organisms by location in the ground ○ Absolute dating: putting an actual number the age Methods have been developed relatively recently Stratigraphy: Stratigraphy: studying a series of strata to determine the age of a fossil ○ Layers in the earth=strata Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ Determine age of fossils based on which strata they are found in ○ Relative dating method most of the time, can sometimes be used in absolute ○ Sediments on bottom of geological sequence must be older than the ones on top ○ Series of strata large scale—geological formation Each layer of strata= Member ○ Law of superposition Biostratigraphy: studying an area with an extensive geological formation that presumably is accumulated over long stretches of time, go into record and look at particular fossils for similar anatomical or morphological traits to establish relative ages of things o Relative dating method Absolute Dating Methods Radiometric Dating ○ All rely on basic principles relying on the phenomenon radiation Understand the rate at which radioactive isotope decays · Half-life: amount of time during which one half of the total number of radioactive isotopes will change into the daughter isotope o Radioactive isotopes useful to human evolution Types of Radiometric Dating: 1. Carbon dating a. Used on bone b. C14 = radio isotope of carbon, relatively short half life i. Because carbon is present in every organic tissue, it is very applicable - likely that the cabron won’t be completely leached out when all the minerals come in and fill it c. Found in organic tissues like bone and has a relatively short half life d. During the decaying process, parent and daughter isotope will be trapped within bone e. Useful dating to about 45,000-50,000 years ago 2. U/Th dating a. Used on speleothems (cave rock) forms when water drops down with mineral content and then over time buildup occurs (calcium-carbonate rocks) i. Looking at stalactite and stalagmite b. Uranium gets trapped inside rocks and is decaying—can detect daughter isotope (thorium) c. Caves formed by water dissolving limestone, Speleothems are caused by calcium carbonate leaching out of the walls and being deposited d. Only works inside caves e. Good for dating up to 400,000 years old and older than 100,000 years old 3. K/Ar and Ar/Ar dating a. Used on volcanic rock/ash b. Date basalts (lava flows) c. In magma there is radioactive potassium, when the volcano explodes, the radioactive isotopes fly out and you can measure content of radioactive isotopes. d. This is for "igneous rocks" e. Radioactive K has a longer half-life good for dating older than a million years Types of Cave Deposits: 1. Sinkholes – The sinkhole opens up to the surface and fossils tend to accumulate there Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 o Fossils accumulate there by carnivores or species falling into them and dying o Fig trees, with wide branches, often grow along the ring. Leopards carry prey up into the trees and then the bones drop into the hole o Sediments often consolidate at the bottom of the hole as breccias which is a mixture of water + dirt + and calcium carbonate that creates cement. § Excellent for preserving bones 2. Caves and Rock Shelters – At one point likely occupied by early hominins o Fossils accumulate there by hominins, lots of discarded bones or burials o Sediments often unconsolidated -- horizontal caves which are occupied, sediments often unconsildated Fluvial (river) and Lacustrine (lake) Sites: - Animals that die along the river ways are often buried by the sediments carried by the water. - Water suspends sediments in it and then the sediments dropped out of flow- can carry bones along with it and bury the bones and ancient fossils o Thus ancient waterways (even if they have been dried up) are likely good sites o Bones are protected - Olduvai Gorge = a famous lacustrine site o Exists as the African plate separates from the Indian plate and forms the “east African rift system” - formed by movement of tectonic plates -- river channels draining into center and then lakes form in the middle area, sediments accumulate as plates pull apart (older sediments lower down) o Lots of lakeshore deposits that look like a layer cake… as the plates move apart layers of rock are visible § The sediments on the lower aspect of this gorge are older Lecture #9- Climate Change: Questions to Answer about Climate Change: 1. How has the Earth’s climate changed over geological time? 2. How has climate change affected human evolution? 3. How do we reconstruct past environments? 4. What is responsible for climate change? a. Natural and non-natural sources How to reconstruct past environments: Foraminifera ○ Basically amebas (like seashells) ○ Single cell ameba lives inside of this thing ○ Live in ocean water ○ Unicellular organism that does not live very long ○ At very high frequency these things die and the shell falls down to the bottom of the ocean, and they collect Since these are calcium carbonate they consolidate and form a sediment which can be a major source of limestone Oxygen isotopes provide climate information ○ Oxygen in the calcium carbonate shell ○ Two Relevant Stable Isotopes of Carbon Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 O16 (light) Evaporates more easily O18 (heavy) Precipitates more easily ○ When the ocean water evaporates, it will preferentially incorporate the molecules with O16 (so more going to cloud is 16) The ○ During cold periods, more water trapped as continental ice sheets ○ These sheets form atmospheric water, which has more of the lighter isotope ○ So in cold periods, ocean water is O16 depleted and O18 enriched In cold periods, water gets trapped in glaciers So O16 is pulled out and there is more O18 ○ Some marine organisms incorporate oceanic oxygen into their shells, preserving the isotopic signal of ocean water, which in turns reflects global temperature ○ Point is: during cold and warm periods you get different proportions of ocean water with oxygen ○ Why is this important? During cold periods -- calcium carbonate in the Formaniferia will have more O18 than during warm periods During warm periods -- more O16 So you can drill the ocean floor, pull up these cores that have strata and as you move up the stratigraphic section you can extract the oxygen isotopes and observe a change in the concentration of O18 and see climate change over time Temperature Trends: General trend towards it becoming increasingly cooler ○ We are currently in a cold period that is heating up Fluctuations on a short term and have become more and more intense recently What Influences Climate: 1. Solar Radiation (Insolation) a. Amount and intensity b. Solar radiation that reaches the earth’s surface 2. Plate Tectonics a. Arrangements of continents of land masses on the earth’s surface b. Largely because tectonic plate effects can effect: c. Continental Drift and Climate i. South America used to be attached to Africa - disconnected ii. Was connected by a landbridge to Antarctica (which was also close to Australia) Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 iii.And this has profound effects on ocean circulation iv. When current hits the west side of South America, it was directed towards the equator and this resulted in cold water becoming more = much more moderate climate v. When South Africa was detached, then water was no longer directed upwards so it just circulates around Antarctica (nothing forcing the water towards the equator) -- water gets colder, colder and colder 1. Cooling the landmass in the South Pole = massive glaciers vi. Some drop off at the end of the Eocene has to do with the separation of these continents 1. GLOBAL EFFECT ON CLIMATE d. Tectonic events occur slowly i. Can go to a valley in Iceland and see the distance between North America and Europe ii. Happen very slowly to impact quick climatic fluctuations 3. Oceanic Circulation a. Gulf Stream - moderates temperatures in the East coast of north america i. It formed also as a result of tectonic events 4. Atmospheric Circulation 5. Orbital Sources of Climatic Variability a. Causes short term climatic events Milankovitch Cycles: 1. Eccentricity a. Orbit around the sun changes from circular to elliptical at 100 kyr intervals b. Average insolation is less during an elliptical orbit = less solar radiation (takes about 100,000 years for the whole cycle to take place) c. When orbit is elliptical it is getting less sunlight = colder d. Constant fluctuation from cold - warm - cold, or warm- cold- warm e. Milankovitch cycles: cyclical movement related to the earth’s orbit around the sun (these three in the list) 2. Tilt/Obliquity a. Axis of the earth varies from 22.1 to 24.5 degrees at 41,000 year intervals b. With higher tilt, polar regions receive more direct sunlight during summer, leading to more melt-off c. The Earth’s current tilt is 23.5 d. The tilt is responsible for the seasons e. If tilted towards the sun - Northern Hemispheres get more sunlight (more meltoff of ice) i. Higher tilt = earth’s polar regions get more sun f. Can rapidly change surface temperature as a result of insolation which happens more in the Northern hemisphere g. Global temperatures will decline as there is more tilt 3. Precession a. Due to the “wobble” in the axial tilt of the earth, and “drift” in the orientation of the earth’s orbit, the season in which the earth is closest to the sun varies at 23,000 year intervals i. Warm periods occur when the earth is closest to the sun during the northern hemisphere winter b. As the earth wobbles, the orientation of the earth around the sun and the spatial positioning of the earth’s orbit will change Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 c. So right now, Northern Hemisphere winters are mild d. Goes from cold to warm to cold again because of the precession of the equinoxes i. Ex. winter in the northern hemisphere is when we are CLOSER to the sun but titled away, so when we process change the relationship of season to our orbital movement ii. When we have half way processed the winter, the winter will occur when we are FURTHER from the sun, which will make for very intense winters e. Warm periods occur when the earth is closest to the sun during the Northern Hemisphere winter All of these things are impacting solar radiation simultaneously but on different time scales Fair correspond between variation in how the earth rotate around the sun and glaciation So these events are said to be affecting shorter term climate change events Different sources of climate change - combined to effect the environmental conditions under which early humans were living ○ Setting the selection pressures that led natural selection to lead humans to evolve Lecture 10- Paleoecology Bovids: Animals within tribes live within specific habitats ○ All of them can move within habitats but for the most part have preferences Bovids on African Landscape: 1. Wildebeest (open, dry habitats) a. Tribes: Antiolopini, Alcelaphini b. Dry = not a lot of rain / not humid, open = refer to the type of vegetation that is present i. Open habitat = lots of grass, not a lot of trees 2. Kudu (closed, dry habitats) a. Tribes: Tragelphini, Aepycerotini Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 b. Closed, dry habitats (bushes or trees that enclose sky above) c. They prefer to eat off of leaves and berries (that grow off of bushy trees) i. Trees close to the sky d. BUT STILL DRY 3. Waterbuck (closed, wet) a. Tribes: Reducini, Bovini b. Cows belong to this group c. Haitats with standing bodies of water or streams around them Can look at these bovids and who is represented more and less, and then depending on the amount of each species can tell us about the history of that area Can look at the fossils to understand what the habitat of an area was like Along all 3 axis seeing what percentage of each of the tribe If you can find fossils then can understand more about the vegetation Also if you find human fossils, then you can know about the conditions that these humans were living ○ (70% prefer dry habitats, 10% prefer open dry habitats, 20% prefer close wet habitats) Fossil assemblages includes humans Triangle Graphs: When humans were alive = more of the open + dry So most humans are living in habitats that are open and dry ○ What does this tell us about the habitats of our fossil human ancestors? ○ All based on where the bovids Graphs = same type of fossil humans, but a different part of Africa, prefer a different habitat Second graph ○ Might not have a habitat preference ○ Can maybe live in different habitats ○ Show adaptations of their ecology as well ○ Shows us that humans are not tied to one specific habitat Paleoecology Using Monkeys: Among the monkeys living in Africa, some live entirely in the trees or some live entirely on the ground 1. Colobus Monkey (Arboreal) a. Tribute: Colombini b. Tree based 2. Baboon (Ground Based) a. Papionini (more terrestrial) b. What style of locomotion tells us about what they were walking on (arboreal—know trees were around, etc.) Carbon Isotopes: Carbon 13 is not radioactive (does not decay) Most Carbon Dioxide has C12 isotope - some small amount has C13 This atmosphere CO2 goes into plant tissues ○ Why? Plants generate energy through photosynthesis Downloaded by Henry Murr ([email protected])  lOMoARcPSD|46591595 ○ Different plants have different biochemical pathways in which photosynthesis take place C3 - trees and bushes with broad leaves go through C3 photosynthesis ○ Produce fruits and berries ○ Have difficult incorporating C13 - harder for this to incoporate into tissues C4- grasses ○ Easier to incorporate C13 molecules ○ Grass eaters = more C13 The biochemical pathways differ in whether or not they can incorporate the C13 (heavier isotope) SO…. ○ Brows Plants = tissues have a lower proportion of C13 isotopes because it is HARDER for their photosynthetic pathway ○ Grass Plants = Higher amount of C13 isotopes Carbon Isotopes and Diet: Animals will come and eat the plant tissue and the carbon in the plant tissue will get incorporated in the tissues of the enamel So an animal who eats a lot of Brows (Broad leaves, berries and fruits) ○ Has low concentrated of C13 isotope Animals that eat grasses ○ Have higher concentration of C13 isotope (in bone and teeth -- which become fossils) Teeth can preserve a record of the C13 isotope that was present when the animal was alive Reconstructing past environments in the fossil record Downloaded by Henry Murr ([email protected])