Exam 1 Study Guide
Exam 1 Study Guide Bio 102
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This 23 page Study Guide was uploaded by Alyssa Shriver on Saturday February 6, 2016. The Study Guide belongs to Bio 102 at University of Tennessee - Knoxville taught by Dr. Jeremy Chandler in Spring 2016. Since its upload, it has received 304 views. For similar materials see Introduction to Biology in Biology at University of Tennessee - Knoxville.
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Exam 1 Study Guide Introduction to Biology Biology the study of life Life’s hierarchy of organization define the scope of biology o Life emerges through organization of various levels o With addition of each new level, novel properties emerge called emergent properties 7 properties of life o Order o Regulation o Growth and development o Energy processing o Response to the environment o Reproduction o Evolution Levels of hierarchy o Biologists explore life at levels ranging from the biosphere to the molecules that make up cells The Upper Tier o Is a global perspective of life Biosphere all the environments on Earth that support life Ecosystem all the organisms living in a particular area Community the array of organisms living in a particular ecosystem Population all the individuals of a species within a specific area The Middle Tier o The middle tier is characterized by the organism, an individual living thing, which is composed of Organ systems have specific functions; are composed of organs Organs provide specific functions for the organism Tissues made of groups of similar cells The Lower Tier o Life emerges at the level of the cell, the lower tier, which is composed of Molecules clusters of atoms Organelles membranebound structures with specific functions Cells living entities distinguished from their environment by a membrane What is Science? o A way of knowing based on inquiry o Systematic study of the natural world and natural phenomena o Science developed from our curiosity about ourselves and the world around us o The word science is derived from a Latin verb meaning “to know” How do scientists draw conclusions? o Reports in the news; Coffee causes cancer Coffee prevents some diseases Caffeine can be poisonous o Use best evidence available o Ask: Was the science performed properly? o Conclusion may be modified in the future o Science is a neverending process Science is a process: make an observation o Start with an interesting informal observation o Often unreliable untested o Anecdotal evidence Science is a process: formulate a question o Use observation to devise a question Science is a process: studying previous research o Read relevant literature o See current information on the subject of interest o Study peerreviewed scientific literature Validity in science o Hypothesis driven science scientific method and logic are applied to support or refute a hypothesis A hypothesis is a tentative explanation made on the basis of evidence collected The strength of hypothesis driven science relies on the empirical nature of its investigation A hypothesis can never be “proven” only supported Science is a process: studying previous research o Peer review: review of an article by experts before publication o Ensures that the authors have appropriately designed and interpreted their study o Weeds out sloppy research Culture of Science o Scientists build on what has been learned from earlier research They pay close attention to contemporary scientists working on the same problem o Cooperation and competition characterize the scientific culture Scientists check the conclusions of others by attempting to repeat experiments Scientists are generally skeptics o Science has two key features that distinguish it from other forms of inquiry. Science.. Depends on observations and measurements that others can verify and Requires that ideas (hypotheses) are testable by experiments that others can repeat Two approaches to Science o Discovery science describe natural phenomena based on observations. Patterns and correlations lead to formation of a hypothesis o Hypothesis driven science scientific method and logic are applied to support or refute a hypothesis Example of discovery science o In 1929, Alexander Fleming discovered that Penicillium mold generated a substance that kills bacteria o In 1941, Howard Florey and Ernst Chain purified penicillin The first commercial antibiotic to save human lives Example of Hypothesis driven science o Criteria for establishing a causative link between an infectious agent and a disease Dr. Barry Marshall o Drank to fulfill Koch’s postulate that it was causative organism of some stomach lesions and ulcers Science is a process: forming scientific hypotheses o A hypothesis is never proven o If false, it is rejected and no longer considered a possible answer to the original question o If the data support the hypothesis, it will be accepted until further testing and data show otherwise Science is a process: experimentation o Experimental group: experiences the experimental intervention or manipulation o Control group: experiences no experimental intervention of manipulation Basis for comparison Science is a process: drawing conclusions o Sample size (n) is important o It is the number of experimental subjects of the number of times an experiments are repeated o The larger the sample size, the more likely the results will have statistical significance o Statistical significance is a measure of confidence that the results obtained are “real” rather than due to random chance Selection and Adaption Methicillinresistant Staphylococcus aureus (MRSA) o Infectious bacterium o Difficult to treat with antibiotics o Kills 19,000 people in the United States each year Staphylococcus aureus o S.aureus (also known as “staph) o Some strains are harmless, other cause disease o Drugresistant strains exist Methicillinresistant Staphylococcus aureus (MRSA) o Developed resistance to antibiotic drugs o Adversely affects people with weakened immune system o Rocky Lannetti was already weakened by the flu Healthy 21yearold football player o The young, whose immune systems are still developing, and the elderly are at especially high risk o People who are already sick and fighting off other infections can be at high risk too Antiobiotics o Chemicals that either kill bacteria or slow their growth o Interfere with function of essential bacterial cell structures Bacteria reproduce through a process called binary fission. Binary fission is a form of asexual reproduction in which a single parent cell replicates its contents and then divides into two daughter cells. o Each daughter cell inherits all its DNA from the single parent cell Antibiotic resistance o Bacteria emerge that survive antibiotics o Acquire random mutations when DNA replicates during asexual reproduction o Binary fission: one parental cell into two daughter cells o Acquisition of new alleles in bacteria may result in antibiotic resistance Random mutation Gene transfer Asexually reproducing bacterial populations become genetically diverse by accumulating mutations and by picking up genes from organisms of the same or different species Mutation o Mutations made during DNA replication introduce new alleles into the populations Gene transfer o DNA can pass from one bacterial species to another. A nonstaph bacterium, for example, can pass genes to staph and introduce genes into the staph population that confer new traits, such as antibiotic resistance How populations evolve o A population is a group of organisms of the same species living together in the same geographic area o An entire population can change (evolve) when some traits are favored over others o For example, a drugresistant trait o Genetically diverse population o Varying allele frequency o Environment favors some alleles over others o Allele frequency changes over time (called evolution) o Fitness: organisms ability to survive and reproduce in a particular environment o Higher fitness= increased likelihood of alleles being passed to next generation o Genes that confer resistance to antibiotics increase an organism’s fitness o Organism’s alleles, or genotype, determine phenotype o Interplay between phenotype and environment determine frequency of traits in a population o If traits improve fitness, traits become more common in population Phenotype o From Greek phainein, meaning “to show”, and typos, meaning “type” o An organism’s observable characteristics or traits, such as its morphology, development, biochemical or physiological properties, phenology, behavior, and products of behavior Genotype o An individual’s collection of genes or alleles (variant form of a gene) inherited from a set of parental genes How populations evolve o Organism’s alleles, or genotype, determine phenotype o Interplay between phenotype and environment determine frequency of traits in a population o If traits improve fitness, traits become more common in population o Population evolves o These processes all occur as a result of selection o Populations, not individuals, evolve o Populations experience changes in allele frequencies over time Mechanism of Evolution o Selection Artificial selection selective breeding for desired traits in an organism Natural selection process where organisms better adapted to their environment produce more offspring and In artificial selection humans are in effect the “environment” that selects In 1929, Alexander Fleming discovered that Penicillium mold generated a substance that kills bacteria In 1941, Howard Florey and Ernst Chain purified penicillin o The first commercial antibiotic to save human lives Natural selection: differential survival and reproduction of individuals within a population in response to environmental pressure Advantageous traits become more common and population becomes better suited, or adapted, to environment Natural selection occurs in patterns o Directional selection: predominant phenotype shifts in a particular direction o Stabilizing selection: phenotype of populations settles near middle of range Ex. Human babies with very low birth weights do not survive as well as larger babies, and very large human babies are not easily delivered through the birth canal. Midrange babies are favored o Diversify selection: phenotype of population is at both extremes of range Three General Outcomes of Natural Selection o Directional selection: shifts the overall makeup of a population by selecting in favor of one extreme phenotype o Stabilizing selection: favors intermediate phenotypes, occurs in relatively stable environments, and is the most common o Diversifying selection: can lead to a balance between two or more contrasting phenotypic forms in a population Evolution of the unseen microbial world o Antibiotic resistance in bacteria is a growing problem that threatens everyone’s way of life Why sudden rise in antibiotic resistance? o Several factors have contributed Availability and use Profitability $$$ Evolution! Antibiotic resistance is a growing problem worldwide o Antibiotics are overused o Overprescribed; used in farm animal feed This exerts selective pressure for drugresistant strains o Streptococcus pneumonia o Acinetobacter baumanii Resistant to multiple drugs Stopping superbugs o Control resistance by changing practices that enable resistant strains to thrive o Wash hands, use hand sanitizers, stop misuse of antibiotics Dogs, The Beagle and Evolutionary Theory DNA the blueprint of the nature of life. The source of all diversity is the mutation of this blueprint code A cooling, drying climate over the last 40 million years turned North America from a warm and wooded place into the drier, open plains we know today. A new study shows how dogs evolved in response to those changes, demonstration that predators are sensitive to climate change because it alters the hunting opportunities in their habitat There are two prevailing theories on domestication of canines o Hunger/gatherer hypothesis Wolves were domesticated by hunter gatherers to use as tools for getting food o Agricultural revolution Wolves were progressively less scared of humans by acting as scavengers on waste from large scale agriculture Agricultural Revolution Hypothesis o A comparison of the full genomes of dogs and wolves revealed many changes that accrued as wild canines evolved into man’s best friend. Unsurprisingly, many of these differing regions affect the brain, and may explain the different temperaments of wolves and dogs. But the comparison, published today in Nature also pinpointed several regions that are involved in digestion, including genes that help to break down starch. This supports the idea that protodogs evolved new digestive adaptions to rely on the edible byproduct of the agricultural revolution Hunter Gatherer Hypothesis o Domestic dogs evolved from a group of wolves that came into contact with European huntergatherers between 18,800 and 32,100 years ago and may have since died out. This origin story comes from a new study that compares DNA from dozens of dogs and wolves, including 18 ancient fossils. The results, published today in Science, provide the clearest picture yet of where, when, and how vivid predators came to be man’s best friend. It really is sea change from the little bits of fragmentary DNA that have been reported in the past. Lamarck o One of the first evolutionary visions o As the fossil record kept developing he realized traits were not “fixed” o The first to propose change was through natural processes not natural theology o Coined the term “biology” Lamarckism o Hypothesis that traits acquired in one’s lifetime are passed on to offspring o Ex. If a giraffe strained its neck to eat leaves from higher branches, then overtime it would develop a longer neck. It would then pass this acquired trait on to its offspring, and they would be born with long necks Lamarck vs. Darwin o Darwin argued that complexity evolved simply as a result of life adapting to its local conditions from one generation to the next Contrasting views on Evolutionary forces o Lamarck Use and disuse Transmission of acquired characteristics Increasing complexity No extinction o Darwin Variation Inheritance Differential survival Extinction The Voyage of the Beagle, Evolution, and Speciation What’s the main reason for genetic diversity? o DNA Robert Fitzroy o Captain of the Beagle o Devout in religious beliefs Science of the day theologians o Debated with Darwin on the cruise Alexander von Humboldt o Geologists John Henslow o Darwin’s primary mentor at Cambridge University o Botanist Contributor’s to Darwin’s thinking included: o Charles Lyell Geologist, uniformitarianism The Earth is older than 6,000 years o George Cuvier First to say species go extinct o Thomas Malthus Struggle for existence Carrying capacity: J curve/ S curve o Jean Baptiste de Lamarck Evolution by acquired characteristics First evolution theory Giraffes get taller due to stretching Alfred Russel Wallace Independently Drew the Same Conclusions as Darwin o Papers from Wallace and Darwin were jointly presented to the Linnaean Society in 1858 The Second Voyage of the Beagle o 18311836 o Different species on different islands o Origin of species study Dust collected from the masthead on the Beagle o Some of the original samples were added to growth medium and cultivated viable organisms after over one hundred of years in storage Numerous fungi, bacteria were found There are the same organisms everywhere in the world, but once they get to a place, natural selection occurs and decides whether or not the organism thrives or doesn’t Bioluminescence is when oxygen in high concentrations can be harmful to microorganisms Darwin visited Brazil’s Atlantic rainforest before lodging began, and discovered the incredible diversity of its flora and fauna which differed greatly from Great Britain’s. Discomfort with Evolution o The upheaval surrounding evolution began with publication of On the Origin of Species and continues nearly 150 later o An early disparaging view of evolutionary theory and its creator An early disparaging view of evolutionary theory and its creator. Darwin’s voyage of the Beagle o In Argentina he found fossils of extinct mammals and discovered that they were closely related to species that no longer existed What percent of species are extinct? o 99% o Most of the extinctions are what we call “background extinctions” Background Extinction o The ongoing extinction of individual species due to environmental or ecological factors such as climate change, disease, loss of habitat, or competitive disadvantage in relation to other species. Background extinction occurs at a fairly steady rate over geological time and is the result of normal evolutionary processes, with only a limited number of species in an ecosystem being affected at any one time. Voyage to the Galapagos Islands o In the Galapagos Islands he discovered that animals like birds and turtles differed slightly from one island to another o The HMS Beagle stayed at the Galapagos Islands from September 15 through October 20, 1835 Galapagos Giant Tortoises o Galapagos in Spanish for saddle/tortoise o Although the Galapagos tortoises looked pretty much alike to Darwin, Nicholas Dawson, the Englishman in charge of Ecuador’s penal colony on Charles Island, told Darwin that he could tell which island any particular tortoise cam from, because there were slight differences from one island to the next. o Again, the significance of this was no evident to Darwin until after he had returned to England and thought about it Galapagos Island finches o Four species of finches found on the Galapagos Islands o Darwin did not realize they were all finches, but the English ornithologist John Gould told him they were; Gould identified a total of 13 different species among Darwin’s specimens o The Galapagos finches have been extensively studied since Darwin’s time, and their evolution (back and forth) recorded Galapagos Marine Iguanas o Their diet consists of mostly seaweed, which is unusual for land animals such as the iguana o Their feet are webbed so they can swim in the sea o On land they are sluggish in movements but swim with ease and quickness in the sea o They regulate their temperature by either laying flat on the lava to catch the heat or perching up to catch the breeze o The brightly colored lizards are colored that way from eating plentiful seaweed and this attracts female lizards because the male is healthy therefore the offspring with be healthy o Colors due from algal blooms in summer and feeding on those blooms El Nino Effect on marine iguanas? o Dries up all the algal, therefore all the iguanas starve and more than 99% of the iguanas die off The Galapagos Islands o “Both in space and time, we seem to be brought somewhat near to that great fact that mystery of mysteries the first appearance of new beings on this Earth” o Darwin’s notebooks on the voyage of the Beagle totaled to 1,383 pages on geology, and 368 pages on zoology What comes to mind when you see the word “ecosystem”? o Life o Animals o Plants o Environment o Habitat o Other Urban Evolution o Studying evolution in Manhattan Population genetics o Study of the genetic makeup if populations and how genetic composition changes o Gene pool; total collection of alleles in a population o Identify allele frequency o If the gene pol changes over the course of generations, then evolution has occurred o Changes in allele frequency over time o Population evolves o Good, bad, or neutral consequences result in the population becoming more adapted to its environmentnatural selection results in a population adapting What causes changes in allele frequency? o Natural Selection Population is better adapted o Nonadaptive Evolution Caused by mutation, genetic drift, and gene flow Nonadaptive Evolution o Genetic Drift Changes in allele frequencies between generations that occurs purely by chance Subset of population reproduces Subset of alleles represented in next generation Decreases genetic diversity of a population Evidence for Genetic Drift o Researchers collected tail DNA from 312 mice at 15 locations in NYC. One they analyzed each mouse’s DNA, the researchers wanted to get a sense of how related the populations were. They assigned mice with similar genotypes particular colors and sorted all the mice by location. They found that mice within a population shared more alleles with one another than they did with mice from other populations. Evolution of Populations, Speciation, and Evidence for Evolution Today in science o Sex wars: ant queens take sperm from males of other species Rock pocket mice o Valley of Fires Recreation Area, NM o The mice coat camouflages them from predators MC1R Gene o Lighter mice have two copies of the light allele o Darker mice have one copy or two copies of the black allele Variation and time o How often does a black coat mutation arise? Depends on Mutation rate Reproduction rate Population size Mutation Rate 2 per 10^9 sites in DNA Possible mutation sites in fur gene= 10 Number of copies of fur genes= 2 1 in 25 million offspring have a black coat mutation o Now factor in rate of reproduction: per year >5 offspring o Population size >5,000 females o Total offspring per year= 25,000 o Odd of black mutation: 1 in 25 million o 1 black mouse every 2500 years Is 1 black mouse per 1000 years a high mutation rate? o No Selection and time o How long would it take for every mouse to be black? Depends on S is the selection coefficient S is a relative measure of fitness S is successful at reproducing Is a black mouse produced 101 survivors out of 100 light colored mouse Nonadaptive Evolution o Genetic Drift Change in allele frequencies between generations that occur purely by chance Subset of population reproduces Subset of alleles represented in next generation Decreases genetic diversity of a population Gene Flow o Movement of alleles from one population to another o Urbanization can prevent gene flow, can lead to inbreeding Why is genetic diversity important? o Diverse gene pool gives a population more flexibility to survive in a changing environment o The more genetically diverse a population, the more ways it has to adapt Reintroducing genetic diversity o Must bring in new alleles o Mutation o Gene flow Inbreeding o Mating between closely related individuals o Does not change the allele frequency within a population o Increases the proportion of homozygous individuals to heterozygotes o Ex. Charles Darwin’s marriage Inbreeding Depression o Closely related individuals are more likely to share the same alleles o Negative reproductive consequences for a population o Associated with high frequency of homozygous individuals possessing harmful recessive alleles The Florida Panther o In 1990’s around 30 or less members of the population remaining o Many of the remaining individuals were sick and a multitude of defects ranging from crooked tails to heart conditions in addition to poor sperm quality o In 1995 8 female pumas from Texas were brought in to bolster the population Adaptive and Nonadaptive Mechanisms of Evolution o Natural Selection Individuals with favorable alleles reproduce preferentially, increasing the frequency of these alleles Adaptive Usually genetic diversity decreases—unfavorable alleles may be eliminated from the population o Mutation New alleles are created randomly Nonadaptive Usually genetic diversity increases—new alleles are introduced into the population o Genetic Drift Allele frequencies change due to chance events Nonadaptive Genetic diversity usually decreases—alleles may be eliminated from the population o Gene Flow Alleles move from one population to another Nonadaptive Genetic diversity increases—new alleles are added to the population Homozygous vs. heterozygous review o Tt heterozygous (hybrid) o BB homozygous dominant o Bb homozygous recessive o TT homozygous dominant o Tt homozygous recessive o Bb heterozygous (hybrid) HardyWeinberg equilibrium o In a nonevolving population, allele and genotype frequencies do not change over time o Use to identify genes that have changed because of evolutionary mechanisms o Baseline to judge if a population is evolving o HardyWeinberg equation P2+2pq+q2=1 P2 is the frequency of homozygous dominant 2pq is the frequency of heterozygotes q2 is the frequency of homozygous recessives o Five necessary conditions No mutation introducing new alleles into the population No natural selection favoring some alleles over others An infinitely large population size (and, therefore, no genetic drift) No influx of alleles from neighboring populations (i.e. no gene flow) Random mating of individuals What is a species? o Biological species concept A population of individuals whose members can interbreed and produce fertile offspring Different species cannot mate because they are reproductively isolated Speciation and “sexual islands”, Evidence for Evolution What is a species? o Biological species concept Species is a Latin word meaning “kind” or “appearance” The biological species concept defines a species as “A group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring What is bacteria? o Contains cell wall, plasma membrane, prokaryotic chromosome Duplication of chromosome and separation of copies Continued elongation of the cell and movement of copies Division into two daughter cells o The biological species concept cannot be applied in all situations, including Asexual organisms Reproductive Isolation o Ecological Isolation Different environments. The Artic fox and the desert fox live in such different places, they never encounter each other o Temporal Isolation Mating behavior or fertility at different times. The leopard frog mates in early spring and the bullfrog mates in early summer o Behavioral Isolation Different mating activities. The prairie chicken is not attracted to the mating display of the ring necked pheasant o Mechanical Isolation Mating organs are incompatible. Plants pollinated by the hummingbird do not receive pollen from plants pollinated by the black bee o Gametic Isolation Gametes cannot unite. The gametes from a dog and a cat cannot unite to form a zygote o Hybrid Inviability Gametes unite but viable offspring cannot form. The goat and sheep can mate, but the zygote formed does not survive o Hybrid Infertility Viable hybrid offspring cannot reproduce. Zebras and horses are different species because their hybrid offspring, zebroids, cannot produce offspring of their own Sexual Selection o Inherited traits are more likely to foster offspring or produce more offspring o Often leads to sexual dimorphism differences in appearance between males and females of the same species, such as in color, shape, size, and structure, that are caused by the inheritance Reproductive Barriers between Species o Prezygotic barriers include Temporal isolation Habitat isolation Behavioral isolation Mechanical isolation, and Gametic isolation o Prezygotic barriers operate if Interspecies mating occurs and Hybrid zygotes form o Postzygotic barriers include Reduced hybrid viability, Reduced hybrid fertility, and Hybrid breakdown Mechanisms of Speciation o A key event in the potential origin of a species occurs when a population is somehow cut off from other populations of the parent species o Species can form by Allopatric speciation, due to geographic isolation, or Sympatric speciation, without geographic isolation Evidence of Evolution o Evolution leaves observable signs o Five of the many lines of evidence in support of evolution The fossil record Biogeography Comparative anatomy Comparative embryology, and Molecular biology Georges Cuvier o 17691832 Naturalist that specialized in the anatomy of animals. One of the first paleontologists o One of the first to realize that fossilized remains were evidence of extinct organisms. (religiously troubling theory) o “Father of Paleontology” o Theory of cataclysms The Fossil Record o Paleontologists: scientists who study ancient life by means of the fossil record o Fossil: the preserved remains or impressions of onceliving organisms o Fossil record: an assemblage of fossils arranged in order of age, which provides evidence of changes in species over time Not every organism that dies forms a fossil. Organisms are more likely to fossilize if they have bony skeletons or hard shells. In addition, the organism must be covered quickly upon death or create an imprint in special types of sediment. Therefore, the fossil record is not a complete record of past life, but it has supplied an impressive body of evidence for evolution Fossil Process o Organism dies Organism is preserved by rapid freezing, desiccation, or burial in amber. In these cases, organisms are preserved largely in their original state. Organism is preserved by rapid burial in sediment layers. Quick burial in sediment (ex. By mudslide or volcanic eruption) protects the body from rapid decay Organism is fossilized by mineralization. Hard parts of the body such as teeth and bones do not decay rapidly. Over time minerals in water are deposited in the spaces within bones or replace the bone as it breaks down. The result is a mineralized fossil. Organism is fossilized by imprint or mold. The soft mud in which a dead organism is buried hardens into rock around the organism. Over time the organism decays, leaving a space in the surrounding rock. The space has the same shape as the exterior. Reading the fossil record o Discovered fossil remains of Tiktaalik o Important part of evolution of vertebrate Animals with bony or cartilaginous backbones o Tiktaalik Transition between fish and landdwelling animals o Descent with modification (aka evolution) All living things are related Different species emerged over time due to natural selection o Not all organisms are preserved o The fossil record is not a complete record of past life o Extensive enough to show arc of life o Shows an ordered succession of evolution o See changes over time in family of organisms The fossil record of horses supports the theory of descent with modification. Forelimb fossils are similar to one another, but show changes over time from the earliest horse ancestors to modernday horses as species diverged from a common ancestor. In the fossil record we can observe over time a reduction in toe number, as the central toe became dominant, allowing horses to move more rapidly in new prairielike environments. Reading the fossil record o Shows intermediate fossils like Tiktaalik o 375380 million years ago o No landdwelling vertebrates How are fossils dated? o Relative dating Determine age of the fossil from its position relative to layers of rocks or fossils of known age o Radiometric dating Use radioactive isotopes as a measure of age Evolution of life on land o 400350 million years ago o Most land submerged under water Age of fishes o Some plants and invertebrates on land animal without a backbone o Over time land became more available Evidence for Evolution Cont. & Life on Earth Evolution of life on land o 400350 million years ago o Most land submerged under water Age of fish o Some plants and invertebrates on land Animal without a backbone o Over time land because more available Evolution of life on land o Living on the land requires Sturdier structure Prevention of water loss A different way to take in oxygen Limbs o Tetrapods Vertebrate with four true limbs Jointed, bony appendages with digits o Tiktaalik Possess many features of a lobefinned fish Also had a jointed elbow, wrist, and fingerlike bones Common Ancestry o All tetrapods share the same forelimb bones arranged in the same order o Homology: Similarity due to common ancestry o Homologous structures: are those that are similar because they are inherited from the same ancestor The number, order, and underlying structure of the forelimb bones are similar in all the groups illustrated below. The differences in the relative width, length, and strength of each bone contribute to the specialized function of each forelimb. The anatomical homology is strong evidence that these organisms all have a common ancestor at some time in the distant past. The variations in bone shape and function reflect evolutionary Divergent Evolution o Accumulation of differences in populations which can lead to the formation of a new species o Vestigial Structures a structure which has lost much of its ancestral function In human examples: appendix, coccyx, goose bumps How old is Earth? o Rocks collected from Apollo missions o Estimate age of Earth: 4.5 billion years old o Radiometric dating Amount of radioactivity present in a rock is used as a geologic clock o Radioactive isotopes Unstable form of an element that decays into another element by emitting energetic particles (radiation) o The time it takes for half the isotopes in a sample to break down is called its halflife o Used to determine the age of the materials in which they’re found o Some rock types, like those produced during volcanic eruptions, contain radioactive minerals like zircon that can be used to determine the age of the rock. Because the isotope238 decays to lead at a constant rate, the age of rock layers containing these minerals can be calculated by measuring the ratio of uranium238 to lead206 in the mineral sample. When and how did life begin? o 3.5 billion years ago o Left no discernible evidence o Harold Urey and Stanley Miller hypothesized that they could synthesize organic molecules by replicating the chemical environment of early Earth o Their experiment yielded new organic molecules, including amino acids o Showed that it was possible to create molecules of life from inorganic materials What was life like million of years ago? o The geologic timeline shows that Earth’s geography and climate have gone through dramatic changes o Oldest known fossils date 3.5 billion years ago o Atmosphere lacked oxygen o Unicellular prokaryotes that used other gases as a fuel source o Emergence of unicellular photosynthetic organisms 3.0 to 2.5 billion years ago o Oxygen began to accumulate in the atmosphere o First multicellular eukaryotic organisms: green algae 1.2 billion years ago o Marine invertebrates arrived 600 million years ago o Diverse animal world in Cambrian explosion o Land colonized by primitive plants 450 million years ago o Periodic mass extinctions punctuate the fossil record Elimination of all individuals in a species o Survivors spread and diversified o Colonized newly open habitats o Adaptive radiation o Pattern of extinctions followed by adaptive radiation is seen in the fossil record o Punctuated equilibrium: periodic bursts of species change as a result of sudden environmental change Why are there no penguins at the North Pole, and no polar bears at the South Pole? o Distribution of organisms reflects their evolutionary history o Biogeography: study of how organisms are distributed in geographical space o Plate tectonics Movement of Earth’s upper mantle and crust Influences the geographical distribution of landmasses and organisms o Earliest penguin fossils were found near New Zealand and date from a time when what is now New Zealand was physically close to Antarctica. Penguins were able to distribute widely in the southern hemisphere with the movement of the tectonic plates. Are creatures that look alike always closely related? o Common ancestry is not the only reason that two species might appear similar o Convergent evolution Organisms that are not closely related evolve similar adaptations as a result of independent episodes of natural selection For example, cold water fish How many species are there on Earth, and how do scientists keep track of them? o Estimated 5 million to 30 million total number of species on Earth o 1.5 million or so have been formally described Taxonomy o How we classify different species o Systematically identifying, naming, and classifying organisms on the basis of shared traits o Organisms are classified into groups that are increasingly exclusive. In the broadest category (animal kingdom), all animals are included. Closely related organisms are grouped based on morphological, nutritional, and genetic characteristics. There are far fewer organisms in an order than in a phylum. Molecular methods o Based on molecular (DNA) and morphology (phenotype) Phylogeny o The evolutionary history of a group of organisms o Represented by a diagram called a phylogenetic tree Branch lengths can represent, genetic differences, time, or physical character changes o Evolutionary history, or phylogeny, is represented visually by a phylogenetic tree. Trees have a common structure, with a root, nodes, and branch points. To determine evolutionary relationships among living or extinct organisms, consider the most recent common ancestors. o Branch: process of natural selection leading to new species or groups of species o Root: this is the common ancestor of all organisms on the tree o Node: this is the last common ancestor of the organisms above this point in the tree How many branches does the tree of life have? o Since each living species sits on its own branch in a phylogenetic tree, the complete tree of life has as many branches as there are species in the world In 1977, Carl Woese was studying recently discovered prokaryotes in hot springs Analysis of the DNA revealed that these prokaryotes were a distinct form of life o He called them Archaea Carl Woese’s discovery replaced the five kingdoms with the three domains: o Bacteria Green nonsulfur bacteria Grampositive bacteria Proteobacteria Cyanbacteria Spirochetes Thermotogales o Archaea Creanarchaeota Hyperthermophiles Sulfur oxidizers Halophiles Euryarchaeota Methanogens o Eukarya Microsporidia Diplomonads Trichomonads Flagellates Ciliates Plants Fungi Animals Slime molds Entamebas How many branches does the tree of life have? o The highest category in modern classification is the domain The modern classification system today: o Domain Eurkarya o Kingdom Animalia o Phylum Chordate o Class Mammalia o Order Carnivore o Family Canidae o Genus Vulpes o Species Vulpes o Humans are a member of the Eukarya
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