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Evolution and Classification Unit 9 How could life have begun on a lifeless Earth? • Early atmosphere was similar to gases given off by volcanoes carbon monoxide, carbon dioxide, and nitrogen • Notice: NO OXYGEN How could life have begun on a lifeless Earth? • Aleksandr Oparin = Russian biochemist; developed a theory that the chemicals in the early atmosphere and energy from lightning could have formed simple organic compounds • Earth was mostly covered by water life probably began in the oceans, a “primordial soup” Miller and Urey Experiment • Conducted in 1952 by Stanley Miller and Harold Urey • They took a vial of water and gases similar to those of the early atmosphere and shocked it with electricity (like lightning) • They discovered amino acids had formed • Since proteins are a major building block of cells, they concluded that this could be how life began • http://www.youtube.com/watch?v=79o6xz MfzKg Biogenesis vs Abiogenesis • Abiogenesis = the idea that life can come from non-living things, also known as spontaneous generation • Biogenesis = the idea that life must come from other life Redi Experiment • Performed by Francesco Redi in 1668 • At the time people believed in spontaneous generation • Fish came from mud in rivers • Maggots came from rotting meat • Redi decided to prove that life must come from other life Redi Experiment Open Jar Sealed jar Cheesecloth jar Open to the air? Yes No Yes Flies able to get in? Yes No No Rotting meat? Yes Yes Yes Maggots present? Yes No No Conclusion: Maggots come from flies, not from meat. Therefore, life must come from other life spontaneous generation is wrong But wait, there’s more… • After the discovery of the microscope and microscopic organisms, people wondered “Is biogenesis true at all levels of life?” • Louis Pasteur (a French microbiologist) performed an experiment that proved that it was Pasteur’s Experiment • Pasteur made a “broth” of nutrients that he boiled until he was sure nothing was alive in there Pasteur’s Experiment • The flask was specially designed to be open to the air, but not let any dust touch the now sterile broth Pasteur’s Experiment • Pasteur saw that nothing grew, so he repeated the experiment, but now he snapped off the neck of the flask and exposed the broth to dust • The broth was soon filled with microorganisms • Therefore, spontaneous generation was proven wrong again So where do cells come from? • Miller and Urey had proven that amino acids could form on their own, but what about cells? • The first cells were probably anaerobic, prokaryotic, heterotrophic, and unicellular • Anaerobic = no oxygen in atmosphere • Prokaryotic = no nucleus (developed later) • Heterotrophic = don’t make own food too hard • Unicellular = small and simple How did we get oxygen? • Over time, photosynthetic cells developed • RECALL: Photosynthesis produces glucose and oxygen • All of this oxygen resulted in the ozone layer and allowed aerobic organisms to develop Endosymbiont Hypothesis • Developed by Lynn Margulis in 1966 • States that eukaryotic cells came from prokaryotic cells that lived together in symbiosis • Mitochondria and chloroplasts have their own genetic material and reproduce on their own probably bacteria absorbed by the cell • Endosymbiosis = when one organism absorbs another and they live and work together Ok, so now we have cells… Where did all this life come from? • Charles Darwin (1809-1882) is credited with creating the theory of evolution, although his ideas were based on the ideas of many others • Developed his ideas as he sailed on the HMS Beagle, especially as he sailed around the Galapagos Islands Theory of Evolution • Darwin originally decided to keep his ideas to himself • In 1859, Alfred Russel Wallace discovered the same things as Darwin and was going to publish his ideas • This made Darwin decide to go ahead and publish his findings Theory of Evolution • 1. There is a variety of traits in a population. • 2. There is competition in the population for limited resources. • 3. Natural selection favors the individuals with a certain trait. This doesn’t mean that everyone else dies, but they won’t have as many offspring. • 4. Over time, this trait will be more frequent in the population, because nature has selected that trait. Theory of Evolution • What makes a trait useful? • That depends on the circumstances of the population Adaptations • An adaptation is any heritable trait that suits an organism to its natural function in its environment (its niche) • Three major types: • Structural adaptations = physical traits like defensive structures, camouflage and mimicry (looking like a more dangerous animal) • Behavioral adaptations = behaviors (learned or instincts) that help an organism survive, such as herding, schooling, growling, etc. • Physiological adaptations = physical/chemical traits such as sight, enzymes, and hemoglobin Evidence for Evolution • Fossils = any evidence of life, including imprints and remains of organisms • The fossil record is incomplete very few organisms become fossils • However, the fossil record indicates that life began in the sea and moved to land Evidence for Evolution • How can we tell how old a fossil is? • Relative dating = where the fossil is compared to other fossils; fossils near the top are more recent than those below not very accurate • Radioactive dating = uses the rates of decay of various radioactive isotopes to determine when the organism was fossilized much more accurate Evidence for Evolution • Biochemical similarities = similarities in DNA, amino acid sequences, proteins, etc. • The more similarities there are, the more closely related two species will be Evidence for Evolution • Shared anatomical structures = physical similarities between species • Similar bone structures (even if the function is different) indicate a common ancestor = homologous structures • However, structures that perform the same function but have different anatomical structures DO NOT come from the same ancestor evolved separately = analogous structures Evidence for Evolution • Vestigial structures = structures that are not functional in an organism, but indicate a link to a previous ancestor • Examples: Human appendix, human tail bones, foot bones in whales and dolphins, etc. Evidence for Evolution • Embryology = comparing how organisms look at different stages of embryonic development and looking for similarities So if there is all this evidence, why is evolution just a theory? • In science, a law tends to describe a relationship in nature, a theory explains why that relationship exists. • If a better explanation is discovered, a theory can be discarded or replaced • Right now, the theory of evolution is the best scientific explanation for life When did different organisms evolve? • Life began in the ocean unicellular (simple protists, algae, etc.) • Eventually, life got complicated (multicellular plants, invertebrate animals like jelly fish, etc.) How did animals evolve? • From jellyfish, animals developed backbones fish • Some animals grew legs and lungs and moved out of the water amphibians and insects • Amphibians still need to return to water to lay their eggs How did animals evolve? • Eventually, harder shells and dry skins or feathers develop reptiles and birds • Mammals then evolved live birth, produce milk, hair follicles • Some mammals returned to the ocean whales, dolphins, manatees, etc. How did plants evolve? • Aquatic plants moved onto the land bryophytes = seedless, non-vascular (they can’t move water through a stem) • Mosses, liverworts, hornworts • Must stay low to the ground for water osmosis • Need water to reproduce How did plants evolve? • Seedless vascular plants developed next • Now capable of growing taller can move water against gravity • Xylem = carries water up from roots to rest of plant • Phloem = transports nutrients and carbohydrates (food) to rest of plant • Reproduce using spores instead of seeds • Ferns, club mosses, horsetails How did plants evolve? • Plants then developed seeds Gymnosperms (“naked seed”) • Have vascular tissue and seeds, but no flowers • Not as dependent on water = wider variety of habitats • Palm trees, conifers, ginkgoes, gnetophytes How did plants evolve? • Finally, flowers developed Angiosperms (“enclosed seed”) • Roses, oak trees, daisies, maple trees, etc. • Two kinds: • Monocots = one seed leaf, parallel veins, floral parts often in multiples of 3, vascular bundles scattered throughout stem, fibrous roots • Dicots = two seed leaves, branched veins, floral parts often in multiples of 4 or 5, vascular bundles arranged in a ring, taproot Types of Plants: Vascular Tissue? (able to move water?) Seeds? Flowers? Bryophytes No No No Seedless vascular plants Yes No No Gymnosperms Yes Yes No Angiosperms Yes Yes Yes How does evolution work? • Jean-Baptiste Lamarck = (1744-1829) the man who got it wrong • Thought that acquired traits could be passed from parent to offspring now we know that is not true How does evolution work? • Individuals don’t evolve, populations do • Populations are the smallest unit of evolution • Evolution occurs when the gene pool (all of the genes of a population) changes • A change in genotype may lead to a change in phenotype • Evolution acts on the phenotype How does evolution work? • Mutations = random changes in DNA; may lead to a new phenotype • If the mutation is favorable, the organism will have an advantage to survive and reproduce • The environment also plays a role environmental changes are nature’s “selection forces” • Example: Lots of snow makes a mutation for white fur favorable Types of Selection: • Stabilizing selection = favors the “average” or “middle” phenotype • Directional selection = favors ONE of the extreme ends of the phenotype spectrum • Disruptive selection = favors BOTH of the extreme ends of the phenotype spectrum, but not the middle Co-evolution • The evolutionary effect of one species on another • Example: Hummingbirds with longer beaks are better able to collect nectar from long, narrow flowers. Hummingbirds prefer brighter colored flowers. Therefore, there is an increase in frequency for long-beaked hummingbirds and bright flowers. Geographic Isolation • Speciation = the formation of a new species • Geographic isolation = two populations of a species are physically separated from each other and unable to interbreed eventually become new species • Therefore, geographic isolation leads to reproductive isolation How quickly does evolution happen? • Two different rates: • Gradualism = evolution that takes a long time, happens gradually and slowly • Punctuated equilibrium = evolution that happens over a relatively short period of time, happens in rapid bursts after long periods of stability, probably due to environmental change Does evolution happen today? • YES! • As long as variation, overproduction, competition, natural selection, and mutations occur, evolution will happen • Since most evolution takes so long to occur, it can be hard to see in a lab • However, there are some forms of evolution we can observe… Does evolution happen today? • Resistance evolution = insects become resistant to pesticides, bacteria become resistant to antibiotics • Artificial selection = humans select desirable traits and breed animals who have those traits (ex. Different dog breeds) How do we organize organisms? • Aristotle = Ancient Greek philosopher who developed the first classification system • Two main categories = plants and animals OR Carl Linnaeus – Father of Classification • Further divided plants and animals into smaller and smaller groups • Used Latin because it was a “dead language” and would not change Linnaeus Classification • Linnaeus first grouped related organisms into a genus • Example: All dog-like creatures are grouped into the genus Canis • Every different type of organism within the group gets its own name a species • Example: A domesticated dog is grouped into the species familiaris, while the wolf is grouped into the species lupus • Genus is always capitalized, species is not • Italicized or underlined Canis familiaris or Canis lupus Scientific names • Binomial nomenclature = two names (genus + species) • Why use scientific names? • Avoid confusion due to common names same name for an organism all over the world • Question: What is the difference between a cougar, mountain lion, panther, puma, and a catamount? What about a cottonmouth and a water moccasin? • Answer: In North America, they are the same animal! Modern Classification • Even after the microbial world was discovered, the 2 kingdom system continued to be used • Science can be very slow to change • In 1969, Robert Whittaker expanded classification to include 5 kindoms: Animals, Plants, Fungi, Protists, and Monera Modern Classification • Taxonomy = the science of classification • Today, we have seven levels: Kingdom Phylum Class Order Family Genus Species King Phillip Came Over For Great Sex Modern Classification • A kingdom is a more general, broad group and will therefore have more organisms • We now have 6 kingdoms • A species is much more specific, and will therefore have less organisms only one • A species is defined as a group of organisms which can interbreed and produce fertile offspring But wait… There’s more! • We now have 3 domains that we organize the 6 kingdoms into: • Bacteria • Archaea • Eukarya Organizing Life… • So what happens if you come across an organism, and you don’t know what it is? • There are several tools you can use, but one of the easiest is the dichotomous key Dichotomous Key • Uses a series of paired statements about the physical appearance of the organism • Only useful if the organism has already been classified and given a scientific name • 1. Always start at statement 1 (or the beginning point) • 2. Decide which path best describes the organism (Statement A or Statement B) • 3. Follow that path to find the next choice (Go to …) • 4. When you can go no further, you will find the name! Dichotomous Key But what if it is an organism that hasn’t been classified yet? • Scientists use many methods to classify new organisms: • Morphology = classifying organisms based on their physical characteristics usually enough to get the correct domain and kingdom • Example: Having a nucleus will place the organism in the domain Eukarya • DNA and biochemical analysis = scientists will look for genetic similarities to other classified organisms or other less visible (but still testable) characteristics • Example: In a Gram-stain, prokarya will stain pink (gram-negative) while archaea will stain purple (gram-positive) But what if it is an organism that hasn’t been classified yet? • Scientists can compare embryology (how organisms look during early stages of development) • Evolutionary phylogeny = describes relationships between organisms based on shared traits, which can be physical (does the animal have a jaw?) or genetic (shared genes) • Phylogenetic tree = tool used to show phylogenetic relationships Don’t get the wrong idea… • Humans are not at the top of the “evolutionary ladder” • We are just another branch on the tree! 1) German Shepherd, Great Dane, parrot, Irish setter, canary, husky, robin, pigeon Title_________________ Title____________________ _________________________ _________________________ ____________________________ ____________________________ _________________________ _________________________ ____________________________ ____________________________ 2) apples, peas, orange, banana, carrot, lettuce, turnip, pear, grape, potato Title_________________ Title_________________ _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ _____________________ The Six Kingdoms: Bacteria • Prokaryotic, unicellular • Food: Can be autotrophic or heterotrophic • Cellular energy: Can be aerobic or anaerobic respiration • Reproduction: Asexual • Can be beneficial (making food like yogurt) or harmful (causing disease) to humans The Six Kingdoms: Archaea • Prokaryotic, unicellular • Food: Can be heterotrophic or autotrophic • Cellular energy: Can be aerobic or anaerobic respiration • Reproduction: Asexual • EXTREME bacteria live in areas with very high temperatures, salinity, guts of animals, etc. The Six Kingdoms: Protista • Eukaryotic, can be unicellular or multicelluar • Food: Can be autotrophic or heterotrophic • Cellular energy: Aerobic respiration • Reproduction: Asexual • Some protists (like algae) form the base of food webs and produce most of our oxygen The Six Kingdoms: Plantae • Eukaryotic, multicellular • Food: Autotrophic • Cellular energy: Aerobic respiration • Reproduction: Sexual and asexual • Very important form the base of many food webs, used for many products (lumber, food, cloth, medicine, etc.) The Six Kingdoms: Fungi • Eukaryotic, can be multicellular or unicellular • Food: Heterotrophic • Cellular energy: Aerobic or anaerobic respiration • Reproduction: Asexual or sexual • Act as decomposers (break down dead stuff) and can be used to make alcohol and food The Six Kingdoms: Animalia • Eukaryotic, multicellular • Food: Heterotrophic • Cellular energy: Aerobic (occasionally anaerobic) • Reproduction: Sexual • Important consumers in food webs, humans are animals