Transcript Evolution
Evolution-change over time The Origin Of Life Spontaneous generation vs biogenesis A FIRST LIFE HYPOTHESIS • • • • • Conditions one Earth 4.5 billion Years Ago Amino acids and RNA Protobionts- Coacervates and Pre-cells Heterotroph Hypothesis Cell symbiosis Miller & Urey’s experiment • Conditions to simulate a primitive earth• lightning, UV radiation, volcanic activity, and heating and cooling • methane, ammonia, carbon dioxide, and water • Boiled and condensed • electric charge ***A mixture of Amino Acids Resulted*** First Life Processes • 3.5- 4 billion years ago • 1. Abiotic synthesis of monomers (amino acids and nucleic acids) • 2. Joining of monomers into polymers concentrated by clay, sand, and heat • 3. aggregation into droplets( protenoids, liposomes, coacervates- ) • 4. hereditary and metabolic pathways- RNA and RIBOZYMES • coacervates, protobionts, precells and the heterotroph hypothesis • coacervate- hydrophobic and hydrophilic portions of large molecules create enclosures • Proto-cell-precursor of cells ( enclosures with membrane characteristics • heterotroph- can NOT make it’s own food and must consume the molecules from which it emerged • Chemoautotroph-use inorganic ( H2S) compounds to make food Endosymbiosis • Eukaryotes resulted from symbiotic associations between small and large prokaryotes. • Ex. mitochondria and chloroplasts have their own double membrane and DNA I. Evidence of evolution Fossils Comparative Anatomy Comparative Embryology Comparative Genetics and Biochemistry Systematic Fossils mold-impression left by remains in sediment imprint- thin carbon film cast- mold is filled by sediment petrifaction- replacement by minerals amber and preserved remains Mold Molds • When an organism is buried, it can decay leaving an empty space in the rock that is the exact shape of the organism Cast-mold is filled in by sediment • Mold of an organism is created, it often becomes filled by minerals in the surrounding rock, producing a replica of the original organism Casts Amber-resin • Entire, intact organism preserved • Rare, but valuable • Most delicate parts are preserved • (DNA) Petrified fossils • Hard parts of organisms are penetrated and replaced by minerals atom-for-atom • Minerals harden, and an exact stone copy of the original organism is produced • Ex. Wood Imprints • Fossils form before sediments harden • Thin objects like leaves and feathers falling into soft sediments like mud • Entire, intact organism preserved • Rare, but valuable • Most delicate parts are preserved Frozen Trace fossils • Markings or evidence of animal activities • Footprints, trails, and burrows Where are fossils found? Sedimentary Rocks Erosion Law of Superposition Sedimentary rocks are laid down in horizontal layers with the younger layers closer to the surface and the older layers buried deeper. Used to determine the appearance and disappearance of organisms. Oldest layer? Youngest Dating Fossils • Relative Dating – if sediments have been left undisturbed, layers closer to the surface should be younger than deeper layers. • Absolute Dating – a more precise measure of age, years, or time period RELATIVE DATING • Age determined by relative position of strata or by fossil similarities • LAW OF SUPERPOSITION- DEEPER STRATA ( layers) CONTAIN OLDER FOSSILS Relative DATING • Dates determined by where in strata an object is found. • Law of superposition- lower layers are older and those nearer the surface are more recent. Absolute Dating • Radiometric or Radioactive Isotope Dating – measuring the amount of a specific element found in the organism that has radioactively decayed – Carbon-14 = half-life 5730 years • Example: – Carbon –14 Dating – Half-life – the time (in years) that passes when half of the radioactive isotope decays RADIOMETRIC DATING • Use the ratio of radioactive isotope remaining in a specimen to non-radioactive parent material. Half-life- amount of time needed for 1/2 the radioactive isotope to decay into a nonradioactive daughter particle Geologic time scale • List the four Eras and describe the major types of life or major geologic event associated with each: Geologic Time Scale • Four Eras • Most important to know: – Order of the appearance of organisms Precambrian Era • 4.6 billion years – 545 million years ago • Organisms: – UNICELLULAR: Photosynthetic Bacteria and Primitive Prokaryotes – 2 billion years into the Precambrian, first Eukaryotic organisms – Towards the end, simple multi-cellular organisms like algae, sponges, and jellyfish Paleozoic Era • 545 million years – 248 million years ago • Cambrian period - Life explosion! – Invertebrates – Worms, echinoderms and primitive arthropods (trilobites) – Fish, Plants like ferns on land – Amphibians – Reptiles Mesozoic Era • 248 million years – 65 million years • Triassic Period – first mammals (mouse like) led to dinosaurs • Jurassic Period – Age of the Dinosaurs – End of Jurassic – modern birds ancestors • Cretaceous Period – Dinosaur extinction, development of flowering plants, oak, fig and elm trees. Cenozoic Era • 65 million – present • Mammals flourish • Primates • Modern human species approximately 200,000 years ago GEOLOGIC TIME SCALE Views of Change over Time • Gradualismchange in fossil record is slow favors Evolution and Natural Selection • Catastophismperiodic natural disasters have caused changes in fossil records Plate Tectonics • Geological explanation for how the continents move • Pangaea – 245 million years ago • Laurasia and Gondwana – 135 million years ago • 7 continents exist – 65 million years ago Additional Evidence of Evolution Anatomical comparisons Embryological comparisons Genetic and bimolecular comparisons Anatomical comparison • Homologous- similar in origin • Analogous -similar in function • Vestigial structures - no apparent function Anatomical Analysis • Homologous Structure – a modified structure that is seen among different groups of descendants SIMILAR IN ORIGIN Anatomical Analysis • Analogous Structure – any body structure that is similar in function but different in structure SIMILAR IN FUNCTION Anatomical Analysis • Vestigial Structure – body structure that is reduced in function in a living organism but may have been used in an ancestor Anatomical Analysis • Analogous Structure – any body structure that is similar in function but different in structure Embryological comparisons Embryological Development • Similarities between vertebrate embryos • ex. Gill Slits and a Tail Biochemical and Genetic homology • Cytochrome and other proteins are similar • DNA comparisons • RNA similarities • Enzyme comparisons Genetic Comparisons • Homology or Similarities within our DNA ? Evolution as seen by Lamarck1. need 2. Use/disuse 3. Inheritance of Acquired Characteristics • What is wrong with the thinking of Lamarck concerning the inheritance of acquired traits? ADAPTATIONS • Morphological- change in form (size, shape, or color) Physiological- change in body or cell function Behavioral- change in the way an organism interacts with others or it’s environment Summary of Natural Selection • 1. Overpopulation and limited resources • 2. Genetic variation- genetic drift,mutation, polyploidy • 3 Selection pressure- environmental stress • . 4. The struggle for survival leads to survival of the most fit genetic variations which are passed on to succeeding generations Overpopulation and selection pressure • Bacteria struggle to survive in an environment with limited resources. genetic variation 2. Resistant individuals exist as a variation but in small numbers within the bacterial population. • 2. Repeated use of antibiotics creates conditions favorable to selection of resistant individuals Survival of most fit • 3. Antibiotic kills non-resistant members of pop. Reproduction of most fit Only resistant survivors in an unrestricted environment lacking any competition. Entire population becomes resistant Hardy-WeinbergMicroevolution • Describes those conditions that can lead to changes within a population’s genes GENE POOL- the sum total of all genes in a breeding population GENETIC DRIFT- changes in the frequency of an allele The gene frequencies of alleles • For a gene locus where only two genes occur in a pop. Let p = the frequency of one allele and q = the frequency of the other. • Then p + q = 1 ex. ( A + a = 1 ) When gametes combine: The probability of generating a AA genotype is p2 The probability of generating a aa genotype is q2 The prob. of Aa is 2pq Hardy -Weinberg Principle States that if the following conditions occur that the gene pool will not change: • • • • • if matings are random if there are no mutations if there are no migrations if the population remains large if there is no natural selection the gene pool will remain constant These do not all happen in Nature !!!!!! The principle is stated as a null hypothesis Any one of these conditions lead to genetic change? • If matings are not random not all genes are shared equally ( Amish, Jews, and other isolated groups ) • Migrations add to or remove genes • Mutation- changes gene pool quickly • Populations are small - inbreeding • Natural selection favors the most fit - Evolution of Populations Hardy-Weinberg theorem describes microevolution or changes within a populations gene pool The equation used to express gene frequencies within a pop. P2 +2pq +q2 = 1 The Bottleneck Effect • Natural disasters reduce the size of a population. The smaller population is more subject to change than the main group. The Founder Effect • When a few individuals colonize a new habitat. • Galapagos Islands SPECIES • Morphological- based on appearance • Biological- based on number of chromosomes ( ability to mate and produce fertile offspring) • SPECIATION• the development of a new species from and existing one Allopatric speciation • speciation through isolation of a population • geographic isolation • gene pools become separated • genetic change ( variation in alleles, mutation, polyploidy ) • adaptation and natural selection Sympatric speciation • Species is formed within a population • dramatic mutation such as polyploidy • Ontogeny recapitulates phylogeny--- our embryonic development mirrors our evolutionary past Industrial Melanism • Industrial pollution around Manchester England • Peppered Moth exists as two variants Light colored and dark colored living on light trees covered with lichens. Selection pressure changes – predation favors the darker moth variant. Pesticide resistance • DDT classic case of natural selection • Selection pressure favors DDT resistant individuals. • Results in resistant populations. Three types of selection pressure • 1. Stabilizing-favors intermediate phenotype or heterozygote • 2. Directional - favors one extreme form or genotype • 3. Diversifying- favors both extremes or genotypes Selection Pressure • Stabilizing Selection – natural selection that favors average individuals of a population • Average size may be advantageous in terms of survival and reproduction • Spiders Selection Pressure • Directional selection – one of the extreme forms of a trait is favored by natural selection • Woodpeckers with the longest beaks Selection Pressure • Diversifying or disruptive selection – individuals with both extreme forms of a trait are at a selective advantage • Limpets – white and dark brown Mimicry • Batesian- a harmless species adapt to resembles a harmful or unpalatable one- Viceroy/Monarch • Bee /Robber fly FLY WASP MIMIC Viceroy Butterfly MODEL Monarch Butterfly Mimicry • Mullerian – two species that are harmful or unpalatable come to resemble each other over time-Various Species of Bees Co-evolution- two species evolve together Several symbiotic associations Parasite-Host Divergent evolutionbranching out from a common origin -adaptive radiation Convergent evolution- • two isolated species come to resemble each other due to similar environments