UNIT VIII POPULATION GENETICS CLASSIFICATION Big Campbell Ch

UNIT VIII POPULATION GENETICS & CLASSIFICATION • Big Campbell Ch 22 -28, 31 • Baby Campbell Ch 13 -17

I. INTRODUCTION TO EVOLUTION • Evolution o Change over time in the allele frequency of organisms o Descent with modification • Natural Selection o Populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others o Differential reproductive success • Evolutionary Adaptations o A prevalence of inherited characteristics that enhance organisms’ survival and November 24, 1859

II. A HISTORY OF EVOLUTIONARY THEORY • Carolus Linnaeus (1707 -1778) o Taxonomy • James Hutton (1726 -1797) o Gradualism • Jean-Baptiste de Lamarck (17441829) o Use & Disuse o Inheritance of Acquired Characteristics

II. A HISTORY OF EVOLUTIONARY THEORY, cont • Thomas Malthus (1776 -1834) o Populations • Charles Lyell (1792 -1875) o Uniformitarianism • Gregor Mendel (1822 -1884) o • Alfred Wallace (1823 -1913) o Independent development of evolutionary theory

II. A HISTORY OF EVOLUTIONARY THEORY, cont

II. A HISTORY OF EVOLUTIONARY THEORY, cont • Charles Darwin (1809 -1882)

II. A HISTORY OF EVOLUTIONARY THEORY, cont

II. A HISTORY OF EVOLUTIONARY THEORY, cont • Darwin’s Finches o New species of finches arose from gradual accumulation of adaptations due to variations in food supply, terrain

III. DARWIN’S CONCLUSIONS • Descent with Modification o Four Observations ØMembers of a population often vary greatly in their traits. ØTraits are inherited from parents to offspring. ØAll species are capable of producing more offspring that their environment can support. ØOwing to a lack of food or other resources, many of

III. DARWIN’S CONCLUSIONS, cont • Decent with Modification o Two Inferences Ø Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals. Ø This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the

IV. EVIDENCE FOR EVOLUTION • Direct Observation o Antibiotic/Drug Resistance o Coloration in Guppies

IV. EVIDENCE FOR EVOLUTION, cont • Fossil Record o Succession of forms over time o Transitional Links o Vertebrate descent

IV. EVIDENCE FOR EVOLUTION, cont • Homology o Homologous structures o Vestigial organs Ø Snakes Ø Cetaceans Ø Flightless birds o Convergent Evolution Ø Independent evolution of similar features in different lineages Ø Analogous structures

IV. EVIDENCE FOR EVOLUTION, cont • Biogeography o Geographical distribution of species o Continental Drift Ø Pangaea o Islands are inhabited by organisms most closely resembling nearest land mass

IV. EVIDENCE FOR EVOLUTION, cont • Comparative Embryology o Pharyngeal Pouches Ø Gill slits o Tail

IV. EVIDENCE FOR EVOLUTION, cont • Molecular Biology o Similarities in DNA, proteins, genes, and gene products o Common genetic code

V. POPULATION GENETICS • Population Genetics Ø The study of genetic changes in populations • Population Ø • Species Ø • Gene pool Ø Population’s genetic make-up • Modern Synthesis/Neo. Darwinism

V. POPULATION GENETICS, cont • Hardy-Weinberg Principle – Predicts allele frequency in a nonevolving population; that is, a population in equilibrium – Can be used to determine if a population is evolving – States that allele frequencies in a population will remain constant from

V. POPULATION GENETICS, cont • Five Conditions for Hardy-Weinberg Equilibrium 1) 2) 3) 4) 5) • If any of these conditions are not met, evolutionary change will occur

V. POPULATION GENETICS, cont • Hardy-Weinberg Equation Ø If p = frequency of one allele (A) and Ø q = frequency of the other allele (a), then Øp + q = • Therefore, Øp = Øq = • • Frequency of AA = Frequency of aa = Frequency of Aa = Distribution of genotype frequencies in a population =

V. POPULATION GENETICS, cont Hardy-Weinberg Practice Problems 1. If you know that you have 16% recessive fish (bb), . . . Ø q 2= Ø q Ø Therefore, p = • Calculate the frequency of each genotype using Hardy. Weinberg p 2 + 2 pq + q 2 = 1 Ø p 2 = Ø BB = Ø 2 pq = Ø Bb = Ø bb =

V. POPULATION GENETICS, cont • Hardy-Weinberg Practice Problems, cont 2. If in a population of 1, 000, 90 show recessive phenotype (aa), use Hardy-Weinberg to determine frequency of allele combinations.

VI. MICROEVOLUTION • A change in the gene pool of a population over a succession of generations • Five main causes: üGenetic Drift üGene Flow üNatural Selection üMutation

VI. MICROEVOLUTION, cont • Genetic Drift o Changes in the gene pool due to chance. More often seen in small population sizes. Usually reduces genetic variability. There are two situations that can drastically reduce population size: Ø The Bottleneck Effect: type of genetic drift resulting from a reduction in population (natural disaster) such that the surviving population is no longer genetically representative of the original population

VI. MICROEVOLUTION, cont • Genetic Drift Ø Founder Effect § Genetic drift attributed to colonization by a limited number of individuals from a parent population § Gene pool is different than source population

VI. MICROEVOLUTION, cont • Gene Flow Ø Genetic exchange due to the migration of fertile individuals or gametes between populations – tends to reduce differences between populations • Natural Selection Ø Differential success in reproduction; only form of microevolution that adapts a population to its

VI. MICROEVOLUTION, cont • Mutations Ø A change in an organism’s DNA (gametes; many generations); original source of genetic variation (raw material for natural selection) • Nonrandom Mating Ø Inbreeding and assortive mating both shift frequencies of

VII. VARIATIONS IN POPULATION • Polymorphism Ø Coexistence of 2 or more distinct forms of individuals (morphs) within the same population • Geographical Variation Ø Differences in genetic structure between populations (cline)

VII. VARIATIONS IN POPULATION, cont • Mutation and Recombination • Diploidy Ø 2 nd set of chromosomes hides variation in the heterozygote • Balanced Polymorphism Ø Heterozygote Advantage Ø Frequency-Dependent Selection o Survival & reproduction of any 1 morph declines if it becomes too

VII. VARIATIONS IN POPULATION, cont • Adaptive Evolution due to Natural Selection v Fitness - Contribution an individual makes to the gene pool of the next generation • Three ways in which natural selection alters variation v. Directional v. Diversifying v. Stabilizing

VII. VARIATIONS IN POPULATION, cont • Sexual Selection Ø Can result in sexual dimorphism secondary sex characteristic distinction Ø Intrasexual Selection Ø Intersexual Selection

VIII. MACROEVOLUTION • Origin of new taxonomic groups • Speciation v. Anagenesis accumulation of heritable changes transform existing species into new species v. Cladogenesis budding of new species from a parent species that continues to exist

VIII. MACROEVOLUTION, cont • Biological Species Concept Ø Described by Ernst Mayr in 1942 Ø A population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring; in other words, similar organisms that can make babies Ø Can be difficult to apply to

VIII. MACROEVOLUTION, cont • Reproductive Isolation o Prevent closely related species from interbreeding when their ranges overlap. o Divided into 2 types ØPrezygotic ØPostzygotic

VIII. MACROEVOLUTION, cont Prezygotic Reproductive Barriers

VIII. MACROEVOLUTION, cont Postzygotic Reproductive Barriers

VIII. MACROEVOLUTION, cont • Speciation o Fossil record shows evidence of bursts of many new species, followed by periods of little chance ØKnown as punctuated equilibrium o Other species appear to change more gradually ØGradualism fits model of evolution proposed by Darwin

VIII. MACROEVOLUTION, cont • Modes of Speciation Ø Based on how gene flow is interrupted Ø Allopatric § Populations segregated by a geographical barrier; can result in adaptive radiation (island species) Ø Sympatric § Reproductively isolated subpopulation in the midst of its parent population (change in

UNIT VIII, cont - CLASSIFICATION

I. EARLY EARTH • Formation of Organic Molecules o Oparin/Haldane Hypothesis Ø Primitive Earth’s atmosphere was a reducing environment Ø No O 2 Ø Early oceans were an organic “soup” Ø Lightning & UV radiation provided energy for complex organic molecule formation o Miller/Urey Experiment Ø Tested Oparin/Haldane hypothesis Ø Simulated atmosphere composed of water, hydrogen, methane, ammonia

I. EARLY EARTH, cont • Three Eons Ø First two described as Precambrian o Archaean Eon o Proterozoic Eon Ø Present day = Phanerozoic eon o Paleozoic era o Mesozoic era o Cenozic era • Continental Drift Ø Pangaea Ø Gondwanaland & Laurasia • Mass Extinctions • Biogeography Ø Study of past & present distribution of species

I. EARLY EARTH, cont

II. PHYLOGENY • Evolutionary history of an organism • Phylogenetics - the tracing of evolutionary relationships • Linnaeus • Binomial nomenclature • Taxon (taxa)

II. PHYLOGENY, cont • Relationships may be determined using morphological and molecular simlarities Ø Homology vs. Analogy. . . o Homology likenesses attributed to common ancestry o Analogy likenesses attributed to similar ecological roles and natural selection Ø Convergent evolution o Species from

II. PHYLOGENY, cont • Clade Ø Refers to the set of species descended from a particular ancestral species Ø Relationships illustrated with a cladogram o Branching diagram that depicts relationships among taxa o May illustrate derived character states among taxa. Derived character states are traits not found in ancestral species; indicate a close evolutionary relationship among organisms o Ingroup – Group of taxa being analyzed o Outgroup – Used as a means of comparison; closely related to, but not a

II. PHYLOGENY, cont

II. PHYLOGENY, cont

III. PROKARYOTES

III. PROKARYOTES, cont Classification Methods • Domain Ø Archaea Ø Bacteria • Kingdom Ø Archaebacteria Ø Eubacteria • Shape Ø Cocci Ø Bacilli Ø Spirilla • Gram Stain Reaction Ø Positive

IV. PROKARYOTES - EUBACTERIA • Cell wall § Peptidoglycan § Gram Positive § Gram Negative • Capsule § Adherence § Protection • Pili § Adherence § Conjugation

IV. PROKARYOTES – EUBACTERIA, cont Motility • Flagella • Helical shape § Spirochetes • Slime • Taxis

IV. PROKARYOTES – EUBACTERIA, cont • Nucleoid region • Plasmids • Asexual reproduction Ø Binary fission • “Sexual reproduction” Ø Transformation Ø Transduction Ø Conjugation • Endospore Ø Bacterial “hibernation”

IV. PROKARYOTES – EUBACTERIA, cont Nutrition • Photoautotrophs Ø Photosynthetic Ø Harness light to drive the synthesis of organics Ø Cyanobacteria • Chemoautotrophs Ø Oxidation of inorganics for energy Ø Obtain carbon from CO 2 • Photoheterotrophs Ø Use light to generate ATP Ø Must obtain carbon in an organic form • Chemoheterotrophs Ø Consume organic molecules for both energy and carbon Ø Saprobes - decomposers

IV. PROKARYOTES – EUBACTERIA, cont • Metabolism o Nitrogen fixation Ø Conversion of atmospheric nitrogen (N 2) to ammonium (NH 4+) o Metabolic Cooperation Ø Biofilms o Oxygen relationships Ø Obligate aerobes Ø Facultative anaerobes Ø Obligate anaerobes

IV. PROKARYOTES – EUBACTERIA, cont Prokaryotic Ecology • Decomposers • Nitrogen Fixation • Symbiosis Ø Commensalism Ø Mutualism Ø Parasitism

IV. PROKARYOTES – EUBACTERIA, cont Bacterial Pathogenesis • Koch’s Postulates – Criteria for bacterial disease confirmation Ø Ø • Opportunistic Ø Normal residents of host; cause illness when defenses are weakened • Exotoxins Ø Bacterial proteins that can produce disease w/o the prokaryote present (botulism) • Endotoxins

V. ORIGINS OF EUKARYOTIC CELLS • Endosymbiotic Theory (AKA “Endosymbiont Theory”) • Margulis • Mitochondria and chloroplasts were formerly from small prokaryotes living within larger cells

V. ORIGINS OF EUKARYOTIC CELLS Support for Endosymbiotic Theory • DNA structure • Double membrane • Replication of Mitochondria/Chloroplasts • Ribosomes • Similarities between chloroplast/mitochondrial DNA & specific bacterial genomes, including cyanobacteria • Enzymes

EUKARYOTES

VI. KINGDOM PROTISTA • • Very diverse All _________ Mostly _________ Classified according to eukaryotic kingdom protist is most like, nutrition Ø Animal-like § Ingestive § Protozoa Ø Plant-like § Photosynthetic § Algae Ø Fungus-like § Absorptive § Slime Molds

VI. KINGDOM PROTISTA, cont Protist Phylogeny

VI. KINGDOM PROTISTA, cont Protist Systematics • Diplomonads Ø Lack mitochondria, cell walls Ø Giardia lamblia Ø Trichomonas vaginalis • Euglenoids Ø Most are heterotrophic; may be autotrophic Ø Pellicle Ø Flagellated Ø Many have “eyespot” Ø Euglena Ø Trypanosoma

VI. KINGDOM PROTISTA - Systematics, cont • Alveolates Ø Contain small sacs called alveoli; may help regulate water, ion concentration Ø Dinoflagellates – phytoplankton, also known as “spinning algae” § Red Tides Ø Ciliates – Paramecium, Stentor Ø Apicomplexa - all parasitic; lack cilia, flagella § Plasmodium § Toxoplasma

VI. KINGDOM PROTISTA - Systematics, cont • Stramenopila • Water molds (decomposers), mildews (parasitic), algae (photosynthetic) Ø Diatoms § Photosynthetic; make up most of Earth’s plankton § Have glass-like silicon shells Ø Brown Algae Ø Golden Algae

VI. KINGDOM PROTISTA - Systematics, cont • Foraminiferans Ø Ca Carbonate shells Ø Dead foraminiferans settle on ocean floor; shells become chalk Ø White Cliffs of Dover • Rhodopyhta Ø Red algae Ø Mostly multicellular • Chlorophyta Ø Green Algae § Volvox § Spirogyra § Chlamydomonas Ø Unicellular; may be colonial Ø Chloroplasts, cell walls of

VI. KINGDOM PROTISTA - Systematics, cont • Amoebozoa Ø All have pseudopods § Amoeba v. May be parasitic v. Entamoeba histolytica § Slime Molds

VII. KINGDOM FUNGI

VII. KINGDOM FUNGI, cont Characteristics of Fungi • Heterotrophic by absorption; releases exoenzymes Ø Decomposers (saprobes) Ø Parasites Ø Mutualistic symbionts (lichens) • Hyphae - body filaments Ø Septate (cross walls) Ø Coenocytic (no cross walls) • Mycelium - network of

VII. KINGDOM FUNGI, cont Life Cycle

VII. KINGDOM FUNGI, cont Classification • Phylum Chytridiomycota Ø Most closely related to protists; considered to be most primitive member of Kingdom Fungi Ø Aquatic fungi • Phylum Zygomycota Ø Food mold; Rhizopus Ø Mycorrhizae Ø Produce spores from zygote surrounded by thick covering called zygosporangium; may remain dormant for months; resistant to extreme

VII. KINGDOM FUNGI - Classification, cont • Phylum Ascomycota Ø Sac fungi Ø Yeasts, truffles, morels, Sordaria Ø Produce sexual and asexual spores § Ascus – sexual spore § Conidia – asexual spore • Phylum Basidiomycota Ø Club fungi Ø Mushrooms, puffballs, bracket fungi Ø Basidiocarp – haploid hyphae fuse, meiosis occurs, formation of basidospores

VII. KINGDOM FUNGI, cont Specialized Life Styles • Molds Ø Used to be classified as Deuteromycota or “Imperfect Fungi” Ø No known sexual stage Ø Penicillium • Yeasts Ø Unicellular Ø Reproduce asexually; budding Ø Saccharomyces • Lichens Ø Mutualistic relationship with algae, cyanobacterium Ø Sensitive to air pollution • Mycorrhizae Ø Mutualistic relationship found in 95% of all