Evolution Introduction n Historical context of evolution n

Evolution Introduction n Historical context of evolution n Processes and mechanisms of evolution n Origin and evolution of life n Specific topics for discussion n

Take-Home Messages n n n Darwin: Voyage of the Beagle and the Origin of Species: the epitomy of the scientific method Mechanism: natural selection operates on genetic variation at the level of populations and over time gradually changes the gene pool, leading to microevolution (populations) and/or macroevolution (species) “As you sleep”, evolution is in action: GMO’s, pesticide resistance in plants and animals, and antibiotic resistance in microbes Theory of evolution extraordinarily provides the mechanism to explain two sides of the same coin: diversity and similarity of living systems Theory of evolution is a gift of monumental importance in the life sciences, and its importance has only grown since Darwin’s seminal publication in 1859 (Origin of Species)

Introduction n Two sides of the same coin: diversity and similarity Theory of evolution n Define theory of evolution n Species evolve gradually from ancestral species n Mechanism is natural selection Gift to biology n Unifying theory to explain diversity and similarity of all living systems n Impressive and substantial underpinning to the life sciences (ecology, environmental sciences, genetic engineering, astrobiology, etc. )

Historical Context: Darwin n Voyage of the Beagle on the HMS Beagle (1831) n Age 22 as naturalist to catalogue plants and animals n Convention at the time: static view (pre-ordained) n Frame of reference for Darwin: UK landscape and biodiversity as bland as UK food

Notable Observations by Darwin n South American diversity of landscapes and biota n n n n Brazilian rainforest Savannas of Argentina Dry deserts of Terra del Fuego Towering mountains of the Andes Flora and fauna distinct from Europe Plethora of structures with intuitive value in the environment (adaptations) Seeding of idea: living systems are not static but vary as a function of the environment

Observations (Galapagos) n Galapagos Islands (seminal event) n n Volcanic islands off Ecuador and Peru Fauna (birds, tortoises, plants, etc. ) n Distinct lineage to species on S. American mainland n n n Finches Tortoise Seeding of idea: n n fauna arrived from mainland, then Fauna diversified in new environment

Darwin back to the UK (1836) n Two seminal ideas in 1830’s n n Malthus: population growth exceeds available resources Competition for limited resources (food, water, light, mates) limits number of offspring n n maple tree produces 1000’s of seed of which ~ 10 germinate and grow – 0. 0001%) Hypothesis: Environment drives the origin of species via the gradual accumulation of traits that incrementally improve survival over time (centuries to millennia)

Darwin and Natural Selection (1840) Idea No. 1: Organisms differ in their success in reproduction and therefore contribute differently to future generations n Idea No. 2: Driving force for this differential success is natural selection acting on the variability among individuals n Product: Evolution of adaptations that enhance success (fitness) n

Darwin: Origin of Species (1859) n Two principal tenets Species evolve gradually from ancestral species n Mechanism is natural selection n n Theory of Evolution as a gift to biology Origin of diversity n Origin of similarity n

Heads: Diversity

Tails: Similarity

Molecular Similarity/Dis-similartity Number of amino acid differences among animals in reference to humans in the protein hemoglobin Human beta chain 0 Gorilla 1 Gibbon 2 Rhesus monkey 8 Dog 15 Horse, cow 25 Mouse 27 Gray kangaroo 38 Chicken 45 Frog 67 Lamprey 125 Sea slug (a mollusk) 127

Processes and Mechanisms n Populations and species evolve (hierarchy) Kingdom Family Species Populations Individuals n Evolution at the population level is called microevolution Evolution at the species level is called macroevolution n

Concept of Fitness n Fitness = relative contribution of an individual to the next generation Positive fitness n Negative fitness n n Contrast fitness to “survival of the fittest” and “struggle for survival”

Variation in Fitness Organisms vary in their morphology, physiology and biochemistry n Source of variation is genetics (yet to be discovered) n Inheritance of traits by Mendel (1860’s) n DNA structure by Watson and Crick (1950’s) n Gene sequences (1970’s) n Genetic engineering (2000’s) n

Summary of Mechanism (1940’s) n Two cardinal tenets n Natural selection (Darwin) n Individuals differ genetically (Mendel) n Result: gene pool of the next generation is a consequence of the action of natural selection on inherited variation at the level of populations

First Generation Gene Pool Selection Fitness Gene Pool Second Generation Gene Pool N>100 Generations Gene Pool N>1000 Generations Gene Pool Microevolution Macroevolution

Large-Scale Changes: Global Selective Agents n Progressive physical/chemical changes n n Catastrophic climate change n n Carbon dioxide in the atmosphere Oxygen in the atmosphere Breakup of Pangeae Asteroid impacts (dinosaurs followed by mammals) Instantaneous biological changes n Evolution of enzymes

Origin and Evolution of Life on Earth

Origin of Life in the Universe: Astrobiology n n n Chemicals of life n Information brokers: nucleic acids and nucleotides n Carbohydrates (carbon skeletons for polymers) n Lipids (e. g. , membranes) n Proteins (e. g. , enzymes) Medium for life is water (H 2 O) Elements for life are common in the Universe Probability: extremely high probability that life has originated and evolved elsewhere in the Universe at multiple times Panspermia: hypothesis that life on Earth originated elsewhere in the Universe

Panspermia

Origin and Evolution of Life: Classification Domain Bacteria Domain Archaea Common Ancestor (4 - 4. 5 Billion Years Ago) Domain Eukarya

Classification of Life on Earth

Illustration of a Virus Figure 24. 28 24 -519

Some Common Viruses Virus HIV Influenza Ebola virus Influenza virus Smallpox Some forms of cancer Colds Polio HIV

Evolution of Humans

Evolution in Action “As You Sleep” n Antibiotic resistance in microbes n n n 100+ antibiotics since 1940’s (penicillium) Efficacy of antibiotics Resistance to insecticides in cockroaches n “Godzilla the Cockroach”

Evolution While You Sleep Industrial melanism in the peppered moth in UK Peppered Moth pollution as stress followed by selection predation by birds Melanic Peppered Moth

Evolution As You Sleep Genetically Modified Organisms (GMO’s) Cotton plants engineered for frost resistance with DNA insert (Bt gene) from a bacterium