evolution of living systems introduction –power of the theory: diversity and similarity of life...
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Evolution of Living Systems
• Introduction– Power of the theory: diversity and similarity of life forms– Theory and a Gift
• Historical context of evolution• Processes and mechanisms of evolution• Origin and evolution of life
– Earth– Astrobiology– Classification
• Specific topics for discussion– Viruses– Evolution of humans– Evolution in action: literally “as you sleep”
Take-Home Messages
• Darwin, Voyage of the Beagle and the Origin of Species: power of observation coupled with intuition
• 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)
• Mechanism of evolution underpins our understanding of origin of life of earth, evolution and classification of organisms, and emerging sense of origin of life forms elsewhere in the universe (astrobiology)
• “As you sleep”, evolution is in action, and notable examples are 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
Evolution of Living Systems
• Introduction– Power of the theory: diversity and similarity of life forms– Theory and a Gift
• Historical context of evolution• Processes and mechanisms of evolution• Origin and evolution of life
– Earth– Astrobiology– Classification
• Specific topics for discussion– Viruses– Evolution of humans– Evolution in action: literally “as you sleep”
Introduction
• Two sides of the same coin– Diversity of life forms– Similarity of life forms (you are a worm)
• Theory of evolution– What is a theory?– Define theory of evolution
• Species arise/evolve gradually from ancestral species• Mechanism is natural selection
• Gift to biology– Unifying theory around which to explain the diversity and
similarity• Evolution preserves traits that confer an advantage• Evolution also adopts new traits that confer an advantage
– Impressive and substantial underpinning to the life sciences (ecology, environmental sciences, genetic engineering, astrobiology, etc.)
Evolution of Living Systems
• Introduction– Power of the theory: diversity and similarity of life forms– Theory and a Gift
• Historical context of evolution• Processes and mechanisms of evolution• Origin and evolution of life
– Earth– Astrobiology– Classification
• Specific topics for discussion– Viruses– Evolution of humans– Evolution in action: literally “as you sleep”
Historical Context: Darwin
• Voyage of the Beagle on the HMS Beagle (1831)– Age 22 as naturalist to catalogue plants and
animals (simply observe and document)– Convention at the time: static view (pre-
ordained)– Frame of reference for Darwin: UK landscape
about as bland as UK food
Notable Observations by Darwin
• South American diversity of landscapes– Brazilian rainforest– Grasslands/savannas of Argentina– Dry deserts of Terra del Fuego (tip)– Towering mountains of the Andes on west coast
• Flora and fauna distinct from Europe and UK• Battery of structures (plants and animals) that had
intuitive value in the environment (adaptations)• Seeding of idea: living systems are not
static/preordained but vary as a function of the environment
Observations (cont’d)
• Galapagos Islands (key event to Origin of Species)– Volcanic series of islands of Ecuador and
Peru (800 km); recent geological origin– Fauna (birds, tortoises, etc.)
• not observed anywhere else• Distinct lineage to species on S. American
mainland (e.g., 13 species of finches)
– Seeding of idea: fauna arrived from mainland and the diversified
Darwin in England (1836)
• Two seminal ideas in 1830’s– Malthus: population growth far exceeds available
resources (all organisms)– Competition for limited resources (food, water, light,
mates) limits number of offspring that survive (e.g., maple tree produces 1000’s of seed of which perhaps 10 germinate and grow – 0.0001%)
• Hypothesis: Environment drives the origin of species
via the gradual accumulation of traits that steadily 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
• Idea No. 2: Driving force for this differential success is natural selection that acts on the variability among individuals
• Product: Evolution of adaptations to enhance success (fitness)– Relate back to the Voyage of the Beagle (1831)
Darwin: Origin of Species (1859)
• Note elapsed time from first observation (1831) to publication (1959)
• Two principal tenets– Species evolve gradually from ancestral species– Mechanism is natural selection
• Theory of Evolution as a gift to biology– Origin of diversity is _____________– Origin of similarity is _____________
• Consequences for a host of other aspects of the life sciences
Heads: Diversity
Tails: Similarity at the Molecular Level
Evolution of Living Systems
• Introduction– Power of the theory: diversity and similarity of life forms– Theory and a Gift
• Historical context of evolution• Processes and mechanisms of evolution• Origin and evolution of life
– Earth– Astrobiology– Classification
• Specific topics for discussion– Viruses– Evolution of humans– Evolution in action: literally “as you sleep”
Processes and Mechanisms
• Misconception that individuals evolve– Individuals develop NOT evolve
• Populations and species evolve (key levels of hierarchy)Kingdom
FamilySpecies
PopulationsIndividuals
Organs• Evolution at the population level is called microevolution• Evolution at the species level is called macroevolution
Concept of Fitness
• Fitness = relative contribution of an individual to the next generation– Positive fitness– Negative fitness
• Contrast fitness to “survival of the fittest”• Contrast fitness to “struggle for survival”• Example of sexual dimorphism in animals
– Ornate plumage in birds attracts mates– Ornate plumage also attracts predators– Positive fitness: contribution to the next generation
Variation in Fitness
• Organisms vary in their morphology, physiology and biochemistry
• Without variation, no differential fitness as all individuals are the same
• Source of variation is genetics (yet to be discovered)– Inheritance of traits (1860’s)– DNA (1950’s)– Gene sequences (1970’s)
Summary of Mechanism (1940’s)
• Two cardinal foundations of evolution– Natural selection as presented by Darwin– Individuals differ genetically in their fitness
• 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 GenerationGene Pool
Second Generation Gene Pool
N>100 Generations Gene Pool
N>1000 Generations Gene Pool
Selection
Fitness
Gene Pool
Microevolution
Macroevolution
24-511Figure 24.14
Speciation
Large-Scale Changes: Global Selective Agents
• Progressive physical/chemical changes– Carbon dioxide in the atmosphere– Oxygen in the atmosphere– Ultraviolet radiation in the atmosphere– Breakup of Pangeae– Climate change today
• Catastrophic physical/chemical climate change– Asteroid impacts (dinosaurs)
• Instantaneous biological changes– Evolution of enzymes– Endosymbiosis and Lynn Margulis
Earth’s Selective Agents in the Atmosphere
24-507Figure 24.4
Large Scale Physical Changes: Breakup of Pangeae
19-381bFigure 19.19b
Geographical Isolation and Evolution:Darwin and the Galapagos
19-381aFigure 19.19a
Endosymbiosis: Lynn Margulis
24-506Figure 24.3
Evolution of Living Systems
• Introduction– Power of the theory: diversity and similarity of life forms– Theory and a Gift
• Historical context of evolution• Processes and mechanisms of evolution• Origin and evolution of life
– Earth– Astrobiology– Classification
• Specific topics for discussion– Viruses– Evolution of humans– Evolution in action: literally “as you sleep”
Origin and Evolution of Life on Earth
Origin of Life in the Universe: Astrobiology
• Chemicals of life– Information brokers: nucleic acids and nucleotides – DNA and
RNA– Carbohydrates (carbon skeletons for polymers)– Lipids (membranes)– Proteins (enzymes)
• Medium for life is water (H2O)• Chemicals for life are common in the Universe and
environment (temperature) is commonplace• Probability: extremely-extremely high that life has
originated and evolved elsewhere in the Universe at multiple times
• Panspermia hypothesis: life on Earth originated elsewhere in the Universe and was transported here
Panspermia
Earth-Centered World
Sun-Centered World
Habitability of Extraterrestrial
Systems
Copernican Revolution
Revolutions in Physics, Chemistry,
Geochemistry, and Life Sciences
Astrobiology
Progression of the Sciences Leading to Astrobiology
Origin and Evolution of Life: Classification
Domain Domain DomainBacteria Archaea Eukarya
Common Ancestor (4 - 4.5 Billion Years Ago)
Classification of Life on Earth
Evolution of Living Systems
• Introduction– Power of the theory: diversity and similarity of life forms– Theory and a Gift
• Historical context of evolution• Processes and mechanisms of evolution• Origin and evolution of life
– Earth– Astrobiology– Classification
• Specific topics for discussion– Viruses– Evolution of humans– Evolution in action: literally “as you sleep”
Illustration of a virus
24-519Figure 24.28
Viral nucleic acid and a host cell
24-520Figure 24.29
Evolution of Humans
24-514Figure 24.17
Evolution in Action “As You Sleep”
• Antibiotic resistance in microbes– 100+ antibiotics since 1940’s (penicillum)– Generation time for microbes and intense natural
selection for resistance
• Industrial melanism in moths– White versus dark colored moths in UK and pollution
(selection is predation by birds)
• Herbicide resistance in weeds• Cockroaches resistant to insecticides• Genetically Modified Organisms (GMO’s)
Take-Home Messages
• Darwin, Voyage of the Beagle and the Origin of Species: power of observation coupled with intuition
• 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)
• Mechanism of evolution underpins our understanding of origin of life of earth, evolution and classification of organisms, and emerging sense of origin of life forms elsewhere in the universe (astrobiology)
• “As you sleep”, evolution is in action, and notable examples are 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
Omissions from Chapter 24
• Classification (pp 640-650)