Evolution of Living Systems Introduction –Power of the theory: diversity and similarity of life forms –Theory and a Gift Historical context of evolution

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






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.)






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






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






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






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)

Documents

Evolution of Living Systems Introduction –Power of the theory: diversity and similarity of life forms –Theory and a Gift Historical context of evolution