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 (preordained)
– 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
Family
Species
Populations
Individuals
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 Generation
Gene Pool
Selection
Fitness
Gene Pool
Second Generation
Gene Pool
N>100 Generations
Gene Pool
N>1000 Generations
Gene Pool
Microevolution
Macroevolution
Speciation
Figure 24.14
24-511
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
Figure 24.4
24-507
Large Scale Physical Changes:
Breakup of Pangeae
Figure 19.19b
19-381b
Geographical Isolation and Evolution:
Darwin and the Galapagos
Figure 19.19a
19-381a
Endosymbiosis: Lynn Margulis
Figure 24.3
24-506
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
Progression of the Sciences Leading to Astrobiology
Habitability of
Extraterrestrial
Systems
Copernican
Revolution
Astrobiology
Sun-Centered
World
Revolutions in Physics,
Chemistry,
Geochemistry, and Life
Sciences
Earth-Centered
World
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
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
Figure 24.28
24-519
Viral nucleic acid and a host cell
Figure 24.29
24-520
Evolution of Humans
Figure 24.17
24-514
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)