Biology 321: Mechanisms of Evolution
May 3
whitinga@macewan.ca
Wed & Fri 1-2pm
Topic 1: Why study Evolution; History of Evolutionary Biology Chapter 1
It all begins with a simple Idea
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Darwin Proposed Idea of evolution that described a single origin
Why Study Evolution
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Critical for understanding biology. Evolution is the only scientific explanation for the diversity of
life
Principles of evolution underlie improvements for agriculture
o Natureal selection accounts for rise in pesticide resistance
o Informs designs of new technology to protect crops from disease
Scientists apply lessons from evolutionary biology to clean up toxic environments and
conservation
Species adapt to climate change
Understanding evolution is central for advancement of medicine
Evolutionary medicine devoted to study and treat human illnesses
Learn about scientific method & how we gather information, test hypothesis, come to
consensus about explanations.
Evolution as a fact – evidence to prove these things happened
Evolution as a theory – natural selection (mechanism in evolutionary theory)
Evolution as a path – Deals with general processes but understand history – facts of history
Appreciate modern biology
Develop understanding of main kinds of evidence for evolutionary
Natural selection can exist without evolution
o Changes in population without having consequences on genetic gene pool
Be able to understand and evaluate research and how it shows evolutionary concepts
Able to judge reliability of statements made in media
Explain evolutionary concepts to people who are unaware (not trained)
Evolution: What is it?
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Latin: Evolvere “To unfold or unroll”
Current: Simply “to change” (Change in stars, fashion etc)
Biological/Organic Evolution “Change in beings from one thing to another”
o Change in a lineage of population between generations
o Change in allele frequencies over time
o Change through time in living organisms
o Change over time in the proporations of individual organisms differing genetically in
one+ traits
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Descent with Modification (Darwin)
 Darwin misses one of the biggest of evidence based ideas (genetics)
Evolution: Themes
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Process (Microevolution)
o How the process occurs
o Bacteria are undergoing change & they lack genetic repair mechansism – bacteria
change over time –
History (Maceoevolution)
o Process created history with many unique events
Early History of Evolutionary Biology Ancient Misconceptions
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Aristotle
o Line of academic descent
 Socrates -> Plato -> Aristotle -> Alexander the Great
o Scala (scale) naturae (nature) “Scale of nature”
 Great chain of being
 Ladder of nature/life
 Linear evolution from simple to complex organism
o Small at bottom, human at top
 Species permanent & unchangeable
 Species perfectly adapted to their environment
Pliny the Elder
o Roman naturalist, wrote Natural History
o Fossils like shark teeth fell to earth during lunar eclipse “Glossopetrae” (tongue stones)
o Other fossils grew in earth
Carolus Linneaus
o Botanist, Doctor, Naturalist
o Binomial system of naming organisms
 Variety of naming system was to demonstrate glory of creation and diversity on
planet viewing similarities
James Hutton
o Theory of the Earth
 Earth is ancient – most people believed earth was only 6000 years old
 Uniformitarianism
 Present is the key to the past (things that happen today happened in the
past)
 Gradualism
 Features of earth are slow accumulation of events
Thomas Robert Malthus
o Principle of Population
 Population grows geometrically
 Food increases arithmetically
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Suggests there is a crisis point where the population surpasses the food
available
o Struggle for existence
Jean Baptiste Lamarck
o French Naturalist
o Theory of Evolution
 Recognized that changes occur “Change over time”
 Organisms continually change to become better adapted to their environment
 Features acquired during life can be passed onto offspring
Georges Cuvier
o French Naturalist, Zoologist
o Father of comparative anatomy and paleontologist
o Opposed ideas of evolution (Correlation of parts)
o Change through Catastrophism
 Only natural catastrophes could account for the changes
 Continual change through catastrophies
Charles Lyell
o Scott geologist – principle of Geology
o Helped Darwin work through evidence based on descent with modification
o Took Hutton’s ideas and gave wide audience
o Advocated Uniformitarianism and gradualism
 Earth was very old.
Charles Darwin
o Family of doctors – but Charles dropped out
o Theology, Natural History
o HMS Beagle (1831-1836)
 Surveyed south America
 Friended botanist John Henslow
 Invited as companion to captain
o Darwins travel
 Canary Island
 South America
 Galapagos Island – Group of birds “Galapagos Finches”
 New Zealand
 Australia, Tasmania
o He noted the similarities of species between places and recognized changes in temp and
moisture occur and fit their environment but share common forms
o Observations
 Similarity (unity) and Dissimilarity (Diversity)
 Redundant forms from place to place
 Variation on basic for m within a region
 His goal was to describe where species came from
 Lyell’s discovery of deep time provided support
 Descent with modification over great time
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Alfred Russel Wallace
o British Naturalist, Biologist, Geographer, anthropologist, explorer
o Independently proposed theory of evolution due to natural selection
o Darwin & Wallace joint paper presented at the linnean society of London by Charles
Lyell & Joseph Hooker
Organizing Life
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Scala Naturae
o Aristotle 350 BC
o Species are fixed = unchanging
o Organized by complexity with man on top
Darwin & Wallace presentation; controversial
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Opponents
o Richard Owen (UK): Botany, anatomy; evolution is more complex than Darwin’s Theory
o Louis Agassize (USA): Ice age, fossil fishers
Defenders
o Joseph Dalton
o Asa Gray
o Alfred Russel Wallace
o Thomas Huxley
Explanatory Power of evolution by natural selection
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Discovery of Archaeopteryx lithographica
o Oldest fossil bird from Jurassic of Germany
o Intermediate between birds and reptiles
 Had teeth, claws (reptiles) but feathers, beaks (birds)
Discovery of missing-link animals
o Lungfish show how
o Platypus
Darwin Revolutionized biology and geology
o Concept of tree of life; natural selection; classification by shared descent; selectivity of
extinction; depth of time; geographical isolation; sexual selection; co-evulation
Henry Bates Theory of Mimicry
o Butterflies of different types look alike (Amazonian butterflies)
o Process of natural selection
Gregor Mendel
o Principle of inheritance
Evolutionary Synthesis or Modern Synthesis
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Explored ideas from genetic change to gene flow, mutation, sexual selection, genetic drift lead
to speciation
Term coined by Julian Huxley
Movement married Darwin evolution and natural selection
Molecular Era
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Double helix structure of DNA
o Roslind Franklin
o Watson and Crick
PCR technology
Scientific Framework
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Assumption of science
o Scientific hypothesis, predictions, and tests assume uniformitarianism
 Assume that the same fundamental process that operates in our universe today
will be operating tomorrow and yesterday
 Uniformitarianism is fundamental to all sciences.
May 5, 2022
Classification of Organism
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Before Darwin
o Kinds, types, ideals
o Similarity, characteristic features
After Darwin
o Shared ancestry
o Phylogeny (genealogical relationship)
o Adaptations
Tree of Life
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One common ancestor or multiple?
o Darwin suggested there was one and he was right
o Archaea (Prokaryote), Bacteria (Prokaryote), Eukarya (Eukaryotes)
Domain Eukarya
o Fungi
o Animals
 Shares more in common with fungi than plants
o Land Plants
Last Universal Common Ancestry
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Eukaryotes
o Multicellular
o Membrane bound organelle
o Heterotroph
Prokaryote
o Single cell
Phylogenetic Tree & Darwin
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Darwin’s Diagram of phylogeny
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First diagram in 1859 shows a single origin separating groups by similarities where some
exist and some go extinct. Shows ancestors
Linnean Taxonomy
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Domain Eukaryote
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Primates
Family Hominidae
Genus Homo
Species Homo Sapien
Shows things that have features in common is because they may have shared ancestry
o Taxon: Second word
o Categories: First word
 Hierarchical
o Darwin’s tree
 Shared adaptations
 Shared ancestors
Review of Topics 1-2
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What did James Hutton do?
o Suggested Earth’s age “Theory of Earth”
What did Cuvier do?
o He was against evolution
o Change only through catastrophism
What did Lamarck do?
o Provided first theory of evolution
o First mechanism: The use and disuse
 Species were continually adapting themselves
Differentiate micro and macroevolution
o Micro : Genetic level
o Macro: Species Level
Differentiate Classification from Systematics
o Classification:
o Systematics: Unite classification with evolutionary History. Describes study of biological
diversity
Systematics
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Study of biological diversity that tries to establish phylogenies (evolutionary history)
Helps us understand history of all life
o Can’t see history -only clues to actual events
o Build hypothesis of life history
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Clatogram: Pictogram that shows the relationships of species through shared ancestry
Phylogeny: The time of break up of lines in clatogram shows the time at which an event
happened
Willi Hennig (1913-1976)
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Best known for developing idea of phylogenetic systematics
Hennigian principle
o Geneaelogical principle
Plesio- vs apomorphy
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Plesiomorphy
o Morphe = form
o Plesio = near
 Near ancestral type
 Ex: Lizard, dino, crocodile have legs
Symplesiomorphy
o Sym = same “together”
o Same ancestral shape – shared ancestral type
o What all species share in common
Apomorphy
o Apo = away from
 Away from ancestral
 Example: Snakes lacking legs
 What makes this different from ancestor
Synapomorphy
o Syn “with” or together
o Shared (together) derived characters
 What do two groups shared difference
Phylogenetic Systematics/Cladistics
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Based on characters that most clearly reveal evolutionary relationships
Many characters can be measured but not all are useful
Shared derived character states (synapomorphies)
Phylogeny directly related to classification
Data for inferring phylogenies
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Characters
o Characteristics of organism
o Variable feature (Bill/beak size)
 External & internal – morphological, behaviour, physiological, cell structure,
biochem, chromosome structure
Character states
o Alternate conditions of feature: Large or small
o Ancestral (Primitive/plesiomorphic)
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o Derived (advanced/apomorphic)
Goal: recreate history of evolution
Monophyletic group
o Set of species derived from any one ancestor
o Recognized by synapomorphies
 Shared, derived characteristics
Phylogeny (tree) with named monophyletic groups
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Each taxon has a single origin
Based on sharing derived states of characteristics
Homology
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Similaries due to shared ancestry
May not have same function
Sharing of homologies among species indicate have evolved from common ancestor that had
same feature
Ex: Share radius/ulna/humerus etc but may differ per species
Analogy – Analogous
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Similarity between structures that is not a result of common evolutionary origin
o They are independently evolved
 Ex: Bat wing vs insect wing
Phenotypic similarity that is not from common descent but due to similarity of function
Homoly/Analogy
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Convergence
o Similar appearance not due to common ancestry
o Could be analogous but NOT homologous
Parallelism
o Independent evolution of similar structure from common ancestgor
 Raptorial feet from perching feet in owls and falcon
Basic rules of Cladistic
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All species in a natural group (clade) share most recent common ancestor
All species that share this ancestor must be included in the group
Mono, Poly, and Paraphyly
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Monophyletic
o Taxon in which all species share a common ancestor and characteristics are derived
from that ancestor
Polyphyletic
o Derivation of a taxon from two or more ancestral sources
Paraphyletic
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Taxon in which all species share a common ancestor but not all species derived from
that common ancestor are included
Ignores some descendents
Phylogenentic Tree/Cladogram
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Operational taxonomic Unit (OUT): Taxonomic level ofsampling selected by user to be used in a
study such as individuals, population, species
Clade: Group of two or more taxa or DNA sequence that includes both their most recent
common ancestor and all descendents
Node: Branch point in a tree
Branch: Defines relationship between taxa in terms of descent and ancestry
Topology: Branching pattens of tree
Branch length: Represents number of changes that have occurred in the branch
Root: Common ancestor of all taxa