Darwin & Evolution
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Transcript of Darwin & Evolution
Darwin & Evolution
Evolution
“Nothing in biology makes sense except in the light of evolution”
Theodosius Dobzhansky
Evolution• Evolvere
– “to unfold or unroll”• Central organizing concept of how
the world and organism have come to function
• Builds on accumulating knowledge– Need organisms history to fully
understand it• Descent with modification
– Often with diversification
Evolution• Descent of organisms from common
ancestors• Genetic change in a population or
species over generations• Heritable changes that have
produced characteristics more suited for the environment
Before there was Darwin…
Anaximander
•16th Cent BC
Living creatures formed from water
Humans and animals descended from fish
Interpreted observations of Sharks/dogfish as intermediaries between fish and land animals
History of Evolutionary thought
Plato 427-347 BC• Essentialism
– Essence- perfect form
– Earthly plane & essential plane
• Static world• Variation
– Imperfect earthly representation
– Only essence matters
Aristotle 384- 322 B.C• Essentialism with taxonomical
organization• Scala Naturae
– Aka Scale of nature– Aka ladder of nature
• God created all species– No gradation among species– No new species, no extinctions
• Spontaneous generation
Scala Naturae
…….Add Judeo-christianity
Historical Time Frame• Plato/ Aristotle
– Essentialism- fixed species• Victorian era- 1700-1800• “Pre- science”• Natural Theology- Life’s diversity attributed
to god’s splendor– God created all diversity – Earth very young
• Role of science to catalogue god’s creatures– “god’s splendor in the intricacies of life”– Taxonomy
Victorian Era• Victorian era
– Conservative, chaste– Lack in education– Lack in communication
• Christianity dominated– Earth created in 7 days– Earth is not old 6000 yrs– Earth is static
Carolus Linnaeus, 1707-1778
Newton 1643- 1727• Explained physical phenomena• Introduced Mechanistic ideology
– Explain the world outside of god– Introduced the power of reason
• Beginnings of an atmosphere that encouraged the questioning of old beliefs
• Spurred the “Age of Enlightenment”– Faith in progress & the power of reason
Cuvier 1769-1832• Paleontology, geology, comparative
anatomy• History of life documented via fossils
– Older fossils deeper– Unique species at each depth
• Extinction via catastrophism• Form & function• No evolution
– So complex could not be altered
James Hutton 1726-1797• Father of Geology• Earth is OLD
– “no vestige of a beginning, no prospect of an end”
– Older than 6000 yrs• Processes of earths changes can be
explained by present time processes– Ex water
• Gradualism– Profound change is the cumulative product of
slow continuous processes
Charles Lyell
• Geologist• Principles of Geology• Earth is very old• Uniformitarianism
– Geological processes have not changed over time- same rate today as in past
– Responsible for timeline of earth
Thomas Malthus 1776- 1834• Economist, Population study• “Essays on the principle of
population” 1798• Populations grow faster than food
supply • Not all survive….struggle for life
Jean Baptiste Lamarck• First to propose Evolution• Proposed idea adaptation• Inheritance of acquired
characteristics– Introduced mechanism of evolution– Use and disuse
• Incorrect mechanism• Ridiculed
Evolution was in the air…• Mechanistic thinking (Newton)• Timeline- earth old (Hutton & Lyell)• Fossil evidence (Cuvier)• Relatedness amongst species- descent via
inheritance of characteristics over time (Lamark, buffon)
• Adaptation to environment (Lamark)• Struggle for existence (Malthus)• BUT natural theology is still prevalent
Darwin
Voyage of the Beagle, 1831
Similar Solutions• Adaptation
– Trait that aids in the survival or reproduction of an organism
Fossils
GalapagosDarwin had• Perspective• Time to read• Specimens survive• Galapagos
Artificial Selection• Intentional
breeding for desirable traits
Darwin’s Observations• Diversity• Similar solutions- ie adaptations• Fossils• Geographic distribution
– Environment influences distribution of plants & animals
• Read & incorporated the work of others– Malthus- population– Lyell- earth old
• Artificial selection
Darwin
• The origin of species• “on the origin of species by
means of natural selection, or the preservation of favored races in the struggle for life”– Descent with modification– Theory of natural selection
Wallace 1823-1913• Naturalist• Father of Biogeography• “on the tendency of varieties to
depart indefinitely from the original type”
• Independently conceived natural selection
• Not so lucky
Origin of Species• Descent with modification
– Aka evolution– All organisms related through descent from some
unknown ancestor– Happened over long periods of time– Adapt to environment– Well accepted within 15 years- timing
• Differential reproductive success– More offspring than can survive will be produced
• Struggle to survive– Variation among individuals– Best suited for the environment will survive– Aka Natural selection
What was Darwin Missing?– Mechanism of inheritance
• Hershey & Chase 1952 • Linked DNA to inheritance
– Direct evidence for natural selection• Grant & Grant 1972-2003• Darwin’s finches in Galapagos
Evolution….After Darwin…
Evidence of Evolution• Fossil record• Biogeography• Comparative anatomy• Comparative embryology/
development• Comparative behavior• Molecular biology
Fossils• Fossil any preserved remnant or
impression of an organism that lived in the past
• http://www.youtube.com/watch?v=VtWdUG4nNCU• http://www.youtube.com/watch?v=34eKAm48LfM
Conditions that Favor Fossilization:• Having Hard parts – shells, bones,cysts
• Get buried, trapped– Marine species– Marsh, flooding areas– Limitation: Has to die in right place under the right conditions.
Most things don’t get into the fossil record• Abundant species (with many individuals)• Long lived species (as a species)• Avoid eroding away• Get discovered
– Limitation: Only certain areas highly researched – Limitation: Highly favors hard parts, abundant, long lived species
organisms.
Biogeography• Study of geographic
distribution• Use to study how
lineages of animals evolved
Comparative Anatomy• Comparison of body
structures among taxa to understand evolutionary relationships/ history– Homologous vs analogous
Homologous Structures• A characteristic
shared by 2 or more taxa that evolved from the same structure in their common ancestor
Analogous Structures• Analogous structures have a similar
function but DO NOT share common ancestry
Comparative Embryology• Compare
developmental patterns (ontology) to understand common ancestry
Comparative Behavior• Compare behavior to understand
common ancestry
Molecular Biology• Study of DNA
sequences to understand evolutionary relationships
• Revolutionized our understanding of evolutionary biology
Modern Synthesis• Modern view of our understanding of evolution• A comprehensive theory of evolution emphasizing
natural selection, gradualism, and populations as the fundamental units of evolutionary change
• New Terms– Evolution= slow accumulation of change over time– Mechanism of change= natural selection
• Editing– Evolutionary adaptation
Survival of the Fittest….
Natural Selection• Mechanism of evolution caused by
environmental selection of organisms most fit to reproduce• Aka Reproductive advantage
• Results in adaptation to the environment
Adaptation• A feature or characteristic that
increases survival or reproductive success
• Increases fitness relative to an alternate trait (gene allele)
Natural selection results in populations that are better adapted To their parent’s environment
Fitness• Relative Fitness
– Trait that results in increased reproductive success
Charles Darwin and The Tree of Life
• http://video.google.com/videoplay?docid=1589429273035937450