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