Download History and Theory of Evolution

History and Theory of Evolution
Evolution Introduction
• Definition:
– Change in a population over time
• Specifically:
– Evolution is the frequency of heritable traits in
population changing from one generation to the
next
Evolution Introduction
• Allele = several variety of changes
• Alleles code for traits to establish form or
structure, physiology, or behavior
• Descent = subsequent generations with
modifications
Evolution Introduction
• Explains:
– Ways organisms suited for environment
– Shared characteristics of life (unity)
• Genetic code
– Diversity of life
• Life became many different forms
2 Views of Evolution
• Microevolution
– Small changes over short periods of time
– Supports improvements in existing species
• Macroevolution
– Small changes accumulating over long periods of
time result in major changes
– Supports the formation of new speices
History of Evolution
• Paved the way for Darwin’s thinking
History of Evolution
• Some Greek philosophers suggested life may
change gradually over time
• Aristotle (384 -322 B.C.) viewed species as
fixed
– Ordered all organisms based on complexity
History of Evolution
Classification
• Carolus Linnaeus
– Developed binomial nomenclature system of
naming organisms
• “nested” classifications system (not linear)
– Opposed the idea of evolution
Paleontology
History of Evolution
• Georges Cuvier
– Studied fossils in strata
• Fossils in older strata have changed
from current life-forms
• Some species appeared and
disappeared
– His explanation: catastrophism =
events in past occurred suddenly
• Boundary between strata
represented a local catastrophe (ex.
flood); area repopulated by
immigration
History of Evolution
Geology
• Charles Lyell
– Came up with gradualism or uniformitarianism
• Change is constant over time
• Same process, same rate
– Sediment deposition is constant
– Catastrophes are common
Pattern of Evolution
History of Evolution
• Erasmus Darwin
– Grandfather of Charles Darwin
– Life evolves as environments change
Pattern of Evolution
History of Evolution
• Jean-Baptiste de Lamarck
– Organisms adapt to their environments by
acquiring traits
– Changes in their lifetime
• Disuse: organisms lost parts because they did not use
them
• Perfection with use and need: the constant use of an
organ leads that organ to increase in size
– Transmit new characteristics to next generation
Lamarck
• Observation of giraffes:
– In order to reach higher vegetation, giraffes
stretched their neck to acquire longer necks
Using Darwin’s ideas:
Giraffes born with
longer necks survive
better and leave
offspring that will
inherit their long necks
Naturalist
History of Evolution
• Charles Darwin (1809 –
1882)
• British naturalist (tried
medicine and clergy)
• Proposed evolution by
natural selection
– Differences in survival and
reproduction in accordance
to their interaction with
environment
Charles Darwin
• Invited to travel around the world in the HMS
Beagle
– 1831-1836
– Made many observations of nature
Robert Fitzroy
Voyage of the HMS Beagle
Observing the origin of the fauna on the
Galapagos
Observations
• Succession of Types
– Current species
resemble fossils in
same area
Why should extinct
armadillo-like species
& living armadillos be
found on the same
continent?
Glyptodont fossils are also unique to South
America.
Observations
Mylodon (left) Giant ground sloth (extinct)
Modern sloth (right)
“This wonderful relationship
in the same continent between
the dead and the living will…throw more light
on the appearance of organic beings on our earth
and their disappearance from it,
than any other class of facts.”
Observations
Observations
• Darwin collected and found birds on
Galapagos islands
– Thought they were very different kinds
– However…14 birds species were different types of
finches
– Only one species of finch found on the mainland
How did
one species
of finches become
so many different
species now?
Observations
Descendant species
Ancestral species
Observations
• Correlation of species to food source
Seed Eaters
Flower
Eaters
Insect Eaters
Darwin’s Finches
• Found differences in beaks
– Associated with different foods
Darwin’s Finches
• Conclusions:
– Small populations of original South American
finches landed on islands
• Variation in beaks enabled individuals to gather food
successfully in different environments
– Over generations, population of finches changed
anatomically and behaviorally
• Accumulation of advantageous traits in population
• Emergence of different species
Darwin’s Finches
• Differences in beaks:
– Successfully compete
– Successfully feed
– Successfully
reproduce
• Pass on successful
traits
– Natural selection
More observations
• Correlation of species to food source
Whoa,
Turtles, too!
More Observations
Many islands also show
distinct local variations
in tortoise morphology
…perhaps these are
the first steps in the
splitting of one species
into several?
Darwin’s Return
• Returned to England in 1836
– Wrote papers describing
observations
– Wrote his theory of species
formation in 1844
• Instructed his wife to publish his
ideas after his death
• Reluctant to publish but did not
want his ideas to die with him
But…
• 1858 = Darwin received
letter from Alfred Russel
Wallace
• Wallace published article
similar to Darwin’s
unpublished idea of
natural selection
– Asked Darwin to evaluate
his ideas and pass it along
for publication
It was time!!!
• Became a race of who will publish first and
what will be better accepted
• Wallace published his article on “The
Tendency of Varieties to Depart Indefinitely
from the Original Type” (1858)
• Darwin published “The Origin of Species by
Means of Natural Selection” (1859)
Patterns of Evolution
• 3 types of evolution (describing organisms in
relation to one another):
1. Divergent (adaptive radiation) = similar
organisms become increasingly different
because of different types of environments
Patterns of Evolution
2. Convergent evolution = different
organisms become increasingly similar
because of similar types of environments
Patterns of Evolution
3. Coevolution = two nonrelated species
change because of close interaction
• Predator-prey (disease & host)
• Competitive species
• Mutualism (pollinators & flowers)