Download Evolution - Smyth County Schools

Evolution
By Diana L. Duckworth
Rustburg High School
Campbell County
Two Separate Issues
• Does evolution occur?
– Immutability of species or transmutation of
species
– Did all life originate from one common
ancestor?
• If evolution occurs, how does it occur?
Before Origin of Species
• Erasmus Darwin –
physician, poet
– All life descended from
single filament
– Grew in complexity;
capacity for self
improvement;
improvements handed
down to offspring
– Darwin’s grandfather
http://a-evolucao-de-darwin.weblog.com.pt/arquivo/2008/02/concurso_erasmus_darwin
Lamarck -Philosophie Zoologique
• French – translation
problems
• After career of 30 years
abruptly became an
evolutionist (1800)
– Spontaneous generation
– Tend toward complexity
• Explanation:
– Pressures from environment –
new needs
– Use certain organs more; grow
larger
– Acquired characteristics are
heritable
http://bio.research.ucsc.edu/people/bernardi/Marina/public_html/Bio175/Bio175Website/Index.html
Important Influences on C. Darwin
http://www.lakesideschool.org/
studentweb/worldhistory/mode
rnworld/ThomasRobertMalthus
essay.htm
http://io.uwinnipeg.ca/~simmons/16cm05/1116/16evolut.htm
• Malthus – populations
grow exponentially;
competition for food so
not all survive
• Charles Lyell – professor
at Cambridge; lifelong
friend & advisor
• First textbook of geology
– Propounded uniformitarian
principle instead of
catastrophism
– Earth history built up
through small, gradual
changes
– Earth is very old
Charles Darwin
• Young man – without real
direction
• Obtained position on
HMS Beagle as
companion to captain
• Voyage 1831 – 1836
• Started out believing
common view – species
are immutable
http://nayagam.wordpress.com/2006/02/
Changing Ideas
http://www.geol.umd.edu/~jmerck/galsite/research/projects/hayeslip/darw
in.html
http://www.mccullagh.org/image/d30-3/iguana-closeup.html
• During voyage, Darwin
became convinced that
species do change over
time – the transmutability
of species
• Fossil evidence from
South America
• Similarity of species in
Galapagos to those on
South American mainland
Galapagos
• Chance remark by
governor of
Galapagos –
• Can tell what island a
tortoise comes from
by the shape of his
shell
Mockingbirds
• Darwin recognized
mockingbirds
– Labeled with island of
origin –
• Gave them to bird expert,
John Gould, on his return
to London
– Gould found 3 speices
among specimens
– Each species from a
different island!
http://www.hiltonpond.org/ThisWeek020501.html
http://www.birddigiscoping.com/2005_10_01_archive.html
http://costaricaphoto.wordpress.com/
Collected a bunch of little brown birds;
based on beaks, he thought they were a
mix of grosbeaks, wrens, finches &
orioles; did not label collection location.
http://www.avianweb.com/finchspecies.htm
“Darwin’s” Finches
• Gave them to John Gould
– All finches – 13
species!!
• Now Darwin wondered
– how could 13 different,
but closely related
species arrive in the
Galapagos?
• His answer
– one arrived & evolved
into 13 species
http://www.greenclub.bc.ca/Green_Club_Activity/GVRD_Parks_Events/gvrd_parks_events.htm
Insights led to theory
• Idea was fully formed
by 1838
• Filled series of
notebooks which
contain every
important concept in
evolution
• Done by 1844
• Yet he did not publish
until 1859
http://www.shimer.edu/admissions/dialectic-natural-sciences.cfm
Why the delay?
• Darwin had very poor health. Long periods of inactivity.
• Knew dramatic impact of his ideas & wanted to support
them with more data.
• Began work on barnacle classification which took 10
years & other experiments to bolster his theory.
• Other considerations:
• Impact on his marriage since his wife was pious
Christian, distractions & responsibilities of family &
community life; political climate (he was establishment,
idea might encourage radicalism); did he not want to
offend his friends in clergy?
What prompted the publication
• Competition from a young
naturalist working in East
Indies
• Alfred Russell Wallace
• Independently happened
on the same idea, even
calling it “natural selection”
• Observed the change from
Australian to Asian species
in the Indonesian Islands
• Darwin simply did not want
to be scooped! His ego
would not allow it!
http://www.thebeagleproject.com/2007/03/i-am-afraid-ships-on-fire-or-why-this.html
Wallace Line
http://people.eku.edu/ritchisong/RITCHISO/birdbiogeography.html
On the Origin of Species
• Took Darwin one year to complete and publish
manuscript. He could not include all of the data
he had amassed in intervening years.
• First half of Origin he answered the question
“HOW?”
– Natural Selection
• Second half he presented arguments from four
areas of research that supported the concept of
transmutation of species & that all life had
evolved from a common ancestor.
– Biogeography; comparative anatomy; embryology; &
paleontology (fossils)
Natural Selection
• Populations of a species have variability in
traits & these traits are heritable.
• A trait may convey a survival advantage
on the individual possessing it.
• These individuals survive to reproduce in
greater numbers.
• Advantageous trait is passed on to their
offspring.
• Advantageous trait increases in
population.
Speciation
• Isolation of a population is required for
natural selection to produce another
species.
• May be geographic isolation.
• Changes in the environment produce the
selective force which causes natural
selection.
From 1859 to 1882
• Darwin was already well known in
scientific circles for his body of work
• This book made him famous at all levels of
society and on all continents
• It quickly sold out & there were 5 more
editions
• Subject of much rumor; not everyone read
the book & just over simplified ideas &
distorted them.
Single greatest misconception:
• Man evolved from monkeys…. Man was not
discussed in Origin but in a later book, The
Descent of Man…
• What Darwin said:
• All life developed from a common ancestor –
note that the word evolution does not appear in
Origin
• In other words, man and monkey had a common
ancestor that was neither man, nor monkey
Greatest Flaw
• Darwin did not abandon some of the
Lamarckian ideas
• He did not know of the work of Gregor
Mendel, so he did not know the reality of
inheritance
• Enamored of idea of use & disuse (use it
or lose it)
• Did not refute the idea of the inheritance of
acquired traits.
How does transmutation occur?
• Natural Selection – survival of the fittest
• Individuals with traits that give them an
advantage in their environment will survive
and reproduce, thus passing these
advantageous traits on to the next
generation.
– Populations must have variable traits
– These traits must be heritable