PRINCIPLES OF EVOLUTION
Chapter 10 Page 278
A. EARLY IDEAS ABOUT EVOLUTION
1. Early Scientists
a. Darwin was not the first person to come up with
the idea
b. Evolution – process of biological
change by which descendants
differ from ancestors
c. Carolus Linnaeus – developed
classification system for organisms
d. Buffon – proposed that species shared ancestors
instead of arising separately
e. Lamarck
1) Proposed all organisms evolved toward
perfection and complexity
2) Happened b/c changes in the environment
2. Theories of geologic change set the stage for
Darwin
a. Fossils
1) Traces of organisms that existed in the
past
2) Caused from catastrophism – natural
disasters happened often in earth’s history
b. Gradualism proposed – slow changes over
time
c. Charles Lyell
1) Proposed theory of uniformitarianism
2) Uniformitarianism – geologic processes are
uniform through time
3) Theory expanded on gradualism and
replaced theory of catastrophism
4) Challenged young earth views
5) Ex. Ice melting – if you know the rate, do you
have to watch the whole thing melt?
B. DARWIN’S HISTORY AND OBSERVATIONS
1. Introduction
a. Born same day as Abraham Lincoln (1809)
b. Went to study medicine
c. Hated school and dropped out
d. Studied theology
1) “Devote” Christian at this point
2) Graduated w/BA in theology
e. Had an interest in geology
f. Went on a 5 year trip around the world
1) Documented
many different
species
2) Came up with
natural selection
g. Published “The Origin of Species” (1859)
1) Talks about why there is diversity on earth
2) Theory of evolution
3) Didn’t publish right away
a)Wanted it perfected
b)Wife said no…would have hurt the church
4) When it was published - sold out in one day
5) Huge difference – most scientists used to be
trained in the Bible
Origin of species video
http://www.youtube.com/watch?v=vfmOaAz371M
2. Darwin observed differences among island species
a. Variation – differences in physical traits of an
individual from other members of a species
1) Can happen in same species
2) Can happen in different species
b. Adaptation
1) Allows an organism to better survive in
its environment
2) Can lead to genetic change in a
population over time
VARIATION AND ADAPTATION
Variation
Adaptation
c. Darwin’s finches (Galapagos islands)
1) Had similar structures but also some variation
2) Beaks for eating insects/nuts
3) Each came from a common ancestor
4) Birds adapted as food source changed
5) If beaks change, why not other structures too?
3. Darwin observed fossil and geologic evidence
a. Found animals similar to ones today, meaning
there would have to be long periods of time in
order to change
b. Fossils of marine organisms in the mountains
1) Darwin experienced earthquake
2) Saw land that was underwater move above
3) Geologic processes add up over time
C. THEORY OF NATURAL SELECTION
1. Insights to idea of natural selection
a. Selection Process
1) Artificial selection
a)Process where humans change a species by
breeding it for certain traits
b)Can give a lot of variation from other organisms
c) Breed only animals with that trait
2) Heritability
a) Trait can be passed
to offspring
b) Has to have
heritability or natural/
artificial selection wont
work
3) Natural selection
a) Organisms with beneficial trait have more
offspring on average
b) Nature is the selecting agent
c) Traits are selected by what is beneficial and
what is not
d) Doesn’t happen perfectly the first time –
could take many generations
NATURAL SELECTION
Moths that blend in don’t get
Eaten – selected against
ENOUGH SAID
b. Struggle for Survival
1) Food, water, shelter limit population growth
2) Population – all individuals living in that area
3) W/limited resources what
allows one animal to live
and another to die?
2. Natural Selection Explains Evolution
a. Variation
1) Heritable differences are basis for natural
selection
2) Differences b/c of genetics from parents or
mutations
b. Overproduction w/offspring
1) Raises chances of survival
2) Increases completion b/w offspring for resources
c. Adaptation
1) Allows for some organisms to survive over others
2) Individuals are “naturally selected” to live
d. Descent w/modification
1) Over time a certain trait will stay
2) Offspring will be more likely
to have that trait
3) Will cont. as long as environment
doesn’t change
4) Ex. – bottom paragraph pg 288 - 289
e. Fitness – measure of the ability to survive and
reproduce compared to others in the population
3. Natural selection acts on existing variation
a. Acts on phenotypes rather than genotype
b. Changing Environments – pg 290
c. Adaptations as compromises – pg 291
D. EVIDENCE OF EVOLUTION
1. Fossils
a. Look at location, age,
and environment of fossil
b. Certain fossils are only found
in some layers
c. Primitive fossils are found deeper in rock
2. Geography
a. Provides isolation
of populations
b. Find similar
species in similar
rock layers
3. Embryology
a. Developing embryos look similar
b. Very difficult to tell apart
4. Anatomy
a. Homologous structures – similar appearance
but different function
b. If each of these groups descended from a
different ancestor, why would they share these
homologous structures?
5. Vestigial Structures
a. Remnants of organs or structures that had a
function but not any more
b. Ostrich wings
c. Snakes – pelvic bones and stumplike limbs
d. Humans
1) Appendix
2) Tail bone
E. EVOLUTIONARY BIOLOGY TODAY
1. Fossils – a record of evolution
a. Paleontology – study of fossils or extinct organisms
b. Fossil record is not complete
1) Most living things don’t form fossils
2) Haven’t looked for fossils in every area of the
world
3) Missing links – pg 300
2. Molecular and genetic evidence
a. Pseudogenes
1) Sequences of DNA nucleotides
2) Similar to vestigial structures
b. Homeobox genes
1) Control development of specific structures
2) Found in all organisms
3) Indicate distant common ancestor
c. Protein comparisons
1) Unique set of proteins found in specific cells
2) Cell from different species with similar proteins
show common ancestry