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 ideab. Evolution – process of biological change by which descendants differ from ancestorsc. 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?

1. Introductiona. Born same day as Abraham Lincoln (1809)b. Went to study medicinec. Hated school and dropped outd. Studied theology1)“Devote” Christian at this point2)Graduated w/BA in theology

B. DARWIN’S HISTORY AND OBSERVATIONS

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 earth2)Theory of evolution3)Didn’t publish right awaya)Wanted it perfectedb)Wife said no…would have hurt the church

4)When it was published - sold out in one day5)Huge difference – most scientists used to be

trained in the Bible

Origin of species videohttp://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

AdaptationVariation

VARIATION AND 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

1. Insights to idea of natural selectiona. Selection Process1)Artificial selectiona)Process where humans change a species by

breeding it for certain traitsb)Can give a lot of variation from other

organismsc) Breed only animals with that trait

C. THEORY OF NATURAL SELECTION

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

Click icon to add picture

Moths that blend in don’t get

Eaten – selected against

NATURAL SELECTION

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

1. Fossilsa. Look at location, age, and environment of fossilb. Certain fossils are only found in some layersc. Primitive fossils are found deeper in rock

D. EVIDENCE OF EVOLUTION

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

1. Fossils – a record of evolutiona. Paleontology – study of fossils or extinct

organismsb. Fossil record is not complete1)Most living things don’t form fossils2)Haven’t looked for fossils in every area of the

world3)Missing links – pg 300

E. EVOLUTIONARY BIOLOGY TODAY

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