EVOLUTION

I. Theory of Evolution

A. Differences in individuals can lead to changes in an entire species

B. Began with Charles Darwin, now expanded upon by scientists

I. Theory of EvolutionC. Does NOT produce progress in one

direction (its not always good)1. A growing bush:

a. Branches survive from beginning w/o change

b. Branches can die out

c. Branches can grow and branch out, each new branch would be a new species

II. Mechanics of Evolution

A. Darwin – Evolution was nature’s version of artificial selection (farmers breed plants / animals with the traits they want, speed, flower color)

B. Natural Selection – nature chooses who survives, based on traits, and those traits get passed on to the next generation.

II. Mechanics of Evolution

C. An individual can be born with an advantage (stronger, faster) that will help it survive and reproduce

II. Mechanics of EvolutionD. Useful traits first appeared randomly

(mutation) but become more common with each generation

E. Harmful adaptations (reduce chances of surviving or reproducing) decrease over time

II. Mechanics of Evolution

F. A species evolves as the number of individuals with the trait inc / dec over time

G. POPULATION changes as a result of evolution, NOT the individual

III. Evidence of Evolution

A. Fossil Record1. Older layers of rock are on the bottom

(Law of Superposition)

2. Fossils in upper layers are more complex but similar to fossils in lower layers

3. Some fossils are NOT like modern organisms, they died out (extinction)

III. Evidence of Evolution

4. Other fossils are identical to modern organisms (Horseshoe crab looks the same as it did 300 million yrs ago)

III. Evidence of Evolution5. Fossils show changes in environment

and the species that lived there

6. First organisms were single celled, they became more complex until about 1 billion yrs ago, multi-celled organisms began to appear

III. Evidence of Evolution

III. Evidence of EvolutionB. Comparative Anatomy

1. Structural similarities among different organisms (limb bones of human, cat, bat and whale)

III. Evidence of Evolution

C. Comparative Embryology1. Comparing early stages of development

shows similarities that suggest common ancestry (Fish, turtle, chicken and human all have tails in stages of development)

III. Evidence of Evolution

III. Evidence of Evolution

D. Comparative Cytology1. All living things are made of cells and

organelles have same structure and function in most organisms

E. Comparative Biochemistry1. Structure and function of DNA, RNA and

proteins are similar in all organisms. More proteins in common = more DNA in common = more closely related

IV. Overproduction

A. A species makes more offspring than can possibly survive

B. Ex. Bacteria, insects, dandelions, rabbits

IV. OverproductionC. If all offspring survived, the species

would overrun the Earth

D. Population remains the same b/c not all individuals born/hatched will survive to adulthood

E. Species that reproduce quickly and produce many offspring evolve MUCH more quickly than those w/ long reproductive cycles and few offspring

V. Competition for Resources

A. Organisms need resources (food, water and shelter).

B. These are limited so organisms MUST compete for them

C. The best suited will win the “competition” and pass on their traits.

D. Losers generally die before their traits get passed on

VI. VariationA. Organisms in a species are NEVER

exactly alike, due to genetic variation1. Color of rabbits can help against foxes2. Peppered Moth3. Peppered Moth Simulation

B. More diverse a species = greater chance of surviving a change in environment

C. No variation + change in env = endangered species / extinction

VII. Selection by EnvironmentA. Most evolutionary change happens as

a result of a change in the environment.

B. New traits are now favored, which will get passed on.

C. Environment IS the driving force for evolution

VIII. Sources of Gene Variation

A. Mutations – change in base sequence of DNA

1. Random events that cannot be predicted2. Body cell mutations = individual3. Sex cell mutations = offspring4. Most are harmful, organism isn’t born

dies, or it cannot reproduce5. Beneficial mutations may lead to a new

species (polar bear)

VIII. Sources of Gene Variation

B. Genetic Shuffling1. Sorting and recombination of genes

during meiosis and fertilization

2. Gives new and different combinations of genes

IX. Speciation

A. Development of a new species

B. Geographic Isolation 1. Small groups may be segregated from

the large group by an impassable barrier (water, mountains)

2. The small population cannot interbreed with the larger group.

3. If their environment is different, good traits for their env get passed on

IX. Speciation

C. Reproductive Isolation1. Eventually the 2 populations become so

different they cannot interbreed, even if the barriers are removed

2. They are now 2 separate species

3. Kaibab Squirrel Story

IX. Speciation

X. Human Influence on Evolution

A. Bacteria resistant to antibiotics1. Millions are exposed to antibiotic. There

is a chance some have a gene (b/c of a mutation) that makes them resistant to the drug

2. Small number of survivors, some resistant some not

3. They reproduce. If they are exposed to same antibiotic the resistant population will continue to grow

X. Human Influence on Evolution

B. Mosquitoes and DDT1. Same process happens when spraying

for mosquitoes. Can make population of resistant mosquitoes

XI. Human EvolutionA. Genes in Population

1. Microcephalin – 37,000 yrs ago, provided increased art, music and tool making, 70% of present population has gene

XI. Human Evolution

2. ASPM – 6,000 yrs ago, provided for increased language, agriculture, engineering, 30% of present population has gene

XII. ExtinctionA. Disappearance of an entire speciesB. When death rate > birth rateC. Environment changes and the species is

unable to adapt to new conditions

D. Most of the life that lived on Earth is now EXTINCT!! (99.9% is gone)