TIME

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Evolution is a theory, like many other scientific theories
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Scientists have accumulated significant evidence that modern organisms were produced by change over time.

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Evolution : the process by which a species changes over time resulting from environmental pressure.

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Lived 1809-1882
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Well educated in biology and natural history
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Traveled the world by sea
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The plant and animal life he saw on many of the remote islands he visited, peaked his curiosity.

• Darwin: “Why is it that way?”
– famous for the theory of
Natural Selection:
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Survival and reproduction by individual organisms based on their respective fitness in changing environments.
• “Survival of the Fittest”

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Diversity
– a variety of living things
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Estimates for # of species on
Earth range from 3 to 20 million.
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More than 99.9% of the species that have inhabited Earth are now extinct.

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Fitness-
An organism’s ability to survive and reproduce in a given environment based on its physical traits and behaviors.
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An organism with favorable traits and behaviors is more likely to survive, and pass those traits on to subsequent generations

Principle of Common Descent
• Darwin’s theory that species have shared or common ancestors.
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Just as each individual organisms comes from previous organisms, each species has developed from previous species.

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Adaptation : any inherited characteristic that allows an individual to better survive and reproduce in a given environment
– Tiger’s camouflage stripes
– Polar bear’s thick fur and fat
– Eagle’s talons and beak

Evidence in Living Organisms
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Similarities in Early Development
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Embryology
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Similarities in Body Structure
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Homologous Structures
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Similarities in Biochemistry

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Embryologystudy of organisms at early stages of development
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Vertebrates (for example) show significant similarities during early development

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Homologous Structures structures that develop from the same body parts
Ex: Human arm, dolphin fin, bat wing, bird wing….

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Analogous Structures -
Structures that are not homologous, but serve similar purposes:
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Ex: trachea tubes vs lungs
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Ex: bird wings vs dragonfly wings

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Vestigial Structures - organs or structures that serve no purpose
– wisdom teeth, appendix, snake legs
– whale pelvis

Biochemistry
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DNA/RNA structure identical throughout all organisms
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ATP found in all living systems
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Complex proteins (cytochrome c)
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Closely related organisms have almost identical biochemistry

6.5 Evolution

• A collection of carefully reasoned and tested hypotheses about how evolutionary change occurs.

• Lamarck (1744-1829)
– Natural urge to better themselves
– Use and disuse
– Passing on acquired traits

• Charles Lyell- Understood that
Earth was very old.

• Malthus- Babies are being born faster than people are dying.
• Population must be limited
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Darwin realized that plant and animal populations must be controlled against growth.

• Natural Selection- Survival and reproduction by individual organisms based on their respective fitness in changing environments.

Four Main Parts
1. Overpopulation- more individuals born than can survive

2. Variation- Each individual is genetically different.
3. Competition- Individuals compete for resources:
Food, water, space, mates
“Survival of the fittest”

Natural selection- Individual with best traits (adaptations) to the environment will survive and reproduce.

14-3 Genetics and Evolution
Evolution happens through changes in genes
The environment dictates which adaptations (phenotypes) are favorable.

An individual’s phenotype is controlled by it’s genes
(genotype)
The total amount of genes found in a population is the GENE
POOL

Changes in the Gene Pool can cause the population to evolve
Changes in the gene pool are caused in many ways

Causes of Change
1. Mutations in the genes
(DNA) of individuals allowing new adaptations
2. Geographic Isolationpopulation is split by some physical barrier: river, mountain, ocean

3. Reproductive Isolation: individuals unable to breed together: behavior or physical characteristics
4. Temporal Isolation: changes in mating cycles

The formation of a new species from a preexisting population is
SPECIATION.

Some species evolve to new environments with new adaptationsdivergent evolution

The environment also causes different creatures to become similar looking-
Convergent Evolution

4-5 Evolutionary Theory Evolves
Genetic Drift is because of evolution by random chance
No Natural Selection
Happens by accident

2 types of Genetic Drift
1. Bottleneck Effect-
Competition is killed and is a random act
2. Founders Effect- No competition in new environment
– the evolution of a new Island.

Rates of evolution
1. Gradualism-
Slow steady evolution of species

2. Punctuated
Equilibriumlong periods of no evolution, then brief periods of change

• Earth’s age is estimated at 4.6 billion years.
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James Hutton in 1788- proposed that features of the earth were influenced by volcanoes, erosion, etc.. These things all act very slowly

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In 1830, Charles Lyell agreed that the earth had been shaped over a long period of time…but also stressed the importance of explaining theory in terms of scientific method.

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Relative Dating - the age of some rocks “relative” to others based on their position.
NEWER: RECENTLY DEPOSITED
OLDER: DEPOSITED EARLIER

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Absolute Dating : using scientific techniques to find the approximate actual age of artifacts.
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Radioactive Dating : using the known rate of decay to calculate the age of artifacts. ( 14 C)

Element
Rubidium-87
Thorium-232
Uranium-238
Potassium-40
Uranium-235
Carbon-14
Half Life
50 billion years
13.9 billion years
4.5 billion years
1.3 billion years
713 million years
5770 years

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Fossils - preserved remains of ancient organisms
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Formation of fossils- when animals are buried in some medium that prevents decay
– mud, sand, silt, tar pits
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Sedimentary Rock

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Specific conditions are required for fossils to form
– mountains vs. rivers and streams
– many organisms never fossilize
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Not all fossils have been found

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The quality of fossils varies greatly
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As a result, the fossil record is not as complete as paleontologists would like

Cabrian: 500 million

Jurassic: 200 million

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Collectively, the millions of fossils that have been collected make up The Fossil Record
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Many pieces are missing
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Scientists have been able to construct detailed paths of change through time for many species

• Evidence indicates that Earth’s climate has changed significantly over time
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Evidence also shows that species of plants and animals changed to fit those environments, or perished.