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Bio 101: Evolution


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Earliest, oldest

Simple, single-celled organisms
Presence of Trilobites
Age of reptiles, dinosaurs, vertebrates
Age of Mammals

Current Age
Index Fossils
Help compare organisms from different areas
Theory of Superposition
The deeper you go in rock layers, the further back you go.

Deeper is older.

Higher is younger.
Theory of Uniformity
Things happening today occurred in the past.

Mountains rose from the sea and eroded back down.

These take a long time.

Thus, the earth must be very old.
Theory of Evolution
Individuals vary: These are inheritable.

Variation is good/bad/neutral: determined by natural conditions.

Those with good live longer and reproduce more.

Compete for limited resources.

Over time, species change.
"Survival of the Fittest"
Fitness: health and reproduction

Those who survive best and reproduce best leave more offspring.
"Natural Selection"
Conditions of nature determines which variations contribute to health.
"Descent with Modification"
Species will change over time.

Due to Natural Selection, Competition & Survival of the Fittest

Individuals vary - these are inheritable.
Unaltered Fossils
real bone, teeth, amber, mummification
Altered Fossils
carbonization, cast, mold, petrification
Trace Fossils
worm tubes, internal cast, gastrolith
Transitional Fossils
Show changes in species over time.
Radiometric Dating (Purpose)
Actual age to the fossils.

Actual age of Geologic Eras.
Radiometric Dating (Process)
Isotopes are taken in and used like the original element.

Unstable, so decay over periods of time.

By determining how much has decayed, we see how old it is.
Explains why organisms are found where they are.
Continental Drift
Continent moves from Equator to Mid-Latitudes.

Land areas separate into two and move.

Two separate land masses come together --> Climate Changes, Predator/Prey Changes, Natural Selection may change, Species may change

(Marsupials predominate in Australia... Similarity between ostrich, emu, and rhea.
Embryological Similarities
Longer they resemble one another, more closely related they are.
Adolescent Similarities
Longer they continue to be alike, more closely related they are.
DNA/DNA Hybridization
Take DNA from two different species.

Combine to make one DNA molecule.

Heat to break bonds.

More heat needed means more bonds had formed.

Most heat equals most similar.
Agents of Evolutionary Change
Gene Pool
Genetic Drift
Gene Flow
Changes occur in individuals.
If beneficial, will spread.
Allow the individual to benefit from Natural Selection.
Gene Pool
The total of all the genes posible in the population.

A population is limited to the possibilities in its gene pool.
Gene Flow
Changes occur in individuals.

If beneficial, will spread.

Movement of genes within a population.
Non-Random Mating
Mates chosen based on beneficial trails.

Natural Selection is basis for whether a trait is beneficial.

Specials are capable of change due to non-random mating.
Stabilizing Selection
Birth Weight
Directional Selection
Giraffe Neck
Disruptive Selection
Isolation Mechanisms
Things that spearate populations so that genetic drift can occur.

(Pre-mating & Post-mating)
1. Geographic
2. Ecological (habitat)
3. Behavioral
4. Temporal
5. Mechanical
1. Gamete (chemical)
2. Zygote Mortality
3. Hybrid Sterility
4. Second Generation Fitness
Some aspect of geography separates the group.
where they live prevents interaction
actions keep them separate
Reproductive Timing is off
Reproductive apparatus does not fit
Sperm cannot penetrate egg
Zygote Mortality
Fertilization occurs -> zygote does not develop properly -> death results
Hybrid Sterility
Mule example
Second Generation Fitness
Two species mate, produce offspring.

Offspring mates. Second generation is less fit.

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