Topic 1: Origins of Life

Origin of the Solar System• Earth is estimated

to be ~4.6byo– Radiometric dating

of rocks & meteors• Nebula: cloud of

gas & dust in space• Nebula Hypothesis:

– Gravity pulled much material together (Sun formed)

– Planets: remaining materials

• Hypothesis: Energy from lightning created organic materials from inorganic ingredients

• Experimental Set-Up:– Ammonia, H2O vapor,

Methane, CO2 gases added

– Electricity added (simulate lightning)

• Result: Amino Acids & later nucleotides

Geologic Change• Early belief:

– Earth ~6,000 years old– Life remained

unchanged• “New” Observations

– Rock layers contained differing fossils

– Deeper/older fossils less complex

– Environmental changes thought to affect life characteristics

Charles Darwin

• Observed:– Organisms have variations based upon environment– Some variations proved helpful in particular environment

• Natural Selection: Process where organisms with favorable traits survive and reproduce

• Major concept in biology published in The Origin of Species (1859)

Topic 2: The Theory ofNatural Selection

• Four factors:1) Overpopulation: more offspring are born than can

survive2) Variation: individuals of a population have

differences3) Adaptation: Some variations allow better survival4) Descent w/ modification: Offspring w/ advantages

will make up more of a population

Which rabbit is best adapted?

Which rabbit is best adapted?

Struggle for Survival

• Populations do not grow unchecked– Limiting Factors: food, water, shelter, disease,

predators• Fitness: measure of the ability to survive &

produce more offspring

Changing Environments

• Earth’s environments gradually change– Mountains created– Ocean valleys dry up– Rivers create canyons

• Variations allow some to survive changing environments– With adaptation: more likely to survive & reproduce– Without adaptation: more likely to perish

Are new environments being created and destroyed?

Topic 3: The Evidence to

Support Evolution Theory

• Defined: Collection of known fossils– Most found in sedimentary

rock

• Age determined by depth– Law of Superposition: new

rock forms on top of older rock

• Evidence Conclusions:– 1) Newer fossils are more

complex– 2) Common ancestors:

similarities between ancient & modern life

Radiometric Dating

• Isotopes: atoms of the same element with differing neutrons– Ex: 12Carbon and 14Carbon– 12C = 6 protons + 6 neutrons– 14C = 6 protons + 8 neutrons

• 14C decays at known rate• Fossil age determined by comparing ratio of 12C to 14C

– Wider ratio = older samples

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Scale:1 minute = 3 million years

• Show transitions between groups of organisms– Archaeopteryx: shares both bird & reptile features– Basilosaurus: early whale with tiny hind legs– Tiktaalik: early fish with legs

• Evidence Conclusion : Indicates common ancestry

• Defined: similar body structures with very different functions

• Different environments lead to adaptations– Ex: The forelimbs of animals

• Evidence Conclusion : Indicates common ancestry

• Defined: Organs which have lost most or all their original function

• Vestigial Human Parts:– Gill slits = once used to breath oxygen in water– Yolk sac = once used to nourish developing embryo– Appendix = once used to digest plants

• Evidence Conclusion : Indicates common ancestry

Vestigial Structures

Human Embryo w/ Vestigial Structures

Snake femurs (leg bones) are vestigial

Pelvic bones of whales are vestigial

Nictitating membrane is vestigial in humans

• DNA, proteins, & amino acids compared

• More related species have more similar chemistry

• Evidence Conclusion : Indicates common ancestry

• Different species show similar development

• Different body plans become noticeable later in development

• Evidence Conclusion : Indicates common ancestry

• Antibiotics: chemicals designed to kill bacteria

• Antibiotic Resistance: Bacteria are adapting to the use of antibiotics– Example of natural

selection– Importance: Bacteria

infections are becoming harder to treatFungus

Bacteria

No bacteria

Antibiotic Resistance

GoodBad

• Pesticides: Chemicals designed to kill pests (rodents, insects)

• Pesticide Resistance: pests are adapting to the use of pesticides– Example of natural selection– Importance: Crops are being destroyed by pests

Topic 4: Speciation

Speciation• Defined: evolution of a new

species• Species: group of

organisms that can interbreed and produce fertile offspring

• Factors that lead to evolution– Natural Selection– Gene flow– Mutations– Sexual selection– Genetic drift

Gene Flow

• Defined: Movement of genes from 1 population to another

• Increases variations in a population (new genes introduced)

• If gene flow prevented– No variations exchanged– Populations isolated– Organisms adapt to their own environment

Genetic Drift

• Defined: Changes in gene pool due to chance (not natural selection)

• More likely in smaller populations• Ex: Natural disaster

– Pre-forest fire (left picture): Blue is more advantageous– Post-forest fire (right picture): Due to more red survivors, red has the

advantage to reproduce– Survival unrelated to adaptations; Random

Geographic Isolation

• Mountains, rivers, canyons, oceans may separate a population– Gene flow stopped

• Each population adapts to its isolated environment

• Over time, genetic differences accumulate between the groups

Behavioral Isolation

• Gene flow prevented due to different mating rituals

• Populations unable to reproduce• Differences accumulate between both groups

Temporal Isolation• Gene flow prevented

due to time interference–1) Mate at different

seasons–2) Some active at

night (nocturnal)• Differences

accumulate between both groups

Topic 5: Patterns in Evolution

Divergent Evolution

• Defined: closely related species become increasingly different

• Cause: Different environments• Ex: Red fox (forest) vs. Kit fox (desert)

Convergent Evolution

• Defined: different species evolve similar traits due to similar habitats

• Survival advantage to a particular environment • Ex: Tuna (fish) and dolphins (mammals)

– Unrelated species with a similar environment (ocean)– Faced similar evolutionary pressures

Coevolution

• Defined: 2 or more species evolve in response to changes in each other

• Ex: Plants and Insects– Plants: provide insects with nectar– Insect: transfers pollen from one plant to another

How Fast Does Evolution Occur?

• No exact time frame• Gradualism: slow & steady change of 1 species into another

– Small changes continually build• Punctuated Equilibrium: Rapid periods of evolution

– Due to sudden environment change– Ex: Mammal diversity exploded after dinosaur extinction

• Examples of both models exist