topic 1: origins of life origin of the solar system earth is estimated to be ~4.6byo –radiometric...
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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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Outside linksLink 1Link 2
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