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 of
Natural Selection
• Four factors:
1) Overpopulation: more offspring are born than can
survive
2) Variation: individuals of a population have
differences
3) Adaptation: Some variations allow better survival
4) 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
Dinosaurs extinct
Land animals
Fish (first vertebrates)
Apes
Dinosaurs appear
Amniotic egg
Land plants & fungi
Multicellular plants
Outside links
Link 1
Link 2
Unicellular
eukaryotes
Scale:
1 minute = 3 million years
Land prokaryotes
(LUCA)
prokaryotes
24 Hour Life Timeline
• 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
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
Bacteria
No bacteria
Fungus
• 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
treat
Antibiotic Resistance
Bad
Good
• 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