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10.1 Early Ideas About Evolution
10.1 Early Ideas About Evolution
• Spontaneous Generation – living things could come from nonliving things
• Biogenesis – all living things come from other living things
10.1 Early Ideas About Evolution
• Observation– Tiny wormlike maggots turned into sturdy oval cases,
from which flies eventually emerge
• Francesco Redi – questioned the belief that flies were generated spontaneously from rotting meat
• Experimental Group – jars with nets over them that contained meat inside– Netting allowed air to enter but not flies
• Control Group – uncovered jars with meat inside
• Result – maggots swarmed over the meat in the open jars while the experimental remained maggot free
10.1 Early Ideas About Evolution
ControlExperimental A:Independent Variable - cork
Experimental B:Independent Variable - net
10.1 Early Ideas About Evolution
Hypothesis – microorganisms form not from air but from other microorganisms
Spallanzani
•Experiment – boiled broth in a flask to kill all microorganisms in it
•Experimental Group – boiled then sealed flask
•Control Group – boiled then left open
•Result – sealed flask remained clear and free of microorganisms; open flasks became cloudy
*Disagreed – heated the flasks too long, killing the
“vital force” in the air inside the flask
10.1 Early Ideas About Evolution
Louis Pasteur – Made a goose-neck flask that prevented solid particles from entering but allowed air
– – remained clear for up to a year – he broke the neck off & the remained clear for up to a year – he broke the neck off & the broth became cloudybroth became cloudy
10.1 Early Ideas About Evolution
Fossil – trace of a long dead organism
• Found in sedimentary rock – deposited by wind & water• Develop from hard body parts• Overtime hard minerals replace the tissue leaving
rocklike structures
• Mold – imprint in the rock in the shape of the organism• Cast – mold has been filled with hard minerals making a
rocklike model
10.1 Early Ideas About Evolution
Distribution of Fossils
• Law of Superposition – successive layers of rock or soil were deposited on top of one another by wind or water
• Lowest stratum (rock layer) is the oldest
• Relative age – using law of superposition to figure out the age of one fossil compared to another
10.1 Early Ideas About Evolution
Evolution is biological change over time
• A species is a group of organisms that can reproduce and have fertile offspring.
10.1 Early Ideas About Evolution
Naturalist – collect specimens and keep careful records of observations
Lamarck: Similar species descended from a common ancestor– Acquired Trait – trait not determined by genes but by
experience or behavior– Believed acquired traits could be passed down
10.2 Darwin’s Observations
10.1 Early Ideas About Evolution
Charles Darwin
• Born 1802• Originally studied medicine at Edinburgh University
– Hated the sight of blood– later switched to Theology (Divinity)
Faith waivered after encountering the evils of slavery on his travels
• 1931 H.M.S. Beagle• 5-year mapping and collecting expedition to South
America and South Pacific
10.2 Darwin’s Observations
10.1 Early Ideas About Evolution
10.1 Early Ideas About Evolution
• Worked on his theories for 20 years• Married his first cousin
– 9 children – 3 died in childhood• Died 1882• February 12th is Darwin Day• Did not say “Survival of the Fittest”
– Herbert Spencer 1864
10.1 Early Ideas About Evolution
• Variation is a difference in a physical trait.– Galápagos tortoises that live in areas with tall plants have
long necks and legs.– Galápagos finches that live in areas with hard-shelled nuts
have strong beaks.
10.2 Darwin’s Observations
10.1 Early Ideas About Evolution
• An adaptation is a feature that allow an organism to better survive in its environment.– Adaptations can lead to genetic change in a population.– The change in genetic makeup of the population is
evolution
10.2 Darwin’s Observations
10.1 Early Ideas About Evolution
Darwin’s Theories
• Descent with Modification – newer forms appearing in the fossil record are actually the modified descendants of older species
• Natural Selection – Organisms with favorable traits survive, reproduce, and pass the variations to the next generation
10.3 Theory of Natural Selection
10.1 Early Ideas About Evolution
• Artificial selection is the process by which humans select traits through breeding.
neck feathers
crop
tail feathers
10.3 Theory of Natural Selection10.4 Evidence of Evolution10.3 Theory of Natural Selection
10.1 Early Ideas About Evolution
• The study of geography provides evidence of evolution.
– Island species most closely resemble nearest mainland species– Populations can show variation from one island to another
Biogeography - Study of the distribution of organisms around the world.
10.3 Theory of Natural Selection10.4 Evidence of Evolution
10.1 Early Ideas About Evolution
• Embryology provides evidence of evolution.
Larva
Adult barnacleAdult crab
– Identical larvae = different adult body forms– Similarites in Biochemistry: DNA, RNA, ATP– Embryos of Vertebrates and gill slits
10.3 Theory of Natural Selection10.4 Evidence of Evolution
10.1 Early Ideas About Evolution
10.1 Early Ideas About Evolution
• Anatomy provides evidence of evolution.
Human hand Bat wingMole foot
– Homologous structures are similar in structure but different in function
10.3 Theory of Natural Selection10.4 Evidence of Evolution
10.1 Early Ideas About EvolutionHuman hand
Bat wing
Mole foot
Fly wing
– Analogous structures – similar function but different structure
10.3 Theory of Natural Selection10.4 Evidence of Evolution
10.1 Early Ideas About Evolution
• Ostrich wings are examples of vestigial structures
Vestigial structures are remnants of organs or structures that had a function in an early ancestor but no longer have a function
10.3 Theory of Natural Selection10.4 Evidence of Evolution
10.1 Early Ideas About Evolution10.4 Evidence of Evolution
10.1 Early Ideas About Evolution
Normal Distribution – Frequency is highest near the average and decreases toward each extreme end of the range
• Natural selection can change the distribution of a trait in one of three ways
11.2 Natural Selection in Populations
10.1 Early Ideas About Evolution
1. Stabilizing selection favors the average phenotype
10.3 Theory of Natural Selection11.2 Natural Selection in Populations
10.1 Early Ideas About Evolution
2. Directional selection favors phenotypes at one extreme
10.3 Theory of Natural Selection11.2 Natural Selection in Populations
10.1 Early Ideas About Evolution
3. Disruptive selection favors both extreme phenotypes
10.3 Theory of Natural Selection11.2 Natural Selection in Populations
10.1 Early Ideas About Evolution
• Convergent evolution – Change toward similar characteristics in unrelated species
• Different species adapt to similar environments.
• Ex: Aquatic organisms
10.3 Theory of Natural Selection11.6 Patterns in Evolution
10.1 Early Ideas About Evolution
• Divergent evolution – 2 or more related populations become more dissimilar– Response to different environments/habitats
ancestor
red foxkit fox
10.3 Theory of Natural Selection11.6 Patterns in Evolution
10.1 Early Ideas About Evolution
Coevolution – change of 2 or more species in close association with each
– occur in beneficial and competitive relationships.
10.3 Theory of Natural Selection11.6 Patterns in Evolution
10.1 Early Ideas About Evolution
Extinction is the elimination of a species from Earth.
10.3 Theory of Natural Selection11.6 Patterns in Evolution
10.1 Early Ideas About Evolution
• Mass extinctions are rare
– destroy many species at global level– thought to be caused by catastrophic events– at least five mass extinctions in last 600 million years
10.3 Theory of Natural Selection11.6 Patterns in Evolution
10.1 Early Ideas About Evolution
• Adaptive radiation – The diversification of one ancestral species into many species.
– descendent species usually adapted to wide range ofenvironments
10.4 Evidence of Evolution11.6 Patterns in Evolution
10.1 Early Ideas About Evolution
Punctuated Equilibrium
• A repeating pattern in the history of life• Reflected in the fossil record• Shows bursts of evolutionary activity that are followed by
long periods of stability.