10.1 early ideas about evolution. spontaneous generation – living things could come from nonliving...

10.1 Early Ideas About Evolution


• Spontaneous Generation – living things could come from nonliving things

• Biogenesis – all living things come from other living things


• 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


ControlExperimental A:Independent Variable - cork

Experimental B:Independent Variable - net


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


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


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


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


Evolution is biological change over time

• A species is a group of organisms that can reproduce and have fertile offspring.


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


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



• 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


• 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.



• 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



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


• 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


• 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


• 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



• Anatomy provides evidence of evolution.

Human hand Bat wingMole foot

– Homologous structures are similar in structure but different in function


10.1 Early Ideas About EvolutionHuman hand

Bat wing

Mole foot

Fly wing

– Analogous structures – similar function but different structure



• 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


10.1 Early Ideas About Evolution10.4 Evidence of 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


1. Stabilizing selection favors the average phenotype

10.3 Theory of Natural Selection11.2 Natural Selection in Populations


2. Directional selection favors phenotypes at one extreme



3. Disruptive selection favors both extreme phenotypes



• 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


• Divergent evolution – 2 or more related populations become more dissimilar– Response to different environments/habitats

ancestor

red foxkit fox



Coevolution – change of 2 or more species in close association with each

– occur in beneficial and competitive relationships.



Extinction is the elimination of a species from Earth.



• 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



• 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


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.

10.1 early ideas about evolution. spontaneous generation – living things could come from nonliving...

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