Origin of LifeOrigin of Life

Theories

Spontaneous Generation(abiogenesis)- life comes from nonliving material

Biogenesis- - life only comes from other living things.

Important Experiments

Francesco Redi – disproved that – disproved that maggots came from dead organismsmaggots came from dead organisms

Miller and Urey - early atmosphere had very little

oxygen - used to create organic compounds

(amino acids)

Louis Pasteur – completely disproved spontaneous generation

Lamark’s Explanation

a. believed that traits were a. believed that traits were “acquired” and not “acquired” and not determined by genesdetermined by genes

b. traits were results from b. traits were results from organisms experiences or organisms experiences or behaviorbehavior

c. “necks of giraffes”c. “necks of giraffes”

Charles Darwin’s Theory of Evolution

Galapagos IslandsGalapagos Islands

a. Darwin’s finchesa. Darwin’s finches

Origin of Species by Natural Selection – by Charles Darwin – by Charles Darwin

EvolutionEvolution – concept that species – concept that species

have changed over timehave changed over time

Natural Selection““organisms organisms best suited to their environment to their environment reproduce more successfullyreproduce more successfully than other than other organisms”organisms”

1. Adaptation 1. Adaptation 2. Competition2. Competition

*selection conditions change as the demands of *selection conditions change as the demands of the environment changethe environment change

*if change is too extreme and organism can’t *if change is too extreme and organism can’t change, they become extinct or diechange, they become extinct or die

Patterns of Evolution Genetic Drift – the alteration of allele – the alteration of allele

frequencies by chance eventsfrequencies by chance events

Punctuated Equilibrium – speciation occurs – speciation occurs during brief periods of rapid genetic change during brief periods of rapid genetic change

Divergent Evolution – two or more – two or more related populations or species become related populations or species become more and more dissimilarmore and more dissimilar

- domestic dogs- domestic dogs

Convergent Evolution – 2 organisms – 2 organisms seem to be similar but are not at allseem to be similar but are not at all

- shark and porpoise- shark and porpoise

Co-Evolution – 2 species evolve together – 2 species evolve together

- plants and the animals that pollinate - plants and the animals that pollinate themthem

Types of Natural Selection

3 types3 types

1. stabilizing selection1. stabilizing selection

2. directional selection2. directional selection

3. disruptive selection3. disruptive selection

Stabilizing Selection - individuals with the AVERAGE form of a trait have the highest fitness - most common

Directional Selection - individuals that display a more extreme form of a trait have a greater

fitness then those with an average form of trait - one extreme > average

Disruptive Selection - individuals with either extreme of a trait have a greater fitness than those with a average form - either extreme > average

Evidence of Evidence of EvolutionEvolution

Evidence from Living Organisms

Homologous and Analogous Structures

a. a. Homologous – – similar features that similar features that

originated in a originated in a shared/common shared/common

ancestorancestor

b.b. Analogous- - features serve features serve identical functions identical functions and look somewhat and look somewhat alikealike

Vestigial Organs

“ “useless features”useless features”

a. appendixa. appendix

b. human tailboneb. human tailbone

Evolutionary Evidence

- similar DNA, homologous features, - similar DNA, homologous features,

vestigial structuresvestigial structures

Biochemical Evidence

- similar amino acid sequence- similar amino acid sequence

DNA and Chemical Studies

a. human and chimp DNA – very a. human and chimp DNA – very similarsimilar

Embryo studies

a. all vertebrae embryos are similar a. all vertebrae embryos are similar at 4 weeksat 4 weeks

b. all vertebrates have gill slits at 4 b. all vertebrates have gill slits at 4 weeksweeks