How the Earth formed

• About 4.5 billion years ago• From a cloud of gas and dust

(nebula) that also formed the Sun and other planets and comets and asteroids…

• “chunks” stuck together, which attracted more chunks,

which stuck and attracted more chunks…

How the Earth formed

• Kept getting hit with meteors (bombardment), volcanic eruptions

• Atmosphere not like today ammonia (NH3), hydrogen sulfide gas (H2S), water vapor and methane (CH4), carbon dioxide (CO2)

Miller and Urey (1950’s)• Proposed that these simple atmospheric

molecules at high temperatures (e.g. lightning) could form amino acids

• Comets/meteorites also have traces of amino acids

First living things• About 3 billion years ago• Simple, one celled, autotrophic prokaryotes• Chemosynthesis: use chemicals to make

energy• Some species still around today, at bottom

of ocean by volcano vents (Archaea) • Cyanobacteria

– Took CO2 out of atmosphere and release O2. – Responsible for our atmosphere today

• Eventually one may have been swallowed by another and survived inside to make

eukaryotes (endosymbiosis)

Spontaneous generation

• Stated that nonliving things could turn into living things (mice from wheat/cloth)

• Remember that in the 17th century (and earlier) not everyone was educated

• Biogenesis: living things can only come from living things…what we believe now

Hutton• People believed Earth

about 6000 years old (biblical account)

• James Hutton: noticed rock layers in mountains were bent/folded, but were flat when formed

• So forces inside the Earth must have done that, but it would take longer than 6000 years

• Deep-time…things happened much farther back in time than we thought

Lyell• Said that the processes going on

today, geologically, were going on back then, too

• Called Uniformitarianism• Was a competing theory (Cuvier)

called catastrophism where big geological events happened and species became extinct

Jean Baptiste Lamarck• Believed in spontaneous generation, and

that simple things could become more complex in their life time

• Organisms change over life-time (acquired traits)

• Pass that on to children

• Inheritance of acquired characteristics

Jean Baptiste Lamarck

Charles Darwin• And Alfred Russel Wallace

(Darwin published book first)• Noticed differences between

finch (bird) species as traveled by ship around the world (HMS Beagle, Galpagos Islands)

•Descent with modification– Traits passed on to children over

time

Charles Darwin

Comparing Lamarck

and Darwin

4 Parts of the Theory• Struggle for existence: nature produces

more offspring than can survive at one time. Competition for resources (food, water, space, etc.).

• Variation/Adaptation: genetic differences in a population. (adaptations)

• Survival of the Fittest: Creatures with best adaptations survive.

• Natural selection: ones that survive reproduce more like themselves

• Note: nature (environment) “picks” what’s best…different from us picking

(artificial selection…breeding)

4 Parts of the Theory

Proof for Evolution• So over time, what a species

looks like can change• Transitional species

– Fossils of species in between modern and older set up a series

where can see changes

Transitional species

Proof for Evolution• Rocks form in flat

layers• Older ones at

bottom• Fossils in rocks

similar closer together

• Farther apart fossils are, more

different

Proof for Evolution• Embryology:

– Creatures look very similar when young– From common ancestor

Proof for Evolution• Anatomy:

– Homologous structures look alike inside and out (common ancestor, e.g.

human arms, dog legs, bird wings)– Analagous structures look the same

outside, but inside very different (evolved separately, e.g. bird wings, insect wings)

– Vestigial structures seem to serve no function, but “left over” from

ancestor (e.g. appendix, tail bone)

Structures• Homlogous

• Analogous

Structures• Vestigial

• Humans:– Muscles that

move ears– Appendix– Tonsils– Body hair– Tail bone – Wisdom teeth

Proof for Evolution• Biogeography:

– Organisms far apart look similar– Organisms close together have slight

differences

Proof for Evolution• Molecules/genetics:

– DNA and RNA sequences are incredibly similar between similar creatures

– Many genes similar between organisms