how the earth formed about 4.5 billion years ago from a cloud of gas and dust (nebula) that also...
TRANSCRIPT
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
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
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)
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
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• 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• 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