Download theory (casual usage of the word) vs. scientific theory

theory
(casual usage of the word)
vs. scientific theory
theory- guess
scientific theory- an explanation of a natural
phenomenon supported by a large body of
scientific evidence obtained from various
investigations and observations.
• Germ Theory of Disease- a specific disease is
caused by a specific type of microorganism.
– The germ theory of disease is considered by many to be
one of the most important contributions to science and
medicine (if not THE most important)
– Before the work of Van Leeuwenhoek, Pasteur, Koch, and
others, most doctors believed that diseases were caused
by SPONTANEOUS GENERATION- that is, infections
arose from nonliving material.
– Since it was believed that microorganisms could arise
from nonliving substances, scientists and doctors of that
time saw no purpose in trying to discover ways to prevent
diseases.
– In fact, before the germ theory was proposed, doctors
would actually perform autopsies on people who died of
an infectious disease and then go care for patients
WITHOUT WASHING THEIR HANDS IN BETWEEN, not
realizing that they were actually transmitting the disease
themselves!
• Atomic Theory– Even today after hundreds of years of
research, no one has yet seen a single atom.
– How can we then be certain that atoms exist?
– Tested by experimentation• Dalton’s atom
• Thompson’s atom
• Rutherford’s atom
• Bohr’s atom
• Current electron cloud model.
• How did life begin? (pgs 8-14)
– Spontaneous generation theory- fully
formed LIFE could come from NONLIVING
matter
Recipes for living things– fishdried mud
– mosquitoes water
– moths old clothes
– flies meat
• Francesco Redi- 1668 (pgs. 8-9)
• Lazzaro Spallanzani 1700’s (pg. 11)
• Louis Pasteur- 1864 (pgs.12-13)
he proved BIOGENESIS-
new organisms come from
existing organisms
• Life does not arise from NON-LIVING
things. (BIOGENESIS!!)
• If life comes only from life, then how did
life on Earth first begin?
(question from page 423 in your bio. book)
• Life does not come from non-life
(chemicals) today but it could have under
the conditions of the early earth.
Formation of the Earth to multi-cellular life
– Big Bang- universe expanding, galaxies are moving apart, like
raisins in a loaf of raisin bread! (pg. 423)
– Swirling mass of gas and dust
– Collapsing in to form the sun (evolution of a star)
– Collected as clumps to form the planets-more dense elements
to core, less dense to crust, even less dense to form
atmosphere
– Earth 4.6 billion years old
– About 3.8 bya the surface cooled enough for the oceans to
form
– 3.5 bya 1st fossil evidence of prokaryotic life
– 1 bya 1st fossil evidence of eukaryotic life (pg 427 endosymbiotic theory)
– Sexual reproduction arises and SPEEDS up the evolutionary
process! Leads to much more variation!! (pg. 428)
– A few hundred million years after sexual repro. evolved we
begin to see the fossil evidence of MULTICELLULAR life forms.
galaxies are identified in 2D images (right), then have their distance determined from
their spectrum to create a 2 billion light-years deep 3D map (left) where each galaxy
is shown as a single point, the color representing the luminosity - this shows only
those 66,976 our of 205,443 galaxies in the map that lie near the plane of Earth's
equator.
• First organic molecules-leading to the first life forms
– Primordial Soup
1. simple compounds like AMINO ACIDS- can these form
from what was believed to be present on the early earth?
YES!
» Oparin’s Hypothesis- NH3 ammonia, H2 hydrogen gas, H2O
water vapor, and CH4 methane
» other substances-HCN hydrogen cyanide, CO2 carbon dioxide,
CO carbon monoxide, H2S hydrogen sulfide
» Miller and Urey experiment (pg. 424) formation of amino acids,
ATP (an energy molecule) and DNA nucleotides!!
2. Complex compounds formed like PROTEINS (amino acids
link together to make proteins) YES!
3. concentration and enclosure- cluster together (pg. 425) YES!
4. clusters grow, reproduce and metabolize CAN’T GET THIS!!