Evolution UnitNotes #1: The Earth’s History
Origins of Life
• “The proper scene for the slow brewing of life from nonlife was the early Earth. The Earth’s conditions favored certain chemical combinations over others, and with the passage of time a direction was set.” ▫ Lynn Margulis and Dorion Sagan, 1993
Spontaneous Generation & Vital Force• Spontaneous generation: early idea that life
could be produce from non-living substances using vital force
• Vital force: an invisible substance in the air that could give rise to new life from the nonliving world
3 Experiments for vital force:
1) Redi – do flies come from meat?2) Spallanzani – does vital force produce
life in water (straight necked flask)?3) Pasteur – does vital force produce life in
water (curved necked flask)?
The Early Earth
Measuring the Earth’s Age
Radiometric Dating = calculating the age of an object by measuring proportions of radioactive isotopes
Radioactive Isotope = an unstable form of an element that decays into simpler elements and gives off energy (radiation)Ex/ Carbon-14 decays into Nitrogen & Potassium-40 decays into Argon-40Half-life = the amount of time it takes for one half of a given radioactive isotope to decay (specific to the substance)Potassium 40
Half-life = 1.3 billion years
Argon 40
~4.54 billion years old
So how did life begin? (take 2)Spontaneous Origin
Spontaneous Origin = the process of life developing from non-living chemical interactions
1) Simple Organic molecules were formed in the atmosphere. (Ammonia, Methane, Hydrogen gas, Water, but NO Oxygen gas)2) Sun light, volcanic heat, lightning, etc energized the molecules creating larger and more complex substances.
The first building blocks of life became available
Testing the idea:
1920 – Oparin & Haldane suggest early atmosphere contained organic molecules & lacked oxygen1953 – Miller & Urey test the primordial soup model
Prokaryotes, the oldest organisms
Scientists study fossils to discover clue of what early life was like
Fossils = mineralized bone, tooth, shell or imprints of organisms
The oldest fossils are microscopic and date 3.5 billion years old from Australia
Early prokaryotes survived without oxygen, in fact oxygen was toxic to some.Cyanobacteria were some of the first
prokaryotes to show and they were photosynthetic
Cyanobacteria began adding oxygen to the atmosphere through photosynthesisToday 21% of the Earth’s atmosphere is oxygen
Eukaryotes from Prokaryotes
Eukaryotes show up in the fossil record 1.5 billion years ago
The Theory of Endosymbiosis
One of the main differences between prokaryotes and eukaryotes= Mitochondria & Chloroplasts
Proposes that these organelles are the descendents of symbiotic, aerobic eubacteria.
Later a photosynthetic prokaryote entered a symbiotic relationship with a larger cell
The larger host cell would gain protection from toxic oxygen
Supporting Evidence: Both organelles contain their own circular DNA and can replicate on their own.
Vocab• Take a sheet of paper and
fold into 3 columns.• Column 1: Vocab Word• Column 2: Definition in 8
words or less.• Column 3: Picture
▫ If there is no picture.▫ Draw an example or▫ Draw something that
relates.
• TODAY’S VOCAB (DUE TUES)
• Biogenesis• Spontaneous Generation• Isotope• Atom• Microspheres • Coacervates• Radiometric dating
HW:
•Get an 8.5 x 11 inch 3 subject notebook.•Go on Mr. E’s website at
www.losal.org/lahs and use instructions to make a cover page for Unit 8.▫Due Thursday
Read p282 – 286 answer #1-5 on p.286