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 OriginSpontaneous 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 organismsThe oldest fossils are microscopic and date 3.5 billion years old from AustraliaEarly 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 ProkaryotesEukaryotes 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