EvolutionChapters 14-17

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Biogenesis – “life” “creation”All living things come from other living things

HistorySpontaneous GenerationLiving things could arise from non-living things

Francesco Redi Jars with Meat

One open, one with netting Found maggots on open one

If spontaneous Generation was TRUE, there should have been maggots on both.

New Spontaneous Generation: only simple things come from non-living things

HistoryLazzaro Spallanzani

Boiled Broth, Sealed it Found NO lifeIf New Sponanteous Generation was true, there

should have been bacteria or mold in the broth. Critics said he killed the ‘vital force’ in the air so

life couldn’t start Vital Force – something in the air that made simple

life

HistoryLouis Pastuer

Made a special curved flask that would let in ‘vital force’ but not germs Found NO life Broke flask, then it spoiled.

FINALLY DISPROVED Spontaneous Generation!

So if all living things come from other living things, where did the first living thing come from?

All religions try to explain this in their own way

History of EarthEarth is about 4.6 billion years old

(4,600,000,000)Life about 3.5 billion years old

(3,500,000,000)How do we know?Radioactive Dating:

Studying the chemical make up of an object to determine its age.

Before we can understand how to date something we need to get radioactivity

(How do we know how old Earth is?)Radioactivity(The over stuffed closet)

Something is radioactive if it has too much energy or particles stored in one place.

It decays when it spontaneously releases the extra.

Often changing an atom from one element to a different one.

University lecture with G counterSpitting out the extra

Radioactive DecayElements that decay do so regularly

Carbon-14: 5715yearsThorium-230: 75,000 yearsPotassium-40: 1,300,000 yearsUranium-238: 4,500,000 yrs

Half Life: The amount of time it takes for half the element in a thing to decay.Carbon-14

# of Half lives

Fraction left

Fraction gone

Age

1 1/2 1/2 5715

2 1/4 3/4 11430

3 1/8 7/8 17145

4 1/16 15/16 22860

Example Half Life Problem:I found a fossil! It’s the skull of a

weird animal. I took it to a lab and they said it had 1/16th of the carbon left. How old is it?What element am I using?

Carbon-14What is its half life? 5715 yearsWhat fraction is left? 1/16th

How many half lives have past? 4 Go to chart and figure out how many

half lives have past.Multiply the elements half life

(that you look up) with the number of half lives that have occurred? 5715 X 4 = 22860years old

Element Half LifeCarbon-14 5715 years

Thorium-230 75,000 years

Potassium-40 1,300,000,000 yrs

Uranium-238 4,500,000,000 yrs

Cesium-137 30 years

Sodium-25 60 SECONDS

Radon-219 4 SECONDS

Barium-140 12.7 DAYS

Nitrogen-13 10 MINUTES

Selenium-83 25 MINUTES

Hydrogen-3 12.4 years

Iodine-131 8.1 DAYS

Strontium-90 87.3 years

Back to the History of EarthEarly Atmosphere composed of ammonia NH4,

Hydrogen H2, Water Vapor H2O, and methane CH4

Since the Earth was still very hot from the friction caused by rocks hitting it, the temperature would have been above the boiling point of water

Alexander Oparin 1923 said this but NEVER TESTED IT!

Stanley Miller and Harold Urey DID test it in 1953 and found that using electricity (like lightning) would make amino acids and simple pieces of DNA

Miller and Urey Apparatus

History of Earth

Its also possible that some organic compounds came from “Aliens” or meteorites hitting the Earth

These compounds could clump together and form microspheres and coaccervates

Microspheres and coaccervates have the ability to absorb materials from around them and split into smaller ones.

If DNA or RNA got trapped in these and helped it to do better than others without the DNA, primitive life has begun.

LifeIn order to be considered living, an organism

needs to pass on their traits – through DNA or RNA

Simplest Life forms are archaebacteria Prokaryotic – no nucleus Heterotrophic – can not make their own food Anaerobic – do not use oxygen

Eventually all the ‘food’ would be eaten so how will they survive? EVOLUTION

Evolution occurs when organisms with certain characteristics do better then others; do better means have more babies, which means they pass on more genes.

Think about itGiraffes feed on trees. If a giraffe has the genes

that say ‘be short’ will it survive? Will it make babies? Will the gene that says ‘be short’ survive?

Can a giraffe stretch out his neck and make it stay that way? Maybe. Can that giraffe pass that on to his kids? NO WAY

What if that short giraffe started eating apples found on the ground? Would he survive? Would being short be helpful? Would those genes be passed on? NEW SPECIES

Does that new species have anything to do with the old one?

Review! Test TomorrowWhere does life come from?

Other living things BIOGENISIS

What did people used to think life cam from? Came out of the mud or swamp gases SPONTANEOUS GENERATION

What did Frank Redi do? Tried to disprove Spontaneous generation with fly

experiment Made ‘new’ spontaneous generation

What did L. Spallinzanni do? Tried to disprove Spontaneous generation with

broth and sealed flasks but created a ‘VITAL FORCE” argument

Who finally disproved spontaneous generation? Louis Pasteur S-neck flask

How old is Earth? 4.6 billion years

How do we know? Radioactive dating of isotopes

What is an isotope? An atom with too much stuff packed in

What is radioactivity? When the stuff comes flying out and changes into

something else

What is the half life of an element? The time it takes for ½ of the element in a sample to

decay

What is decay? Spit out the extra

Where do I find half lives? Have to look it up

If 1/16th of an element remains, how many half lives have past?

4

If 1/16th of carbon remains in a sample how old is it?

4 x 5730 = 22,920

If I have a sample of carbon-14 that is 10g and let it sit for 5730 years, how much mass of carbon-14 will be left?

5 grams

What was the early earth’s atmosphere made of?

CO2, H2O, NH4, CH4

What was the temperature of the early earth? Over boiling

Who figured these particles were in the atmosphere?

Oparin

Who tested this hypothesis? Miller and Urey

What did Miller and Urey find? The beginnings of more complex molecules Coaccervates and microspheres

Where else could these compounds have come from?

Meteorites

How did the first life eat? Heterotrophic

What did the first life look like? Simple, no nucleus, or organelles, prokaryotic

Did they use Oxygen? None there yet

Once all the food was gone what happened next?

The organisms who could make their own food did better and evolved

What is evolution? Making the most babies and passing on your genes.