Objectives:

• Define Spontaneous Generation and list some observations that led people to believe this way.

• Summarize the experiments performed by Redi and Spallanzani that tested the idea of spontaneous generation.

• Discuss how Pasteur’s experiment disproved the hypothesis of spontaneous generation.

Theory that life only comes from other life.

• Hypothesis that living matter could arise from nonliving matter.• Fish could appear from mud

• Flies appear from meat

Italian Scientist, 1668

Control Group Experimental Group

Open Jar with pieces of meat in it

Cheesecloth covered jar with pieces of meat in it

Flies and maggots on the meat and in the jar

Flies around the jar, but no flies or maggots in the jar or on the meat

Redi proved that flies come from eggs laid by other flies. He did not disprove spontaneous generation.

Italian Scientist, early 1700’s

Control Group Experimental Group

Boiled broth in an open flask

Boiled broth in a flask then immediately sealed the flask shut

Broth became cloudy after a few days

Broth remained clear

Spallanzani proved that living microorganisms could not grow from the broth if air could not get to it.

• The use of microscopes greatly aided Spallanzani, his work was not possible without a microscope or knowledge of microorganisms.

• Critics claimed that Spallanzani killed the “vital life force” of the air.

French Scientist, Mid to Late 1800’s• Best known for Pasteurization - Process by which food items are heated to kill the majority of the bacteria. Most widely associated with dairy products.

• The Paris Academy of Science offered a prize for anyone that could settle the controversy over spontaneous generation versus biogenesis once and for all.

Pasteur used a gooseneck flask, he boiled broth inside the flask, the flask WAS NOT sealed. Pasteur left the flask sit for a period of one year, the broth was still clear. After a year Pasteur broke the neck off the flask, the broth turned cloudy in a short period of time. This was enough to convince the Paris Academy of Science, Pasteur won their contest.

For more information on Spontaneous Generation and the work of Redi, Spallanzani and Pasteur visit the website http://mail.usf.edu/~spnichol/spont_gen.html

Read section 14-1 and complete Questions 1-6 on page 263 Due Wednesday

Quiz on Section 14-1 Friday

Objectives:

• Outline the modern scientific understanding about the formation of the Earth.

• Define half-life and summarize its use.

• Discuss Oparin’s hypothesis

• Describe the Miller-Urey apparatus and the experiments completed with it.

• Summarize the importance of cell-like structures created in the lab.

•3.8 – 3.9 Billion years ago the Earth cooled enough for the Oceans to form.

• 3.9 Billion years ago the oldest known rocks were formed.

• 3.5 Billion years ago the oldest known fossils formed.

• 1.8 Million years ago the first human- ancestors arose.

• 5 Billion years ago the solar system formed from a swirling mass of dust and gasses.

• The sun formed and started burning a few million years after the solar system was formed.

• 4.6 Billion years ago the Earth started to form from a collection of space debris.

•Relative age dating determining the age of rock units with respect of one another.

It is a ballpark age, not exact, based on the position within the rock layer.

•Absolute age dating is determining a numerical age of a rock unit using different laboratory techniques.

It is an accurate age based on Science.

Radioactive Dating – method of determining the age of a material based on the half-life of elements within it.

Isotopes – Atoms of the same element that have different numbers of Neutrons.

Mass number – The total number of Protons plus Neutrons within an element.

Radioisotopes – radioactive isotopes, they release radiant energy or particles from their nucleus.

Element – The simplest form of a substance.

Subatomic particles

Protons + charge

Neutrons no charge

Electrons – charge

Atomic Number – The number of Protons, also the number of Electrons.

• Radioactive Dating - Using the half-life of various radioisotopes to determine the age of a material.

• Half-life is the length of time it takes for ½ of a substance to decay.

• Different radioisotopes have different rates of decay, therefore they have different half-lives.

• The half-life may be a fraction of a second or billions of years.

Radioactive Dating Methods:

Isotope Half-life

Carbon-14

C-14

5730 years

Potassium-40

K-40

1300000000 years

Uranium-238

U-238

4500000000 years

• C-14 is used only for Organic matter, and useful only to about 50000 years.

Alexander I Oparin - Soviet Scientist – 1923

Developed a hypothesis on how life was formed on Earth.

Used works from other scientists to develop his idea and NEVER tested it

First Oparin hypothesized that the Earth’s early atmosphere was different than today. The atmosphere contained Ammonia (NH3), Hydrogen Gas (H2), Water Vapor (H2O) and compounds containing Hydrogen and Carbon such as methane (CH4)

Oparin thought that the temperature of the early atmosphere was above the boiling point of water. At these temperatures the components of the early atmosphere may recombine to form simple organic compounds.

Next Oparin hypothesized that these simple organic compounds would fall to the Earth in the rain after the Earth cooled enough for water to condense. These simple organic molecules would collect and be concentrated in the primordial oceans.

Due to random chance alone these simple organic molecules would combine together to form complex organic compounds.

Thirdly Oparin thought that these Complex Organic molecules must somehow become concentrated and enclosed in a membrane.

Finally Oparin hypothesized that these concentrated and enclosed structures must be linked to essential biochemical pathways such as reproduction and respiration.

4 Essential Developments for the Creation of Life

1. Formation of simple Organic Compounds

2. Formation of Complex Organic Compounds

3. Concentration and Enclosure of these Compounds

4. Linkage to Vital Biochemical Pathways

Stanley Miller – Harold UreyAmericans1950’s

1st LIFEUnicellular, Prokaryotic, Asexual, Heterotrophs (got food from primordial soup), Anaerobic

Some turned to PredationSome turned to Photosynthesis(created O2)

Eukaryotic cells arose – Theory of Endosymbiosis

Aerobic Respiration

Multicellular

Microspheres Page 268 Coacervates

Growth

Organization

Reproduction

Membrane-like boundry

Linkage to Biochemical Pathways

1st Life - Prokaryotic, Unicellular, Asexual, Heterotroph, AnaerobicClosely resembled modern day Archaebacteria

Some turned to predation – Endosymbiotic Theory – EukaryotesSome turned to photosynthesis – Created O2 – In atmosphere created O3 –

The presence of Oxygen allowed some organisms to become Aerobic – Allowed Multicellular organisms to arise.

Microspheres Page 268 Coacervates

NO Growth YES

YES Organization NO

YES Reproduction NO

YES Membrane like boundary

YES

NO Linkage to Biochemical Pathways

NO