I. How Did Life Begin?Prior to the 17th century:1. Spontaneous Generation:The belief that living things

could come from non-living things.

Francesco Redi (1668) Italian

scientist Attempted to discredit Spontaneous Generation.

Experimented to prove that maggots came from flies

Redi’s Exeriment1668 – Experiment showing how maggots come from flies

Lazzaro Spallanzani (1700)Italian scientist Experimented with spontaneous

generation of microorganisms.1. Created meat broth2. Boiled broth to kill

microorganisms3. Capped some flasks and left

others open.

Spallazani’s ExperimentOpponents of his study claimed that he overheated the samples…Destroying the VITAL FORCE

Louis Pasteur (1800’s) French scientist

*The conclusions of Pasteur, brought about the theory of

BIOGENESIS – Living things come from other living things

B. Formation Of The EarthAbout 5 billion years ago, the solar system was a mass of swirling gas and dust.

Possible result of a SUPERNOVA

As millions of years passed, a large amount of material collapsed to the center and created the sun.

Around 4.6 billion years ago, the earth and some of the other planets were formed.

As earth cooled, water vapor in the air condensed to form water and the first oceans. 3.8 to 3.9 billion years ago.

C. Measuring Earth’s AgeRadiometric dating:

Estimate the age of an object by measuring its content of radioactive isotopes.

Radioactive isotopes:Unstable and “decay” over time.Half-life:The time that it takes for a

radioactive isotope to decay by one half

D. Life On The Earth

The oldest evidence of life on the earth is found in rock estimated to be 3.5 billion years old.

The evidence shows in the form of FOSSILS.

The first fossils were referred to as MICROFOSSILS, ancient prokaryotic cells.

1. Formation of Simple Organic Compounds

A. Primordial Soup ModelAlexander Oparin (1923) • Soviet scientist• Gases of the primitive atmosphere came together and created simple organic compounds

When the atmosphere cooled and the rain fell, so did the compoundsOver time the compounds entered chemical reactions and proteins and other organic compounds resulted

* DID NOT run any experiments to support theory

-In 1953, Americans, Stanley Miller and Harold Urey, set up an experiment that was based on Oparin’s theory.

B. The Bubble ModelAmmonia and Methane were released from volcanoes into bubblesBubbles rise to the surface and burst

Formation of protein occurred either by amino acids spontaneously combining… Or they were heated in the absence of oxygen

-Similar mechanisms may have led to the formation of carbohydrates, lipids, and nucleic acids

2. Formation of Complex Organic Compounds

3. Concentration and Enclosure

Proteins clump together to form microscopic droplets…

A. Coacervates - droplets of different types of irregularly shaped molecules .

Includes Amino Acids and sugars

B. Microspheres-Round, usually from one type of molecule.Separated from the environment by a membrane Chemical reactions occur here more easily than in waterCan bud off

4. Evolution of Growth, Metabolism, and Reproduction

Coacervates and microspheres lack the complexity of living cells …

-They can grow -They can bud • They lack the ability to respond to natural selection.

5. The Role of RNA

RIBOZYME:A special type of RNA was discovered to be able to act like an enzymeThey can replicate themselvesResearch indicates life may have started with RNA

II. Evolution of Cellular Life

A. The First ProkaryotesScientists hypothesize that the first cells were: • Anaerobic• Heterotrophic• Prokaryotic

B. The First EukaryotesSome early Eukaryotes may have gone through a relationship known as SYMBIOSIS.

Endosymbiosis Theory: Prokaryotic intracellular parasites evolved into various cell organellesEvidence in the mitochondria and chloroplasts

ENDOSYMBIOSIS THEORY

Life Invaded LandCyanobacteria: photosynthesizing organisms gave off oxygen as a waste product. (At about 2.8 billion years ago) Oxygen had two effects on the environment:1) Those organism that could bond oxygen to other compounds survived

- beginning of aerobic respiration.2) Ozone (O3) was created

Lamarck’s ExplanationFrench scientist (1744-1829)Similar species descended from common ancestors

ACQUIRED TRAITS: explanation for species change.

• Changes arise from experiences and behavior over a lifetime

• Not determined by genes. EXAMPLES: web feet, giraffe neck, tails“USE and DISUSE”

Charles DarwinWent to medical schoolStudy become a ministerInterested wildlife and the environmentTook a voyage on a ship, the BEAGLE, as the boats naturalist

Darwin proposed a mechanism for evolutionNatural Selection: occurs because of ADAPTATIONSPublished a book: “On the Origin of Species” 1859, 1 year after Alfred Wallace (same basic ideas)

Evolution by Natural Selection“Human populations are able to

increase faster than the food supply can” – Thomas Malthus 1798

Only a limited number of offspring survive to reproduce

Individuals with traits that best suit their environment are most likely to survive and reproduce

Darwin’s Theories1. Descent with

modification:Newer life forms appearing

in the fossil record are modified versions of the old species

2. Modification by Natural Selection:

Mechanism for how evolution can occur.

Why some organisms survive when others do not:

The environment affects individuals differentlySome traits provide an advantagePopulations ADAPT as the proportion of favorable genes increasesFITNESS: Single organisms genetic contribution to the next generation.Favorable traits provide an ADAPTIVE ADVANTAGE

Adaptations:Inherited traits that have become

popular due to a selective advantage

Darwin’s Theory:Based on 4 major points….1. Inherited variation exists within

the genes of every population2. Some individuals are better

suited for their environments

3. Traits that provide an advantage are spread as individuals survive and have offspring

4. Fossils provide evidence that living species evolved from extinct species

The Scopes Trial

PBS VIDEO ON EVOLUTION

Darwin and Evolution

Evidence of EvolutionThe Fossil Record:Fossils:Preserved or mineralized

remains or imprints of an organism that lived long ago

Concerns with using fossils for source of evidence

The fossil record is NOT COMPLETEMany times genetic information is not available from the fossilsNot all organisms are equally likely to be fossilized

Types of Fossils Imprints

A film of carbon remains after other elements of an organism have decayed Mold

created by the impression of a shape/track Cast

sediment fills in a cavity left by a fossil

Fossil Video

FOSSIL DATINGWays of

determining fossil age:

1. Position within sedimentary rock

• Look at different strata:• Deeper is older

Dating is done by

comparing ratio of carbon 12 and carbon 14

Used to date things up to 50,000 yrs. old

2) Carbon dating

• Isotopes• Parent • Daughter

• Half Life (yrs)

• Dating Range (yrs) • Materials

• Carbon-14• Nitrogen-

14• 5730±30 • 0100-70,000 • Anything with C

• Potassium-40

• Argon-40 Calcium-

40• 1.3 billion • 50,000-4.6 billion

• Muscovite Biotite

Hornblende Whole volcanic

rock• Uranium-238

• Uranium-235

Uranium-232

• Lead-206 • Lead-207

Lead-208

• 4.5 billion • 710 million

14 billion

• 10 million-4.6 billion •  

• Zircon,U containing

• Rubidium-87

• Strontium-87

• 47 billion• 10 million-4.6

billion

• Muscovite Biotite

Potassium Feldspar

Whole metamorphic

or Igneous rock

Evidence From Living Organisms

1) Evidence of Common Ancestry -Organisms that are similar in

structure had a common ancestor

2. Homologous Structures vs. Analogous Structures

A. Homologous:Structures that are embryologically similar and functionally different

B. Analogous:Structures that are

embyologically different but function the same

Homologous Structures

4. Biochemical Comparisons:

-Examine biochemical compounds within organisms

3. Vestigial Organs:Organs that are seemingly functionless

5. Embryological Development:

Compare organisms at various stages of development

Embryonic SimilaritiesIndicate Common ancestor