Overview of the Origin of Overview of the Origin of LifeLife

Chapter 14Chapter 14

Biogenesis Biogenesis vs vs

Spontaneous GenerationSpontaneous Generation• Spontaneous generation- the thought

before the 17th century, living things could come from non-living things

• Biogenesis=all living things come from other living things

Redi’s ExperimentRedi’s ExperimentItalian ScientistItalian Scientist

Meat

No MaggotsMaggots

Flies

Eggs

John NeedhamJohn Needham

Spallanzani ExperimentSpallanzani ExperimentItalian Scientist #2Italian Scientist #2

Pasteur’s ExperimentPasteur’s Experiment

History of EarthHistory of Earth

Formation of EarthFormation of Earth

• 5 billion years ago the solar system was a swirling mass of gas and dust

• The planets are thought to have formed from violent collisions of space debris.

• The age of earth is approx. 4 billion years old

• It is based on studying the layers of sediment in the earth’s crust

Radioactive DatingRadioactive Dating

• Establishes the age of material

• All atoms of the same element have the same atomic number

• However, they can differ in the number of neutrons?

• (What is that called?)

Radioactive Dating Cont.Radioactive Dating Cont.

• Answer: Isotope• Mass # = proton and neutrons in the nucleus• Ex: Mass of carbon is 12, 6 protons and 6

neutrons• Most elements have isotopes• Isotopes are designated by their mass #- eg. Carbon-12 = mass of 12 How about Carbon -14?

IsotopesIsotopes

• Isotopes have unstable nuclei

• They undergo radioactive decay

• This are called radioactive isotopes

• The length of time it takes for half of an isotope to decay is referred to as: Half Life

• The age of the material can be determined by measuring the particular radioactive isotope it contains

Example of Carbon DatingExample of Carbon Dating

Alexander OparinAlexander Oparin

• Thought the earth was once very different and contained ammonia NH3, hydrogen gas, and water vapor.

• Thought these elements formed organic compounds of amino acids.

• Complex chemical reactions might have occurred to bring about macromolecules essential for life. (Name some?)

Harold Urey and Stanley MillerHarold Urey and Stanley Miller

• Ideas from Oparin

• Experiment: contained a chamber of gas, as gas circulated electric sparks, (acting as lightening) supplied the energy to drive the chemical reaction

• Other experiments branched off from this one including how ATP and DNA were formed.

Molecules to Cell-like StructuresMolecules to Cell-like Structures

MicrospheresMicrospheres: organic molecules that : organic molecules that spontaneously form, spherical in shape and contain spontaneously form, spherical in shape and contain

protein-organized in a membraneprotein-organized in a membrane

CoacervatesCoacervates• COACERVATES, polymer-rich colloidal droplets, have been studied in the

Moscow laboratory of A. I. Oparin because of their conjectural resemblance to prebiological entities. These coacervates are droplets formed in an aqueous solution of protamine and polyadenylic acid. Oparin has found that droplets survive longer if they can carry out polymerization reactions.

Making CoacervatesMaking CoacervatesOur Lab Experiment Our Lab Experiment

First Life FormsFirst Life Forms

• 3.5 billion year old fossils found near the north pole (unicellular organisms)

• Why is RNA necessary and DNA must have RNA to carry out life functions?

• What does RNA have that DNA doesn’t (besides Uracil)?

What was the Role of RNA?What was the Role of RNA?

• Thomas Cech- unicellular eukaryotes had RNA that was able to act as an enzyme- ribozymes

• Life is thought to have started with self replicating RNA

• Competition between RNA molecules may have occurred- What does that remind you of today that contains RNA?

The 1The 1stst Prokaryotes Prokaryotes

• Very little oxygen

• Must have been anaerobic

• Very small in size

• Most likely heterotrophic-taking organic molecules from the environment

• As the resources for the heterotrophs became limited autotrophs are thought to have evolved.

ArcheabacteriaArcheabacteria

• Kingdom of Unicellular organism that thrive in harsh environments

• Most are autotrophic• Obtain energy by chemosynthesis and not

photosynthesis• Chemosynthesis- Carbon dioxide is the carbon

source, producing carbohydrates from inorganic sources instead of from light.

• Energy is obtained from inorganic molecules (sulfur)

CyanobacteriaCyanobacteria

• One of the 1st photosynthetic microorganisms• Able to withstand the change from carbon

dioxide to oxygen• The ozone formed and even though toxic to

plants and humans helps to prevent UV radiation on earth.

CYANOBACTERIA OZONE

FIRST EUKARYOTESFIRST EUKARYOTES• Began 2-1.5 billion years ago• Small eukaryotes are thought to have developed inside

larger prokaryotes that were anaerobic• Lynn Margulis-proposed they lived in an endosymbiotic

relationship- mutually beneficial relationship• Aerobic prokaryotes are thought to have produced the 1st

mitochondria • Later invaders thought to have given rise to chloroplasts• Both chloroplasts and mitochondria contain some

genetic material (single stranded circular DNA) so they are able to reproduce independently.

http://cosmology.com/Cosmology2.htmlhttp://cosmology.com/Cosmology2.html

• http://hegel.lewiscenter.org/users/mhuffine/subprojects/Instructor/IPBIO%20Main%20Page/ppt/Attributes%20of%20life_files/v3_document.htm