Evolution: Origins of Life. We know that there is a great variety of living organisms in our...
-
Upload
blaze-morris -
Category
Documents
-
view
212 -
download
0
Transcript of Evolution: Origins of Life. We know that there is a great variety of living organisms in our...
Evolution: Origins of Life
We know that there is a great variety of living organisms in our biosphere.
All living organism also interact with one another as well as with abiotic factors.
We are all composed of the 4 same biomolecules
How did we get to be a planet with such rich biodiversity?
I. Theories on the Origins of Life
• A. People’s idea about where some living things come from have changed throughout history.
• B. Prior theories:– 1. Recipe for Bees (Aristotle)– 2. Spontaneous Generation(disproved by Francesco Redi)– 3. Pasteur’s TestLiving things come from living things
II. Changing Theories
• A. Redi’s experiment:– 1. Controlled jars – open meat jars, maggots appeared– 2. Tested jars (covered in gauze) – maggots did not
appear
• B. Redi’s experiment scientists understood that life could not rise from nonliving matter. (abiogenesis)
II. Changing Theories
• C. Pasteur’s Experiment:– 1. Boiled broth that was kept open to air through a
round neck did not have any microorganisms living in it– 2. If the flask with broth was broken living things would
begin to appear
• D. Pasteur’s experiment allowed scientists to begin to understand that living things only come from other living things. (biogenesis)
III. Conditions of Early Earth
• A. Some scientists still believe that spontaneous generation of life occurred once but was now impossible because the conditions found on early Earth have changed.
• B. Several scientists began experiments to replicate ancient Earth & gain support for the “primordial soup” theory. Oparin & Haldane proposed such theories.
• C. Ancient Earth:– 1. Major volcanic eruptions– 2. Hundreds of meteor showers– 3. Constant lightning storms– 4. Atmosphere composed of carbon dioxide, nitrogen,
hydrogen sulfide & sulfur dioxide– 5. NO OXYGEN!!
IV. Miller-Urey Experiment (1953)
• A. Mixture of water, hydrogen, methane, and ammonia was cycled through an apparatus that delivered electrical sparks to the mixture.
• B. At the end about 10% to 15% of the carbon in the system was now in the form of a mixture of organic compounds, including something similar to amino acids, which are the building blocks of proteins.
Life on Earth came from Mars
V. First Life
• A. All living things are composed of cells; the 1st life form was an organism very similar to bacteria.
• B. First life forms were composed of prokaryotic cells– 1. Prokaryotic cells – cells with no nucleus
VI. Endosymbiosis• A. Scientists theorize that
eukaryotic cells originated through symbiosis between micro-organisms. – 1. In other words: organelles were
taken inside another cell and became part of the cell
• B. Example:– 1. An animal cell’s mitochondria
was originally a proteobacteria – 2. A plant cell’s chloroplasts was a
cell taking up a cyanobacteria