1. 1 ORIGIN OF LIFE Chapter 14 Topics: Biogenesis Earth’s History First Life Forms

2. 2 Spontaneous Generation  Living things can arise from non-living things  Many believed that the air had some sort of capacity to generate life  Invisible “ether”  Widely accepted theory of the origin of living things until ~1600s  As the scientific theory took hold, many began to discard this view

3. 3 Biogenesis  All living things come from living things  Many began to challenge the theory of spontaneous generation in favor of biogenesis  But, these scientists had rough road ahead to change the minds of many  Redi  Spallanzani  Pasteur

4. 4 Francesco Redi  Italian scientist 1626-1697  He hypothesized maggots/flies arose from meat that had been infested with the fly eggs.  He set up experiment with a control group of meat with no cover and an experimental group of meat with a cover to keep the flies out  Control group became infested with maggots  Experimental group remained maggot-free

5. 5 Lazzaro Spallanzani  Italian scientist 1729-1799  He theorized that the microorganisms found in food came from pre-existing organisms not from the air – folks still did not believe Redi’s results  Set up an experiment to test his hypothesis  Control group – boiled meat broth, left open to air after boiling  Experimental group – boiled meat broth, sealed immediately after boiling  Results – no microorganisms in sealed container

6. 6 Louis Pasteur  French scientist 1822-1895  He took Spallanzani’s work one step farther – he also believed these microorganisms are in the air and contaminate food  He set up an experiment similar to Spallanzani’s except he did not seal experimental group flasks  Instead, he designed a special crooked neck flask to allow air in but trap any organisms before they could enter the sterile broth  His broth remained open to air, but microorganism- free for more than a year.  So air is not able to spontaneously generate life

7. 7 So how did “it” all begin?  As humans entered into this new age of enlightenment, they began to question not only what gives rise to living things, but how did life and Earth begin.  As you know, often finding answers takes a long time and humankind needed to acquire the tools and knowledge to find the answers to the questions that plague us all.

8. 8 Big Bang  Current theory contends that “it” all began as a singularity.  This is something with infinitely large mass but packed into an infinitely small volume with a huge magnetic force.  This singularity simply expanded, so the term “big bang” is a bit of a misnomer – there was no explosion, but a big expansion  At that instant all the matter, energy, and forces that exist now came into existence

9. 9 Big Bang…  This expansion occurred ~13.7 B years ago.  The matter from the singularity moving outward at great speed and at extremely high temperature.  Swirling masses of matter eventually formed our solar system and our Earth about 4.5 B years ago  The universe is still expanding and we are now able to detect the faintest radio emissions dating from the time of the Big Bang, enabling scientists to better date that event.

10. 10 How do we know the age of Earth?  Primarily from radioactive dating methods  Radioactive elements break down and decay into more stable elements  Half-life is the time it takes for ½ of a sample of a radioactive element to decay  Carbon-14 has a ½ life of 5730 Years  C-14 used to date organic material  Uranium-238 has a ½ life of 4.5 Million Years  U-238 used to date inorganic material

11. 11 Early Earth  But the surface cooled and water formed to cover much of the surface  Early Earth compounds very different from modern  Early atmosphere reducing atmosphere (CO 2, H 2 S, CH 3 )  But many scientists thought this primordial soup of the ancient oceans gave rise to the first organic molecules that led to the beginning of life

12. 12 Stanley Miller & Harold Urey  At the University of Chicago in the 1950s, they devised & conducted an experiment to make organic compounds from this primordial soup  They created an apparatus to contain this ocean mixture; using electricity to simulate lightning strikes  Experiment yielded: amino acids, ATP, & nucleotides – all the necessary components of a living cell

13. 13 Lerman’s Bubble Model alternative to “primordial soup” model  Proposed in 1986 by geophysicist Louis Lerman  Suggests that chemicals necessary for life found in bubbles at the ocean surface  Bubbles produced at deep sea ocean vents, trapping escaping gases (NH 3, CH 3 ) in bubbles  The bubbles essentially protected compounds from UV degradation & concentrated them; rxns leading to amino acids thus occurred safely & faster  As bubbles burst at ocean surface, UV radiation and lightning energy provided E for further rxns, creating the molecules required by living organisms  http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AbioticSynthesis.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AbioticSynthesis.html

14. 14 How do we get from molecules to a cell?  This is one question to which there is no good answer – at least not yet.  However, many organic molecules naturally coalesce when in solution and scientists theorize that this is what happened  Microspheres – protein molecules that group  Coacervates – molecules of different types linked by amino acids and sugars

15. 15 Terms  Autotrophe – organism that uses E to synthesize organic molecules from inorganic material  Heterotrophe – organism that obtains organic “food” molecules by eating other organisms or their by-products  Prokaryote – cell with no nucleus, no membrane-bound organelles  Eukaryote – cell with nucleus and membrane-bound organelles  Photosynthesis – production of carbohydrates by using E from light  CO 2 + Light + H 2 O  C 6 H 12 O 6 + O 2  Chemiosynthesis – production of carbohydrates by using E from inorganic sources NOT light  Glycolysis – first step to making ATP  If oxygen present, aerobic respiration occurs  If no oxygen present, fermentation occurs  Fermentation – pathway for breaking down organic molecules when NO oxygen is present  Cellular Respiration – process by which cells make ATP by breaking down organic compounds  Aerobic Respiration – process of making ATP, oxygen is final electron acceptor

16. 16 Archaebacteria – closest link to early living cells -Early bacteria were autotrophic – using chemosynthesis not photosynthesis ( remember no sunlight getting thru the thick cloud layer ) -They were able to survive harsh environments ( remember the atmosphere is full of poisonous gases and it is still pretty hot ) -Some of these acquired the ability to photosynthesize by 3 billion years ago -Oxygen (O 2 ) was the by product of these cells & it built our modern atmosphere

17. 17 Eukaryotes  Current theory as to how these arose is the Endosymbiotic Theory proposed by Dr. Lynn Margulis.  Somehow a prokaryote entered another prokaryote; a symbiotic relationship ensued; the organism reproduced  The “inside” prokaryote became the chloroplast and mitochondria of today’s eukaryotic cells  Remember mitochondria and chloroplasts have their own DNA