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1.5 IB Bio
The Origin of Cells
Term | Definition |
---|---|
When did life begin? | -Earth is 4.5 billion years old -It took approx .5 billion years for the Earth to cool to form a crust -As early as 4 billion years ago early cells existed |
Cell Theory questioned in the origin of cells | -All cells come from pre-existing cells |
The four/five steps in creating the first cells (Step One) | 1. The non-living synthesis of simple organic molecules from a mixture of any three of methane, hydrogen, ammonia and water vapor. |
The four/five steps in creating the first cells (Step Two) | 2. The assembly of these molecules into polymers |
The four/five steps in creating the first cells (Step Three) | 3. The origin of self-replicating molecules that make inheritance possible |
The four/five steps in creating the first cells (Step Four) | 4. The packaging of these molecules into membranes with an internal chemistry different from their surroundings. |
The four/five steps in creating the first cells (Step Five) | 5. The development of binary fission of these protocells. |
Symbiosis | An association between two or more species. |
Endosymbiosis theory (Eukaryotes are formed from prokaryotes) | -Mitochondria of eukaryotes came from aerobic bacteria -Chloroplasts evolved from primitive autotrophic prokaryotes -Both were taken into larger heterotrophic cells by endocytosis -Eukaryotes then formed membranes that could contain the prokayotes |
Evidence to Endosymbiosis Theory | -Mitochondria and chloroplasts have DNA that is separate from the cells nuclear DNA -This DNA is similar to prokaryotic DNA (not associated with proteins) -Mitochondria and chloroplasts have small 70S ribosomes (regular eukaryotic ribosomes are 80S) |
Evidence to Endosymbiosis Theory- Part 2 | -Mitochondria and chloroplasts have double membrane |
Prior to Louis Pasteur (1822-1895) | -Notion of spontaneous generation was commonly accepted -This proposed that life is continuously being spontaneously created where no life previously existed |
Louis Pasteur's Experiment Step One | -Started with two flasks and a nutrient broth in each |
Louis Pasteur's Experiment Step Two | -Bent the necks of the flasks into "S" shapes |
Louis Pasteur's Experiment Step Three | -Boiled the broth to kill any existing microbes |
Louis Pasteur's Experiment Step Four | -Broke off the swan neck from the 1st flask only, exposing the nutrient broth to air from above. -In flask 2, dust particles remained near the tip of the swan neck |
Louis Pasteur's Experiment Step Five | -The broth in the broken flask quickly became cloudy (a sign of microbial life) -The unbroken flask remained clear |