Bio U1 - 1.5

Question 1

Discuss the implications of all cells being formed from preexisting cells.

Answer 1

Implication 1: All cells of our body can be traced back to the first cell, the zygote
Implication 2: The origin of all cells can be traced down to the last universal common ancestor of all life on Earth
Implication 3: There must have been a first cell to have arose from a non-living material

Question 2

Outline the four processes needed for the spontaneous origin of cells on Earth.

Answer 2

1. The synthesis of simple organic molecules from inorganic compounds.
2. The assembly of these organic molecules into polymers.
3. The formation of a polymer that can self replicate (enabling inheritance).
4. Packaging of molecules into membranes with an internal chemistry different from the surroundings.

Question 3

Outline the experiments of Miller and Urey into the origin of organic compounds.

Answer 3

The experiment consisted in the analysis of the hypothesis of Oparin-Haldane, in which simple organic molecules can arise from inorganic compounds.

Question 4

Explain the process of the experiment conducted by Miller and Urey

Answer 4

Boiled water evaporates and then mixes with methane, ammonia, and hydrogen gases. As they mix, they are shocked by electrodes to simulate lighting. Later, a condenser makes the water drip back down to the initial flask and the organic molecules (amino acids and began to settle in that flask while the water evaporates once again.

Question 5

Describe Pasteur’s experiments about spontaneous generation.

Answer 5

Pasteur’s experiment was done to oppose the theory of spontaneous generation, in which living beings arose from non-living ones. With two beakers and controlled temperature, humidity, exposure to sun, and air flow, only the independent variable was analyzed. First, he heated the broth in both flasks to sterilize it, then let the flask be and bacteria to reproduce. One flask had a curved neck which allowed the entrance of air without the contact of bacteria with the broth, while the other flask had a straight neck that allowed that contact. The curved neck flask guaranteed that bacteria could not reach broth and that was what happened, while the other broth was contaminated. This disproved spontaneous generation.

Question 6

State the endosymbiotic theory

Answer 6

Theory that states that mitocondria and chloroplasts evolved from free living prokariotic cells that were engulfed (but not digested) by early eukariotic cells. They would go on to develop a symbiotic relationship.

Question 7

Outline the major events in the origin of eukariotic cells

Answer 7

1. Ancestral Prokaryote
2. Infolding of cell membrane
3. Cell with nucleus and endomembrane system
4. Engulfing of aerobic prokaryote
5. Ancestral aerobic eurkaryote cell
6. Engulfing of photosynthetic prokaryote
7. Ancestral Photosynthetic eukaryote

Question 8

Describe the evidence for the endosymbiotic theory

Answer 8

Mitochondria and Chloroplasts, besides having a double membrane, share the following similarities with prokaryotes:
1. Shape
2. Size
3. 70s Ribosomes
4. Circular, naked DNA
5. Gene sequences
6. Movement
7. Binary fission
8. Antibiotic resistance