1. How would you characterize life on Earth up until 2.2 billion years ago? 2. H

Question

1. How would you characterize life on Earth up until 2.2 billion years ago?
2. How are eukaryotic cells different from prokaryotic cells? To answer this question, list and describe 4 ways.
3. According to Margulis' symbiosis theory, where did the mitochondria in eukaryotic cells come from?
4. What is the significance of the Ediacara fauna, and when does it occur on the Precambian time chart?
5. What is the main piece of evidence for continental glaciation in the Proterozoic record?
6. What led Joe Kirschvink to propose that the Earth was once frozen over from the poles to the equator?

Explanation / Answer

2. Eukaryotic cells differ from prokaryotic cells in many ways. Some of the major differences are;

1. Eukaryotic cells have well defined nucleus who h is surrounded by nuclear membranes. Prokaryotic cells do not have well d3fined nucleus. Their nucleus is without nuclear membrane, nucleoplasm, nuclear pores and nucleolus. Such as nucleus is called as nucleoid.

2. Membrane bound organelles like mitochondria, chloroplasts, ER, Golgi apparatus are absent in prokaryotic cells while as these organelles are present in eukaryotic cells.

3. Eukaryotic cells have both 70S and 80S ribosomes . Prokaryotic cells bear 70S ribosomes.

4. Respiratory enzymes are located on plasma membrane in prokaryotic cells while as in eukaryotic cells these enzymes are found in mitochondria.

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