During an investigation of a freshwater lake, a Biology student discovers a previously unknown microscopic organism. Further study shows that the unicellular organism is eukaryotic. (a) Identify FOUR organelles that should be present in the eukaryotic organism and describe the function of each organelle. (b) Prokaryotic cells lack membrane-bound organelles found in eukaryotes. Describe what the cell would have looked like if the student had discovered a prokaryotic organism instead. What structures would still be present?

Explanation:

Four organelles that would be present if the organism is a unicellular eukaryotic "animal" will be

(a)

1) Plasma membrane:  A selectively permeable barrier that regulates what goes in and out of the cell hence surrounds the cell.

2) Chromosome: It harbours/houses the nucleus which stores the genetic material.

3) Nucleus: It is the organelle inside of the chromosome that stores the gene/genetic material of the cell.

4) Mitochondria: It is generally referred to as the power house of the cell. This is because it generates the energy that the cell uses to carry out it's function.

(b)

The main difference between the eukaryotic and prokaryotic organisms is that eukaryotic organisms have well defined nucleus while prokaryotic organisms lack well defined nucleus- they have nucleoid. The nucleoid stores almost (if not all) the genetic material of the prokaryotic organisms; hence they serve similar function as the nucleus in that regard. Structures such as plasma membrane and cytoplasm (is the internal part of the cell in which several other organelles are attached) are still present in prokaryotes.