Question

A) Multicellularity arose several separate times within the Kingdom Protista. What does it mean to be multicellular?  Why might mutlticellularity be an advantage? In your answer contrast the unicellular life of a Paramecium, to a semi-multicellular protist, like kelp. How do an aggregate (like plasmodial slime mold) and a colony (like Volvox) illustrate the transition from unicellular to multicellular organisms?

B)What types of density-dependent effects do we see in human populations as conditions become crowded due to overpopulation? (Give at least two examples and how it affects humans or other living organisms) Give an example of a density-independent effect that has occurred recently to a human populations somewhere in the world.  

Answer 1

A) A Multicellular organism is an organism as the name suggests consist of more than one cell. These cells function together resulting in a specialized function. The advantages of multicellular organisms include:

• They have a higher lifespan as there are many specialized subgroups of cells to perform various functions.
• Multicellular organisms can maintain homeostasis and defend themselves from the external environment.
• In single-celled organisms the death of the cell results in the death of the organism and this is not the case for multicellular organisms
• There is functional and size limitation for the single-celled organisms while its not a problem for multicellular organisms
• Multicellular organisms evolved to do sexual reproduction in which variations could be incorporated easily.

Talking about paramecium and kelp, they are unicellular and multicellular respectively. The size of a paramecium is  50 to 300um while kelps are giant organisms up to 30m in length. Kelps reproduce sexually while paramecium does fission.

Volvox is an example for a transition from single-celled to multicellular organisms. They come together to form cell aggregates of 600 to 6000 cells on average and do the functions together. Thus they are known as the transitions from unicellularity to multicellularity.

B) Overpopulation is a major drawback the world is facing these days. An increase in density such as in countries like India and China is leading to scarcity of the limited resources. This had effects on agriculture, employment, renewable resources, accommodation, etc. This can affect the total economy of the country and end result could be poverty and unemployment. This can also increase pollution and can lead to the exploitation of the resources.