What led to the evolution of multicellular organisms?

Answer 1

If the why question is asking from a position of purpose, i.e. for what reason did multicellular organisms evolve from unicellular organisms, the question can only be answered from a religious or philosophical perspective. Science cannot impart motive to nature.

If the why question is asking from a position of what the process was that lead from uncellular to multicellular organisms, the answer is simple. Selection pressures favored having numerous distinct cells that work in tandem over individual cells that did not and then further cells that were in complete union with each other over those that work in tandem. There are a number of intermediate steps between unicellular and multicellular organisms. Probably the most clear "midway" point is the colonial organism of which the extant Volvox is one of the best examples. (Admittedly Volvox itself is only 200 million years to present old, so it is not a remnant of this transition, but is similar to what scientists surmise was part of the transition that led to the development of multicellular organisms.) In a colonial organism, numerous unicellular organisms work in tandem to achieve goals (similar to how geese fly in flocks even though each is autonomous). The required communication would select cells that more effectively communicate with each other, leading to cells that can function as part of the same organism.

Answer 2

Recent hypotheses argue that the development of multicellularity is the result of an adaptation to both scarcity of foods and predation. Multicellular organisms can more easily guard themselves from small predators, and can more easily move around to locate new sources of food.

Experiments have been run to confirm these hypotheses, and it has been observed that populations of single-celled organisms may indeed evolve to the point where they form colony organisms when predators are introduced or foods become scarce.

Answer 3

The question is incomplete. There are no options given (for "which of the following") to answer this question.

Answer 4

cell differientiation

Answer 5

appearance of eukaryotic cells