Final answer:
Bacteria generally outnumber human cells, with estimates ranging from a 10:1 to a 1:1 ratio of bacteria to human cells, indicating a symbiotic and complex ecosystem on and within the human body. The correct option is B.
Step-by-step explanation:
Comparing the number of cells in humans with the number of bacteria on and within them, bacteria generally outnumber human cells. Earlier estimates suggested a ratio of 10:1 in favor of bacteria. However, more recent studies indicate that the ratio is closer to 1:1, meaning that our bodies are host to nearly as many bacterial cells as human cells.
Bacteria thrive in various parts of the human body such as the mouth, nasal cavity, throat, ears, gut, and on the skin, particularly in moist areas. This not only includes symbiotic and commensal bacteria but also potential pathogens that could cause diseases, highlighting the complex relationships we have with these microorganisms.
It's important to recognize that bacteria play crucial roles in maintaining human health, such as aiding in digestion and protecting against harmful microorganisms. At the same time, they can also be responsible for infections.
This dual nature suggests that bacteria and humans are in a delicate balance of mutualism and competition, making up a complex ecosystem within and on the human body.