Which of the following organisms is an example of a saprotroph?

A saprotroph is an organism that feeds on decaying organic matter, breaking it down and obtaining nutrients in the process. This type of organism plays a crucial role in the ecosystem by recycling nutrients, which helps in the decomposition of dead materials and contributes to soil health.

In this case, a bacterium is a prime example of a saprotroph, as many types of bacteria thrive on decomposing organic matter. These microorganisms secrete enzymes that break down complex organic substances into simpler compounds, which they can absorb and use for growth and energy. This decomposition process not only sustains the bacteria but also enriches the soil with essential nutrients that benefit other organisms in the ecosystem.

The other organisms listed, such as a tiger (which is a carnivore), a bat (which can be an insectivore or frugivore), and an oak tree (which is a producer), do not primarily obtain their energy and nutrients through the decomposition of organic matter. Therefore, the bacterium stands out as the correct choice when identifying a saprotroph.