Final answer:
In population density studies for terrestrial organisms, water bodies are typically excluded because they are not habitable by these organisms, and excluding them does not cause mistakes in calculations.
Step-by-step explanation:
When conducting population density studies for terrestrial organisms, researchers typically exclude water bodies since these areas are not habitable for the organisms. Thus, the correct answer to whether population density studies take into effect water bodies for terrestrial organisms is No, and it doesn't cause mistakes (b). Including areas such as lakes, rivers, and oceans in these calculations would indeed cause mistakes as it would give an inaccurate representation of the available habitat and could lead to an underestimation of the true population density.
Population size and density are crucial metrics used to describe and understand populations in a given habitat and are important in conservation efforts and ecological studies. Accurate estimates of these metrics are essential to properly manage and protect species.