Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What does the term biodiversity refer to?

1. The variety of life in a specific ecosystem

2. The total number of organisms in a habitat

3. The extinction rates of species

4. The number of environmental factors affecting life

The correct answer is: The variety of life in a specific ecosystem

Biodiversity is a comprehensive term that specifically encompasses the variety of life forms present within a given ecosystem, including the diversity of species, their genetic differences, and the ecosystems they form. This variety is crucial because it contributes to the resilience and functionality of ecosystems, allowing them to adapt to changes and pressures such as climate change and habitat destruction. The definition of biodiversity includes not just the number of different species, but also their interactions with each other and their environments, which makes the variety of life in a specific ecosystem a central aspect of its health and sustainability. In contrast to the other options, the total number of organisms in a habitat does not capture the complex relationships and interactions among different species that biodiversity emphasizes. The extinction rates of species are a consequence of losses in biodiversity rather than a measure of it, and the number of environmental factors affecting life may influence biodiversity but does not define it. Thus, the correct understanding of biodiversity centers on the variety of life itself within ecosystems.