A Level Biology Practice Exam

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What does species richness measure?

The total number of individuals in a community
How many different species are present
The average age of species in a habitat
The genetic diversity within a species

The correct answer is: How many different species are present

Species richness specifically measures how many different species are present in a given community or area. It is an important component of biodiversity and reflects the variety of life forms in an ecosystem. By quantifying the number of distinct species, researchers can assess the health and stability of ecosystems, as higher species richness is usually associated with greater ecological resilience and functioning. This measurement does not consider the abundance of those species or their distribution—it purely focuses on diversity at the species level. Other related concepts, such as species evenness and overall biodiversity, incorporate additional factors, but species richness by itself provides critical insights into ecological composition.