Explain what biodiversity is, why genetic and species diversity matter for the resilience of populations and ecosystems, and how human activity threatens it (NYSSLS LS4, stability and change; cause and effect).

What this topic is asking

NYSSLS LS4 asks you to explain what biodiversity is, why it matters, and how it links to the stability of populations and ecosystems. On the Life Science: Biology Regents this often comes as a cluster comparing a uniform population with a diverse one when conditions change. The crosscutting concepts are stability and change and cause and effect.

What biodiversity is

Both kinds of diversity matter. Genetic diversity is the variation within a species (the raw material for natural selection); species diversity is the range of different species in an ecosystem. The exam may ask about either, so use the right term.

Why genetic diversity matters

This is the same logic that links variation to surviving change in speciation and extinction. The classic exam scenario contrasts a uniform crop, which a single disease can wipe out, with a diverse crop, in which some resistant plants survive.

Why species diversity matters

A more species-diverse ecosystem tends to be more stable and resilient. With many species, the loss or decline of one can be compensated for by others that fill similar roles, so the ecosystem keeps functioning when conditions change. A simple ecosystem with few species is more fragile, because the loss of one species can disrupt the whole system. This links biodiversity to the stability of food webs (see ecological relationships and succession).

Threats to biodiversity

Human activity is the major modern threat to biodiversity. Habitat destruction, pollution, climate change, overharvesting and the introduction of invasive species all reduce the number of species and the genetic variation within them, increasing the risk of extinction (see human impact on ecosystems). Conserving biodiversity, by protecting habitats and reducing these pressures, helps keep populations adaptable and ecosystems resilient.

Try this

Q1. Define biodiversity, including the two kinds of diversity it covers. [2]

• Cue. The variety of life in an area, including species diversity (the number and variety of species) and genetic diversity (variation within a species).

Q2. Explain why a genetically diverse population is more likely to survive a new disease than a uniform one. [2]

• Cue. With more variation, some individuals are more likely to be resistant and survive to reproduce, so the population persists; a uniform population can all be affected at once.