Explain the importance of biodiversity and the factors, including environmental change, that lead to extinction (North Carolina Standard Course of Study, Biology, LS.Bio.10).

What this topic is asking

North Carolina LS.Bio.10 asks you to explain the importance of biodiversity and the factors that lead to extinction, including environmental change. For the Biology EOC you need to know what biodiversity is, why it supports ecosystem stability and resilience (and benefits humans), and the natural and human causes of extinction. Items often ask you to link a human activity to species loss or to explain why diversity matters.

What biodiversity is and why it matters

Biodiversity matters most for ecosystem stability and resilience. A diverse ecosystem, with many species and a wide range of genes, is better able to withstand and recover from change: if a disease, a drought, or a new predator strikes, a varied community is more likely to contain species or genetic variants that can cope, so the ecosystem keeps functioning. A low-diversity system is more fragile, because the loss of one species can have large knock-on effects.

Extinction and its causes

Extinction is the permanent loss of a species, occurring when its members can no longer survive and reproduce, so the species disappears. Extinction is a natural part of evolution and has always happened, often through slow environmental change or natural disasters that the species could not adapt to fast enough.

However, human activities have greatly accelerated extinction. The major human causes the EOC expects are:

• Habitat destruction (clearing forests, draining wetlands, urban development), the leading cause: removing the food, shelter, and breeding sites a species needs.
• Pollution of air, water, and soil, which can poison organisms or degrade their environment.
• Overhunting and overharvesting, taking organisms faster than they can reproduce.
• Invasive species, introduced organisms that outcompete or prey on native species.
• Human-caused climate change, shifting conditions faster than many species can adapt.

A species with low genetic diversity is especially vulnerable, because it has less variation to draw on if the environment changes (this ties back to the value of genetic variation). Slowing extinction is the goal of conservation, which protects habitats and biodiversity.

Try this

Q1. Explain why greater biodiversity tends to make an ecosystem more stable. [2]

• Cue. A wider variety of species and genes means that if conditions change, some are more likely to survive and keep the ecosystem functioning (more resilience).

Q2. Name three human activities that can cause extinction. [3]

• Cue. Any three of habitat destruction, pollution, overhunting or overharvesting, invasive species, and human-caused climate change.