Communicate information about biodiversity, how it arises through evolution, and how it supports ecosystem stability and benefits humans (Tennessee Academic Standards for Science, Biology I, BIO1.LS4).

What this topic is asking

The Tennessee LS4 standards ask you to communicate information about biodiversity: what it is, how it arises through evolution, and why it matters for ecosystems and humans. For the Biology I EOC that means knowing the levels of biodiversity, the link between genetic variation and a population's ability to survive change, how biodiversity supports ecosystem stability and resilience, and the benefits biodiversity provides to people. Items often ask why a high-variation population or a diverse ecosystem copes better with a disturbance.

The levels of biodiversity

These levels connect: genetic diversity within species underpins the ability of those species to persist, and a region with many species and habitats has high overall biodiversity. The EOC may ask you to identify which level a description refers to.

How biodiversity arises

Biodiversity is a product of evolution over vast spans of time. Mutation generates new alleles (genetic diversity), and natural selection and speciation turn variation into new adaptations and new species (species diversity). Each branching event in the tree of life adds to the variety, so today's biodiversity is the accumulated result of billions of years of descent with modification from common ancestors. This ties biodiversity directly to the evidence for common ancestry and to speciation.

Why genetic variation matters for survival

This is why conservation efforts try to maintain genetic variation, and why small, inbred populations (with little variation) are at greater risk.

Biodiversity and ecosystem stability

At the ecosystem level, high biodiversity generally makes an ecosystem more stable and resilient, meaning better able to withstand and recover from disturbances (a storm, a disease, a drought). The reason is a kind of redundancy: with many species and many feeding relationships in a complex food web, the loss or decline of one species can be compensated for by others that fill similar roles. A simple ecosystem with few species is more fragile, because the loss of one species can have large knock-on effects. This connects to ecosystem stability and resilience.

Why biodiversity benefits humans

Biodiversity provides many benefits (ecosystem services) to people:

• Food from diverse crops, livestock, and wild species.
• Medicines, many of which are derived from plants, fungi, and other organisms.
• Raw materials such as timber, fibers, and fuels.
• Pollination of crops by insects and other animals.
• Clean air and water, climate regulation, and soil formation from healthy ecosystems.
• Recreation, culture, and ecotourism.

Because so much depends on biodiversity, its loss (through habitat destruction, pollution, and climate change, covered in human impact on ecosystems) is a serious concern.

Try this

Q1. Name the three levels of biodiversity. [3]

• Cue. Genetic diversity (within a species), species diversity (number and variety of species), and ecosystem diversity (variety of habitats).

Q2. Explain why an ecosystem with high biodiversity tends to be more resilient than one with low biodiversity. [2]

• Cue. With many species and feeding relationships, the loss or decline of one species can be compensated for by others, so the ecosystem recovers more readily; a simple ecosystem is more fragile because losing one species has larger effects.