Construct an argument, based on evidence, for the importance of biodiversity and how evolution produces the diversity of life (Louisiana Student Standards for Science, High School Biology, HS-LS4).

What this topic is asking

Louisiana's LS4 standards ask you to construct an argument for the importance of biodiversity and to connect it to evolution. For LEAP 2025 Biology you should be able to define biodiversity, explain how natural selection and speciation produce it over long periods, argue why it supports ecosystem stability, and identify the threats to it. Because this is an argument standard, the test rewards a claim backed by clear biological reasoning.

What biodiversity is

Biodiversity is the diversity half of the LS4 core idea, "Unity and Diversity." The unity comes from common ancestry (all life is related); the diversity comes from evolution producing many different forms.

How evolution produces biodiversity

So biodiversity and evolution are two sides of one idea: evolution by natural selection, acting on variation in many different environments, generates the variety of life.

Why biodiversity supports ecosystem stability

A central argument the standard asks for is that biodiversity makes ecosystems more stable and resilient:

• With many species, the ecosystem has more ways to keep functioning if conditions change, because it is likely that some species can tolerate the disturbance.
• A high-diversity ecosystem is less dependent on any single species, so losing one has a smaller effect.
• Genetic variety within species gives populations the raw material to adapt to change rather than go extinct.

A low-diversity ecosystem, by contrast, is more vulnerable: a single disease, pest, or environmental shift can have a large effect because there are few alternatives.

Why biodiversity matters to humans, and the threats

Biodiversity also has direct value to people: it provides food, medicines (many drugs come from natural organisms), raw materials, and ecosystem services such as clean air and water, pollination of crops, and decomposition of waste. It also represents future options, the genetic and species variety we may need later.

Biodiversity is threatened mainly by human activities: habitat destruction, pollution, overharvesting, the spread of invasive species, and climate change. These reduce the number of species and the genetic variety within them, which is why conservation aims to protect biodiversity.

Try this

Q1. Define biodiversity and state how it arises from evolution. [2]

• Cue. Biodiversity is the variety of life (number of species and genetic variety); it arises as natural selection in different environments causes populations to diverge and new species to form over long periods.

Q2. Explain why an ecosystem with high biodiversity is more resilient to a disturbance than one with low biodiversity. [2]

• Cue. With many species, some are likely to survive the disturbance and keep the ecosystem functioning, and it is less dependent on any single species, so losing one has a smaller effect.