Biodiversity and Conservation: KS3 Biology Explained

Biodiversity is the variety of life on Earth — the number and range of species in an area, plus the genetic variation within them. High biodiversity makes ecosystems stable and resilient. When it falls, ecosystems become fragile and the services they provide — clean water, food, medicines, and climate regulation — are put at risk.

What does biodiversity mean?

Biodiversity (short for biological diversity) has three interconnected levels:

Species diversity — the number of different species in an area (species richness) and how evenly distributed their populations are. An oak woodland with 50 species of plant, 1,000 species of insect, and 50 species of bird is more biodiverse than a plantation of a single tree species.

Genetic diversity — the variety of genes within a species. A large, genetically diverse population can better resist disease and adapt to changing conditions. Cheetahs, for example, have very low genetic diversity — the result of a near-extinction bottleneck — making them vulnerable to new diseases.

Ecosystem diversity — the range of different habitats and ecosystems (rainforests, coral reefs, wetlands, grasslands) present in a region or on the planet.

When ecologists measure biodiversity in a habitat, they often use sampling methods such as quadrats (counted squares) and transects (line surveys) to estimate species number and abundance.

Why does biodiversity matter?

Healthy, biodiverse ecosystems provide ecosystem services — benefits that humans depend on:

Ecosystem service | Example
Food production | Wild pollinators (bees, hoverflies) pollinate crops worth billions of pounds per year
Clean water | Wetland plants filter pollutants from water before it reaches rivers and reservoirs
Climate regulation | Forests and oceans absorb CO₂, slowing climate change
Medicine | Many drugs were discovered from wild species (penicillin from mould, aspirin from willow bark, cancer drugs from the rosy periwinkle)
Soil fertility | Worms, fungi, and bacteria decompose organic matter, recycling nutrients that plants need
Flood control | Peat bogs, woodlands, and wetlands absorb rainfall and slow run-off, reducing flood risk

Beyond practical value, biodiversity has intrinsic value — many scientists and ethicists argue that species have a right to exist regardless of their usefulness to humans.

What are the main threats to biodiversity?

Human activities are currently driving a sharp decline in global biodiversity, sometimes called the sixth mass extinction:

Threat | How it reduces biodiversity
Habitat destruction | Deforestation, draining wetlands, and urban development remove the living space species need
Habitat fragmentation | Roads and development split habitats into isolated patches, cutting populations off and reducing genetic diversity
Climate change | Rising temperatures and shifting rainfall patterns alter habitats faster than many species can adapt or migrate
Overexploitation | Overfishing, hunting, and unsustainable harvesting reduce population sizes directly
Invasive species | Non-native species outcompete, predate, or spread disease to native species; e.g. grey squirrels in the UK displaced red squirrels
Pollution | Pesticides, fertiliser run-off (eutrophication), plastics, and industrial chemicals harm or kill organisms

In the UK, the State of Nature report found that around 15% of species are threatened with extinction and that species have declined on average by 19% since 1970.

What is conservation and what methods are used?

Conservation is the management of ecosystems and species to protect, restore, or maintain biodiversity. It does not mean leaving nature untouched — it often requires active intervention.

In-situ conservation (in place)

Protecting species within their natural habitat:

Nature reserves and national parks (e.g. the Lake District, Cairngorms) set aside land where habitats are protected from development.

Marine protected areas (MPAs) restrict fishing and other activities in sea areas, allowing fish stocks and reef ecosystems to recover.

Hedgerow and woodland management maintains habitat connectivity so species can move between patches.

Reintroduction programmes — returning species to their former range (e.g. red kites successfully reintroduced to England and Wales; beavers to Scotland).

Ex-situ conservation (outside natural habitat)

Protecting species away from their habitat as a safety net:

Zoos and wildlife parks — breed endangered species and maintain genetic diversity through coordinated breeding programmes.

Seed banks — store seeds of thousands of plant species at low temperature and humidity (e.g. the Millennium Seed Bank at Kew Gardens holds seeds from 40,000+ species).

Cryopreservation — freezing genetic material (eggs, sperm, embryos) of critically endangered animals.

How do human land-use decisions affect biodiversity?

Every land-use decision involves trade-offs between biodiversity and human needs:

Intensive farming maximises food yield per hectare but creates monocultures (single-species fields) with few habitats for other species.

Organic farming and agri-environment schemes reduce pesticide use and maintain field margins, hedgerows, and ponds that support wildlife.

Rewilding — deliberately restoring natural processes (reintroducing predators, allowing rivers to meander, reducing grazing) — is emerging as a cost-effective way to restore biodiversity at scale in some regions.

The key insight at KS3: biodiversity and human welfare are not automatically opposed. Protecting ecosystems protects the services humans depend on.

Frequently asked questions

What is biodiversity in KS3 biology?

Biodiversity is the variety of life in an area — the number and range of species present, the genetic variation within those species, and the range of habitats and ecosystems. High biodiversity means a richer, more stable ecosystem. It is measured using sampling techniques such as quadrats and transects, and can be compared between habitats or over time to track changes.

What is the biggest threat to biodiversity?

Habitat destruction is generally considered the biggest threat — when habitats are cleared for farming, housing, or industry, all the species that depended on them lose their living space simultaneously. Climate change is increasingly a major threat as it alters temperature and rainfall patterns faster than many species can adapt. Pollution, invasive species, and overexploitation are also significant causes of biodiversity loss.

What is the difference between in-situ and ex-situ conservation?

In-situ conservation protects species and habitats in their natural environment — for example, nature reserves, marine protected areas, and habitat restoration. Ex-situ conservation protects species away from their natural habitat — for example, zoo breeding programmes, seed banks, and cryopreservation. Both approaches are needed: in-situ is the ideal long-term solution, but ex-situ provides a safety net for critically endangered species while in-situ efforts improve.

Why should we conserve biodiversity?

Biodiversity provides ecosystem services that humans depend on: pollinators for crops, clean water, stable climate, medicines, and fertile soils. Beyond utility, biodiversity has intrinsic value — species have evolved over millions of years and have the right to exist. Once a species is extinct, it is gone forever. Conserving biodiversity now is far cheaper and easier than attempting to restore ecosystems after collapse.

For Socratic biology tutoring with Professor Darwin, visit aitutors.me.