Three Levels of Biodiversity at a Rice Field Edge
At the edge of a rice field, we can compare variation among rice plants, the species present, and habitat conditions. These observations lead to questions about genetic, species, and ecosystem diversity, but visible plant traits alone do not prove genetic differences.
Start with the Organisms and Their Habitat
Consider several rice clumps. Some are taller, some have different grain colors, and some mature at a different time. That does not automatically mean they are different species or that the differences are genetic. The environment can also affect visible traits, so genetic variation requires genetic or breeding evidence.
Around the rice, we may find fungi, small fish, frogs, aquatic insects, and other plants. Comparing the organisms present tells us about species diversity. Including the wet soil, water current, light, and shelter expands the comparison to ecosystem diversity.
Three Levels of Biodiversity
Biodiversity is the variation of living things within species, between species, and between ecosystems.
Biodiversity can be studied at genetic, species, and ecosystem levels.
A gene is a segment of DNA that can contribute to a trait, such as plant height or grain color. Observable traits can reflect genetic differences, environmental conditions, or both. Biologists use several species concepts. Under the commonly used biological species concept, members of a sexually reproducing species can generally reproduce with one another and produce fertile offspring. An ecosystem is a community of organisms and its nonliving environment interacting as a functional unit.
The comparison determines the level of diversity. Differences in rice height within one species concern genetic diversity when they result from inherited genetic differences. Differences among rice fields, mangroves, and coral reefs concern whole ecosystems.
Choose the level from the question: genetic diversity compares members of one species, species diversity compares the species present and their proportions, and ecosystem diversity compares habitats and ecological relationships.
| Scale | Main question | Close example | Mistake to avoid |
|---|---|---|---|
| Genes | Why are members of one kind not exactly the same? | Rice varieties differ in height, harvest time, or grain color | Calling variation inside one kind many species |
| Species | Which species live there, and how evenly are individuals distributed among them? | Rice, small fish, frogs, fungi, aquatic insects | Counting species while ignoring their relative abundance |
| Ecosystems | What habitat and environmental relationships differ? | Rice fields, rivers, mangroves, coral reefs | Explaining place differences from one organism only |
Genetic Variation Within One Species
Genetic diversity appears when organisms belong to the same species or population, but their inherited variants are not exactly the same. In rice, different varieties can vary in plant height, harvest time, grain color, or resistance to environmental conditions. Different genetic variants and their combinations can contribute to these traits, often together with the growing environment.
A visible trait is usually not determined by genes alone. Plant height, for example, can be influenced by inherited variants as well as water, nutrients, light, and other growing conditions.
Genetic differences can make individuals respond differently to the same environmental change. A population with more variation is therefore more likely to include individuals that survive and reproduce under the new conditions.
Comparing Diversity at Larger Scales
Genetic diversity compares members of one species. Species diversity compares the species that live together, while ecosystem diversity also compares their habitats and ecological relationships.
Species Diversity Compares Which Species Are Present
Species diversity considers both how many species occur in one place, called species richness, and their relative abundance, often described as evenness. At the edge of a rice field or another wet cultivated area, rice may live alongside fungi, small fish, frogs, aquatic insects, and microscopic organisms. Two sites can have the same species richness but different evenness if one species dominates one site while individuals are distributed more evenly at the other. Each species also has its own traits and ecological role. Rice produces organic matter through photosynthesis, fungi help decomposition, and fish and frogs become part of the food web.
Ecosystem Diversity Compares Habitats and Relationships
Rice fields, rivers, tropical rainforests, mangroves, savannas, and coral reefs have different conditions. Light, water, salinity, soil, temperature, and organism interactions shape which living things can survive there.
Indonesia contains many tropical habitats across several biogeographic regions. Much of western Indonesia lies on the Sunda Shelf and has strong Asian affinities, while Papua lies on the Sahul Shelf and has strong Australasian affinities. Wallacea lies between them as a complex transition zone. Its boundaries differ among groups of organisms, so biologists compare evidence from each group. The present distribution of Indonesian species results from environmental conditions, geological history, dispersal, evolution, and long-term biological interactions.
Primary biodiversity records can come from museums, scientific collections, DNA barcodes or short DNA markers, and field photographs. Records of place, time, and organism identity can then support a claim that a species occurs in a region.
Choose the Level of Biodiversity First
When observing nature, first identify what is being compared. Differences among members of one species belong to genetic diversity. Differences among the species present belong to species diversity. Differences among habitats and ecological relationships belong to ecosystem diversity.
One rice field edge, garden, or forest can contain all three levels at once. The place stays the same, but the question determines which level of biodiversity is being studied.