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Ecosystems and Biomes
From Local Communities to Global Patterns
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Ecosystems and biomes help biologists organize life on Earth from small local interactions to broad global patterns. An ecosystem is a community of organisms interacting with one another and with nonliving factors such as water, soil, air, and sunlight. A biome is a large region defined mainly by climate and dominant plant life, such as desert, tundra, or tropical rainforest. Understanding both ideas helps explain why similar environments support similar life forms in very different parts of the world.
Biomes form because temperature and precipitation strongly affect which plants can grow, and plants in turn shape food webs, habitats, and nutrient cycles. Within each biome, many different ecosystems can exist, such as ponds, forests, grasslands, or coral reefs. Energy flows through ecosystems from producers to consumers and decomposers, while matter is recycled through water, carbon, and nutrient cycles. Human activity can alter ecosystems and even shift biome boundaries by changing climate, land use, and biodiversity.
Key Facts
- Ecosystem = organisms + abiotic environment + interactions
- Biome = large geographic region defined by climate and dominant vegetation
- Primary productivity generally increases with warmth and available water
- Energy flow in a food chain can be approximated by the 10% rule
- Net primary productivity = gross primary productivity - plant respiration
- Climate patterns are often summarized by average temperature and annual precipitation
Vocabulary
- Ecosystem
- A system made of living organisms interacting with each other and with nonliving parts of their environment.
- Biome
- A large ecological region characterized by a particular climate and typical plant and animal communities.
- Abiotic factor
- A nonliving part of the environment, such as temperature, water, sunlight, or soil.
- Producer
- An organism, usually a plant or alga, that makes its own food using sunlight or chemical energy.
- Biodiversity
- The variety of living organisms in an area, including differences in species, genes, and ecosystems.
Common Mistakes to Avoid
- Confusing a biome with an ecosystem, because a biome is a broad climate-based region while an ecosystem is a specific interacting system within an area. A desert biome can contain many ecosystems such as dunes, oases, and dry washes.
- Assuming only living things matter in ecosystems, which is wrong because abiotic factors like water, temperature, and soil strongly affect survival and distribution. Ignoring nonliving conditions gives an incomplete explanation of ecosystem patterns.
- Thinking energy is recycled in ecosystems, which is wrong because energy flows one way through food webs and much of it is lost as heat. Matter is recycled, but energy must keep entering, usually from sunlight.
- Believing all places in the same biome have identical species, which is wrong because biomes share climate patterns and general vegetation, not exact organisms. Different continents can have similar biome conditions but different species evolved there.
Practice Questions
- 1 A grassland ecosystem receives 12000 kJ of energy in producers. Using the 10% rule, how much energy is available to primary consumers and how much is available to secondary consumers?
- 2 A forest has a gross primary productivity of 2500 g/m^2/yr and plant respiration of 900 g/m^2/yr. Calculate the net primary productivity.
- 3 Explain why tropical rainforests and deserts support very different ecosystems even when both receive strong sunlight.