Kneel by a pond on a summer evening. A dragonfly snatches a midge; a frog eyes the dragonfly; a heron watches the frog. Sunlight, water and mud feed the plants that feed them all. You are looking at an ecosystem — a web of life stitched together by feeding and energy.
What is an ecosystem?
An ecosystem is a community of living things (plants, animals, fungi, microbes — the biotic parts) together with the non-living surroundings (sunlight, water, soil, climate — the abiotic parts). The living and non-living parts depend on one another; this is called interdependence. Remove one part and the rest can suffer.
- Producers — green plants that make food from sunlight by photosynthesis.
- Consumers — animals that eat plants (herbivores) or other animals (carnivores).
- Decomposers — fungi and bacteria that break down dead matter and return nutrients to the soil.
Food chains and food webs
A food chain shows one path of energy, for example grass to grasshopper to shrew to owl. The arrows point in the direction energy flows — from the eaten to the eater. In reality most animals eat several foods, so many chains link into a food web.
Nutrient cycling and global biomes
When plants and animals die, decomposers break them down and release nutrients back into the soil, where plants take them up again. This endless recycling keeps the ecosystem fed. On a world scale, ecosystems with similar climate and plant life are grouped into biomes. Because climate is set mostly by latitude, biomes form broad bands around the globe: cold tundra near the poles, then belts of forest, grassland and desert, and finally the lush rainforest at the equator. The same rules that shape a garden pond, then, shape the whole living planet.
| Biome | Climate | Plant life |
|---|---|---|
| Tundra | Cold, dry | Mosses, low shrubs |
| Taiga | Cold winters | Coniferous trees |
| Desert | Hot, very dry | Cacti, sparse plants |
| Rainforest | Hot, wet | Dense tall trees |