10 Biomes and Global Ecology

Biomes, Ecosystems, and Environmental Conditions

A Biome is a broad region whose climate is associated with characteristic plant and animal communities. The term describes large-scale patterns, not a single uniform landscape. A particular Ecosystem is a community of organisms interacting with each other and with their physical surroundings; many ecosystems can exist within one biome.

Biomes are broadly grouped into terrestrial and aquatic environments. To understand why their communities differ, begin with the environmental conditions that shape life.

Climate, Productivity, and Adaptation

The Climate of a region is its long-term pattern of temperature and precipitation. On land, both the average amounts and seasonal variation influence which plants can grow. In turn, vegetation affects the food and shelter available to animals.

Latitude influences the amount and seasonality of sunlight. Elevation, ocean currents, prevailing winds, and mountains also affect temperature and rainfall. For example, air rising over a mountain range may lose moisture as rain, leaving drier conditions on the other side.

These conditions shape Primary productivity: the rate at which producers such as plants and algae build biomass. Warm, wet places with long growing seasons can support high plant growth. Deserts and tundra tend to have lower productivity because of limited water, extreme temperatures, or short growing seasons.

Organisms have adaptations that help them cope with local conditions. Desert plants may store water or have reduced leaves. Plants in cold regions may grow close to the ground or retain needle-shaped leaves.

The Major Terrestrial Biomes

The eight commonly recognized terrestrial biomes illustrate how climate relates to characteristic vegetation and patterns of animal life:

• Tropical wet forest: Warm and rainy much of the year, with dense, layered evergreen vegetation and high species diversity.

• Savanna: Warm, with seasonal rainfall and a prolonged dry season. Grasses and scattered trees support grazing animals and their predators.

• Subtropical desert: Very low, often unpredictable rainfall; sparse vegetation and organisms adapted to conserve or find water.

• Chaparral: Mild, wet winters and hot, dry summers. Drought-tolerant shrubs are common, and fires are an important disturbance.

• Temperate grassland: Seasonal temperatures and moderate rainfall. Grasses dominate, with few trees away from rivers.

• Temperate forest: Moderate rainfall and distinct seasons. Deciduous trees often lose their leaves in winter.

• Boreal forest (taiga): Long, cold winters and short summers, with coniferous trees common.

• Arctic tundra: Very cold, low precipitation, and a short growing season. Low-growing plants are common, and Permafrost—ground that remains frozen for extended periods—may limit roots.

These categories describe broad patterns rather than identical landscapes. Soil, fires, water availability, and local topography produce variation within biomes. For example, a temperate grassland may include wetlands along streams even when surrounding conditions discourage widespread tree growth.

Aquatic Habitats and Their Conditions

Aquatic communities are influenced by Salinity, light, temperature, water movement, and dissolved nutrients. Freshwater environments include lakes, ponds, rivers, streams, and wetlands. Marine environments include the open ocean, coastal waters, coral reefs, and estuaries, where freshwater mixes with seawater.

Light is important because photosynthesis depends on it. In many ocean areas, enough light for photosynthesis reaches roughly the upper 200 meters; below this zone, photosynthesis is generally not possible. Surface waters can support phytoplankton and food webs based on photosynthesis. Deep-sea communities depend on food drifting down from above or, in some places, on chemical energy used by microbes near hydrothermal vents.

Water movement also helps determine where organisms live. Rivers and streams favor organisms able to withstand flowing water. Tides expose intertidal organisms to changing water and air conditions, while currents and mixing can move nutrients through marine habitats. Estuaries have shallow, productive waters and fluctuating salinity, so their inhabitants must tolerate changing conditions.

Global Patterns and Key Connections

Similar climates can produce similar broad vegetation types in distant regions, but the communities are not necessarily identical. Regional history, geographic barriers, soils, and the species available in an area also matter.

In aquatic environments, depth, distance from shore, salinity, and water flow help create distinct habitats. Across both land and water, organisms are distributed according to environmental conditions and their adaptations to them.

Takeaway: Climate is a major influence on terrestrial life, while aquatic communities are shaped by factors such as light, salinity, nutrients, and water movement. In both settings, local conditions interact to shape productivity and the organisms that can thrive.