Chapter 3 Summary
CONCEPT 3.1 Terrestrial biomes are characterized by the dominant growth forms of vegetation.
- Terrestrial biomes and their associated plant growth forms reflect global patterns of precipitation and temperature.
- The potential and actual distributions of terrestrial biomes differ due to human influences, particularly conversion of land for agriculture and grazing.
- There are nine major terrestrial biomes: rainforests, seasonal forests and savannas, and deserts in tropical and subtropical climates; grasslands, shrublands and woodlands, deciduous forests, and evergreen forests in the temperate zone, and boreal forests and tundra in polar regions.
- Biological communities in mountains occur in elevational bands associated with gradients in temperature and precipitation.
CONCEPT 3.2 Biological zones in freshwater systems are associated with the velocity, depth, and chemistry of the water.
- Biological communities in streams and rivers vary with stream order and location within the stream channel.
- Biological communities in lakes vary with depth and the amount of light penetration.
CONCEPT 3.3 Marine biological zones are determined by ocean depth, light availability, and the stability of the bottom substratum.
- Estuaries, salt marshes, and mangrove forests occur in shallow zones at the margins between terrestrial and marine systems, and are influenced by the import of fresh water and sediments by nearby rivers.
- Biological communities at the shoreline reflect the influence of tides and the stability of the substratum (sandy versus rocky).
- Coral reefs and kelp and seagrass beds are productive communities with high diversity associated with habitat complexity provided by their photosynthesizers.
- Biological communities of the open ocean and deep benthic zones contain sparse populations of organisms, whose distributions are determined by light availability and proximity to the bottom.
