17-3 Major Biological Communities
I. Climate largely determines where species live
A. Climate = prevailing weather conditions, most importantly temperature and moisture, which help determine biological communities
B. Biomes = major biological communities that occur over a large area of land
C. Additional factors play important roles in determining where biomes are located
- soil type
- wind
- latitude
- elevation
II. There are seven major biomes
A. Tropical rain forests
- abundant rainfall (200-450 cm/year), little seasonal variation
- high productivity, dominated by large trees
- infertile soil, most of the nutrients are held in the plants
- decomposition occurs quickly
- at least 50% of all terrestrial species
B. Deserts
- sparse precipitation (less than 25 cm/year)
- sparse vegetation, which is drought resistant, such as cacti
- covers large areas of continental interiors
C. Savannas
- low precipitation (90-150 cm/year), with long dry seasons
- tropical grasslands, with widely spaced trees
- located between tropical forests and deserts
D. Temperate deciduous forests
- plentiful precipitation (75-250 cm/year), distributed throughout the year
- temperate regions are about half way between equator and poles
- dominated by large trees, which usually shed leaves during cold winter
- drier regions, different soils favor evergreen forests
- very dry summers favor shrubs, chaparral
E. Temperate grasslands
- moderate climates with less precipitation than temperate deciduous forests
- temperate regions are about half way between equator and poles
- prairies, or open grasslands, with deep, thick roots
- highly fertile soil, usually converted to agriculture
F. Taiga
- cold, wet climates, with long winters, and most precipitation in summer
- closer to poles than equator
- dominated by large coniferous trees
- large mammals are common
G. Tundra
- very low precipitation (less than 25 cm/year)
- between taiga and poles
- brief summers, long very cold winters
- soil often boggy, permafrost (permanently frozen soil at depths greater than 1 meter)
- mostly low growing plants
III. Aquatic communities are linked to terrestrial communities
A. Organic & inorganic materials continuously enter bodies of water via streams and runoff
B. Freshwater communities
- lakes cover about 1.8% of Earth's surface; streams about 0.3%
- ponds and lakes have three main zones:
a. littoral zone = shallow, near shore, with aquatic plants and smaller animals
b. limnetic zone = surface waters away from shore, with algae, zooplankton, fish
c. profundal zone = deep water, limited light, with bacteria and decomposers
C. Marine communites
- nearly 75% of Earth's surface
- oceans have three main zones:
a. shallow ocean waters = shallow, near shore, rich communities with aquatic plants
and many animals
b. surface of the open ocean = surface waters away from shore, rich with
phytoplankton (40% of all producers on Earth), zooplankton, many fish, invertebrates
c. depths of the ocean = deep water, limited light, with bacteria, decomposers,
unusual carnivores, and occasional deep sea vents
D. Estuaries = saltwater marshes
- very productive, collecting organic and inorganic materials via streams and runoff
- aquatic plants shelter developing fish, birds, invertebrates
- endangered by human development
