Biomes (bioclimatic zones) are appropriate divisions by which to organize
the natural world, because the organisms that live in each of them possess common
constellations of adaptations to them, in particular to the climate of each of the
zones and to the characteristic vegetation types that develop in them. The primary
elements to be dealt with under each zone were chosen because they are considered
the basic elements at all levels, from the entire planet through each of its component
physical environments to the species themselves.
Biomes of the World
Major terrestrial biomes
Examples of biomes. Which one am I?
What is the relationship between biomes and climate?
- if you knew the mean temperature and rainfall of a region, and especially
if you had some measure of their variability and seasonality, you could predict
the type of biotic communities that would be found there.
- and even if you didn't know the exact species of plants and animals that might
live in the region, you could predict adaptations they might have that would allow
them to live there.
Examples of how various physical factors influence climate
- Northern North America, Europe and Asia below ice-cap
- bitterly cold winters, short summers, growing season (60 days)
- low rainfall (20 cm/yr) but lots of melting snow in summer
- high elevations above timberline (alpine tundra)
- Arctic tundra photo
- regions where rainfall is less than 20 cm/yr
- cold (Great Basin desert between Sierra Nevadas and Rockies) and hot (Sahara
and Sonoran desert in Arizona)
- not all deserts have sandy soils
- The Ultimate Desert Resource
- 10 to 30 inches/yr (25-75 cm/yr) of rainfall, but not enough to support trees
(or trees widely scattered)
- Savannah plants
- relatively cold winters
- variety of names (e.g., savanna in tropical/subtropical regions, prairie
in temperate regions)
- height of the grasses reflects local moisture Types of grasslands in NA
- extensive root systems
- rich soil
- maintained by grazing and fire
Temperate Deciduous Forest
- south of the northern boreal forest (taiga) in eastern North America,
eastern Asia, and much of Europe (and in equivalent zones in the southern hemisphere)
- moderate climate with relatively high rainfall (distributed over entire year)
- well-defined seasons, with growing season between 120 and 300 days
- rich soil from decomposed leaf litter
- temperate areas with poor soil and little water support coniferous forests
Temperate Rain Forests
- wet and cool climates where marine air meets coastal mountains
- very limited distribution; Chile and the Pacific Northwest
- sustain highest standing biomass of all terrestrial ecosystems
Tropical Rain Forests
- South America, Africa, and the Indo-Malayan region near equator
- warm/hot weather with plentiful rainfall (200-400 cm/yr)
- growing season is year-long (dry season may be 2-3 months)
- richest and most complex biome
- rapid recycling of nutrients, poor soil for agriculture
- competition for light leads to vertical stratification of species
Net primary productivity is influenced by temperature, rainfall, and other
factors (availability of sunlight, nutrients, and length of growing season).
The more productive a community, the more life it can support per unit area.
Terrestrial biome(s) with highest net primary productivity:
Adaptations of Organisms
Working in groups and, later, consulting your textbook and using the links above
and below, list some adaptations (in structure, function, behavior, etc.) found in
the various plants and animals that increases their likelihood of existing in these biomes.