Biomes
 The axis of rotation is angled 23.50 – the latitude that receives the
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most direct sunlight plus the most hours of sunlight changes
throughout the year as Earth orbits the Sun
Spring Equinox (March) – Sun directly overhead – all regions
get 12 hours of light + 12 hours of dark – spring begins in
Northern Hemisphere; fall in Southern Hemisphere
Summer Solstice (June) – max tilt of Northern Hemisphere
toward Sun – longest amount of daylight – summer begins
Fall Equinox (Sept) – opposite of March – day & night equal
Winter Solstice (Dec) – max tilt of Northern Hemisphere away
from Sun – shortest daylight – winter begins
 Biome – an area characterized by typical plants and
animals adapted to the yearly temperature and
precipitation
 Each biome contains many ecosystems whose
communities are adapted to local variation in climate,
soil, and other environmental factors
 Evaporation > precipitation
 30% of Earth
 Variations in annual
temp (red) and precip (blue)
in tropical, temperate, and
cold deserts
 Tropical
 warm temps
 high humidity
 photosynthesis
year-round
 Temperate
 Deciduous forests:
seasonal changes
broad leaves dropped for
cold winters
 Rain forests:
evergreens in cool,
moist environment
 Polar
 Taiga
long, cold winters
evergreens adapted to
year-round photosynthesis
 Tropical
savanna
 Temperate
prairie
 Polar
tundra
 Freshwater systems – low levels of dissolved salts
 Streams and rivers: from mountains to oceans
 Flow creates different conditions and habitats
 Headwaters: cold, clear, rapidly moving water with
high levels of O2
 Downstream: slower moving, less O2, warmer temps,
more algae and cyanobacteria
 Standing water: lakes and ponds
 Life found in layers – temperature, sunlight, dissolved
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O2, and nutrient availability changes with depth
Littoral zone: shallow area around shore; rooted
vegetation
Limnetic zone: open offshore area; too deep for rooted
plants; food chain begins with phytoplankton
Profundal zone: deep water without light; food chain
depends on organisms above
Benthic zone: muddy bottom; nourished by decaying
organic matter
 Wetlands – land is submerged part or all of the year
but is shallow enough for rooted vegetation
throughout
 Swamps: contain trees
 Marshes: mainly nonwoody vegetation (cattails)
 Estuaries
 Saltmarshes where rives flow into the ocean
 Nutrient rich areas due to river flow
 Mangrove swamps
 Also produce nutrient rich mud
 Intertidal zone
 Narrow strip between high and low tide mark on the
coastline
 Difficult habitat for life
 Coral reefs
 Warm, shallow water beyond the shoreline
 The open ocean
 Sunlight cannot penetrate to the bottom
 Photic zone: enough light for photosynthesis
 Aphotic zone: lacks light and therefore photosynthesis