Biomes and The Biosphere

1. Biomes and The Biosphere

2. Introduction to Ecology • Study of interactions between organisms and the environment • Abiotic and biotic factors play a role in distribution and abundance of a species • The Biosphere • Entire portion of Earth inhabited by life

3. North Pole 60°N Low angle of incoming sunlight 30°N Tropic of Cancer Sunlight directly overhead at equinoxes 0° (equator) Tropic of Capricorn 30°S Low angle of incoming sunlight 60°S South Pole Atmosphere Climate • Temperature, precipitation, sunlight, and wind • Most significant influence on distribution of organisms • Determined by sunlight intensity, air currents, presence of large bodies of water, mountain ranges • All of these vary mainly as a factor of latitude and altitude • Climograph

4. Biomes • Major ecosystem, characterized by a particular climate and type of vegetation Tropical forest Desert Temperate grassland 30 Temperate broadleaf forest 15 Annual mean temperature (°C) Coniferous forest 0 Arctic and alpine tundra –15 400 300 200 100 Annual mean precipitation (cm)

5. Climate and Biomes • Biomes change with altitude and latitude because vegetation is partly determined by temperature (and precipitation).

6. 30°N Tropic of Cancer Equator Tropic of Capricorn 30°S Chaparral Tundra Key Temperate grassland High mountains Tropical forest Polar ice Temperate broadleaf forest Savanna Coniferous forest Desert Terrestrial Biomes • Tropical forests: equator, most complex, constant temperature and rainfall, canopy • Savanna: tropical grassland with scattered trees, occasional fire and drought; large herbivores • Desert: sparse rainfall • Chaparral: spiny evergreen at midlatitudes along coasts • Temperate grassland: All grasses; seasonal drought; occasional fires; large mammals • Coniferous forest: cone-bearing trees • Tundra: permafrost; very little precipitation

7. Aquatic Biomes • Freshwater or marine (saltwater) • Physically and chemically stratified • Vertical stratification • Photic zone - light (photosynthetic organisms; phytoplankton) • Aphotic zone - little light • Benthic zone - bottom substrate • Benthos - community of organisms that live in benthic zone • Detritus - dead organic material • Distance from shore • Littoral, limnetic • Intertidal, neritic, oceanic • Open water versus bottom (pelagic vs benthic) • Chemical stratification • Changes in temperature, oxygen and nutrient content vary with depth • Thermocline - narrow stratum of rapid temperature change that separates more uniformly warm upper layer from more uniform cold deeper waters • Turnover

8. Intertidal zone Coastal zone Pelagic zone 0 Photic zone 200 m Continental shelf Benthic zone Aphotic zone Marine zonation 2,500–6,000 m Abyssal zone (deepest regions of ocean floor) Marine biomes • Intertidal zone - area where land meets water • Neritic zone - shallow regions over continental shelves • Oceanic zone - very deep water past the continental shelves • Pelagic zone - open water of any depth • Benthic zone - seafloor bottom • Abyssal zone - benthic region in deep oceans

9. Littoral zone Limnetic zone Photic zone Pelagic zone Benthic zone Aphotic zone Zonation in a lake Freshwater Biomes • Littoral zone • Shallow, well lit waters, close to shore, rooted plants • Limnetic zone • Well-lit, open water, farther from shore, phytoplankton and cyanobacteria • Profundal zone • Deep, aphotic waters • Lake classification • Oligotrophic - deep, nutrient poor • Eutrophic - shallow, high nutrient content

10. Spring Winter O2 (mg/L) O2 (mg/L) 0 4 8 12 0 4 8 12 Lake depth (m) Lake depth (m) 8 8 16 16 0° 4° 4° 2° 24 24 4° 4° 4° 4° 4° 4° 4°C 4°C O2 concentration High (>8 mg/L) Medium (4–8 mg/L) Low (<4 mg/L) O2 (mg/L) O2 (mg/L) 0 4 8 12 0 4 8 12 Lake depth (m) Lake depth (m) 4° 22° 8 8 4° 20° 18° 4° 8° 4° 16 16 6° 4° 5° 4°C 4°C 24 24 Summer Thermocline Autumn Turnover in Lakes • Seasonal turnover due to changes in temperature cycles oxygen and nutrients between photic and aphotic zones