Climate & Biogeography Biogeographic realms Environmental components affect the • By 1800s, many naturalists began to identify distribution and abundance of organisms 2 broad patterns of distribution Kangaroos/km Climate in northern Australia is hot > 20 and wet, with seasonal drought. – biogeographic realms 10–20 5–10 1–5 0.1–1 Red kangaroos < 0.1 occur in most Limits of semiarid and arid Palearctic distribution regions of the interior, where precipitation is Nearctic Tropic relatively low and of Cancer Oriental variable from (23.5°N) year to year. Ethiopian Equator Neotropical (23.5°S) Southeastern Australia Tropic of Australian Southern Australia has has a wet, cool climate. Capricorn cool, moist winters and warm, dry summers. Tasmania Factors that Limit Species Distribution Factors that Limit Species Distribution • Abiotic (nonliving) Limiting Factors • Density Dependent Limiting Factors – Temperature – Limited resources – Water • Food – Soil type • Water • Safe refuge – Sunlight • Predation – Salinity • Competition – Wind stress • Living space – Altitude, depth – Disease, Pollution • Biotic (living) Limiting Factors • Density Independent Limiting Factors – Food source – Natural disasters – Competition • Hurricanes – Predators • Floods, landslides, volcanoes – Social factors, mates • Drought, frost – Pathogens, parasites – Environmental insult • Deforestation – Vegetation • Pesticide • Fire – Climatic change Climate Latitude is an important correlate for • The prevailing weather conditions in a particular area temperature, sun exposure, and rainfall • Four major abiotic components: – Temperature, water, sunlight, and wind • Macroclimate: patterns on global & regional scales • Microclimate: very fine, small-scale patterns – scale determined by size & mobility of the organisms – e.g., conditions encountered by the community of organisms underneath a fallen log Figure 52.3 Heyer Climate & Biogeography The equator receives maximal solar heating producing predictable patterns of wind and rainfall WET and DRY GLOBAL AIR CIRCULATION AND PRECIPITATION PATTERNS • Uneven heating causes wet and dry areas Figure 52.3 Figure 52.3 Seasons Coriolis Effect SEASONAL VARIATION IN SUNLIGHT INTENSITY Effect of the earth’s rotation upon objects/fluids in motion over long distances • Winds, ocean currents, long-range artillery March equinox: Equator faces sun directly; • Causes motion to veer off neither pole tilts toward sun; all regions on Earth • In Northern Hemisphere, veer clockwise 60°N experience 12 hours of daylight and 12 hours of June solstice: Northern • In Southern Hemisphere, veer counter-clockwise 30°N darkness. Hemisphere tilts toward 0° (equator) • No effect at equator 66.5°N (Arctic Circle) sun; summer begins in Northern Hemisphere; 60°N winter begins in 30°S Southern Hemisphere. Global air circulation Westerlies and precipitation patterns 30°N Northeast trades December solstice: Northern 0° Hemisphere tilts away from sun; Constant tilt winter begins in Northern Southeast trades of 23.5° Hemisphere; summer begins September equinox: Equator faces sun in Southern Hemisphere. directly; neither pole tilts toward sun; all 30°S regions on Earth experience 12 hours of Westerlies daylight and 12 hours of darkness. 60°S Figure 52.4 Figure 52.3 66.5°S (Antarctic Circle) OCEAN CURRENTS Climate fluctuations are reduced by proximity to bodies of water 2 Air cools at 1 Warm air high elevation. over land rises. 3 Cooler air sinks over water. 4 Cool air over water moves inland, replacing rising warm air over land. • Heat absorbed by ocean waters at the equator is distributed northward. • Greatly moderates climate extremes. • Warm zones especially expanded along western boundary currents. c.f., Figure 52.5 Figure 52.6 Heyer Climate & Biogeography General global pattern modified by “rain Biomes: shadow” to leeward side of mountain ranges the major types of ecosystems Coastal regions: Inland regions: Wet with moderate temps Dry with extreme Terrestrial biomes hot/cold temps • Primary determining factors – Temperature (latitude, altitude) – Water availability (rainfall) • Secondary determining factors – Substrate (soil type) – Photoperiod (latitude again) – Wind (evaporative cooling, physical stress) Influence rainfall, temperature, and photoperiod. – Disturbance (fire, volcano, mudslide, storm, etc.) Figure 52.6 Terrestrial Biomes CLIMATE IMPACTS ORGANISMS Climatograph • Annual mean temperature • Annual mean precipitation • Controls vegetation patterns Figure 52.8 Figure 52.9 Convergence Similar form & function in unrelated organisms from similar ecosystems TROPICAL FORESTS • Warm, stable temperature • 100+ inches of rain – Rain forest: consistent – Dry forest: seasonal • Low nutrient soils Euphorbia Cereus sp. canariensis • Rapid decomposition and recycling Cactus from Americas Euphorb from Africa • Most complex – Patchy & stratified • High diversity Figure 52.10 Heyer Climate & Biogeography SAVANNA BIOME DESERT BIOME • Warm temperature • Temperature extremes • Low but consistent • Precipitation infrequent rainfall • Evaporation exceeds • Less structure and precipitation diversity – Life keyed to rainfall – Adaptations for water • Fire and grazing conservation prevent tree invasion • 30° north and south • Rain shadow CHAPARRAL BIOME TEMPERATE GRASSLANDS • Cold winters “Mediterranean climate” • Seasonal drought • Cool offshore currents • Occasional drought • Mild rainy winters • Grazing and fire • Long hot summers • Prevent invasion by • Frequent fires shrubs and trees • Vegetation adapted to • Deep fertile soils fire • Human impact TEMPERATE DECIDUOUS (BROADLEAF) FOREST CONIFEROUS FORESTS Largest terrestrial biome • 35° to 50° north and • Short summers south • Harsh winters • Ample precipitation • Poor soils • Warm summers and cold winters • Cone bearing trees • Deciduous vegetation • Fire maintained • Rich soils • Temperate rain forests in • Many human impacts northwestern North America Heyer Climate & Biogeography Aquatic Biomes TUNDRA BIOME >75% of Earth’s surface • Northern latitudes • Alpine regions above 30°N treeline Tropic of Cancer Equator • Short, warm summers Continental Tropic of shelf Capricorn • Long, bitter cold winters 30°S • Permafrost • Low growing vegetation Key Lakes Rivers Estuaries Abyssal zone (below oceanic Coral reefs Oceanic Intertidal zone pelagic zone) pelagic zone Stratification of aquatic biomes LAKES • Oligotrophic: few nutrients→few producers →clear water • Many aquatic biomes are stratified into zones (layers) • Eutrophic →abundant nutrients →abundant phytoplankton defined by light penetration, temperature, and depth →murky, green water LAKES Intertidal zone Neritic zone Oceanic zone Littoral Limnetic 0 zone Photic zone zone 200 m Continental Pelagic shelf zone Benthic Photic Aphotic zone zone zone Benthic Pelagic zone zone Aphotic zone 2,500–6,000 m Abyssal zone (a) Zonation in a lake. (b) Marine zonation. Oligotrophic lake in Eutrophic lake in Okavango Grand Teton, Wyoming delta, Botswana Figure 52.12 LAKES • Lakes are sensitive to seasonal temperature change WETLANDS – Often experience seasonal turnover • Alternate between aquatic and terrestrial 2 In spring, as the sun melts the ice, the surface water warms to 4°C WETLANDS and sinks below the cooler layers immediately below, eliminating the In winter, the coldest water in the lake (0°C) lies just 1 thermal stratification. Spring winds mix the water to great depth, below the surface ice; water is progressively warmer at bringing oxygen (O ) to the bottom waters (see graphs) and deeper levels of the lake, typically 4–5°C at the bottom. 2 nutrients to the surface. Spring O2 (mg/L) Winter O2 (mg/L) 0 4 8 12 0 4 8 12 8 8 Lake depth (m) 16 Lake depth (m) 16 0° 4 2° 4° ° 24 4° 4° 24 4° 4° 4 O concentration ° 4° 2 4°C 4°C High Medium Low O2 (mg/L) O2 (mg/L) 0 4 8 12 0 4 8 12 4° 22° 8 4° 20° 8 4° 18° 16 4° 8 16 Lake depth (m) Lake depth (m) ° 4° 6° 5° 24 4°C 4 C 24 Autumn Thermocline ° Summer 4 In autumn, as surface water cools rapidly, it sinks below the 3 In summer, the lake regains a distinctive thermal profile, with underlying layers, remixing the water until the surface begins warm surface water separated from cold bottom water by a narrow to freeze and the winter temperature profile is reestablished. vertical zone of rapid temperature change, called a thermocline. Okefenokee National Wetland Reserve in Georgia Figure 52.13 Heyer Climate & Biogeography OCEAN ZONES ESTUARIES Neritic province: over shelf • Transition between freshwater and marine Oceanic province: off shore ESTUARIES (open water) An estuary in a low coastal plain of Georgia OCEAN ZONES Light absorption & penetration in the sea Only top 2% of ocean has sufficient sunlight for photosynthesis. (open water) TROPICAL NERITIC BIOME TEMPERATE NERITIC BIOME • Warm, stratified, oligotrophic waters • Cold, eutrophic waters → most productive • Coral reefs — “oases in the desert” • Upwelling: surface water blown offshore; replaced CORAL REEFS by deep water • Phytoplankton blooms & kelp forests < 1% of ocean area, but > 50% of fish productivity Bull kelp Coral reef in the Red Sea Heyer Climate & Biogeography ABYSSAL BENTHIC BIOME OCEANIC BIOME • Dependent upon organic “marine snow” raining Earth’s largest ecosystem! (>90% of biosphere) down from euphotic surface waters • Isolated pockets of chemoautotrophs MARINE BENTHIC ZONE Toothed whales Baleen whales Zooplankton Fish A deep-sea hydrothermal vent community Heyer .