Ecosystems in the Biosphere

Biomes and Abiotic Factors

• Biomes: broad geographical areas with similar biological communities
• Determined by climate
• Temperature
• Precipitation
• Vegetation reflects adaptations to specific climates
• Evapotranspiration: the amount of water plants lose due to climate
• Ratio between water demand and availability determines plant types
• Deserts: Low precipitation and high evapotranspiration
• Dominated by succulents
• Low biomass
• Rain Forest: High precipitation and high evapotranspiration
• Very moist and dense vegetation
• High biomass

Convergent Evolution

• Plants may look similar, but have different evolutionary history and mechanisms
• Plants converge in appearance and function since they are adapting to similar environments Example: Cacti from North America and Euphorbes from Africa look very similar, but have extremely different evolutionary histories and mechanisms for tolerating hot and dry conditions.

Aquatic biomes

• Shaped by
• Climate
• Nutrient availability
• Oxygen
• Sunlight
• Primary producers
• Shallow aquatic systems
• Macroscopic Algae
• Aquatic plants
• Open Ocean
• Photosynthetic microscopic organisms
• Aquatic biomes include:
• Intertidal
• Coral reefs
• Pelagic realm
• Deep sea

Biomes: Freshwater

Ponds & Lakes

• Can be BIG or small
• Can be seasonal (Example: ponds) or last for hundreds to thousands of years (Example: the Great Lakes)

• Is broken down into layers:
• Littoral Zone = near the shore
• Warm temperatures in the summer, cold to frozen temperatures in the winter (depending on latitude)
• Supports: algae, aquatic plants, snails, clams, insects, crustaceans, fish and amphibians
• Organisms in this zone provide food for snakes, birds and turtles
• Limnetic Zone = open water near the surface
• Supports: plankton and some fish
• Profundal Zone = Bottom of the lake
• Cold and dense
• Little to no light = minimal if any plants

Streams & Rivers

• Bodies of water that flow in generally one direction connecting a source/headwater (Example: snowmelt, lake, underground springs) to the mouth of another body of water (Example: lake or ocean)
• Varying levels of light and oxygen availability throughout the length of the river/stream system
• Example: lots of oxygen where the headwater enters the river but low amount of oxygen where the river meats the mouth

Wetlands

• Includes standing waters like marshes, swamps and bogs
• High species diversity
• Support: hydrophytes (lilies, cattails, black spruce), amphibians, birds, mammals and fish

Biomes: Forest

Tropical Forests

• Found at latitudes near the equator
• Has 12 hour light/dark cycles
• Does not have winter, only has the RAINY or the DRY season
• Little temperature variation, between 20-25°C all year
• Gets more than 200cm/year of rainfall
• Dense and continuous canopy causes low light conditions on the forest floor
• Supports: evergreen trees, ferns, vines, mosses, palms
• Supports: birds, bats, small mammals, insects

Temperate Forests

• At 25-50° latitudes in both hemispheres (United States, Europe, South America)
• Has fertile soil
• Supports: oak, hickory, beech, maple, elm, hemlock, willow (all trees that lose their leaves annually)
• Supports: skunks, squirrels, rabbits, birds, deer, cougars, lynx, wolves, foxes, bears

Boreal (Taiga) Forests

• Largest terrestrial ecosystem (Canada, Northern Europe, Russia)
• Precipitation is primarily snow
• Nutrient poor soil
• Supports: cold-tolerant evergreen trees like pine, spruce and fir
• Supports: woodpeckers, hawks, moose, bear, weasel, lynx, foxes, wolves, deer, hares, chipmunks, bats

Biomes: Marine

Oceans

• Largest of all the biomes - covers the majority of the Earth's surface
• Broken down into different zones:
• Intertidal Zone = where the land and the ocean meet
• In rocky coastal regions this zone is organized vertically
• Highest region supports: algae, mollusks
• High-tide submerged region supports: snails, crabs, sea stars, small fish
• Always submerged region supports: invertebrates, fish, aquatic plants
• In sandy coastal regions less plant life is supported but does support: worms, clams, crabs, birds
• Pelagic Zone = open ocean but at the surface
• Supports: seaweed, fish, sharks, whales, dolphins, plankton
• Light continually decreases until the beginning of the benthic zone
• Benthic Zone = below the pelagic but above the abyssal zone
• Very little light and very cold
• Supports: some seaweed, bacteria, fungi, sponges, anemones, worms, sea stars and fish
• Abyssal Zone = deep ocean
• No light, very cold, high oxygen levels and high pressure
• Supports: invertebrates and fish
• Includes areas where tectonic plates meet and just above hydrothermal vents
• Chemosynthetic bacteria are found in and around hydrothermal vents and act as the autotrophs of the zone

Coral Reefs

• Found in warm, shallow water in the ocean
• Dominant organism is the coral itself - coral is made up of animal polyps and algae
• Supports: microorganisms, invertebrates, fish, urchins, octopi, sea stars

Estuaries

• Found where freshwater streams/rivers meath the mouth of the ocean
• Supports: algae, seaweed, grasses, mangrove trees (in tropical climates)
• Supports: worms, oysters, crabs, birds

Biomes: Desert

Hot and Dry Deserts

• Daily temperatures can range from sub-zero at night to 45°C during the day
• Evaporation rate is higher than rate of rainfall
• This means that when it rains, the rain has evaporated before it hits the ground!
• Often have rocky abiotic components as sand is often blown away
• Supports: ground shrubs, some waxy trees, plants with thick cuticles, plants with specialized stomata opening times, plants with specialized leaves as spines
• Supports: small carnivorous mammals, insects, spiders, reptiles and birds
• Most animals are nocturnal or crepuscular to avoid the heat

Semi-arid Deserts

• Have long dry summers with some rainfall in winter
• Daily temperature ranges from 21-27°C during the day to 10°C at night
• Most organisms are sustained on water from condensation rather than precipitation
• Supports: ground shrubs, plants with spines for leaves or glossy leaves
• Supports: rats, mice, rabbits, skunks, grasshoppers, ants, lizards, snakes, birds

Coastal Deserts

• Gets around 8-13cm/year of rainfall
• Supports plants that have a specialized ability to store water or to shrink/shrivel during dry times without dying
• Supports: toads, insects, coyotes, badgers, owls, eagles, lizards, snakes

Cold Deserts

• Hot summers around 20-30°C but VERY cold winters at sub-zero temperatures
• Summers are short and moist, with long winters with 15-26cm/year of snow
• Supports plants with spiny leaves
• Supports: rabbits, rats, mice, squirrels, badgers, foxes, coyotes, lizards, deer (during the winter)

Biomes: Grassland

Savanna

• Found in warm/hot climates
• Has an annual rainfall of 50-130cm/year
• This rainfall is concentrated to only 6-8 months with severe drought conditions for the remaining months
• Fires are vitally important for maintaining grasses and avoiding succession by shrubs and trees
• Fires = natural disturbance
• Types of savanna:
• Climatic = caused by the climate of the region
• Edaphic = caused by low soil nutrients
• Derived = caused by human activity and sometimes by animal activity (like elephants)
• Supports: grasses, forbes, scattered trees
• Supports: grasshoppers, beetles, mice, lizards, birds, giraffes, zebras, buffalos, kangaroos, snakes, worms, termites, leopards, hyenas, elephants
• Not ALL of these animals are found in all savannas - it is climate and ecosystem specific

Temperate Grassland

• Hot summers, cold winters and has less rainfall than a savanna
• Yearly temperatures can range from -40°C to +40°C
• Supports almost no trees but does support grasses and some flowers
• Supports: gazelles, zebras, rhinoceros, horses, lions, wolves, wild dogs, rabbits, deer, mice, coyotes, foxes, skunks, badgers, sparrows, hawks, owls, spiders, grasshoppers
• Can be broken down further into prairies (tall grasses) and steppes (short grasses)

Biomes: Tundra

Arctic Tundra

• Temperatures range from -40°C to +12°C yearly
• Gets about 15-25cm/year of precipitation
• Contains permafrost
• Permafrost is permanently frozen subsoil
• This makes tundra distinct from deserts
• Supports: shrubs, mosses, grasses, flowers, lichens
• Supports: voles, caribou, hares, squirrels, foxes, wolves, polar bears, falcons, loons, terns, owls, gulls, insects and fish

Alpine Tundra

• Found at high altitude mountains all over the world
• Supports: grasses, dwarf trees, shrubs, heath
• Supports: pika, marmots, goats, sheep, elk, alpine birds, insects