Ecosystems
Climate and the Biosphere
Climate: Refers to the prevailing weather conditions in a particular region.
Dictated by temperature and rainfall.
Influenced by the following factors:
Variations in solar radiation distribution due to the tilt of the Earth as it orbits the sun.
Other effects—topography, proximity to water bodies.
Effect of Solar Radiation
The sun’s rays are more direct at the equator and more spread out nearing the poles.
Tropical regions nearest the equator are warmer than temperate regions farther away.
The Earth is on a slight tilt (23°).
As the Earth orbits, different areas are tilted toward or away from the sun, determining seasons.
The flow of warm and cold air form three large circulation patterns in each hemisphere.
The direction in which the air rises and cools determines the direction of the wind.
At the equator:
The sun heats the air.
Water evaporates: as warm, moist air rises, the moisture is lost as rain.
The greatest amounts of rainfall occur near the equator.
The rising air flows toward the poles
At about 30° north and south latitude, air typically sinks toward Earth’s surface and reheats.
As the dry air descends, it creates high-pressure areas with low rainfall.
The result is the great deserts of Africa, Australia, and the
Americas that are found at this latitude.
At about 60° north and south latitude, the warm air rises and cools, producing a low-pressure area.
Low-pressure areas result in zones of high rainfall.
Between 30° and 60° latitude, a strong wind pattern known as the westerlies occurs in both hemispheres.
• These winds move from west to east.
As a result, the west coasts of the continents at these latitudes are wet.
At latitudes higher than 60°, weaker winds called the polar easterlies blow from east to west in both hemispheres.
Dry air descends at the poles and retains moisture.
The direction of wind patterns, such as the westerlies and easterlies, is affected by the spinning of the Earth about its axis.
Northern Hemisphere: Large scale winds generally move clockwise.
Northeast trade winds blow toward southwest.
Southern Hemisphere: Winds move counterclockwise.
Southeast trade winds blow toward northwest.
Other Effects
Topography: physical features of land.
Mountains
As air blows up the mountain, it rises and cools, causing condensation to occur.
The windward side receives more rain than the leeward side.
This creates a rain shadow on the leeward side, which receives less rain.
As air descends the other side of the mountain, it picks up moisture and produces a dry, sunny environment.
Coasts
During the day, land warms more quickly than ocean, air rises, and cool sea breeze blows off ocean.
At night, land cools faster and breeze blows from the land to the sea.
Monsoon climate
Land heats more rapidly than the waters of the Indian Ocean during the spring.
This difference causes a gigantic circulation of air: warm air rises over the land, and cooler air comes in off the ocean to replace it.
As warm air rises, it loses its moisture, creating a monsoon climate (about six months long): wet ocean winds blow onshore.
During the monsoon season, rainfall is especially heavy on the windward side of hills.
The pattern reverses by November.
Lake Effect
In the winter, arctic winds blowing over the Great Lakes become warm and moisture-laden.
When these winds rise and lose their moisture, snow begins to fall.
Buffalo, New York, gets heavy snowfall due to the lake effect.
Terrestrial Ecosystems
Biome: major type of terrestrial ecosystem.
Characterized by particular climatic conditions and community of plants and animals.
Major biomes characterized by mean annual temperature and mean annual precipitation.
Biomes gradually change from one type to another at borders.
Linked to each other to form biosphere.
Distribution of the biomes and their corresponding communities of organisms is determined by three things:
Climate (affected by solar radiation).
Water.
Defining topographical features.
Biomes change with altitude as they do with latitude due to changes in temperature.
Can see progression of tropical rain forest, temperate forest, coniferous forest, and tundra when ascending latitude in the Northern Hemisphere or ascending a mountain.
Tundra
Tundra biome.
Encircles the arctic region south of polar seas in the Northern Hemisphere.
Very cold and dark most of the year—short growing season, precipitation is minimal (< 20 centimeters/year).
Permafrost prevents water drainage; bogs and pools form in the summer.
Vegetation suitable for short growing season.
Lichens, short grasses, mosses, dwarf shrubs.
Animals—few live all year round.
Ptarmigans, musk ox, migratory birds, caribou, reindeer, and wolves.
Coniferous Forests
Coniferous forests have long, cold, snowy winters with warm and humid summers; found in three locations.
Taiga
northern part of North America and Eurasia.
Vegetation: Cone-bearing trees adapted to the cold climate.
Pine, firs, spruce.
Needles can withstand weight of snow and thick bark.
Understory is limited to mosses and lichens.
Animals—usually near lakes and streams.
Bears, deer, moose, beavers, muskrats, wolves, birds
Montane coniferous forest
a second location of coniferous forest biome.
Near mountaintops just above deciduous forest.
Wolverine and mountain lion located in montane coniferous forest.
Temperate rain forest.
These are found on the western coast of the United States and Canada.
Plentiful rainfall and rich soil have produced some of the tallest conifer trees known.
Coastal redwoods.
Small sections are considered old-growth forest with an average age of more than 150 years old.
Moss and ferns grow on tree trunks.
Temperate Deciduous Forests
South of the taiga in eastern North America, much of Europe, and eastern Asia.
Moderate climate, with relatively high precipitation (75 to 150 centimeters per year).
Well-defined seasons, long growing season (140 to 300 days).
Trees are deciduous because they lose their leaves in fall and regrow them in spring.
Vegetation
Common trees are oak, beech, maple, and other broad-leaf deciduous trees.
The tallest trees form a canopy, receive the most sunlight, and create a shade below.
The understory trees are a layer of trees just below the tallest group.
Shrubs and herbaceous plants grow below the understory layer
Stratification of plant life provides a variety of habitats for insects and birds.
Ground life is plentiful.
Squirrels, rabbits, chipmunks, shrews, and other small herbivores.
Ground birds such as turkeys, pheasants, and grouse.
Beavers, muskrats, bobcats, red foxes, deer, and black bears.
A greater diversity of amphibians and reptiles than in the taiga.
Fruits, nuts, and berries provide winter food.
Tropical Forests
the tropical rain forest is the most common type.
South America, Africa, Indo-Malayan region, regions near the equator.
Uniformly warm temperatures (20 degrees Celsius to 25 degrees Celsius).
Abundant rainfall, minimum of 190 centimeters per year.
Biome with the greatest species diversity.
10-square kilometer area may contain 750 species of trees and 1,500 species of flowering plants.
Complex structure, many levels of life.
Broadleaf evergreen trees grow up to 15 to 50 meters or more.
Some trunks are buttressed; lianas (woody vines) encircle trees.
Animals:
Some live on gthe ground—acas, agouties, peccaries, and armadillos.
Many live in trees.
Insect life is very abundant.
Termites play a role in decomposition of woody plants; ants found everywhere.
Birds—beautiful colors.
Hummingbirds, parakeets, parrots, toucans.
Amphibians and reptiles – well represented.
Many types of frogs, snakes, and lizards.
Primates:
Lemurs and monkeys, which feed on fruits.
Carnivores—big cats.
Jaguars in South America.
Leopards in Africa and Asia.
Many animals and some plants spend their entire life in the canopy.
Epiphytes: plants that grow on other plants.
Have own roots and absorb materials from canopy.
Soil is not as rich as that of temperate deciduous forest.
Nutrients are rapidly recycled.
Removing trees for agriculture causes erosion.
Tropical deciduous forests have wet and dry seasons.
Shrublands
Tend to occur along coasts with dry summers and receive most of their rainfall in winter.
Shrubs with waxy leaves, adapted to arid conditions.
Can quickly regrow after fires.
Excess heat required for some seeds to germinate.
Chaparral is type of Mediterranean shrubland found in California, South Africa, Australia.
Animals include coyotes, jackrabbits, lizards, deer, roadrunners, gophers, and other rodents.
Grasslands
Rainfall is greater than 25 centimeters per year but not enough to support trees.
Natural grasslands have declined because they are now used to grow crops such as wheat, corn, and soybeans.
Grasses are well adapted to a changing environment.
Tolerate some grazing, flooding, drought, and fire.
Growth of grasses is seasonal.
Areas with higher rainfall can support tall grasses.
In drier areas, shorter grasses dominate.
Temperate grasslands
Russian steppes; American pampas; North American prairies.
Bison and pronghorn antelope once were abundant in prairies.
Now, small animals, such as mice, prairie dogs, and rabbits typically live below ground.
Aboveground, hawks, snakes, badgers, coyotes, and foxes feed on the smaller animals.
Savanna
grassland with some trees.
Relatively cool, dry season is followed by a hot, rainy season.
Acacia—a typical savanna tree, sheds its leaves during the dry season.
African savanna:
Great variety and number of large herbivores.
Elephants and giraffes feed on tree vegetation (browsers).
Antelopes, zebras, wildebeests, and rhinoceroses feed on grasses (grazers).
Carnivores include lions, hyenas, cheetahs, and leopards.
Deserts
Usually found at latitudes of about 30 degrees Celsius, in both Northern and Southern Hemispheres.
Annual rainfall less than 25 centimeters due to dry winds.
Hot days (lack of clouds) and cold nights.
Most deserts have a variety of plants.
Succulent, spiny cacti and non-succulent woody shrubs (sagebrush and ocotillo).
Exception: The Sahara has little or no vegetation.
Animals–some adapted to desert environment.
Many are nocturnal, to avoid heat.
Reptiles and insects have waterproof outer coverings to conserve water.
Insects may pass through all stages of development while there is rain.
Reptiles and snakes are typical desert vertebrates.
Other animals include some running birds, rodents, coyotes, and hawks
Aquatic Ecosystems
Two main types:
Freshwater (inland).
Lakes.
Saltwater (usually marine).
Oceans.
Brackish water is a mixture of fresh and salt water.
Coastal ecosystems
Mountain Streams and Rivers
Mountain streams and rivers are bodies of freshwater found in high elevations.
Frozen precipitation at high elevations melts and flows down toward the sea.
These bodies of water are cold and tend to be low in nutrients and biodiversity.
As the water makes its way to lower elevations, it accumulates nutrients and becomes warmer.
Species that can be found in clean mountain streams include mayflies and trout
Lakes
bodies of fresh water.
Classified by nutrient abundance.
Oligotrophic (nutrient-poor) lakes – small amounts of organic matter.
Low productivity.
Eutrophic (nutrient-rich) lakes – plentiful amounts of organic matter.
High productivity due to location near naturally nutrient-rich regions.
May be enriched by agricultural or urban runoff.
Eutrophication can be caused by large inputs of nutrient.
Estuaries:
Estuary: a partially enclosed body of water where fresh and salt water mix.
Coastal bays, tidal marshes, fjords, some deltas, and lagoons.
Associated with salt marshes, mudflats, mangroves. Abundance of nutrients, but rapid changes in salinity.
Feeding grounds of many birds, fish, shellfish. “Nurseries” of the sea.
Half of all marine fish mature in estuaries.
Wetlands
areas that hold some amount of water during part of the year; classified by their vegetation.
Marshes:
Frequently or continually inundated by water.
Rushes, reeds, and other grasses provide excellent habitats for waterfowl and small mammals.
One of the most productive ecosystems on Earth.
Swamps:
Dominated by either woody plants or shrubs.
Common swamp trees include cypress, red maple, and tupelo.
The American alligator is a top predator.
Bogs:
Characterized by acidic waters, peat deposits, and sphagnum moss.
They receive most of their water from precipitation and are nutrient-poor.
Several species of plants thrive in bogs.
Cranberries, orchids, and insectivorous plants such as Venus flytraps and pitcher plants.
Moose are inhabitants of bogs in the northern United States and Canada.
Humans have historically channeled and diverted rivers and filled in wetlands.
These activities degrade ecosystems, cause seasonal flooding, and eliminate food and habitats for wildlife and natural protection.
Wetlands purify waters by filtering them and by diluting and breaking down toxic wastes and excess nutrients.
Wetlands directly absorb storm waters and overflow from lakes and rivers, protecting farms, cities, and towns from the devastating effects of floods.
Federal and local protection laws have been enacted as more people recognize their value.
Seashores
Rocky or sandy and are constantly bombarded by the sea.
Littoral zone: between high and low tidal marks – divided into three zones.
Upper portion – barnacles are attached tightly to stone.
Midportion – brown algae known as rockweed may overlie the barnacles.
Lower portion – oysters and mussels are attached to the rocks by filaments.
Limpets and periwinkles.
Below the littoral zone, macroscopic seaweeds anchor to the rocks.
Animals that live on sandy shores cannot attach to shifting and unstable surfaces.
They instead bury themselves underground.
Some remain underground, others surface at night to feed.
Ghost crabs and sandhoppers feed at night at low tide.
Sandworms and sand (ghost) shrimp remain within the burrows and feed on detritus.
Oceans
Cover approximately 75% of the Earth.
Have a major role in redistributing heat in the biosphere.
Air takes on the temperature of the water below, and then warm air moves from the equator to the poles.
Influence the wind patterns.
Currents are caused by wind blowing steadily across great bodies of water.
Friction from moving air drags the water along.
The momentum of wind and moving water is the current.
Ocean currents eventually strike land, causing them to move in circular paths.
Northern Hemisphere:
Currents circulate clockwise.
As currents flow, they move warm water from the equator to the poles.
The Gulf Stream brings tropical Caribbean water to the east coast of North America and higher latitudes of western Europe.
Without the Gulf Stream, Great Britain would be as cold as Greenland.
Southern Hemisphere:
Currents circulate counterclockwise.
The Humboldt Current circulates cold, nutrient-rich water northward along the west coast of South America.
An upwelling occurs when cold offshore winds cause nutrient-rich waters to rise and take the place of warm, nutrient-depleted water.
Waters enriched by upwelling support fisheries of Peru and Chile.
When the Humboldt Current is not as cool, stagnation occurs, and fisheries decline
Pelagic Division
Organisms in oceans are placed into either the pelagic division (open waters) or the benthic division (ocean floor).
Neritic province–shallow waters over continental shelf.
Oceanic province – open water, several depth zones.
Neritic Province
Abundant sunlight and inorganic nutrients allow a large concentration of organisms.
Phytoplankton provide food for zooplankton and small fish.
The small fish are food for larger fish. Coral reefs.
Coral reefs are areas of high biological abundance in shallow, nutrient-poor, tropical waters.
They include calcareous red and green algae and colonies of stony corals.
Many corals contain symbiotic zooxanthellae
Coral reefs
Reefs are densely populated with life.
The crevices and caves provide shelter for filter feeders (sponges, sea squirts) and scavengers (crabs and sea urchins).
Many small fish live there; some feed directly on corals, others feed on plankton or detritus.
Larger fish, such as snapper, feed on smaller fish.
Top predator fish include the shark, barracuda, and moray eel.
Oceanic Province
This province lacks the inorganic nutrients of the neritic province, but sunlight is available.
Has a lower concentration of phytoplankton.
Epipelagic zone: photosynthesizers are eaten by zooplankton, which are eaten by herring and bluefishes, which are, in turn, eaten by larger mackerels, tunas, and sharks.
Whales and other mammals also occur here.
Mesopelagic zone: carnivores such as squids and lantern fish.
Bathypelagic zone: complete darkness.
Carnivores and scavengers.
Benthic Division 1
The benthic division includes organisms that live in or on the oceanic soil.
Sublittoral zone—continental shelf.
Seaweed, algae, clams, worms, crabs, sea stars.
Bathyal zone—continental slope.
Organisms depend on detritus that falls from above.
Abyssal zone—abyssal plain.
High pressure and cold water.
Many invertebrates live at soil-water interface.
Sea lilies, sea cucumbers, tube worms.
The flat abyssal plain is interrupted by underwater mountain chains called oceanic ridges.
Along axes of the ridges, crustal plates spread apart.
Molten magma from Earth’s core rises.
Seawater percolates through hydrothermal vents. Seawater is heated, causing sulfate to react with water and form hydrogen sulfide (H2S).
Free-living or mutualistic chemoautotrophic bacteria use electrons from (H2S) to reduce bicarbonate to organic compounds to support this ecosystem.
Includes huge tube worms and clams