Chapter 26 Outline and Terms

26.1. Climate and the Biosphere

A. Global Air and Water Circulations

1. Both global climate and local weather create living conditions for organisms.
2. Biomes are major communities characterized by certain climatic conditions and their own mix of species.
3. Biomes are dependent upon four major factors.
   1. A spherical earth causes variation in received solar radiation.
   2. The tilt of the earth's axis as it rotates about the sun causes seasonal change.
   3. Land masses and oceans are distributed unevenly.
   4. Topography (landscape) including mountain ranges, affects local climate.

B. Air Circulation

1. Earth is a sphere; therefore the sun's rays are more direct near the equator and spread out near the poles.
2. Tropics are therefore warmer than temperate areas. (Fig. 26.1a)
3. Tilt of the earth's axis as it rotates about the sun causes one pole to be more directly exposed to sunlight.
4. Cold air is heavy and sinks; hot air is lighter and rises.
   1. If the earth was standing still, equatorial air would rise and move toward the poles.
   2. This would replace heavy polar air that sinks and flows toward the equator, now a low pressure area.
   3. This would produce high winds moving toward the poles and surface winds moving toward equator.
5. Earth's Rotation Has an Effect
   1. Wet equatorial air loses its moisture as it rises and cools near the equator.
   2. By 30^o north, the descending air reheats and is dry; this is a zone of deserts.
   3. From equator to 30^o north and south, surface winds blow from east-southeast in the Southern Hemisphere and from the east-northeast in the Northern Hemisphere making east coasts wet.
   4. Between 30^o and 60^o north and south, strong winds called the westerlies blow from west to east.
   5. The west coasts of continents in these latitudes are wet as is the Pacific Northwest.
   6. Weaker polar easterlies blow from east to west between 60^o north or south and the respective poles.
   7. Earth's rotation and continents and oceans alter three circulation cells between the equator and poles.
   8. The spinning of the earth shifts winds from directly north-south toward east or west.

C. Effects of Topography

1. Topography is the physical features or "lay" of the land.
2. Mountains cause rain and rain shadows
   1. Air blowing up over a mountain range rises and cools; windward side receives more rainfall.
   2. The leeward side of the mountain range receives dry air; it is in a rain shadow. (Fig. 26.3)
      1. Hawaiian Islands experience 750 cm of rain on windward side, only 50 cm in rain shadow.
      2. Western side of Sierra Nevada Mountains is lush; eastern side is a semi-desert.
3. Coastal Breezes
   1. Since land heats up and cools down faster than oceans, it causes a daily pattern.
   2. In the day, land heats up and warm air rises; cool sea breezes blow inland to replace the rising air.
   3. At night, the land cools first and cold air sinks and blows out to sea.
4. Monsoon Climates
   1. India and south Asia climate generates wet ocean winds for almost half the year.
   2. The land heats more rapidly than the waters of the Indian Ocean during spring.
   3. The difference in temperature causes a gigantic circulation of air with warm air rising and cooler air continuously coming in off the ocean to replace it.
   4. As the warm air rises, it loses its moisture and the monsoon season begins.
5. The "Lake Effect"
   1. Arctic winds blowing across the Great Lakes become warm and moisture laden.
   2. When these winds rise and lose their moisture, snow falls.

26.2. Biomes of the World

A. The biosphere is be divided into large biogeographic units called biomes.

1. Biomes have a particular mix of plants and animals adapted to live under certain environmental conditions.
2. Average temperature and rainfall influences where the different biomes are found on the surface of the earth. (Fig. 26.4a)
3. Climate is a principle determinant of the distribution of biomes. (Fig. 26.4b)
4. A latitude temperature gradient is also seen when we consider altitude; the rain forest-deciduous forest- coniferous forest-tundra sequences are also seen when ascending a mountain. (Fig. 26.5)
   1. The mountain coniferous forest is a montane coniferous forest.
   2. The tundra near the peak is an alpine tundra.

B. Soil Types

1. Soil is the uppermost layer of the lithosphere.
2. Soil originates with the weathering of bedrock and the reorganization of this material by water, plants, animals and detritivores.
3. Humus is the decomposed component of soil.
4. Topsoil takes thousands and even millions of years to form; soil erosion is a serious loss of resources.
5. Soil Particle Sizes and Properties
   1. Sand is a large particle that forms large pores for fast water drainage.
   2. Silt is intermediate in particle size and in pore properties.
   3. Clay is very fine, drains slowly, and leaves no pore spaces for roots to get air for cell respiration.
   4. Loam is a mixture of sand, silt, and clay and when mixed with humus, has the best properties.
6. Soil Horizons
   1. A horizon is uppermost topsoil; it contains litter and humus but soluble chemicals have been leached out.
   2. B horizon has little or no organic matter but contains inorganic nutrients leached from the A horizon above.
   3. The C horizon is weathered or shattered rock.
7. Grassland soil has a deep A horizon built up from decaying grasses over many years with little leaching into the B horizon.
8. Forest soils have enough inorganic nutrients in the A and B horizons to allow root growth.
9. In tropical rain forests, the A horizon is very shallow and the B horizon is deeper due to more leaching; since the topsoil lacks nutrients, it can only support crops for a few years.

26.3. Terrestrial Biomes

A. Tundra (Fig. 26.7)

1. Arctic tundra encircles the earth south of the ice-covered polar seas in the Northern Hemisphere.
2. Arctic tundra covers 20% of earth's land surface; it is cold and dark much of the year.
3. Tundra receives 20 cm of rainfall annually; melting snow provides water during summer.
4. Only the topmost layer of earth thaws; permafrost beneath is always frozen.
5. Trees are not found in the tundra because
   1. the growing season is too short,
   2. their roots cannot penetrate the permafrost, and
   3. they cannot become anchored in the boggy soil of summer.
6. In summer, the ground is covered with sedges and short-grasses with patches of lichens and mosses.
7. Dwarf woody shrubs flower and seed quickly while there is sunlight for photosynthesis.
8. A few larger animals adapted to cold live in tundra year-round (e.g., lemming, ptarmigan, and musk-ox).
9. During summer, tundra contains many insects and migratory animals (e.g., shore birds, waterfowl, caribou, reindeer, and wolves).

B. Coniferous Forests (Fig. 26.8)

1. Taiga is coniferous forest extending across northern Eurasia and North America.
2. Near mountain tops, it is called a montane coniferous forest.
3. On Pacific Coast from Canada down to California, it is called a temperate rainforest.
4. Contains great stands of spruce, fir, hemlock, and pine; these trees have thick protective leaves and bark.
5. The needle-like leaves can withstand the heavy weight of snow.
6. There is a limited understory of plants; the floor is covered by low-lying mosses and lichens beneath the layer of needles.
7. Birds harvest the seeds of conifers; bears, deer, moose, beaver and muskrat live around the cool lakes and streams.
8. Major carnivores include wolves, wolverine, and mountain lion.
9. The temperate rain forest along the Pacific Coast has the largest trees in existence, some at 800 years.

C. Temperate Deciduous Forests (page 451) (Fig. 26.9)

1. These are found south of taiga in eastern North America, eastern Asia, and Europe.
2. Climate is moderate with a relatively high annual rainfall (75-150 cm).
3. Seasons are well-defined with a growing season that ranges between 140 and 300 days.
4. Trees of a deciduous forest (e.g., oak, beech, and maple) have broad leaves which they lose in the fall and grow again in the spring.
5. In temperate deciduous forest, enough sunlight penetrates the canopy to support a well-developed understory composed of shrubs, a layer of herbaceous plants, and a ground cover of mosses and ferns.
6. Stratification beneath the canopy provides a variety of habitats for insects and birds.
7. Deciduous forest contains many rodents that provide food for bobcats, wolves, foxes.
8. Deciduous forest also contains deer and black bears.
9. Compared to taiga, winters are milder and allow many amphibians and reptiles to survive.

D. Tropical Forests (page 452)

1. Tropical rain forests are found in South America, Africa, and the Indo-Malayan region near the equator.
2. Climate is warm (20-25^oC) and rainfall plentiful (minimum of 190 cm per year).
3. This is probably the richest biome, both in number of species diversity and in total biomass.
4. Tropical rain forest has a complex structure, with many levels of life. (Fig. 26.10)
5. Although there is animal life on the ground (e.g. pacas, agoutis, peccaries, and armadillos), most animals live in the trees and many spend their entire life in the canopy.
6. Insects are abundant in tropical rain forests; the majority have not been identified.
7. Termites are critical in decomposition of wood.
8. Various birds tend to be brightly colored.
9. Amphibians and reptiles are represented by many species of frogs, snakes, and lizards.
10. Lemurs, sloths and monkeys feed on fruits.
11. The largest carnivores are cats (e.g., jaguars in South America and leopards in Africa and Asia).
12. Epiphytes are air plants that grow on other plants.
    1. They have roots of their own to absorb moisture and minerals leached from the canopy.
    2. Others catch rain and debris in hollows of overlapping leaf bases.
    3. Common epiphytes are related to pineapples, orchids and ferns.
13. Tropical forests in India, Southeast Asia, West Africa, West Indies, Central and South American are seasonal.
    1. They have deciduous trees that shed leaves in the dry season; layers of undergrowth are below.
    2. Certain of these forests contain elephants, tigers and hippopotami.
14. A year-long growing season means productivity is high.
15. The warm, moist climate that supports high productivity also promotes rapid recycling of litter.
16. Consequently soil is relatively poor because nutrients are tied up in biomass; this makes poor agricultural soils.

E. Shrubland (page 454)

1. Shrubland is dominated by shrubs with small but thick evergreen leaves coated with a thick, waxy cuticle, and with thick underground stems that survive dry summers and frequent fires.
2. Shrubland is found in South America, western Australia, central Chile, around the Mediterranean Sea.
3. Dense shrubland in California, where the summers are hot and very dry, is chaparral. (Fig. 26.12)
   1. This Mediterranean-type shrubland lacks an understory and ground litter and is highly flammable.
   2. Seeds of many species require heat and scarring action of fire to induce germination.
4. West of the Rocky Mountains is a cold desert region dominated by sagebrush and dependent birds

F. Grasslands

1. Grasslands occur where rainfall is greater than 25 cm but is insufficient to support trees. (Fig. 26.13)
2. Natural grasslands once covered over 40% of the earth's land surface.
3. In temperate areas with rainfall between 10 and 30 inches a year, grassland is the climax community; it is too wet for desert and too dry for forests.
4. Most grasslands now grow crops, especially wheat and corn.
5. Grasses are the dominant plant; grazing and burrowing species are dominant animal life.
6. Extensive root systems of grasses allow them to recover quickly from grazing, flooding, drought, and sometimes fire.
7. Temperate grasslands include Russian steppes, South American pampas, and North American prairies.
8. Tall-grass prairie occurs where moisture is not sufficient to support trees.
9. Short-grass-prairie survives on less moisture and is between a tall-grass prairie and desert.
10. Animal life includes mice, prairie dogs, and rabbits and the animals that feed on them, hawks, snakes, badgers, coyotes, and foxes.
11. Prairies once contained large herds of buffalo and pronghorn antelope.
12. Savanna is tropical grassland that contains some trees.
    1. Savanna contains the greatest variety and numbers of herbivores (e.g., antelopes, zebras, wildebeests, water buffalo, rhinoceroses, elephants, and giraffes).
    2. This supports a large population of carnivores (e.g., lions, cheetahs, hyenas, and leopards). (Fig. 26.14)
    3. Any plant litter not consumed by grazers is attacked by termites and other decomposers.

G. Deserts (page 456)

1. Deserts usually occur at latitudes about 30^o north or south. (Figs. 26.4 and 26.15)
2. Deserts have an annual rainfall of less than 25 cm because winds pick up moisture and ascend.
3. Lacking cloud cover, desert days are hot and nights are cold.
4. Sahara and a few other deserts are nearly devoid of vegetation.
5. Most have a variety of plants, all adapted to heat and scarcity of water (e.g., succulents).
6. Animal life includes many insects, reptiles such as lizards and snakes, running birds (e.g., roadrunner), rodents (e.g., kangaroo rat), and a few larger birds and mammals such as hawks and coyotes.

26.4. Aquatic Biomes

A. Classifications

1. Aquatic biomes are classified as fresh water or saltwater (marine).
2. Wetlands near the sea have mixed fresh and salt water and are brackish.
3. Aquatic biomes share nutrients and biogeochemical cycles.
4. Evaporated water precipitates and flows through lakes and ponds, streams and rivers, and groundwater.
   1. The top of the saturation zone defines the water table.
   2. Groundwater sometimes occurs in underground layers called aquifers.
5. Human Activities
   1. Wandering streams are often channelized into straight channels; eliminating storage for flood control.
   2. Elimination of wetlands removes unique habitat for fish, waterfowl and other wildlife.
   3. Wetlands also filter toxic wastes.
6. Freshwater communities are found in: lakes, rivers, and streams.

B. Lakes

1. Lakes are freshwater bodies classified by nutrient status.
   1. Oligotrophic (nutrient-poor) lakes have low organic matter and low productivity.
   2. Eutrophic (nutrient-rich) lakes are highly productive from natural nutrients or agricultural runoff.
   3. Eutrophication occurs when added nutrients change an oligotrophic lake to eutrophic.
2. In a temperate zone, deep lakes are stratified in summer and winter.
   1. Epilimnion is the surface layer warmed from solar radiation; it soon becomes nutrient-poor but photosynthesis keeps oxygen levels high.
   2. At the thermocline, there is an abrupt drop in temperature.
   3. The hypolimnion is the lower cold region; it becomes depleted in oxygen but is nutrient rich from detritus falling from above.
   4. The less dense epilimnion floats on the heavier cold hypolimnion; this prevents mixing.
3. Fall and Spring Overturns
   1. In the fall, the upper epilimnion waters become cooler than the hypolimnion.
   2. This causes the surface water to sink and deep water to rise.
   3. The fall overturn continues until the temperature is uniform.
   4. In winter, ice forms on top because ice is lighter; this provides an insulating cover and organisms can live though a harsh winter in this moderate water.
   5. In spring, the ice melts and the cooler water on top sinks below the warmer water on the bottom.
   6. After the spring overturn, water returns to a more uniform temperature and sun warms the surface.
   7. Fish and other aquatic life are adapted to the strata and seasonal changes.

C. Life Zones

1. Plankton includes freshwater and marine microscopic organisms that freely drift in fresh or salt water.
2. Phytoplankton are the photosynthetic plankton, including algae.
3. Zooplankton are animals that feed on phytoplankton.
4. Littoral zone is shallow and closest to shore; plants root in this zone and harbor some animals.
5. Limnetic zone is open sunlit layer of body of a lake; it contains plankton, a few insect larvae, and fish.
6. Profundal zone is portion of a lake below any significant sunlight penetration; contains zooplankton and fishes that feed on debris that falls from above.
7. Benthic zone is soil-water interface with bottom-dwelling organisms; includes worms, mollusks, crustaceans.

D. Coastal Communities

1. The mouth of a river develops into
   1. a salt marsh in temperate zones, and
   2. a mangrove swamp in subtropical zones.
2. Silt carried by rivers forms mudflats.
3. Estuary is a partially enclosed body of water at the end of a river where freshwater and seawater mix.
   1. Fewer organisms are tolerant of the mix of fresh river water and salty tidal water.
   2. For organisms suited to rapid changes in salinity, estuaries provide abundant nutrients.
   3. Estuaries are a nutrient trap since nutrients are
      1. delivered by the river
      2. brought in from the sea by tides
      3. released from decaying vegetation. (Fig. 26.22)
   4. Estuaries are a nursery for spawning and rearing of over half of marine fishes.
4. Seashores are constantly bombarded by tidal seas.
   1. Littoral zone is covered and uncovered daily by tides.
   2. Upper littoral is covered by barnacles.
   3. Midportion harbors brown algae that may overlie barnacles.
   4. Lower portion has oysters and mussels attached to rock and various snails.
   5. Below the littoral, seaweeds are main photosynthesizers anchored to rocks by holdfasts.
   6. Sandy beaches have no anchor holds; therefore beach organisms are burrowing or tube-living.

E. Oceans

1. Moisture that evaporates into the air carries the heat used to evaporate it with it.
2. Water is warm at the equator and cold at the poles due to the distribution of the sun's rays. (Fig. 26.1a)
3. Air takes on the temperature of the water below and warm air moves from the equator to poles.
4. Therefore, oceans make winds blow.
5. Oceans hold heat or remain cool longer than land masses.
6. Winds generate ocean currents due to friction at the ocean surface.
7. Since ocean currents are bounded by land, they move in a circular path, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
8. Ocean currents take heat from the equator to the polar regions.
   1. Gulf Stream brings tropical Caribbean water to east coast of North America and upper western Europe.
   2. Without the Gulf Stream, Great Britain would be as cold as Greenland.
   3. A major Atlantic ocean current warms the eastern coast of South America.
   4. The Humboldt Current in the Pacific flows toward the equator off the west coast of South America.
9. Upwellings occur when cold nutrient-rich water rises to supplant warm nutrient-poor water.
   1. Humboldt Current brings rich nutrients north; uprising that occurs near Christmas is "El Nino."
   2. This supports rich marine life and the fisheries of Peru and northern Chile.
   3. Seabirds deposit droppings on land (guano) where it is a major source of phosphorus mining.
   4. Failure of El Nino results in stagnation, poor fishing, and global climate pattern changes.

F. Pelagic division includes the neritic and oceanic provinces.

1. Neritic province lies over the continental shelf.
   1. This contains a greater concentration of organisms than in the oceanic province.
   2. It is a more productive part of the ocean because of the concentration of sunlight and nutrients.
   3. It provides base of food web leading to commercially valuable fishes (e.g., herring, cod, and flounder).
2. The oceanic province lies over the continental slope and abyssal plane.
   1. Epipelagic zone extends from the surface to maximum depth photosynthesis significantly occurs.
      1. It does not have a high concentration of phytoplankton because it lacks nutrients.
      2. However, the numbers of producers in this zone still support a large assembly of zooplankton, which support large numbers of other marine organisms, when the entire ocean is considered.
      3. Epipelagic animals include mackerels, tunas, and sharks.
   2. Mesopelagic zone extends below maximum depth at which photosynthesis significantly occurs.
      1. Zone is dominated by carnivores adapted to absence of light (e.g., luminescent shrimps, squids, and fishes).
      2. Organisms tend to be translucent or red colored.
   3. Bathypelagic zone is in absolute darkness except for occasional flash of bioluminescent light.
      1. Animals are carnivores and scavengers.
      2. This level supports a variety of strange carnivores.

G. Benthic Division

1. Benthic division includes organisms that live on or in the soil of the ocean floor, including continental shelf, continental slope and abyssal plain. (Fig. 26.25)
2. The sublittoral zone is located on the continental shelf up to the low tide mark on the coast.
   1. It supports a mixed food web with seaweeds and filter-feeding organisms as the first trophic level.
   2. The seaweeds comprise the first trophic level for a grazing food web; the detritivores (e.g., clams and worms) comprise the first trophic level for a detrital food web.
   3. Starfishes, lobsters, crabs, brittle stars, and some bottom-dwelling fish occupy the upper trophic levels.
3. Bathyal zone is located on continental slope and extends through mesopelagic and bathypelagic depths.
   1. It contains a detrital food web with detritivores (e.g., clams and worms) as the first trophic level.
   2. Again, starfishes, crabs, brittle stars, and some bottom-dwelling fish occupy the upper trophic levels.
4. Abyssal zone is located on and immediately above the abyssal plane.
   1. This is a region of extreme cold and intense pressure.
   2. It contains a detrital food web in which the detritivores (e.g., sponges, worms, tubeworms, sea cucumbers, sea lilies, and sea urchins) comprise the first trophic level.
   3. Starfishes, crabs, brittle stars, and some bottom-dwelling fish occupy the upper trophic levels.
5. Hydrothermal vents are areas where seawater percolates through cracks.
   1. The water is heated to about 350^o C.
   2. This causes sulfate to react with water for form hydrogen sulfide (H₂S).
   3. Chemosynthetic bacteria obtain energy by oxidizing hydrogen sulfide.
   4. These communities are not based on light energy but support huge tube worms and clams.

H. Coral Reefs

1. Coral reefs are a formation composed of the calcium carbonate skeletal remains of stony corals and carbonaceous red and green algae.
2. Coral reefs occur in shallow, warm, tropical regions and just below the water surface.
3. They are densely populated with diverse animal life. (Fig. 26.26)
4. A coral reef community consists of colonies formed by budding.
5. Zooanthellae are microscopic algae housed in the coral.
6. Corals feed at night and the photosynthetic algae feed at day in a mutualistic relationship.
7. Closely-related sea anemones are important coral inhabitants.
8. Numerous crevices and caves provide shelter for filter feeders (e.g., sponges, sea squirts, and fan worms) and for scavengers (e.g., crabs and sea urchins).
9. Barracuda, moray eel and sharks are top predators. (Fig. 26.26b)
10. Coral reefs are affected by overfishing and pollution.
11. Great Barrier Reef of Australia is threatened by an overabundance of crown-of-thorns starfish that is normally controlled by the giant triton, which is recently diminishing.