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Biology

Sylvia S. MaderMichael Windelspecht

Chapter 46

Major Ecosystems

of the Biosphere

Lecture Outline

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Outline

  • 46.1 Climate and the Biosphere
  • 46.2 Terrestrial Ecosystems
  • 46.3 Aquatic Ecosystems

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46.1 Climate and the Biosphere

  • Climate
    • Prevailing weather conditions in a region
    • Determined primarily by temperature and rainfall
    • Influenced by a multitude of factors including latitude, tilt of the earth’s axis, topography, and whether a body of water is nearby
  • Solar radiation
    • Direct at the equator
    • Tilt of the earth causes one pole or the other to be angled toward the sun.
  • Daily rotation of the earth on its axis affects precipitation and winds.

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Climate and the Biosphere

  • Effect of Solar Radiation
  • Solar radiation
    • Direct at the equator, but indirect at the poles
    • Tilt of the earth causes one pole to be closer than the other to the sun.
      • Accounts for the seasons that occur in all parts of the Earth except the equator
    • At the equator, warm, moist air rises and loses its moisture as it cools in the form of rain.
    • Rising air moves toward the poles, but at 30 degrees north and south latitude it cools and sinks towards the earth’s surface.
      • Creates areas of high pressure with little rainfall
        • Great deserts of Africa, Australia, and the Americas

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Climate and the Biosphere-1

  • Effect of Solar Radiation (cont’d)
    • At 60 degrees north and south latitude, warm air rises and cools, producing an area of low pressure with high rainfall.
      • Great forests of the temperate zone
    • Rotation of the earth affects precipitation and winds.
      • In the Northern Hemisphere these winds bend clockwise.
      • In the Southern Hemisphere these winds bend counterclockwise.
      • Doldrums occur at the equator.
        • Regions of calm winds

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Distribution of Solar Energy

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Global Wind Circulation

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Climate and the Biosphere-2

  • Topography
    • The physical features of the land
    • Consider a coastal mountain range
      • Windward side of the mountain
        • Receives more rainfall than the leeward side
        • Rising winds
        • Releases moisture
      • Leeward side
        • Receives less rainfall than the windward side
        • Subsiding dry winds
        • Evaporates existing water and rarely rains
        • Creates a rain shadow

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Formation of a Rain Shadow

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Climate and the Biosphere-3

  • Topography
    • Monsoon climate
      • Ocean winds blow onshore for almost half the year.
      • Land heats more rapidly than the water, which causes an enormous circulation of air.
      • Warm air rises over land and is replaced by cooler ocean air.
        • As the air rises, it loses its moisture and the monsoon season begins.

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46.2 Terrestrial Ecosystems

  • Biome
    • Major terrestrial ecosystem characterized by climate and geography
    • Has a particular mix of plants and animals adapted to living under certain environmental conditions
    • Tends to repeat wherever temperature and precipitation are the same
    • Supports characteristic types of animals, although many migrate from one biome to another

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Biome Pattern of Temperature�and Precipitation

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Distribution of Biomes

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Terrestrial Ecosystems

  • Biome (cont’d)
    • Climate and biomes change with increasing or decreasing latitude and altitude.
      • Traveling from the equator to the North Pole, you observe tropical rain forests, followed by a temperate deciduous forest, a coniferous forest, and tundra.
        • A similar sequence is seen when ascending a mountain.

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Climate and Biomes

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Terrestrial Ecosystems-1

  • Tundra
    • Arctic Tundra – Encircles Earth just south of ice-covered polar seas in Northern Hemisphere
    • Covers 20% of Earth’s land surface
    • Permafrost layer never thaws
    • Trees are not found in the tundra.
      • The growing season is too short.
      • Roots cannot penetrate permafrost.
      • Roots cannot become anchored in shallow boggy soil.

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The Tundra

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Terrestrial Ecosystems-2

  • Coniferous Forests
    • Found in the taiga, near mountaintops, and along the Pacific Coast of North America
    • Taiga typifies coniferous forest with cone-bearing trees.
      • Trees are well adapted to cold.
      • Leaves and bark have thick covering.
      • Needle-like leaves can withstand weight of heavy snowfall.
    • Temperate Rainforest (old-growth forest) of Pacific Northwest
      • Evergreen forest
      • Tallest conifers in existence
        • Old-growth forest

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The Taiga

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Terrestrial Ecosystems-3

  • Temperate Deciduous Forests
    • Found south of taiga in eastern North America, eastern Asia, and much of Europe
    • Moderate climate
      • Relatively high rainfall
      • Four well-defined seasons with long growing seasons
    • The tallest trees form a canopy.
    • Ground-life is plentiful.

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Temperate Deciduous Forest

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Terrestrial Ecosystems-4

  • Tropical Forests
    • Tropical rainforests are found in equatorial regions.
      • Warm weather and plentiful rainfall
      • Complex structure with forest floor, understory, and canopy
      • Most animals live in trees.
        • Abundant insect life
      • Epiphytes grow in many areas.
        • Example: Bromeliads (pineapples), orchids, and ferns
      • Soils are nutrient-poor.
        • Rapid recycling of nutrients
        • Productivity high

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Levels of Life in a Tropical Rain Forest

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Representative Animals of the�Tropical Rain Forests of the World

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Terrestrial Ecosystems-5

  • Shrublands
    • Tend to occur along coasts that have dry summers and wet winters
      • Shrubs are adapted to withstand arid conditions.
      • Dense shrubland in California is known as chaparral.
        • Lacks an understory and ground litter
        • Highly flammable

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Terrestrial Ecosystems-6

  • Grasslands
    • Occur where annual rainfall is greater than 25 cm, but generally insufficient to support trees
    • Grasses are well adapted to changing environment.
    • Temperate grasslands have cold winters and hot, dry summers.
    • Savannas have a cool, dry season and a hot, rainy season.

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Temperate Grassland

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The Savanna

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Terrestrial Ecosystems-7

  • Deserts
    • Usually found at latitudes of about 30° in both hemispheres
      • Deserts cover nearly 30% of Earth’s land surface.
      • Descending winds lack moisture.
      • Annual rainfall is less than 25 cm.
      • There is a large temperature differential between day and night.
      • Lack of cloud cover causes hot days.
      • The nights are cold because heat escapes easily into the atmosphere.

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The Desert

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46.3 Aquatic Ecosystems

  • Aquatic ecosystems are classified as
    • Freshwater (inland) or
    • Saltwater
    • Brackish water is a combination of both.
  • Wetlands are areas that are wet for at least part of the year.
    • Marshes – frequently or continually inundated by water
    • Swamps – dominated by woody plants or shrubs
    • Bogs – characterized by acidic waters, peat deposits, and sphagnum moss

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Freshwater and Saltwater Ecosystems

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Aquatic Ecosystems

  • Lakes
    • Bodies of water classified by nutrient status
      • Oligotrophic – Nutrient-poor
      • Eutrophic – Nutrient-rich
      • Oligotrophic lakes can become eutrophic lakes through the process of eutrophication.
        • Process by which a body of water receives a large input of nutrients

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Types of Lakes

a: © Roger Evans/Photo Researchers, Inc.; b: © The McGraw-Hill Companies, Inc. Pat Watson, photographer

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Aquatic Ecosystems-1

  • Lakes (cont’d)
    • In temperate zones, deep lakes are stratified in the summer and winter and have distinct vertical zones.
      • In summer, lakes have three layers that differ in temperature.
        • Epilimnion – surface layer (warm water)
        • Thermocline – middle layer (cooler than epilimnion)
        • Hypolimnion – bottom layer (cold)
      • The warmer, less dense water of the epilimnion floats on top of the colder, denser water of the thermocline, which floats on top of the hypolimnion.

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Aquatic Ecosystems-2

  • Lakes (cont’d)
    • Fall overturn
      • Epilimnion water becomes cooler than the water in the hypolimnion.
        • Causes the surface water to sink and deep water to rise
        • Process continues until temperature is uniform throughout the lake.
    • Spring overturn
      • As ice melts, cooler water on top sinks below warmer water on the bottom.
        • Temperature is uniform throughout lake.
          • Thermal stratification occurs when the surface waters absorb solar radiation.

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Lake Stratification in a Temperate Region

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Aquatic Ecosystems-3

  • Life Zones
    • Plankton
      • Free-drifting microscopic organisms
      • Important community in fresh water and salt water ecosystems
        • Phytoplankton – Photosynthetic algae
          • Producer base of the lake ecosystem
        • Zooplankton – Tiny animals that feed on the phytoplankton
    • Life Zones
      • Littoral zone – Closest to shore
      • Limnetic zone – Sunlit body of the lake
      • Profundal zone – Below light penetration
      • Benthic zone – Sediment at soil-water interface

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Zones of a Lake

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Aquatic Ecosystems-4

  • Coastal Ecosystems
    • Estuary
      • Portion of the ocean where fresh water and seawater meet and mix
        • Mudflats, mangrove swamps, and rocky shores
      • Organisms must be able to adapt to changing salinity and constant mixing of waters.
      • Nearly two-thirds of all marine fishes and shellfish require development in estuaries.
        • Nursery of the sea

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Aquatic Ecosystems-5

  • Coastal Ecosystems
    • Rocky and sandy shores
      • Constantly bombarded by the sea
      • Intertidal zone
        • Lies between high- and low-tide marks
        • Many attached organisms

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Coastal Ecosystems

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Aquatic Ecosystems-6

  • Oceans
    • Euphotic Zone (shallow ocean waters)
      • Contain a greater concentration of organisms than the rest of the sea
    • Coral reefs
      • Located just below the surface in shallow, warm, tropical waters
      • Densely populated with life
      • Provide a home for microscopic algae called zooxanthellae
        • Mutualistic relationship between algae and coral

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Ocean Ecosystems

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Aquatic Ecosystems-7

  • Oceans (cont’d)
    • Pelagic Zones
      • Epipelagic Zone
        • Lacks inorganic nutrients
        • Does not have as high a concentration of phytoplankton as shallow areas
      • Mesopelagic Zone
        • Carnivores
        • Absence of light
        • Zooplankton, invertebrates, and fish migrate to surface to feed at night.
      • Bathypelagic Zone
        • Complete darkness except for bioluminescent light
        • Carnivores and scavengers

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Ocean Inhabitants

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Aquatic Ecosystems-8

  • Oceans
    • Abyssal Plain
      • High pressure and extreme cold
      • Organisms are dependent on debris sinking down from above.
      • Interrupted by oceanic ridges
      • Hydrothermal vents
        • Seawater percolates through cracks in the ocean floor and is heated to about 350 degrees.
          • Causing sulfate to react with water, forming hydrogen sulfide
          • Provides source of energy for chemoautotrophic organisms
          • Ecosystem can exist where light never penetrates because chemosynthesis doesn’t require light energy.

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Biomagnification of Mercury

  • Mercury becomes a serious environmental risk when it undergoes bioaccumulation in an organism’s body.
  • Mercury enters ecosystems at the base of the food chain and increases in concentration as it moves up.
    • Top-level predators and organisms that are long-lived are the most susceptible to high levels of mercury accumulation.
  • Mercury exposure for humans primarily occurs by eating contaminated fish.
    • Can lead to sterility in males, damage to the central nervous system, and birth defect in humans
  • Mercury travels through food webs to terrestrial ecosystems.
    • High levels of mercury have been found in terrestrial birds.

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Biomagnification of Mercury-1

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Aquatic Ecosystems-9

  • Ocean Currents
    • Major ocean currents move warm water and heat from the equator to cooler parts of the biosphere.
      • Gulf Stream current warms the East Coast of North America and the higher latitudes of western Europe.
        • Moves tropical Caribbean water
      • Another current in the Southern Hemisphere warms the eastern coast of South America.
      • The Humboldt Current in the Southern Hemisphere flows towards the equator.
        • Carries cold water northward along the western coast of South America
      • In upwelling, cold offshore winds replace warm nutrient-poor waters with cold nutrient-rich waters.
        • El Nino Southern Oscillation – Cold upwelling off west coast of South America subsides.
          • Climate patterns change globally.

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Ocean Currents

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Appendix : Long Description for Visuals

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Long Description for Distribution of Solar Energy

Distribution of solar energy. a. Because the Earth is a sphere, beams of solar energy striking the Earth near one of the poles are spread over a wider area than similar beams striking the Earth at the equator. b. The seasons of the Northern and Southern Hemispheres are due to the tilt of the Earth on its axis as it rotates about the sun.

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Long Description for Global Wind Circulation

Global wind circulation. Air ascends and descends as shown because the Earth rotates on its axis. Also, the trade winds move from the northeast to the west in the Northern Hemisphere, and from the southeast to the west in the Southern Hemisphere. The westerlies move toward the east.

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Long Description for Formation of a Rain Shadow

Formation of a rain shadow. When winds from the sea cross a coastal mountain range, they rise and release their moisture as they cool this side of a mountain, called the windward side. The leeward side of a mountain receives relatively little rain and is therefore said to lie in a “rain shadow.”

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Long Description for Biome Pattern of Temperature and Precipitation

Pattern of biome distribution. a. Pattern of world biomes in relation to temperature and moisture. The dashed line encloses a wide range of environments in which either grasses or woody plants can dominate the area, depending on the soil type.

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Long Description for Distribution of Biomes

b. The same type of biome can occur in different regions of the world, as shown on this global map.

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Long Description for Climate and Biomes

Climate and biomes. Biomes change with altitude just as they do with latitude because vegetation is partly determined by temperature. Precipitation also plays a significant role, which is one reason grasslands, instead of tropical or deciduous forests, are sometimes found at the base of mountains.

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Long Description for The Tundra

The tundra. a. In this biome, which is nearest the polar regions, the vegetation consists principally of lichens, mosses, grasses, and low-growing shrubs. The melting snow forms pools of water on the permanently frozen ground, attracting many birds. b. Caribou will feed on lichens, grasses, and shrubs during the summer then migrate south during the winter.

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Long Description for The Taiga

The taiga. The taiga, which means “swampland,” spans northern Europe, Asia, and North America. The appellation “spruce-moose” refers to the (a) dominant presence of spruce trees and (b) moose, which frequent the ponds.

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Long Description for Temperate Deciduous Forest

Temperate deciduous forest. a. The Shawnee National Forest in Illinois is home to many varied plants and animals. b. Marsh marigolds may be found in wetland areas, chipmunks feed on acorns, and bobcats prey on these and other small mammals.

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Long Description for Levels of Life in a Tropical Rain Forest

Levels of life in a tropical rain forest. The primary levels in a tropical rain forest are the canopy, the understory, and the forest floor. But the canopy (solid layer of leaves) contains levels as well, and some organisms spend their entire lives in one particular level. Long lianas (hanging vines) climb into the canopy, where they produce leaves. Epiphytes are air plants that grow on the trees but do not parasitize them.

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Long Description for Representative Animals of the Tropical Rain Forests of the World

Tropical rain forests. Some of the representative animals found in the tropical rain forests.

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Long Description for Shrubland

Shrubland. a. Shrublands, such as chaparral in California, are subject to raging fires, but the shrubs are adapted to quickly regrow.b. Greater roadrunners find a home in the chaparral.

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Long Description for Temperate Grassland

Temperate grassland. a. Tall-grass prairies are seas of grasses dotted by pines and junipers. b. Bison, once abundant, are now being reintroduced into certain areas.

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Long Description for The Savanna

The savanna. The African savanna varies from grassland to widely spaced shrubs and trees. a. This biome supports a large assemblage of herbivores (e.g., zebras, wildebeests, and giraffes). b. Carnivores (e.g., cheetahs) prey on these.

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Long Description for The Desert

The desert. Plants and animals that live in a desert are adapted to arid conditions. a. The plants are either succulents, which retain moisture, or shrubs with woody stems and small leaves, which lose little moisture. b. Among the animal life, the kangaroo rat feeds on seeds and other vegetation. c. Burrowing owls feed on rodents, reptiles, and insects. d. The kit fox is a desert carnivore.

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Long Description for Freshwater and Saltwater Ecosystems

Freshwater and saltwater ecosystems. Center: Mountain streams have cold, clear water that flows over waterfalls and rapids. As streams merge, a river forms and gets increasingly wider and deeper until it meanders across broad, flat valleys. At its mouth, a river may divide into many channels, where wetlands and estuaries are located, before flowing into the sea. To Sides: Mayfly larvae are found in clean water with a high oxygen content. Trout are a major predator of mayflies. Carp are adapted to water that contains little oxygen and much sediment. Blue crabs are found in estuary regions

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Long Description for Types of Lakes

Types of lakes. Lakes can be classified according to whether they are (a) oligotrophic (nutrient-poor) or (b) eutrophic (nutrient-rich). Eutrophic lakes tend to have large populations of algae and rooted plants, resulting in a large population of decomposers, which use up much of the oxygen and leave little oxygen for fishes.

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Long Description for Lake Stratification in a Temperate Region

Lake stratification in a temperate region. Temperature profiles of a large oligotrophic lake in a temperate region vary with the season. During the spring and fall overturns, the deep waters receive oxygen from surface waters, and surface waters receive inorganic nutrients from deep waters.

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Long Description for Zones of a Lake

Zones of a lake. Rooted plants and clinging organisms live in the littoral zone. Phytoplankton, zooplankton, and fishes are in the sunlit limnetic zone. Water striders (photo) stand on the surface film of water with water-repellent feet. Crayfishes and molluscs (art) are in the profundal zone as well as the littoral zone. Pike (photo and art) are top carnivores prized by anglers.

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Long Description for Coastal Ecosystems

Coastal ecosystems. a. Mudflats are frequented by migrant birds. b. Mangrove swamps skirt the coastlines of many tropical and subtropical lands. c. Some organisms of a rocky coast live in tidal pools.

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Long Description for Ocean Ecosystems

Ocean ecosystems. Organisms live in the well-lit waters of the euphotic zone and in the increasing darkness of the deep-sea waters of the pelagic zones (see Fig. 46.21).

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Long Description for Ocean Inhabitants

Ocean inhabitants Different organisms are characteristic of the epipelagic, mesopelagic, and bathypelagic zones of the pelagic division compared to the abyssal zone of the benthic division.

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Long Description for Biomagnification of Mercury-1

Biomagnification of mercury. a. Tuna may contain high levels of mercury due to biomagnification. b. Eating tuna or other fish that contains high levels of mercury can lead to problems with fetal development.

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Long Description for Ocean Currents

Ocean currents. The arrows on this map indicate the locations and directions of the major ocean currents set in motion by the global wind circulation. By carrying warm water to cool latitudes (e.g., the Gulf Stream) and cool water to warm latitudes (e.g., the Humboldt Current), these currents have a major effect on the world’s climates.

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