Chapter 4
4-3 Biomes
 Biome – a large group of ecosystems that are characterized by certain soil, climate
conditions, plants and animals
 The climate of a region is an important factor in determining which organisms can
survive there
 Within a biome, temperature and precipitation can vary over small distances
 Latitude is an important abiotic factor to both land and aquatic biomes
The Major Biomes
 Tropical Rain Forest
 Precipitation – 200-400cm of rainfall annually
 Soil – low in nutrients
 Plants – broad-leaved evergreen trees, ferns, large woody vines and climbing
plants, orchids
 Animals – birds, snakes, monkeys, frogs, ants
 Temperature – warm year round 25-29ºC
 Located near equator
 One small acre may support 100 species of plants
 Species live at various levels
 Contains more species of organisms than anywhere else
 Desert
 Precipitation – less than 10cm of rain per year
 Soil – sandy soil, low in nutrients and very little or no topsoil
 Plants – succulent plants that have needle shaped leaves to reduce water loss
 Animals – rattlesnakes, lizards, spiders, roadrunners
 Temperature – humidity is very low so suns rays penetrate and heat the ground
quickly so its hot during the day and cold at night
 Plants are adapted to growing, flowering and producing seed quickly
 Plants are deep rooted
 Desertification – conversion of grasslands and other productive biomes to
desertlike wastelands
 Grassland
 Precipitation – 25-100cm of rain per year
 Soil – very rich in nutrients and deep layer of topsoil
 Plants – tall and short grasses and small plants
 Animals – bison, wolves, prairie dogs, foxes, coyotes
 Temperature – warm summers and very cold winters
 Found in the interior of continents
 Also called prairies
 Not enough rain to support trees
 Savanna
 Precipitation – 30-50cm of rain per year
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 Soil – compact soils
 Plants – grasses, scattered trees
 Animals – lions, cheetahs, elephants, giraffes, zebras, ostriches, rhinoceros
 Temperature – warm year round, 24-29ºC
Woodland and Shrubland
 Precipitation - 25-60cm of rain per year
 Soil – low in nutrients and highly acidic
 Plants – hardened tough evergreens, wildflowers, grasses
 Animals – coyotes, foxes, bobcats, mountain lions
 Temperature – hot dry summers with periodic fires and cool moist winters
 Western or southern coastal region
 Also called chaparral in areas dominated by shrubs
Deciduous Forest
 Precipitation – 70-200cm of rain per year
 Soil – moist and fertile, rich in humus (decaying leaves and other organic matter)
 Plants – birch, maple, oak, elm, evergreens
 Animals – deer, foxes, raccoons, squirrels, birds
 Temperature – warm during the summer and cold in the winter, 0-30ºC
 Deciduous Trees – lose their leaves annually
 ¼ of bird species
Coniferous (Taiga) Forest
 Precipitation – 30-70cm of rain per year, frequent droughts
 Soil – low in nutrients and highly acidic
 Plants – cone bearing trees, pines, firs, spruces
 Animals – moose, bears, timberwolves, migratory birds
 Temperature – warm during the summer and cold in the winter
 Needle shape leaves is adaptation for water loss
 Lies south of the tundra
Tundra
 Precipitation – 20-60cm of rain per year
 Soil – thin moist and nutrient poor
 Plants – mosses, lichens, and grasses that survive in soggy soil
 Animals – caribou, reindeer, artic fox
 Temperature – cool in summer and freezing in winter
 Permafrost – permanently frozen ground
 Treeless land
 Long summer days and short periods of winter sunlight
4-4 Aquatic Ecosystems
 Nearly ¾’s of the Earth’s surface is covered with water
 Aquatic ecosystems are often grouped according to the abiotic factors that affect
them.
 The depth of water determines the amount of light that organisms receive
 Communities of organisms found in shallow water close to shore can be very
different from the communities that occur away from shore in deep water
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Freshwater Ecosystems
 Flowing-Water Ecosystems
 Rivers, streams, creeks, and brooks
 Originate in mountains or hills
 3 Types of Stream Habitats
1. Riffle
 Shallow
 Water flows swiftly over rough bottom of sand and rock
2. Pools
 Deep water flows slowly over smooth bottom
3. Runs
 Smooth surface but fast flowing water
 Standing-Water Ecosystems
 Lakes and ponds
 A Lake has 3 Zones
1. Littoral
 All around the shore
 Water is shallow and well lit
 Diversity is greatest
2. Limnetic
 Open water
 Sunlit water that extends to where photosynthesis takes place
 Plankton, diatoms, green algae
3. Profundal
 Open water
 Below depth of photosynthesis
 Bacterial decomposers
 Lakes show seasonal changes in temperate regions
 Spring Overturn
 DO from the surface moves to deep water and nutrients released by
decomposition moves to surface
 Fall Overturn
 Upper layer cools becomes denser then sinks
 DO moves down and nutrients move up
 Oligotrophic Lake
 Nutrient poor and oxygen rich
 Deep lake with few phytoplankton
 Eutrophic Lake
 Nutrient rich and oxygen poor
 Has a high rate of biological productivity
Freshwater Wetlands
 Wetland – water covers the soil or is present at or near the surface of the soil at
least part of the year
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 3 Types of Freshwater Wetlands
1. Bog – wetland that form in depressions where water collects
2. Marsh – shallow wetland along river
3. Swamp – look like flooded forests, water flows slowly
Estuaries
 Estuary – a place where salt water mixes with fresh water
 The salinity of an estuary changes with the tides so a large range of salt tolerant
organisms live there
 Mangrove – coastal wetland that occur in bays and estuaries across tropical regions
 In southern Florida and Hawaii
 Dominant plants are salt-tolerant trees, called mangrove
Marine Ecosystems
 Intertidal Zone
 Portion of the shoreline between the high and low tides
 High levels of sunlight, nutrients, and oxygen but productivity may be limited by
waves crashing against the shore
 Organisms that live here have to be adapted to changing conditions
 Benthic Zone
 Includes all sediments and rocks of the ocean bottom
 Starts at continental shelves and extends to deep sea trenches
 Pelagic Zone
 Full volume of ocean water
Coral Reefs
 Found in tropical coastal water
 Named for the coral animals whose calcium carbonate skeletons make up their
primary structure
 An extraordinary diversity of organisms flourishes among coral reefs
 Reef-building corals grow with the help of algae that live symbiotically within their
tissues
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