Environmental Science
Chapter 4, section 4.2
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NOTES
Kinds of Ecosystems
4.2: Grasslands, Chaparral, Deserts and Tundra
 Climates with less rainfall:
savannas, grasslands, chaparrals, deserts
 As precipitation decreases, so does the diversity of species present
 Number of different species is smaller, individuals of each species is even smaller
 Another type of “desert” is present far to the north. It is called the tundra. Very little precipitation
occurs here and temperatures stay very cold year round
Savannas
 Parts of Africa, western India, northern Australia and some parts of South America are covered by
grasslands called savanna; located in tropical and subtropical areas, between tropical rain forests and
deserts
 West African plains contain the greatest collection of grazing animals on Earth and the predators that
hunt them
 Not many trees, too little rainfall
 Savannas have a wet season and a dry season; grass fires may sweep across savannas in the dry season
Savannas: Animal Adaptations
 Migratory lifestyle of the large, grazing herbivores, such as the elephant
 Animals follow the rains to newly sprouted grasses
 Predatory animals follow their mobile food source
 Give birth during rainy season when food is more abundant and survival is greatest
 Avoid competition by eating vegetation at different heights; ex: small gazelle grass on grasses, black
rhinos browse on shrubs and giraffes feed on tree leaves
Savannas: Plant Adaptations
 Most rain falls during the wet season, therefore, plants must be able to survive long periods without
water
 Savanna trees and grasses have horizontal underground root systems to obtain water and enable them
that survive long dry seasons and regrow quickly after fires
 Course savanna grasses have vertical leaves
 Trees and shrubs have thorns or razor sharp leaves – deter herbivores
Temperate Grasslands: Prairies, Steppes and Pampas
 This biome is dominated by grasses and has very few trees; hot summers and cold winters; temperate
grassland can receive 50 to 88 cm of precipitation per year
 Grasslands have the most fertile soil of any biome
 Many natural temperate grasslands have been replaced with crops of corn, soybean and wheat
 Grasslands at one time covered 42% of the total land surface on Earth; today, they cover only about 12%
 Found on interiors of continents where there is too little rainfall for trees to grow; prairies of North
America, steppes of Russia and Ukraine, pampas of South America
 Mountains play a crucial role in maintaining grasslands by blocking rain clouds thus maintaining low
rainfalls; rainfall increases as you move eastward, thus larger grasses/shrubs can grow
 Sizzling summer temperatures make grasslands a tinderbox; fire is common in grasslands
Temperate Grasslands: Plant Adaptations
 Prairie grasses are perennials, surviving from year to year
 Root systems form dense mats the survive drought and fire and hold the soil in place
 Rainfall determines what type of grasses will grow in an area
 Few trees will survive on the grasslands because of drought, fire and constant battering of winds
Temperate Grasslands: Animal Adaptations
 Grazing animals (pronghorn antelope and American Buffalo) have large, flat back teeth for chewing
coarse prairie grasses
 Grazers cope with severe winters by growing thick coats of fur which they shed in spring
 Badgers, prairie dogs, owls live in protected underground burrows; these burrows shield them from fire,
the elements and predators
Threats to Temperate Grasslands
 Cultivation and overgrazing have changed the grasslands
 Grain crops have replaced native grasses and cannot hold the soil in place as well because their roots are
shallow, resulting in soil erosion
 Overgrazed animals are constantly chewing down the grasses hindering them from regenerating or
holding the soil, thus furthering soil erosion; constant use is changing the fruitful grasslands into less
productive, desert like biomes
Chaparral
 A type of temperate woodland biome; have fairly dry climates but get enough rainfall to support more
plants than a desert; have scattered trees communities (coniferous trees such as pinon pines, junipers)
 Occurs in the mid-latitudes (30 degrees north and south of the equator)
 Lies primarily in coastal areas that have Mediterranean climates, ex: Hollywood, Calif
 Known for their hot, dry summers; mild, wet winters; and slight variations in seasonal temperatures
Chaparral: Plant Adaptations
 Mostly low-lying evergreen shrubs and small trees
 ex: chamise, manzanita, shrub oak, olive trees and cooking herbs like sage and bay
 Plants have small, leathery leaves that resist water loss; they contain oils that promote burning
 Natural fires destroy trees that compete with chaparral plants, thus allowing light and space for the
smaller plants
 Plants are well adapted and can regrow from small bits of surviving tissue
Chaparral: Animal Adaptations
 Common adaptation is camouflage – shape or coloring that allows them to blend with their environment
 Quail, lizards, chipmunks and mule deer have brownish gray coats that allows them to move through the
brush
 Animals have adapted to seasonal differences for food
Threats to the Chaparral
 Biggest threat worldwide is human development
 This biome has lots of sun, access to oceans and mild year-round climates which is inviting to humans
Deserts
 They are the driest places on Earth, receiving less than 25 cm (10 in) of precipitation a year; they have
little or no vegetation and have extreme temperatures


Hot deserts occur closer to the equator ( Sonoran Desert in Arizona, Sahara Desert in Africa), cold
deserts are farther away (Gobi Desert in China, Great Basin in US)
Often occur in the rain shadow of mountains (leeward side of the mountain)
Deserts: Plant Adaptations
 Plants in the desert have adaptations for obtaining and conserving water
 Succulents and cacti have thick, fleshy stems and leaves that store water; have waxy coating to prevent
water loss
 Spines deter thirsty animals from eating plant’s juicy flesh
 Roots are shallow and spread out widely
 Plants are adapted to drought, will die when it is too dry, drop their seeds which lie dormant until the
next rainfall when they germinate, grow and bloom before the soil becomes dry again (droughtresistance); adapted to survive even when their water content falls below 30% of their mass (water levels
between 50% to 75% are fatal for most plants)
Deserts: Animal Adaptations
 Reptiles (gila monsters, rattlesnakes) have thick, scaly skins that prevent water loss
 Amphibians (spadefoot toad) survive scorching desert summers by burying themselves in the ground
and sleeping through the dry season (estivating)
 Insects and spiders are covered with body armor to help them retain water
 Most animals are active at night or at dusk, when the air is cooler
Threats to the Desert
 In the American West, residential development encroaches upon the desert areas
 Off-road and all-terrain vehicles kill desert vegetation, destroying habitats of endangered animals (desert
tortoise)
 Humans removing desert plants endanger plant populations
Tundra
 Lies north of the Arctic Circle; has no tall trees; dominated by grasses, lichens and herbs
 Frozen soil supports mostly tough grasses and shrubs
 Summers are short; only a few inches of the soil thaws; becomes dotted with bogs and swamps during
the thaw periods; makes an ideal breeding ground for huge numbers of swarming insects (mosquitoes,
blackflies) and birds that feed on them
 Under soil lies the permafrost
Tundra: Plant Adaptations
 Mosses and lichens cover acres of rocks (don’t need soil to grow)
 Where soil (thin) exists, plants have shallow, wide roots which anchor them against arctic winds
 Flowering plants (moss campion, gentian) are tiny and hug the ground for warmth and to stay out of the
wind
 Woody plants and perennials (willow, junipers) have evolved dwarf forms and grow flat or trailing
 Plants grow and flower quickly (short summers)
Tundra: Animal Adaptations
 Millions of migratory birds breed during the short summer because of the abundant food supply (plants,
mollusks, worms, insects)
 Caribou and reindeer migrate; wolves prey on the caribou, deer, moose, lemmings, mice and rabbits.
 Rodents burrow underground during winter
 Year-round residents (arctic fox) have white fur in winter; coats are extremely well insulated (musk ox)
Threats to the Tundra
 One of the most fragile biomes on Earth
 Food chains are relatively simple and can be disrupted easily
 Conditions are so extreme, land is easily damaged and slow to recover.
 Oil extraction and transport across land has brought humans to the area, which has disturbed the delicate
balance of the biome