Biomes

Biomes  Many of the trees and shrubs in a seasonal

 General type of communi�es with similar forest are drought-deciduous
climate condi�ons, growth paterns, and  Seasonal forests are o�en open woodlands
vegeta�on types. that grade into savannas.

Major World Biomes Tropical Savannas and Grasslands

Terrestrial Biomes  Grasslands - also known as prairies or
 Characteris�cs of biological communi�es steppes; receive between 25 and 75 cm of
vary with temperature, precipita�on, and rain per year.
la�tude.  Savannas - extensive grasslands w/
 Hot, humid regions generally have greater occasional or patches of trees; typically
biological produc�vity than cold or dry tropical w/ 50-150 cm of rain per year.
regions.  Most tropical savannas and grasslands have
 Climate graphs are used to describe and a rainy season, but generally the rains are
compare precipita�on and temperature in less abundant or less dependable than in a
different biomes. forest.
 Temperature and precipitation are the most  During dry seasons, fires can sweep across
important determinants in biome grassland, killing off young trees and keeping
distribu�on on land. the landscape open.
 Ver�cal zona�on occurs as vegeta�on type
change rapidly from warm and dry to cold Desert
and wet as you go up a mountain.  Occur where precipitation is rare and
unpredictable, usually with less than 30 cm
of rain per year.
 Desert is more vulnerable, sparse, slow-
growing vegeta�on is quickly damaged by
off-road vehicles.
 Desert soils recover slowly.
 Desert is also vulnerable to overgrazing.

Temperate Grasslands
 As in tropical la�tudes, temperate (mid-
la�tude) grasslands occur where there is
enough rain to support abundant grass but
not enough for forests.
 Forbs - a complex, diverse mix of grasses and
flowering herbaceous plants
 Deep roots help plants in temperate
Tropical Moist Forests
grasslands and savannas survive drought,
fire, and extreme heat and cold. These roots,
Kinds of Moist Tropical Forests
together with an annual winter
 Cloud Forests – are found high in the
accumula�on of dead leaves on the surface,
mountains where fog and mist keep
produce thick, organic-rich soils in temperate
vegeta�on wet all the �me.
grasslands.
 Tropical rainforests – occur where rainfall is
abundant and temperatures are warm to hot
Temperate Shrublands
year-round.
 Evergreen shrubs with small, leathery,
sclerophyllous (hard, waxy) leaves form
Tropical Seasonal Forests
dense thickets.
 Drought-tolerant forests that look brown and
 other small trees o�en cluster in sheltered
dormant in the dry season but burst into vivid
valleys. Periodic fires burn fiercely in this
green during rainy months.
 O�en called Dry Tropical Forests
 Biomes

fuel-rich plant assemblage and are a major  have deep pigmenta�on and
factor in plant succession. leathery leaves
 this landscape is called chaparral, Spanish for
“thicket”. Marine Ecosystem
 inhabited by drought-tolerant animals  Vary mainly with depth, temperature, and
salinity.
Temperate Forests  Ver�cal stra�fica�on - key feature of aqua�c
 Deciduous Forests ecosystems
 Broadleaf forests occur throughout the  Deep ocean species o�en grow slowly in part
world where rainfall is plentiful. because metabolism is reduced in cold
 In mid latitudes, these forests are deciduous conditions.
and lose their leaves in winter.  Temperature also affects the amount of
 At lower la�tudes, broadleaf forests may be oxygen and other elements that can be
evergreen or drought-deciduous. absorbed in water.
 Can re-grow quickly because they occupy  Phytoplankton - microscopic floa�ng algae
moist, moderate climates. that carry on photosynthesis in pelagic
ecosystem
 Coniferous Forests  Zooplanktons - small, weakly swimming
 Grow in a wide range of temperature and animals that feed on phytoplankton.
moisture condi�ons.
 O�en they occur where moisture is limited Ocean Systems based on depth and proximity to
 Temperate Rainforest - a cool, rainy forest shore
o�en enshrouded in fog.  Benthic – communi�es occur on the botom.
 Pelagic zone – (from “sea” in Greek) are the
Boreal Forest water column.
 Or Northern Forests  Epipelagic zone – (epi = on top) has
 Lie between about 50° and 60° north. photosynthe�c organisms. Below this are the
 Mountainous areas at lower la�tudes may mesopelagic (meso = medium), and
also have many characteris�cs and species of bathypelagic (bathos = deep) zones.
the boreal forest.  Deepest layers: Abyssal Zone (to 4,000 m)
 Dominant trees are pines, hemlocks, spruce, and Hadal Zone (deeper than 6,000 m).
cedar, and fir.  Litoral Zones – shorelines.
 These forests are slow-growing because of  Inter�dal Zone – area exposed by low �des.
the cold temperatures and a short frost-free
growing season
 The extreme, ragged edge of the boreal
forest, where forest gradually gives way to
open tundra, is known by its Russian name,
Taiga.
 Tundra - A treeless landscape that occurs at
high la�tudes or on mountaintops, has a
growing season of only two or three months
 Arc�c Tundra - an expansive biome that
has low productivity because it has a
short growing season.
 Alpine Tundra
 Occurring on a near mountain top
 has environmental condi�ons
and vegeta�on similar to arc�c
tundra
 have a short, intense growing
season
 Biomes

Coastal Zones  Epilimnion – a warmer upper layer that

Coral Reefs is mixed by wind and warmed by the sun.
 among the best-known marine ecosystems  Hypolimnion – below the epilimnion. A
because of their extraordinary biological colder, deeper layer that is not mixed.
productivity and their diverse and beau�ful  Thermocline – Sharp temperature
organisms. boundary.
 Mesolimnion – below thermocline, the
Mangroves water is much colder.
 trees that grow in salt water.
 occur along calm, shallow, tropical Wetlands - Shallow ecosystems in which the land
coastlines around the world. surface is saturated or submerged at least part of the
 help stabilize shorelines, and they are also year.
cri�cal nurseries for fish, shrimp, and other  Swamps
commercial species.  Also known as wooded wetlands
 Wetlands with trees.
Estuaries  Marshes
 bays where rivers empty into the sea, mixing  Wetlands without trees.
fresh water with salt water  Bogs
 Areas of saturated ground, and usually
Salt marshes the ground are composed of deep layers
 shallow wetlands flooded regularly or of accumulated, undecayed vegeta�on
occasionally with seawater, occur on known as peat.
shallow coastlines, including estuaries  Fens
 Similar to bogs except that they are
Tide Pools mainly fed by groundwater
 depressions in a rocky shoreline that are
flooded at high �de but retain some water Human Disturbance
at low �de  Humans have become dominant organisms
 These areas remain rocky where wave over most of the earth, damaging or
ac�on prevents most plant growth or disturbing more than half of the world’s
sediment (mud) accumula�on. terrestrial ecosystems to some extent.
 By some es�mates, humans preempt about
Barrier Islands 40 percent of the net terrestrial primary
 low, narrow, sandy islands that form to produc�vity of the biosphere
parallel to a coastline  Conversion of natural habitat to human uses
 occur where the con�nental shelf is shallow is the largest single cause of biodiversity
and rivers or coastal currents provide a losses.
steady source of sediments

Freshwater Ecosystems
 Vary according to depth and light
penetra�on, which control size and types of
vegeta�on.
 O�en small but they are dispropor�onately
important in biodiversity
 Freshwater Lakes - have dis�nct ver�cal
zones.
 Ver�cal Zones
 Benthos – the botom, occupied by a
variety of snails, burrowing worms, fish
and other organisms.