Biomes
What is a biome?
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Biotic
Examples: Plants, animals, fungi, bacteria
Abiotic
Examples: Sunlight, soil, air, temperature, light, wind, water
Climate
Precipitation
In the boxes below, write one phrase to summarize and give a
definition for your biome. Then, draw a picture to help you remember the
defining characteristics of that biome.
Biome
Tropical
Rainforest
Temperate
Rainforest
Deciduous
Forest
Taiga
Desert
Tundra
Grasslands
Savanna
Definition
Drawing
Tropical Rainforests
Tropical rain forests occur in a belt around the Earth near the equator in South
America, parts of Africa and Southeast Asia. They are always heavy with humidity and
are characterized by heavy rainfall (250-700cm a year). Because they are near the
equator, tropical rainforests maintain a constant warm climate of about 30°C (85°F)
year around, making it an ideal climate for growing plants. Tropical rainforests have the
greatest amount of biological diversity (number of different species) out of any other
biome.
Although the climate is ideal for plant life, the soil is usually thin and devoid
(lacking in) of nutrients due to the large amount of rainfall washing away the few
nutrients left in the soil after the plants have taken up the majority. Because there are
many organisms, there is rapid decay which returns nutrients of the soil but these
nutrients are quickly taken up by the plants. Many of the trees adapt to the poor soil
conditions by having aboveground roots that grow sideways (stilt roots) from the trees
to provide extra support.
Many of the plants in tropical rainforests grow in
layers, forming a dense canopy which absorbs about
95% of the sunlight. Little light reaches the understory
under the canopy, leaving only shrubs and small trees
well adapted to living in shade. Many of the plants grow
up the side of large trees to reach the sunlight. Many
plants also have drip tips- special leaf shapes which
enable the massive amount of rainfall to quickly run off
the plant. Common plants include orchids, ferns,
bromeliads, banyan trees, pitcher plants, palm trees and
bamboo trees.
Because of the incredible diversity of organisms in the
rainforest, the animals found there are adapted to exploit
specific resources to avoid competition. For example, there are
several birds that eat insects but each bird species eats insects
only in a certain layer of the vegetation. Insects, bats and birds
only pollinate one species of plant, reducing competition for
food. Common animals include the chimpanzee, capybara,
orangutan, slow loris, macaws, flying dragons, jaguars, howler monkeys, anacondas,
piranhas, toucans and many others.
Tropical rainforests are rapidly disappearing due to deforestation- destroyed by
logging or cleared for ranches or farms. Many of the plants and animals become extinct
and native peoples are often displaced. Every year an area of the tropical rainforest the
size of North and South Carolina combined is destroyed. Tropical rainforests used to
cover about 20% of the Earth’s surfaced- now they cover about 7%.
Temperate Rainforests
Temperate rainforests are found mostly in North America, although some are
found in South America and Australia. In North America, temperate rainforests can be
found in the Pacific Northwest (Washington, Oregon, Northern California). Temperate
rainforests have great diversity, although they contain much fewer species than Tropical
Rainforests. They are cool, humid forests which receive a large amount of rainfall and
the temperatures rarely fall below freezing.
Temperate Rainforests generally experience rainfall of about 200-400cm a year
and experience a cooler climate than tropical rainforests, ranging anywhere from 25°C
to 5°C (75°-30°F). Precipitation can take the form of either rain or snow, depending on
the season. Temperate rainforests experience four distinct seasons, unlike the tropical
rainforest, which maintains a warm climate year around. There are dry summers and
colder wet winters.
Temperate rainforests do not have many
broadleaf plant like the tropical rainforest. Most of the
trees found here are coniferous or evergreens. The decay
rate in temperature rainforests is much slower than in
tropical rainforests due to the slow decay of needle
leaves compared to broad leaves and the cooler
temperatures (warm temperatures increase decay). Due
to a slower decay, as well as a lack of the wide root
systems found in tropical rainforests, the soil in
temperate rainforests is much richer than tropical rainforests. There are often “nurse”
logs which have fallen and now provide habitats and nutrients for the organisms in the
rainforest as they decay.
A canopy and understory is also present in temperature
rainforests. Many of the trees are ancient, huge, and have stilts
(pitchfork like extensions to allow them to root in the soil). Common
plants include incredibly old large coniferous (needle-like) trees such
as red cedars, redwoods, Douglas firs and hemlocks, as well as
mosses, fungi and lichens growing on decaying logs and as epiphytes
(growing on other trees but not acting as parasites).
Many animals live on the forest floor and have adapted to
eating the tough conifer needles. Animals in the temperate rainforest
camouflage themselves by having brown, gray or green colorings. Common animals
include a variety of slugs, black and brown bears, raccoons, skunks, cougars, elk, owls,
chipmunks, moose and rabbits.
Threats to the temperate rainforest include deforestation, clearing the forest for
farming, the logging industry cutting down trees and pollution.
Deciduous Forests
Deciduous forests are found throughout
eastern North America, Europe and parts of
Asia. Deciduous forests are characterized by
their deciduous plants, which shed their broad
leaves every autumn (unlike coniferous plants
who do not shed their leaves). They experience
extreme weather changes throughout the year.
Deciduous forests experience the four
seasons, which be vary from 35°C (95°F) in the
summer to well below freezing in the winter.
Deciduous forests receive about 50-250cm of precipitation annually, which allows for
the decomposition of dead organic matter by bacteria and a variety of fungi. This leads
to a very rich and deep soil which is full of nutrients.
Plants of deciduous forests grow in layers and include a canopy and forest floor.
The forest floor receives more light than in rainforests and a larger number of plants
grow on the forest floor as a result. Deciduous forest plants have adapted to the seasonal
changes by shedding their leaves every fall to conserve moisture and sugar in the tree
trunk, as well as to survive heavy snowstorms without risking the breaking of their
branches. Rhizomes (underground stems) are present and become dormant during the
winter. Rhizomes survive in the cold ground because they are somewhat insulated by the
fallen leaves and snow. The trees often grow thick bark to protect themselves from the
cold winter temperatures and parasitic fungi. Common plants include maple, oak,
sycamore, walnut, ash and birch trees, as well many
wildflowers, small shrubs and bushes.
Animals blend into their environment by having
less colorful fur due to the lack of tree cover in the
winter. Due to the colder temperatures, animals in the
deciduous forest have adapted to survive the winters
through hibernation. They eat a tremendous amount of
food before the winter to store as fat and sleep through
the winter to avoid battling for limited food supplies
during the snowy winter months. Many species of bird migrate during the winter to
warmer climates. Many of the organisms have developed thicker coats to survive the
winter. Deer and elk have developed smaller antlers to allow them to move easily
through the underbrush. Common animals include deer, black and brown bears, wolves,
raccoons, turkeys, owls, chipmunks, moose and rabbits.
Threats to deciduous forests lie mostly in destroying the forests for agriculture
and development of towns/house, as well as logging.
Taiga
The taiga is the northern coniferous forest which stretches across the northern
hemisphere through below the Arctic Circle in countries such as Canada, Sweden,
Iceland, Finland, Russia and the U.S. (Alaska). The taiga is the largest continuous biome
in the world and is often prone to wildfires. There is constant daylight during the
summer and very little diversity in species.
The taiga consists of coniferous
trees with needle like leaves that
contain acidic substances. When the
leaves die and fall to the ground, the
soil becomes acidified, which is one
reason there are very few plants on
the forest floor, save for a few ferns
and mosses. The soil is thin and
lacking in nutrients due to the climate
(cold leads to slow decomposition)
and acidity.
Taiga is extremely cold and have long winters (6-10 months out of a year). During
the winter, the average temperature is often below freezing and can plummet to -54°C
(-65°F). The summer months range anywhere from -7°C to 15°C (19.4°F - 59°F). The
growing season without frost can be as short as 50 days. The taiga receives little
precipitation (30-90cm) and often falls as snow, with some rainfall during the summer
months.
Coniferous plants do not shed their needle-like leaves to help them maintain
water in their leaves during the harsh winter months. The cone-like shape also helps the
tree shed snow stuck on its branches. The plants in the taiga often have thick bark to
protect the trees from wildfires. The trees’ waxy needle-like leaves help to preserve
water and the tough cones protect the seeds inside. The trees also have shallow roots
systems to allow them to use water quickly when the snow melts in the spring. Common
plant species include pine, hemlock, spruce and fir trees.
The lakes and swamps attract birds that feed on insects and fish. These birds
migrate south for the winter. Year round residents burrow underground or hibernate
and remain insulated by the deep snow cover. Many animals have white or brown
coloring to camouflage them from predators, as well as thick fur to keep them warm in
the winter. Hares that are brown in the summer shed their fur and grow white fur to
camouflage them in the winter. Common animals include lynxes, wolves, caribou, foxes,
hares, and moose.
The taiga is being destroyed by mining, trapping animals for their fur, pollution
in the lakes or rivers and finally by the logging industry, which is cutting down large
sections of the taiga’s trees for pulp and paper.
Desert
Deserts are defined as areas that receive less than 25cm of precipitation each
year. Deserts are extremely hot and extremely dry. There are only a few periods of heavy
rainfall per year. They are generally found between 30° latitude north and 30° latitude
south. Deserts are found in northern & southern Africa (Sahara, Kalahari), parts of
Australia, North & South America (Mojave desert in CA, NV & AZ) and in Mongolia
(Gobi desert).
Deserts receive less than 25cm of precipitation
each year. Due to the small amount of rainfall, few
nutrients get washed away from the soil. The dryness
hinders decay of dead organic matter, leading to soil
that is rich in nutrients but poor in organic matter.
Temperatures during the day often exceed
40°C (100°F) and drop to 5°C (41°F) at night. The
temperatures drop so drastically at night due to a lack
of humidity or trees to retain heat and provide insulation. Deserts cool down rapidly at
night and heat up quickly after the sun rises.
All desert plants are characterized by adaptations which allow them to get and
conserve water. Succulents and cacti have thick fleshy stems and leave which store water
and have a waxy coating to prevent water loss. Cactus spines stop thirsty animals from
devouring the plants. Some plants store water in underground bulbs which spread out
under the surface to catch as much rain as possible. Others contain toxins which
prevents other plants from growing nearby. Common plants include saguaro cacti,
barrel cacti, prickly pear cacti, dragon trees, aloe plants and yucca plants.
Animals in the desert must survive
the intense heat, searing sun and a lack of
water. Some animals get their water from
seeds and plants. Others are nocturnal to
avoid the hot sun during the day. Many
animals stay in the cool underground.
Reptiles have dry scaly skin to prevent water
loss. Common animals include gila
monsters, camels, sidewinder snakes, thorny
devils, spadefoot toads, coyotes,
rattlesnakes, vultures, scorpions and small rodents.
Global warming is increasing droughts, which lead to the drying up of water holes
and a larger number of wildfires. Agriculture and farming leads to the destruction of
plants and the soil.
Tundra
The tundra is a biome found north of the
Arctic Circle, near the North Pole. Areas of northern
Russia and Canada, as well as Greenland and Alaska
are considered part of the tundra biome. The tundra
is a very cold, windy, rocky biome without trees and
with very little precipitation, where grasses and tough
shrubs grow in the frozen soil. There are nomadic
tribes who survive here in the tundra. There is very
low biological diversity found in the tundra.
During winter, it is very cold and dark with the average temperature around 28°C (-18°F), sometimes dropping as low as -50°C (-58°F). During the warm summer
months (12°C) when the sun is shining 24 hours a day, the tundra is covered in marshes,
lakes and bogs created by the thawing of the top layer of soil. The tundra is similar to
deserts in terms of precipitation- it receives between 15-25cm of rainfall per year.
The tundra experiences very short
summers causing only the first few inches of soil
to thaw. Underneath this lies permafrost, which
is the term for permanently frozen soil.
Permafrost is impenetrable (impossible to break
through). Where soil does exist, it is very thin.
The tundra does not have any trees and
the plants found in this biome grow low to the
ground due to the arctic winds. Mosses and
lichens cover acres of rocks due to their ability to grow without soil. Lichens are
organisms which are composed of a fungus and an algae living and growing together.
Plants have wide shallow roots to anchor them in the thin soil against the arctic winds.
Many plants in the tundra are dark red, which allows them to absorb more heat from the
sun in the cold climate. Common plants include lichens, dwarf shrubs, cotton grass and
mosses.
Animals in the tundra are adapted to live in the freezing conditions. Most tundra
organisms are migratory to avoid the cold winter months, although some do hibernate.
Millions of birds feed on the insects and plants in the summer and migrate south during
the winter. Rodents burrow underground during the winter and many animals have
white fur or feathers to blend into the abundant snow. Animals that do not migrate
during the winter have thick coat to keep them warm and well insulated. Common
animals include caribou, wolves, moose, musk ox, arctic foxes, polar bears, and snowy
owls.
The tundra is a very fragile biome and is being destroyed by global warming (melting the
permafrost) and pollution of lakes and land from the extraction of oil.
Grasslands
Grasslands (prairies/steppes) are big open spaces primarily found throughout
Midwestern North America and parts of Asia but they can be seen all over the world.
The world’s grasslands once covered about 42% of the total land surface- today
grasslands occupy only 12% of the Earth’s surface due to the clearing of the plains for
agriculture. Grasslands are found in the inland of continents where there is too little
rainfall for trees to grow.
Grasslands receive 25-90cm of precipitation annually. Average temperatures
range from -5°C to 20°C (23°F - 68°F) , although many grasslands are found in colder (20°C/ -4°F) and hotter (30°C/86°F) climates. Depending on where the grasslands are
found in the world, they might be hot all year around (close to equator) or experience
both hot summers and cold winters (U.S. prairies). Grasslands often experience
wildfires which maintains the grass height and also allows some grasses to re-seed.
Grasslands have the most fertile soil of all biomes. Because of the fertile soil, many of
the grasslands are destroyed to make room for crops.
The hot grasslands near the equator in Africa are called savannas, while the
plains found in the U.S. are called prairies. In Europe, they are called steppes and in
South America, they are known as pampas.
Grasslands contain many species of
grasses with dense root systems which form
mat-like structures to survive drought, fire
and hold the soil in place. Root depth and
grass height vary with the amount of rainfall.
There are tall, short and mixed grass prairies
based on the amount of rainfall. Trees
cannot survive on the prairie due to drought,
fire and constant wind. Common plants
other than grasses include milkweed plants,
wildflowers and stinging nettles.
Prairie
Young grasses are nutritious food for the grazing
animals found in the grasslands, such as bison and
pronghorns. The bison’s thick coats allow them to
survive the cold winters on the plains. Small animals
such as badgers, prairie dogs and owls live in
underground burrows, which shield them from fires
and predators. Common animals include bison, prairie
dogs, pronghorns, owls, ferrets, snakes and many
insects.
Steppe
Savanna
Savannas are found in the West African plains, as well as in some areas of South
America and India. Savannas are considered a type of grassland found in particularly
warm environments. They are found near the equator and occur inland, which causes
them to receive too little rain to allow many trees to grow.
Savannas are warmer than most grasslands and have a very long dry season with
a very short wet season. Temperatures range
from 20°-30°C (68°-86°F) and the Savannah
receives anywhere from 50-120 cm (20-50 in)
of rainfall annually, most of which occurs
during the wet season. Grass fires often sweep
across the Savanna during the dry season,
which returns nutrients from the ash back into
the soil, making it more fertile. Overall, the soil
found in Savannas is infertile and lack
nutrients.
Plants in the Savanna must have adaptations present to survive wildfires and
preserve water during the dry seasons. Many of the grasses have large underground root
systems and thick bark to allow them to survive fires, obtain as much water as possible
and allow plants to quickly regrow after a fire. Many plants also have vertical leaves to
help them to conserve water. The shrubs often have thorns or a bitter taste to stop
herbivores from eating them. Common plants include different types of grasses, acacia
trees, candelabra tree, eucalyptus trees, kangaroo paws and baobabs.
Savannas are home to many herbivores
which graze on the grasses. The grazing
herbivores have a migratory way of life and
follow the rains, allowing them to survive during
the hot dry season. Many animals burrow
underground to avoid predators and the heat.
The animals often give birth only during the
rainy season when food is abundant. They avoid
competition for food by eating vegetation at
different heights (gazelles on grass, rhinos on
shrubs, and giraffes on trees). Common animals include lions, ostriches, giraffes,
warthogs, elephants, rhinoceros and hyenas.
Many savannas have been used as grazing areas for farmers’ cattle and goats. The
farmers do not move their herds often enough and soon the grasses are completely eaten
away. Without any vegetation, the savanna turns into a desert. Huge areas of savanna
are lost to the Sahara desert every year due to overgrazing and farming.