Zoology Biomes

8/19/2019 Zoology Biomes

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BIOMES

BY DENNIE LEO LOGANBMLS-1BSEPTEMBER 6, 2013


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RAINFOREST

The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches (125to 660 cm.) of rain falls yearly.Rain forests belong to the tropical wet climate group. The temperature in a rain forest rarely gets higher than 93 °F(34 °C) or drops below 68 °F (20 °C); average humidity is between 77 and 88%; rainfall is often more than 100 inchesa year. There is usually a brief season of less rain. In monsoonal areas, there is a real dry season. Almost all rainforests lie near the equator.

Rainforests now cover less than 6% of Earth's land surface. Scientists estimate that more than half of all the world'splant and animal species live in tropical rain forests. Tropical rainforests produce 40% of Earth's oxygen. A tropical rain forest has more kinds of trees than any other area in the world. Scientists have counted about 100 to300 species in one 2 1/2-acre (1-hectare) area in South America. Seventy percent of the plants in the rainforest aretrees. About 1/4 of all the medicines we use come from rainforest plants. Curare comes from a tropical vine, and is used asan anaesthetic and to relax muscles during surgery. Quinine, from the cinchona tree, is used to treat malaria. Aperson with lymphocytic leukaemia has a 99% chance that the disease will go into remission because of the rosyperiwinkle. More than 1,400 varieties of tropical plants are thought to be potential cures for cancer. All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don't branchout for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The

majority of the trees have smooth, thin bark because there is no need to protect them from water loss and freezingtemperatures. It also makes it difficult for epiphytes and plant parasites to get a hold on the trunks. The bark ofdifferent species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by theirflowers.Despite these differences, each of the three largest rainforests--the American, the African, and the Asian--has adifferent group of animal and plant species. Each rain forest has many species of monkeys, all of which differ fromthe species of the other two rain forests. In addition, different areas of the same rain forest may have differentspecies. Many kinds of trees that grow in the mountains of the Amazon rain forest do not grow in the lowlands ofthat same forest.


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DESERT

Deserts cover about one fifth of the Earth's surface and occur where rainfall is less than 50 cm/year. Although mostdeserts, such as the Sahara of North Africa and the deserts of the southwestern U.S., Mexico, and Australia, occurat low latitudes, another kind of desert, cold deserts, occur in the basin and range area of Utah and Nevada and inparts of western Asia. Most deserts have a considerable amount of specialized vegetation, as well as specializedvertebrate and invertebrate animals. Soils often have abundant nutrients because they need only water to becomevery productive and have little or no organic matter. Disturbances are common in the form of occasional fires orcold weather, and sudden, infrequent, but intense rains that cause flooding.

There are relatively few large mammals in deserts because most are not capable of storing sufficient water andwithstanding the heat. Deserts often provide little shelter from the sun for large animals. The dominant animals ofwarm deserts are nonmammalian vertebrates, such as reptiles. Mammals are usually small, like the kangaroo miceof North American deserts.

HOT AND DRY DESERTTemperatures exhibit daily extremes because the atmosphere contains little humidity to block the Sun's rays.Desert surfaces receive a little more than twice the solar radiation received by humid regions and lose almost twiceas much heat at night. Many mean annual temperatures range from 20-25° C. The extreme maximum ranges from43.5-49° C. Minimum temperatures sometimes drop to -18° C.

Rainfall is usually very low and/or concentrated in short bursts between long rainless periods. Evaporation ratesregularly exceed rainfall rates. Sometimes rain starts falling and evaporates before reaching the ground. Rainfall islowest on the Atacama Desert of Chile, where it averages less than 1.5 cm. Some years are even rainless. InlandSahara also receives less than 1.5 cm a year. Rainfall in American deserts is higher — almost 28 cm a year.


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The animals include small nocturnal (active at night) carnivores. The dominant animals are burrowers andkangaroo rats. There are also insects, arachnids, reptiles and birds. The animals stay inactive in protectedhideaways during the hot day and come out to forage at dusk, dawn or at night, when the desert is cooler.

SEMI-ARID DESERTThe summers are moderately long and dry, and like hot deserts, the winters normally bring low concentrations ofrainfall. Summer temperatures usually average between 21-27° C. It normally does not go above 38° C and eveningtemperatures are cool, at around 10° C. Cool nights help both plants and animals by reducing moisture loss from

transpiration, sweating and breathing. Furthermore, condensation of dew caused by night cooling may equal orexceed the rainfall received by some deserts. As in the hot desert, rainfall is often very low and/or concentrated.The average rainfall ranges from 2-4 cm annually.

During the day, insects move around twigs to stay on the shady side; jack rabbits follow the moving shadow of acactus or shrub. Naturally, many animals find protection in underground burrows where they are insulated fromboth heat and aridity. These animals include mammals such as the kangaroo rats, rabbits, and skunks; insects likegrasshoppers and ants; reptiles are represented by lizards and snakes; and birds such as burrowing owls and theCalifornia thrasher.

COASTAL DESERTThe cool winters of coastal deserts are followed by moderately long, warm summers. The average summertemperature ranges from 13-24° C; winter temperatures are 5° C or below. The maximum annual temperature isabout 35° C and the minimum is about -4° C. In Chile, the temperature ranges from -2 to 5° C in July and 21-25° Cin January. The average rainfall measures 8-13 cm in many areas. The maximum annual precipitation over a longperiod of years has been 37 cm with a minimum of 5 cm.

Some animals have specialized adaptations for dealing with the desert heat and lack of water. Some toads sealthemselves in burrows with gelatinous secretions and remain inactive for eight or nine months until a heavy rainoccurs. Amphibians that pass through larval stages have accelerated life cycles, which improves their chances ofreaching maturity before the waters evaporate. Some insects lay eggs that remain dormant until theenvironmental conditions are suitable for hatching. The fairy shrimps also lay dormant eggs. Other animalsinclude: insects, mammals (coyote and badger), amphibians (toads), birds (great horned owl, golden eagle and thebald eagle), and reptiles (lizards and snakes).

COLD DESERTThese deserts are characterized by cold winters with snowfall and high overall rainfall throughout the winter andoccasionally over the summer. They occur in the Antarctic, Greenland and the Nearctic realm. They have short,moist, and moderately warm summers with fairly long, cold winters. The mean winter temperature is between -2to 4° C and the mean summer temperature is between 21-26° C. The winters receive quite a bit of snow. The meanannual precipitation ranges from 15-26 cm. Annual precipitation has reached a maximum of 46 cm and a minimumof 9 cm.

The plants are widely scattered. In areas of shadscale, about 10 percent of the ground is covered, but in some areasof sagebush it approaches 85 percent. Plant heights vary between 15 cm and 122 cm. The main plants aredeciduous, most having spiny leaves. Widely distributed animals are jack rabbits, kangaroo rats, kangaroo mice,pocket mice, grasshopper mice, and antelope ground squirrels. In areas like Utah, population density of theseanimals can range from 14-41 individuals per hectare. All except the jack rabbits are burrowers. The burrowinghabit also applies to carnivores like the badger, kit fox, and coyote. Several lizards do some burrowing and movingof soil. Deer are found only in the winter.


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GRASSLAND

Grassland biomes are unaltered areas of land where grass is the dominant plant life, as opposed to other terrestrialbiomes where trees occupy most of the land surface. Grassland are found around the globe and have served asgrazing areas for a large number of animals, and have been exploited as farming grounds or plantations byhumans. Grassland are generally semi-arid areas with little or no trees, and are inhabited by grazing mammals,ground-nesting birds, insects, and a few species of reptiles.

PRAIRIESPrairies are generally humid and are densely covered in tall grass. There are very few trees on prairies, most ofthem usually found on hill slopes or more humid near springs and rivulets. The prairie soil is rich in nutrients and isideal for the growth of plant life, which is why prairie regions have been exploited by farmers for centuries.Grazing animals such as oxen and bison who fed on the prairie grass were also exploited by humans, with the bisonbeing driven to near extinction by hunters.

STEPPE

The steppe grassland is usually found in areas of the world which are less prone to moisture. Steppe vegetation iswell suited to this drier climate, and the grass is generally shorter than that which is found on prairie grasslands.Animal life on the steppe is comprised of grazing mammals such as the antelope, and a wide variety of burrowingmammals such as ground squirrels and ferrets. Steppes are virtually semi-arid deserts in the making, and arehighly threatened by overgrazing.

SAVANNA

Savanna biomes are distinguished by their warmer drier climates, and their seasonal droughts.


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Savanna plant life is highly adapted to the hot and dry climate, with trunks that can store water for days, or specialbuilt-in mechanisms allowing the plant to lie dormant during periods of drought.

TROPICAL SAVANNA

Tropical Savanna is the most ecologically diverse of the grasslands. Here, several species of animals includingbirds, mammals, reptiles, and insects congregate and feed upon the trees and grass or each other. One goodexample of the tropical savanna is found in Africa, where lions, elephants and warthogs make their home.


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Aquatic

The marine regions are divided between coral reefs , estuaries, and oceans . Oceans represent the largest and mostdiverse of the ecosystems; salt water evaporates and turns to rain which falls on the land regions, while most of theoxygen in our atmosphere is generated by algae. Algae is also responsible for the absorption of large amounts ofcarbon dioxide from our atmosphere.

The ocean connect to the land via what is called the intertidal zone . Because of rising and falling tides, coastal areas

are constantly changing, with various animals and marine plants living at the bottom, and on the seashore. Rockycoastal areas are host to fewer species due to the fact that only the highest of tides will reach the top of the cliffs.

In the warm shallow waters which line the continents and surrounding islands lie barriers called coral reefs. Coral isa living organism consisting of animal and algae tissues. Corals feed like plants through the process ofphotosynthesis, and like animals, they also use their tentacles to catch micro-organisms. The coral reef is also hostto other species such as starfish, octopi, and other molluscs.

Out in the open ocean is what is called the pelagic zone , which is host to many species of fish and marine mammals,plankton, and some floating seaweed. The area underneath the pelagic zone is called the benthic zone , or deep-sea, and is host to silt, sand, and slowly decomposing organisms. This area is very cold due to its depth, which is

untouched by the light of the sun. There are few plants at this level, and the animals include mostly bottom feedingorganisms such as starfish, anemones, sponges, amongst others, as well as various micro-organisms.

The deepest part of the ocean is called the abyssal zone . It is host to many species of invertebrates and fish includingsuch oddities as the coelacanth , a prehistoric fish once thought extinct and found in the depths of the Indian Ocean,and other fish that glow in the dark via a process called photoluminescence. The abyssal zone is very cold, and highlypressurized. Its floor features vents formed by spreading tectonic plates which release hydrogen sulphide andother minerals which are consumed by the bacteria which are then consumed by other micro-organisms, which arein turn, consumed by the fish, and so on.


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Tundra

ARCTIC TUNDRA

The arctic tundra occupies earth's Northern hemisphere, circling the North Pole all the way down to the evergreenforests of the boreal biomes. The arctic tundra sees little rainfall, like the cold deserts of Russia. The soil of thearctic tundra is poor in nutrients, which accounts for the low amount of vegetation. There is an under-layer of soilcalled permafrost which remains completely frozen at all times, allowing little room for deep rooting plants andtrees. The plants that do survive the frozen landscapes are extremely resilient, and their roots are close to thesurface of the hard soil, as to intake what little water falls upon the ground; most of the arctic tundra's plant lifeconsists of shrubbery, lichen, moss, and flowers. Icy rivers flow through the tundra to the Arctic Ocean, and arehome to trout, salmon and other freshwater fish. Sometimes rainfall produces small, temporary ponds, whichserve as mating areas for flies and mosquitoes.

Other animal species occupying the tundra consist of polar bears, caribou, musk ox, grey wolves, lemmings,rabbits, squirrels, and birds such as penguins, falcons, ravens, terns, and loons. All are greatly adapted to theirenvironment, with extra layers of fat, and the ability to hibernate during the colder months, although this hasmore to do with the lack of food than the cold. Birds of the tundra migrate south during the winter months,causing constant change in the animal population.


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ALPINE TUNDRA

The alpine tundra biome exists on rocky mountaintops and is very similar to the arctic tundra except for aconspicuous lack of trees. Because trees cannot grow at this high altitude, most of the alpine tundra plant lifeconsists of shrubbery and small leafy plants such as alpine bluegrass which serve as dinner to a variety of grazinganimals such as bighorn sheep and mountain goats. Other alpine tundra animals include elk, pika, marmots, andbirds such as the white-tailed ptarmigan and the grouse, and a few insects like grasshoppers, bumblebees, andbeetles.


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INSIGHTSRAINFORESTThere are two types of rainforests, tropical and temperate. Tropical rainforests are found closer to the equatorwhere it is warm. Temperate rainforests are found near the cooler coastal areas further north or south of theequator.

The tropical rainforest is a hot, moist biome where it rains all year long. It is known for its dense canopies ofvegetation that form three different layers. The top layer or canopy contains giant trees that grow to heights of 75m (about 250 ft) or more. This layer of vegetation prevents much of the sunlight from reaching the ground. Thick,woody vines are also found in the canopy. They climb trees in the canopy to reach for sunlight. The middle layer, orunderstory, is made up of vines, smaller trees, ferns, and palms. A large number of plants from this level are usedas common houseplants. Because of the small amount of sunlight and rainfall these plants receive, they adapteasily to home environments. The bottom layer or floor of the rainforest is covered with wet leaves and leaf litter.This material decomposes rapidly in the wet, warm conditions (like a compost pile) sending nutrients back into thesoil. Few plants are found on the floor of the forest due to the lack of sunlight. However, the hot, moistatmosphere and all the dead plant material create the perfect conditions in which bacteria and othermicroorganisms can thrive.

DESERTDesert biomes are the driest of all the biomes. In fact, the most important characteristic of a desert is that itreceives very little rainfall. Most deserts receive less than 300 mm a year compared to rainforests, which receiveover 2,000 mm. That means that the desert only gets 10 percent of the rain that a rainforest gets! The temperaturein the desert can change drastically from day to night because the air is so dry that heat escapes rapidly at night.The daytime temperature averages 38°C while in some deserts it can get down to -4°C at night. The temperaturealso varies greatly depending on the location of the desert.

Since desert conditions are so severe, the plants that live there need to have adaptations to compensate for thelack of water. Some plants, such as cacti, store water in their stems and use it very slowly, while others like bushes

conserve water by growing few leaves or by having large root systems to gather water or few leaves. Some desertplant species have a short life cycle of a few weeks that lasts only during periods of rain.

GRASSLANDGrasslands are generally open and continuous, fairly flat areas of grass. They are often located between temperateforests at high latitudes and deserts at subtropical latitudes. Grasses vary in size from 2.1 m (7 ft) tall with rootsextending down into the soil 1.8 m (6 ft), to the short grasses growing to a height of only 20 to 25 cm (8 to 10 in)tall. These short grasses can have roots that extend 1 m (about 3 ft) deep.

The height of grass correlates with the amount of rainfall it receives. Grasslands receive about 500 to 900 mm ofrain per year compared to deserts, which receive less than 300 mm and tropical forests, which receive more than

2,000 mm. While temperatures are often extreme in some grasslands, the average temperatures are about -20°Cto 30°C. Tropical grasslands have dry and wet seasons that remain warm all the time. Temperate grasslands havecold winters and warm summers with some rain.

The grasses die back to their roots annually and the soil and the sod protect the roots and the new buds from thecold of winter or dry conditions. A few trees may be found in this biome along the streams, but not many due tothe lack of rainfall.


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TUNDRAThe tundra is the coldest of the biomes. It also receives low amounts of precipitation, making the tundra similar toa desert. Tundra is found in the regions just below the ice caps of the Arctic, extending across North America, toEurope, and Siberia in Asia. Much of Alaska and about half of Canada are in the tundra biome. Tundra is also foundat the tops of very high mountains elsewhere in the world. Temperatures are frequently extremely cold, but canget warm in the summers.

Tundra winters are long, dark, and cold, with mean temperatures below 0°C for six to 10 months of the year. The

temperatures are so cold that there is a layer of permanently frozen ground below the surface, called permafrost.This permafrost is a defining characteristic of the tundra biome. In the tundra summers, the top layer of soil thawsonly a few inches down, providing a growing surface for the roots of vegetation.

AQUATICWithout water, most life forms would be unable to sustain themselves and the Earth would be a barren, desert-likeplace. Although water temperatures can vary widely, aquatic areas tend to be more humid and the air temperatureon the cooler side. Water is the common link among the five biomes and it makes up the largest part of thebiosphere, covering nearly 75% of the Earth`s surface. Aquatic regions house numerous species of plants andanimals, both large and small. In fact, this is where life began billions of years ago when amino acids first started tocome together. The aquatic biome can be broken down into two basic regions, freshwater (i.e, ponds and rivers)

and marine (i.e, oceans and estuaries).

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