The document discusses major ecosystems of the Earth. It defines an ecosystem as consisting of biotic (living) and abiotic (non-living) components that interact. The major ecosystems discussed are aquatic ecosystems including freshwater, estuarine, and marine ecosystems, and terrestrial ecosystems. Specific biomes within terrestrial ecosystems mentioned include alpine, chaparral, and tropical rainforests.

1. 2014
Ugo Kelechi
Universityof Lagos
6/16/2014
Major ecosystems of the Earth

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MAJOR ECOSYSTEMOF THE WORLD
WHAT IS AN ECOSTSTEM?
An ecosystem is made up of living organisms (biotic) and their surrounding non-living
component (abiotic) e.g. air living in an environment in which a continuous interrelationship
between the two occur.
Components of an Ecosystem
ABIOTIC COMPONENTS
Sunlight, Temperature, Precipitation, Water or moisture Soil or water (e.g., P, NH4) etc.
BIOTIC COMPONENTS
Primary producers e.g. plant, Herbivores e.g. buffalo, Carnivores e.g. hyena, Omnivores e.g.
man, Detritivores and decomposers e.g. earthworm.
These biotic and abiotic components are linked together through nutrient cycles and energy
flows. As ecosystems are defined by the network of interactions among organisms, and
between organisms and their environment, they can come in any size but usually
encompass specific, limited space. (Although some scientists say that the entire planet is an
ecosystem).

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From wibley.com
MAJOR ECOSYSTEMS IN THE WORLD
Major classes of relatively contained ecosystems are called Biomes. Biomes are climatically
and geographically defined as similar climatic conditions on the Earth, such as communities
of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts
of the earth have more or less the same kind of abiotic and biotic factors spread over a large
area, creating a typical ecosystemover that area. Such major ecosystems are termed as
biomes. Biomes are defined by factors such as plant structures (such as trees, shrubs, and
grasses), leaf types (such as broadleaf and needle leaf), plant spacing (forest, woodland,
savanna), and climate. Biomes are often identified with particular patterns of ecological
succession and climax vegetation (quasi equilibrium state of the local ecosystem). An
ecosystem has many biotopes and a biome is a major habitat type. Some examples of
habitats are ponds, trees, streams, creeks, and burrows in the sand or soil.
There are 2 major classes of Ecosystems: ‘Aquatic Ecosystem’ and ‘Terrestrial Ecosystems’.

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Aquatic biomes are ecosystems that flourish under water. The life itself was originated
from an aquatic environment and it is about ¾ of the total earth’s surface. Depending on
the salinity of the water and the aquatic environment, the aquatic biome can be divided into
the following categories:
1. FRESH WATER ECOSYSYSTEM: They contain relatively small area of earth's surface
(1.8%) and they include lakes and ponds, rivers, streams and springs, and wetlands
which support many species of life including fish, amphibians, insects and plants.
Freshwater habitats can be classified by different factors, including temperature,
light penetration, and vegetation.
Freshwater ecosystems can be divided into lentic ecosystems (still water) and lotic
ecosystems (flowing water). They are characterised with low or no salt
concentration. The base of food-web is also found in freshwater Plankton
(small microscopic organisms). Generally the fresh water habitat can be divided into
two types:
(a)Moving water ecosystems: They include rivers and streams, since they originate
from one place, and traverse over some distances, passing through different terrains
and areas and their abiotic factors also undergo changes. Examples of such moving
water include Nile of Egypt, amazon of Africa and Ganges of India.
(b)Standing water ecosystems: Standing water bodies include ponds, marshes and
lakes. The sediments flowing into a lake or pond, eventually fills up a water and turns
it into marsh and then finally into the forest. The standing water bodies do not have
any flow velocity or current, though winds may produce wave action in large sized
lakes. Penetration of light in the lake will depend upon its depth and the sediment
brought in regularly into the lake by the water flowing into the lake. Dissolved gases,

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like oxygen, carbon dioxide are not uniformly distributed, and their distribution is
controlled by factors such as temperature, rate of photosynthesis.
2. EUTUARINE ECOSYSTEM: This is an outfall reach of a river in which the back
water if an ocean during high tides comes in contact with the river current. It
represents a transition zone between the river and the sea. As the sea water backs
up at the time of high tide, the sea water mixes with the river water, creating a zone
of water with intermediate salinity. At the time of low tide, the sea water receding
towards the sea is joined by more river water, which further reduces its salinity.
3. OCEAN/MARINE ECOSYSTEM : They contain very large amount of the Earth’s
surface about (75%) which is about two-thirds of the surface of the earth with high
concentration of salt in its water. They include oceans, salt marsh and lagoons,
mangroves and coral reefs, the deep sea and the sea floor. Such places are
considered ecosystems because the plant life supports the animal life. Marine
ecosystems are very important for the overall health of both marine and terrestrial
environments. According to the World Resource Centre, coastal habitats alone
account for approximately 1/3 of all marine biological productivity, and estuarine
ecosystems (i.e., salt marshes, sea grasses, mangrove forests) are among the most
productive regions on the planet. In addition, other marine ecosystems such as coral
reefs provide food and shelter for all marine habitats such as fishes. Marine
ecosystems usually have a large biodiversity and are therefore thought to have a
good resistance against invasive species.
TERRESTIAL ECOSYSTEMS: The terrestrial Ecosystems which is also known as
land habitat are found on landforms, it’s also a community of organisms and their

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environment that occurs on the land masses of continents and islands which
contains more species than other biomes with precipitation of 250cm per year.
Terrestrial ecosystems are distinguished from aquatic ecosystems by the lower
availability of water and the consequent importance of water as a limiting factor.
Terrestrial ecosystems are characterized by greater temperature fluctuations on
both a diurnal and seasonal basis than occur in aquatic ecosystems in similar
climates. The availability of light is greater in terrestrial ecosystems than in aquatic
ecosystems because the atmosphere is more transparent than water. Gases are
more available in terrestrial ecosystems than in aquatic ecosystems. Those gases
include carbon dioxide that serves as a substrate for photosynthesis, oxygen that
serves as a substrate in aerobic respiration, and nitrogen that serves as a substrate
for nitrogen fixation. Terrestrial environments are segmented into a subterranean
portion from which most water and ions are obtained, and an atmospheric portion
from which gases are obtained and where the physical energy of light is transformed
into the organic energy of carbon-carbon bonds through the process of
photosynthesis. Terrestrial ecosystems occupy 55,660,000 mi2 (144,150,000 km2),
or 28.2%, of Earth's surface. Although they are comparatively recent in the history of
life (the first terrestrial organisms appeared in the Silurian Period, about 425 million
years ago) and occupy a much smaller portion of Earth's surface than marine
ecosystems, terrestrial ecosystems have been a major site of adaptive radiation of
both plants and animals. Major plant taxa in terrestrial ecosystems are members of
the division Magnoliophyta (flowering plants), of which there are about 275,000
species, and the division Pinophyta (conifers), of which there are about 500 species.
Members of the division Bryophytes (mosses and liverworts), of which there are

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about 24,000 species, are also important in some terrestrial ecosystems. Major
animal taxa in terrestrial ecosystems include the classes Insecta (insects) with about
900,000 species, Aves (birds) with 8500 species, and Mammalia (mammals) with
approximately 4100 species. Terrestrial habitat can also be sub-divided into the
following…
1. THE HIGHLAND ICY ALPINE BIOME: The word ‘alpine’ is gotten from a Latin
world ‘alp’ which means high mountain areas. This is a biome of high mountain
areas, having snow, high winds, ice, and that is typical in winter season. The
alpine environment usually exists on mountains at an altitude of about 3000m or
more. In the alpine biome, the summer temperature may range from 10 to 15◦c;
but in winter, the temperatures are below freezing point. The highland icy
mountain extends in Asia covering most part of India, Nepal, Bhutan, china and
Russia.
2. THE CHAPPARAL BIOME: This biome is found in a little bit of most of the
continents such as the west cost of U.S.A., the west coast of south America, the
cape town area of south Africa , the western tip of Australia etc. the chapparal
biome has different types of terrain, like flat plains, rocky hills, and mountain
slopes. It is characterised by hot and dry climate, with temperature of 10◦c
during winter and 40◦c during summer. The plants and animals that are adapted
to this climatic conditions include scrub oak, cacti, alligator, honey bee, ladybugs
etc.
3. TROPICAL RAINFOREST: A tropical rainforest is an ecosystemtype that occurs
roughly within the latitudes 28 degrees north or south of the equator (in the
equatorial zone between the Tropic of Cancer and Tropic of Capricorn). The

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tropical rain forest now covers less than 6% of the earth’s land surface, and yet
more than 50% of all the worlds’ plant and animal’s species live in these forests.
These forests also produce about 40% of the earth’s oxygen due to high degree
of photosynthesis. This ecosystem experiences high average temperatures about
20 -30 degree Celsius, humidity and a significant amount of annual rainfall about
125-650 cm. Rainforests can be found in Asia, Australia, Africa, South America,
and Central America, Mexico and on many of the Pacific, Caribbean, and Indian
Ocean islands. Within the World Wildlife Fund's biome classification, tropical
rainforests are thought to be a type of tropical wet forest (or tropical moist
broadleaf forest).
The Amazon Rainforest South America
Types of tropical rainforest

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Lowland equatorial evergreen rain forests: are forests which receive high
rainfall (more than 2000 mm, or 80 inches, annually) throughout the year. These
forests occur in a belt around the equator, with the largest areas in the Amazon
Basin of South America, the Congo Basin of Central Africa, Indonesia, and New
Guinea.
Moist deciduous and semi-evergreen seasonal forests: They receive high
overall rainfall with a warm summer wet season and a cooler winter dry season.
Some trees in these forests drop some or all of their leaves during the winter dry
season. These forests are found in parts of South America, in Central America
and around the Caribbean, in coastal West Africa, parts of the Indian
subcontinent, and across much of Indochina.
Montane rain forests: They are also known as cloud forests, are found in
cooler-climate mountain areas. Depending on latitude, the lower limit of
montane rainforests on large mountains is generally between 1500 and 2500 m
while the upper limit is usually from 2400 to 3300 m.
4. SAVANNA: A savanna is also part of the terrestrial ecosystem with Precipitation
of about 90-150cm/year, Open, widely spaced trees, seasonal rainfall and can be
found in areas like Parts of Africa, South America & Australia. It characterized by
the trees being sufficiently widely spaced so that the canopy does not close. The
open canopy allows sufficient light to reach the ground to support an unbroken
herbaceous layer consisting primarily of grasses. Some classification systems also
recognize a grassland savanna from which trees are absent. This article deals

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only with savanna under the common definition of grassy woodland with a
significant woody plant component. It is often believed that savannas feature
widely spaced, scattered trees. However, in many savannas, tree densities are
higher and trees are more regularly spaced than in forest. Savannas are also
characterized by seasonal water availability, with the majority of rainfall confined
to one season. Savannas are associated with several types of biomes. Savannas
are frequently in a transitional zone between forest and desert or grassland.
Savanna covers approximately 20% of the Earth's land area.
5. DESERT:-
This is an ecosystemwhich contains a region of arid land due to low amount of
rainfall 20cm/year, high level of evaporation and often with dry, sparse
vegetation; scattered grasses, and in which streams dry up unless they are
supplied by water from outside areas. Deserts can also be described as areas
where more water is lost by evapotranspiration than falls as precipitation. Desert
plants must have special adaptations to survive with this little water. Deserts
generally receive less than 25 cm of rain (precipitation) each year. Deserts take
up about one third (33%) of the Earth's land surface. Semi deserts or steppes are
regions which receive between 250 millimetres (10 in) and 400 to 500millimetres
rainfall.

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Sahara desert North Africa
Deserts can also be classified into ‘hot desert’ with annual rainfall of about 25cm
and high evaporation potential. They can be found in the tropical regions e.g.
Kalahari Desert and Sahara desert and the ‘cold desert’ which is lands with
temperatures below 0◦c covered with snow or ice which makes it inhabitable for
plant life. Examples include Arctic desert and Antarctic deserts.
6. TEMPERATE GRASSLAND: The temperate grassland is a terrestrial biome with
predominant vegetation consisting of grasses and shrubs. The climate is
temperate and ranges from semi-arid to semi-humid. Characteristics of
temperate grassland include: rainfall of 10-60cm/year, warm to hot season
(often with a cold to freezing season in winter), and Rich soil with fertile with rich
nutrients and minerals; tall dense grasses, trees or shrubs with large, grazing
mammals; birds; reptiles. They can be found in areas like Central North America;
Central Asia. E.g. The California Central Valley Grassland.
7. DUCIDUOUS FOREST: The deciduous forest typically contains large broad leaf
trees as their dominant vegetation. These trees shed their leaves and become
leaves in winter. The commonest of trees that can be found incudes oaks,
chestnut, beech, maple and magnolia. They survive under the conditions of

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temperature and somewhat cold climate (annual average temperature being of
the order of 10 degree Celsius) which is generally near warm with rainfall of
about 75-125 cm annually. Rain falls periodically throughout the year, even as
winter snow may fall in some part. Minimum temperatures may reach as low as -
12◦c in winter; while in summers, it may be as warm as 25◦c. The deciduous
forest exist in mid-latitudes in both hemisphere such as areas like Europe, North
east America, and central Asia.
8. THE TUNDRA BIOME: This biome includes the dry treeless cool land extending
from polar icecaps down to the forest limit. It includes all the lands masses near
the poles. In the northern hemisphere, near the arctic, a lot of land exists in this
biome, and it’s usually called the arctic tundra. While in the southern
hemisphere, very little land exists near the South Pole apart from Antarctica, and
this portion is called Alpine Tundra. The tundra is the world’s youngest biome
located at altitude 55 to 70◦ north. The tundra has vast treeless lands, covering
about 20% of the total earth land surface.
9. THE TAIGA BIOME (coniferous forest biome): This biome consists of main taiga,
which is a Russian word for forest. The taiga is located near the top of the world,
below the tundra biome. The taiga stretches over Eurasia and North America,
and it’s the largest biome on the world. The taiga forests are also known as
boreal forest. Since these forest consist of needle leaf trees, this biome is also
known as coniferous forest biome. The winters in taiga are very cold with only
snowfall. The summers are warm, rainy, and humid. The average temperature is
below freezing six month a year. The total amount of precipitation in this kind of

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biome is about 30 to 35 cm. the taiga biome kind be found in areas such as the
temperate coniferous forest in western north America.
References
Santos, K. G.; Rajeshwari, G.; Dr. Ranjini, G. “ENVIRONMENTAL SCIENCE AND
ECOLOGICAL STUDIES.
NATIONAL GEOGRAPHIC INFORMATION
GEOLOGY.COM