Here is a compilation of essays on ‘Biosphere’ for class 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Biosphere’ especially written for school and college students.
Essay on Biosphere
- Essay on the Definition of Biosphere
- Essay on the Concept of Biosphere
- Essay on the Sub-Systems of Biosphere
- Essay on the Components of Biosphere
- Essay on the Habitat of Biosphere
- Essay on Energy-Flow in the Biosphere
- Essay on the Functional Classification of Biospheric Elements
Essay # 1. Definition of Biosphere:
Biosphere is that part of the earth where life exists. The geographical distribution of living organisms reveals that living creatures are found in different sets of environmental conditions. The scientists have discovered many kinds of organisms. Earlier, they were classified into two groups—the plant kingdom and the animal kingdom.
The science of classification of organisms is called Taxonomy. In 1969, Whittaker divided all organisms into five kingdoms based on the complexity of cell structure, organisms’ body and mode of obtaining nutrition.
1. Monera (single cell microscopic organisms) like—bacteria
2. Protista (unicellular, primarily aquatics organisms) like—phytoplankton
3. Plantae (multicellular phytosynthetic plants) like—sea weeds, algae, mosses, ferns and seed plants.
4. Fungi (multicellular decomposers) like—yeasts, mushrooms etc. There are over 100,000 species of fungi.
5. Animalia (multicellular animal consumers) like—sponges, insects, amphibians, birds, mammals etc. There are several species under each kingdom. This group also includes human beings. The human beings are called Homo sapiens (homo means man and sapiens means wise).
The environment means surroundings. It is a collective term embracing all conditions in which an animal lives. There are two types of conditions—physical or abiotic such as air, soil, water, light, temperature, precipitation and biotic conditions which surround and affect the life of the organisms.
The life of living organisms is so intimately related with the environmental factors of a place that every living being is perfectly adapted to a particular environment.
All the organisms whether plants or animals interact with each other. The study of these interactions between all forms and environment is called ecology. The term ecology has been derived from the Greek word ‘oikos’ which means ‘house’ and ‘logy’ means ‘science’ or ‘study of’.
The German Sociologist Earnst Hackel used the term ‘oekologie’ in 1869 and he became the first person to use the term. All the interacting components—biotic and abiotic with the group of organisms—are called ecosystem.
Essay # 2. Concept of Biosphere:
The biosphere is a life supporting layer which surrounds the earth and makes plant and animal life possible without any protective device. The ‘organic world or biosphere is that part of the earth which contains living organisms – the biologically inhabited soil, air and water’.
The biosphere consists of all the living organisms (the biotic component), energy (the energy component) and physical environment (the abiotic component) and there are continuous interactions between living organisms and physical environment and among the living organisms themselves.
The average thickness of the biosphere or life supporting layer consisting of air, water, soil and rock is about 30 km. The upper limit of the biosphere is determined by the availability of oxygen, moisture, temperature and air pressure. Decrease in oxygen, moisture, temperature and air pressure with increase in height in the atmosphere limits the upper boundary of the biosphere.
Though the NASA has discovered the presence of bacteria upto the height of 15 km in the atmosphere but the lower layer of the atmosphere upto a few hundred meters accounts for most of the living organisms because favourable environmental conditions are available for the growth and development of living organisms in the lower part of the atmosphere.
The lower limits of the biosphere are determined by the availability of required amount of oxygen and light which can sustain life. Thus, the depth of the biosphere over the land is upto the depth of the deepest roots of the trees or the depth upto which can live the burrowing organisms or the depth at which lie the parent bed-rocks.
The biosphere extends upto greater depth in the oceans. The existence of life has been detected upto a depth of 9,000m in the deep oceanic trenches and deep sea plains (fig. 40.1).
Essay # 3. Sub-Systems of Biosphere:
The biosphere consists of two major systems viz.:
(i) Terrestrial biomes systems, and
(ii) Aquatic biomes systems.
The terrestrial biomes systems are further comprised of three subsystems viz.:
(i) Plant system,
(ii) Animal system, and
(iii) Soil system.
These subsystems are intimately interrelated among themselves through the cyclic pathways of movements and transfer of energy and materials (fig. 40.2) whereas the aquatic biomes systems are also composed of three sub-systems viz.:
(i) Plant system,
(ii) Animal system, and
These three sub-systems of aquatic biomes system of the biosphere are also intimately interrelated through cyclic pathways of movements of energy and matter among themselves.
The biospheric ecosystem is affected and modified by certain factors either directly or indirectly.
These factors are called as modifiers of ecosystems.
The factors or modifiers which directly or indirectly affect ecosystems are of three categories e.g.:
(i) Physical modifiers,
(ii) Chemical modifiers, and
(iii) Biological modifiers.
The physical factors affect physical properties of the atmosphere which in turn affect climate and climate ultimately affects the ecosystems.
Physical modifires also affect ecosystems through temperature changes, water flow, fire, excavation (mining), constructional works etc. The chemical factors affect the composition of the atmosphere which in turn affects climate which ultimately affects the ecosystems.
Water and soil composition is highly modified by chemical elements and thus modified soil and water affect the ecosystems. The biological factors like cropping patterns, population characteristics, manipulation of species density and distribution and species genetics also affect the ecosystems.
Essay # 4. Components of Biosphere:
If we consider the whole of the biosphere as an ecosystem at global scale, the components of the biosphere and the biospheric ecosystem become the same. The total physical environment at global scale also contains the same components as those of the biosphere and the ecosystem (biospheric ecosystem).
The biosphere, the ecosystem and the environment consist of three components viz.:
(i) Inorganic or abiotic or physical components,
(ii) Energy component, and
(iii) Biotic or organic component.
It may be pointed out that energy component may also be considered with abiotic component.
1. Abiotic Components:
The abiotic or inorganic or physical component of the bisophere or the ecosystem represents physical environment of the whole biosphere or part thereof. This component, on an average, includes the lithosphere, the atmosphere and the hydrosphere.
Generally, these are considered as land and or soil, air and water respectively. If the whole of the biosphere is taken to be an ecosystem at global scale, these three physical or abiotic components are considered as the sub-systems of biospheric system (ecosystem).
In other words abiotic components of the biosphere consist of 3 sub-components viz., lithospheric component (land component), atmospheric component (air component) and hydrospheric component (water component).
Only summary of these components is reproduced here. It is significant to note that though biotic components of the biosphere are most significant aspects of the study of biogeography but abiotic components involving land, air and water are also studied in this discipline.
(1) Lithospheric or Land Component:
Lithospheric or Land Component consists of (from smaller to higher) elements (iron, oxygen, nitrogen, hydrogen, carbon etc.), minerals (hematite, dolomite, felspar etc.), rocks and soils, microland forms (relief features of 3rd order viz., erosional and depositional landforms produced by exogenetic denudational processes like running water-fluvial process, groundwater, sea waves-marine process, wind- aeolian process, glaciers and periglacial process), meso- landforms (relief features of 2nd order produced by endogenetic forces namely, mountains, plateaus, faults, folds etc.) and macro-landforms (relief features of 3rd order e.g., continents and ocean basins).
The lithosphere accounts for about 29 per cent of the total surface area of the globe. The landforms of various sizes as mentioned above provide a variety of habitats for the plants and animals. Thus, it is necessary to study the main characteristics of lithospheric components and all the physical processes, whether exogenetic or endogenetic, which affect the lithosphere – the surface of the earth.
The geological cycle involving a set of processes and sub-cycles e.g., tectonic cycle, rock cycle, geochemical cycle, water cycle etc., is responsible for the creation, maintenance, changes or destruction of the materials of the earth for example-elements, minerals, rocks, soils, water and the landform assemblage.
Soil system is very important component because soils act as a vital transfer pathways of energy in the biosphere and are very important for the biological cycling of nutrients. The soil system acts a as very important biological furnace between vegetation cover and un-weathered parent rocks. Soil environment also provides habitats of various sorts to the largest community of organic life (biological community).
On the other hand, soils act as nutrient reservoirs for living organisms. Soils facilitate the process of root osmosis for the transfer of their nutrients to the plants though their roots in solution form. Soil system is also called as a biological factory or laboratory because the processes of creation of rutrients, their consumption and their return are confined to soils.
(2) Atmospheric or Air Component:
The atmosphere is a significant component of the biospheric ecosystem because it provides all the gases necessary for the sustenance of all life forms in the biosphere. It also filters the incoming solar radiation and thus prevents the ultraviolet solar radiation waves to reach the earth’s surface and hence protects it from becoming too hot.
The atmospheric component includes the consideration of the composition and structure (troposphere, stratosphere, mesosphere, thermosphere-iono- sphere and exosphere) of the atmosphere and the elements of weather and climate (insolation, temperature, air pressure, winds, humidity and precipitation, air masses, frontogenesis and fronts, cyclones and anticyclones etc.).
The atmosphere helps in the process of photosynthesis and drives hydrological cycle.
(3) Hydrospheric or Water Component:
The water or hydrospheric component is very important component of the abiotoc or physical components because it is very essential element for all types of life in the biosphere. Water plays very important role in the circulation of nutrients in the various components of the ecosystems and it makes biogeochemical cycles effective in the biosphere.
The water components consist of surface water, subsurface or groundwater and oceanic water. Surface water of the earth surface is found in static state (e.g., water of lakes, ponds, tanks, reservoirs etc.) and in dynamic (in motion) state (e.g. surface runoff, streams, springs etc.). The groundwater is found in the pore spaces of regolith known as aquifers.
The oceanic water or hydrosphere covers about 71 per cent of the total surface area of the globe. On the basis of size and location the hydrosphere is divided into oceans, seas, small enclosed seas, bays etc. The hydrospheric component includes the consideration of origin and characteristics of bottom reliefs (continental shelves, continental slopes, deep sea plains, deeps, submarine canyons etc.), temperature, salinity, ocean deposits, waves and currents, coral reefs and atolls because these determine different types of habitats of marine organisms.
2. Biotic Components:
Biotic or organic components of the biosphere consist of three subsystems e.g.:
(1) Plant system,
(2) Animal system including man, and
Of these three sub-systems plants are the most important because plants alone produce organic matters which are used by themselves and by animals including micro-organisms either directly or indirectly. Plants also make the cycling and recycling of organic matter and nutrients possible in different components of the biospheric ecosystem.
(1) Plant Component:
Social grouping of plant species is called plant community and plants are basic unit of this community. Plants are found on any land in different forms e.g., woodland, forest, meadows, bogs, grassland, marshlands etc. These different forms of plants are collectively known as vegetation.
In other words, ‘all the plants which grow together in any area form its vegetation, the character of which depends not just on the different species present but on the relative proportions in which their members are represented’.
Thus, the vegetation of any particular habitat consists of groups of plants of different species or of the same species which are ecologically related, meaning thereby different plant groups are able to occupy the same habitat because of their competitive ability and range of tolerance.
Plant community has been defined in a variety of ways by ecologists and bio-geographers e.g.:
(1) Social groupings of plant species are called plant community.
(2) Plant community represents groups of plants which occur together and possess a certain degree of unity of individuality.
(3) Plant community is a group of plants which occupy a definite physical habitat.
(4) Plant community refers to groups of plant species which have distinctive characteristics of their composition and structure in relation to their physical habitat.
There are certain characteristics of plant community e.g.:
(i) Plant community consists of two or more different species of plants.
(ii)The plant species of plant community are capable of growing together in a particular physical habitat which they inhabit and thus different members (species) of a plant community are ecologically interrelated.
(iii) A plant community has a well-defined composition and structure which are attained over time through the interactions between different plant species and between plant and their physical environment.
(iv) Plant community represents the ecological conditions of a region or an area or a physical habitat.
(v) The structures, composition and growth form of different species of a given plant community reveal the effects of both mutually interacting biotic and abiotic environments on them.
In other words, this is well known fact that the species of plants, their structure, composition and growth form depend upon the nature of mutual interactions between abiotic and biotic components of the environment, it is easier to understand the nature and pattern of mutual interactions of factors (components, both abiotic and biotic) which affect the species, their structure, composition and growth form. Out of the abiotic or physical factors, climate and soil mostly affect the species of plants, their structure and growth form.
In turn plants also affect and control the properties of soils and climatic conditions of their physical habitat. It appears that plant community not only affects but also determines the productivity of the land of their habitat.
Plants are primary producers because they produce their food themselves through the process of photosynthesis. Thus, plants are also called autotrophs. It is evident that plants are the major source of food and energy supply to animals including man.
The study of plant components includes the consideration of:
(i) Classification of plants,
(ii) Major divisions of plant kingdoms,
(iii) Plant system,
(iv) Plants and their environment,
(v) Plant communities (including vertical structure, species composition, community development and community hierarchy),
(vi) Plant evolution, and
(vii) Distribution, dispersal and extinction of plants etc.
(2) Animal Components:
On a functional basis the biotic or organic components of biospheric ecosystem are divided into two broad divisions e.g.:
(i) Autotrophic component (which represents plants. These have been briefly discussed above), and
(ii) Heterotrophic component includes those animals which depend on autotrophic green plants (primary producers, which produce their food themselves.
It may be pointed out that it is not necessary that plants always have roots, this is the reason that some bacteria also fall in the category of plants because they produce their food themselves) for their food.
The main functions of heterotrophic components or animals (primary consumers) include:
(i) To use organic matter made available by the autotrophic green plants,
(ii) To rearrange the organic matter/elements, and
(iii) To decompose organic elements etc.
Organic matters are available to animals in three forms e.g.:
(i) From living plants and animals,
(ii) From partially decomposed plants and animals, and
(iii) From organic compounds in solution form.
Thus, heterotrophic animals are classified into 3 broad categories on the basis of the availability of organic matter to them:
(A) Saprophytes are those animals which live on organic compounds in solution form derived from dead plants and animals.
(B) Parasites are those animals which depend on other living organisms for their food and life.
(C) Hoiozonic animals are those who take their food through their mouths. All the big animals like elephants, cows, camels, lions etc. are included in this category.
Micro-organisms are also known as decomposers because these decompose the dead plants and animals and other organic matter in different forms. During the process of decomposition of organic matter micro-organisms obtain their food as well as they differentiate and separate complex organic matters and thus make them simple so that these may be again used by autotrophic primary producer green plants. A large number of microbacteria and fungi are included in the category of micro-organisms.
There are three stages of the study of animals and micro-organisms e.g.:
(1) Identification of all animals and micro-organisms in a given region,
(2) Classification of all identified animals and micro-organisms, and
(3) The study of distributional patterns, evolution and extinction of animals.
It is significant to point out that animal kingdom includes a variety of animals and micro-organisms ranging from microscopic organisms to giant whales. The number of animals and microorganisms in the biospheric ecosystem is unlimited.
Though all organisms in the biosphere could not be identified and named yet animals are classified into seven successive groups (from higher order to lower order) on the basis of available knowledge e.g.:
(i) Animal kingdom,
(vi) Genera, and
The distribution of animals, their evolution, dispersal, extinction, relationships between animals and their physical environment, the roles of animals in the ecosystems, relationships between plants and animals and their physical environment.
The other properties of ecosystems viz., ecosystem productivity, ecosystem stability and instability etc. Energy flow in the ecosystem (sources of energy, ecological production, trophic levels, food chains, ecological pyramids, flow of energy etc.) and circulation of elements in the ecosystem.
Essay # 5. Habitat of Biosphere:
The natural home or environment of an animal, plant or other organism. The habitat must offer food, shelter and climatic conditions which will be well suited for the organism to survive, breed and flourish. The habitat is a part of the total environment. A habitat comprises of both biotic and abiotic components.
For example, the habitat of a tiger must have small animals for the tiger to hunt and feed on. It should have thick vegetation in the form of shady trees and shrubs where tiger can hide and lie in wait for its prey. These components may not be available in all forests and so is the tiger.
The total life-containing and life-supporting environment of the world is restricted to a very thin and irregular veil around the globe. The total thickness of biosphere is about 21 km (10 km in air and 11 km in water from the earth’s surface).
The biosphere consists of three major types of habitats:
(i) Aquatic Habitat,
(ii) Terrestrial Habitat, and
(iii) Aerial or Arboreal Habitat.
(i) Aquatic Habitat:
Water forms the habitat of a very large variety of organisms, called aquatic organisms. Some well-known aquatic organisms are algae, fishes and whales. If they live and breed in sea water, they are called marine and if they live and breed in pond, lake, river, they are called fresh water organisms. Fresh water habitat may be lentic pertaining to still water as lakes, ponds or bogs, or it may be lotic pertaining to running water as rivers, streams, brooks, etc.
(ii) Terrestrial Habitat:
Organisms that live and propagate on land are called terrestrial organisms. Trees, elephants, men, tigers and so on are some of the examples of this kind.
(iii) Aerial or Arboreal Habitat:
The organisms that use air (sky) for their activities are called aerial or arboreal organisms. Birds fall under this category.
In addition to the above, some organisms’ life like frogs, crocodiles etc. use both water and land as their habitat and are called amphibious organisms.
Essay # 6. Energy Flow in the Biosphere:
All organisms need food as a source of energy for growth and reproduction.
On the basis of feeding habits organisms may be divided into three major groups:
(ii) Consumers ,
(i) Producer organisms:
Producer organisms are able to manufacture their own food from solar energy through the process of photosynthesis. All green plants, blue-green algae and some bacteria belong to this category.
(ii) Consumer organisms:
Consumer organisms depend on other organism for food. Animals fall in this group. Consumers are divided into two categories—carnivores and herbivores. Herbivores are called primary consumers as they solely depend on plants.
For example, deer, horse, zebra etc. Carnivores are secondary consumers as they depend on herbivores. For example, tiger, lion, etc. Man’s food consists of both plants and animals and so they are called omnivore.
Decomposers causes a substance to rot or break up in to simpler part. It help to decompose dead plants and animals. They depend only on decomposition, as their food. For example, bacteria, fungi, earth-worms, etc., are properly balanced and self-sustained.
Essay # 7. Functional Classification of Biospheric Elements:
Elements of the biosphere are divided in four categories on functional basis:
(1) Abiotic (physical) elements include basic elements of the habitats and dead organic compounds.
(2) Producers are primarily autotrophic green plants and are intermediaries between abiotic and biotic components of the biosphere because they manufacture their food through photosynthesis and derive nutrients from the soils through root osmosis. Herbivores and carnivores (consumers) depend for their food on producers.
(3) Consumers are heterotrophic organisms which include animals and man and are further divided into primary consumers (herbivores), secondary consumers (carnivores) and omnivores.
(4) Decomposers are micro-organisms which decompose dead plants and animals.