Here is a compilation of essays on ‘Ecosystem’ for class 6, 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Ecosystem’ especially written for school and college students.
Essay on Ecosystem
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Essay Contents:
- Essay on the Meaning of Ecosystem
- Essay on the Concept of Ecosystem
- Essay on the Functions of an Ecosystem
- Essay on the Components of an Ecosystem
- Essay on the Ecological Pyramid
- Essay on the Productivity of an Ecosystem
- Essay on Energy Flow in an Ecosystem
- Essay on Food Chain and Food Web
- Essay on the Ecological Habitat
1. Essay on the Meaning of Ecosystem:
The term an ecosystem is originally defined by Tansley (1935). An ecosystem is defined as the network of interactions among organisms, and between organisms and their environment they can come in any size but usually encompass specific, limited spaces although according to some scientists the entire planet is an ecosystem or an ecosystem is defined as a complex, dynamic community of organisms including plants, animals and micro-organisms that all interact among themselves as well as with the environment that they live in.
An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment. All living organisms are a part of both a biotic community and an ecosystem.
Ecosystems are what sustain both humans and animals, providing them with energy, nutrients, oxygen, water and shelter, among other things. Ecosystems don’t have strict boundaries or sizes; they can range from something as small as a dead tree stump to something as large as the ocean.
2. Essay on the Concept of Ecosystem:
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There are many examples of ecosystems a pond, a forest, and grassland. The study of ecosystems mainly consists of the study of certain processes that link the living, or biotic, components to the non-living, or abiotic, components. Energy transformations and bio-geochemical cycling are the main processes that comprise the field of ecosystem ecology. Ecology generally is defined as the interactions of organisms with one another and with the environment in which they occur.
Studies of individuals are concerned mostly about physiology, reproduction, development or behavior, and studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction. Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.
These functional aspects include such things as the amount of energy that is produced by photosynthesis, how energy or materials flow along the many steps in a food chain, or what controls the rate of decomposition of materials or the rate at which nutrients are recycled in the system.
3. Essay on the Functions of an Ecosystem:
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Ecosystem function is the capacity of natural processes and components to provide goods and services that fulfill human needs, either directly or indirectly. Ecosystem functions are conceived as a subset of ecological processes and ecosystem structures. Each function is the result of the natural processes of the total ecological subsystem of which it is a part.
Natural processes, in turn, are the result of complex interactions between biotic (living organisms) and abiotic (chemical and physical) components of ecosystems through the universal driving forces of matter and energy.
There are four primary groups of ecosystem functions:
(i) Regulatory functions,
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(ii) Habitat functions,
(iii) Production functions and
(iv) Information functions
(i) Regulatory Functions:
This group of functions relates to the capacity of natural and semi-natural ecosystems to regulate essential ecological processes and life support systems through bio-geochemical cycles and other biospheric processes. In addition to maintaining the ecosystem (and biosphere health), these regulatory functions provide many services that have direct and indirect benefits to humans (i.e., clean air, water and soil, and biological control services).
(ii) Habitat Functions:
Natural ecosystems provide refuge and a reproduction habitat to wild plants and animals and thereby contribute to the (in situ) conservation of biological and genetic diversity and the evolutionary process.
(iii) Production Functions:
Photosynthesis and nutrient uptake by autotrophs converts energy, carbon dioxide, water and nutrients into a wide variety of carbohydrate structures which are then used by secondary producers to create an even larger variety of living biomass.
This broad diversity in carbohydrate structures provides many ecosystem goods for human consumption, ranging from food and raw materials to energy resources and genetic material.
(iv) Information Functions:
Since most of human evolution took place within the context of an undomesticated habitat, natural ecosystems provide an essential ‘reference function’ and contribute to the maintenance of human health by providing opportunities for reflection, spiritual enrichment, cognitive development, recreation and aesthetic experience.
4. Essay on the Components of an Ecosystem:
There are two types of components that make up an ecosystem’s characteristics:
(A) Abiotic and
(B) Biotic.
Biotic components are made up of living factors. Abiotic components are made up of all non-living factors.
Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems is obtained primarily from the sun. It generally enters the system through photosynthesis, a process that also captures carbon from the atmosphere.
(A) Abiotic Components:
These factors are non-living like light, temperature, water, atmospheric gases, wind as well as soil (edaphic) and physiographic (nature of land surface).
Abiotic factors may be abbreviated as SWATS (Soil, Water, Air, Temperature, Sun light):
I. Sunlight:
Sunlight is a major part of abiotic conditions in an ecosystem. The sun is the primary source of energy on our planet. Light energy (sunlight) is the primary source of energy in nearly all ecosystems. It is the energy that is used by green plants (which contain chlorophyll) during the process of photosynthesis; a process during which plants manufacture organic substances by combining inorganic substances.
Visible light is of the greatest importance to plants because it is necessary for photosynthesis. Factors such as quality of light, intensity of light and the length of the light period (day length) play an important part in an ecosystem.
(i) Quality of Light (Wavelength or Colour):
Plants absorb blue and red light during photosynthesis. In terrestrial ecosystems the quality of light does not change much. In aquatic ecosystems, the quality of light can be a limiting factor. Both blue and red light are absorbed and as a result do not penetrate deeply into the water. To compensate for this, some algae have additional pigments which are able to absorb other colours as well.
(ii) Light Intensity:
The intensity of the light that reaches the earth varies according to the latitude and season of the year. The southern hemisphere receives less than 12 hours of sunlight during the period between the 21st March and the 23rd of September, but receives more than 12 hours of sunlight during the following six months.
(iii) Phototropism:
Phototropism is the directional growth of plants in response to light where the direction of the stimulus determines the direction of movement; stems demonstrate positive phototropism i.e. they came towards the light when they grow.
II. Temperature:
The distribution of plants and animals is greatly influenced by extremes in temperature for instance the warm season. The occurrence or non-occurrence of frost is a particularly important determinant of plant distribution since many plants cannot prevent their tissues from freezing or survive the freezing and thawing processes.
Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Temperature also affect decomposition freezing temperatures kill a soil microorganism, which allows leaching to play a more important role in moving nutrients around.
Temperature also plays a key role in ecosystems with hot climates allowing rapid growth, high surface animals, and cold climates leading to more spherical, fatty animals as well as slower growth and reproduction. Habitats vary widely as a result of temperature too. Plants and bacteria also have to have particular features that allow for survival in extreme climates of temperatures.
III. Water:
In aquatic eco systems water perform many important environmental functions Water availability is an abiotic factor of ecosystems. Living things need water to survive and how plentiful or scarce water is affects the necessary water cycle of evaporation, condensation and precipitation. Oceans, rivers or streams are key components of an ecosystem and the many forms of life that live there.
The freshwater ecosystem itself is made up of biotic and abiotic elements and depends on them equally as well. Water quality is another factor, with important metabolic functions subject to water ingredients like zinc and iron that become poisonous with low- quality water.
IV. Weather:
Meteorology or weather conditions considered abiotic component are temperature, wind velocity, solar insulation, humidity and precipitation. The most important of these is climate. Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available.
The statistical and seasonal variation of these factors influences the habitat. Weather directly controls the biotic component i.e. Vegetation as well as animals. Climate features such as rain, wind and temperature play a large part also in the way an ecosystem has to work. Rain provides necessary water for photosynthesis and so its quantity will determine just how many photosynthetic organisms can survive in an environment, the predators of those organisms, as well as the types.
V. Soil:
Soil conditions that affect ecosystems are the granularity, chemistry and nutrient content and availability. These soil conditions interact with precipitation to cause change. Although animal remains dead organic material such as are considered abiotic.
VI. Air:
Air levels define how strong and sturdy the organisms in an ecosystem are, and which habitats must be in existence for them to survive. Low wind levels allow for weaker more feeble organisms that reproduce rapidly to survive. In windy areas, many plants use it as an advantage and make countless spores that will be carried to other plants and pollinate.
Air quality plays an important part because pollution can contribute to carbon monoxide and sulfur dioxide degrading circulatory or pulmonary function. Air pollution can also disrupt the process of photosynthesis.
VII. Topography:
Topography also controls ecosystem processes by affecting things like micro-climate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside Micro-topographic elements mix with meteorology barriers to affect plant growth and selection in a given area.
Topography, soil type and precipitation shape surface run-off and limit the ability of animals to build burrows and nests and affects the way predators and prey are able to hunt and hide from each other.
(i) Altitude:
This has effects on climate and so has various effects according to what climate factors it affects.
(ii) Slope:
The organisms on a flat land compared to a hilly one will have different movement muscles to one another. This is because some muscles are say, evolved for forward propulsion (calf muscles) whilst others for lifting the leg (thigh muscles).
(iii) Aspect:
This is the direction that the land is facing (in relation to the sun) and so has its relevance to temperature, wherein for example, an environment that faces generally away from the sun will be cooler.
VIII. Tolerance Range:
Abiotic factors are particularly important to new or barren or unpopulated ecosystems. This is because the abiotic factors of the unpopulated system sets the stage for how well a given species will be able to live, thrive and reproduce there. Each organism’s ability to survive in a set of abiotic conditions is known as the tolerance range.
(B) Biotic Components:
Biotic components mean related to life. These are living factors. Plants, animals’, insects, fungi and bacteria are all biotic or living factors. Each biotic factor needs energy to do work and food for proper growth.
There are three types of organisms that live in a biotic community are producers, consumers and decomposers. The members of a biotic community are inter-dependent in that they all depend on one another in some way for their survival. This inter-dependence is essential for stability of biotic community.
They can be further sub-divided into autotrophs (producers) and heterotrophs (consumers) that include herbivores, carnivores, and omnivores, detritivores (decomposers).The biotic characteristics are mainly determined by the organisms that occur. For example, wetland plants may produce dense canopies that cover large areas of sediment or geese may graze the vegetation leaving large mud flats.
Aquatic environments have relatively low oxygen levels, forcing adaptation by the organisms found there. For example, many wetland plants must produce aerenchyma to carry oxygen to roots.
Other biotic characteristics are more subtle and difficult to measure, such as the relative importance of competition, mutualism or predation. There are a growing number of cases where predation by coastal herbivores including snails, geese and mammals appears to be a dominant biotic factor.
(i) Autotrophic Organisms:
Autotrophic organisms are producers i.e. autotrophs. They convert the solar energy into food from photosynthesis (the transfer of sunlight, water, and carbon dioxide into energy).They generate organic compounds from inorganic material. Algae use solar energy to generate biomass from carbon dioxide and are possibly the most important autotrophic organisms in aquatic environments.
Of course, the more shallow the water, the greater the biomass contribution from rooted and floating vascular plants. These two sources combine to produce the extraordinary production of estuaries and wetlands, as this autotrophic, biomass are converted into fish, birds, amphibians and other aquatic species.
Chemosynthetic bacteria are also referred as autotrophs. They found in benthic marine ecosystems. These organisms are able to feed on hydrogen sulphide in water. Height concentrations of animals that feed on these bacteria are found around volcanic vents.
(ii) Heterotrophic Organisms:
Heterotrophic organisms consume autotrophic organisms and use the organic compounds in their bodies as energy sources and as raw materials to create their own biomass. Heterotrophs are further divided into herbivore, carnivore, omnivore and decomposer on the basis of source of nutrition.
Herbivores are also named as primary consumers. Caterpillars, rabbit, grasshopper etc. are plant eater. They withdraw their nutrition from green plants. Energy transferred from plants have occurred.
Carnivores are named as secondary consumer. Consumers, i.e. heterotrophs: e.g. animals, they depend upon producers (occasionally other consumers) for food. Animals that feed on primary consumers are (carnivores) secondary consumers. Blackbird, frogs, Meat eaters, feed upon the herbivores, fewer in number than primary consumers. Their energy transfers have occurred, more chance for energy to be lost via respiration, excretion etc.
Omnivores are named as tertiary consumer or deversivores hawks, fox, dog, humans etc. are omnivores. Animals that feed on secondary consumers are omnivores ortretiary consumers. They have two sources of food, because eat both plants and animals.
Decomposers, i.e. detritivores: e.g. fungi and bacteria, they break down chemicals from producers and consumers usually after death into simpler form .They convert macro molecules into micro molecules by enzymatic activity.
Each of these (Producer, Primary consumer, Secondary consumer, Tertiary consumer and Decomposer) constitutes a trophic level. The sequence of consumption of nutrition from plant to herbivore, herbivore to carnivore in the forms a food is called chain. Real systems are much more complex than these organisms will generally feed on more than one form of food, and may feed at more than one trophic level.
Carnivores may capture some prey which is part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Euryhaline organisms are salt tolerant and can survive in marine ecosystems, while stenohaline or salt intolerant species can only live in freshwater environments.
5. Essay on the Ecological Pyramid:
The descriptive device used to explore the trophic structure of an ecosystem is called a trophic pyramid. The purpose of a trophic pyramid is to graphically represent the distribution of biomass or energy among the different trophic levels of the ecosystem. An ecological pyramid (also trophic pyramid) is a graphical representation designed to show the number of organisms, biomass or biomass productivity and energy transferred at each trophic level in a given ecosystem.
Charles Elton developed the concept of ecological pyramid. After his name these pyramids are also called as Eltonian pyramids. Ecological pyramids begin with producers on the bottom (such as plants) and proceed through the various trophic levels (such as herbivores that eat plants, then carnivores that eat herbivores, then carnivores that eat those carnivores, and so on). The highest level is the top of the food chain.
a. Pyramid of Biomass:
Biomass is the amount of living or organic matter present in an organism. Biomass pyramids show how much biomass is present in the organisms at each trophic level, while productivity pyramids show the production or turnover in biomass. The total amount of living or organic matter in an ecosystem at any time is called ‘Biomass’.
An ecological pyramid of biomass shows the relationship between biomass and trophic level by quantifying the amount of biomass present at each trophic level of an ecological community at a particular moment in time.
“Pyramid of biomass is the graphic representation of biomass (total amount of living or organic/ dry matter in an ecosystem) present per unit area of different trophic levels, with producers at the base and top carnivores at the tip”. Typical units for a biomass pyramid could be grams per meter, or calories per meter. The pyramid of biomass may be ‘inverted’ or upright.
b. Inverted Pyramid:
When smaller weight of producers supports larger weight of consumers an inverted pyramid of biomass is formed. In an aquatic habitat the pyramid of biomass is inverted or spindle shaped where the biomass of trophic level depends upon the reproductive potential and longevity of the member.
In a pond ecosystem, the phytoplanktons are the major producers, at any given point. This phytoplankton will be lower than the mass of the heterotrophs, such as fish and insects. This is explained as the phytoplanktons reproduce very quickly, but have much shorter individual lives.
c. Upright Pyramid:
When larger weight/biomass of producers support the smaller weight of consumers (primary, secondary and onwards) an upright pyramid of biomass is resulted. In forest or terrestrial ecosystem plants or producer have maximum dry weight while primary consumer depends upon them have low dry weight as compared to them. Secondary and tertiary consumer also show loss in dry weight successively. Thus, the pyramid of biomass in a terrestrial ecosystem is upright.
d. Pyramid of Number:
Ecosystem community may be represented in terms of number of organism. When the relationships among the number of producers, primary consumers (herbivores), secondary consumers (carnivore of order 1), tertiary consumers (carnivore of order 2) and so on in any ecosystem, it forms a pyramidal structure called the pyramid of number. “Pyramid of numbers is the graphic representation of number of individuals per unit area of various trophic levels stepwise with producers forming the base and top carnivores the tip”. The shape of this pyramid varies from ecosystem to ecosystem.
There are three types of pyramid of numbers:
e. Upright Pyramid:
In aquatic and grassland ecosystem numerous small autotrophs support lesser herbivores which support further smaller number of carnivores and hence the pyramidal structure is upright.
In forest ecosystem lesser number of producers support greater number of herbivores who in turn support a fewer number of carnivores. Thus number or organism producer to herbivore increase, while herbivore to carnivore and carnivore to successive trophic level number of organism decrease.
f. Inverted Pyramid:
In parasitic food chain, one primary producer support numerous parasites which support still more hyper parasites therefore number of organism at each trophic level increase. In a parasitic food chain, for e.g., an oak tree, the large tree provides food to several herbivorous birds. The birds support still larger population of ectoparasites leading to the formation of an inverted pyramid.
g. Pyramid of Energy:
The pyramid of numbers and pyramid of biomass have their limitations because they provide information only on the quantity of organic matter available at a particular time but not on the productivity and turnover time.
The pyramid of energy is drawn after taking into consideration the total quantity of energy utilized by the trophic levels in an ecosystem over a period of time. As the quantity of energy available for utilization in successive trophic levels is always less because there is loss of energy in each transfer, the energy pyramid will always be upright.
“Pyramid of energy is a graphic representation of the amount of energy trapped per unit time and area in different trophic level of a food chain with producers forming the base and the top carnivores at the tip”.
Pyramid of energy is always upright. It is so because at each transfer about 80 – 90% of the energy available at lower trophic level is used up to overcome its entropy and to perform metabolic activities. Only 10% of the energy is available to next trophic level (as per Lindemann’s ten percent rule).
When a large tree support larger number of herbivorous birds which in turn are eaten by carnivorous birds like falcon and eagle, which are smaller in number, it forms a spindle shaped pyramid.
6. Essay on the Productivity of an Ecosystem:
In ecology, productivity or production is refers to the rate of synthesis or production of biomass in an ecosystem. It is usually expressed in units of mass per unit surface (or volume) per unit time, for instance grams per square meter per day (g m2 d1).
The mass unit may relate to dry matter or to the mass of carbon generated. Productivity of autotrophs such as plants is called primary productivity, while that of heterotrophs such as animals is called secondary productivity.
A. Primary Production:
Primary production is the synthesis of new organic material from inorganic molecules such as H2O and CO2. It is dominated by the process of photosynthesis which uses sunlight to synthesise organic molecules such as sugars, although chemosynthesis represents a small fraction of primary production.
Organisms responsible for primary production include land plants, marine algae and some bacteria (including cyanobacteria).The controlling factors of primary productivity are intensity of light, temperature, moisture, air and nutrients.
Ecosystem Productivity:
Tropical regions every day and temperate regions during the growing season receive some 8,000 to 10,000 kilocalories (kcal) of energy each day on each square meter (1 m2) of surface. A kilocalorie is the amount of heat needed to warm 1 kg of water 1 degree Celsius (°C). Because all of the light trapped in photosynthesis is ultimately released as heat, it makes sense to follow the flow of energy through ecosystems in units of heat.
Primary production is the production of organic matter from inorganic carbon sources. Overwhelmingly, this occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels.
It also drives the carbon cycle, which influences global climate via the greenhouse effect. The process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).
About 48-60% of the GPP is consumed in plant respiration. The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP). Total photosynthesis is limited by a range of environmental factors.
These include the amount of light available, the amount of leaf area a plant has to capture light (shading by other plants is a major limitation of photosynthesis), rate at which carbon dioxide can be supplied to the chloroplasts to support photosynthesis, the availability of water, and the availability of suitable temperatures for carrying out photosynthesis.
(a) Gross Productivity:
Gross productivity is the amount of energy trapped in organic matter during a specified interval at a given trophic level. The table shows the use of visible sunlight is a cattail marsh. The plants have trapped only 2.2% of the energy falling on them.
However, at least half of this (2.2%) is lost by cellular respiration as the plants run their own metabolism.
(b) Net Productivity:
Net productivity is the amount of energy trapped in organic matter during a specified interval at a given trophic level less that lost by the respiration of the organisms at that level.
The table shows representative values for the net productivity of a variety of ecosystems both natural and managed. These values are only representation and are show fluctuations because of variations in temperature, fertility, and availability of water.
The productivity of an ecosystem is defined as the rate at which radiant energy (solar energy) is stored by photosynthetic and chemosynthetic activity of green plants (autotrophs) in the form of organic substances which can be used as food materials. In other words, the productivity of an ecosystem refers to the rate of production i.e. the amount of organic matter accumulated in any unit time.
This Primary productivity is of two types:
1. Gross Primary Productivity:
Gross primary productivity is the total rate of photosynthesis including the living matter used up.
2. Net Primary Productivity:
Net primary productivity is the rate of storage of organic materials in plant bodies in excess of respiratory utilization by plants. In other words, the net photosynthesis for an entire community is its net primary productivity.
This is the amount of stored chemical energy (biomass) that the communities synthesize for the ecosystem. Biomass is the net dry weight of organic material; it is biomass that feeds the food chain.
B. Secondary Production:
Secondary production is the generation of biomass of heterotrophic (consumer) organisms in a system. This is driven by the transfer of organic material between trophic levels, and represents the quantity of new tissue created through the use of assimilated food.
Secondary production is sometimes defined to only include consumption of primary producers by herbivorous consumers. (With tertiary production referring to carnivorous consumers), but is more commonly defined to include all biomass generation by heterotrophs. Organisms responsible for secondary production include animals, protists, fungi and many bacteria.
Secondary production can be estimated through a number of different methods including increment summation, removal summation, the instantaneous growth method and the Allen curve method. Secondary productivity is the rate of energy storage at consumer level.
C. Net Productivity:
Means the rate of storage of organic matter not used by any consumer. Such organic matters are not consumed by any consumer it is utilized by decomposer. The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition.
This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem and nutrients and atmospheric carbon dioxide would be depleted. Approximately 90% of terrestrial NPP goes directly from plant to decomposer.
Decomposition processes can be separated into three categories leaching, fragmentation and chemical alteration of dead material. As water moves through dead organic matter, it dissolves and carries with it the water-soluble components.
These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered “lost” to it). Newly shed leaves and newly dead animals have high concentrations of water- soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.
Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton.
Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition. Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.
The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows to them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.
Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of the physical factors environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.
Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. This can be especially important as the soil thaws in die spring, creating a pulse of nutrients which become available.
According to Odum, there are three main levels of productivity on the earth’s surface:
(1) Regions of die highest fertility and productivity, which comprise shallow water areas, moist forest, alluvial plains and fertile cropped lands.
(2) Grasslands, shallow lakes and most agricultural lands.
(3) Areas of lowest productivity such as arctic lands, deserts and ocean deeps.
Pyramid of Productivity:
An ecological pyramid of productivity is often more useful, it show the production or turnover of biomass at each trophic level. Instead of showing a single snapshot in time, productivity pyramids show the flow of energy through the big-food chain. Typical units would be grams per meter per year or calories per meter per year. This graph begins with producers at the bottom and places higher trophic levels on top.
When an ecosystem is healthy, this graph produces a standard ecological pyramid. This is because in order for the ecosystem to sustain itself there must be more energy at lower trophic levels than there is at higher trophic levels.
This allows for organisms on the lower levels to not only maintain a stable population, but to also transfer energy up the pyramid. The exception to this generalization is when portions of a food web are supported by inputs of resources from outside of the local community.
When energy is transferred to the next trophic level, typically only 10% of it is used to build new biomass, becoming stored energy and most of them used in metabolic processes. As such, in a pyramid of productivity each step will be 10% the size of the previous step (100, 10, 1, 0.1, and 0.01).
The advantages of the pyramid of productivity are:
(i) It takes account of the rate of production over a period of time.
(ii) Two species of comparable biomass may have very different life spans.
Therefore their relative biomass is misleading, but their productivity is directly comparable.
An ecological pyramid of numbers shows graphically the population of each level in a food chain.
7. Essay on Energy Flow in an Ecosystem:
In an ecosystem Biotic components are connected to each other, Producer synthesize organic matter after using sun light, these organic matter also fulfill nutritional requirement of all types of consumer. Energy enters the biological system as light energy, or photons, is transformed into chemical energy in organic molecules by cellular processes including photosynthesis and respiration, and ultimately is converted to heat energy. This energy is dissipated, meaning it is lost to the system as heat; once it is lost it cannot be recycled.
Without the continued input of solar energy, biological systems would quickly shut down. Thus the earth is an open system with respect to energy. The organic matter transferred from producer to consumer in the form of food. Food is the source of energy and energy in the form of food transferred from producer to consumer. Such transfer is named as energy flow.
The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. The transformations of energy in an ecosystem begin first with the input of energy from the sun.
Energy from the sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen (derived from the splitting of water molecules) to produce carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine triphosphate or ATP. In terrestrial ecosystems, roughly 90% of the NPP ends up being broken down by decomposers.
The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system. In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher. In trophic systems photosynthetic organisms are the primary producers.
The organisms that consume their tissues are called primary consumers or secondary producers’ herbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumers carnivores are secondary consumers.
Each of these constitutes a trophic level. The sequences of consumption of energy are from plant to herbivore, herbivore to carnivore that forms a food chain. Carnivores may capture some preys which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus).
The frog represents a node in an extended food web. The energy ingested is utilized for metabolic processes and transformed into biomass. This energy flow diagram illustrates that energy is lost as it fuels the metabolic process that transforms the energy and nutrients into biomass.
An expanded three link energy food chain (1. plants, 2. herbivores, 3. carnivores) illustrating the relationship between food flow diagrams and energy transformity. The transformity of energy becomes degraded, dispersed, and diminished from higher quality to lesser quantity as the energy within a food chain flows from one trophic species into another.
It is so because at each transfer about 80 – 90% of the energy available at lower trophic level is used up to overcome its entropy and to perform metabolic activities. Only 10% of the energy is available to next trophic level (as per Lindemann’s ten percent rule).
Abbreviations: I = input, A=assimilation, R = respiration, NU = not utilized, P = production, B = biomass.
8. Essay on Food Chain and Food Web:
Food chains were first introduced by the African-Arab scientist and philosopher Al-Jahiz in the 9th century and later popularized in a book published in 1927 by Charles Elton, which also introduced the food web concept. A food chain is a linear sequence of links in a food web starting from a species that eats other species. A food chain shows you which animal eats which in a simple line. Most food chains have no more than four or five links.
There cannot be too many links in a single food chain because the animals at the end of the chain would not get enough food (and hence energy) to stay alive. Most animals are part of more than one food chain and eat more than one kind of food in order to meet their food and energy requirements.
These interconnected food chains form a food web. In a food chain, energy is passed from one link to another. When herbivore eats, only a fraction of the energy (that it gets from the plant food) becomes new body mass- the rest of the energy is lost as waste or used up by the herbivore to carry out its life processes.
Therefore, when the herbivore is eaten by a carnivore, it passes only a small amount of total energy (that it has received) to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be “wasted” or “used up” by the carnivore. The carnivore then has to eat many herbivores to get enough energy to grow.
A food chain differs from a food web, because the complex polyphagous network of feeding relations are aggregated into trophic species and the chain, only follows linear monophagous pathways. A common metric used to quantify food web trophic structure is food chain length.
In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web and the mean chain length of an entire web is the arithmetic average of the lengths of all chains in a food web.
Food chains are directional paths of trophic energy or, equivalently, sequences of links that start with basal species, such as producers or fine organic matter and ends with consumer organisms.
The food chain length is a continuous variable that provides a measure of the passage of energy and an index of ecological structure that increases in value counting progressively through the linkages in a linear fashion from the lowest to the highest trophic (feeding) levels. Food chains are often used in ecological modeling.
Food chain varies in length from three to six or more levels. Ex:
1. A food chain consisting of a flower, a frog, a snake and an owl consists of four levels;
2. A food chain consisting of grass, a grasshopper, a rat, a snake and finally a hawk consists of five levels.
Producers, such as plants, are organisms that utilize solar energy or heat energy to synthesize starch. All food chains start with a producer. Consumers are organisms that eat other organisms. All organisms in a food chain, except the first organism, are consumers.
9. Essay on the Ecological Habitat:
Habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant, or other type of organism. It is the natural environment in which an organism lives, or the physical environment that surrounds (influences and is utilized by) a species population.
An area of land or water occupied by an organism, a group of a single species, a biocenosis, or a synousia and possessing all conditions required for its existence (climate, topography, soil, food).The habitat of a species is defined as the total area within the species’ range of distribution that satisfies the species’ ecological requirements. The habitat of a population is the part of the species’ habitat that will guarantee the existence of a population.
The habitat of an individual is the actual area occupied by a given individual in all phases of its development. The habitats of many species vary with the stage of development in the organism’s life cycle. The part of the habitat for a species occupies for a limited time only (a season, a part of a day) or for a particular purpose (feeding, reproduction) is called a station. The habitat of a biocenosis is called a biotope.
(i) Microhabitat:
The term microhabitat is often used to describe small-scale physical requirements of a particular organism or population.
(ii) Monotypic Habitat:
The monotypic habitat occurs in botanical and zoological contexts, and is a component of conservation biology. In restoration ecology of native plant communities or habitats, some invasive species create monotypic stands that replace and/or prevent other species, especially indigenous ones, from growing there.
A dominant colonization can occur from retardant chemicals exuded, nutrient monopolization, or from lack of natural controls such as herbivores or climate, that keep them in balance with their native habitats.
(iii) Ecological Niche:
The word literally means a specific place however the ecologist use it for the habitat along with the role a species or population plays in its ecosystem.
“Ecological niche means the total interaction of a species with in the environment or its functional position or status in an ecosystem.”
In ecology, a niche is a term describing the way of life of a species. Each species is thought to have a separate, unique niche. The ecological niche describes how an organism or population responds to the distribution of resources and competitors (e.g., by growing when resources are abundant, and when predators, parasites and pathogens are scarce) and how it in turn alters those same factors (e.g., limiting access to resources by other organisms, acting as a food source for predators and a consumer of prey).
The majority of species exist in a standard ecological niche. A premier example of a non-standard niche filling species is the flightless, ground-dwelling kiwi bird of New Zealand, which exists on worms, and other ground creatures, and lives its life in a mammal niche. Island biogeography can help explain island species and associated unfilled niches.
(iv) Grinnellian Niche:
The word “niche” is derived from the Middle French word nicher, meaning to nest. The term was coined by the naturalist Joseph Grinnell in 1917, in his paper “The niche relationships of the California Thrasher.” The Grinnellian niche concept embodies the idea that the niche of a species is determined by the habitat in which it lives. In other words, the niche is the sum of the habitat requirements that allow a species to persist and produce offspring.