Our Environment

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Introduction

• All organisms including plants, animals, microorganisms, human beings and the physical environment all interact to maintain a balance in the environment.

• All the living and non- living species and their interaction constitutes an environment.

• A biological community of interacting organisms and their physical environment.

• Biotic organism include :
  Every living organism such as a living bacterium till human beings.

• Abiotic components include :
  Temperature
  Rainfall
  Wind
  soil
  Minerals

• Made-made ecosystems are :
  Gardens
  Crop Fields

• Natural ecosystems are :
  Forests
  Ponds
  lakes etc.

Crop Field (Man-Made)

Forest (Natural)

• Organisms are divided into three main categories , they are:
  Producers
  Consumers
  Decomposers

• Organisms which can produce their own food in the presence of sunlight and chlorophyll under the process of photosynthesis are known to be producers / autotrophs. Eg: green plants and cyanobacteria.

• Organisms, who depend or drive food from other organisms or producers directly or indirectly are known to be consumers.

• Consumers are classified into :
  Herbivores
  Carnivores
  Omnivores
  Parasites

• Micro-organisms that can break down the complex organic substances into simpler inorganic substances that further go down the lower layers of soil and utilized by plants are considered as decomposers. Eg :  bacteria and fungi.

Food Chains & Food Webs

• The sun is the ultimate source of energy on this earth.

• A food chain refers to the order of events in an ecosystem, where one living organism eats another organism, and later that organism is consumed by another larger organism. The flow of nutrients and energy from one organism to another at different trophic levels forms a food chain.

• Trophic level refers to the sequential stages in a food chain, starting with producers at the bottom, followed by primary, secondary and tertiary consumers.

Details On Food Chain

1. Each step or level of the food chain forms a tropic level.
2. The autotrophs or the producers are at the first trophic level.
3. They fix up the solar energy and make it available for heterotrophs or the consumers.
4. The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third and larger carnivores or the tertiary consumers form the fourth trophic level.
5. Food we eat acts as a fuel to provide us energy to do work.
6. The autotrophs capture the energy present in sunlight and convert it into chemical energy. This energy supports all the activities of the living world. From autotrophs, the energy goes to the heterotrophs and decomposers.
7. The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves and convert it into food energy.
8. According to Lindeman’s Law of 10%, the efficiency of energy transfer from one trophic level to the next is about 10%. Or Only 10% of the net primary productivity of producers ends up as herbivores and so on to the next trophic levels.
9. Therefore, 10% can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers. n Since so little energy is available for the next level of consumers, food chains generally consist of only three or four steps. The loss of energy at each step is so great that very little usable energy remains after four trophic levels. n There are generally a greater number of individuals at the lower trophic levels of an ecosystem, the greatest number is of the producers.

Food Web 

1. A system of interlocking and interdependent food chains.
2. It can be described as a “who eats whom” diagram that shows the complex feeding relationships for a particular ecosystem.
3. The interconnectedness of how organisms are involved in energy transfer within an ecosystem is vital to understanding food webs and how they apply to real-world science.

Representation Of Lindeman’s Law

Figure representing : A food web

Details On Food Chains

1. The flow of energy is unidirectional.
2. The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs.
3. Another interesting aspect of food chain is how unknowingly some harmful chemicals enter our bodies through the food chain.
4. One of the reasons is the use of several pesticides and other chemicals to protect our crops from diseases and pests. These chemicals are either washed down into the soil or into the water bodies. From the soil, these are absorbed by the plants along with water and minerals, and from the water bodies these are taken up by aquatic plants.
5. As these chemicals are not degradable, these get accumulated progressively at each trophic level. As human beings occupy the top level in any food chain, the maximum concentration of these chemicals get accumulated in our bodies. This phenomenon is known as biological magnification.

Flow Of Energy In Environment

Ozone Layer And Its Depletion

• Ozone is a deadly poison.
• At stratosphere layer, it shields the earth’s surface from the harmful UV rays from the sun.
• Ultraviolet rays can cause skin cancers and can damage our cells or induce mutations also can affect the cornea of the eyes.

• Reactions involving formation of ozone:

1. The high energy of UV rays splits up the oxygen molecule and release a nascent oxygen [O].
2. Then this nascent oxygen combines with the oxygen molecule to give ozone (comprising 3 atoms of oxygen).

• The amount of ozone in the atmosphere began to drop sharply in the 1980s. This decrease has been linked to synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.
• In 1987, the United Nations Environment Program (UNEP) succeeded in forging an agreement to freeze CFC production.

Degradable & Non-Biodegradable Wastes 

Biodegradable wastes	Non – biodegradable wastes
Biodegradable waste is a form of waste, originating naturally from plant or animal sources, which may be degraded by other living organisms.	Waste that cannot be decomposed or degraded by the biological process is known as “Non-biodegradable wastes”. Most of them include the inorganic waste that is non-biodegradable.
Biodegradable substances may decompose within few days or months.	Non-biodegradable items may take thousands of years or may never ever be broken down and remain in their original form as it is.

SUMMARY

• The various components of an ecosystem are interdependent.
• The producers make the energy from sunlight available to the rest of the ecosystem.
• There is a loss of energy as we go from one trophic level to the next, this limits the number of trophic levels in a food-chain.
• Human activities have an impact on the environment.
• The use of chemicals like CFCs has endangered the ozone layer. Since the ozone layer protects against the ultraviolet radiation from the Sun, this could damage the environment.
• The waste we generate may be biodegradable or non-biodegradable.
• The disposal of the waste we generate is causing serious environmental problems.