Our Environment

Ecosystem is defined as the structural and functional unit of biosphere. It is a stable ecological unit where continuous input of energy and circulation of matter occurs.

Ecosystem is the structural and functional unit of biosphere and is a stable ecological unit where regular input of energy and circulation matter takes place.

Autotrophs can make their own food in the presence of sunlight. They are the ultimate source of energy for each and every organism of a food chain. Hence, every chain always starts with producers (autotrophs) that is why they are placed at the first trophic level of food chain.

In given food chain, Grass –> Insects –> Frogs à Snakes

Frogs assign at third trophic level. They act as secondary consumers who feeds of primary consumers (i.e., insects)

Organisms that feed on dead plants and animals are called decomposers, e.g. bacteria, fungi, etc. They breakdown the complex organic compounds present in the dead remains into simpler substances and obtain nutrition from them. These substances are released into the soil and to the atmosphere.

Thus, they play the following roles

(i) They help in recycling of materials, replenishment of the soil’s nutrients, etc.

(ii) They clean our surroundings by decomposing dead organisms and organic wastes.

Natural water bodies are example of natural ecosystem. They exist naturally without any human support, whereas aquarium is an artificial ecosystem which is created and maintained by humans. It rely on human efforts to sustain. It does not possess a self-regulating mechanism.

Ans. The study of food chain in an area or habitat helps in

(i) understanding the energy transfer through organisms.

(ii) understanding the ecological balance in a habitat or ecosystem.

(iii) understanding harmful human activities and disruption of ecological balance, if any

An example of four steps of food chain operating in a large lake is as follow:

Algae à Protozoan à Small fish à Big fish.

Parasites are organisms (animals or plants) that live in or on other organisms (host) and take benefits by deriving nutrients from it, i.e., they get food or protection from host organisms, e.g. Cuscuta.

On other hand, decomposers are organisms that breakdown dead or decaying organisms into simple inorganic substances. E.g., Fungi

The transfer of food or energy takes place through various levels in the food chain, which are known as trophic levels. E.g.

In a food chain, about 80—90% of the energy available at a trophic level is lost during its transfer to next trophic level. Hence, amount of energy available goes on decreasing at each successive trophic level.

If a plant fixes 4000 J energy, then next three successive trophic levels will get 400 J, 40 J and 4 J respectively (according to 10% law). If another level is added in a food chain, then it will get only 0.4 J energy. Thus, usually food chains remain shorter and limited to 3-4 trophic levels only.

If we kill all the organisms in one trophic level, the lower trophic level will grow more in number and the higher trophic level will not survive.

Hence, flow of energy from one trophic level to other will not take place.

According to 10% law, only 10% of the energy entering a particular trophic level of organisms is available for transfer to the next trophic level.

The flow of energy through a food chain is unidirectional and it moves progressively through various trophic levels as follow

(i) Green plants capture 1% of energy of the sunlight that falls on their leaves and convert it into food energy.

(ii) When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment. On an average only 10% of food eaten is turned into its own body and made available for the next level of consumers.

(iii) Thus, 10% can be taken as average value of the amount of organic matter present at each step and reaches the next level of consumers.

Ans. The flow of energy in an ecosystem occurs in the following sequence

The flow of energy is unidirectional because of the reasons given below

(i) Energy flows progressively from one trophic level to another and cannot revert back. Energy given out as heat is lost to the environment and does not return to be used again.

(ii) The available energy decreases at higher trophic level. Out of the total energy available at a particular trophic level, only 10% is passed on to the next trophic level, making it impossible for energy to flow in the reverse direction.

Biological magnification also known as bio magnification is the phenomenon of progressive increase in the concentration of non-biodegradable toxicants in organisms at each successive trophic level.

Biological magnification refers to the increase in the concentration of certain toxicants at each successive trophic level.

No, the levels of magnification will not be same in all trophic levels. When the chemical do not get degraded and get accumulated progressively at each trophic level, it leads to biomagnification. Biomagnification is more in organisms of higher trophic levels.

Depletion of ozone is mainly caused due to the excessive use of Chlorofluorocarbons (CFCs). These are synthetic chemicals which are used as refrigerants and in fire extinguishers.

Steps which should be taken to limit the damage to ozone layer include

(a) Minimising the use of aerosol spray propellants containing fluorocarbons and chlorofluorocarbons.

(b) Exercising control over large scale nuclear explosions and limited use of supersonic planes.

Ozone layer filter the Sun’s ultraviolet radiation (UV-B), thereby protecting the environment from its harmful effects and also play key role in regulating the temperature.

The energy and biomass decrease from lower to higher trophic levels, so the length of food chain is restricted and cannot have more than four trophic levels.

UV radiation acts on the O₂ molecule. Higher energy of UV split apart O₂.

CFCs rise up in stratosphere where UV radiation splits them releasing molecular chlorine (Cl^–). It reacts with O₃ and releases oxygen, so O₃ gets depleted.

Ozone at the higher levels of the atmosphere is a product of UV radiations acting on oxygen (O₂) molecule. The high energy UV radiations split apart some molecular (O₂) into free oxygen (O) atoms. These atoms are very reactive and combine with molecular oxygen to form ozone

It shields the surface of the Earth from harmful ultraviolet (UV) radiations of the Sun.

Due to environmental pollution, ozone layer has began to deplete in the 1980s.

This was mainly due to the increasing use of synthetic chemicals like Chlorofluorocarbons (CFCs). These are used in refrigerants as coolant and in fire extinguishers.

Due to depletion of ozone layer harmful UV rays can penetrate or enter our atmosphere. These radiations are highly damaging to organisms. They can cause skin cancer in human beings, damage eyes (cause disease called cataract), decrease crop yield, disturb global rainfall, etc.

Following methods could be applied to reduce the accumulation of pesticides in our body.

(i) Minimise the use of pesticides.

(ii) Consuming washed fruits and vegetables.

(iii) Developing vegetarian feeding habits

(i.e., feed upon plants as plants belong to lower trophic level so, they have less accumulation of insecticides, whereas organisms of higher trophic level have higher concentration of insecticides and pesticides).

We can reduce the problem of waste disposal by the following methods

– Recycling: The solid wastes such as paper, plastics, glass and metals, etc are recyclable. So, waste paper can be sent to paper mills for reprocessing to form newspaper. The plastic articles can be melted and remoulded again to make new articles.

– Biodegradable waste: The waste such as leftover food, fruits, animal dung, peels of vegetables can be converted into compost by burying them in a pit dug in ground and can be used as manure.

If all the waste is biodegradable, then there will be no accumulation of waste on the Earth and it would be a cleaner place to live.

But if, this biodegradable waste is too large in amount then its slow degradation may lead to air pollution (due to release of gases) as well as water and land pollution.

The two ways in which non-biodegradable substances would affect the environment are

(i) They make the environment poisonous and unfit for survival of living forms of life.

(ii) They block the transfer of energy and minerals in the ecosystem.

Biodegradable materials are broken down by microorganisms present in nature into simple harmless substances.

Non-biodegradable materials need a different treatment like heat and temperature for disposal and hence, both should be discarded in two different dustbins.

Effective segregation of waste as biodegradable and non-biodegradable is much easier to recycle. Biodegradable waste used to make manure can out of compost, whereas non-biodegradable waste could be recycled and reused for various purposes. Also effective segregation of wastes means that less wastes goes to landfill, which makes it cheaper and better for people and environment.

A pond ecosystem refers to freshwater ecosystem where there are various organism’s dependent on each other with the prevailing water environment for their nutrients and survival.

There are two components of the pond ecosystem

(i) Abiotic: It includes water, dissolved minerals, oxygen and carbon dioxide. Sunlight is the main source of energy.

(ii) Biotic: It consists of phytoplankton’s, zooplanktons, aquatic insects, fishes and other aquatic animals. These organisms are classified as producers, consumers and decomposers

The waste generated in our house and measures for its disposal are given in the table below

Insecticides are non-biodegradable chemicals added to crop fields to stop the growth of insects the crops.

Modern insecticides are being developed keeping in mind, the harm they cause to the environment and its components.

Biodegradable insecticides can be decomposed into harmless substances, which will subsequently be dispersed in their specific pathways and cause no pollution.

Non-biodegradable insecticides build up in the fat tissues of the body and pass on to organisms that feed on them.

Hence, they accumulate along the food chain resulting in significant amounts in the tissues of consumers at the highest trophic level.

The property of newly developed insecticides includes that it can easily get decomposed into simpler components by soil bacteria.

Ans. As Mona follows vegetarian diet along with milk products. She should be considered as occupying third trophic level because the curd is prepared by the milk of cow/buffalo by the action of bacteria, but the energy of the milk is getting transferred from cow to Mona, so Mona is at the third trophic level.

Ans. Organisms which breakdown the complex organic compounds present in dead and decaying matter into simpler inorganic materials are called decomposers, e.g. certain bacteria and fungi.

Decomposers act as cleaning agents of environment by decomposing dead bodies of plants and animals. They also help in recycling of materials, replenishment of soil’s nutrients, etc.

The consequence of their absence in an ecosystem can be disastrous. The dead bodies would persist for long, leading to their accumulation and thus, polluting the environment. The biogenetic nutrients associated with these remains will not be returned back to the environment.

As a result, all the nutrients present in soil, air and water would soon be exhausted and the whole life cycle of organisms will be disrupted.

Ans. Consumers are the organisms who derive energy by eating plants or other organisms as they cannot produce food on their own. Absence of primary consumers in nature would lead to enormous growth of plants and decline in the population of carnivore animals, who eat them. Hence, the whole food web will get disrupted.

Ans. The direction of energy transfer in following cases are as follows:

(a) Primary consumer (grasshopper) to secondary consumer (frog)

(b) Producer (grass) to primary consumer (deer)

(c) Primary consumer (deer) to secondary consumer (lion)

Ans. Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. The lower trophic level of an ecosystem has a greater number of individuals than the higher trophic levels. Removal of producers will affect all the organisms of successive trophic levels and it will threat their survival. The removal of higher trophic level will lead to increase in organisms of lower trophic level and the organisms of higher trophic level will die due to the shortage of food.

Ans. No, removal of all organisms of a trophic level will disturb the ecosystem. Killing of higher trophic level organisms will cause explosion in the population of lower trophic level organisms. This will adversely affect the ecosystem and thus environment.

Ans. The producers convert solar energy into chemical energy in the form of organic compounds. The primary consumers (herbivores) derive their nutrition from the producers. According to the energy transfer law, only 10% of energy is transferred from one trophic level to the other.

So, the energy that is captured by the producers does not revert back to the Sun and the energy transferred to the herbivores does not come back to the producers. It just keeps on moving to the next trophic level in one direction. That is why the flow of energy in the food chain is always unidirectional.

Ans. A large number of pesticides and chemicals are used to protect our crops from pests and diseases. Some of these chemicals are washed down from the soil, while some enter the water bodies. From the soil, they are absorbed by plants along with water and minerals and from the water bodies, they are taken up by aquatic plants and animals. This is how these chemicals enter the food chain.

As these chemicals cannot decompose, they accumulate progressively at each trophic level. This increase in the concentration of harmful chemicals with each step of the food chain is called biomagnification. As human beings occupy the top level in any food chain, these chemicals get accumulated in our bodies in considerably high amount causing diseases.

Undesirable activities of man eliminate growth of organisms belonging to one or more trophic levels in a food chain. Thus, the food chain gets shortened, e.g. hunting tigers for their skin, etc.

It causes imbalance in the functioning of ecosystem and biosphere. If organisms of one trophic level are eliminated, the organisms prior to that trophic level will flourish and increase in number. Also, the organisms of the subsequent trophic level will sharply decrease, thereby creating an imbalance.

Vegetarian food chain is advantageous in terms of energy because it has less number of trophic levels As we know, only 10% of the energy is transferred to the next trophic level in a food chain, so if a person is vegetarian then, he would have maximum amount of energy by consuming producers or plants in a food chain.

Ans. Some harmful effects of agricultural practices on the environment are as follows

(i) Soil degradation: Extensive cropping causes loss of soil fertility. Also, over the time it can lead to soil erosion and finally to desertification.

(ii) Pollution: Use of synthetic chemical fertilisers and pesticides leads to soil, water and air pollution.

(iii) Water shortage: Excess use of groundwater for agriculture lowers the water level. This results in acute water shortage at many places.

(iv) Biomagnification: The chemical pesticides, being non-biodegradable accumulate in organisms in increasing amounts at each trophic level.

(v) Deforestation: Indiscriminate cutting of trees for agriculture has resulted in loss of habitat for wildlife. Thus, it also causes damage to natural ecosystem.

Ans. Ozone is a triatomic molecule, i.e., made up of three atoms of oxygen joined together. Its molecular formula is O₃. It can affect any ecosystem in the following ways

(i) It protects against ultraviolet rays if, present in stratosphere.

(ii) Ozone dissipates the energy of UV rays by undergoing dissociation followed by reassociation.

(iii) In atmosphere, it is highly toxic and causes injury to mucous membranes, eye irritation and internal haemorrhages in animals and humans.

Environmental pollution is an undesirable change in the physical, chemical or biological characteristics of the natural environment, brought about by man’s activities. This pollution may affect the soil, water or air.

Non-biodegradable pollutants include DDT, radioactive waste, plastic, insecticides

Some daily life eco-friendly activities are

(i) Save a tree, use less paper: You can buy tree-free 100% post-consumer recycled paper for everything from greeting cards to toilet paper. Paper with a high post-consumer waste content uses less pulp and keeps more waste paper out of landfills.

(ii) Opt bamboo for hardwood floors: Bamboo is considered as an environmental-friendly flooring material due to its high yield and the relatively fast rate at which it replenishes itself. It takes just 4-6 years for bamboo to mature, compared to 50 – 100 years for typical hardwoods. Also look for sources that use formaldehyde-free glues.

(iii) Reduce plastics, reduce global warming: Unfortunately, plastics are made from petroleum, the processing and burning of which is considered one of the main contributors to global warming, according to the EPA. In addition, sending plastics to the landfill also increases greenhouse gases. Reduce, reuse and recycle our plastics are one of the best ways to combat global warming.

(iv) Use healthier paints: Conventional paints contain solvents, toxic metals and Volatile Organic Compounds (VOCs) that can cause smog, ozone pollution and indoor air quality problems with negative health effects, according to the EPA. These unhealthy ingredients are released into the air, while we are painting, drying of paint and even after the paints are completely dry.

(v) Use compost: Instead of using synthetic fertilisers, compost provides a full complement of soil organisms and the balance of nutrients needed to maintain the soil’s health. Healthy soil minimises the population of weeds.

Ans. Materials that remain for a long time in the environment, without getting decomposed by any natural agents, also causing harm to the environment are called non-biodegradable. Plastic cups are non-biodegradable and raised the concern towards hygiene, thus they were replaced by kulhads.

Kulhads are made up of clay on a large scale resulted in the loss of top fertile soil. It is replaced by disposable paper cups because the paper can be recycled, it is biodegradable and is eco-friendly material which does not cause environment pollution.