Our Environment

The non-living parts of an ecosystem are called abiotic components. Abiotic components include sunlight, water wind, temperature, altitude (height), soil, pH, and atmospheric gases.

Energy flow in an ecosystem is unidirectional. Energy always flow from sun to the producers and then to the consumers. 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.

When green plants are consumed by the herbivores (primary consumers) most of the energy is liberated as heat to the environment, some amount goes into digestion and some energy used for growth and reproduction. Only 10% of the food eaten is turned into its own body and made available for the next level of consumers.

i. The group of organisms that occupy the same level in a food chainis called trophic level.

ii. For example, in a grassland ecosystem, the different species of grasses are primary producers make up one trophic level.

iii. Similarly different species of grass eating animals (herbivores) are at one trophic level.

Biodegradable substances are those which can be breakdown or degraded by microorganisms such as bacteria and fungi. Cotton, rubber and leather are biodegradable substances in above given substances.

Non-biodegradable substances are those which cannot be breakdown or degraded by microorganisms such as bacteria and fungi. Glass is no-biodegradable substance in above given substances.

Aerosol and CFCs are substances that posed a threat to the environment

•Aerosol is a substance enclosed under pressure and released as a fine spray by means of a propellant gas. For example body deodorant, any of spray.

•CFCs or Chlorofluorocarbons are a group of man-made compounds containing chlorine, fluorine and carbon. They are harmful and cause depletion of ozone layer.

Full for of CFCs is chlorofluorocarbons, commonly known as Freon, CFCs are used in in air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans.

Ozone is formed naturally in the stratosphere layer of the atmosphere by a 2-steps reactive process. In the step-1, solar ultraviolet radiation (sunlight) breaks apart an oxygen molecule to form two separate oxygen atoms.

•Frog and rabbit belong to second trophic level as they are carnivores feed on plants or producers.

•Eagle and tiger belong to third trophic level as they are carnivores feed on herbivores or primary consumers.

As we know that only 10% of energy is transferred from the first trophic level to the next and 90 % of the energy lost as heat to the surroundings. Let’s understand with an example.

Let's assume that the plants or producers have 10 joules of energy, according to 10 % law, only 1 joule of energy will be available for transfer to next trophic level that is herbivores (deer) and 10 % of 1 joule that is 1.1 joule of energy is available for the carnivores (lion).

(a) Autotrophs prepare their food (carbohydrate) in presence of sunlight with the help of carbon dioxide and water. This process is called photosynthesis.

(b) According to 10% law, 10 % to 500J that is 50J is transferred to sheep (I consumer). Hence, 5J of energy is transferred to lion (II consumer) that is 10 % of 50 J.

Ozone is a gas layer present in the stratosphere. This layer protects living beings on the Earth from harmful ultraviolet (UV) rays coming from the Sun. Without the layer of ozone in the atmosphere, it would be very difficult for anything to survive on the surface. Depletion of the ozone layer has consequences on humans, animals and plants.

Disposable paper cups are advantageous over plastic cups as paper cups are bio-degradable and can be recycled. Whereas, plastic is very harmful and is non-biodegradable as well as a curse to the eco-system so it is better to use disposable paper cups which can be recycled easily. Therefore, using paper cups does not adversely affects environment.

The following consequences may occur due to decreases in number of carnivores in an ecosystem?

(i) Population of herbivores will increase due to absence of its predator.
(ii) Autotrophs will disappear from earth due to overgrazing done by herbivores.
(iii) Both these factors may disturb the food chain and food webs thus affecting the ecosystem.

Decomposers such as bacteria and fungi break down dead plants and animal wastes in the process of decomposition. During decomposition complex substances converted into simple inorganic nutrients such as carbon and nitrogen. These nutrients are back into the environment so, that the producers can use them.

The radiations from the Sun that are absorbed by ozone layer is ultraviolet (UV) radiation. UV radiation causes skin damage, in some cases the DNA damage causes genetic mutations. Prolonged exposure of UV radiation which can lead to skin cancer. Long exposure to eyes causes cataract.

Kulhads are made of soil. Use of earthen kulhads is not an environmentally friendly decision because for making enough kulhads upper layer of fertile soil is used. Loss of fertile soil can make land barren and unproductive. The removal of the layer of soil makes field to lose its fertility making it unfit for agriculture purpose.

The top consumers are those predators which have no natural enemies. Top consumers are different in different food chains. Each food chain end with a top consumer. Some examples of top consumers are alligator, hawk, polar bear and lion or tiger.

•Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels.

•Removing producers will affect herbivores heavily due to absence of food. They will die.

•Similarly, the carnivores would also die in absence of herbivores.

•Removing herbivores from the food chain, Producers would grow enormous; carnivores would not get food.

•Removing carnivores, the population of herbivores would increase to unsustainable levels.

•No, the organisms of any trophic level cannot be removed without causing any damage to the ecosystem? It will disturb the food web and will create ecological imbalance.

•Ozone layer is a high concentration of ozone molecules present in the stratosphere.

•The main function of the ozone layer is to absorb the Sun’s ultraviolet radiation, hence protecting the Earth from its harmful effects.

•Depletion of the ozone layer is a cause due to excessive use of CFCs or ammonia.

•Damage of ozone layer is cause of concern because ultra violet radiation from the sun will reach the earth and will effect human beings, plants and animals.

•After the Montreal Protocol, the Ozone layer is improving by the control use of CFCs and other harmful chemicals.

•DDT is an insecticide and is non-biodegradable compound.

•Once this insecticide sprayed in the environment, it stays for very long time and through food chain into the organisms.

•According to the concept of biomagnification, the maximum accumulation of a non-biodegradable pollutant is maximum in the highest trophic level.

•Hence, DDT gets accumulates at each trophic level and since, man is at the highest trophic level, there is maximum accumulation of DDT observed in them.

A food web having three food chain:

•Sun is the only source of energy. Producers convert solar energy into chemical energy in the form of food.

•The primary consumers (herbivores) depends on producers for food.

•According to the energy transfer law, only 10% of energy is transferred from one trophic level to the other.

•Therefore, the energy that is captured by the producers does not come 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 a unidirectional way.

•That is why the flow of energy in the food chain is always unidirectional.

(a) In a forest the steps of food chain:

Trees (producers) – Deer (primary consumer) – Lion (top consumer).

(b) In a grassland the steps of food chain

Grasses (producers) – rabbit (primary consumer) – snake (secondary consumer) –owl (top consumer).

(c) In a pond the steps of food chain

Algae and aquatic plants (producers) – small fish (primary consumer) – big fish (secondary consumer) –shark (top consumer).

•Non-biodegradable waste such as plastics, aluminium cans and pesticides are inert substances. These persist in the environment for very long time.

•This means that these substances require landfills for dumping.

•Excess of fertilizers, pesticides and other chemicals cause soil infertility and also affects aquatic life.

•Most of non-biodegradable chemicals are easily absorbed by the organisms causing biological magnification.

A network of different food chain operating at the same time is called food web. In food web organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level.

Sun is the ultimate source of energy in an ecosystem. Energy always flows from sun to the producer through photosynthesis. From producers energy transfers to different consumers. It always flow from sun to producer and then to consumers.

Disposable plastic plates are made of non-degradable materials. Materials made of Plastic cannot be degrade or decomposed by mroorganisms such as bacteria and fungi.

Chlorofluorocarbons (CFCs) are also called Freon. These compounds released into the atmosphere from spray cans, refrigerators, air conditioners. CFCs cause chemical reactions that break down ozone molecules. This causes reduction in absorption of ultraviolet radiation by ozone.

In a food chain organism which synthesise carbohydrates from inorganic compounds using radiant energy are called producers. These are autotrophs and make food for consumers.

Energy available for transfer to the next level is in the form of food which is carbohydrate, a chemical energy.

Population of tiger will decrease due to absence its food (deer) and the population of grass will increase in the absence its consumer (deer).

The decomposers are considered as cleaner of the Earth. Decomposers such as bacteria and fungi break down or decompose dead and decaying organic matter into simpler or inorganic forms.

The third trophic level is occupied by the II consumer. II consumers are carnivores which feed on herbivores or grass eating animals. Carnivores are tiger, wolf, etc.

Ecosystem is the interactions among living (biotic) organisms, and non-living things (abiotic).

As we know only 10 % of the total energy available at any trophic level is transferred to the next higher trophic level. So, as we move up the higher trophic level, the energy keeps on decreasing. Therefore, decrease in energy at higher trophic limits the food chain.

In the given food chain fourth trophic level is occupied by snakes. The available energy is 5 kJ at snakes, so at the producer level energy should be 5000 kJ. Grasshopper will get 500 kJ energy as per 10 % law and frog will get 50 kJ and then snake will get 5 kJ energy which is 10 % of 50 kJ.

•Biological magnification occurs when the number of chemicals and toxins increase and accumulate through the trophic levels of a food chain.

•Chemical substances from crop fields and industries are released into the environment, making their way toward food chains and food webs.

•Normally biological magnification doesn’t affect directly but exposure to these harmful chemicals may cause some long-term side effects.

An artificial ecosystem is a man-made system where there is interaction among plants, animals, and people living in an area together with their surroundings. Examples are crop fields, aquarium.

Trophic level 1 (T1) is occupied by primary producers. They utilizes sun energy and produce food (carbohydrate). Since producers occupies base of the pyramid, have maximum energy and numbers.

False.

The length of the food chain is different in different food chain. It depends on the amount of energy is available at producers and on population size of consumer.

False.

No, the energy flow in an ecosystem is always unidirectional. It always flow only from the Sun to the producer and then to consumers, not vie-versa.

False.

The flow of organic matter in a food chain is bidirectional, through biogeochemical cycles, nutrients obtained after decomposition are cycled back to the soil.

False.

Only 10 % of the available energy is transferred to the next trophic level, most of the energy is lost to environment as heat.

False

In a terrestrial ecosystem, the green plants capture about 1% of the energy of sunlight that falls on their leaves and converts it into food energy.

True

Only 10 % of the available energy is transferred to the next trophic level.

True

As we move up in ecological pyramid, number of individuals keeps on decreasing.

True

Chemical substances from crop fields and industries are released into the environment, make their way toward food chains and food webs. This is biological magnification. It doesn’t affect directly but exposure to these harmful chemicals may cause some long-term side effects.