Textbook - Our Environment Questions in English

(N/A) Trophic levels are the specific stages or steps in a food chain through which energy is transferred from one organism to another.
Example of a food chain:
Grass $\rightarrow$ Grasshopper $\rightarrow$ Frog $\rightarrow$ Snake $\rightarrow$ Peacock
The different trophic levels in this food chain are as follows:
$1$. Grass (Producer): First trophic level $(T_1)$
$2$. Grasshopper (Primary consumer): Second trophic level $(T_2)$
$3$. Frog (Secondary consumer): Third trophic level $(T_3)$
$4$. Snake (Tertiary consumer): Fourth trophic level $(T_4)$
$5$. Peacock (Quaternary consumer): Fifth trophic level $(T_5)$

(B) Decomposers break down the dead remains of plants and animals,which consist of complex organic substances,and convert them into simple inorganic substances.
Decomposers act upon all organic components present in the bodies of dead organisms.
These simple substances are then released back into the environment,where they can be reused by producers.
Thus,decomposers maintain the nutrient cycle and ecological balance in nature.

(N/A) Substances that can be broken down into simpler components through the process of decomposition by microorganisms are known as biodegradable substances.
Conversely,substances that cannot be decomposed or broken down by the action of microorganisms are referred to as non-biodegradable substances.

(N/A) Biodegradable substances affect the environment in the following two ways:
$(i)$ During the decomposition of biodegradable substances,foul odors are released,which pollute the surrounding air.
$(ii)$ Areas where moist biodegradable waste accumulates become breeding grounds for insects such as mosquitoes and houseflies. These insects act as vectors for pathogens and spread various diseases.

(N/A) Non-biodegradable substances affect the environment in two ways:
$(i)$ They do not decompose naturally. As a result,they accumulate in the ecosystem,leading to environmental pollution and biomagnification,which can be toxic to organisms.
$(ii)$ Substances like insecticides,detergents,and plastics pollute water bodies and soil,disrupting the natural balance of the ecosystem and harming aquatic and terrestrial life.

(N/A) Ozone is a natural gas composed of three atoms of oxygen. Its chemical formula is $O_{3}$. It is blue in colour and has a strong,pungent odour.
The ozone layer acts as a protective shield for the Earth by absorbing harmful ultraviolet $(UV)$ radiation from the sun. These $UV$ radiations are highly damaging to living organisms,as they can cause skin cancer,cataracts,and damage to the $DNA$ of plants and animals,thereby disrupting the balance of the ecosystem.

(N/A) The problem of waste disposal can be reduced in the following ways:
$(1)$ By segregating biodegradable and non-biodegradable waste into separate bins.
$(2)$ By composting biodegradable waste and using it as manure in a kitchen garden.
Two specific methods for effective waste management are as follows:
$(1)$ Recycling: Processing waste materials into new products to reduce the consumption of fresh raw materials.
$(2)$ Production of Biogas: Converting organic biodegradable waste into energy (biogas) and organic fertilizer.

(D) Wastes that are capable of being broken down or decomposed rapidly by the actions of microorganisms are called as biodegradable wastes.
Fruit-peels,cake,lime juice,wood,grass,flowers,and leather are all organic materials that can be easily decomposed by the action of microbes.
Therefore,all the items listed in options $A$,$B$,and $C$ are biodegradable.

(A) food-chain represents the sequence of organisms through which energy flows in an ecosystem,typically starting with a producer (plant) followed by consumers.
In the option $A$,Grass is a producer,Goat is a primary consumer (herbivore),and Human is a secondary or tertiary consumer (omnivore).
This sequence represents a valid flow of energy: $Grass \rightarrow Goat \rightarrow Human$.
Options $B$,$C$,and $D$ do not represent a logical feeding sequence where one organism consumes the other.

(B) Environment-friendly practices are actions that help in conserving natural resources and reducing pollution.
$1$. Carrying cloth-bags reduces the use of plastic bags, which are non-biodegradable and harmful to the environment.
$2$. Walking to school instead of using a motorized vehicle reduces the emission of greenhouse gases and pollutants.
$3$. Switching off unnecessary lights and fans helps in conserving electricity, which is often generated by burning fossil fuels.
Since all the mentioned options contribute to environmental protection, the correct answer is $All \text{ of the given options}$.

(B) If all the organisms or members of any trophic level are removed, the ecosystem will definitely be damaged.
For example, in the food chain: $Grass \rightarrow Grasshopper \rightarrow Frog \rightarrow Snake \rightarrow Peacock$.
If all grasshoppers are killed or removed, the frogs will not get food and will either die or migrate to another place in search of food.
If snakes are killed, the number of frogs will increase significantly, which will disturb the balance of the entire ecosystem.

(B) The impact of removing all organisms in a trophic level is indeed different for different trophic levels.
If producers are removed,the entire food chain collapses as there is no energy source.
If primary consumers are removed,producers overgrow and secondary consumers starve.
If top carnivores are removed,the population of lower trophic levels increases uncontrollably,leading to overgrazing and ecological imbalance.
Therefore,it is not possible to remove the organisms of any trophic level without causing significant damage to the ecosystem,as every level plays a crucial role in maintaining the balance of the food web.

(N/A) Biological magnification is the process of increasing the concentration of non-biodegradable toxic substances (such as pesticides or heavy metals) in the tissues of organisms at each successive trophic level of a food chain.
Yes,the levels of this magnification are different at different levels of the ecosystem.
The concentration of these chemicals increases as we move up the food chain.
Therefore,the maximum concentration is observed in the organisms at the highest trophic level (top carnivores),while the minimum concentration is found in the organisms at the lowest trophic level (producers).

(N/A) The following problems are caused by the non-biodegradable wastes generated by us:
$(i)$ Non-biodegradable waste cannot be decomposed into simpler forms by biological processes; therefore,it accumulates in the environment in its original form and causes pollution.
$(ii)$ The accumulation of such waste leads to the spread of various diseases and epidemics.
$(iii)$ It leads to the phenomenon of biomagnification,where toxic substances increase in concentration at each successive trophic level in a food chain.

(B) Even if all waste generated is biodegradable,it can still impact the environment if not managed properly.
$1$. Large quantities of biodegradable waste accumulating in one place can lead to the production of foul odors and the breeding of disease-carrying vectors like flies and mosquitoes.
$2$. If biodegradable waste is dumped into water bodies,it can lead to eutrophication,where the decomposition process consumes dissolved oxygen,harming aquatic life.
$3$. Therefore,while biodegradable waste is easier to manage through composting,it is not entirely harmless if left unmanaged or disposed of incorrectly.

(N/A) The ozone layer in the stratosphere protects living organisms on Earth from the harmful ultraviolet $(UV)$ radiation of the sun.
Damage or depletion of the ozone layer is a cause for concern because it allows more $UV$ radiation to reach the Earth's surface,which can cause serious health issues such as skin cancer,cataracts,and damage to the immune system in humans,as well as harm to plants and marine ecosystems.
To limit this damage,the United Nations Environment Programme $(UNEP)$ has taken significant steps.
$UNEP$ succeeded in forging an international agreement known as the Montreal Protocol,which mandates that all signatory countries freeze the production and consumption of chlorofluorocarbons $(CFCs)$ and other ozone-depleting substances at $1986$ levels to prevent further depletion of the ozone layer.