Environmental Science Online Test 9th Science Lesson 24 Questions in English

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“Nature has the power to refresh and renew” 

– Helen Keller

Elements of nature continuously undergo changes and transformations. Environmental protection provides holistic knowledge about natural processes, effects of human intervention and solutions to overcome environmental problems.

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Environmental issues such as pollution, global warming, ozone layer depletion, acid rain, deforestation, landslide, drought and desertification have gained major focus across the world.

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Natural resources are recycled over and over again on earth for continued availability. At the same time, it also reminds us of our responsibility to reduce and restrain our activities that will affect the natural processes.

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Living organisms adjust themselves according to their habitat and changes in the ecosystem. All living organisms develop certain morphological, anatomical, physiological and reproductive adaptations which help them to survive better and to withstand environmental conditions.

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Biosphere is the part of the earth where life exists. All resources of biosphere can be grouped into two major categories namely Biotic and Abiotic.

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Abiotic or non-living factors which include all factors like temperature, pressure, water, soil, air and sunlight which affect the ability of organisms to survive and reproduce.

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There is a constant interaction between biotic and abiotic components in the biosphere and that makes the biosphere a dynamic and stable system.

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Cyclic flow of nutrients between non-living and living factors of the environment are termed as bio–geo-chemical cycles.

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Some of the important biogeochemical cycles are:

• Water cycle 
• Nitrogen cycle 
• Carbon cycle

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Water cycle or hydrological cycle is the continuous movement of water on earth. In this process, water moves from one reservoir to another by processes such as evaporation, sublimation, transpiration, condensation, precipitation, surface runoff and infiltration, during which water converts itself to various forms like liquid, solid and vapour.

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Evaporation is a type of vaporization, where liquid is converted to gas before reaching its boiling point. Water evaporates from the surface of the earth and water bodies such as the oceans, seas, lakes, ponds and rivers.

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Sublimation:

Sublimation is conversion of solid to gas, without passing through the intermediate liquid phase

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Ice sheets and ice caps from north and south poles, and icecaps on mountains, get converted into water vapour directly, without converting into liquid.

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Transpiration is the process by which plants release water vapour into the atmosphere through stomata in leaves and stems.

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Condensation is the changing of gas phase into liquid phase and is the reverse of vaporisation. At higher altitudes, the temperature is low. The water vapour present there condenses to form very tiny particles of water droplets. These particles come close together to form clouds and fog.

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Due to change in wind or temperature, clouds combine to make bigger droplets, and pour down as precipitation(rain). Precipitation includes drizzle, rain, snow and hail

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As the water pours down, it runs over the surface of earth. Runoff water combines to form channels, rivers, lakes and ends up into seas and oceans. Some of the precipitated water moves deep into the soil. Then it moves down and increases the ground water level.

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Some of the precipitated water flows through soil and porous or fractured rock. Infiltration and percolation are two related but different processes describing the movement of water through soil.

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Major human activities affecting the water cycle on land are urbanisation, dumping of plastic waste on land and into water, polluting water bodies and deforestation.

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Nitrogen is the important nutrient needed for the survival of all living organisms. It is an essential component of proteins, DNA and chlorophyll.

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Atmosphere is a rich source of nitrogen and contains about 78% nitrogen. Plants and animals cannot utilize atmospheric nitrogen.

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Plants and animals cannot utilize atmospheric nitrogen. They can use it only if it is in the form of ammonia, amino acids or nitrates. Processes involved in nitrogen cycle are explained below.

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Nitrogen fixation is the conversion of atmospheric nitrogen, which is in inert form, to reactive compounds available to living organisms. This conversion is done by a number of bacteria and blue green algae (Cyanobacteria).

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Leguminous plants like pea and beans have a symbiotic relationship with nitrogen fixing bacteria Rhizobium. Rhizobium occur in the root nodules of leguminous plants and fixes nitrogenous compounds.

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Plants absorb nitrate ions and use them for making organic matter like proteins and nucleic acids. Herbivorous animals convert plant proteins into animal proteins. Carnivorous animals synthesize proteins from their food.

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Animal proteins are excreted in the form of urea, uric acid or ammonia. The putrefying bacteria and fungi decompose these animal proteins, dead animals and plants into ammonium compounds.

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The ammonium compounds formed by ammonification process are oxidised to soluble nitrates. This process of nitrate formation is known as nitrification. The bacteria responsible for nitrification are called as nitrifying bacteria.

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Free living soil bacteria such as Pseudomonas sp. reduce nitrate ions of soil into gaseous nitrogen which enters the atmosphere

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Burning fossil fuels, application of nitrogen-based fertilizers and other activities can increase the amount of biologically available nitrogen in an ecosystem. Nitrogen applied to agricultural fields enters rivers and marine systems. It alters the biodiversity, changes the food web structure and destroys the general habitat

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Carbon occurs in various forms on earth. Charcoal, diamond and graphite are elemental forms of carbon. Combined forms of carbon include carbon monoxide, carbon dioxide and carbonate salts.

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All living organisms are made up of carbon containing molecules like proteins and nucleic acids. The atmospheric carbon dioxide enters into the plants through the process of photosynthesis to form carbohydrates. From plants, it is passed on to herbivores and carnivores.

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During respiration, plants and animals release carbon into atmosphere in the form of carbon dioxide. Carbon dioxide is also returned to the atmosphere through decomposition of dead organic matter, burning fossil fuels and volcanic activities.

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More carbon moves into the atmosphere due to burning of fossil fuels and deforestation. Most of the carbon in atmosphere is in the form of carbon dioxide. Carbon dioxide is a greenhouse gas. By increasing the amount of carbon dioxide, earth becomes warmer. This leads to greenhouse effect and global warming.

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Any feature of an organism or its part that enables it to exist under conditions of its habitat is called adaptation. On the basis of water availability, plants have been classified as: 

• Hydrophytes 
• Xerophytes 
• Mesophytes

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Plants growing in or near water are called hydrophytes. Hydrophytes may be free floating or submerged plants living in lakes, ponds, shallow water, marshy lands and marine habitat. Hydrophytes face certain challenges in their habitat.

Explanation 

Hydrophytes face certain challenges in their habitat. They are:

• Availability of more water than needed
• Water current may damage the plant body
• Water levels may change regularly
• Maintain buoyancy in water

Explanation

Adaptations of hydrophytes:

• Roots are poorly developed as in Hydrilla or absent as in Wolffia.
• Plant body is greatly reduced as in Lemna.
• Submerged leaves are narrow or finely divided. e.g. Hydrilla.

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Floating leaves have long leaf stalks to enable the leaves move up and down in response to changes in water level. e.g. Lotus.

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Air chambers provide buoyancy and mechanical support to plants as in Eichhornia (swollen and spongy petiole).

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Plants that grow in dry habitat are called xerophytes. These plants develop special structural and physiological characteristics to meet the conditions.

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Xerophytes develop special structural and physiological characteristics to meet the following conditions:

• To absorb as much water as they can get from the surroundings.
• To retain water in their organs for very long time. 
• To reduce the transpiration rate. 
• To reduce consumption of water

Explanation 

• They have well developed roots. Roots grow very deep and reach the layers where water is available as in Calotropis. 
• They store water in succulent water storing parenchymatous tissues. e.g. Opuntia, Aloe vera. 
• They have small sized leaves with waxy coating. e.g. Acacia. In some plants, leaves are modified into spines. e.g. Opuntia.

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Mesophytes are common land plants which grow in situations that are neither too wet nor too dry. They do not need any extreme adaptations.

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Adaptations of mesophytes:

1. The roots of mesophytes are well developed and are provided with root caps. 
2. The stem is generally straight and branched. 
3. The leaves are generally broad and thin. 
4. The presence of waxy cuticle in leaves traps the moisture and lessens water loss. 
5. Leaves have stomata which close in extreme heat and wind to prevent transpiration

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Animals can adapt themselves according to their habitat. Temperature and light are forms of energy which influence various stages of life activities such as growth, metabolism, reproduction, movement, distribution and behaviour. Animals develop special features or behaviour patterns to escape from extreme conditions of temperature and light.

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Bats are the only mammals that can fly. Mostly, bats live in caves. Apart from caves, bats also live in trees, hollowed logs and rock.

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Bats are active at night. This is a useful adaptation for them, as flight requires a lot of energy during day. Their thin, black wing membrane (Patagium) may cause excessive heat absorption during the day. This may lead to dehydration.

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Forelimbs are modified serve wings. Tail supports and controls movements during flight. Muscles are well developed and highly powerful and achieve in beating of wings. Tendons of hind limbs provide a tight grasp when the animals are suspended upside down at rest.

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Hibernation is a state of inactivity in which the body temperature drops with a lowered metabolic rate during winter.

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Bats are warm blooded animals but unlike other mammals, they let their internal temperature reduce when they are resting. They go to a state of decreased activity to conserve energy.

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Bats use a remarkable high-frequency system called echolocation. Bats give out high-frequency sounds (ultrasonic sounds). These sounds are reflected back from its prey and perceived by the ear. Bats use these echoes to locate and identify the prey.

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Earthworm is commonly found in soil, feeding on live and dead organic matter. Earthworm plays a vital role in maintaining soil fertility. It facilitates aeration, water infiltration and producing organic matter to increase crop growth.

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The earthworm has a cylindrical, elongated and segmented body. This helps them to live in narrow burrows underground and for easy penetration into the soil. Mucus covers the skin which does not allow soil particles to stick to it. Moist skin helps in oxygenation of blood.

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Earthworm body is flexible having circular and longitudinal muscles which help in movement and subsoil burrowing. Each segment on the lower surface of the body has number of setae. They help the earthworm to move through the soil and provide anchor in the burrows.

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When the soil becomes too hot or dry, earthworms become inactive and undergo a process called aestivation. Earthworm moves deeper into the soil.

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Earthworms are referred as ‘Farmer’s friend’. After digesting organic matter, earthworms excrete a nutrient-rich waste product called castings which is used as Vermicompost.

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Earthworms are sensitive to light. It has no eyes but can sense light through light sensitive cells (Photoreceptors) present in their skin. They react negatively to bright light (Photophobic). It remains in its burrow during the day to avoid light.

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Water conservation is the preservation, control and management of water resources. It also includes activities to protect the hydrosphere and to meet the current and future human demand.

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Importance of Water Conservation:

• It creates more efficient use of the water resources. 
• It ensures that we have enough usable water.  
• It helps in decreasing water pollution. 
• It helps in increasing energy saving.

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World Water Day on 22nd March every year, is about focusing attention on the importance of water. Agricultural water is often lost due to leaks in canals, run off and evaporation.

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Farm ponds are used as one of the strategies to support water conservation. Much of the rainfall runs off the ground. The run off not only causes loss of water but also washes away precious top soil. Farm ponds help the farmers to store water and to use it for irrigation.

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Water recycling, apart from rain water harvesting, is also one of the key strategies to conserve water. Water recycling is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, industrial processes, flushing in toilets and ground water recharge.

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Primary treatment involves temporary holding of the wastewater in a tank. The heavy solids get settled at the bottom while oil, grease and lighter solids float over the surface. The settled and floating materials are removed. The remaining liquid undergoes secondary treatment.

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Tertiary or advanced treatment is the final step of sewage treatment. It involves removal of inorganic constituents such as nitrogen, phosphorus and microorganisms. The fine colloidal particles in the sewage water are precipitated by adding chemical coagulants like alum or ferric sulphate.

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IUCN is an international organization working in the field of nature conservation and sustainable use of natural resources. IUCN is the global authority on the status of the natural world and the measures needed to safeguard it.

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The organization is best known to the wider public for compiling and publishing the IUCN red list of threatened species, which assesses the conservation status of species worldwide. India, a mega diverse country with only 2.4 % of world’s land area, accounts for 7-8% of all recorded species. 

Explanation 

IUCN recorded species in India includes over 45,000 species of plants and 91,000 species of animals. The mission of IUCN is to influence, encourage and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable.

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The country’s diverse physical features and climatic conditions have resulted in a variety of ecosystems such as forests, wetlands, grasslands, desert, coastal and marine ecosystems. Four of 34 globally identified biodiversity hotspots are found in India.

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India became state member of IUCN in 1969, through the Ministry of Environment, Forest and Climate change (MoEFCC).

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IUCN (International Union for Conservation of Nature and Natural Resources) was founded on 5th October 1948 at Gland, Switzerland