Test: Class 7 General Science NCERT Based - 4 - UPSC MCQ

Explanation:

• Snow is not a liquid form of water, it is a solid form of water.


• Lake water and river water are both liquid forms of water.


• Water vapour is a gaseous form of water, not a liquid form.


• Ice is a solid form of water, not a liquid form.

Therefore, the correct options are A: 1, 4 and 5 only.

• All animals, whether herbivores or carnivores, depend ultimately on plants for food. Organisms which feed on plants often get eaten by other organisms, and so on.

• For example, grass is eaten by insects, which in turn, is taken by the frog. The frog is consumed by snakes.

• This is said to form a food chain: Grass → insects → frog → snake → eagle. Many food chains can be found in the forest. All food chains are linked. If any one food chain is disturbed, it affects other food chains too.

• A primary consumer is an organism that feeds on primary producers. Organisms of this type make up the second trophic level and are consumed or predated by secondary consumers, tertiary consumers or apex predators.

• Primary consumers are usually herbivores that feed on autotrophic plants, which produce their own food through photosynthesis.

• Cactus is a desert plant. Desert plants lose very little water through transpiration. The leaves in desert plants are either absent, very small, or they are present in the shape of spines.

• This helps in reducing loss of water from the leaves through transpiration.The leaf-like structure you see in a cactus is, in fact, photosynthesis in these plants is usually carried out by the stems. The stem is also covered with a thick waxy layer, which helps to retain water.Most desert plants have roots that go very deep into the soil for absorbing water.

• While respiration, the exchange of gases in plants occurs through the leaves. Plants take in the air through the stomata and utilise the oxygen.

• They release carbon dioxide into the atmosphere. During photosynthesis, plants use carbon dioxide in the presence of sunlight to make their own food and release oxygen. Plants make their food only during the day; while they respire during the day and night both.

• Oxygen released during photosynthesis is much more than that used during respiration.

• Municipal Solid Waste, also called garbage or trash, is nonhazardous disposable materials generated by households, institutions, industries, agriculture, and sewage.

• It is made up of waste, organics, and recyclable materials, with the municipality overseeing its disposal. Typically, municipal solid waste is collected, separate and sent to either a landfill or municipal recycling center for processing.

• An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. In contrast, an anaerobic organism (anaerobe) is any organism that does not require oxygen for growth. Some anaerobes react negatively or even die if oxygen is present.

• Pollution of water bodies by mercury causes Minamata disease in humans and Dropsy in fishes. Lead causes dysplasia, cadmium poisoning causes Itai – Itai disease.

• Accumulation of arsenic in the body parts like blood, nails and hairs causing skin lesions, rough skin, dry and thickening of skin and ultimately skin cancer.

• Eutrophication occurs when fresh water is artificially supplemented with nutrients, which causes an abnormal plant growth. The output of waste into the water bodies from industries, agriculture, and urban communities generally exceeds the biological capacities of aquatic systems.

• Runoff of chemical fertilizers from fields is a major cause. When organic matter exceeds the capacity of those microorganisms in water that break it down and recycle it, it encourages rapid growth, or blooms of algae.

• When they die, remains of the dead algae add further to the organic wastes already in water; eventually, water becomes deficient in oxygen.

• Wetlands are areas lying along the banks of rivers and lakes, and coastal regions. They are life-supporting systems providing fish, forest products, water, flood control, erosion buffering, a plant gene pool, wildlife, recreation, and tourism areas.

• Though they are endowed with a rich biodiversity yet of late, they are being greatly exploited.

• A number of factors have been responsible for the depletion of wetland areas mainly the mangrove forests, along the coasts of India. Intensive aquaculture development, deforestation, pollution from tankers, domestic waste, agricultural runoff, and industrial effluents are some of the factors.

• In 1981, Chilika Lake, India's largest brackish water lagoon, was the first site to be designated a Ramsar Wetland of International Importance.

• In a country like India where more than 50% of the population is rural-based, agriculture is one of the most important professions.

• The fields have to be regularly watered and there are large networks of irrigation systems all over the country. This sector is therefore the largest consumer of water in the country.

• In the past few years, various methods have been introduced to decrease the wastage of water in this sector. One of the methods that is becoming popular is that of drip irrigation.