Test: Environment & Ecology - 3 (July 23, 2021)


25 Questions MCQ Test UPSC CSE Prelims 2021 Mock Test Series | Test: Environment & Ecology - 3 (July 23, 2021)


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QUESTION: 1

With reference to animal and plant biodiversity on earth, consider the following statements:

  1.  

    Animals constitute more than two-thirds of the total species on earth.

  2.  

    There are more types of fishes than types of insects.

  3.  

    India is one of the megadiverse countries in the world with 20 percent of the total global species diversity.

 

Which of the statements given above is/are correct?

Solution:
  • According to IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million. Estimates vary widely and many of them are only educated guesses.

  •  

    Statement 1 is correct and statement 2 is not correct: More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms, and angiosperms) comprise no more than 22 per cent of the total. Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. That means, out of every 10 animals on this planet, 7 are insects. The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles, and mammals.

  •  

    Statement 3 is not correct: Although India has only 2.4 per cent of the world‘s land area, its share of the global species diversity is an impressive 8.1 per cent. That is what makes our country one of the 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India.

 

 

 

 

 

QUESTION: 2

An intermediate stage found in ecological succession in an ecosystem depicting the diversity of species of organisms, an increase in the number of species and organism as well as an increase in total biomass in a given area is termed as

Solution:
  • An important characteristic of all communities is that composition and structure constantly change in

response to the changing environmental conditions. This change is orderly and sequential, parallel with the changes in the physical environment. These changes lead finally to a community that is in near equilibrium with the environment and that is called a climax community. The gradual and fairly predictable change in the species composition of a given area is called ecological succession. During succession some species colonise an area and their populations become more numerous, whereas populations of other species decline and even disappear.

  • The entire sequence of communities that successively change in a given area are called sere(s). The individual transitional communities are termed seral stages or seral communities. In the successive seral stages there is a change in the diversity of species of organisms, increase in the number of species and organisms as well as an increase in the total biomass. Hence option (a) is the correct answer.

  • Based on the nature of the habitat – whether it is water (or very wet areas) or it is on very dry areas – succession of plants is called hydrach or xerarch, respectively. Hydrarch succession takes place in wetter areas and the successional series progress from hydric to the mesic conditions. As against this, xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions.

  • An ecological niche is a role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. A species' niche includes all of its interactions with the biotic and abiotic factors of its environment. Biotic factors are living things, while abiotic factors are nonliving things.

QUESTION: 3

Photoperiod is the duration of light received daily and seasonally by living organisms. It impacts:

  1. Coordination of opening of buds and flowers in a plant

  2. Migration cycles of birds

  3. The breeding time of mammals

Select the correct answer using the code below.

Solution:
  • Living organisms receive light by light receptors (e.g. eye, photoreceptors, stigma, ocellus, etc.) Thus, light is used as a stimulus for activity cycles. The duration of light received daily and seasonally is called photoperiod. For example, when the duration of daylight reduces, animals go into hibernation.

  • Photoperiodism is the functional or behavioural response of an organism to changes of duration in daily, seasonal, or yearly cycles of light and darkness. Photoperiodic reactions can be reasonably predicted, but temperature, nutrition, and other environmental factors also modify an organism‘s response.

  • It causes programming of life cycles, coordination of opening of buds and flowers in plants and migration in animals. Breeding time in most organisms is determined by photoperiod in such a way that the offspring have the greatest chance of survival. Hence statement 1 is correct.

  • In animals, the regular activities of migration, reproduction, and the changing of coats or plumage can be induced out of season by artificially altering daylight. Birds, for example, have migrated north in the winter after having been exposed to reversed seasonal lighting in laboratories. The manipulation of a specific stimulating period of darkness, which is required by each species for every phase of the migratory process, is an important factor in photoperiodism. Hence statement 2 is correct.

  • When stimulated by light, an animal‘s pituitary gland will release hormones that affect reproduction. Thus, the mating season of a species can be made to occur at an unusual time by manipulating daylight. Long periods of light followed by short periods will induce mating behavior in species that normally breed in autumn (e.g., goats and sheep), while spring breeders (e.g., mink) will start the reproductive process when daylight is increased. Application of photoperiodism is common in the poultry industry, as daylight affects egg-laying, mating, and the bodyweight of the fowl. Hence statement 3 is correct.

QUESTION: 4

In the polar regions, small-sized animals are rare. What is the reason behind this?

Solution:
  • An overwhelming majority of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. In aquatic animals, the osmotic concentration of the body fluids changes with that of the ambient water osmotic concentration.

  • These animals and plants are simply conformers. Thermoregulation is energetically expensive for many organisms. This is particularly true for small animals like shrews and hummingbirds. Heat loss or heat gain is a function of surface area. Since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside; then they have to expend much energy to generate body heat through metabolism. This is the main reason why very small animals are rarely found in polar regions. Hence option (d) is the correct answer.

  • Allen's rule, an ecogeographical rule, states that significant differences exist in the size of limbs and other external organs of animals, even within the same species, depending on the geographical region in which they live. Animals living in colder regions of the world, for instance, have shorter limbs than those living in warmer regions as an adaptation to control the dissipation of heat. A smaller body surface area helps animals in colder regions stay warm by slowing down the loss of body heat. · During the course of evolution, the costs and benefits of maintaining a constant internal environment are taken into consideration. Some species have evolved the ability to regulate, but only over a limited range of environmental conditions, beyond which they simply conform.

QUESTION: 5

With reference to National Board for Wildlife, consider the following statements:

  1. It has been constituted under the Wildlife Protection Act, 1972.

  2. It is headed by Minister of Environment, Forest and Climate Change.

  3. Its recommendations are binding on the union government.

Which of the statements given above is/are correct?

Solution:
  • Statement 1 is correct: National Board for Wild Life is a ―Statutory Organization‖ constituted under the Wildlife Protection Act, 1972.

  • Statement 3 is not correct: The board is advisory in nature and advises the Central Government on framing policies and measures for conservation of wildlife in the country. However, it is a very important body because it serves as apex body to review all wildlife-related matters and approve projects in and around national parks and sanctuaries.

  • Statement 2 is not correct: The NBWL is chaired by the Prime Minister. It has 47 members including the Prime Minister. Among these, 19 members are ex-officio members. Other members include three Members of Parliament (two from Lok Sabha and one from Rajya Sabha), five NGOs and 10 eminent ecologists, conservationists and environmentalists.

  • The Indian Board for wildlife in its 15th meeting held in the year 1983 decided to prepare National wildlife Action Plan. Accordingly, the First National wildlife Action Plan was adopted in the year 1983 and was implemented upto 2001. Subsequently second National wildlife action plan was in operation from 2002 to 2016. Presently third wildlife action plan is in operation for period 2017 to 2031.

QUESTION: 6

With reference to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), consider the following statements:

  1. It aims to ensure that international trade in specimens of wild animals and plants does not threaten their survival.

  2. It was adopted under the aegis of United Nations Framework Convention on Climate Change.

  3. It is legally binding on the Parties.

Which of the statements given above is/are correct?

Solution:
  • Statement 1 is correct: CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) is an international agreement between governments. Its aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.

  • Statement 2 is not correct: CITES was drafted as a result of a resolution adopted in 1963 at a meeting of members of IUCN (The World Conservation Union). The text of the Convention was finally agreed at a meeting of representatives of 80 countries in Washington, D.C., the United States of America, on 3 March 1973, and on 1 July 1975 CITES entered in force.

  • Statement 3 is correct: CITES is an international agreement to which States and regional economic integration organizations adhere voluntarily. States that have agreed to be bound by the Convention ('joined' CITES) are known as Parties. Although CITES is legally binding on the Parties – in other words they have to implement the Convention it does not take the place of national laws. Rather it provides a framework to be respected by each Party, which has to adopt its own domestic legislation to ensure that CITES is implemented at the national level.

QUESTION: 7

Which of the following species are extinct?

  1. Dodo

  2. Quagga

  3. Passenger Pigeon

  4. Steller’s Sea Cow

Select the correct answer using the code given below.

Solution:
  • The human activities have emerged as a major cause for the loss of biological. The colonisation of the tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds.

  • The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is the world's most comprehensive inventory of the global conservation status of plant and animal species. It uses a set of quantitative criteria to evaluate the extinction risk of thousands of species. These criteria are relevant to most species and all regions of the world. · Of the world‘s 5,490 mammals, 79 are Extinct or Extinct in the Wild, with 188 Critically Endangered, 449 Endangered and 505 Vulnerable. There are 1,677 reptiles on the IUCN Red List, with 293 added recently. In total, 469 are threatened with extinction and 22 are already Extinct or Extinct in the Wild.

  • Some examples of recent extinctions include the dodo (Mauritius), quagga (Africa), thylacine (Australia), and three subspecies (Bali, Javan, Caspian) of tiger. The last twenty years alone have witnessed the disappearance of 27 species.

  • In addition, many species extinctions in the last 500 years like Steller‟s sea cow, passenger pigeon etc. have been due to overexploitation by humans.

  • Hence option (d) is the correct answer.

QUESTION: 8

Which of the following is/are examples of ex-situ conservation methods?

  1. National parks

  2. Botanical gardens

  3. Zoological parks

Select the correct answer using the code given below.

Solution:
  • When we conserve and protect the whole ecosystem, its biodiversity at all levels is protected - we save the entire forest to save the tiger. This approach is called in situ (on-site) conservation. However, when there are situations where an animal or plant is endangered or threatened (organisms facing a very high risk of extinction in the wild in the near future) and needs urgent measures to save it from extinction, ex-situ (offsite) conservation is the desirable approach.

  • Examples of in-situ conservation methods are biosphere reserves, national parks, sanctuaries, and sacred groves.

  • Examples of ex-situ conservation methods are Zoological parks, botanical gardens, and wildlife safari parks.

QUESTION: 9

Consider the following pairs:

Which of the pairs is/are correctly matched?

Solution:
  • Microbes are used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes. Examples of acid producers are:

    • Aspergillus niger (a fungus) of citric acid (it is a natural preservative and is also used to add an acidic (sour) taste to foods and soft drinks);

    • Acetobacter aceti (a bacterium) of acetic acid ( used in vinegar, used as an antiseptic against pseudomonas, staphylococci, etc., is also used in cervical cancer screening) ;

    • Clostridium butylicum (a bacterium) of butyric acid (aid in the prevention, management, and/or treatment of a variety of health conditions, including gastrointestinal problems, colon cancer, diabetes/metabolic disorders, and neurological disorders).

    • Lactobacillus (a bacterium) of lactic acid;

    • Yeast (Saccharomyces cerevisiae) is used for commercial production of ethanol;

    • Streptokinase produced by the bacterium Streptococcus and modified by genetic engineering is used as a ‘clot buster‘ for removing clots from the blood vessels of patients who have undergone myocardial infraction leading to heart attack.

    • Bioactive molecule, cyclosporin A, that is used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum.

    • Statins produced by the yeast Monascus purpureus have been commercialised as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

    • Hence only pair 3 is correctly matched.

QUESTION: 10

Consider the following statements regarding corals:

  1. They are mainly found in tropical oceans and seas.

  2. Most fishes lay eggs in coral colonies.

  3. Coral reefs have greater biodiversity than tropical rainforests.

Which of the statements given above is/are correct?

Solution:
  • The coral is a polyp, an organism that lives in the shallow sea. Its skeleton is composed of limestone and dolomite. The layers of deposition of the skeletons of these polyps form a shallow rock known as Coral Reef.

  • They thrive in tropical oceans confined between 25 degrees North and 25 degree south latitudes. Corals are found mainly in the tropical oceans and seas because they require a high mean annual temperature above 20 degree celsius. Hence statement 1 is correct.

  • Most fishes lay eggs in coral colonies. Hence statement 2 is correct.

  • Since coral polyps cannot survive above water level, coral reefs are found either up to sea level or below it.

  • The coral reefs are more diverse than tropical rainforests because coral reefs have more than 1,000,000 species. Hence statement 3 is correct.

QUESTION: 11

Consider the following statements regarding Biosphere Reserves:

  1. They are areas of terrestrial and coastal ecosystems promoting balance between their conservation and sustainable use.

  2. The "Man and the Biosphere (MAB) Programme" for establishing a coordinated World Network of biosphere reserves is an initiative of Convention on Biological Diversity (CBD).

Which of the statements given above is/are correct?

Solution:
  • Statement 1 is correct: Biosphere reserves are areas of terrestrial and coastal ecosystems promoting solutions to reconcile the conservation of biodiversity with its sustainable use. They are internationally recognized, nominated by national governments and remain under sovereign jurisdiction of the states where they are located.

  • Statement 2 is not correct: Launched in 1971, UNESCO‘s Man and the Biosphere Programme (MAB) is an Intergovernmental Scientific Programme that aims to establish a scientific basis for the improvement of relationships between people and their environments.MAB combines the natural and social sciences, economics and education to improve human livelihoods and the equitable sharing of benefits, and to safeguard natural and managed ecosystems, thus promoting innovative approaches to economic development that are socially and culturally appropriate, and environmentally sustainable. Its World Network of Biosphere Reserves currently counts 701 sites in 124 countries all over the world, including 21 transboundary sites.

  • There are 18 Biosphere Reserves in the country. Under the MAB Programme of the UNESCO, India has 11 internationally recognised biosphere reserves.

QUESTION: 12

With reference to Zoological Survey of India (ZSI), consider the following statements:

  1. It is a statutory body under Ministry of Environment, Forest and Climate Change.

  2. It undertakes Environmental Impact Assessments with regard to fauna.

  3. It prepares the Red Data Book, Fauna of India and Fauna of States.

Which of the statements given above is/are correct?

Solution:
  • The Zoological Survey of India (ZSI), a subordinate organization of the Ministry of Environment, Forest and Climate Change was established in 1916 as a national centre for faunistic survey and exploration of the resources leading to the advancement of knowledge on the exceptionally rich faunal diversity of the country. ZSI has its headquarters at Kolkata.

  • It has not been established under any act. Hence, it is not a statutory body.

  • Its activities include:

    • Study of the fauna of states

    • Fauna of conservation areas

    • Fauna of important ecosystems

    • Status survey of endangered species

    • Fauna of India and o Ecological Studies & Environmental impact assessments.

  • One of its primary objectives is: Preparation of Red Data Book, Fauna of India and Fauna of States. ·

  • ZSI undertakes Environmental Impact Assessment (EIA) with special reference to ecology and wildlife, and provides necessary services to assess possible impact and also on mitigating measures. ZSI assists development agencies in advising alternatives to minimize ecological damage both In short and long time frame perspectives.

QUESTION: 13

Emissions from which of the following sources can cause acid rain?

  1.  

    Volcanoes

  2.  

    Swamps

  3.  

    Plankton in the ocean

 

4 .Power generation from fossil fuels

Select the correct answer using the code given below.

Solution:
  • Acid rain means the presence of excessive acids in rainwater.

  •  

    The causes of acid rain are Sulfur and Nitrogen particles which get mixed with the wet components of rain. Sulfur and Nitrogen particles which get mixed with water are found in two ways either man-made i.e as the emissions are given out from industries or by natural causes. Natural causes of acid rain are oxides of sulphur and nitrogen from volcanoes, swamps and plankton in the oceans. However, most of the acids are produced by human activities like power generation from fossil fuels which produces around 70% of the SO2 produced in the atmosphere. However, this is not a natural source but is an anthropogenic source. Hence all the options are correct.

 

 

 

QUESTION: 14

With reference to the agricultural practices, consider the following statements:

  1. Inter-cropping method involves growing different crops simultaneously within the same plot.

  2. Mulching is the practice of cultivation of leguminous crops between the cropping seasons.

Which of the statements given above is/are correct?

Solution:
  • Statement 1 is correct: Intercropping involves growing different crops simultaneously within the same plot of land. This increases the yield and maximizes utilization of abiotic inputs, like efficient use of sunlight, water etc.

  • Statement 2 is incorrect: Mulches are generally waste plant materials. In mulching, these plant materials are spread around the base of the crops. It protects the soil from erosion, reduces compaction from the impact of heavy rains ,conserves moisture, reducing the need for frequent waterings, maintains a more even soil temperature and prevents weed growth

QUESTION: 15

Which among the following is the main assumption of the Limits to Growth theory?

Solution: The limits to growth theory, is a 1972 book about the computer simulation of exponential economic and population growth with finite resource supplies. It was funded by the Volkswagon Foundation and commissioned by the Club of Rome. It suggests that the environment cannot support rising resource utilisation beyond its carrying capacity. Hence option (a) is the correct answer.

QUESTION: 16

In the context of environment and ecology, Surangam and Zing are:EXplanation: er.

Solution:

The Indian government has started looking at means to revive the traditional systems of water harvesting in the country. Given that these methods are simple and eco-friendly for the most part, they are not just highly effective for the people who rely on them but they are also good for the environment.

  • Hence option (b) is the correct answ
QUESTION: 17

Consider the following statements:

  1. The total amount of water received in the form of rainfall over an area is called rainwater harvesting potential.

  2. The amount of water that can be effectively harvested out of total water received is called rainwater endowment.

Which of the statements given above is/are correct?

Solution:

  • Rainwater harvesting potential is the amount of water that can be effectively harvested out of total water received in an area. While the rainwater endowment is the total amount of water received in the form of rainfall over an area.
  • Hence both the statements are not correct.

QUESTION: 18

With reference to homeostasis, consider the following statements:

  1. It refers to the maintenance of the constancy of an organism’s internal environment despite varying external environmental conditions.

  2. Only mammals are capable of maintaining homeostasis.

Which of the statements given above is/are correct?

Solution:
  • Statement 1 is correct: The maintaining of the constancy of an organism‘s internal environment despite varying external environmental conditions is called homeostasis. · Some organisms are able to maintain homeostasis by physiological (sometimes behavioural also) means which ensures constant body temperature, constant osmotic concentration, etc. All birds and mammals, and a very few lower vertebrate and invertebrate species are indeed capable of such regulation (thermoregulation and osmoregulation).

  • Statement 2 is not correct: An overwhelming majority (99 per cent) of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. In aquatic animals, the osmotic concentration of the body fluids change with that of the ambient water osmotic concentration. These animals and plants are called conformers. ·

  • Thermoregulation is energetically expensive for many organisms. This is particularly true for small animals like shrews and humming birds. Heat loss or heat gain is a function of surface area. Since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside; then they have to expend much energy to generate body heat through metabolism.

QUESTION: 19

Which of the following statements regarding the effects of gaseous air pollutants is not correct?

Solution:
  • Statement (a) is correct: Oxides of sulphur are produced when sulphur containing fossil fuel is burnt. The most common species, sulphur dioxide, is a gas that is poisonous to both animals and plants. It has been reported that even a low concentration of sulphur dioxide causes respiratory diseases e.g., asthma, bronchitis, emphysema in human beings. Sulphur dioxide causes irritation to the eyes, resulting in tears and redness. High concentration of SO2 leads to stiffness of flower buds which eventually fall off from plants.

  • Statement (b) is correct: Dinitrogen and dioxygen are the main constituents of air. These gases do not react with each other at a normal temperature. At high altitudes when lightning strikes, they combine to form oxides of nitrogen. NO2 is oxidised to nitrate ion, NO3- which is washed into soil, where it serves as a fertilizer. In an automobile engine, (at high temperature) when fossil fuel is burnt, dinitrogen and dioxygen combine to yield significant quantities of nitric oxide (NO) and nitrogen dioxide (NO2). The irritant red haze in the traffic and congested places is due to oxides of nitrogen. Higher concentrations of NO2 damage the leaves of plants and retard the rate of photosynthesis. Nitrogen dioxide is a lung irritant that can lead to an acute respiratory disease in children. It is toxic to living tissues also. Nitrogen dioxide is also harmful to various textile fibres and metals.

  • Statement (c) is correct: Hydrocarbons are composed of hydrogen and carbon only and are formed by incomplete combustion of fuel used in automobiles. Hydrocarbons are carcinogenic, i.e., they cause cancer. They harm plants by causing ageing, breakdown of tissues and shedding of leaves, flowers and twigs.

  • Statement (d) is not correct: Carbon monoxide (CO) is one of the most serious air pollutants. It is a colourless and odourless gas, highly poisonous to living beings because of its ability to block the delivery of oxygen to the organs and tissues. It is produced as a result of incomplete combustion of carbon. Carbon monoxide is mainly released into the air by automobile exhaust. It binds to haemoglobin to form carboxyhaemoglobin, which is about 300 times more stable than the oxygen-haemoglobin complex. In blood, when the concentration of carboxyhaemoglobin reaches about 3–4 per cent, the oxygen carrying capacity of blood is greatly reduced. This oxygen deficiency, results into headache, weak eyesight, nervousness and cardiovascular disorder.

QUESTION: 20

Sacred Groves in India can be best defined as

Solution:

India has also a history of religious and cultural traditions that emphasised the protection of nature. In many cultures, tracts of forest were set aside, and all the trees and wildlife within were venerated and given total protection. Such sacred groves are found in Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, Western Ghat regions of Karnataka and Maharashtra and the Sarguja, Chanda and Bastar areas of Madhya Pradesh. In Meghalaya, the sacred groves are the last refuges for a large number of rare and threatened plants. Hence option (c) is the correct answer.

QUESTION: 21

Which of the following microbes can be used as an insecticide?

  1. Bacteria

  2. Fungi

  3. Virus

Select the correct answer using the code given below.

Solution:
  • All the microbes mentioned can be used as pesticides. Single cell organis ms, such as bacteria, fungi and protozoa, and viruses, have been mass produced and formulated for use in a manner similar to insecticides. Eg - Bacillus Thuringiensis. Hence all the options are correct. · Several fungi have been studied as potential microbial insecticides. Beauveria bassiana can affect a wide variety of arthropods.

  • Virus can also be used as insecticide. Baculoviruses are a family of naturally-occurring viruses known to infect only insects and some related arthropods. Most are so specific in their action that they infect and kill only one or a few species of Lepidoptera larvae (caterpillars), making them good candidates for management of crop pests with minimal off-target effects.

QUESTION: 22

Consider the following statements:

  1. While eurythermal organisms are those organisms which can survive in a wide range of temperatures, stenothermal organisms are restricted to a narrow range of temperatures.

  2. While all vertebrates are stenothermal, all invertebrates are eurythermal.

Which of the statements given above is/are correct?

Solution:
  • Living organisms are scattered all over the world. However, their distribution is not even. Their ability to survive and reproduce is mostly dependent on abiotic factors such as temperature, pH, salinity, moisture, humidity, oxygen levels, etc. Organisms that are best adapted to the environmental conditions of that particular area are dominant while other organisms are dominant in other areas. ·

  • Statement 1 is correct: Based on temperature tolerance, different groups of organisms are defined. Among them, eurythermal and stenothermal animals are two categories. Eurythermal animals are able to tolerate a wide range of temperature levels. Stenothermal animals are those which can tolerate a narrow range of temperature levels.

  • Statement 2 is not correct: Eurythermal animals include cat, dog, man, goat, tiger, etc which are vertebrates (as they have a backbone and a spinal column). Thus vertebrates can be eurythermal. Although stenothermal animals include a penguin, python, crocodile, some aquatic insects survive in a narrow range of temperature, usually cool water (cold stenotherms). Insects are not vertebrates (as they lack a backbone and a spinal column). Thus all stenothermal organisms are not necessarily vertebrates.

  • A few organisms can tolerate and thrive in a wide range of temperatures - eurythermal, but, a vast majority of them are restricted to a narrow range of temperatures - stenothermal.

QUESTION: 23

Which of the following are non-point sources of pollution in rivers?

  1. Surface drains carrying municipal sewage

  2. Run-off from agricultural fields

  3. Dumping of un-burnt/half-burnt dead bodies

  4. Dhobi ghats

  5. Effluents from industries

Select the correct answer using the code given below.

Solution:
  • Point sources: These are organized sources of pollution where the pollution load can be measured, e.g. surface drains carrying municipal sewage or industrial effluents, sewage pumping stations and sewerage systems, trade effluents from industries, etc. Pollution loads due to untreated sewage is one of the main reasons threatening the ecological health of rivers. Most of the urban lakes in the country are also facing similar challenges.

  • Non-point sources: These are non-measurable sources of pollution such as run-off from agricultural fields carrying chemicals and fertilizers, run-off from solid waste dumps and areas used for open defecation, dumping of un-burnt/half-burnt dead bodies and animal carcasses, dhobi ghats, cattle wallowing, etc.

  • Out of the total measurable pollution in the rivers from various point sources, around 75% is contribut ed by municipal sewage from towns located along the banks of rivers and remaining 25% by industrial effluents.

QUESTION: 24

Rain-soaked Meghalaya forests, deep ocean trenches, torrential streams and boiling thermal springs are examples of:

Solution:
  • A biome is an area of the planet that can be classified according to the plants and animals that live in it. Temperature, soil, and the amount of light and water help determine what life exists in a biome. ·

  • Not all scientists classify biomes in the same way. Some use broad classifications and count as few as six biomes. These are forest, grassland, freshwater, marine, desert, and tundra.

  • Other scientists use more precise classifications and list dozens of different biomes. For example, they consider different kinds of forests to be different biomes. Tropical rain forests that are warm and wet year round are one biome. Temperate deciduous forests—those that have cold winters, warm summers, and are dominated by trees that lose their leaves—are a different biome. Taiga forests, which are in cold regions and are dominated by cone-bearing firs and spruces, are yet another biome.

  • Regional and local variations within each biome lead to the formation of a wide variety of habitats. Life exists not just in a few favourable habitats but even in extreme and harsh habitats -scorching Rajasthan desert, rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, permafrost polar regions, high mountain tops, boiling thermal springs, and stinking compost pits. Even our intestine is a unique habitat for hundreds of species of microbes. Hence, option (d) is the correct answer.

  • Biogeographic realms

    • These are large spatial regions within which ecosystems share a broadly similar biological evolutionary history .Eight terrestrial biogeographic realms are typically recognized, corresponding roughly to continents - Australasian, Afrotropical, Nearctic, Oceanic, Antarctic, Indo-Malayan, Neotropical, Palearctic.

    • Population refers to the organisms of the same species that are in proximity to one another. For e.g. a group of rabbits.

    • Ecotones- Ecotone, a transitional area of vegetation between two different plant communities, such as forest and grassland. It has some of the characteristics of each bordering biological community and often contains species not found in the overlapping communities. An ecotone may exist along a broad belt or in a small pocket, such as a forest clearing, where two local communities blend together. The influence of the two bordering communities on each other is known as the edge effect.

QUESTION: 25

Communities rich in species diversity are considered as stable communities. Which of the following is/are features of stable communities?

  1. High variation in productivity from year to year.

  2. Resistance to occasional anthropogenic disturbances.

  3. Resistance to invasion by alien species Select the correct answer using the code given below.

Solution:
  • George David Tilman is an American ecologist. It is said that a stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species. Hence statements 2 and 3 are correct and 1 is not correct.

  • David Tilman‘s long term ecosystem experiments using outdoor plots show how these attributes are linked to species richness in a community. Tilman found that plots with more species showed less year-to year variation in total biomass. He also showed that in his experiments, increased diversity contributed to higher productivity.