{"id":18359,"date":"2019-12-06T10:45:58","date_gmt":"2019-12-06T05:15:58","guid":{"rendered":"https:\/\/www.cbselabs.com\/?p=18359"},"modified":"2021-09-18T15:15:47","modified_gmt":"2021-09-18T09:45:47","slug":"important-questions-for-class-12-biology-cbse-organisms-and-its-environment","status":"publish","type":"post","link":"https:\/\/www.cbselabs.com\/important-questions-for-class-12-biology-cbse-organisms-and-its-environment\/","title":{"rendered":"Important Questions for CBSE Class 12 Biology Organisms and Its Environment"},"content":{"rendered":"
1.Ecology<\/strong> is the branch of biology, which studies the interactions among organisms\u00a0and their physical (abiotic) environment.<\/p>\n 2.<\/strong>The subject ecology is basically concerned with four levels of biological organisation. 3.Environment<\/strong> Ecology at organism level deals with how different organisms are adapted to their environment in terms of their survival and reproduction. The major biomes of the world are desert, grassland, rainforest and tundra. 4.<\/strong>Major abiotic factors are: Euiythennal<\/strong> These can tolerate a wide range of temperature. Euryhaline<\/strong> Organisms, which can tolerate a narrow range of salinity. (iii)Light<\/strong> is an essential factor for the process of photosynthesis performed by autotrophs.<\/p>\n (iv)Soil The nature and properties of soil vary from place to place. It depends on climate, weathering process and whether soil is transported or sedimentary and how its development occurred.<\/p>\n 5.Responses to abiotic factors<\/strong> determines how organisms can cope or manage with stressful conditions of the habitat. Conform<\/strong><\/p>\n Migrate<\/strong> Suspend<\/strong><\/p>\n <\/p>\n 6.Adaptation<\/strong> is any attribute of an organism, i.e. morphological, physiological or behavioural, that enables the organism to survive and reproduce in its habitat. Many adaptations have evolved over a long evolutionary time and are genetically fixed. (ii)Adaptations in desert plants<\/strong><\/p>\n (iii)Adaptations in mammals<\/strong><\/p>\n (iv)Adaptations at high altitudes in humans (v) Adaptations in desert lizards (Behavioural response)<\/p>\n 1.Give an example of an organism that enters ‘diapause’ and why?[Delhi 2014]<\/strong> 2.Mention how do bears escape from stressful time in winter. [Delhi 2013c]<\/strong> 3.Write the basis on which an organism occupies a space in its community\/natural surroundings.<\/strong>[All India 2013]<\/strong> 4.Why are some organisms called as\u00a0eurythermals and some other as stenohaline? [Foreign 2011]<\/strong> 5.Why are green plants not found\u00a0beyond a certain depth in the ocean? [HOTS; Delhi 2011]<\/strong> 6.Mention any two activities of\u00a0animals, which get cues from diurnal and seasonal variations in light intensity, [Delhi 2011 c]<\/strong> 7.How do animals like fishs and snails\u00a0avoid summer related unfavourable conditions? [Delhi 2010]<\/strong> 8.How do prickles help cactus survive in desert? Give two methods.[All India 2010 C]<\/strong> 9.Which one of the two, stenothermals or eurythermals shows wide range of distribution on earth and why?[HOTS; Delhi 2008]<\/strong> 10.When and why do some animals like snails go into aestivation?[All India 2008]<\/strong> 11.Why is the polar region not a suitable habitat for tiny humming birds? [HOTS; All India 2008]<\/strong> 12.When and why do some animals go\u00a0into hibernation? \u00a0[Foreign 2008]<\/strong> 13.List any two physiological responses that help you to gradually get acclimatised to high altitudes when you go from the plains. [Delhi 2008 C]<\/strong> 14.Define homeostasis. [All India 2008 C]<\/strong> 15.When and why do some animals like frogs hibernate? [Delhi 2008]<\/strong> 16.Between amphibians and birds, which will be stable to cope with global warming? Give reason.<\/strong>[HOTS; All India 2008]<\/strong> 17.How do herbs and shrubs survive\u00a0under the shadow of big canopied trees in forests?\u00a0\u00a0 [Delhi 2008C]<\/strong> 18.Why many of the freshwater animals cannot live for long in seawater or vice versa?[HOTS; Delhi; All India 2008 C]<\/strong> 19.Some organisms suspend their metabolic activities to survive in unfavourable condition. Explain with the help of any four examples.[Delhi 2012]<\/strong> 20.Explain the response of all\u00a0communities to environment over time.\u00a0 [All India 2011]<\/strong> 21.Bear hibernates, whereas some species of zooplanktons enter diapause to avoid stressful external conditions. How are these two ways different from each other?[Foreign 2011]<\/strong> 22.How does our body adapt to low oxygen availability at high altitudes?[Foreign 2011]<\/strong> 23.Why are small animals rarely found in the polar regions? Explain.[HOTS; Foreign 2010]<\/strong> 24.How do seals adapt to their natural\u00a0habitat? Explain. \u00a0[Foreign 2010]<\/strong> 25.Humming birds v<\/sub> live among the\u00a0bushes in tropics, while penguins live on icebergs. They cannot survive if their habitats are reversed. Justify. \u00a0 \u00a0[HOTS; Delhi 2010 C]<\/strong> 26.How does human body maintain constant temperature both in summers and winters? Explain.<\/strong>[Delhi 2009 C]<\/strong> 27.(i)State how the constant internal\u00a0environment is beneficial to organisms.<\/strong> 28.Water is very essential for life. Write any three features both for plants and animals which enable them to survive in water scarce environment,<\/strong> 29.How do organisms like fungi, zooplanktons and bears overcome the temporary short-lived climatic stressful conditions? Explain.[All India 2010; Delhi 2008]<\/strong> 30.The following graph represents the organismic response to certain environmental condition (e.g. temperature)<\/strong> 31.(i) Explain giving reasons why the\u00a0tourists visiting Rohtang Pass or Mansarovar are advised to resume normal active life only after a few days of reaching there.<\/strong> 32.list the different ways by which\u00a0organisms cope or manage with abiotic stresses in nature. Explain any three ways.\u00a0\u00a0\u00a0\u00a0 [All India 2009c]<\/strong> (ii) Conformating Organisms that cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. Such animals are called conformers. For example, small animals have larger surface area relative to their volume. They lose body heat very fast in low temperature. So, they expend energy to generate body heat through metabolism for adjusting. 33.(i) List any four abiotic components\u00a0that lead to variations in the physical and chemical conditions of habitats.<\/strong> Organisms and Populations Important Questions for CBSE Class 12 Biology Organisms and Its Environment 1.Ecology is the branch of biology, which studies the interactions among organisms\u00a0and their physical (abiotic) environment. 2.The subject ecology is basically concerned with four levels of biological organisation. These are given below: (i)Organism Living component of the environment at individual level …<\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[2],"tags":[],"yoast_head":"\n
\nThese are given below:
\n(i)Organism<\/strong> Living component of the environment at individual level and is basic unit of ecological hierarchy.
\n(ii)Population<\/strong> The sum total of all individuals of a species in a specific geographical area.
\n(iii)Communities<\/strong> Assemblage of all the populations of different species present in an area that interact among themselves.
\n(iv)Biome<\/strong> It is a large unit, which consists of a major vegetation type, associated fauna in a particular climatic zone. Tropical rainforest, deciduous forest, sea coast, deserts, etc., are the major biomes of India.
\nNOTE<\/strong> Other important terms used in ecology are:
\nEcosystem<\/strong> Represents, the organisms and their environment in a particular area.
\nHabitat<\/strong> It refers to a specific place or locality delimited by a combination of factors, physical features and barriers where a community dwells.
\nNiche<\/strong> The ecological niche of an organism represents the physical space occupied by it, the resources it utilises and its functional role in the ecological system.
\nBiosphere<\/strong> The surface of earth with all life forms, i.e. union of all ecosystems. It is a highly ordered system.<\/p>\n
\n(i)Different biomes are formed due to:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 .<\/p>\n\n
\n
\n(ii)Regional and local variations within each biome lead to the formation of a wide variety of habitats.
\n(iii) Life on earth exists in favourable habitats as well as in extreme and harsh habitats like 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 and even in our intestine.
\n(iv) The biotic components of a habitat are pathogens, parasites, predators and competitors of the organism with which they interact constantly.
\n(v)The key abiotic elements that lead to variations in habitats are:
\n(a)Temperature \u00a0(b) Water
\n(c)Light \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0(d) Soil.<\/p>\n
\n(i)Temperature<\/strong> is the major abiotic factor, which is most ecologically relevant.<\/p>\n\n
\nStenothermal<\/strong> These can tolerate a narrow range of temperature
\n(ii)Water<\/strong> is the next major important factor without which life cannot exist.<\/p>\n\n
\nStenohaline<\/strong> Organisms, which can tolerate a narrow range of salinity.<\/p>\n\n
\n
\n
\n(i)During the course of millions of years of their existence, many species would have evolved a relatively constant internal (within the body) environment that permits all biochemical reactions and physiological functions to proceed with maximal efficiency and thus, enhance the overall fitness of the species.
\n(ii)The organisms should try to maintain the constancy of its internal environment,i.e.homeostasis, despite of varying external environmental conditions that tend to upset its homeostasis.
\n(iii)Human beings can maintain their homeostasis by using artificial means
\n(air conditioner in summer and heater in winter).
\n(iv)Ways by which other organisms can cope up with environmental changes are\u00a0given below:
\nRegulate<\/strong><\/p>\n\n
\n
\n
\nIt is the temporary movement from a stressful habitat to a more hospitable area and
\nreturn, when the stressful period is over.<\/p>\n\n
\n
\n
\nSome examples of adaptations are:
\n(i)Adaptations in kangaroo rat<\/strong><\/p>\n\n
\n
\n
\n(a)At high altitude places like Rohtang Pass near Manali (> 3500 m) and Mansarovar, in China occupied Tibet, people suffer from altitude sickness.
\n(b)Its symptoms are nausea, fatigue and heart palpitations.
\n(c)This is because at low atmospheric pressure of high altitudes, body does not get enough oxygen.
\n(d)The relief occurs gradually due to acclimatisation.
\n(e)The body cope up with this low oxygen stress by<\/p>\n\n
\n
Previous Year\u00a0Examination Questions<\/strong><\/span><\/h3>\n
1 Mark Questions<\/strong><\/span><\/h3>\n
\nAns<\/strong>.Many zooplanktons in lakes and ponds\u00a0enter diapause. They enter diapause to escape unfavourable environmental conditions and to delay the overall development.<\/p>\n
\nAns.<\/strong>Bears escape from stressful time in winter\u00a0by going into hibernation<\/p>\n
\nAns.<\/strong>An organism occupies individual or species\u00a0level in its community. This level is occupied on the basis of ecological level of organisation or ecological hierarchy. Individual-> Population -> Biotic community -> Biome<\/p>\n
\nAns<\/strong>.Organisms, which can tolerate and thrive\u00a0in a wide range of temperatures are called as eurythermal while organisms, which can tolerate and thrive in a narrow range of salinities are stenohaline<\/p>\n
\nAns<\/strong>.Beyond a certain depth, green plants are\u00a0not found, because light is unavailable in that zone.<\/p>\n
\nAns<\/strong>.The two activities of animals which get cues from diurnal and seasonal variations in light intensity are:
\n(i) Timing their foraging
\n(ii) Migratory activities
\n(iii) Reproduction (any two)<\/p>\n
\nAns.<\/strong>Fish migrate and snails go into aestivation\u00a0or summer sleep to avoid summer-related problems.<\/p>\n
\nAns<\/strong>.The two methods by which prickles help cactus survive in desert are:
\n(i) By reducing and altering outer surface to reduce evaporation of water.
\n(ii) By providing defense against grazing animals.<\/p>\n
\nAns<\/strong>.Eurythermals show a wide range of distribution on earth, as they can tolerate and thrive in a wide range of temperatures<\/p>\n
\nAns.<\/strong>During stressful conditions of the habitat and\u00a0inability to migrate, animals like snails undergo aestivation and protect themselves<\/p>\n
\nAns.<\/strong>Humming birds have a larger surface area\u00a0compared to body volume. They tend to lose body heat very fast, when it is cold outside. Due to this, they need to spend more energy to generate body heat. Hence, polar region being a cold habitat is not suitable for tiny hummingbirds<\/p>\n
\nAns.<\/strong>When unfavourable conditions are for a short\u00a0time and if the animals could not migrate, they undergo hibernation to avoid stressful winter conditions.<\/p>\n
\nAns<\/strong>.The physiological condition or responses in order to get accl imatised to high attitudes are:
\n(i) To compensate low oxygen, the production\u00a0of red blood cells is increased.
\n(ii) High haemoglobin content and its decreased binding capacity.
\n(iii) Faster breathing rate (any two).<\/p>\n
\nAns.<\/strong>The process to maintain the constancy of\u00a0internal environment of the body, despite varying external environmental conditions is called homeostasis<\/p>\n
\nAns.<\/strong>When unfavourable conditions are for a short\u00a0time period and animals are unable to migrate, they hibernate to avoid the stres winter.<\/p>\n
\nAns<\/strong>.Birds will be stable to cope with global warming because they can tolerate a wide range of temperatures (eurythermals).<\/p>\n
\nAns.<\/strong>The herbs and shrubs are adapted to perform\u00a0photosynthesis optimally under very low light conditions due to growing in the forests under the shadow’ of big canopied trees<\/p>\n
\nAns<\/strong>.Seawater contains high quantity of salt that is\u00a0not favourable for freshwater animals. They face osmotic problems, hence they cannot survive in seawater for long.<\/p>\n2 Marks Questions<\/span><\/strong><\/h3>\n
\nAns.<\/strong>Examples of organisms that suspend their metabolic activities in unfavourable condition.
\n(i) Bacteria, fungi and lower plants They form thick-walled spores, which help them to survive in unfavourable conditions. Spores germinate on \u00a0return of favourable conditions.
\n(ii) Higher plants Seeds and some other vegetative reproductive structures serve as means to tide over periods of stress. They reduce their metabolic activity and undergo dormancy.
\n(iii) Animals They undergo hibernation or aestivation, if unable to migrate. For example, some snails and fishes.
\n(iv) Zooplanktons They enter diapause (suspended development) under unfavourable conditions.<\/p>\n
\nAns<\/strong>.Response of communities to environment:
\n(i) Some organisms maintain homeostasis by physiological or behavioural means (regulate).
\n(ii)The internal environment in majority of animals and nearly all plants change with the change of external environment (conform).
\n(iii)Some organisms leave their habitats temporarily during unfavourable conditions and return back when conditions become favourable (migrate).
\n(iv)Some organisms suspend their\u00a0metabolic activities to avoid stress by timely escaping, e.g. hibernation and aestivation.<\/p>\n
\nAns<\/strong>.Difference between diapause and hibernation:
\n<\/p>\n
\nAns.<\/strong>Body adaptations at high altitudes are:
\nThe physiological condition or responses in order to get accl imatised to high attitudes are:
\n(i) To compensate low oxygen, the production\u00a0of red blood cells is increased.
\n(ii) High haemoglobin content and its decreased binding capacity.
\n(iii) Faster breathing rate (any two).<\/p>\n
\nAns<\/strong>.Small animals have a large surface area\u00a0relative to their volume. So, they tend to lose body heat very fast during cold conditions. They need to spend more energy to generate body heat. Due to this smaller animals are rarely found in polar regions.<\/p>\n
\nAns<\/strong>.Seals adapt to the natural habitat\u00a0(cold climate) by developing a thick layer of fat (blubber) below their skin that acts as an insulator and reduce excess loss of body heat.<\/p>\n
\nAns<\/strong>.Humming birds are natural habitats of\u00a0tropics. They have large surface area relative to their volume. So, they tend to lose heat very fast, even when it is cold outside.Penguins live on icebergs (natural habitat). They have less surface area to volume ratio. The lesser the ratio, more effective will be the thermoregulation. Also, they hide in group to escape from cold conditions. Therefore, both of them will not survive if their habitats are reversed<\/p>\n
\nAns<\/strong>.Human body maintains constant body temperature (37\u00b0C) as follows:
\nIn summers,<\/strong> the outside temperature is very high than our body temperature. Due to this, profuse sweating occurs. This causes evaporation and cooling effect on the body.
\nIn winters<\/strong>, the outside temperature is much lower than our body temperature. This causes shivering, a kind of exercise that produces heat and raises the body temperature.<\/p>\n3 Marks Questions<\/span><\/strong><\/h3>\n
\n (ii)Explain any two alternatives by which orgnaisms can overcome stressful external conditions.<\/strong>[All India 2014]<\/strong>
\nAns<\/strong>.(i)Constant internal environment is\u00a0beneficial to organisms as it permits all biochemical reactions and physiological functions to proceed with maximal efficiency, thereby enhancing the overall efficiency of organism.
\n(ii) The two alternatives by which organisms can overcome stressful external conditions are<\/p>\n\n
\n or<\/strong>
\n How do organisms cope with stressful external environmental conditions which are localised or of short duration? \u00a0 [ah India 2011]<\/strong>
\nAns.Adaptation in plants<\/strong>
\n(i) Thick cuticle on their leaf surface.
\n(ii) Stomata are arranged in deep pits (sunken) to minimise water loss through transpiration.
\n(iii) Leaves are reduced to spines. The\u00a0photosynthetic function is carried out by thick, fleshy flattened stems.
\nAdaptation in animals<\/strong>
\n(i) Kangaroo rat meets the water requirement through internal oxidation of\u00a0fat.\u00a0They concentrate their urine, so that minimum volume of water is excreted.
\n(ii) Snails undergo aestivation during\u00a0summers.
\nOrganisms either migrate or suspend their metabolic activities when conditions are stressful for short duration.In such conditions, organisms are as follow:
\n(i) Moving away from stressful habitat to more favourable area and return to their habitat when stressful period is over. For example, birds from Siberia and other cold countries migrate to Bharatpur Sanctuary of Rajasthan.
\n(ii) Hibernating (frogs) or aestivating (snails) or undergo diapause (zooplanktons).
\n(iii) Thick-walled spores are formed in stressful conditions and germinate under suitable conditions, e.g. bacteria, fungi and lower groups of plants.<\/p>\n
\nAns.<\/strong>(i)Fungi They produce various kinds of\u00a0thick-walled spores to survive under unfavourable conditions, which germinate on return of favourable conditions.
\n(ii) Zooplanktons They enter diapause, a stage of suspended development under unfavourable conditions.
\n(iii)Bears They hibernate during winter to\u00a0escape the time of unfavourable\u00a0<\/span>conditions.<\/span><\/p>\n
\n <\/strong>
\n (i)Which one of these A or B depicts conformers?<\/strong>
\n (ii)What does the other line graph depict?<\/strong>
\n (iii)How do these organisms differ from each other with reference to homeostasis?<\/strong>
\n (iv)Mention the category to which\u00a0human belong. \u00a0 [All India 2009]<\/strong>
\nAns.<\/strong>(i)A depicts conformers.
\n(ii) The other line B depicts regulators.
\n(iii) Differences between conformer and regulator are:
\n
\n(iv) Humans are regulators.<\/p>\n5 Marks Questions<\/span><\/strong><\/h3>\n
\n (ii) It is impossible to find small animals in the polar regions. Give reasons.\u00a0\u00a0 [All India 2012]<\/strong>
\nAns.<\/strong>(i)Tourists visiting to Rohtang Pass near\u00a0Manali (> 3500 m) may suffer from altitude sickness. They resume normal active life only after a week because in low atmospheric pressure at high altitudes, the body does not get enough oxygen. Gradually, the body compensates low oxygen availability by
\n(a)Increasing red blood cell production.
\n(b)Decreasing the binding affinity of \u00a0haemoglobin.
\n(c)Increasing the breathing rate.
\n(ii)Small animals have a large surface area\u00a0relative to their volume. So, they tend to lose body heat very fast during cold conditions. They need to spend more energy to generate body heat. Due to this smaller animals are rarely found in polar regions.<\/p>\n
\nAns<\/strong>.Organisms cope up with abiotic stress by:
\n(i)Regulating Some organisms maintain\u00a0homeostasis by physiological and behavioural means. They are called regulators, e.g.<\/p>\n\n
\n(iii) Migrating The temporary movement of organisms from the stressful habitat to a\u00a0more hospitable area and return when favourable conditions reappear is called migration. The long distance migration is very common in birds.<\/p>\n
\n (ii) Explain the impact of these components on the distribution of organisms in different habitats.<\/strong>
\n [All India 2009 C]<\/strong>
\nAns<\/strong>.(i)Temperature, water, light and soil.
\n(ii) (a) Temperature influences the kinetics of enzymes and thereby the metabolism and other physiological functions of the organisms.
\nOrganisms may be eurythermal and can tolerate a wide range of temperature and stenothermal that can tolerate only a narrow range of temperature.
\n(b)Water is important to sustain life and productivity and distribution of plants is dependent on water.
\nFreshwater forms cannot thrive in sea water and vice versa.
\n(c)Light influences photosynthesis of plants. Light also influences the flowering in plants and timing of foraging, reproduction and migratory activities of animals.
\nAquatic plants occupy different depths depending on their pigments and the light available.
\n(d)Soil influences vegetation by the\u00a0water holding capacity, topography and its composition.
\nImportant Questions for Class 12 Biology<\/a>Class 12 Biology<\/a>NCERT Solutions Home Page<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"