Bihar Board 12th Biology Important Questions Short Answer Type Part 6

Bihar Board 12th Biology Important Questions Short Answer Type Part 6 are the best resource for students which helps in revision.

Bihar Board 12th Biology Important Questions Short Answer Type Part 6

Question 1.
What are the features of wild plants which are selected by man for his benefit?
Wild plants grow rapidly and produce a crop within a season, and wild plants store enough food reserves in their seeds to survive through drought.

Question 2.
What is plant introduction?
When a plant species is carried from its place of origin to a new place and cultivated, it is termed as plant introduction. It is an important method for crop improvement.

Question 3.
What is meristem culture?
Use of explant that contains pre-existing shoot meristems and produce shoots from them when cultured on a medium. Such a culture is called meristem culture.

Question 4.
What is callus?
An unorganised mass of cells is called callus. It is usually produced by culturing explant in tissue culture laboratories. A superficial tissue developing in woody plants, usually through cambial activity, in response to wounding is also called callus. This tissue develops for protecting the injured surface.

Question 5.
Who coined the term totipotency? What does it means?
German botanist Gottlieb Haberlandt 1902 coined the term totopotency. Totipotency is the ability or capability of a cell to give rise to a complete organism, when cultured in a suitable culture medium at appropriate temperature and aeration conditions.

Question 6.
What are somatic hybrids? What are their common uses?
Somatic hybrids are produced by fusion of somatic cells of two varieties of species. They are produced by somatic hybridisation. The cell walls of plant cells are removed by digestion with a combination of pectinase and cellulase. The naked protoplasts of two ceils are induced to fuse by a solution of polyethylene glycol (PEG) and a brief high voltage current. Such protoplasts when transferred to suitable culture medium, develop cell walls and begin to divide. These are used for gene transfer, transfer of cytoplasm and production of allopolyploids.

Question 7.
What are dedifferentiation and redifferentiation?

  1. Transformation of mature cells into meristematic cells leading to the formation of callus is called dedifferentiation.
  2. Development of entire plants from the components cells of callus is called redifferentiation.

Question 8.
Discuss the role of plant tissue culture in increasing food production.
Plant tissue culture plays various roles in increasing food production as:

  • The callus culture and suspension culture is used to get cell biomass production.
  • It may be used for biochemical isolation.
  • It is used to regenerate plantlets.
  • It is used for the production of transgenic plants.
  • It is used for isolation of protoplasts.

Question 9.
Elaborate as to how biotechnology can be helpful in achieving sustainable agriculture.
Biotechnology can be helpful in achieving sustainable agriculture through the use of biofertilizers, biopesticides, disease resistant and insect resistant varieties. Microorganisms are used to prepare butter, yogurt, cheese, idlis, dosa etc. Single cell protein (SCP) can be produced from algae, bacteria, microbes etc. It is done in yeasts. It provides a valuable protein rich supplement in human diet. Microbes are employed to enhance the availability of nutrients to crops.

Question 10.
‘Biotechnology can greatly promote human welfare, but it can also be misused to increase human sufferings.’ Comment on the statement.
Biotechnology is the wise use of organisms for human welfare. It can be misused in many ways:

  • Biopotenting may cause problem to one country.
  • Biopiracy – developing countries may be misused by exploiting bioresources.
  • Bioweapons – may be fatal to use.
  • Transgene – its introduction may violate the integrity of a species.

Question 11.
Give a schematic representation of plant breeding.
Bihar Board 12th Biology Important Questions Short Answer Type Part 6, 1

Question 12.
Write a note on heterosis.
Heterosis is the reverse of inbreeding depression. When two unrelated individuals or lines are crossed, the performance of F1 hybrid is often superior to both its parents.
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Fig.: Meaning of heterosis. When phenotype of F1 falls within range of parental values it represents dominance. Only when F1 phenotype falls outside (on either side) of the parental range, it constitutes heterosis.

Question 13.
A farmer adds Azotobacter culture to the soil before sowing maize. How does it increases the yield of maize?
Azotobacter is a free-living nitrogen fixing bacteria. It fixes atmospheric nitrogen in the soil and increases the fertility of soil. Maize plants cultivated in fertile soil result in increased yield.

Question 14.
What are mutations?
Mutation is a sudden and heritable change in a character of an organism. It may arise due to a change in (i) chromosome structure, (ii) chromosome number, (iii) base sequence of the concerned gene. Mostly mutations are non-expressive. These may be spontaneous (natural) or induced by mutagens like physical mutagens (X-rays, gamma rays, etc.), chemical (EMS., sodium azide etc.)

Mutation, breeding is used in plant breeding to develop improved varieties.

Question 15.
What is the difference between conventional agriculture practices and modern agriculture practices?
Conventional agriculture practice includes the use of locally available good quality seeds, compost, manure and biofertilizers, this was more ecofriendly. Modern agricultural practices are causing ecological damage due to enormous exploitation of natural resources and un-manageable amount of byproducts and wastes, which are continuously polluting the atmosphere.

Question 16.
Insulin is extracted from which micro-organism?
Insulin producing genes from human beings have been introduced into bacteria E. Coli, E. Coli produces insulin which is known as humulin.

Question 17.
Name a water fern that is an excellent biofertilizer for rice cultivation. What helps the fern to do so?
Azolla – Anabaena symbiosis is a cyanobacterial biofertilizer, for rice cultivation. It fixes atmospheric nitrogen which is consumed by growing rice crops.

Question 18.
What is Integrated Pest Management?
Integrated Pest Management is an important step taken by government which involves the harmovious application of various ‘Cultural controls’ to insure environmental pollution and proper maintenance of ecological balance.

Question 19.
Differentiate between manure and biofertilizers.

Manure Biofertilizer
1. Manures represent the partially decayed wastes and are added to soil. 1. Biofertilizers include the organisms which enrich the soil nutrients due to their biological activity.
2. They increase the fertility aeration and water holding capacity of soil. 2. They may or may not contribute in maintaining the form of soil.
3. Green manures add many kinds of nutrient elements used by crops. Chemical fertilizers are required to be added to soil. 3. One or few nutrients are made available to crops by biofertilizers. They add to the fertility of soil and reduce the demand of chemical fertilizers.

Question 20.
Write a note on Mycorrhiza.
Mycorrhiza are symbiotic association between fungus and roots of higher plants. It is of two types: Ectomycorrhiza and Endomycorrliza.
1. Ectomycorrhiza – Here, fungal mycelia form mantle on root surface. From the mantle, fungal hyphae penetrate into cortex of root as well as into the soil. This leads to increase in surface area for absorption of water and minerals (N, P and K). Fungal hyphae in soil further solubilise some insoluble organic compounds which are easily absorbed by plants. Ectomycorrhizae have been found in oaks, pines, Fagus and Eucalyptus.

2. Endomycorrhiza – Here, fungus does not form a mantle on root surface, instead it produces loosely interwoven hyphae. Some of these mycelia penetrate into soil still others enter into cortex of root.

Question 21.
What is the biological significance of ectomycorrhizae in peach orchards?
The ectomycorrhizae has following functions in peach orchards:

  • Absorption of water
  • Solubilisation of complex organic molecules into simple inorganic nutrients
  • Protection of plants from attack of disease causing pathogens, etc.

Question 22.
Write two main drawbacks of using chemical weedicides? What are Bioherbicides?
Herbicides are those chemicals which are used to control the weeds (unwanted plants in crop fields).
Drawbacks of use of chemical weedicides:

  • Improper use of herbicides may damage the crops.
  • They encourage the growth of resistant weeds.

Bioherbicide involves the biological control of Weeds by some living organisms. It involves the use of insects feeding on a specific weed or use of certain micro-organisms which will cause disease in weeds.

Question 23.
How is Lactic acid produced? Write down its uses.
Lactic acid – It was the first organic acid to be produced from microbial fermentation of lactose (milk sugar). Fermenting agents are bacteria (e.g. Streptococcus lactis and Lactobacillus species) and fungi (e.g. Rhizopus). The acid derived from fungal sources is costlier but is of high purity.
Bihar Board 12th Biology Important Questions Short Answer Type Part 6, 3

Uses: Lactic acid is used in confectionery, fruit juices, essence, pickles, canned vegetables and fish products. It is also employed as mordant in tanning, printing of wool, plastic and pharmaceuticals.

Question 24.
Write the fermentation reactions for the production of alcohol.
Bihar Board 12th Biology Important Questions Short Answer Type Part 6, 4

Question 25.
Why are leguminous plants cultivated as green manure crop?
Leguminous plants possess root nodules where atmospheric nitrogen is fixed by symbiotic bacteria – Rhizobium. The fixed nitrogen fertilizes the soil. Moreover, the green plants provide manure by their death and decay.

Question 26.
How can age-sex structure of a population be deficted in a pyramid diagram?
The age structure of a given population refers to the proportion of individuals of different ages within that population. Many functional aspects of the individuals are related to age. For example, infants, below one year of age, and older people have higher mortality rates than individuals of other ages. In addition, the proportion of reproductively active males and females in a population influences the population growth. The number of female individuals in active reproductive age (usually 15 – 44 years) influences the birth rates within a population.

Age-sex structure of a population can be depicted in the form of a pyramid diagram by plotting the percentage of population of each sex in each age class.

The age-sex structure of the developed world gives a steeper pyramid, which represents a nearly stable population. A rapidly growing population, like that of India, is represented by a much less steep pyramid.

The population planning policies have succeeded only marginally.

Question 27.
Briefly outline the reasons for human population explosion.
Population explosion refers to increase in human population at an alarming rate.
It is because:

  • Agricultural production has increased and starvation deaths have declined.
  • Medical services have brought down mortality due to fatal diseases and epidemics.

Question 28.
Why is increasing food production considered only a temporary solution for a growing population?
Malthus had stated that “Population, when unchecked increases in geometrical ratio, while the food supply at the best increase in an arithmetical ratio, hence population tends to increase upto the limits of means of subsistence”. Advances in biotechnology has led to increase in food production but it is considered as temporary solution because the environment can support population upto a certain limit. If the current trend of growth counting, the other available natural resources will become too meagre to meet the needs. This will lead to number of socio-economic problems.

Question 29.
What do evolutionary biologists believe that the ‘success’ of mammals is largely due to their ability to maintain a constant body temperature and thrive whether they live in Antarctica or in the Sahara desert?
The mechanism used by most mammals to regulate their body temperature are similar to the ones that humans use. Human being maintain a constant body temperature of 37°C. In summer, when outside temperature is more than our body temperature, we sweat profusely. The resulting evaporate cooling, similar to what happens with a desert cooler in operation, brings down the body temperature. In winter when the temperature is much lower than 37°C, we start to shiver, a kind of exercise which produces heat and raises the body temperature.

Question 30.
Why is temperature regarded as the most ecologically relevant enviromental factor?
The average temperature on land varies seasonally, decreases progressively from the equator towards the poles and from plains to the mountain tops. It ranges from subzero levels in polar areas and high altitude to > 50°C in tropical deserts in summer. Where average temperature exceed 100°C there are unique habitats such as thermal springs and deep-sea hydrothermal vents. Due to this variation in temperature mango trees cannot grow in temperature countries like Canada and Germany and snow leopards are not found in Kerala.

Question 31.
Name the major biomes of India.
Major biomes of India:

  1. Tropical rain forests
  2. Deciduous forests
  3. Desert
  4. Seacoast

Question 32.
What are the key elements that lead to variation in the physical and chemical conditions of different habitats?
The most important key elements are temperature, water, light and % soil. However, the physico-chemical (abiotic) components alone do not characterise the habitat of an organism completely; the habitat includes biotic components also – pathogens, parasites, predators and competitors of the organisms with which they interact constantly.

Question 33.
Explain in brief the importance of light
Plants produce through photosynthesis, which is possible only when sunlight is available as a source of energy. Many species of small plants, growing in forests are adopted to photosynthesis optionally under very low conditions because they are constantly overshadowed by tall, canopied trees. Many plants are also dependent on sunlight to meet their photoperiodic requirement for flowering. The availability of light on land is closely linked with that of temperature since the sun is the source for both.

Question 34.
What will happen if the predator is too efficient and over exploits its prey?
If a predator is too efficient and over-exploits its prey, then the prey might become extinct and following it, the predator will also become extinct for lack of food.

Question 35.
Why it is difficult to draw sharp boundaries between ecosystems?
The different ecosystems do not have sharp boundaries between them. There are present transitional zones, between the adjacent ecosystems. These are called ecotones, these harbour some organisms from each of the adjacent ecosystems and some peculiar to themselves.

Question 36.
In the following table of interspecific interactions, fill the blanks with ‘+’ sign for beneficient interaction, ‘-‘sign for detrimental and 0 for neutral interaction.
Bihar Board 12th Biology Important Questions Short Answer Type Part 6, 5
Bihar Board 12th Biology Important Questions Short Answer Type Part 6, 6

Question 37.
What is an ecosystem? How material and energy transformation occurs in an ecosystem?
An ecosystem is a structural and functional unit of the biosphere which consists of living organisms and their non-living environment.
Bihar Board 12th Biology Important Questions Short Answer Type Part 6, 7

Question 38.
Differentiate between Autotrophs and Heterotrophs.

  1. Prepare their organic nutrients themselves.
  2. Get inorganic materials from outside.
  3. Obtain energy from sunlight or inorganic chemical reactions.
  4. Usually add O2 to the environment.
  5. Are of 2 types : photoautotrophs and chemoautotrophs.
  6. They are producer organisms.
  7. Include plants, some protists and certain bacteria.


  1. Do not prepare organic nutrients themselves.
  2. Get both organic and inorganic materials from outside.
  3. Obtain energy from organic nutrients.
  4. Add CO2 to the environment.
  5. Are of 2 types : phagotrophs and saprotrophs.
  6. They are consumer organisms.
  7. Include animals, many protists and bacteria and bacteria and fungi of decay.

Question 39.
What are special consumers? Give a brief account?
Special consumers are organisms which have special mode of food intake. These may include parasites, double consumers, both producers and consumers and scavengers.

  • Parasites like bacteria, protists and animals may be considered as secondary consumers or some higher order consumers.
  • Double consumers like ants, bear, man. These are omnivores. They belong to more than one category for e.g. man is a primary consumer when vegetarian and a secondary consumer when non-vegetarian.
  • Both producers and consumers, there are insectivores plants which are producers and secondary consumers.
  • Scavengers or detrivores are animals which feed on decaying organic matter or dead organisms like earthworms, termites, vultures etc.

Question 40.
What is the significance of decomposers?
The decomposers are bacteria and fungi who obtain their food from organic molecules of dead producers and consumers and their waste products. The decomposers play an important role of returning the chemical nutrients to the environment. They also make space for the new producers by consuming the dead and decaying matter, otherwise all the nutrients would remain locked in the dead remains of plants and animals and will not be available for recreation.

Question 41.
Draw a scheme to show decomposition of detritus.
Dead remains of plants and animals are called detritus. The decomposition of detritus is a complex and enzymatic process, that involves step-wise degradation.
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Question 42.
With the help of a generalised scheme show how the biotic components of an ecosystem are related.
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Question 43.
What is a food web? Give example.
Food web is a network of food chains which become interconnected at various trophic levels to form a number of feeding connections among different organisms of a biotic community. Food webs provide stability to the ecosystem.
For example food web in a pond.
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Question 44.
What is a food chain? Enlist its important characters.
The sequential inter-linking of organisms involving the transfer of food energy from the producers, through a series of organisms is known as a food chain. Its main characteristics are:

  1. In food chain there occurs repeated eating and it involves nutritive interaction between the living organisms
  2. It is always straight
  3. It has undirectional flow of energy
  4. It usually contains 4 to 5 trophic levels
  5. Mostly 80 – 90% of energy is lost as heat.

Question 45.
What is photosynthetic efficiency, net production efficiency, Assimilation efficiency and ecological efficiency?
(1) Photosynthetic efficiency – It is the percentage ratio between gross primary productivity and incident total solar radiation. It generally varies from 1 to 5 percent.
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(2) Net production efficiency – It is the percentage ratio between net primary productivity and gross primary productivity. It is around 50%.
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Important efficiency measures for consumers include:
(1) Assimilation efficiency – It is the percentage ratio between food energy assimilated and food energy ingested at one trophic level.
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(2) Ecological efficiency – It is the percentage ratio between energy in biomass production at one trophic level and energy in biomass production at previous trophic level. It is also called trophic level efficiency.
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Question 46.
Differentiate between Gaseous cycles and Sedimentary cycles.

Gaseous Cycles Sedimentary Cycles
1. Pertain to gases (C2, N2, O2). 1. Pertain to minerals (Ca, P, S, K, Mg.)
2. Have reservoir pool in air or water. 2. Have reservoir pool in rocks.
3. Occur quickly and take less time to complete. 3. Occur very slowly and take a long time to complete.
4. Are relatively perfect systems as the elements remain uniformly in circulation. 4. Are less perfect systems as the elements get locked in reservoir pool for long periods.

Question 47.
Industries can cause rise and fall in the temperature of biosphere. How?
Industries add CO2 and particulate matter to the air. The CO2 acts as a greenhouse gas and increases the temperature of the air, whereas the particulate matter decreases the amount of sunlight reaching the earth and reduces the temperature on earth.