Bihar Board 12th Biology Important Questions Short Answer Type Part 7

Bihar Board 12th Biology Important Questions Short Answer Type Part 7 are the best resource for students which helps in revision.

Bihar Board 12th Biology Important Questions Short Answer Type Part 7

Question 1.
Due to uncontrolled excessive hunting, the population of tigers in a forest becomes zero. Discuss the long-term effect of this situation on the population of deer in that forest.
In a forest ecosystem the food chain occurs like this:
Grass → Deer → Tiger
As a result of excessive hunting, the tiger population in a forest becomes zero. This will lead to an increase in the population of deer. Consequently, the amount of grass in the forest decreases. In long term, is such a situation exists it will be a decrease in deer population due to competition among deer for grass. Due to excessive grazing the forest may turn into a desert after a long time.

Question 2.
Why soil is rich in nutrients in the tropical rain forests?
Soil in tropical rain forests is rich in minerals and humus because the high temperature and moisture are favourable for the decomposition of fallen leaves and dead organic matter by the decomposers.

Question 3.
Define wild life. Write its significance in the maintenance of the environment.
The wild life refers to the naturally occurring species of animals and plants which are not domesticated or cultivated.


  • Wild life has links in food chains operating in nature. These food chains are extremely beneficial to us.
  • Wild life maintains a balance in nature. For example, snakes control rodent population which destroy our crops.
  • Wild life also performs the role of biological control. These help in the recycling of matter in nature.
  • Green plants purify air, they gives us oxygen also maintain atmospheric temperature.
  • Plants add water vapour by transpiration and influence rainfall.

Question 4.
How is diversity at all levels generally conserved?
Diversity is recognised by gene pool, species and biotic community. The ecosystem changes due to the pollution, climate changes and exploitation etc. There is need to prevent further destruction or degradation of habitats. There are on site (in situ) and off site (ex situ) strategies of conservation. Protected areas like biosphere reserves should be maintained.

Question 5.
What are threatened species? Name their 3 types in order of the danger of extinction they face.
Species likely to disappear sooner or later are threatened species. Their 3 types are:

  1. Endangered species: These species are facing danger of imminent extinction, due to abundance of predators, pathogen or pullulans, very few in number or reduction in habitat.
  2. Vulnerable species: Their abundant population is present but threatened to deplete in number due to some factors like DDT in bird population.
  3. Rare species: These are naturally present in small populations, they have risks from predators/pathogen or environmental factors.

Question 6.
What kind of threats to the biodiversity may lead to its loss?
Some important factors that lead to extinction of species and consequent loss of biodiversity are:

  • habitat loss and fragmentation
  • introduction of non-native species
  • over exploitation
  • soil, water and atmospheric pollution
  • intensive agriculture
  • forestry.

Habitat loss is the primary reason because if habitat is destroyed, then species would be destroyed (e.g. burning of forest, cutting of trees etc.) Pollution may eliminate some species. Eutrophication in lakes reduces biodiversity. Introduction of exotic species hinder the development of natural species, e.g. exotic fish Nile perch, water hyacinth and Lantana camara.

Question 7.
What do you understand by conservation of wildlife? What are its main objectives?
Wise use and preservation of natural resources is called ‘conservation of wild life. Its main objectives are:

  • To ensure utilization of species and ecosystems – All the endangered species of plants and animals should be preserved. National Parks and Sanctuaries should be set up for wildlife. Wildlife should be protected in zoological gardens.
  • Preservation of species diversity – If a particular species migrates from one area to another, arrangements should be made to set up that species in the other area.
  • Maintenance of life supporting systems – Unique ecosystem should be protected. National protection programmes should be linked with international programmes.

Question 8.
Give two main cases of extinction of species by human intervention.
Two main causes of extinction of a species are:
(i) By destroying their natural habitat. Many wild areas are being converted to human settlements, harbour, dams, reservoirs, croplands, mining sites etc. Environmental pollution and deforestation also results in the destruction of habitat, e.g., Habitat of largest flying bird (California Condor) of today has been affected by human cleanliness. Minor disturbances in the routes of migratory animals also affect them, i.e., some dams are blocking spawning.

(ii) Indiscriminate killing of the organism. Due to some properties of particular organisms, e.g., Rhinoceros is hunted for its horn, snakes are killed because of their venom and skin; Tigers, Lions, Leopards are killed on a large scale skin; Tigers, Lions, Leopards are killed on a large scale because of their skin and demand of some plants because of its medicinal ornamental property.

Question 9.
Broadly classify the extinction process.
Extinction of species – The extinction of species is a natural process. Species have disappeared and new ones have evolved to take their place over. There are three types of extinction processes:

  • Natural extinction – When there is change in environment conditions, certain species disappear and others, (which are more adapted to changed conditions) take their place. This loss of species that occurred in the geological past at a very slow rate is known as natural (background extinction.)
  • Mass extinction – There have been several periods in the earth’s geological history when large number of species became extinct due to catastrophes.
  • Anthropogenic extinction – More number of species is disappearing from the face of the earth due to human activities. Man-made mass extinction represents a very severe depletion of biodiversity.

World Conservation Monitoring Centre has recorded that 533 animal (mostly vertebrates) and 384 plant species (mostly flowering plants) have become extinct since the year 1600. The current rate of extinction is 1000 to 10000 times higher than the background rate of extinction.

Question 10.
Describe the role of wild life in modern agriculture.
Many new improved varieties of crops and useful animals have been derived from their wild relatives by genetic modifications. The wild forms serve as a reserve gene pool which may be tapped for improving disease resistance, pest resistance, cold tolerance and drought tolerance etc.

Question 11.
Why there is legal lapse as far as wildlife conservation is concerned?
The existing laws are adequate to protect our wildlife. The failure of enforcement of these laws of protection of wildlife is one of the reasons for the depletion and extinction of wildlife.

Question 12.
Write a note on extinction.
Extinction is the disappearance of a species from earth when its last surviving member dies. It is of three types:

  • Natural extinction, is the slow replacement of existing species with better adapted species.
  • Mass extinction is extinction of large number of species due to catastrophe, for e.g. extinction of dinosaurs.
  • Anthropogenic extinction is extinction of species: due to human activities.

Question 13.
What are the main causes of extinction of species?
The main causes of extinction of species are as follows:

  • Hunting for commercial purposes and as a sport.
  • Destruction of habitats due to deforestation, establishment of new human settlements, polluted water bodies, roads, dams building etc.
  • Exotic species produce ecological imbalance due to removal of biological control.
  • Pollution-environmental pollution has degraded many important habitats, resulting in decrease in life.
  • Deforestation reduces the area of free movement of wild animals and reduces their reproductive capacity.

Question 14.
List some special Wild Life Projects in India.

  • Gir Lion sanctuary Project: It has started since 1972 by Gujarat and Central Government to save Asiatic Lion.
  • Project Tiger: This programme has started on 1, 1973 by Central Government.
  • Project Hangul: This project was launched by IUCN, WWF and Government of Jammu and Kashmir in 1970 for Kashmir Stag or hangul.
  • Himalayan Musk Deer Project: This a joint effort of Gujarat and Central Government to save Musk deer. It was started in 1972.
  • Crocodile Breeding Project: It was started in 1975 by Central Government and UNDP to save gharial and mugger.

Question 15.
What do you mean by conservation of biodiversity? What are its objectives?
Conservation may be defined as a technique of deriving maximum advantage from the biosphere without in any may degrading it. Conservation of biodiversity has three main objectives:

  • To maintain essential ecological processes and life supporting systems like air, water and soil.
  • To preserve the diversity of species and the range of genetic material of world’s organisms.
  • To ensure a continuous use of species, and ecosystems which will support the rural communities and urban industries.

Question 16.
What is species richness? How is it related to species diversity?
Species richness is the nuclear of species per unit area. With the increase in area, species richness also increases because of availability of natural resources. Number of individuals of different species will give an idea about evenness or equitability of species.

Species diversity is the product of species richness and species evenness.

Question 17.
What are the factors responsible for loss of biodiversity?
Various factors responsible for loss of biodiversity are natural, mass extinction and anthropogenic or due human activities. Human activities have accelerated extinction of species by hunting, destroying habitats, fragmentation, introduction of new species in ecosystem, environmental pollution, construction of buildings, highways, industries, over-exploitation of rare species and due to ignorance.

Question 18.
How can biodiversity be conserved?
For conservation, main steps include, protection of wildlife in natural and artificial habitats, preference should be given to threatened species during conservation programmes, emphasis on preserving ecosystem rather than a single species, protection of critical habitats like breeding habitats, feeding habitat etc., stopping animal trade of rare species, making international agreements to protect the migratory animals, setting up of National parks and Sanctuaries to protect animals.

Combining national efforts with international effort and active public participation for various in their natural habitat. Biodiversity in not homogeneously distributed over time and space. It differs from place to place.

Question 19.
How do you define biodiversity? Explain its significance in the present context
Biodiversity is the totality of genes, species and ecosystem of a region. Depending upon the environmental conditions and species tolerance, biodiversity differs from place to place.

Significance: Human race depends on biodiversity for food source, breeding improved varieties, drugs and medicines, for aesthetic and cultural values and for maintaining the ecological balance.

Human beings are destroying biologically rich and unique habitats for their own interests. Due to increasing population, consumption of resources and pollution human beings are destroying the delicate balance of biosphere, this is affecting biological diversity and causing extinction of species. Biodiversity loss is one of world’s most concerned crisis. It is essential to conserve biodiversity.

Question 20.
What is species diversity?
SPecies are distinct units of diversity, each one is playing a unique role in the ecosystem. Species diversity is the variety of species within a region. It can be measured in terms of species richness, which is the number of species per unit area. So greater the species richness, greater is the species diversity. The number of species increases with the area of the site.

Question 21.
What is the major cause for atmospheric pollution in metro cities? How can this pollution be reduced?
Automobiles are a major cause of atmospheric pollution in metro cities. The pollution can be reduced by proper maintenance of automobiles along with use of lead-free petrol or diesel.

Question 22.
Name the three divisions of diversity.
Biodiversity may be divided into three types: genetic diversity, species diversity and community or ecological diversity. Genetic diversity is related to the variations of genes within a species. The variations may be present in same genes, in entire genes or in chromosomal structures. Species diversity is the variety of species within a region. It depends on species richness and species evenness. Species richness is the number of species per unit area.

Community or ecological or ecosystem diversity is the different types of habitats or ecosystems. It contains diverse number of niches, trophic levels and various ecological processes which support energy flow, food webs and nutrient recycling.
Bihar Board 12th Biology Important Questions Short Answer Type Part 7, 1
Fig.: Interrelationship in Biodiversity.

Question 23.
Write a short note on Ex-situ conservation.
Ex-situ conservation – This approach of conservation of endangered species includes the protection of a group of typical ecosystem f by a network of protected areas. Artificial conditions for individuals of a species are maintained under human supervision. Cultivation of rare plants and rearing of threatened animals is done in botanical and zoological gardens and are preserved in seed banks (plants) or genetic banks (animals).

Question 24.
Explain in brief electrostatic precipitator.
The electrostatic precipitator can remove 99 percent particulate matter present in the exhaust from a thermal power plant. The precipitator has electrode wires that are maintained of several thousand volts, which produce corona that releases electrons. These electrons attach to dust particles giving them a net negative charge. The collecting plates are grounded and attract the charged dust particles. The velocity of air between the plates must be low enough be allow dust to fall. A scrubber inside the precipitator removes gases like sulphur dioxide. In a scrubber, the exhaust is passed through a spray of water or lime.

Question 25.
What laws should be enforced to protect ourselves from noise pollution?
Stringent following of laws laid down in relation to noise like delimitation of horn-free zones around hospitals and schools, permissible sound-levels of crackers and of loudspeakers, timings after which loudspeakers cannot be played, etc. need to be enforced to protect oursevles from noise pollution.

Question 26.
What are the effects of discharge of sewage into a river?
When sewage is discharged into a river, micro-organisms involved in biodegradation of organic matter in the receiving water bodies consume a lot of oxygen, and thus, there is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. This cause mortality of fish and other aquatic creatures.

Question 27.
What are the effects of the presence of large amount of nutrients in water?
Presence of large amount of nutrients in water causes excessive growth of planktonic algae, called algal bloom which imparts a distant colour to the water bodies. Algal blooms cause deterioration of the water quality and fish mortality. Some algal bloom are also extremely toxic to human beings and animals.

Question 28.
Why are plants of water hyacinth called the world’s most problematic aquatic weed?
Plants of water hyacinth are called the most problematic aquatic weed because these plant grow abundantly in eutrophic water bodies, and lead to an imbalance in the ecosystem of the water bodies.

Question 29.
What are the effect of disposal of sewage from homes and hospitals directly into water bodies?
Sewage of homes and hospitals contain many undesirable pathogenic micro-organisms, and if disposed directly into water can causfe outbreak of serious diseases, such as, dysentery, typhoid, jaundice, cholera etc.

Question 30.
What are the components of water from industries like petroleum, paper manufacturing, metal extraction and processing and chemical manufacturing?
Waste water of the above industries contain toxic substances and a variety of organic compounds.

Question 31.
What is cultural or accelerated eutrophication?
Pollutants from man’s activities like effluent from industries and homes can radically accelerate the ageing process of water bodies. This phenomenon is called cultural or accelerated eutrophication.

Question 32.
What are sanitary landfills?
Sanitary landfills are open pits. The wastes are dumped in a depression or trench after compaction, and covered with dirt every day.

Question 33.
What is reforestation?
Reforestation is the process of restoring a forest that once existed but was removed at some point of time in the past. In a deforested area, reforestation may occur naturally. Reforestation can be speeded by planting trees with due to consideration to biodiversity that earlier existed in that area.

Question 34.
What are the effects of wastewater of thermal power plants if disposed directly into water bodies?
Thermal wastewater if disposed directly into water bodies eliminates or reduces the number of organisms sensitive to high temperature, and may exchange the growth of plant and fish in extremely cold areas but, only after causing damage to the indigenous flora and fauna.

Question 35.
What are municipal solid wastes?
Municipal solid wastes are waste from homes, offices, stores, schools, hospitals, etc. That are collected and disposed by the municipality. These wastes generally comprise paper, food wastes, plastics, glass, metals, rubber, leather, textile, etc.

Question 36.
What steps should be taken by human beings to solve environment issues?
All waste that is generated by us should be categorised into three types:

  1. bio-degradable
  2. recyclable
  3. non-biodegradable.

The biodegradable materials should be put into deep pits in the ground and be left for natural breakdown. Only the non-biodegradable waste should be disposed off. The need to reduce our garbage generation should be a prime goal.

Question 37.
What is organic farming?
Organic farming is a cyclical, zero-waste procedure, where waste products from one process are cycled in as nutrients for other processes. This allows the maximum utilisation of resource and increases the efficiency of production.

Question 38.
What has led to the enchancement of ozone degradation? How?
Chlorofluorocarbons (CFCs) has led to the degradation of the ozone layer. CFCs discharged in the lower part of atmosphere move upward and reach stratosphere. In stratosphere, UV rays acts on them releasing Cl atoms.

Cl degrades ozone releasing molecular oxygen, with these atoms acting mearly as catalysts. Cl atoms are not consumed in the reaction. Thus CFCs are added to the stratosphere which have permanent and continuing affects on ozone levels.

Question 39.
What are the effects of waterlogging?
Irrigation without proper drainage of water leads to waterlogging in the soil besides affecting the crops, waterlogging draws salt to the surface of the soil. The salt is then deposited as a thin crust on the land surface or starts collecting at the roots of the plants. This increased salt content is inimical to the growth of crops and is extremely damaging to agriculture.

Question 40.
How does deforestation occur?
Deforestation occurs due to various human activities. These are as follows:

  • Conversion of forest to agricultural land so as to feed the growing human population.
  • Trees are used for timber, firewood, cattle ranching and for several other purposes.
  • Slash and burn agriculture also called Jhum cultivation in northeastern state of India, has also contributed to deforestation.

Question 41.
Write chromosomal abnormalities in Klinefelter’s Syndrome and Turner’s Syndrome.
In Klinefelter’s syndrome are more sex chromosome present. In such syndrome the chromosomes are 47 (44A + xxy). This is trisomy condition.

In Turner’s syndrome there is one sex-chromosome is less. This is monosomy condition. The chromosomes are 45 (44A + xo). Such is sterile female.

Question 42.
What is polygenic trait?
This is a condition in which one character is controlled by more an one pair genes. When a character is controlled by more than a pair of g genes then such inheritance is called polygenic inheritance. For example the 5 sun of human is controlled by more than two pair genes.

Question 43.
Name the technique used to separate DNA fragments in the laboratory.
In laboratory the DNA fragments are separated by Agarose Gel electrophoresis.

Question 44.
Discuss about advantages of asexual reproduction.
Advantages of asexual reproduction are

  • Single parent is required
  • Genetically identical offsprings produced
  • Helps in dispersal of species
  • Rapid reproduction.

Question 45.
What is interferon?
Interferon is secreted from microbes infected cell. Interferon enters into nearby cells and made resistance against microbes. After enterance into healthy cells promote proteins synthesis agaist microbes. It gives temporary immunity.

Question 46.
If in one strand of DNA the sequence of nitrogenous bast are as
Then what will be the sequence of nitrogenous bases in complementary strand in 5′ – 3′ direction?

Question 47.
How did Louis Pasteur discredited the theory of spontaneous generation?
Louis Pasteur discredited the theory of spontaneous generation by not plugging the sterilized sugar solution. He observed the livings entered into sugar solution and reproduce. Thus he proved the new organism developed when microbes entered into sugar solution.