Q1. What is the Hardy–Weinberg Principle? Answer: Allele frequencies remain constant from generation to generation in the absence of evolutionary forces.
Q2. Define gene pool. Answer: The total collection of all genes and their alleles in a population.
Q4. What does p represent? Answer: Frequency of the dominant allele (A).
Q5. What does q² represent? Answer: Frequency of homozygous recessive genotype (aa).
Q6. Name the five factors affecting Hardy–Weinberg equilibrium. Answer: Gene flow, genetic drift, mutation, genetic recombination, and natural selection.
Q7. What is genetic drift? Answer: Random changes in allele frequencies due to chance, especially in small populations.
Q8. What is the founder effect? Answer: A form of genetic drift in which a small group establishes a new population with different allele frequencies.
Biological evolution began after the origin of the first cellular life forms.
Evolution occurs through Natural Selection.
2. Darwin’s Theory of Natural Selection
The two main concepts are:
Branching descent
Natural selection
3. Branching Descent
All organisms evolved from common ancestors.
New species arise by divergence from ancestral species.
4. Natural Selection
Nature selects individuals having favourable inherited variations.
These individuals:
Survive better.
Reproduce more.
Leave more offspring.
5. Fitness
According to Darwin,
Fitness = Reproductive success
It does NOT mean:
Physical strength
Body size
Intelligence
It means ability to survive and produce more offspring.
6. Genetic Basis of Evolution
Adaptation is heritable.
Fitness has a genetic basis.
Only inherited variations can be selected by nature.
Board Point: Acquired characters are not inherited.
7. Adaptation
Adaptation means characteristics that help an organism survive in its environment.
Example:
Antibiotic-resistant bacteria.
Camouflage in insects.
8. Example of Bacteria Evolution
A bacterial colony has natural variations.
When the environment changes, only bacteria with favourable traits survive.
They reproduce rapidly.
Eventually, the new type dominates the population.
Reason: Bacteria divide very quickly.
9. Rate of Evolution
Rate depends on generation time.
Fast Evolution
Bacteria
Viruses
Slow Evolution
Birds
Fish
Mammals
10. Lamarck’s Theory
Proposed by Jean Baptiste Lamarck.
Theory:
Evolution occurs by use and disuse of organs.
Acquired characters are inherited.
Example
Giraffes developed long necks by stretching to reach leaves.
Current Status: Rejected.
11. Darwin vs Lamarck
Darwin
Lamarck
Natural Selection
Use and Disuse
Heritable variations are selected
Acquired characters inherited
Accepted
Rejected
12. Thomas Malthus
His work on population growth influenced Darwin.
Natural resources are limited.
Organisms compete for survival.
13. Observations of Darwin
Organisms produce more offspring than can survive.
Resources are limited.
Population size remains relatively stable.
Individuals show variations.
Most variations are inherited.
Competition exists among organisms.
14. Struggle for Existence
Due to limited resources, organisms compete for:
Food
Space
Shelter
Mates
15. Survival of the Fittest
Only organisms with favourable inherited traits survive and reproduce more successfully.
16. Evolution is Gradual
Evolution occurs:
Slowly
Over many generations
By accumulation of favourable variations
Flow Chart (Very Important)
Variation ⬇ Competition ⬇ Natural Selection ⬇ Survival ⬇ More Reproduction ⬇ Inheritance ⬇ Evolution ⬇ New Species
One-Mark Questions
Q1. What is fitness according to Darwin? Answer: Reproductive fitness (ability to leave more offspring).
Q2. Name the two key concepts of Darwinism. Answer: Branching descent and natural selection.
Q3. Why do bacteria evolve faster than mammals? Answer: Because bacteria have a very short generation time and reproduce rapidly.
Q4. Which scientist proposed the theory of use and disuse? Answer: Jean Baptiste Lamarck.
Q5. Who influenced Darwin’s ideas on population? Answer: Thomas Malthus.
Q6. What is adaptation? Answer: An inherited characteristic that helps an organism survive and reproduce in a particular environment.
NCERT Keywords for Board Exams
Biological Evolution
Natural Selection
Branching Descent
Variation
Adaptation
Fitness
Reproductive Success
Heritable Variation
Lamarckism
Use and Disuse
Acquired Characters
Thomas Malthus
Struggle for Existence
Survival of the Fittest
Exam Tip: CBSE frequently asks the differences between Darwin’s theory and Lamarck’s theory, the meaning of fitness, and the role of variation and natural selection in evolution.
Definition: Adaptive radiation is the evolution of different species from a common ancestor within a geographical area, where each species becomes adapted to a different habitat or ecological niche.
NCERT Definition:
The process of evolution of different species in a given geographical area starting from a common ancestor and radiating into different habitats is called adaptive radiation.
Characteristics of Adaptive Radiation
Begins with a common ancestral species.
Occurs in an isolated geographical region (e.g., islands or continents).
Different populations adapt to different ecological niches.
Results in the formation of many closely related species.
Example 1: Darwin’s Finches (Galápagos Islands)
Darwin observed several species of finches on the Galápagos Islands.
All evolved from a common seed-eating ancestor.
Different species developed different types of beaks according to their food habits.
Finch Type
Adaptation
Seed-eating
Thick, strong beak
Insect-eating
Thin, pointed beak
Cactus-feeding
Long beak
Vegetarian
Broad beak
Reason: Different food resources in different habitats led to natural selection.
Example 2: Australian Marsupials
Australia was geographically isolated.
From a common marsupial ancestor, many different marsupials evolved:
Kangaroo
Koala
Wombat
Bandicoot
Sugar glider
Tasmanian wolf
Marsupial mole
Marsupial rat
Each occupies a different ecological niche.
This is another classic example of adaptive radiation.
Adaptive Radiation and Convergent Evolution
Australia also has placental mammals that resemble marsupials but evolved independently.
Examples:
Placental Mammal
Australian Marsupial
Mole
Marsupial mole
Anteater
Numbat (banded anteater)
Mouse
Marsupial mouse
Flying squirrel
Flying phalanger (sugar glider)
Wolf
Tasmanian wolf
Although they look alike, they do not share a recent common ancestor for these traits.
This similarity is due to convergent evolution, where unrelated organisms evolve similar adaptations because they live in similar environments.
Difference Between Adaptive Radiation and Convergent Evolution
Adaptive Radiation
Convergent Evolution
One ancestor gives rise to many species
Different ancestors evolve similar features
Produces divergent evolution
Produces analogous similarities
Species are closely related
Species are distantly related
Example: Darwin’s finches
Placental wolf and Tasmanian wolf
Flow Chart (Easy to Remember)
Common Ancestor
│
▼
Different habitats
│
Natural Selection
│
Different adaptations
│
Formation of new species
│
Adaptive Radiation
NCERT Exam Points
Adaptive radiation = Evolution of many species from one common ancestor in a geographical area.
Darwin’s finches and Australian marsupials are classic examples.
Placental mammals and Australian marsupials demonstrate convergent evolution, as unrelated groups independently evolved similar adaptations.
Definition: Industrial melanism is the increase in the frequency of dark-coloured (melanic) individuals in a population due to industrial pollution and natural selection.
2. Camouflage
Definition: Camouflage is the ability of an organism to blend with its surroundings to avoid detection by predators.
3. Anthropogenic Evolution
Definition: Evolution caused by human activities such as the excessive use of antibiotics, pesticides, and herbicides.
4. Stochastic Process
Definition: A stochastic process is a chance-based process in which evolution occurs due to random mutations and natural selection, not according to a predetermined plan.
Industrial Melanism (Peppered Moth) – Key Facts
Before Industrialisation
Tree trunks were covered with white-coloured lichens.
White-winged moths were well camouflaged.
Dark (melanic) moths were easily seen and eaten by predators.
White-winged moths were more numerous.
After Industrialisation
Industrial smoke and soot blackened tree trunks.
Lichens disappeared due to pollution.
White moths became easily visible to predators.
Dark (melanic) moths became better camouflaged.
Dark moths survived and reproduced more.
Their population increased.
In Rural (Unpolluted) Areas
Lichens remained abundant.
White moths continued to dominate.
Melanic moths remained fewer.
Why Are Lichens Called Pollution Indicators?
Lichens are highly sensitive to air pollution.
They do not grow in polluted areas.
Presence of lichens indicates clean air.
CBSE One-liner: Lichens are natural indicators of industrial air pollution.
Significance of Industrial Melanism
Best example of Natural Selection.
Demonstrates Evolution in action.
Shows that organisms with favourable adaptations survive and reproduce.
Antibiotic Resistance
Important Facts
Excessive use of antibiotics kills sensitive bacteria.
Resistant bacteria survive.
Resistant bacteria multiply rapidly.
Over time, resistant strains become common.
Example: Antibiotic-resistant bacteria.
Herbicide and Pesticide Resistance
Herbicides
Kill susceptible weeds.
Resistant weeds survive and reproduce.
Pesticides
Kill susceptible insects.
Resistant insects survive and multiply.
Anthropogenic Evolution
Definition
Evolution resulting from human activities.
Examples
Antibiotic-resistant bacteria
Pesticide-resistant insects
Herbicide-resistant weeds
Drug-resistant parasites
Important NCERT Statements
Better-adapted organisms survive and increase in number.
No variant is completely wiped out.
Evolution can occur within months or years.
Human activities accelerate natural selection.
Evolution is not a directed process.
Evolution is based on chance mutations and natural selection.
CBSE One-Mark Facts
Industrial melanism is evidence of natural selection.
Dark moths survived after industrialisation.
White moths survived before industrialisation.
Lichens are indicators of air pollution.
Camouflage helps organisms escape predators.
Excessive antibiotics lead to antibiotic resistance.
Excessive pesticides lead to pesticide resistance.
Excessive herbicides lead to herbicide-resistant weeds.
Evolution caused by humans is called anthropogenic evolution.
Evolution is a stochastic (chance-based) process.
Mutation provides variation, while natural selection acts on that variation.
Flow Chart (Very Important for Board Exams)
Before Industrialisation
White lichens on trees → White moths camouflaged → White moths survive → White moth population increases
⬇️
After Industrialisation
Smoke and soot blacken trees → Lichens disappear → Dark moths camouflaged → Dark moths survive → Dark moth population increases
Microbes are present everywhere –in soil, water, air, inside our bodies and that of other animals and plants. True or False
Ans. True
Microbes are present only in favorable conditions. Comment
Ans. NO. Microbes are present even at places where no other life-form could possibly survive– sites such as deep inside the geysers (thermal vents) where the temperature may be as high as 1000C, deep in the soil, under the layers of snow several metres thick, and in highly acidic environments.
Microbes include
Protozoa
Bacteria
Fungi
Viruses, viroids and prions
All
Ans. 5) All
Draw a well labeled diagram of a bacteriophage.
Ans.
Adenovirus which causes
Respiratory infections
Skin infection
Circulatory problems
All
Ans. Respiratory infections
Mosaic Virus (TMV) is
Polyhedral
Spherical
Rod-shaped
Complex
Ans. 3) Rod-shaped
181 Rod-shaped Tobacco
Which of the following is FALSE?
Microbes cause a large number of diseases in human beings.
Microbes cause diseases in animals and plants. \
All microbes are harmful
Several microbes are useful to man
Ans. All microbes are harmful
What is the full form of LAB?
Ans. Lactic Acid Bacteria
Name the organism which converts milk into curd.
Ans. Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB)grow in milk and convert it to curd.
How curd is prepared?
Ans. To prepared curd, a small amount of curd added to the fresh milk as inoculum or starter containing millions of LAB, which at suitable temperatures multiply, thus converting milk to curd.
Mention some useful applications of LAB besides converting milk to curd.
Ans. Some useful applications of LAB are:
During growth, the LAB produce acids that coagulate and partially digest the milk proteins.
Improves nutritional quality by increasing vitamin B12.
In our stomach, the LAB play very beneficial role in checking disease causing microbes.
How dough, which is used for making foods such as dosa and idli, is prepared?
Ans. The dough, which is used for making foods such as dosa and idli is fermented by bacteria.
Mention the reason for the puffed-up appearance of dough.
Ans. The puffed-up appearance of dough is due to the production of CO2 gas.
How the dough, which is used for making bread, is prepared?
Ans. The dough, which is used for making bread, is fermented using baker’s yeast (Saccharomyces cerevisiae).
A number of traditional drinks and foods are made by _________________________.
Ans.fermentation by the microbes
What is “Toddy”?
Ans. ‘Toddy’ is a traditional drink of some parts of southern India.
How toddy is made?
Ans. ‘Toddy’ is made by fermenting sap from palms.
Microbes are also used to __________fish, soyabean and bambooshoots to make foods.
Ans. ferment
Why there are large holes in ‘Swiss cheese’?
Ans. The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium
Name the bacterium which produces in ‘Swiss cheese’.
Ans. Propionibacterium sharmanii
How are ‘Roquefort cheese’ are ripened?
Ans. The ‘Roquefort cheese’ are ripened by growing a specific fungi on them, which gives them a particular flavour.
10.2 MICROBES IN INDUSTRIAL PRODUCTS
Give example of two products produced by microbes?
Ans.Beverages and antibiotics
What are fermentors?
Ans. Fermentors are very large vessels in which microbes are grown to produce valuable products on an industrial scale.
Name the yeast used for the production of beverages like wine, beer, whisky, brandy or rum.
Ans. Saccharomyces cerevisiae, commonly called Brewer’s yeast
Which of the following is true?
Wine and beer are produced without distillation
Whisky, brandy and rum are produced by distillation
Whisky, brandy and rum are produced without distillation
Both (1) & (2)
Ans. 4) Both (1) & (2)
Write a short note on “Fermented Beverages”.
Ans. Microbes particularly yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky, brandy or rum. The yeast Saccharomyces cerevisiae used for bread-making and commonly called brewer’s yeast is used for fermenting malted cereals and fruit juices, to produce ethanol.
Depending on the type of the raw material used for fermentation and the type of processing (with or without distillation) different types of alcoholic drinks are obtained. Wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth.
What are antibiotics?
Ans. Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes.
Antibiotics have significantly improved our ability to treat deadly diseases such as plague, whooping cough (kali khansi), diphtheria (gal ghotu) and leprosy (kusht rog).
Name the first antibiotic.
Ans. Penicillin.
Name the scientist who discovered Penicillin.
Ans. Alexander Fleming
How did Alexander Fleming discover Penicillin?
Ans. Discovery of Penicillin is an example of chance discovery (serendipity). Alexander Fleming while working on Staphylococci bacteria, once observed that a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. He found out that it was due to a chemical produced by the mould and he named it Penicillin after the mould Penicillium notatum.
Name the source of Penicillin.
Ans. Penicillium notatum (also known as Penicillium Chrysogenum)
Name the scientists who established full potential of penicillin as an effective antibiotic.
Ans. Ernest Chain and Howard Florey
Name some antibiotics and also mention their sources.
Ans. Some antibiotics with their sources:
Name of antibiotics
Source organism
Penicillin
Penicillium notatum (also known as Penicillium Chrysogenum)
Streptomycin
Streptomyces griseus
Tetracycline
Streptomyces rimosus
Gentamicin
Micromonospora purpurea
Griseofulvin
Penicillium griseofulvum
10.2.3 Chemicals, Enzymes and other Bioactive Molecules
Microbes are also used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes. True/ False
Ans. True
Which of the following are acid producers?
Aspergillus niger
Acetobacter aceti
Clostridium butylicum
Lactobacillus
All
Ans. 5) All
Name the microbe which produces citric acid.
Ans. Aspergillus niger (a fungus)
Name the microbe which produces acetic acid.
Ans. Acetobacter aceti (a bacterium)
Name the microbe which produces acetic acid.
Ans. Clostridium butylicum (a bacterium)
Name the microbe which produces lactic acid.
Ans. Lactobacillus (a bacterium)
Name the yeast used for commercial production of ethanol.
Ans. Saccharomyces cerevisiae
Name the enzymes used in detergent formulations.
Ans. Lipases are used in detergent formulations and are helpful in removing oily stains from the laundry.
Bottled fruit juices bought from the market are clearer as compared to those made at home. Why?
Ans. This is because the bottled juices are clarified by the use of enzymes pectinases and proteases.
Name the bacterium which produces Streptokinase.
Ans. Streptococcus
Mention the function of Streptokinase.
Ans. Streptokinase is used as a ‘clot buster’ for removing clots from the blood vessels of patients who have undergone myocardial infaction leading to heart attack.
Name the organism which produces cyclosporin A.
Ans. Cyclosporin A is produced by the fungus Trichoderma polysporum.
What is cyclosporin A?
Ans. Cyclosporin A is bioactive molecule, which is used as an immunosuppressive agent in organ-transplant patients.
Name the organism which produces Statins.
Ans. Statins are produced by the yeast called Monascus.
What are Statins?
Ans. Statins are a class of drugs that acts as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.
10.3 MICROBES IN SEWAGE TREATMENT
Why is sewage treated before disposal?
Ans. Sewage also called municipal waste-water contains large amounts of organic matter, human excreta and microbes. Many microbes are pathogenic in nature. If sewage is discharged directly into natural water bodies like rivers and streams directly, it will cause pollution and health hazards. Therefore, sewage is treated in sewage treatment plants (STPs) to make it less polluting.
Treatment of waste water is done by the heterotrophic microbes naturally present in the sewage. True/False
Ans. True
Name the two stages of sewage treatment.
Ans. Sewage treatment is carried out in two stages:
Primary Treatment
Secondary Treatment or Biological Treatment
Briefly describe primary treatment of sewage.
Ans. Primary treatment steps mainly involve physical removal of particles – large and small – from the sewage through filtration and sedimentation. Substances present in sewage are removed in stages; initially, floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge, and the supernatant forms the effluent. The effluent from the primary settling tank is taken for secondary treatment.
Describe secondary treatment of sewage.
Ans. Secondary treatment of sewage takes place as follows:
The primary effluent is passed into large aeration tanks where it is continuously agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh like structures). While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (biochemical oxygen demand) of the effluent. The sewage water is treated till the BOD is reduced.
Once the BOD of sewage or waste water is decreased significantly, the effluent is then passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment. This sediment is called activated sludge.
A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters.
In anaerobic sludge digesters, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as source of energy as it is inflammable.
The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams. In this way water is recycled in nature.
What is the full form of BOD?
Ans. Biochemical Oxygen Demand
Define BOD.
Ans. BOD refers to the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
What is the significance of BOD Test?
Ans. BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water and thus, indirectly, BOD is a gauge of the organic matter present in the water. The greater the BOD of waste water, more is the organic matter present in waste water, more is its polluting potential.
What is activated sludge?
Ans. Activated sludge refers to aerated sewage containing aerobic microorganisms which helps to break it down.
What are the initiatives taken by the government of India to save major rivers from pollution?
Ans. The Ministry of Environment and Forests has initiated the following two plans to save our rivers from pollution:
Ganga Action Plan
Yamuna Action Plan
Under these plans, it has been proposed to build a large number of sewage treatment plants so that only treated sewage may be discharged in the rivers.
10.4 MICROBES IN PRODUCTION OF BIOGAS
What is biogas?
Ans. Biogas is a mixture of gases (containing mainly methane) produced by the microbial activity and which may be used as fuel.
What are the factors that determine the type of the gas produced by microbes?
Ans. Microbes produce different types of gaseous end-products during growth and metabolism.
The type of the gas produced depends upon
The microbes
The organic substrates
Name the main gas produce in fermentation of dough, cheese making and production of beverages?
Ans.
What are methanogens?
Ans. Methanogens are bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with and .
Give an example of methanogens.
Ans. Methanobacterium.
Which of the following statement is true about methanogens?
These bacteria are commonly found in the anaerobic sludge during sewage treatment.
These bacteria are also present in the rumen (a part of stomach) of cattle.
Both (1) & (2)
None
Ans. Both (1) & (2)
What is the role of methanogens in the rumen of cattle?
Ans. The food of cattle contains a large amount of cellulosic material. In rumen, these bacteria assist in the breakdown of cellulose and play an important role in the nutrition of cattle.
Are human beings able to digest the celluose present in our foods?
Ans. Human beings cannot digest cellulose. This is because they lack the enzymes required to breakdown cellulose.
Draw a well labelled diagram of biogas plant. Explain its working.
Ans. The excreta (dung) of cattle, gobar, is rich in methanogens. Dung can be used for production of biogas, commonly called gobar gas.
The biogas plant consists of a 10-15 feet deep concrete tank called digester. Bio-wastes are collected fed into the digester as slurry of dung. A floating cover, called gas-holder, is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity. The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses. The biogas so produced is used for cooking and lighting.
The spent slurry is removed through another outlet and may be used as fertiliser.
Name the institutions responsible for developing technology of biogas production in India?
Ans. The technology of biogas production was developed in India mainly due to the efforts of
Indian Agricultural Research Institute (IARI)
Khadi and Village Industries Commission (KVIC)
10.5 MICROBES AS BIOCONTROL AGENTS
What do you mean by Biocontrol?
Ans.Biocontrol refers to the use of biological methods and biological agents for controlling plant diseases and pests.
Biological control of pests and diseases:
In agriculture, there is a method of controlling pests that relies on natural predation rather than introduced chemicals.
Which of the following is true?
Biodiversity fosters health of the ecosystem
The more variety a landscape has, the more sustainable it is.
Both (1) & (2)
None
Ans. 3) Both (1) & (2)
Write a short note on organic farming. How is it different from ‘conventional’ farming?
Ans. Organic farming is a form of agriculture that relies on techniques such as crop rotation, green manure, compost, and biological pest control.
In organic farming, the emphasis is on developing an understanding of the webs of interaction between the myriad of organisms that constitute the field fauna and flora; and creating a system where pests are not eradicated, but are kept at manageable levels by a complex system of checks and balances within a dynamic ecosystem.
The organic farming believes that the eradication of the creatures that are often described as pests is not only possible, but also undesirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive.
In contrast, the ‘conventional’ farming practices use chemical methods to kill both useful and harmful life forms indiscriminately.
The use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides. True/False
Ans. True
Which of the following is true?
Ladybird is useful in controlling aphids
Dragonflies are useful to get rid of mosquitoes
Both (1) & (2)
None
Ans. 3) Both (1) & (2)
Give an example of microbial biocontrol agent that can be introduced in order to control butterfly caterpillars.
Ans. Bacillus thuringiensis (often written as Bt).
Write a short note on Bacillus thuringiensis.
Ans. Bacillus thuringiensis is an excellent example of microbial biocontrol agent. These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed. The bacterial disease will kill the caterpillars, but leave other insects unharmed.
The development of methods of genetic engineering has allowed us to introduce B. thuringiensis toxin genes into plants, making them resistant to attack by insect pests.
Give one example of pest resistant plant.
Ans. Bt-cotton
Name the fungus which is used in treatment of plant diseases and serves as biocontrol agents of several plant pathogens.
Ans.Trichoderma.
Which of the following is true?
Trichoderma species are free-living fungi
They are very common in the root ecosystems
Both (1) & (2)
None
Ans. Both (1) & (2)
What are Baculoviruses?
Ans. Baculoviruses are pathogens that attack insects and other arthropods.
Name the genus that contains majority of baculoviruses used as biological control?
Ans. Nucleopolyhedrovirus.
What are the advantages of Baculoviruses?
Ans. Advantages of Baculoviruses are:
Baculoviruses are excellent agent for species-specific, narrow spectrum insecticidal applications.
They do not have negative effects on plants, mammals, birds, and fish or even on non-target insects.
They play an important role in integrated pest management (IPM) programme, especially when beneficial insects are to be conserved or when an ecologically sensitive area is being treated.
10.6 MICROBES AS BIOFERTILISERS
How can we deal with pollution caused by the use of chemical fertilisers?
Ans. Pollution caused by the use of chemical fertilisers can be dealt by switching to organicfarming – the use of biofertilisers.
What do you mean by Biofertilisers?
Ans. Biofertilisers refer to a substance which contains organisms that enrich the nutrient quality of the soil.
What are the main sources of biofertilisers?
Ans. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.
What are root nodules?
Ans. These are nodules found on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into organic forms, enriching the nitrogen content of the soil, which is used by the plant as nutrient,
Name two bacteria free-living in the soil that fix nitrogen.
Ans. Azospirillum and Azotobacter
Briefly explain mycorrhiza?
Ans. Mycorrhiza is a symbiotic association between fungi and roots of a vascular plant. Many members of the genus Glomus form mycorrhiza.
In this mycorrhizal association, the fungal symbiont absorbs phosphorus from soil and passes it to the plant. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.
What advantage the fungus derives from mycorrhizal association?
Ans. In mycorrhizal association, the plants supply nutrients (carbohydrates, vitamins, etc), growth stimulators, etc for fungus.
Give examples of Cyanobacteria which fix atmospheric nitrogen.
Ans. Anabaena, Nostoc, Oscillatoria, etc
Briefly describe Cyanobacteria Biofertilizers.
Ans. Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc.
In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.
Microbes are an insignificant component of life on earth. True/False
Ans. False
All microbes are pathogenic. True/False
Ans. False
The dough, which is used to make bread, is fermented by yeast called ______________
Ans. Saccharomyces cerevisiae
EXERCISES
Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?
Give examples to prove that microbes release gases during metabolism.
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Name any two species of fungus, which are used in the production of the antibiotics.
What is sewage? In which way can sewage be harmful to us?
What is the key difference between primary and secondary sewage treatment?
Do you think microbes can also be used as source of energy? If yes, how?
Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell protein (SCP)
(b) Soil
Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd
How do biofertilisers enrich the fertility of the soil?
