Name any two physiological barriers that provide innate immunity. OR Select two disease resistant crop varieti

Question 88 of 117

Q. Name any two physiological barriers that provide innate immunity.

(OR)

Select two disease resistant crop varieties from the list of crop varieties given below : Himgiri, Pusa Gaurav, Pusa Komal, Pusa A-4

Gujarat GsebCBSE Class XII Board 2019Subjective· 1mImportance★★★★★

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Part (a)Concept understanding — Biology Disease Control

Biology Disease Control — A First Look

Think of your body as a city. Every day, germs (bacteria, viruses, fungi, parasites) try to enter — through the air you breathe, the food you eat, a cut on your skin. Most of the time, your body's defence systems stop them before you even notice. That's immunity, your natural security force.

But sometimes the invaders break through. You get a fever, a cough, an infection. Now you need disease control — the set of actions that stop the illness from spreading and help you recover.

What exactly is disease control?

In biology, disease control means reducing the incidence (new cases), prevalence (total cases), or transmission of a disease. It's not about wiping out every germ — that's impossible. It's about keeping the disease at a level where it no longer threatens public health.

The NCERT textbook divides disease control into two broad approaches:

1. Preventive measures — stopping the disease before it starts

These are actions taken by individuals, communities, and governments to block the entry of pathogens.

Vaccination — training your immune system to recognise a germ before it attacks. This is the single most powerful tool in disease control.
Sanitation and hygiene — clean drinking water, proper sewage disposal, handwashing. Many diseases (cholera, typhoid, hepatitis A) spread through contaminated water or food.
Vector control — killing or avoiding the organisms that carry disease. Mosquito nets, insect repellents, draining stagnant water — these control malaria, dengue, chikungunya.
Quarantine and isolation — separating sick people from healthy ones during outbreaks. You saw this during COVID-19.

Important

Prevention is always better than cure. Once a disease spreads in a population, controlling it becomes exponentially harder and more expensive. That's why governments invest heavily in vaccination drives and public sanitation.

2. Curative measures — treating the disease once it occurs

Even with the best prevention, some people will fall ill. Curative measures aim to:

Reduce the severity of the illness (e.g., antibiotics for bacterial infections, antiviral drugs for flu)
Shorten the duration of the illness
Prevent complications and death
Stop the patient from infecting others

The key point: treatment alone cannot control a disease in a population. If you only treat sick people without preventing new infections, the disease keeps circulating.

Why does disease control matter for society?

A single outbreak can paralyse a city. Schools close, hospitals overflow, businesses shut down. The economic cost is enormous. That's why disease control is not just a medical issue — it's a public health issue.

The NCERT textbook emphasises that disease control requires community participation. No matter how good the doctors or vaccines are, if people refuse to vaccinate their children or ignore hygiene, the disease will keep spreading. …

Part (b)Concept understanding — Biofertilizers Biopesticides

Imagine you have a garden. You want your plants to grow strong and healthy, and you also want to keep pests away. There are two main ways to do this: one is with harsh chemicals (chemical fertilizers and pesticides), and the other is with living things or natural substances. Biofertilizers and biopesticides are the second way — they are nature’s own tools for farming.

Let’s start with biofertilizers. Think of them as "living manure." A chemical fertilizer is like giving a plant a direct shot of nutrients — it works fast but can burn the soil over time. A biofertilizer, on the other hand, is a preparation containing live microorganisms (like bacteria, fungi, or algae) that help the plant get nutrients from the soil or air. For example, certain bacteria can take nitrogen from the air and convert it into a form the plant can use. The plant doesn’t get fed directly; instead, the biofertilizer helps the soil become richer and more fertile naturally.

Note

The NCERT textbook (Class 12 Biology, Chapter 10) defines biofertilizers as organisms that enrich the nutrient quality of the soil. The main examples are Rhizobium (a bacterium that lives in root nodules of legumes and fixes nitrogen), Azospirillum and Azotobacter (free-living nitrogen-fixing bacteria), and blue-green algae (like Anabaena) which also fix nitrogen.

Now, biopesticides. These are living organisms or natural substances that control pests — insects, fungi, weeds, etc. — without using synthetic chemicals. Instead of spraying a poison that kills everything (good and bad bugs alike), a biopesticide might use a specific bacterium that only harms a particular caterpillar, or a fungus that attacks a weed. The most famous example is Bacillus thuringiensis (often called Bt), a bacterium that produces a protein toxic to certain insect larvae but harmless to humans, animals, and most other insects.

Important

The key difference between chemical and biological agents: Biofertilizers and biopesticides are renewable, eco-friendly, and do not leave toxic residues in the soil or water. They are a cornerstone of sustainable agriculture — farming that can continue for generations without destroying the land.

Why does this matter for a commerce or humanities student? Because agriculture is not just about biology — it’s about economics, policy, and human health. Chemical fertilizers and pesticides are expensive to produce, can pollute groundwater, and their overuse leads to "superpests" that become resistant. Biofertilizers and biopesticides are often cheaper in the long run, safer for farm workers, and help maintain soil health. Governments around the world (including India) promote them through subsidies and organic farming schemes. Understanding them helps you see why "organic" food costs more, why some farmers switch to natural methods, and how environmental regulations work.

Here’s a quick summary of the main types you should know (from NCERT):

Biofertilizers:
- Rhizobium (symbiotic with legumes) …

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Part (a): Two physiological barriers of innate immunity are stomach acid (low pH) and lysozyme in tears/saliva.

Part (b): From the given list, the disease-resistant crop varieties are Himgiri (wheat) and Pusa Komal (cowpea).

Part (a)

Concept-first idea: Innate immunity is the non-specific, present-from-birth defence, and its physiological barriers are internal body conditions that make survival difficult for microbes (distinct from physical barriers like skin).

Two physiological barriers:

Acid in the stomach (HCl, low pH) — the strongly acidic stomach environment kills most microbes that are swallowed.
Lysozyme — present in tears, saliva and other secretions, this enzyme digests bacterial cell walls. …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

Showing the 12 most recent of 14 on this concept.

GUJCET 2026Set 051 markMCQ
$Q. Which group of microbes are acting as bio control agents? Select the correct option. (A) Baculo virus, Oscillatoria, Rhizobium (B) Azotobacter, Trichoderma, Glomus (C) Trichoderma, Baculo virus, Bacillus thuringiensis (D) Azospirillum, Anabaena, Bacillus thuringiensis$
›Reveal solutionSolution

The all-biocontrol group is Trichoderma, Baculovirus and Bt.

Trichoderma (fungal biocontrol of plant pathogens), Baculoviruses (species-specific insect pathogens) and Bacillus thuringiensis (Bt) (kills caterpillars) are all biological control agents. The other options include N-fixers/cyanobacteria (Rhizobium, Azotobacter, Anaba …
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GSEB Higher Secondary Certificate (HSC) Examination 2026Set ANNUAL1 markMCQ
$Q. Which of the following is an example of cynobacteria?$
(a) Oscillatoria
(b) Spirullina
(c) Azospirillum
(d) Azotobacter
›Reveal solutionSolution

Oscillatoria is a cyanobacterium (blue-green alga), grouped with Nostoc and Anabaena as autotrophic, nitrogen-fixing biofertilisers, unlike Azospirillum/Azotobacter, which are free-living nitrogen-fixing (but non-photosynthetic) bacteria.

…

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GSEB Higher Secondary Certificate (HSC) Examination 2025Set ANNUAL1 markMCQ
$Q. Which of the following is very useful in getting rid of the menace of aphids?$
(a) Baculovirus
(b) Dragonfly
(c) Ladybird
(d) Trichoderma
›Reveal solutionSolution

The ladybird beetle is a classic biological control agent that preys on aphids.

Biological control uses living organisms to manage pests instead of chemical pesticides. The ladybird beetle (ladybug) is a well-known natural predator of aphids and scale insects, consuming large numbers of them and helping control aphid infestations on crops without chemical intervention. Dragonflies are predators mainly of mosquitoes/small flying insects, Baculovirus is used against lepidopteran/in …

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GSEB Higher Secondary Certificate (HSC) Examination 2025Set ANNUAL1 markMCQ
$Q. Trichoderma is a __________.$
(a) Symbiotic lichen
(b) Free-living bacteria
(c) Blue-green algae
(d) Free-living fungus
›Reveal solutionSolution

Trichoderma species are free-living fungi found in root ecosystems, used as biocontrol agents against plant pathogens.

Trichoderma is a genus of free-living fungi that are very common in the root ecosystem (rhizosphere). Several species are effective biocontrol agents against a number of plant pathogenic fungi (e.g. Fusarium, Pythium, Rhizoctonia species causing root rot), making …

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GUJCET 2024Set 101 markMCQ
$Q. Which one of the following statement is correct :$
(i) Baculoviruses are excellent candidates for species specific narrow spectrum insecticidal applications
(ii) Bacillus thuringiensis is used to control butterfly caterpillars
(iii) Ladybird is useful to get rid of mosquitoes
(iv) Trichoderma fungus are used as a biocontrol agents for animal pathogen (A) only (i),
(iii) and
(iv) (B) only
(i) and
(ii) (C) only
(ii) and
(iv) (D) only
(iii) and (iv)
›Reveal solutionSolution

(i) and (ii) are correct; ladybird controls aphids and Trichoderma is a biocontrol for plant pathogens.

(i) Baculoviruses are excellent narrow-spectrum, species-specific insecticidal agents — correct. (ii) Bacillus thuringiensis controls butterfly caterpillars — correct. (iii) Ladybird controls aphids, not mosquitoes — wrong. (iv) * …
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GSEB Higher Secondary Certificate (HSC) Examination 2024Set ANNUAL1 markMCQ
$Q. Which fungus is taking part in the formation of mycorrhiza?$
(a) Mucor
(b) Glomus
(c) Rhizopus
(d) Monuscus
›Reveal solutionSolution

Glomus is the fungal genus most associated with forming mycorrhizae, a mutualistic symbiosis between fungus and plant root that improves the plant's phosphorus uptake.

Mycorrhiza is a symbiotic association between a fungus and the roots of a higher plant; the fungus increases the surface area for absorption and enhances the plant's uptake of phosphorus and water, while receiving photosynthetic carbohydrates from the plant in return. The fungal genus Glomus forms this vesicular-arbuscular mycorrhiza (VAM) association and is exploited as a biofertiliser in …

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GSEB Higher Secondary Certificate (HSC) Examination 2023Set ANNUAL1 markMCQ
$Q. Identify the free-living bacteria which can fix atmospheric nitrogen in the soil.$
(a) Rhizobium
(b) Bt
(c) Azospirillum
(d) Staphylococci
›Reveal solutionSolution
Free-living nitrogen-fixing soil bacteria include Azospirillum and Azotobacter; Rhizobium fixes nitrogen only in symbiosis with legume roots.

Nitrogen-fixing microbes as biofertilisers:

Free-living (non-symbiotic) N2-fixers in soil: Azospirillum, Azotobacter.

Symbiotic N2-fixer: Rhizobium (in root nodules of legumes). …
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GSEB Higher Secondary Certificate (HSC) Examination 2023Set ANNUAL1 markMCQ
$Q. Identify the barrier of innate immunity in which virus infected cells secrete proteins called interferons.$
(a) Cytokine barriers
(b) Physiological barriers
(c) Cellular barriers
(d) Physical barriers
›Reveal solutionSolution
Interferons are cytokines released by virus-infected cells that protect neighbouring cells - the cytokine barrier of innate immunity.

Innate immunity has four types of barriers:

Physical barriers: skin, mucus lining.

Physiological barriers: acid in stomach, saliva, tears.

Cellular barriers: PMNL/neutrophils, monocytes, macrophages, natural killer cells. …
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GSEB Higher Secondary Certificate (HSC) Examination 2022Set ANNUAL1 markMCQ
$Q. Trichoderma fungus is used for what purpose?$
(a) To get rid of aphids and mosquitoes
(b) In the treatment of diseased plants
(c) To control butterfly caterpillars
(d) For narrow-spectrum insecticidal purposes
›Reveal solutionSolution

Trichoderma species are free-living fungi found in root ecosystems that act as effective biocontrol agents against several plant pathogenic fungi.

Trichoderma is widely used in biological control of plant diseases: it parasitises and suppresses soil-borne pathogenic fungi (such as Fusarium and Pythium) that cause root-rot and other diseases in plants, offering an eco-friendly alternative to chemical fungicides. This is different from biocontrol agents used against insect pests (like Ba …

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GUJCET 2021Set 151 markMCQ
$Q. As biological-controller, Baculo viruses are pathogens to which organisms? (A) fungi and insects (B) insects and beetles (C) insects and other arthropods (D) beetles and arthropods$
›Reveal solutionSolution

Baculoviruses (genus Nucleopolyhedrovirus) attack insects and other arthropods, making them narrow-spectrum biocontrol agents.

Concept. They are species-specific pathogens of insects and other arthropods, useful in integrated pest management. …
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GUJCET 2020Set x1 markMCQ
$Q. Choose the correct option for the statements for Mycorrhiza:$
(i) It absorbs phosphorus from soli.
(ii) It forms root nodules with the association of Rhizobium
(iii) They are resistance to root-borne pathogens, tolerance to salinity & drought.
(iv) They fix atmospheric nitrogen. (A)
(i) and
(ii) (B)
(i) and
(iii) (C) (i),
(ii) and
(iii) (D)
(ii) and (iv)
›Reveal solutionSolution
True for mycorrhiza: (i) absorbs soil phosphorus and (iii) resistance to root pathogens + salinity/drought tolerance → (i) and (iii).

Mycorrhiza is a symbiotic association between a fungus and plant roots.

(i) TRUE — the fungal partner absorbs phosphorus from soil and passes it to the plant.

(ii) FALSE — root nodules with Rhizobium are a legume association, not mycorrhiza. …
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GSEB Higher Secondary Certificate (HSC) Examination 2020Set ANNUAL1 markMCQ
$Q. Match the following and choose the correct option. Column - I: i) Salmonella typhi, ii) Plasmodium, iii) Entamoeba histolytica, iv) Epidermophyton Column - II: p) Malaria, q) Typhoid, r) Ringworm, s) Amoebiasis$
(a) (i - r), (ii - q), (iii - p), (iv - s)
(b) (i - q), (ii - p), (iii - s), (iv - r)
(c) (i - q), (ii - r), (iii - s), (iv - p)
(d) (i - p), (ii - q), (iii - r), (iv - s)
›Reveal solutionSolution
Each disease-causing organism must be matched to the disease it causes: Salmonella typhi (bacterium) causes typhoid; Plasmodium (protozoan) causes malaria; Entamoeba histolytica (protozoan) causes amoebiasis; Epidermophyton (fungus) causes ringworm.

Matching each organism to its disease:

Salmonella typhi — a bacterium — causes Typhoid (q)

Plasmodium — a protozoan parasite transmitted by female Anopheles mosquito — causes Malaria (p)

Entamoeba histolytica — a protozoan — causes Amoebiasis (s) …
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Q.Name any two physiological barriers that provide innate immunity.

Part (a)

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