CBSE 2026 · Region 1 · Set 1 · Q33 · 5 marks
(i)Name the protozoan species that is responsible for causing the most serious and even fatal malarial disease.(ii)Name the host in which the parasite completes its sexual stages and explain the changes taking place.(iii)How does the parasite damage the human body after entering the blood stream ?(iv)Suggest two effective preventive measures to control the spread of this disease in endemic regions.(i)What are bio-fertilizers ?(ii)Name the different types of microorganisms used as bio- fertilizers in organic farming and explain how each contributes to soil fertility.(iii)Write two advantages of using bio-fertilizers over chemical fertilizers.
(i)
Name the protozoan species that is responsible for causing the most serious and even fatal malarial disease.
(ii)
Name the host in which the parasite completes its sexual stages and explain the changes taking place.
(iii)
How does the parasite damage the human body after entering the blood stream ?
(iv)
Suggest two effective preventive measures to control the spread of this disease in endemic regions.
(i)
What are bio-fertilizers ?
(ii)
Name the different types of microorganisms used as bio- fertilizers in organic farming and explain how each contributes to soil fertility.
(iii)
Write two advantages of using bio-fertilizers over chemical fertilizers.
Marking-scheme solution
(i)
Plasmodium falciparum
(ii)
$\displaystyle \diamond$ Female Anopheles Mosquito
$\displaystyle \diamond$
Mosquito picks up gametocytes from the infected person.
Fertilization and development takes place in mosquito gut.
Sporozoites from gut migrate to salivary glands of mosquito.
(iii)
After entering the blood stream they enter liver, and then into red blood cells and reproduce asexually, RBCs rupture and a toxic substance haemozoin is released causing chills and high fever.
(iv)
$\displaystyle \diamond$ Avoiding stagnation of water in and around residential areas.
$\displaystyle \diamond$ Regular cleaning of household coolers.
$\displaystyle \diamond$ Use of mosquito nets.
$\displaystyle \diamond$ Introduce fishes like Gambusia in ponds – they feed on mosquito larval.
$\displaystyle \diamond$ Spraying insecticides in ditches of doors and windows to have wire mesh.
$\displaystyle \diamond$Any other appropriate preventive measures.
(Any two)
(i)
Bio fertilizers – Organisms that enrich the nutrient quality of soil. e.g. bacteria fungi and cyanobacteria.
(ii)
$\displaystyle \diamond$ Bacteria / Rhizobium / Azotobacter / Azospirillum
Rhizobium forms symbiotic association with roots of leguminous plants and fix atmospheric nitrogen into organic forms to be used by the plant,
Azotobacter or Azospirillum fix atmospheric nitrogen while free living in the soil.
$\displaystyle \diamond$ Fungi /genus Glomus .
Fungi breakdown organic matter to release nutrients,
Glomus form mycorrhiza with roots of the plants.This association helps to absorb phosphorous from soil and pass to the plant, plants show resistance to root-borne pathogens, plants show tolerance to salinity and drought,
There is increase in plant growth.
$\displaystyle \diamond$ Cyanobacteria / Anabaena / Nostoc / Oscillatoria (Any one)
Fix atmospheric Nitrogen, serve as important biofertilizers in paddy fields (Any one)
(iii)
-Bio fertilizers do not pollute our environment (soil, ground water).
$\displaystyle \diamond$ They conserve the beneficial soil microbes.
$\displaystyle \diamond$ Do not cause contamination and harm human health.
(Any two)
Microbes in Human WelfareMicrobes as BiofertilisersUnderstandlong_answermedium
More from Microbes in Human Welfare
- Assertion: Activated sludge contains large population of bacteria. Reason (R): These bacteria help in…2026 · asked 3×
- Assertion: Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage.…2026 · asked 3×
- Study the figure given below and answer the questions that follow. Identify the figure and state its…2025 · asked 3×
- Study the given diagram of Sewage Treatment Plant (S.T.P.) and answer the questions that follow: S.T.P.…2022 · asked 3×
- Mention the common bacterium found in the anaerobic sludge during sewage treatment and also in the rumen of…2022 · asked 3×
- A laboratory assistant collected three water samples, namely river water, untreated sewage water and…2026 · asked 3×
- What do you mean by activated sludge in an STP? Explain the biological treatment of the major part of the…2025 · asked 3×
- Bacillus thuringiensis plays an important role in Integrated Pest Management strategy. Explain how. Name any…2022 · asked 3×
CBSE Class 12 Biology past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.