Read the following paragraph and answer the given questions.
Bio-fertilisers are organisms that enrich the nutrient quality of the soil like cyanobacteria, while there are organisms that help to control plant diseases and pests. The very familiar beetle, the ladybird and dragonflies are useful to get rid of aphids and mosquitoes, respectively. An example of microbial biocontrol agents that can be introduced to control butterfly caterpillars is certain bacteria, which are available in sachets in the form of dry spores. These spores are mixed with water and sprayed onto vulnerable plants. Trichoderma species that are very common in the root ecosystem, are very effective biocontrol agents of several plant pathogens. Baculoviruses attack insects and other arthropods. Usage of these viruses is desirable when an ecological sensitive area is being treated.
Find the odd one out of the given organisms?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Dragonflies
Three of the options are cyanobacteria (blue-green algae): autotrophic microbes, many of which fix atmospheric nitrogen and serve as biofertilisers in paddy fields.
Option (1) Dragonflies — The odd one out. Dragonflies are insects, used as biocontrol agents to get rid of mosquitoes.
Option (2) Nostoc — A cyanobacterium. It fixes nitrogen and is a biofertiliser.
Option (3) Oscillatoria — A cyanobacterium. It is named with Anabaena and Nostoc in NCERT.
Option (4) Anabaena — A cyanobacterium. It is an important biofertiliser of paddy fields.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Microbes as Biofertilisers – …
Microbes as Biocontrol Agents – “… The very familiar beetle with red and black markings - the Ladybird, and Dragonflies are useful to get rid of aphids and mosquitoes, respectively.”
