Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Pathogens are disease-causing microorganisms that enter the body through air, water (), food, or physical contact.
Communicable diseases are microbial diseases that spread from an infected person to a healthy person, such as cholera, common cold, and tuberculosis.
Carriers (Vectors) are organisms that carry pathogens without being affected themselves. Examples include the housefly, female mosquito (carrier of parasite), and female mosquito (carrier of Dengue virus).
Food Poisoning is caused by toxins produced by microorganisms like that grow on food items.
Food Preservation techniques involve using chemical or physical methods to prevent microbial growth. Common preservatives include Sodium benzoate () and Sodium metabisulphite ().
Pasteurization involves heating milk to about for to seconds and then suddenly chilling it to prevent the growth of microbes.
Plant diseases caused by microbes include Citrus Canker (Bacteria), Rust of Wheat (Fungi), and Yellow Vein Mosaic of Bhindi (Virus).
📐Formulae
💡Examples
Problem 1:
A student observes that meat covered with dry salt () does not spoil for a long time. Explain the scientific principle behind this.
Solution:
Dry salting creates a high-salinity environment which draws out water () from the microbial cells through the process of osmosis.
Explanation:
Microorganisms require moisture to grow. By removing and increasing the concentration of , the bacterial cells dehydrate and cannot survive or multiply, thus preserving the meat.
Problem 2:
Identify the causative organism and mode of transmission for Malaria.
Solution:
Causative Organism: (a protozoan); Mode of Transmission: Female mosquito (Vector).
Explanation:
When the mosquito bites an infected person, it picks up the parasite. When it subsequently bites a healthy person, it injects the parasite into the bloodstream, causing the disease.
Problem 3:
Why is it advised to keep food covered and avoid eating uncovered items from the roadside?
Solution:
To prevent contamination by pathogens carried by vectors like (Housefly).
Explanation:
Houseflies sit on garbage and animal excreta, where pathogens stick to their bodies. When they sit on uncovered food, they transfer these , leading to diseases like Cholera.