Class 8: Microorganisms and Food Preservation

Study Notes

Chapter 8 of the Class 8 curriculum is about microorganisms and their effects on humans, animals, and plants.
Microorganisms can be useful for humans and animals, but harmful for plants.
Pathogens are microorganisms that cause diseases, and they can enter the human body through contaminated food, water, or infected parasites.
Communicable diseases can spread through infected parasites, contaminated food or water, or physical contact.
Insects and animals can act as carriers for diseases, spreading them to humans.
Food poisoning can occur when microorganisms present in food contaminate it and cause illness.
Preservation methods like chemical preservation using sodium benzoate and sodium metabisulfite can extend the shelf life of food by inhibiting the growth of microorganisms.
Salt and vinegar can also be used for preservation, as seen in the example of pickles.
Post-pasteurization and poststerilization processes involve heating milk to a high temperature, then quickly cooling it to prevent harmful bacteria from growing.
The process of pasteurization involves heating milk to 70 degrees Celsius for 15-30 seconds, then rapidly cooling it to store it safely.
Poststerilized milk remains safe to consume for a few days due to harmful bacteria being killed off during the high-temperature treatment.- Six test tourism recommends storing food in tight containers or packets to prevent microbial attacks and food spoilage.
Nitrogen fixation involves root nodules in legume plants where Rhizobium bacteria convert atmospheric nitrogen into a usable form for plants.
Root nodules provide shelter for bacteria to convert atmospheric nitrogen into a usable form, benefiting plant growth.
Plants utilize the converted nitrogen from bacteria for their growth, which later enters the food chain through animals and humans.
Animals and humans cannot directly use atmospheric nitrogen but benefit from the converted usable form present in plants.
Bacteria convert nitrogen compounds from dead animals or waste into gaseous nitrogen, completing the nitrogen cycle.
The nitrogen cycle starts with atmospheric nitrogen, converts it into a usable form, and then back into atmospheric nitrogen, creating a continuous cycle.