Ch 9Microbes in Human Welfare — Class 12 Biology, concept-first.

When most people hear the word "microbe," they think first of disease -- the bacteria and viruses that cause infections. But this reaction badly under-represents the microbial world.

Fermentation, in the biological sense used throughout this chapter, is the metabolic process by which microorganisms break down organic molecules -- most commonly sugars -- to obtain energy, typically…

Alcoholic beverages are, at their biochemical core, all products of the same basic process seen in bread-making -- yeasts, principally strains of Saccharomyces cerevisiae, fermenting sugars into ethan…

Household fermentation relies on whatever conditions happen to be present in a kitchen. Industrial microbial production, by contrast, takes place in purpose-built vessels called fermenters or bioreact…

Every day, cities and towns generate vast volumes of wastewater -- sewage -- carrying human excreta, food waste, detergents, and other organic and inorganic material washed down drains and toilets.

Biogas is a mixture of gases -- predominantly methane, along with carbon dioxide, hydrogen and hydrogen sulphide -- produced when organic waste is broken down by microorganisms in the absence of oxyge…

For much of the twentieth century, protecting crops from insect pests and disease-causing pathogens relied heavily on synthetic chemical pesticides and fungicides.

Biofertilisers are living organisms -- bacteria, fungi or cyanobacteria -- that, when applied to seeds, plant roots or soil, increase the availability of essential plant nutrients, most importantly ni…

An antibiotic is a chemical substance, produced by one microorganism, that is capable of inhibiting the growth of, or directly killing, another microorganism.

Antibiotics are powerful, often life-saving medicines, but their benefit depends heavily on being used correctly.

Microorganisms, though most familiar to the public as agents of disease, are overwhelmingly beneficial, and human societies -- long before understanding the underlying biology -- have exploited their…

Sample papers and previous-year board questions for this subject.