The major greenhouse gas emitted from agricultural rice paddies is: MCQ with Answer and Explanation

Explanation:
The lac operon in E. coli is a classic example of an inducible operon. It is normally 'off' (repressed) because the lac repressor protein, produced by the 'i' gene, binds to the operator, preventing transcription of the structural genes (z, y, a) needed for lactose metabolism. However, when lactose is present in the environment, it is converted to allolactose, which acts as an inducer. Allolactose binds to the repressor, changing its shape and preventing it from binding to the operator, thus 'inducing' or allowing transcription to occur.

Explanation:
Bacillus is a genus of rod-shaped bacteria, placed in Kingdom Monera because they are prokaryotic. Euglena and Paramecium are unicellular eukaryotes in Kingdom Protista. Agaricus (mushroom) belongs to Kingdom Fungi. Monera includes all prokaryotes like bacteria, cyanobacteria, and archaea. They are characterized by absence of true nucleus and membrane-bound organelles.

Explanation:
Red tides are harmful algal blooms caused primarily by the rapid multiplication of certain marine dinoflagellates, such as Gonyaulax. These blooms discolor the water red or brown and release potent toxins (like saxitoxin) that can kill marine life and cause paralytic shellfish poisoning in humans who consume contaminated seafood. Cyanobacteria can cause freshwater blooms, but not marine red tides.