Science Online Quiz Class - 8

AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV). It is a viral infection that attacks the immune system.

Streptomycin is a well-known antibiotic used to treat various bacterial infections. Sodium bicarbonate is a base, and 'Compose' is not a medical term for an antibiotic.

Yeast is a fungus used in the fermentation process to produce alcohol and carbon dioxide, which is essential for making wine and bread. Since all listed items relate to this process, 'All of these' is the correct choice.

Houseflies are common mechanical carriers of pathogens because they land on waste and then on food, transferring bacteria and other microorganisms.

Anthrax is a serious infectious disease caused by the bacterium Bacillus anthracis. The other options are either beneficial bacteria or different types of organisms.

Rust in plants, such as wheat rust, is a disease caused by parasitic fungi. It is not caused by viruses, bacteria, or protozoa.

Amoeba is often cited as one of the simplest protozoa due to its simple, unicellular structure and lack of complex organelles compared to others like Paramecium or Euglena.

Penicillin was the first true antibiotic, discovered by Alexander Fleming from the fungus Penicillium notatum.

Viruses are considered to be on the border between living and non-living because they require a host cell to replicate but are inert outside of one.

Smallpox is a highly contagious disease caused by the variola virus. It is a classic example of a viral disease.

The formation of curd from milk is a fermentation process driven by lactic acid bacteria. The other terms are unrelated to this biological process.

Rhizobium, Azotobacter, and Cyanobacteria are all known for their ability to fix atmospheric nitrogen into a form plants can use. Therefore, 'All of these' is correct.

Salt, sugar, and oil are all commonly used as food preservatives to inhibit the growth of microorganisms. Thus, 'All of these' is the correct answer.

Lactobacillus (also spelled Lactobacillus) are bacteria that help in curdling milk by producing lactic acid. Rhizobium fixes nitrogen in legumes, Vibrio cholerae causes cholera, and E. coli is an intestinal bacterium.