MPPSC Previous Year ( PYQ )

A keystone species is an organism whose role in an ecosystem has a disproportionately large effect on the environment relative to its own abundance. Its removal can cause dramatic, cascading changes that lead to a decrease in biodiversity and a drastically different ecosystem, or even the ecosystem's collapse. The concept was introduced by zoologist Robert T. Paine in 1969, comparing the species to the wedge-shaped stone at the apex of an arch, which holds the entire structure together Examples of keystone species include the sea otter, which controls sea urchin populations to allow kelp forests to thrive; the beaver, which builds dams to create wetlands; the wolf, a predator that regulates other animal populations; and the African elephant, which maintains grasslands by controlling tree growth.

(c) Sleeping sickness Sleeping Sickness (Human African Trypanosomiasis): Caused by microscopic parasites of the species Trypanosoma brucei and is transmitted to humans through the bite of infected Tsetse flies (Glossina species), not mosquitoes. Other options (a) Dengue fever: Caused by the Dengue virus and transmitted by day-biting Aedes aegypti mosquitoes. It causes high fever, severe joint/muscle pain, and a sharp drop in blood platelets. (b) Filariasis: Caused by microscopic roundworms (mainly Wuchereria bancrofti) and spread by Culex mosquitoes. The parasites block the lymphatic system, causing extreme limb swelling (Elephantiasis). (d) Malaria: Caused by protozoan parasites (genus Plasmodium) and transmitted by female Anopheles mosquitoes. It attacks red blood cells, causing severe periodic fever with chills and anemia.

UPPCS 2021

Option (A) - Parietal cell - Correct Parietal cells, also called oxyntic cells, are present mainly in the glands of the fundus and body of the stomach. They secrete hydrochloric acid (HCl) into the stomach lumen. HCl creates the highly acidic environment required for the conversion of pepsinogen into pepsin and helps in the digestion of proteins. Parietal cells also secrete intrinsic factor, which is essential for the absorption of vitamin B₁₂ in the ileum. Therefore, Option (A) is correct. Option (B) - Peptic cell - Incorrect Peptic cells, also called chief cells, are present in the gastric glands and primarily secrete pepsinogen, the inactive precursor of the enzyme pepsin. Pepsinogen is subsequently activated into pepsin in the acidic environment created by HCl. Thus, chief/peptic cells are involved in protein digestion, but they are not responsible for secreting HCl. Hence, Option (B) is incorrect. Option (C) - Goblet cell - Incorrect Goblet cells are mucus-secreting cells found mainly in the intestinal and respiratory epithelium. In the digestive tract, they produce mucus that helps lubricate and protect the epithelial surface from mechanical and chemical damage. They are not the cells responsible for HCl secretion in the stomach. Therefore, Option (C) is incorrect. Option (D) - Mucous neck cell - Incorrect Mucous neck cells are found in the neck region of gastric glands and secrete mucus. This mucus contributes to protection and lubrication of the stomach lining, helping protect the gastric epithelium from the acidic gastric contents. However, they do not secrete hydrochloric acid. HCl is secreted by parietal cells. Therefore, Option (D) is incorrect.