General Science Questions (MCQs) for Competitive Examinations

Notes:
Fluorine is the element that is associated with teeth disorder because the presence of sodium fluoride in drinking water at the level of 2ppm may cause mottled enamel in teeth, skeletal fluorosis, and may be associated with cancer and other diseases. However, topically applied fluoride (toothpaste, dental rinses) has been shown to help reduce dental caries.

Notes:
The plastid is a major double-membrane organelle found in the cells of plants. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. Plastids often contain pigments used in photosynthesis, and the types of pigments present can change or determine the cell’s colour.

Notes:
Smallpox was one of the world’s most devastating diseases known to humanity. The last known natural case was in Somalia in 1977. It was declared eradicated in 1980 following a global immunization campaign led by the World Health Organization. Smallpox is caused by infection with the variola virus.

Notes:
Cyanobacteria, also known as blue green algae, are single-celled and belong to the family of Prokaryotes. That means, they do not have a well defined cell nucleus. The ability of cyanobacteria to perform oxygenic photosynthesis is thought to have converted the early reducing atmosphere into an oxidizing one, which dramatically changed the composition of life forms on Earth by stimulating biodiversity and leading to the near-extinction of oxygen-intolerant organisms.

Notes:
While fertilization is necessary for organisms that reproduce sexually, individuals that reproduce asexually?do so without the need for fertilization. These organisms produce genetically identical copies of themselves through?binary fission, budding, fragmentation, parthenogenesis, or other forms of asexual reproduction.

Notes:
Chameleons have specialized cells, chromatophores, which contain pigments in their cytoplasm, in three layers below their transparent outer skin. Dispersion of the pigment granules in the chromatophores sets the intensity of each color. Chromatophores contain pigments and reflect light, which are responsible for creating coloration. In chameleons, there are four types of chromatophores: xanthophores, erythrophores, iridiophores, and melanophores (Cooper and Greenberg, 1992).

Notes:
Cuscuta (Dodder) is a genus of about 100-170 species of yellow, orange or red (rarely green) parasitic plants. Dodders are supremely adapted for a life of plunder and pillage. Reduced in form to scrambling and twining threads, they appear to be completely leafless, although closer inspection reveals tiny scale leaves pressed close to the stems. So, it is a stem parasite.

Notes:
The Rock Dove (Columba livia) or Rock Pigeon, is a member of the bird family Columbidae (doves and pigeons). In common usage, this bird is often simply referred to as the “pigeon”. The species includes the domestic pigeon (including the fancy white pigeon).

Notes:
Bile or gall is a dark green to yellowish brown fluid, produced by the liver that aids the digestion of lipids in the small intestine. It neutralizes the acid in food to provide the alkaline conditions needed in the small intestine. Besides, it breaks down large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This process is known as emulsification of fats. It does not convert proteins into amino acids.

Notes:
Cause of night blindness is a deficiency of retinol, or vitamin A, found in fish oils, liver, dairy products, vegetable and fruits yellow in colour. Nyctalopia also called “Night Blindness” is a condition making it difficult or impossible to see in relatively dim light. To over come deficiency of vitamin-A, one needs to feed of food products rich in carotene which is used in synthesis of vitamin-A is liver.