All Free Biology MCQs with Answers

• A. Crossing of two inbred parental lines
• B. Harvesting seeds from the most productive plants
• C. Inducing mutations
• D. Bombarding the seeds with DNA.

Explanation: Hybridisation or heterosis or hybrid vigour is defined as the superiority of hybrid over parents. It has been commercially exploited in different commercial crops like maize, sorghum, bajra, etc. The main steps include: selection of parents, selfing of parents, emasculation, bagging, crossing of desired and selected parents and finally seed setting and harvesting.

• A. Highly prone to pests
• B. Low in yield
• C. Free from intraspecific competition
• D. Characterized by a poor root system.

Explanation: Monoculture describes systems that have very low diversity. Monoculture is the destruction of a diverse ecosystem and replacement with a single species or crop. It depletes the soil, fruits and vegetables become more susceptible to pests and more diseases than those grown in a diverse crop environment, thus requiring larger amount of chemical spray.

• A. Barley
• B. Rye
• C. Pearl millet
• D. Sugarcane.

Explanation: Triticaleis, the first man-made cereal or crop, has been produced by intergeneric hybridization between common wheat (Triticum aestivum) and European rye (Secale cereale) with a view to combine characters of these two parent plants. Triticale is hexaploid, i.e, 2n = 6x = 62 (when tetraploid wheat is used) or octoploid,i.e., 2n = 8x = 56 (when hexaploid wheat is used). Triticale or Triticosecale is not suitable for the purpose of bread making due to low gluten content, but it is a good forage crop.

• A. Wheat, rice and maize
• B. Wheat, rice and barley
• C. wheat, maize and sorghum
• D. Rice, maize and sorghum.

Explanation: Most important source of food in the world are cereals. They are a rich source of carbohydrates, present in endosperms which is the edible portion in cereals. Wheat, corn and rice contribute to about two thirds of the total world's food. Rice alone is the staple food of 60% of the world population and more than 50% of Indians. Wheat is the world's most widely cultivated crop. Maize is an important Kharif crop of India and also contributes to food production.

• A. X­-rays
• B. UV (260 nm)
• C. Gamma rays (from cobalt­-60)
• D. Alpha particles

Explanation: Gamma rays are produced when an unstable atomic nucleus like cobalt­-60 releases energy to gain stability. Sharbati Sonora and Pusa Lerma are the two important varieties of wheat that are responsible for the green revolution in India. These are produced by gamma rays treatment of Sonora­-64 and Lerma Rojo­-64 which are Mexican dwarf wheat varieties.

• A. Goat
• B. Sheep
• C. Goat­-sheep cross
• D. Kashmir sheep­-Afghan sheep cross

Explanation: Pashmina refers to a type of cashmere wool and textiles made from it. This wool comes from a special breed of goat indigenous to high altitudes of the Himalayan mountains. The Himalayan mountain goat, Capra hircus, sheds its winter coat every spring and the fleece is caught on thorn bushes. One goat sheds approximately 3­-8 ounces of the fibre.

• A. Plantlet culture
• B. Organ culture
• C. Micropropagation
• D. Macropropagation.

Explanation: Micropropagation is the latest method of obtaining a large number of plantlets from plant tissue culture. It is called micropropagation because of the minute size of the propagules. It involves repeated subculture of the explant by changing the medium so as to form a large number of plantlets from that single explant. Somatic embryogenesis i.e., developing embryos from somatic cells is one of the techniques of micropropagation.

• A. Triploid
• B. Tetraploid
• C. Diploid
• D. Monoploid.

Explanation: Colchicine is an alkaloid extracted from the seed and corm of Colchicum autumnale. It has the property of arresting and breaking the spindle so that cell division without cell wall formation may be affected leading to doubling of chromosome number. So a diploid cell will become tetraploid by chromosome doubling.

• A. Cellular totipotency
• B. organogenesis
• C. Double fertilization
• D. Test tube culture.

Explanation: Totipotency refers to the capacity of each living cell of a multicellular organism being capable of independent development when provided with suitable conditions. Guha and Maheshwari (1966) cultured anthers of Datura. The haploid pollen grain inside the anther divides to form a multicellular mass of cells called callus. Using varying quantities of auxins and cytokinins in the culture medium, this callus is differentiated into embryoids which later germinates to form the entire plant.

• A. Oat
• B. Barley
• C. Maize
• D. Rye.

Explanation: Triticale is the first man made cereal or crop, which has been produced by intergeneric hybridization between common wheat (Triticum aestivum) and European rye (Secale cereale) with a view to combine characters of these two parent plants. Triticale is hexaploid, i.e, 2n = 6x = 62 (when tetraploid wheat is used) or octoploid,i.e., 2n = 8x = 56 (when hexaploid wheat is used).Triticale or Triticosecale is not suitable for purpose of bread making due to low gluten content, but it is a good forage crop.