General Science Questions (MCQs) for Competitive Examinations

Notes:
The smallest bone in the human body is the stapes. The stapes is one of three small bones in the middle ear that allow mammals to transmit sound waves through their eardrum and hear. The stape bone is also known as the stirrup bone because it is shaped like a stirrup.

Notes:
Interbreeding destroys the genetic integrity of a species, causing it to become progressively infertile or extinct, evolutionary changes in anatomy and biology developed to prevent interbreeding between species. The specific term is Reproductive Isolation, which acts to prevent some, any, or all stages of reproduction from occurring. Reproductive Isolation is very important in keeping animal species separated.

Notes:
Sex determination in human beings depends on the particular pair of sex chromosomes an individual inherits. The homogametic sex, females, usually possess two identical sex chromosomes (XX). On the other hand, males, who are the heterogametic sex, typically present a pair of different sex chromosomes (XY). This distinct pair forms the blueprint that directs male physical and biological characteristics development.

Notes:
An insect is an organism having three pairs of jointed legs. Insects are small, land-dwelling arthropods. It has three distinct body sections : the head, thorax and abdomen. It has one pair of antennae (comprising the scapele, pedicel and flagellum), compound eyes and often one or two pairs of wings.

Notes:
Fertilization in plants is not directly influenced by sunlight. Fertilization occurs after pollination, when pollen grains land on the stigma of a flower of the same species. During this time, a series of events take place leading to the formation of seeds. However, none of these event is affected by presence or absence of light.

Notes:
Some plants have the stem branching out near the base. The stem is hard but not thick. Such plants are called shrubs. Eg: Rose plant. Shrubs have persistent woody stems above the field, unlike herbaceous plants. Shrubs may be evergreen or deciduous. By their numerous stems and shorter height, less than 6 m-10 m long, they are distinguished from trees.

Notes:
Microorganisms or decomposers such as bacteria and fungi help in the process of recycling of nutrients by decomposing various dead organisms such as plants and animals to form humus. Humus is highly nutritious and rich in minerals and microbes vital for healthy plant growth.

Notes:
Alveoli are an important part of the respiratory system whose function it is to exchange oxygen and carbon dioxide molecules to and from the bloodstream. These tiny, balloon-shaped air sacs sit at the very end of the respiratory tree and are arranged in clusters throughout the lungs. Alveoli are tiny balloon shaped structures and are the smallest passageway in the respiratory system.

Notes:
The deficiency of magnesium leads to yellowish green blotch near the base of the leaf between the midrib and the outer edge (chlorosis). The yellow area enlarges until the only green remaining is at the tip and base of the leaf as an inverted V-shaped area on the midrib.

Notes:
The constituents of phloem are Sieve tubes, Companion cells, Phloem parenchyma, Phloem fibres. Tracheids are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts. These are elongated narrow tube like cells with hard thick and lignified walls with large cell cavity.