General Science Questions (MCQs) for Competitive Examinations

Notes:
Bulbs are modified stems of some plants. The stem is modified to be a storage organ where the plant stores its reserve materials which it would use in times of need. It has a modified flower bud or other growth point that is surrounded by modified, fleshy leaves that are referred to as scales. Onion is the best example of bulb.

Notes:
Oxygen liberated during photosynthesis comes from the splitting or hydrolysis of water in the green plants. Cornelius van Niel experimentally proved for the first time that the oxygen liberated during photosynthesis comes from water and not from carbon dioxide. Oxygen is expelled out of plants and Hydrogen is used to reduce Carbon dioxide to produce carbohydrates.

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:
The organs which have different basic structure and origin abut are similar in their appearance and functioning, are called analogous organs. An example of analogous organs are the wings of insects, bats and birds that evolved independently in each lineage separately after diverging from an ancestor without wings.

Notes:
Ornithophily refers to the pollination of flowering plants by birds. Birds involved in ornithophily tend to be specialist nectarivores with brushy tongues and long bills, that are either capable of hovering flight or light enough to perch on the flower structures.

Notes:
All mammals and birds are warm-blooded while all reptiles, arachnids, insects, amphibians, fish are coldblooded. Therefore, all primates (such as humans, apes, and monkeys), cats (tigers, cheetahs, and domestic cats), rodents (rats, beavers, and chipmunks), marsupials (kangaroo), weasels (badgers and meerkats), monotremes (platypuses), sea mammals (whales, seals, walruses, manatees, and dolphins), dogs, pigs, and elephants are warm-blooded.

Notes:
Palisade parenchyma is the layer of tissue directly beneath the epidermis of the upper surface of a leaf. It contains the cylinder-shaped cells that hold the chloroplasts and constitutes the primary area of photosynthesis that converts the light energy to the chemical potential energy of carbohydrates.

Notes:
A goitre, or goiter, is a swelling in the neck resulting from an enlarged thyroid gland. A goitre can be associated with a thyroid that is not functioning properly. Worldwide, over 90% of goitre cases are caused by iodine deficiency. The term is from the Latin gutturia, meaning throat.

Notes:
The bee hummingbird, also known as Helena hummingbird, is a species of hummingbird which is the world’s smallest bird. Females weigh 2.6 g and are 6.1 cm long, and are slightly larger than males, with an average weight of 1.95 g and length of 5.5 cm. As its name suggests, it is scarcely larger than a bee. It is endemic to Cuba and the Isla de la Juventud.

Notes:
As exercise commences pulmonary ventilation (breathing) increases in direct proportion to the intensity and metabolic needs of the exercise. During heavy exercise, breathing rate in an average adult person can increase upto 25 per minute.