General Science Questions (MCQs) for Competitive Examinations

Notes:
Phototropism is the growth of organisms in response to light. In plants, phototropism is a response to blue wavelengths of light and is caused by a redistribution of auxin from the illuminated side to the darker side of the shoot, resulting in quicker growth on the darker side and bending of the shoot toward the source of light.

Notes:
Methane (CH4) is a greenhouse gas and causes warming the same way that CO2 does. It absorbs radiation emitted from the surface and re-emits that radiation in all directions with some of the radiation returning to the surface where it is absorbed and converted to heat. In the first two decades after its release, methane is 84 times more potent than carbon dioxide.

Notes:
‘Survival of the fittest’ is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection. Herbert Spencer first used the phrase, after reading Charles Darwin’s On the Origin of Species, in his Principles of Biology (1864), in which he drew parallels between his own economic theories and Dar-win’s biological ones.

Notes:
True berries, such as blueberries and cranberries have seeds inside. The strawberry, however has its dry, yellow “seeds” on the outside (each of which is actually considered a separate fruit). The “seeds” seen on the outside of a strawberry are actually the plant’s ovaries and are called “achnes.”

Notes:
Beriberi is a disease caused by a vitamin B1 (thiamine) deficiency. There are two types of the disease: wet beriberi and dry beriberi. Wet beriberi affects the heart and circulatory system. In extreme cases, wet beriberi can cause heart failure. Dry beriberi damages the nerves and can lead to a loss of muscle strength and eventually, muscle paralysis.

Notes:
Root hairs are tubular-shaped tip-growing cells that arise from epidermal cells known as trichoblasts, behind the tips of young roots. Like all tip-growing cells, root hairs grow by the addition of cell wall precursors to the tip delivered by vesicles from the endomembrane system.

Notes:
Water is transported through the plant in Xylem vessels, these begin in the roots and end in the leaves of the plant. Water is transported through a combination of “Transpirational pull” and capillary action that produces root pressure.

Notes:
Vitamin C also known as ascorbic acid is found in citrus fruit such as orange, lemon, lime, grapefruit, grapes etc. It protects the immune system, reduces the severity of allergic reactions and helps fight off infections.

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.

Notes:
Deciduous trees and shrubs are plants that annually lose their leaves at the end of each growing season; usually during the winter, but can also occur during a dry season in warm climates. Common examples of deciduous trees include oak, maple, and hickory trees. Oak trees are characteristic deciduous trees that lose their leaves in the fall and regrow them in the spring.