General Science Questions (MCQs) for Competitive Examinations

Notes:
Genes are a part of the chromosome and are found in pairs in somatic cells. One member of the gene pair segregates into a gamete, thus each gamete only carries one member of the gene pair. Gametes unite at random and irrespective of the other gene pairs involved in pairing during zygotene of meiosis-I.

Notes:
The carrot gets its characteristic and bright orange colour from ?-carotene, which is partly metabolised into vitamin A in liver of humans. Carotene is responsible for the orange colour of carrots and many other fruits and vegetables. Carotene is an orange photosynthetic pigment important for photosynthesis.

Notes:
Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland. It plays vital roles in digestion, heart and muscle function, brain development and maintenance of bones. It increases heart rate, cardiac contractility and cardiac output and also promotes vasodilation, which leads to enhanced blood flow to many organs.

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Fertilization is the process of fusion of the male and the female gametes. This can occur either inside (internal fertilization) or outside (external fertilization) the body of the female. Humans provide an example of the former whereas seahorse reproduction is an example of the latter.

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Pyria, or periodontal disease, is a progressive gum disease characterized by inflammation resulting from the toxins found in plaque. It leads to bleeding of the gums. If allowed to progress, Pyria begins to destroy underlying tissue, which may eventually lead to premature tooth loss.

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According to the K+ ion theory the guard cells absorb K+ ions from the cells around them as they produce ATP (due to photosynthesis) and become hypertonic. This leads to absorption of water from nearby cells by endosmosis due to which the guard cells become turgid and the stomata opens. Decreasing light intensity and photosynthesis causes Stomatal closing.

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.

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Eutrophication is the ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage. It leads not only to increased levels of nutrients, but increased Biological Oxygen Demand as well following the decay of algal bloom in stagnant water reservoirs.

Notes:
Chlorophyll, a photo-receptive pigment, allows plants to absorb sunlight. Chlorophyll is a chlorine pigment, which is structurally similar to and produced through the same metabolic pathway as other porphyrin pigments such as heme. At the center of the chlorine ring is a magnesium ion. The molecular formula of C55H70O6N4 Mg. Hence, chlorophyll as a pigment lacks calcium.

Notes:
Plaster of Paris is a plaster made by calcining gypsum.
CaSO4•1/2?H2?O.
It can be used to impregnate gauze bandages to make a sculpting material called modroc. It is used to make classic plaster orthopedic casts to protect limbs with broken bones.