General Science Questions (MCQs) for Competitive Examinations

Notes:
Mercury belongs to the zinc group of elements in the periodic table, which comprises zinc, cadmium and mercury. They all have completely filled-up atomic orbitals. It becomes difficult to knock out these electron(s) from their orbitals and form metallic bonds. With its filled shell electron configuration it is very reluctant to form bonds even with other mercury atoms.

Notes:
Radon, a radioactive noble gas with atomic number 86, is used in radiotherapy. Created by disintegration of radium, its one of the heaviest gases and a health hazard. Radon gas, chemically inert yet radioactive, can accumulate in buildings and drinking water causing lung cancer. Furthermore, radon is noted for brilliant phosphorescence when cooled below its freezing point. Its most stable isotope, 222Rn, has a half-life of 3.8 days. Groundwater often has a higher 222Rn concentration than surface water due to less exposure to atmosphere.

Notes:
The chief cells of the stomach secrete enzymes for protein breakdown (inactive pepsinogen and rennin). Hydrochloric acid activates pepsinogen into the enzyme pepsin, which then helps digestion by breaking the bonds linking amino acids, a process known as proteolysis.

Notes:
Multicellular organisms are made up of more than one cell. The development of multicellular organisms is accompanied by cellular specialization and division of labor; cells become efficient in one process and are dependent upon other cells for the necessities of life. Paramecium is single-celled protists naturally found in aquatic habitats. Paramecium is the only genus in the family Parameciidae, which resides within the phylum Ciliophora.

Notes:
Turner syndrome is a rare chromosomal disorder characterized by partial or complete loss (monosomy) of one of the X chromosomes that affects females. Individuals with Turner syndrome have only 45 chromosomes, including just a single X chromosome. This monosomic has a chromosome complement of 44 autosomes and one X chromosome (44+XO). The abnormal condition probably originates from exceptional egg or sperm with no X chromosome.

Notes:
In menstrual cycle 19-21 days stands for the fertilizing period also called danger period. After ovulation on 14th day chances of contraption are at their highest with well developed endometrium for implantation. This is the time in the menstrual cycle when progesterone should be at its peak for the month and when estrogen should be at the height of its luteal plateau.

Notes:
Silk worms are the larva of a moth (Bombyx mori) native to Asia that spins a cocoon of fine, strong, lustrous fiber that is the source of commercial silk. Silkworms feed on the leaves of the mulberries (genus- Morus) and sometimes on the Osage orange (Maclura pomifera).

Notes:
New born babies and children normally breathe faster than older children and adults. Their respiratory rate is about 30-60 breaths per minute. The respiratory rate for the different age-categories of children is:-6-12 months: 24-30; 1-5 years: 20-30; 6-12 years: 12-20.

Notes:
Various components of blood are: Plasma, Erythrocytes (Red Blood Cells), Leucocytes (White Blood Cells) and Thrombocytes/Platelets. Monocytes, also known as macrophages, are the largest blood cells in most mammals, measuring 10-15 cm in diameter. They are leucocytes. Their nuclei are kidney-shaped and cytoplasm is abundant.

Notes:
Oviparous is a zoological term that refers to animals that lay eggs which then hatch externally. Oviparous animals may fertilize their eggs either externally or internally. Frogs are oviparous since they lay eggs, which then develop outside of the mother. Ovoviviparous animals are relatively uncommon, sharks are most well-known.