Zoology

Klinefelter’s syndrome is a genetic disease of males where cells contain an additional X chromosome, resulting in tall, thin anatomy and small unfertile testes. Gynaecomastia is the typical feature.

Ovulatory phase is the shortest phase in women menstrual cycle when mature egg is discharged from ovarian follicles into oviduct. It begins on day 12 of the cycle and lasts for 2 days.

Anal style is present only in male cockroaches. It is not present in female cockroaches.

Ball & socket joint is present between humerus bone & pectoral girdle where ball-shaped surface fits into cup-like depression of different bone.

Aldosterone is used to activate epithelial mineralocorticold receptors and its pathologic nature on cardiovascular system through mineralocorticold receptors in heart and blood vessels.

Heroin is an opioid drug which is also illegal, extremely addictive. It is derived from morphine.

People having osteoporosis gradually become thin & feeble due to decrease of bone mass & degeneration of bone tissue.

Salamanders are amphibians which look like lizard but their skin lack scales, have four limbs & an elongated tail. Some of the species are either totally aquatic or terrestrial. Ostriches are largest & bulky birds, they are flightless & possess powerful legs for running at speed even 50km/hr. Snakes are limbless reptiles, which help them in underground movements & swimming in water more easily. Sharks are cartilaginous fishes because they do not have swim bladder for breathing & have to move in water to breathe so their body must be lighter, which is why they are composed of cartilages instead of bones. Lampreys are jawless most ancient ancestors of vertebrates characterized by notched funnel-like suctorial mouth.

Gene mutations or point mutations are changes in the structure of gene. Since genes are DNA segments, the gene mutations include changes in the number or arrangement of nucleotides. These are also known as ‘intragenic mutations’. Gene mutations alter or modify the information conveyed by the gene. Lethal, albinos, chlorophyll deficiencies, sickle cell anaemia, etc., are caused by gene mutations.

Parasitism is more difficult to describe. However a parasite defines an organism which is in continues intimate association with other organism called host upon which it is metabolically dependent directly or indirectly. Commensalism considered as a loose association in which two animals of different species lived together without being either metabolically dependent on one or both organisms may receive some benefits from the association. Predation is a type of symbiotic association between two different organisms where one acts as predator that seizes & feeds on other organism which acts as prey. Mutualism is an association between two organisms of two different species where both organisms are benefited from the relationship. Competition is an association between organisms for resources like food, shelter and so on where both may causes harm to each other.

Induced mutations are introduced artificially or experimentally. Any physical or chemical agent, which introduces mutation is called a mutagen or mutagenic agent, physical (high or low temperature and the radiations) and chemical mutagens (mustard gas, colchicines, acridine dyes, nitrous acid, etc).

In centrolecithal eggs the cleavage remains restricted to the periphery cytoplasmic region,  which is called superficial cleavage. E.g, Arthropods, mainly insects.

In mesolecithal and telolecithal eggs due to polarization of yolk holoblastic cleavage produces unequal size blastomere including micromeres [small size blastomere] and macromere [large size] is called unequal holoblastic cleavage. E.g, lower fishes and amphibians.