Biology MCQs

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The pituitary gland or hypophysis is located in one of the bones at the base of the skull. It has two portions viz. anterior hypophysis and posterior hypophysis.
The anterior part produces two hormones that work directly viz. growth hormone (GH) and prolactin; and four tropic hormones {tropic hormones regulate the other endocrine glands} viz. adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
The posterior part releases two hormones produced in the hypothalamus viz. oxytocin and antidiuretic hormone (ADH or vasopressin).

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Viruses are small infectious agents that can replicate only inside the living cells of an organism. Viruses are classified based on the type of genetic material they contain. Some viruses have DNA as their genetic material, while others have RNA. Some viruses have both DNA and RNA as their genetic material.

DNA viruses have double-stranded DNA as their genetic material. They replicate their DNA using the enzymes and machinery of the host cell. Examples of DNA viruses include herpes viruses, pox viruses, and adenoviruses.

RNA viruses have single-stranded RNA as their genetic material. They replicate their RNA using the enzymes and machinery of the host cell. Examples of RNA viruses include influenza viruses, HIV, and coronaviruses.

Viruses that have both DNA and RNA as their genetic material are known as “retroviruses.” These viruses contain a single strand of RNA, but they use an enzyme called reverse transcriptase to convert their RNA into DNA. The DNA is then integrated into the host cell’s genome and replicated along with the host cell’s DNA. Examples of retroviruses include HIV and the human T-cell leukemia virus.

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Cloaca which is the posterior opening that serves as the only such opening for the intestinal, reproductive and urinary tracts is present in Aves, Amphibians and Reptiles. A cloaca is not present in placental mammals.

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In context with the connective tissues, ligaments connect join Bones to Bones. It is also known with the name of articular ligament, articular larua, fibrous ligament, or true ligament.

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The correct sequence of the evolution would be Monotremes, Marsupials and Eutheria. Since, Whale is in subclass Eutheria, it is the latest in the evolution. So the correct sequence is Echidena (Monotreme), Kangaroo (Marsupials) & Whale (Eutheria).Echidna  are the only surviving members of the Monotremata order and are the only living mammals that lay eggs.

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Diabetes mellitus occurs when the body does not produce insulin (type I) or when the body does not respond properly to insulin (type II). This results in elevated blood glucose. In either type, overtreatment, or failure to eat properly while on treatment, can lead to hypoglycemia. Most diabetics recognize their symptoms when “low” and know to go eat something before it progresses to a dangerous point. Symptoms of high blood sugar are much different – thirst, increased urination, sleepiness.

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Metaxylem is the part of the primary xylem that differentiates after the protoxylem and that is distinguished typically by broader tracheids and vessels with pitted or reticulate walls.

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Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin. All species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual’s ability to compete, survive, and reproduce.
Darwin’s evolutionary theory of natural selection gave a more rational explanation of the formation of new species. As per natural selection, various species originated from a single species as a result of adaptation to the changing environment.
Natural selection takes place in four different ways as follows:
• Variation – The changes accumulated over a period of time in an organism usually gives rise to a new species.
• Inheritance – It is the passing on of the variations over generations which ultimately lead to speciation.
• A high rate of growth of population – This gives rise to more number of organisms being reproduced by a species than the environment can support which might lead to the extinction of that particular species.
• Differential survival and reproduction – The superior variations lead to survival of a particular organism and the inferior or negative variation leads to extinction. The superior variations are the ones inherited during reproduction.

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Under suitable conditions, a single cell grows into a colony of cells on agar medium. The resulting population of genetically identical cells derived from a single parent cell is called a clone.

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A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances. Microorganisms that form biofilms include bacteria, fungi and protists. One common example of a biofilm dental plaque, a slimy buildup of bacteria that forms on the surfaces of teeth.