12th Standard Zoology March 2025: Online Practice Test

Explanation. Swelling, redness, heat and pain at the site of tissue injury or infection form the inflammatory response, a part of innate immunity.

Explanation. Nirenberg and Matthaei used poly-U synthetic RNA, which produced polyphenylalanine; so UUU, coding for phenylalanine, was the first codon deciphered.

Explanation. Klinefelter’s syndrome (44A + XXY) occurs in males, not females; the other three pairs are correct.

Explanation. Neanderthal man had a brain capacity of about 1400 cc; 650-800 cc is Homo habilis and about 900 cc is Homo erectus.

Explanation. Syphilis (Treponema pallidum), chlamydiasis (Chlamydia trachomatis) and gonorrhoea (Neisseria gonorrhoeae) are all bacterial; trichomoniasis is protozoan, candidiasis fungal and pediculosis caused by lice.

Explanation. ELISA (Enzyme Linked Immunosorbent Assay) detects antigens or antibodies, so it is mainly used to diagnose infections by detecting pathogens such as HIV.

Explanation. Prolactin from the anterior pituitary initiates and maintains milk secretion (lactation); oxytocin only causes milk ejection.

Explanation. Tropical regions have stable, congenial seasons, temperature, humidity and photoperiod, which promote niche specialisation and speciation; so both statements are true and the reason explains the assertion.

Explanation. In A the internal level rises with the external level (conformer); in B the internal level stays constant (regulator); C conforms up to a point and then regulates (partial regulator).

Explanation. Bacteria do not form gametes; genetic material is exchanged between two cells through conjugation, which is regarded as their sexual mode of reproduction.

Explanation. The National Biodiversity Authority, set up in 2003 under the Biological Diversity Act, 2002, has its headquarters in Chennai.

Explanation. An operon is a cluster of functionally related structural genes controlled together by a common promoter and operator, e.g. the lac operon.

Explanation. The fungus Aspergillus niger is used for the industrial production of citric acid.

Explanation. The thickness of the ozone layer is expressed in Dobson units (DU); 1 DU is a 0.01 mm thick layer of pure ozone at standard temperature and pressure.

Explanation. When RBCs infected by Plasmodium rupture, the toxin haemozoin is released, causing the chill and high fever of malaria.