12th Standard Zoology Supplementary 2021: Online Practice Test

Explanation. Reptiles, especially dinosaurs, dominated the Earth during the Mesozoic era, so it is called the golden age of reptiles.

Explanation. In ZIFT the zygote or early embryo with up to 8 blastomeres is transferred into the fallopian tube, whereas in intra uterine transfer (IUT) an embryo with more than 8 blastomeres is transferred into the uterus.

Explanation. Central dogma: DNA replicates itself (replication), DNA is copied into mRNA (transcription), and mRNA is decoded into protein (translation).

Explanation. Sperms become capable of fertilising the ovum only after capacitation in the female reproductive tract; the cortical reaction occurs in the ovum after sperm entry.

Explanation. In log S = log C + Z log A, S is species richness, A is area, C is the Y-intercept and Z is the slope of the line (regression coefficient).

Explanation. Catadromous animals (e.g. freshwater eels) migrate from freshwater to the sea to breed; anadromous animals (e.g. salmon) migrate from the sea to freshwater.

Explanation. IgE antibodies bind to mast cells and basophils; on re-exposure to the allergen they trigger histamine release, causing allergic reactions.

Explanation. Among the given options, conjugation is the (parasexual) reproductive process in bacteria, in which genetic material passes between two cells through a conjugation tube; bacteria do not form gametes or zoospores, and endospores are resting structures for survival.

Explanation. In both XO (e.g. grasshopper) and XY (e.g. human) systems the male produces two kinds of gametes, so they are examples of male heterogamety.

Explanation. August Weismann proposed the germplasm theory, stating that changes in somatic cells are not inherited; only changes in the germplasm are passed on.

Explanation. Statins, produced by the yeast Monascus purpureus, inhibit the enzyme needed for cholesterol synthesis and lower blood cholesterol; streptokinase is a clot buster and cyclosporin A is an immunosuppressant.

Explanation. Biomedical waste is infectious, so it is treated by autoclaving, incineration or encapsulation; it is not recycled and reused.

Explanation. Subunit recombinant vaccines contain only antigenic components (such as proteins) of the pathogen, e.g. the hepatitis B vaccine, instead of the whole organism.

Explanation. In the mosquito's stomach wall the zygote (ookinete) becomes an oocyst, and the oocyst divides to release thousands of sporozoites that migrate to the salivary glands.

Explanation. By Bridges' genic balance theory, X : A = 2 : 2 = 1.0 gives a female; the Y chromosome does not decide sex in Drosophila, and two autosome sets make it diploid, so 2A + XXY is a diploid female.