The 15 one-mark questions from the Supplementary 2021 12th Standard Zoology public exam, in paper order, with the correct option marked and a short explanation.
Q1
The golden age of reptiles was :
- A. Paleozoic era
- B. Mesozoic eraCorrect
- C. Proterozoic era
- D. Cenozoic era
Explanation. Reptiles, especially dinosaurs, dominated the Earth during the Mesozoic era, so it is called the golden age of reptiles.
Q2
In embryo transfer technique, ________ celled blastomere is transferred into the uterus.
- A. more than 5
- B. more than 8Correct
- C. less than 5
- D. less than 8
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.
Q3
Which of the following is the correct sequence of events with reference to the central dogma ?
- A. Duplication, Translation, Transcription
- B. Transcription, Translation, Replication
- C. Replication, Transcription, TranslationCorrect
- D. Transcription, Replication, Translation
Explanation. Central dogma: DNA replicates itself (replication), DNA is copied into mRNA (transcription), and mRNA is decoded into protein (translation).
Q4
The process which the sperm undergoes before penetrating the ovum is :
- A. Spermiogenesis
- B. Spermiation
- C. CapacitationCorrect
- D. Cortical reaction
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.
Q5
According to Alexander Von Humboldt, species - area relationship is log S = log C + Z log A, where 'Z' is :
- A. Y-intercept
- B. Species richness
- C. Slope of the lineCorrect
- D. Area
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).
Q6
Animals that can move from freshwater to seawater are called as :
- A. CatadromousCorrect
- B. Stenothermal
- C. Anadromous
- D. Eurythermal
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.
Q7
Allergy involves :
- A. IgA
- B. IgECorrect
- C. IgM
- D. IgG
Explanation. IgE antibodies bind to mast cells and basophils; on re-exposure to the allergen they trigger histamine release, causing allergic reactions.
Q8
The mode of reproduction in bacteria is by :
- A. ConjugationCorrect
- B. Formation of gametes
- C. Zoospore formation
- D. Endospore formation
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.
Q9
XO type of sex determination and XY type of sex determination are examples of :
- A. Male heterogametyCorrect
- B. Female heterogamety
- C. Male homogamety
- D. Both (b) and (c)
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.
Q10
Who proposed the 'Germplasm theory' ?
- A. Lamarck
- B. Darwin
- C. Alfred Wallace
- D. August WeismannCorrect
Explanation. August Weismann proposed the germplasm theory, stating that changes in somatic cells are not inherited; only changes in the germplasm are passed on.
Q11
Which one of the following is used to lower blood cholesterol level ?
- A. Clot buster
- B. Cyclosporin A
- C. StatinsCorrect
- D. Tetracycline
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.
Q12
Which one of the following method is not used in biomedical waste disposal ?
- A. Autoclaving
- B. Incineration
- C. Encapsulation
- D. Recycle and reuseCorrect
Explanation. Biomedical waste is infectious, so it is treated by autoclaving, incineration or encapsulation; it is not recycled and reused.
Q13
Vaccines that use components of a pathogenic organism rather than the whole organism are called :
- A. DNA vaccines
- B. Subunit recombinant vaccinesCorrect
- C. Conventional vaccines
- D. Attenuated recombinant vaccines
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.
Q14
The sporozoites of Plasmodium vivax are formed from :
- A. OocystsCorrect
- B. Gametocytes
- C. Spores
- D. Sporoblasts
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.
Q15
What is the sex of Drosophila which possess 2A + XXY chromosomes ?
- A. Triploid female
- B. Diploid femaleCorrect
- C. Triploid intersex
- D. Diploid male
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.
