The 15 one-mark questions from the March 2024 12th Standard Zoology public exam, in paper order, with the correct option marked and a short explanation.
Q1
Colostrum is rich in :
- A. Ig D
- B. Ig E
- C. Ig M
- D. Ig ACorrect
Explanation. Colostrum, the first milk secreted after childbirth, is rich in IgA antibodies, which give the newborn passive immunity.
Q2
Without altering water quality, __________ is/are an ideal disinfectant used in waste water treatment.
- A. Boiling
- B. U-V raysCorrect
- C. Ozonisation
- D. Chlorination
Explanation. UV radiation kills microbes in treated waste water without adding any chemical or leaving residues, so it does not change the water quality, unlike chlorination or ozonisation.
Q3
The ovary remains attached with pelvic wall and the uterus by an ovarian ligament, called :
- A. myometrium
- B. ovarian stroma
- C. mesovariumCorrect
- D. tunica albuginea
Explanation. Each ovary is held to the pelvic wall and uterus by a ligament called the mesovarium. Myometrium is the muscular layer of the uterus, and ovarian stroma and tunica albuginea are parts of the ovary itself.
Q4
B cells are activated by :
- A. Interferon
- B. Complement
- C. AntigenCorrect
- D. Antibody
Explanation. B cells are activated when their receptors bind a specific antigen; they then form plasma cells that secrete antibodies. Antibodies are the product, not the activator.
Q5
A mRNA molecule is produced by :
- A. Duplication
- B. Replication
- C. Translation
- D. TranscriptionCorrect
Explanation. mRNA is synthesised from a DNA template by RNA polymerase in transcription. Replication copies DNA and translation uses mRNA to make protein.
Q6
The average foetal heart rate is :
- A. 120 - 160 beats/minuteCorrect
- B. 120 - 130 beats/minute
- C. 130 - 150 beats/minute
- D. 130 - 160 beats/minute
Explanation. A normal foetal heart rate, monitored with a foetoscope, lies between 120 and 160 beats per minute.
Q7
The wings of birds and butterflies is an example of :
- A. Divergent evolution
- B. Variation
- C. Convergent evolutionCorrect
- D. Adaptive radiation
Explanation. Wings of birds and butterflies do the same job (flight) but have different origins and structures; such analogous organs arise by convergent evolution.
Q8
Modern man belongs to which period ?
- A. QuaternaryCorrect
- B. Cambrian
- C. Cretaceous
- D. Silurian
Explanation. Modern man (Homo sapiens) appeared in the Quaternary period of the Cenozoic era; the other periods belong to the Palaeozoic and Mesozoic eras.
Q9
The most common substrate used in distilleries for the production of ethanol :
- A. MolassesCorrect
- B. Soyameal
- C. Cornmeal
- D. Groundgram
Explanation. Sugarcane molasses, a cheap sugar-rich by-product, is fermented by yeast (Saccharomyces cerevisiae) to produce ethanol in distilleries.
Q10
GEAC stands for :
- A. Genetic Engineering Approval CommitteeCorrect
- B. Genome Engineering Action Committee
- C. Genetic and Environment Approval Committee
- D. Ground Environment Action Committee
Explanation. GEAC is the Genetic Engineering Approval (now Appraisal) Committee of the Government of India, which decides on the use of genetically modified organisms.
Q11
Match the pathogens with respective diseases caused by them and select the correct match using the codes given below :
(A) Leishmania donovani — (i) Amoebiasis
(B) Wuchereria bancrofti — (ii) Kala-azar
(C) Trypanosoma gambiense — (iii) Sleeping sickness
(D) Entamoeba histolytica — (iv) Filariasis
- A. (A)-(iii), (B)-(i), (C)-(ii), (D)-(iv)
- B. (A)-(ii), (B)-(iv), (C)-(iii), (D)-(i)Correct
- C. (A)-(i), (B)-(iv), (C)-(iii), (D)-(ii)
- D. (A)-(ii), (B)-(iv), (C)-(i), (D)-(iii)
Explanation. Leishmania donovani causes kala-azar, Wuchereria bancrofti causes filariasis, Trypanosoma gambiense causes sleeping sickness and Entamoeba histolytica causes amoebiasis: A-ii, B-iv, C-iii, D-i.
Q12
Which of the following is an r-species ?
- A. rhinoceros
- B. human
- C. whale
- D. insectsCorrect
Explanation. r-species are small, short-lived organisms that produce many offspring with little parental care, such as insects. Rhinoceros, humans and whales are K-species.
Q13
ABO blood group in man is controlled by :
- A. Sex linked genes
- B. Multiple allelesCorrect
- C. Holandric genes
- D. Lethal genes
Explanation. The ABO blood group is governed by one gene (I) with three alleles, IA, IB and i, so it is an example of multiple alleles.
Q14
The organization which collects, compiles and publishes the red list of threatened species :
- A. IUCNCorrect
- B. WWF
- C. UNEP
- D. ZSI
Explanation. The International Union for Conservation of Nature (IUCN) maintains and publishes the Red List of threatened species.
Q15
In which mode of reproduction variations are seen ?
- A. SexualCorrect
- B. Asexual
- C. Parthenogenesis
- D. Both (a) and (b)
Explanation. In sexual reproduction, crossing over during meiosis and fusion of gametes from two parents create new gene combinations, so offspring show variations. Asexual reproduction and parthenogenesis give offspring like the single parent.
