The 15 one-mark questions from the March 2020 12th Standard Zoology public exam, in paper order, with the correct option marked and a short explanation.
Q1
Paedogenetic Parthenogenesis occurs in :
- A. Aphis
- B. Honey bees
- C. Solenobia
- D. Gall flyCorrect
Explanation. In paedogenetic parthenogenesis (paedogenesis) the larvae themselves produce young ones parthenogenetically; this is seen in the larvae of the gall fly (Miastor).
Q2
Which of the following menstrual irregularities is correctly matched ?
- A. Oligomenorrhoea - Excessive menstruation
- B. Menorrhagia - Painful menstruation
- C. Amenorrhoea - Absence of menstruationCorrect
- D. Dysmenorrhoea - Irregularity of menstruation
Explanation. Amenorrhoea is the absence of menstruation. Oligomenorrhoea is infrequent menstruation, menorrhagia is excessive bleeding and dysmenorrhoea is painful menstruation.
Q3
Which one of the following technique is used to monitor the foetal heart rate and other functions during late pregnancy and labour ?
- A. FoetoscopeCorrect
- B. EEG
- C. Amniocentesis
- D. CVS
Explanation. A foetoscope is used to monitor the foetal heart rate and other functions during late pregnancy and labour. Amniocentesis and CVS sample foetal cells for genetic tests, and EEG records brain activity.
Q4
If the Child’s blood group is ‘O’, the father’s blood group is ‘A’ and the mother’s blood group is ‘B’, the genotypes of the parents will be :
- A. IA IO and IB IOCorrect
- B. IA IA and IB IO
- C. IO IO and IB IB
- D. IA IB and IO IO
Explanation. An O group child has genotype IO IO, so each parent must carry one IO allele. A father with group A is therefore IA IO and a mother with group B is IB IO.
Q5
Assertion (A) : XX - XO type of sex determination is seen in bedbugs, cockroaches and grasshoppers.
Reason (R) : The sex of the offspring depends upon the sperm that fertilizes the egg.
- A. Both (A) and (R) are true and (R) is not the correct explanation for (A).
- B. Both (A) and (R) are false.
- C. (A) is true and (R) is false.
- D. Both (A) and (R) are true and (R) is the correct explanation for (A).Correct
Explanation. In the XX-XO type, females (XX) form only X eggs while males (XO) form two kinds of sperm, with X or without X. So the sex of the offspring is decided by the sperm that fertilizes the egg, which explains the assertion.
Q6
Which of the following chromosome has the highest gene density ?
- A. Chromosome ‘Y’
- B. Chromosome 1
- C. Chromosome 19Correct
- D. Chromosome 13
Explanation. The Human Genome Project showed that chromosome 19 has the highest gene density; chromosome 1 has the largest number of genes and the Y chromosome the fewest.
Q7
__________ and __________ proposed the classical model of Lac operon to explain gene expression and regulation in E. coli.
- A. Hershey, Chase
- B. Jacob, MonodCorrect
- C. Meselson, Stahl
- D. Watson, Crick
Explanation. Francois Jacob and Jacques Monod proposed the lac operon model of gene regulation in E. coli. Hershey and Chase proved DNA is the genetic material, Meselson and Stahl proved semiconservative replication, and Watson and Crick proposed the double helix.
Q8
A population will not exist in Hardy-Weinberg equilibrium if :
- A. The population is large.
- B. Individuals mate selectively.Correct
- C. There are no mutations.
- D. There is no migration.
Explanation. Hardy-Weinberg equilibrium requires a large population, random mating, no mutation, no migration and no natural selection. Selective (non-random) mating disturbs the equilibrium.
Q9
Find the true and false statements from the following :
(i) Plasmodium vivax is a digenic parasite.
(ii) The life cycle of Plasmodium involves 3 phases namely, schizogony, polygony and sporogony.
(iii) The large schizont shows yellowish - brown pigmented granules called Schuffner’s granules.
(iv) Plasmodium infection leads to Lysis of white blood cells results in cycles of fever and other symptoms.
- A. (i) - True, (ii) - True, (iii) - False, (iv) - True
- B. (i) - True, (ii) - True, (iii) - False, (iv) - False
- C. (i) - True, (ii) - False, (iii) - True, (iv) - FalseCorrect
- D. (i) - False, (ii) - True, (iii) - False, (iv) - True
Explanation. (i) is true: P. vivax needs two hosts, man and the female Anopheles mosquito. (ii) is false: the three phases are schizogony, gamogony and sporogony. (iii) is true. (iv) is false: it is the red blood cells that burst, releasing toxins that cause cycles of fever.
Q10
B Cells that produce and release large amounts of antibody is called :
- A. Killer Cells
- B. Memory Cells
- C. Basophils
- D. Plasma CellsCorrect
Explanation. On activation, B cells divide into plasma cells, which produce and secrete large amounts of antibodies, and memory cells, which remember the antigen.
Q11
Which one of the following bacterium is not involved in ethanol production ?
- A. Sarcina ventriculi
- B. Saccharomyces cerevisiae
- C. Ideonella sakaiensisCorrect
- D. Zymomonas mobilis
Explanation. Saccharomyces cerevisiae, Zymomonas mobilis and Sarcina ventriculi are used to produce ethanol. Ideonella sakaiensis is a bacterium that degrades PET plastic, not an ethanol producer.
Q12
The first clinical gene therapy was done for the treatment of :
- A. SCIDCorrect
- B. AIDS
- C. Cancer
- D. Cystic Fibrosis
Explanation. The first clinical gene therapy (1990) was given to a 4-year-old girl with adenosine deaminase (ADA) deficiency, which causes SCID (severe combined immunodeficiency).
Q13
Which of the following group of animals are the common fauna of the Thar deserts ?
- A. Gaur, Rhino, Antelope
- B. Jack rabbits, Kangaroo rats, Pocket mice
- C. The blackbuck, The Indian Spiny-tailed lizard, The white-footed foxCorrect
- D. Bobcat, Timber wolf, Black bear
Explanation. The blackbuck, the Indian spiny-tailed lizard and the white-footed desert fox are typical animals of the Thar desert. Jack rabbits, kangaroo rats and pocket mice live in North American deserts; gaur and rhino are forest and grassland animals.
Q14
In the E-waste generated by the mobile phones, which among the following metal is most abundant ?
- A. Gold
- B. CopperCorrect
- C. Silver
- D. Palladium
Explanation. Copper is the most abundant metal in mobile phone e-waste; gold, silver and palladium are present only in small amounts.
Q15
Which one of the following is not coming under in situ conservation ?
- A. Biosphere Reserve
- B. Sanctuaries
- C. National Parks
- D. Zoological ParkCorrect
Explanation. In situ conservation protects species in their natural habitat, as in biosphere reserves, sanctuaries and national parks. A zoological park keeps animals outside their habitat, so it is ex situ conservation.
