CBSE biology important very short questions 2023

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CBSE Class 12 Biology board exam 2023 will be held on Thursday, March 16, 2023 from 10.30 AM to 01.30 PM. All students are practicing hard to score well in the exam.

With focus on the right resources and smart work, CBSE Class 12 Biology students will be able to achieve their dream scores. In this article, we are providing students with Important Very Short Answer Type Questions for CBSE Class 12 Biology board exam 2022-23.

Important Very Short Answer Type Questions:

  1. Name an organism where cell division in itself is a mode of reproduction. (AI 2013)

Ans. In Amoeba, asexual reproduction takes place by division of parent body.

  1. Name the part of the flower which the tassels of the corn-cob represent. (AI 2014)

Ans. Tassels of corn-cob represent staminate inflorescence (cluster of male flowers), so they represent androecium (male reproductive part) of the flower.

  1. Name the cells that nourish the germ cells in the testes. Where are these cells located in the testes? (AI 2013C)

Ans. The cells that nourish the germ cells in the testes are called Sertoli cells. Sertoli cells are located in the germinal epithelium of the seminiferous tubules.

  1. Write the function of the seminal vesicle. (1/3, Delhi 2012)

Ans. Seminal vesicle produces an alkaline secretion that helps to neutralise the acidic environment of the male urethra as well as that of female reproductive tract.

  1. Give reasons for the following : The human testes are located outside the abdominal cavity. (1/2, AI 2012)

Ans. The human testes are located outside the abdominal cavity within a pouch called scrotum. The scrotum helps in maintaining the low temperature of the testes (2- 2.5°C) lower than the normal internal body temperature, necessary for spermatogenesis.

  1. Name an IUD that you would recommend to promote the cervix hostility to the sperms. (Delhi 2014C)

Ans. Progestasert is a hormone releasing IUD (intrauterine contraceptive device) which makes the cervix hostile to the sperms.

  1. State one reason why breast-feeding the baby acts as a natural contraceptive for the mother. (AI 2014C)

Ans. Ovulation, and therefore the menstrual cycle, does not occur during intense lactation period (following parturition). Therefore, breast feeding the baby act as a natural contraceptive for the mother but that too upto a maximum period of six months.

  1. Our government has intentionally imposed strict conditions for MTP in our country. Justify giving a reason. (Delhi 2017

Ans. Government of India has imposed strict conditions for MTP because it is being misused for sex determination and illegal abortions of female fetuses. Due to female feticides, male and female sex ratio may get disturbed, raising many ethical, religious and social issues.

  1. A geneticist interested in studying variations and patterns of inheritance in living beings prefers to choose organisms for experiments with shorter life cycle. Provide a reason. (Delhi 2015)

Ans. Living beings with shorter life cycles are preferred by geneticists for studying variations and patterns of inheritance because such organisms complete their life cycle in short duration and produce large number of progenies in less time span, e.g., pea plant used in Mendel’s experiments.

  1. Mention any two contrasting traits with respect to seeds in pea plant that were studied by Mendel. (AI 2014)

Ans. Seed traits studied by Mendel in pea plant were:

(i) Seed shape – Smooth/Round (R) Wrinkled (r)

(ii) Seed (cotyledon) – Yellow (Y) colour Green (y)

  1. A garden pea plant (A) produced inflated yellow pod and another plant (B) of the same species produced constricted green pods. Identify the dominant traits. (Delhi 2012)

Ans. Inflated and green colour pod are dominant traits over constricted and yellow colour pod which are recessive traits.

  1. Name the transcriptionally active region of chromatin in a nucleus. (Delhi 2015)

Ans. Euchromatin is the transcriptionally active region of chromatin in a nucleus.

  1. Name the negatively charged and positively charged components of a nucleosome. (Delhi 2015C)

Ans. The negatively charged and positively charged components of a nucleosome are DNA and histones respectively.

  1. Write the hypothetical proposals put forth by Oparin and Haldane. (Foreign 2015)

Ans. Hypothetical proposals given by Oparin and Haldane :

(i) Life originated spontaneously from preexisting non-living organic molecules.

(ii) Formation of life was preceded by chemical evolution

  1. State two postulates of Oparin and Haldane with reference to origin of life. (AI 2017)

Ans. The two postulates of Oparin and Haldane with reference to origin of life are:

(i) The first form of life could have come from pre-existing, non-living organic molecules (e.g., RNA, protein, etc.) and that formation of life was preceded by chemical evolution.

(ii) The primitive atmosphere was of reducing type, i.e., containing gases like CH4, NH3, etc. The earth had high temperature and volcanic storms. There was no free oxygen.

  1. Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes. (2018)

Ans. Chikungunya and dengue can be controlled by the eradication of Aedes mosquitoes.

  1. Why do we add an inoculum of curd to milk for curdling it? (AI 2015C)

Ans. The starter or inoculum used in preparation of milk products actually contains millions of lactic acid bacteria. Curd is prepared by inoculating cream and skimmed milk with Lactobacillus acidophilus at a temperature of about 40° C or less. Lactobacillus converts lactose sugar of milk into lactic acid which causes coagulation and partial digestion of milk protein casein and milk gets changed into curd.

  1. How is lactic acid bacteria beneficial to us other than helping in curdling the milk? (AI 2015C)

Ans. Lactic acid bacteria is beneficial to us in the following ways other than helping in curdling of milk:

(i) Increases nutritional quality of curd by increasing vitamin B12 content.

(ii) Checks the growth of disease-causing microbes in the gut.

  1. What is the cell that receives a recombinant gene called? (AI 2019)

Ans. The cell that receives recombinant gene is known as genetically modified cell or recombinant cell.

  1. Write the two components of the first artificial recombinant DNA molecule constructed by Cohen and Boyer. (Foreign 2014)

Ans. Two components of first artificial recombinant DNA molecule constructed are : An antibiotic resistance gene and plasmid of Salmonella typhimurium.

  1. What are Cry genes? In which organism are they present? (AI 2017)

Ans. Cry genes are specific genes that encodes cry proteins. They are produced in Bacillus thuringiensis. Man had developed several transgenic crops by introducing these genes from bacteria to crop plants such as Bt cotton, Bt corn, etc

  1. State the role of transposons in silencing of mRNA in eukaryotic cells. (AI 2013)

Ans. Transposons also called as jumping genes, are the source of complementary dsRNA molecule that binds to and prevents translation of mRNA (silencing).

  1. Give example of an organism that enters ‘diapause’ and why? (Delhi 2014)

Ans. Bombyx mori (silk moth) is an insect that enters diapause due to some adverse environmental conditions such as drought, extreme temperature, reduced food availability; which, in turn, delays the overall development. The physiological and metabolic activities diminish at this particular time.

  1. Why are green algae not likely to be found in the deepest strata of the ocean? (AI 2013)

Ans. Green algae are photosynthetic in nature. In the deepest strata of the ocean i.e., benthic zone, light does not penetrate therefore, this zone is in perpetual darkness and photosynthetic organisms such as green algae cannot survive in this region.

  1. Mention how do bears escape from stressful time in winter. (Delhi 2013C)

Ans. Bears undergo hibernation to escape from stressful time in winter. In hibernation, they seek a warm shelter and remain dormant, their respiration rate turns low and they consume stored food.

  1. Write the equation that helps in deriving the net primary productivity of an ecosystem. (Delhi 2013)

Ans. Net primary productivity is the weight of the organic matter stored by the producers which is available to heterotrophs for consumption. It is equal to the rate of organic matter produced during photosynthesis (GPP) minus respiratory losses (R). NPP = GPP – R.

  1. Write the level of biodiversity represented by a mangrove. Give another example falling in the same level. (AI 2014C)

Ans. Ecological diversity is found in mangrove. Rainforests also show same level of biodiversity.

  1. An electrostatic precipitator in a thermal power plant is not able to generate high voltage of several thousands. Write the ecological implication because of it.(AI 2017)

Ans. Electrostatic precipitators (ESPs) are the devices where particles present in dirty air are charged electrically to form a corona of negative charges around them. These charged dust particles when passed over collection plates of ESPs (electrically connected earth) loose their charge and settle down. If ESP in a thermal power plant is unable to generate high voltage of several thousands, that means it is not functioning properly. Due to this, the dust particles will not be able to get charged and settle down. This will result in pollution of air.

  1. Mention two advantages for preferring CNG over diesel as an automobile fuel. (AI 2016)

Ans. CNG is preferred over diesel because it burns more efficiently without producing much pollution and it cannot be adulterated like diesel.

  1. List two advantages of the use of unleaded petrol in automobiles as fuel. (AI 2015)

Ans. Two advantages of using unleaded petrol in automobiles as fuel are:

(i) Unleaded petrol results in decline in the emission of harmful gases such as SO2, CO and NO2, thereby improving air quality.

(ii) It is desirable to use unleaded petrol in the automobiles fitted with catalytic converter because lead in the petrol inactivates the catalyst metals like platinum-palladium and rhodium, etc. present in the converter.

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