CBSE 12TH BIOLOGY - Online Test
Q1. First organic acid produced by microbial fermentation is
Answer : Option D
Explaination / Solution:
Lactic acid occurs in two isomeric forms i.e. L (+) and D (-) isomers, and as a racemic mixture (DL-lactic acid). The isolation of lactic acid from milk was done in 1798. It was the first organic acid produced by microorganisms in 1880. Today, lactic acid is competitively produced both by microbiological and chemical methods.
Q2.
Read the following statements:
i. carbondioxide is a qualitative pollutant.
ii. carbondioxide is already present in environment and is termed as pollutant when it’s concentration increases in the environment:
Answer : Option B
Explaination / Solution:
Carbon dioxide is a quantitative pollutant. This gas is already present in environment in small quantity. When its concentration increases in the environmentit is termed as pollutant. It may cause greenhouse effect also.
Q3. When two parents participate in reproductive process and also involve fusion of their gametes, it is called
Answer : Option C
Explaination / Solution:
In sexual reproduction male and female gametes are produced by male and female organism. The fusion of gametes results into zygote formation that finally develops as new offspring.
Q4. The technique used to produce large number of genetically identical offspring is called as
Answer : Option A
Explaination / Solution:
Cloning is the production of an exact copy of an animal by means of asexual reproduction. Any two animals which contain exactly the same genes are called genetically identical.
An animal which is genetically identical to its parents is called clone.
The cloning of a large animal was successfully done for the first time by Ian Wilmut and his colleagues at the Roslin Institute in Edinburg.
They cloned a sheep named Dolly from its parent sheep called Finn Dorest sheep.
Q5. Which of the following amino acids was not found to be synthesized in Miller’s Experiment?
Answer : Option C
Explaination / Solution:
The famous experiment of Urey and Miller regarding origin of life from inorganic substance produced amino acids, sugar and nitrogenous base etc. glutamic acid was not found in this experiment.
Q6. Successful graft reaction can be done by
Answer : Option D
Explaination / Solution:
Xenotransplantation is the transplantation of living cells, tissues or organs from one species to another. Such cells, tissues or organs are called xenografts or xenotransplants.
Successful graft reaction can be done by using Xenotransplantation to get two kinds of products from single plant.
Q7. A dark stained body present in the somatic cells of human female but absent from those of male is
Answer : Option D
Explaination / Solution:
Barr body is present in somatic cells of human female but it is absent in male. The function of this body is still not known completely.
Q8. For which of the following would you expect distribution range to be badly affected if average Global temperature keeps increasing:
Answer : Option A
Explaination / Solution:
A majority of organisms are restricted to narrow range of temperature. Such organisms are called stenothermal species. The distribution range of these species will be adversely affected if average global temperature keeps increasing.
Q9. Aedesaegypti is a vector for
Answer : Option D
Explaination / Solution:
Dengue fever and yellow fever, both are transmitted to human beings through a mosquito called Aedesaegypti. This mosquito breeds in clean stagnant water and carry the disease causing virus form infected person to healthy person.
Q10. In a DNA strand the nucleotides are held together by:
Answer : Option B
Explaination / Solution:
When nucleotides are incorporated into DNA, adjacent nucleotides are linked by a phosphodiester bond: a covalent bond is formed between the 5' phosphate group of one nucleotide and the 3'-OH group of another.
In this manner, each strand of DNA has a “backbone” of phosphate-sugar-phosphate-sugar-phosphate
