CBSE 12TH BIOLOGY - Online Test
Q1. DNA is extracted by
Answer : Option C
Explaination / Solution:
The piece of DNA obtained by gel electrophoresis contains agrose gel also. Ethanol precipitation is a commonly used technique for concentrating and de-salting nucleic acids (DNA or RNA) preparations in aqueous solution. The basic procedure is that salt and ethanol are added to the aqueous solution, which forces the precipitation of nucleic acids out of solution.
Q2. By studying analogous structures we look for
Answer : Option B
Explaination / Solution:
In evolutionary biology, the term analogous structures pertain to the various structures in different species having the same function but have evolved separately, thus do not share common ancestor.
Examples of analogous structures are as follows: wings of insects and birds used for flying
Q3. Water hyacinth is called as terror of Bengal due to
Answer : Option C
Explaination / Solution:
Water hyacinth is water weeds which grows very fast and covers the whole ponds in few days. Weeds absorb oxygen from the water and make it oxygen deficient that kills the fish in ponds along with other aquatic organisms.
Q4. An antibody is a
Answer : Option C
Explaination / Solution:
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as bacteria and viruses.
The antibody recognizes a unique molecule of the harmful agent, called an antigen, via the Fab's variable region.
Q5. Histamine is secreted by
Answer : Option D
Explaination / Solution:
Histamine is responsible for allergic reaction in the body in response to allergens. It is released from mast cell in response to infection or entry of foreign body.
Q6. Out of the following which is not an example of parasitism?
Answer : Option D
Explaination / Solution:
E.coli in human intestine obtain their food from undigested food remains and do not harm so, it is not an example of parasitism in which one organism is harmed but other is benefited.
Q7. The growing immunity, after getting the disease free body
Answer : Option A
Explaination / Solution:
When a host is exposed to antigens, antibodies are produced in the host body. This type of immunity is called active immunity. Hence, growing immunity after getting the disease free body is active acquired immunity.
Q8. In the DNA molecule:
Answer : Option C
Explaination / Solution:
In the DNA molecule, there are two strands which run antiparallel one in the 5′→3′direction and other in the 3′→5′.
Two strands are combined by Hydrogen bonds between nitrogenous bases of complementary strands.
Q9. Speed of decomposition will be
Answer : Option B
Explaination / Solution:
In detritus food chain, speed of decomposition will be fast if detritus is rich in simple sugar that can be easily decomposed into glucose by saprophytes that includes bacteria and fungi.
Q10. Heterosis means
Answer : Option D
Explaination / Solution:
Hybrid vigour is obtained from hybridization between two plants containing desired traits. Hybrid vigour is also called heterosis as it contains genes from different plants.
