CBSE 12TH BIOLOGY - Online Test
Q1. If DDT content in the water of a lake is found to be 0.004 ppm then pelicans of that area will have:
Answer : Option A
Explaination / Solution:
DDT is used as pesticide in crop fields and to kill mosquito in open drains. DDT is not a biodegradable and reaches to nearby water bodies. DDT enters the food chain through aquatic organisms and get magnified at each trophic levels. Pelicans beings at higher trophic levels may contain upto 2 ppm DDT.
Q2. How many meiotic divisions are required to form 64 pollen grains
Answer : Option A
Explaination / Solution:
Each microspore mother cell produces four pollen grains by reduction division. Hence to produce 64 pollen grains 16 meiotic or reduction division is required.
Q3. Eco RI acting on goi and vector will produce
Answer : Option C
Explaination / Solution:
Restriction enzymes, such as EcoRI, are used in a wide variety of molecular genetics techniques including cloning, DNA screening and deleting sections of DNA in vitro. Restriction enzymes, like EcoRI, that generate sticky ends of DNA are often used to cut DNA prior to ligation, as the sticky ends make the ligation reaction more efficient.
Q4. Which one of the following is incorrect about the characteristics of protobionts (coacervates and microspheres) as envisaged in the abiogenic origin of life?
Answer : Option B
Explaination / Solution:
Protobionts that include coacervates and microspheres are involved in origin of life from inorganic substance. Coacervate and microspheres are separate combinations of molecules from surroundings that leads to formation of first life on earth.
Q5. Stem cutting is used in the propagation of
Answer : Option C
Explaination / Solution:
Stem cutting is a mode of vegetative propagation in which stem is cut into pieces having at least one node. From the node new plantlet emerge out. Mango and cotton are grown by seeds and Banana by root cutting.
Q6. AIDS causing virus has
Answer : Option D
Explaination / Solution:
Acquired immunodeficiency syndrome is caused by human immuno virus. This virus has single stranded RNA as genetic material in place of DNA.
Q7. Amniocentesis for sex determination is legally banned to
Answer : Option C
Explaination / Solution:
Amniocentesis is a test to known chromosomal pattern of embryo that can reveals the sex of foetus. Large number of female foetus is aborted after knowing the sex of foetus. So it is illegal to check sex of foeticide.
Q8. Orchid shows commensalism as interaction with
Answer : Option D
Explaination / Solution:
Commensalism is interaction in which one species is benefited by other is neither benefited nor harmed. Orchids growing on mango tree do not harm the mango plants but get shelter.
Q9. The primary and secondary immune response are carried out with the help of two special types of lymphocytes present in our blood called
Answer : Option A
Explaination / Solution:
T cells (thymus cells) and B cells (bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response. T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for humoral immunity (relating to antibodies).
Q10. HIV is classified as a retrovirus because its genetic information is carried in
Answer : Option C
Explaination / Solution:
Retrovirus is a type of virus that uses RNA as its genetic material. After infecting a cell, a retrovirus uses an enzyme called reverse transcriptase to convert its RNA into DNA.
The retrovirus then integrates its viral DNA into the DNA of the host cell, which allows the retrovirus to replicate. HIV, the virus that causes AIDS, is a retrovirus.
