CBSE 12TH BIOLOGY - Online Test
Q1. The common nitrogen-fixer in paddy fields is
Answer : Option A
Explaination / Solution:
Nitrogen is obtained by plants either in nitrate or nitrite forms. Some microbes convert atmospheric nitrogen into nitrate and nitrite. The common nitrogen-fixing microbe in paddy field is Azospirillum.
Q2. Soil pollution :
i. can be of two types- positive and negative
ii. soil erosion is an example of positive soil pollution
i. can be of two types- positive and negative
ii. soil erosion is an example of positive soil pollution
Answer : Option D
Explaination / Solution:
Addition of harmful substances in soil is called soil pollution. Soil pollution is of two types positive and negative. Addition of organic wastes increase the productivity so positive. Soil erosion is the removal of top fertile layer of soil that reduce its fertility so it is a negative soil pollution.
Q3. Primers are
Answer : Option A
Explaination / Solution:
Primers are chemically synthesized oligonucleotides that are complementary to the regions of DNA and the enzyme DNA polymerase.
Q4. Lamarck theory of organic evolution is usually known as
Answer : Option B
Explaination / Solution:
Lamarck theory of organic evolution is also known as inheritance of acquired traits. He believed that the character an individual gain in his life time is also passed to next generation.
Q5. Which plant can propagated Vegetatively by leaf
Answer : Option A
Explaination / Solution:
Bryophyllum plants grow in marshy areas where seeds are not able to germinate. The leaf margin of Bryophyllum contains numerous plantlets before falling on muddy land.
Q6. Which of the following ecosystem services cost maximum
Answer : Option A
Explaination / Solution:
Soil formation accounts for about 50% of total cost of ecosystem services. Nutrient cycling and recreation accounts for about 10% of all ecosystem services.
Q7. Transgenic mice are being developed for use in testing the safety of
Answer : Option C
Explaination / Solution:
Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine. If successful and found to be reliable, they could replace the use of monkeys to test the safety of batches of the vaccine.
Q8. Which one out of following is not a consequence of overpopulation
Answer : Option C
Explaination / Solution:
The consequence of overpopulation includes unemployment, price rise, and energy crisis. Hygienic condition is not directly affected by overpopulation.
Q9. Embryology is
Answer : Option B
Explaination / Solution:
Embryology is the branch of biological science in which we study about spore, fertilisation as well as formation of embryo. It is not just the formation of embryo from zygote.
Q10. The term Darwinian fitness among populations living together signifies
Answer : Option A
Explaination / Solution:
The term Darwinian fitness among populations living together signifies the reproductive fitness of organisms population. Those species that can reproduce in between are called reproductive fitness.
