CBSE 12TH BIOLOGY - Online Test
Q1. Seed dispersal helps the species to
Answer : Option A
Explaination / Solution:
Seeds have adaptive strategies for dispersal to new habitat and help the species to colonies in new areas. Dispersal may occurs physically or with the help of birds and other animals.
Q2. Unit of evolution and ecology is
Answer : Option B
Explaination / Solution:
The unit of evolution and ecology is population. Evolution occurs due to change in genome of individual that affects the whole population. Ecology is the study of population along with their variation in ecosystem.
Q3. Statement I: Asexual reproduction involves fusion of gametes.
Statement II: Asexually produced offspring are genetically identical.
Statement III: Asexual reproduction occurs in unfavorable condition only.
Statement II: Asexually produced offspring are genetically identical.
Statement III: Asexual reproduction occurs in unfavorable condition only.
Answer : Option B
Explaination / Solution:
In asexual reproduction, fusion of gametes do not takes place and asexual reproduction occurs in favorable conditions. As fusion of gametes do not takes place, all the individuals are genetically identical to each other.
Q4. Assertion: Mast cells in the human body release excessive amounts of inflammatory chemicals, which cause allergic reactions.
Reason: Allergens in the environment on reaching human body stimulate mast cells in certain individuals.
Reason: Allergens in the environment on reaching human body stimulate mast cells in certain individuals.
Answer : Option C
Explaination / Solution:
The IgE-primed mast cell releases granules and powerful chemical mediators, such as histamine, cytokines, granulocyte macrophage colony-stimulating factor (GM-CSF), leukotrienes, heparin, and many proteases into the environment. These chemical mediators cause the characteristic symptoms of allergy.
Q5. Which one represents the correct manner of DNA replication?
Answer : Option A
Explaination / Solution:
During replication of DNA, in one strand (3’ to 5’) replication takes place continuously and in other strand it is in small segment and joined together by DNA ligase enzyme.
Q6. Lysine rich Maize variety is
Answer : Option C
Explaination / Solution:
Lysine is a type of amino acids present in the proteins. Maize variety Shakti is rich in lysine amino acids.
Q7. Cleanliness observed by human beings will adversely affect the habitats of:
Answer : Option D
Explaination / Solution:
Scavenger feeds on dead animal and plant material present in the habitat. Cleanliness observed by human beings will adversely affect the habitat of the scavengers.
Q8. Division of human egg is
Answer : Option C
Explaination / Solution:
Meroblastic is the type of incomplete cleavage that occurs in very yolky eggs, in which the egg cytoplasm but not the yolk divides.
Q9. Henking in 1891 observed a specific nuclear structure in 50% of sperms. He named this structure as
Answer : Option D
Explaination / Solution:
The specific nuclear structure in few insects and 50 percent of the sperm observed by Henking was named as X body. Although its role in sex determination was not known to his time.
Q10. Which of the following microbes cannot be grown into nutritive media?
Answer : Option B
Explaination / Solution:
Virus cannot be grown into nutritive medium because it lacks all cellular apparatus required for reproduction. It reproduces using cellular apparatus of host cell.
