CBSE 12TH BIOLOGY - Online Test
Q1. The test that are used for diagnosis of AIDS are
Answer : Option C
Explaination / Solution:
The incubation period of AIDS is up to 7 years. It can be detected earlier using the diagnostic tools based on biotechnology. Western blotting test and ELISA are two common tests.
Q2. An age pyramid showing declining population is
Answer : Option A
Explaination / Solution:
Age pyramids having declining population is referred as contracting pyramid or orion pyramids or Urn pyramids. This kind of pyramids is formed by population having more old aged population than young age population.
Q3. Which of the following provides physiological barrier as innate immunity?
Answer : Option B
Explaination / Solution:
Physiological barrier is a kind of innate immunity which prevents microbial growth in the body that causes infection. Acid in stomach kill the microbes that enters the alimentary canal along with food.
Q4. Copying of DNA to make more DNA copies is called DNA replication. Replication occurs by method of
Answer : Option A
Explaination / Solution:
In semiconservative replication, when the double stranded DNA helix is replicated, each of the two new double-stranded DNA helices consisted of one strand from the original helix and one newly synthesized. It has been called "the most beautiful experiment in biology.
Semi-conservative replication of DNA was proved by the Meselson and Stahl in 1958.
Q5. Correct decreasing order for rate of primary productivity on land will be
Answer : Option B
Explaination / Solution:
Primary productivity is maximum in tropical rain forests due to availability of sufficient food and water followed by temperate forests. Savannah grasslands have comparatively less productivity and arid regions have limited biotic component and water.
Q6. In which crops is the method of mass selection applied
Answer : Option B
Explaination / Solution:
In cross pollinated plants, the newly developed plants have variation and some plant have new traits. Mass selection method is used to select better variety of plants from large number of variant.
Q7. Which of the following is a gene sanctuary
Answer : Option A
Explaination / Solution:
A gene sanctuary is an area where plants are conserved. It includes both biosphere reserves as well as national parks.
India has set up its first gene sanctuary in the Tura range of Meghalaya for wild relatives of citrus. Efforts are also being made to set up gene sanctuaries for banana, sugarcane, rice and mango.
Q8. In sectional view of female reproductive system, Label (III) and (IV).
Answer : Option C
Explaination / Solution:
Infundibulum and fimbriae are the parts of fallopian tube (oviduct) through which ovum released from ovary passes towards uterus. Fertilisation of ovum occurs in fallopian tube.
Q9. Heterozygous tall plants were crossed with dwarf plants what will be the ratio of dwarf plants in the following progeny?
Answer : Option B
Explaination / Solution:
Heterozygous tall plant (Tt) is crossed with homozygous dwarf (tt) the percentage of dwarf plants is 50 percent.
Q10. High value of BOD shows
Answer : Option A
Explaination / Solution:
Biological oxygen demand is the amount of oxygen required to completely decompose the organic waste present in one liter of water by bacteria. High value of BOD shows that water is highly polluted.
