CBSE 12TH BIOLOGY - Online Test

Answer : Option D
Explaination / Solution:

Condom prevents the individual from both unwanted pregnancy as well as sexually transmitted diseases because it prevents the transfer of body fluid between two partners.

Answer : Option A
Explaination / Solution:

The synergids have special cellular thickening at micropylar tips called filiform apparatus which help in guiding pollen tube into egg synergids for fertilisation to form embryo.

Answer : Option C
Explaination / Solution:

Intraspecific competition could be most intense and strongest as it occurs between organisms having same types of requirement of food, water etc. They may have competition for food, shelter, water, space or mat also.

Answer : Option D
Explaination / Solution:

Lysergic acid diethylamide is one of the most potent mood changing chemicals manufactured from lysergic acid, which is found in ergot fungus that grow on rye and other grains.

Answer : Option C
Explaination / Solution:

The genetic code is the set of "rules" that a cell uses to interpret the nucleotide sequence within a molecule of mRNA. This sequence is broken into a series of three-nucleotide units known as codons.

The three-letter nature of codons means that the four nucleotides found in mRNA — A, U, G, and C — can produce a total of 64 different combinations. Of these 64 codons, 61 represent amino acids, and the remaining three represent stop signals, which trigger the end of protein synthesis.

Because there are only 20 different amino acids but 64 possible codons, most amino acids are indicated by more than one codon. ( however, that each codon represents only one amino acid or stop codon.).

This phenomenon is known as redundancy or degeneracy, and it is important to the genetic code because it minimizes the harmful effects that incorrectly placed nucleotides can have on protein synthesis.

Answer : Option A
Explaination / Solution:

MOET stands for Multiple Ovulation Embryo Transfer technology. In this technology hormone is administrated for multiple ovulation followed by artificial insemination and transfer the embryo into surrogate cow.

Answer : Option D
Explaination / Solution:

The Amazon in South America is the largest, most diverse tropical rainforest on Earth, covering an area of five and a half million square kilometres. The Amazon rainforest functions as a giant air machine that absorbs a large amount of carbon dioxide, and produces oxygen. That is why it is often called the "Lungs of the Earth.

Answer : Option B
Explaination / Solution:

Spermatogenesis occurs in the seminiferous tubules of the testes. The seminiferous tubules are lined by germinal epithelium which are made up of germ cells and sertoli cells.

Answer : Option A
Explaination / Solution:

Genes are segment of DNA present on chromosome. Large numbers of genes are located on single chromosome. A gene or genes determines the traits of the individual.

Answer : Option C
Explaination / Solution:

Symbiotic association of fungi with angiosperm plant root is called mycorrhiza. Most of the plants have this kind of relation. The fungus obtains some sugar from the plant and plant get minerals and water absorbed by fungi.