CBSE 12TH BIOLOGY - Online Test
Q1. The number of births in polygamous population is often directly related to
Answer : Option B
Explaination / Solution:
Polygamous population is often directly related to number of females in the population. Polygamy means having more than one female partner with single male that can reproduce.2
Q2. Which of the following factor do not motivate youngsters towards drug and alcohol use?
Answer : Option D
Explaination / Solution:
Curiosity, need for adventure and excitement and experimentation constitute common causes, which motivate youngsters towards drug and alcohol use.
Q3. Balbiani rings are the sites of
Answer : Option C
Explaination / Solution:
A Balbiani ring is a large chromosome puff. Balbiani rings are diffused uncoiled regions of the polytene chromosome that are sites of RNA transcription and protein synthesis.
They are formed in eukaryotic cells only.
Q4. Which one is not a common fresh water fish
Answer : Option C
Explaination / Solution:
Hilsa is not a common fresh water fish. It is a marine fish. Common fresh water fish are Catla, Rohu and Common carp.
Q5. Nowadays,the greatest cause for extinction or biodiversity loss is
Answer : Option C
Explaination / Solution:
The greatest cause for extinction or biodiversity loss is the habit alteration. Deforestation causes loss of habits of a number of wild animals. Pollution of water also alter the habitat of aquatic organisms.
Q6. The correct order of uterus layers form outside to inside is
Answer : Option A
Explaination / Solution:
The wall of uterus has three layers of tissues. The outer most thin layer is called perimetrium followed by thick layer of smooth muscles, myometrium and innermost glandular tissue is endometrium.
Q7. In human males, some recessive genes express their effect because
Answer : Option D
Explaination / Solution:
Recessive genes are expressed only in case of homozygous condition but sex chromosomes of males do not have opposite alleles on Y-chromosome. So, the recessive gene located on X-chromosome get expressed in males.
Q8. The biological control of agricultural pests, unlike chemical control is
Answer : Option C
Explaination / Solution:
The biological control of agricultural pest, unlike chemical control is called self-perpetuating as biological control has power to renew or perpetuate oneself of itself for indefinite length of time.
Q9. In which year did the scientists report largest ozone hole in the atmosphere?
Answer : Option A
Explaination / Solution:
From September 21 to 30, 2006 the average area of the ozone hole was the largest ever observed, at 10.6 million square miles. It is called as Antarctic ozone hole.
Q10. The DNA fragments in an agarose gel at the same position signify that the two fragments have
Answer : Option C
Explaination / Solution:
Gel electrophoresis is a technique used to separate DNA fragments (or other macromolecules, such as RNA and proteins) based on their size and charge. Electrophoresis involves running a current through a gel containing the molecules of interest. Based on their size and charge, the molecules will travel through the gel in different directions or at different speeds, allowing them to be separated from one another.
The DNA fragments in an agarose gel at the same position signify that the two fragments have same molecular weight and travel same distance.
