CBSE 12TH BIOLOGY - Online Test
Q1. When we compare the relationship between species richness and area for wide variety of taxa, the graph appears to be a
Answer : Option B
Explaination / Solution:
- Alexander Von Humboldt has observed that within a region, species richness gets increased when explored area is increased, but only up to a limit.
- The relationship between species richness and area for a number of taxa like angiospermic plants, fresh water fishes and birds is found to be a rectangular hyperbola.
The equation is described by –
log S = log C + Z log A
S – Species Richness
Z – Slope of the line (regression coefficient)
A – Area
C – y-intercept
Q2. Which of the following is a primary sex organ of female?
Answer : Option A
Explaination / Solution:
Ovary is the primary sex organ of female reproductive system in human beings. Egg is released from one of the ovary each month. It also release hormone.
The secondary sex organs in a female are fallopian tubes, uterus, and vagina.
Q3. ABO blood groups in humans are controlled by the gene I. It has three alleles - IA, IB and i . Since there are 3 different alleles, six different genotypes are possible. How many phenotypes occur?
Answer : Option D
Explaination / Solution:
The three alleles - IA, IB and i will form four different kinds of blood group A, B, AB and O. as IA and IB are dominant and i is recessive in nature.
Q4. Biogas is a
Answer : Option A
Explaination / Solution:
Anaerobic decomposition of biomass like cow dung release biogas. This biogas contains mainly methane gas and can be used as fuel for cooking and lighting.
Q5. Correct sequence for the amount of dissolved oxygen in water body is:
Answer : Option A
Explaination / Solution:
Dissolve oxygen in water bodies is utilized by aquatic organisms for respiration. Oligotrophic have least dissolved oxygen followed by mesotrophic and eutropic have highest concentration of dissolved oxygen.
Q6. Within the embryo sac, three cells at chalazal end are called
Answer : Option D
Explaination / Solution:
The embryo sac is 8 nucleate, 7 celled structure. The three at micropylar ends are called egg Synergids and three at chalazal end are called antipodal cell. The remaining two at center forms the polar bodies.
Q7. The nuclease will act on
Answer : Option C
Explaination / Solution:
A nuclease (also archaically known as nucleodepolymerase or polynucleotidase) is an enzyme capable of cleaving the phosphodiester bonds between monomers of nucleic acids. Nucleases variously effect single and double stranded breaks in their target molecules.
There are two primary classifications based on the locus of activity. Exonucleases digest nucleic acids from the ends. Endonucleases act on regions in the middle of target molecules. They are further subcategorized as deoxyribonucleases and ribonucleases. The former acts on DNA, the latter on RNA.
Q8. The sequence of origin of life may be considered as
Answer : Option A
Explaination / Solution:
The sequence of origin of life may be as first formation of nucleic acid (DNA and RNA) followed by amino acids to form protein. Chlorophyll evolved in plants to become autotrophic from chemoheterotrophic.
Q9. In bacteria asexual reproduction takes palace by
Answer : Option A
Explaination / Solution:
In bacteria, asexual reproduction occurs by endospore formation in favorable condition. In unfavorable condition, bacteria produce sexually or change into cyst.
Q10. Gene therapy is used to treat
Answer : Option D
Explaination / Solution:
Gene therapy is used to treat hereditary genetic disorders which involve delivery of normal gene into the individual or embryo to take over the function of non-functional gene.
