CBSE 12TH BIOLOGY - Online Test
Q1. In grafting, scion forms
Answer : Option C
Explaination / Solution:
In grafting, scion forms the upper shoot system and stock forms the lower root system. Grafting is an artificial mode of vegetative propagation in which two plants are cut and same height and joined together.
Q2. Which of the following birth control measure can be considered as the safest?
Answer : Option D
Explaination / Solution:
A number of birth control measures are used to prevent unwanted pregnancy. Sterilization technique is considered as the safest way. Condom prevents unwanted pregnancy as well as sexually transmitted disease.
Q3. RNA molecules that act as enzymes are called
Answer : Option C
Explaination / Solution:
Until about 20 years ago, all known enzymes were proteins. But then it was discovered that some RNA molecules can act as enzymes; that is, catalyze covalent changes in the structure of substrates (most of which are also RNA molecules). Catalytic RNA molecules are called ribozymes.
Only a few RNA molecules act as enzymes.
Q4. Which one of the following pair is incorrectly matched in respect to the "crop varieties for disease resistance"?
Answer : Option D
Explaination / Solution:
Wheat plants are generally not infected by leaf and stripe rust. Common disease of wheat includes rust and smut disease. Wheat plants are not develop resistance for leaf and stripe rust.
Q5.
Read the following statements:
i) Insects are essentially absent from the sea.
ii) The species diversity on land is generally considerably lower than oceans.
Answer : Option C
Explaination / Solution:
Insects are essentially absent from the sea because insects respire using trachea from air.The species diversity on land is generally considerably higher than ocean therefore, statement ii is incorrect.
Q6. The number of polar bodies formed during oogenesis in human being is
Answer : Option A
Explaination / Solution:
During oogenesis reduction division occurs in primary oocytes to produce one polar body and secondary oocytes. Polar bodies further divide to form two polar bodies. Secondary oocytes further divide to produce one polar bodies and a secondary follicle to produce ovum.
Q7.
What does the chart given below represent?
Answer : Option D
Explaination / Solution:
The chart given below represent XX-XO type of sex determination in which XX forms the female and XO develops as male. It is common in birds.
Q8. Which kingdoms among the living organism contain only micro-organisms?
Answer : Option C
Explaination / Solution:
Monera and Protista contain only micro-organisms. Monera contains unicellular prokaryotic organisms like bacteria. Protista contains unicellular eukaryotic organisms.
Q9. Ozone depletion shall cause higher incidence of
Answer : Option D
Explaination / Solution:
The depletion of ozone layer allows entering of UV rays from sun into the earth’s atmosphere which is associated with a number of health related and environmental issues.
Skin Cancer: exposure to UV rays from sun can lead to increased risk for developing of several types of skin cancers. Malignant melanoma, basal and squamous cell carcinoma are the most common cancers caused by exposure to UV rays.
Eye Damage: UV rays are harmful for our eyes too. Direct exposure to UV rays can lead to Cataract problems, and also Photokeratitis or snow blindness.
Damage to Immune system: our immune system is also highly vulnerable to UV rays. Increased exposure to UV rays can lead to weakening of the response of immune system and even impairment of the immune system in extreme cases.
Q10. The smallest bands in the agarose gel will be towards
Answer : Option C
Explaination / Solution:
The smallest segment of DNA in the agrose gel will be towards anode or positively charged ends. The DNA fragments are negatively charged and moves towards negatively charged anode.
