CBSE 12TH BIOLOGY - Online Test
Q1. Female hetrogamety is present in
Answer : Option A
Explaination / Solution:
Female heterogamety is the formation of different types of gametes in female. Although male produce same types of gametes. In birds the female have ZW sex chromosome and male have ZZ sex chromosome.
Q2. Bacterial leaf blight of rice is caused by a species of
Answer : Option A
Explaination / Solution:
Bacterial leaf blight of rice is caused by bacterium Xanthomonas. The bacteria reduce the photosynthetic area of leaf and finally yield of rice is affected considerably.
Q3. Earth is protected from ultra-violet radiations by means of
Answer : Option C
Explaination / Solution:
Ozone layer (stratospheric ozone) is a high concentration of ozone molecules about 30 to 50 km altitude (stratosphere). The main function of the ozone layer is to absorb the Sun's ultraviolet radiation, hence protecting the Earth from its harmful effects.
Q4. Transfer of DNA into bacteria by phage is called as
Answer : Option C
Explaination / Solution:
Transfer of DNA into bacterial cell by phage or virus is called transformation. Phage kills the bacterium so called bacteriophage.
Q5. Select the correct statement from the following:
Answer : Option B
Explaination / Solution:
In organic evolution, fitness is the end result of the ability to adapt and gets selected by nature. Darwinian variations are small and directional. Mutation is sudden change in gene and all mammals have vertebrae.
Q6. Which of the following may cause algal blooms in the aquatic system:
Answer : Option C
Explaination / Solution:
Algal bloom is rapid increase in population of algae is a water system. This is caused due to excess of nutrients like phosphorus and nitrogen in the water bodies.
Q7. Expand GEAC
Answer : Option A
Explaination / Solution:
The Genetic Engineering Approval Committee (GEAC) is the apex body constituted in the Ministry of Environment and Forests under 'Rules for Manufacture, Use, Import, Export and Storage of Hazardous Microorganisms/Genetically Engineered Organisms or Cells 1989', under the Environment Protection Act, 1986.
Q8. The function of copper-T is to prevent
Answer : Option C
Explaination / Solution:
Copper-T is an intra-uterine device that is used by female to avoid unwanted pregnancy. This device prevents implantation and decrease the motility of sperm by releasing copper ions.
Q9. Coconut fruit is dispersed by
Answer : Option B
Explaination / Solution:
Coconut is generally grown near water bodies. The seeds of coconut fall in water and float to different places that dispersed the seed.
Q10. At high altitudes our body compensates for deficiency of oxygen by
Answer : Option A
Explaination / Solution:
At higher altitudes concentration of oxygen decreases in air due to decreae in air pressure. Our body compensate the deficiency of oxygen at higher altitude by reducing affinity of hemoglobin (Hb) for oxygen binding.
