Evolution — BIOLOGY STD 12 Science — Question

Sakshi's father announced that the children are going to spend this weekend with their grandparents. During the journey, Sakshi saw some farmers who were spraying agrochemicals in their field. She requested her father to stop them. Her father praised her and contacted the farmers. He explained the side effects of such agrochemicals. He also suggested them to use biopesticides and biofertilisers instead of such chemicals. The farmers gave up spraying agrochemicals.

1. What did Sakshi's father explain to the farmers?
2. What are agrochemicals?
3. Why are biofertilisers or biopesticides preferred to chemical fertilisers or pesticides?
4. What values did Sakshi promote?

“Microbes play a dual role when used for sewage treatment as they not only help to retrieve usable water but also generate fuel”. Explain.

What are bacterial phages? Describe their structure in detail.

Fill in the blanks,

Species A	Species B	Type of Interaction	Example
+ + +	- + _____	_____ _____ Commensalism	_____ _____ _____

Answer the following questions:
Explain how recombinants and non-recombinants are differentiated on the basis of colour production in the presence of a chromogenic substrate. Name that procedure.

The zygote passes through several development stages till implantation. Describe each stage briefly with suitable diagrams.

There is only one possible sequence of amino acids when deduced from a given nucleotide. But multiple nucleotide sequences can be deduced from a single amino acid sequence. Explain this phenomenon.