Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Explain the mechanism of reflex action.

Observe the set of 4 figures A, B, C and D and, answer the following questions,

1. Which one of the figures shows mutualism?
2. What kind of association is shown in D?
3. Name the organisms and the association in C.
4. What role is the insect performing in B?

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Arun visited his grandfather's farm and noticed that one of the workers was introducing earthworms in the soil. He quickly rushed to his grandfather and asked him the reason. His grandfather explained him the advantages of earthworm in soil improvement.

1. Why are earthworms also known as detritivores?
2. Explain fragmentation.
3. Name the steps in the process of decomposition.
4. What values are shown by Arun?

Justify the statements. If the answer is false, change the underlined word(s) to make the statement true.
(i) The DNA molecule is double stranded and the RNA molecule is single stranded.
Answer:

1. DNA as the genetic material has to be chemically and structurally stable.
2. It should be able to generate its replica.
3. Sugar-phosphate backbone and complementary base pairing between the two strands, give stability to DNA.
4. Both the strands of DNA act as template for synthesis of their complementary strands. This allows accurate replication of DNA.
5. Single stranded RNA can be folded to form complex structures and perform specific functions such as synthesis of proteins.

(ii) The process of translation occurs at the ribosome.

Do you think that friends can influence one to take alcohol/ drugs? If yes, how may one protect himself/ herself from such an influence?

Taking a small pond as an example of an ecosystem, list the four components of this ecosystem. How do these components function as a unit in a small pond?

What are symptoms of mineral deficiency in plants?

Homo erectus.

Evidences of Darwinism.

Describe the pathway followed by phosphorus in an ecosystem.