Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

What is artificial selection? Explain with examples?

Many microbial pathogens enter the gut of humans along with food. What are the preventive barriers to protect the body from such pathogens? What type of immunity do you observe in this case?

Describe the major features of embryonic development at various months of pregnancy.

Highlight the differences and a similarity between the following population interactions: competition, predation and commensalism.

Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?

Name three incurable sexually transmitted diseases and their causative organisms.

If implementation of better techniques and new strategies are required to provide more efficient care and assistance to people, then why is there a statutory ban on amniocentesis? Write the use of this technique and give reason to justify.

Discuss briefly about seed viability.

Explain the process of pollination in Vallisneria. How is it different in water-lily, which is also an aquatic plant?

What essential features must be present in a cloning vehicle/ cloning vector?