Ecosystems — BIOLOGY STD 12 Science — Question

What is placenta? Draw well labelled diagram of human embryo showing placenta in uterus and also write its four functions.

Name three species of fungi that cause ringworm. Mention the symptoms of this disease?

Where does spermatogenesis occur in human testes? Describe the process of spermatogenesis upto the formation of spermatozoa.

What role does pituitary gonadotropins play during follicular and ovulatory phases of menstrual cycle? Explain the shifts in steroidal secretions.

Explain how xerarch succession progresses from serie to mesic condition and forms a stable climax community. You may use a flow chart.

What is incomplete dominance? Explain it taking the example of snapdragon plant by checker board. Also write the phenotypic and genotypic ratio.

A bright student of class XI, under peer pressure started taking drugs. He started neglecting studies, misbehaving with parents and friends in school. The principal of school counselled him, but it had no effect. His parents took him to a rehabilitation center. After a few months, he came back recovered.

1. What is drug abuse?
2. Name some commonly abused drugs and their source.
3. What should be the attitude of his parents after his return?
4. What values did the principal reflect through his initiative?

State the three principles of Mendel’s law of inheritance.

Bioreactors are the inclusion carriers in any biotechnology based production process. The ultimate success of any biotechnological technique depends on the efficiency of the bioreactor due to large scale production and economy.
In the context of the above passage, answer the following questions :
(i) For optimization of a bioreactor system, list possible operating instructions (rules). Make a list of any four.
(ii) "Optimal growth and metabolic activities of cells." Mention the stages of growth mentioned in.
(iii) Is the bioproduct formed in the bioreactor completely ready for immediate use as desired? Write the appropriate reasons also to support your answer.

More than 25% of human population is suffering from hunger and malnutrition. Scientists have developed techniques where microbes are grown on industrial scale as a source of good protein which can be grown from waste water, animal manure and even sewage.
Based on the above information answer the following questions.

1. In what ways would it be helpful to humans?
2. What can be the response to such new ventures?
3. What values have been manifested in the above case?