Ecosystems — BIOLOGY STD 12 Science — Question

What is semen?

Alien species are a threat to native species. Justify taking examples of an animal and a plant alien species.

What are chorionic villi?

Now, sequencing of total genomes getting is getting less expensive day by the day. Soon it may be affordable for a common man to get his genome sequenced. What in your opinion could be the advantage and disadvantage of this development?

What is LAB? What is its role in human stomach?

A person has been diagnosed to be HIV positive.

1. Name the test which the person underwent.
2. Write the full name of the pathogen involved and describe its structure.
3. Which particular cells of this person are likely to get destroyed?

What do you mean by reproductive health? Mention the different ways in which people are made aware of the significance of reproductively healthy society.

Write any four facts proved by the study of fossils regarding the development of life?

Write the mode of pollination in Vallisneria and water lily. Explain the mechanism of pollination in Vallisneria.

Given below are the events that are observed in an artificial hybridisation programme. Selection of parents → Emasculation → Bagging → Collection of pollen from other male plant → Dusting of pollen on stigma — Rebagging.
While, planning for crop improvement involving dioecious plants, which of the above mentioned steps would not be relevant?