Organisms and Populations — BIOLOGY STD 12 Science — Question

Under natural immunity, how are we automatically protected from environmental germs through protective processes? ###How do innate immunity prevent the entry of external pathogenic factors? Explain.

Explain in detail about modern concept of evolution.

Name the two end products of double fertilization in angiosperms. How are they formed? Write their fate during the development of seed.

Throughout sexual reproduction the chromosome number is maintained same. How is this done?

A woman has certain queries as listed below, before starting with contraceptive pills. Answer them.
What schedule should be followed for taking these pills?

1. Name the stage of Plasmodium that gains entry into the human body.
2. Trace the stages of Plasmodium in the body of female Anopheles after its entry.
3. Explain the cause of periodic recurrence of chill and high fever during malarial attack in humans.

Flow of energy through various trophic levels in an ecosystem is unidirectional and non-cyclic. Explain.

Mention ‘a’ and ‘b’ in the following flow chart. Why is its importance (technique shown in following flow chart) increasing?

Habit and nature of bees

↓

Selection of location

↓

Catching and having of swarms

↓

a

↓

b

Make a list of three household products along with the names of the microorganisms producing them.

What are exotic species? Explain with the help of two examples how the exotic species disturb the native species of an ecosystem?