Class 12 Biology

Few problems along with their solutions from this chapter are given follows:

Q. Ecotone is

(a)a polluted area

(b)the bottom of a lake

(c)a zone of transition between two communities

(d)a zone of developing community

Ans. (c) a zone of transition between two communities

The adjacent biotic (natural) communities generally do not possess a fine demarcation edge or line between them. The adjacent of two communities is represented by population of both the communities, and this transition zone between two communities is referred as ecotone.

Q. What is diapause and its significance?

Ans. Under unfavourable conditions many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.

Q. What is brood parasitism? Explain with the help of an example.

Ans. Brood parasitism is the phenomenon in which an organism (parasite) lays eggs on the nest of other organism (host). e.g., Cuckoo (koel) bird lays its eggs in the nest of its host and lets the host incubate them. The eggs of the parasitic bird resemble the host's egg in size and colour to reduce the chances of the host bird detecting the foreign eggs«and ejecting them from the nest.

Q. Do you agree that regional and local variations exist within each biome? Substantiate your answer with suitable example.

Ans. A biome can be define as the large communities of the world a-; shows that area with similar climate have communities of same type. Climate is the mar factor that determines the type of soil which in turn determines the type of vegetation. The type of vegetation and climate together determine the kind of microorganisms and animals.

The other determining factors are latitude and altitude, intensity and duration of winter and summer days, water mass and topography. The main biome of the world does not show boundary of any country and regional and local variations exist in each biome.

e.g., temperate deciduous forest receives an annual precipitation between 75-150 cm and tropical rain forest show a rainfall above 140 cm/yr which may reach up to 400 cm/yr.