Question

Select the correct statements with respect to migration in animals.
a. The same Siberian crane can be seen in Bharatpur in two consecutive winters.
b. Some fish lay eggs in rivers and the fingerlings gradually swim to sea.
c. Some fish migrate from cold climates to warmer climates to escape cold weather.
d. Some butterflies migrate up to 10,000 kilometers to escape cold weather.

Which of the following alternatives has the correct statement?
A. a and b
B. b and c
C. c and d
D. a and d

Answer 1

Hint: Organisms have different mechanisms to protect themselves from harsh conditions. One such mechanism is migration. It is most commonly followed to protect from the winter conditions of their habitat.

Complete Answer:
When organisms move in large numbers from one place to another, it is called migration. It is usually a periodic and a regular phenomenon as they perform it under specific conditions. But some migrations can occur for their lifetime and are then called a single migration. On the other hand, some of the birds and animals migrate to come back to their habitats. When these birds travel, they travel in groups.

Some of the factors which affects migration are:
- Climatic conditions
- Shelter
- Food availability
- Natural calamities

- When the conditions are not favorable, the biodiversity in a region decreases and causes the organism to shift to other places. Similar case is seen with the Siberian cranes which migrate from Siberia to India during winters.
- The harsh climate in their habitat makes them relocate to Bharatpur in Rajasthan. During the months of October to March/April, they make Bharatpur their home. They also fly to other parts of India. So, the same Siberian crane can be seen in Bharatpur in two consecutive winters.
- Fishes also migrate to smaller or larger distances daily or once in a year but the reasons for this migration is not due to cold climatic conditions. It is mainly due to reproductive or food related needs.
- Butterflies migrate to escape the harsh cold climatic conditions. One of the butterflies known as the Monarch butterfly migrates during the winters. It rests during the winters so that they can save energy for their return in the spring seasons. They make use of a combination of air and thermal to travel.

So, the correct option is (D).

Note: Organisms migrate to escape the cold climatic conditions of their habitat. Some common examples of migration include Siberian cranes and monarch butterflies. There is a reduction in biodiversity in the place from where they have migrated and the biodiversity increases at places where they have migrated to.