Question

what are the various types of geographical barriers?Discuss the role of these barriers on the distribution of animals​

Answer 1

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The following points highlight the top two barriers to animal distribution. The barriers are: 1. Extrinsic Barriers 2. Intrinsic Barriers.

Animal Distribution: Barrier # 1. Extrinsic Barriers:

Those barriers working from outside of an individual’s body of the population are extrinsic barriers.

Extrinsic barriers are gene­rally of three types:

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(a) Physiographic

(b) Biotic and

(c) Climatic barriers.

(a) Physiographic Barriers:

Different’ physical and geographical obstacles, which act as barriers are included in this type.

It can further be described under following heads:

(i) Topographical Barriers.

(ii) Large bodies of Water.

(iii) Large bodies of Land Masses.

(iv) Impurity and Lack of Salinity of Sea Water.

(v) Vegetative Barriers.

(vi) Desert.

(vii) Pressure and

(viii) Ice mass.

(i) Topographical Barriers:

High and extensive mountain ranges limit the distribu­tion of animals, e.g., Himalaya. This fange is situated more or less parallel to the equator. On the south of this range is hot and moist plains of India, with a very distinct tropical fauna, like elephant, tiger, etc.

This resembles the faunal type of Africa. Whereas on the northern part of the mountain the climate is colder and the fauna is more or less similar to that of Europe, like oxeny, gibbons, etc.

(ii) Large Bodies of Water:

Giant river systems and oceans act as effective barriers for Tand animals, specially flightless animals- like amphibians, reptiles, etc. Fresh water fishes cannot survive in marine water and similarly marine animals cannot survive in fresh water.

However, during breeding peri­od some fishes migrate from their normal habitat to other places. When fresh water fishes migrate to the saline water, it is called ‘catadromous migration’ (e.g. byne, eel) and when marine fishes migrate to the fresh­water, it is called ‘anadromous migration’ (hilsa, sad, salmon, etc.).

In most of the cases a small amount of salt water often is an absolute barrier for amphi­bians. For this reason, the Pacific islands are completely uninhabited by amphibians, unless they are introduced by man, e.g., Hawaii.

In India, Brahmaputra and Ganges with their tributaries obstruct the distribution of some forest animals.

(iii) Large Land Masses:

Both fresh­water and marine animals find large land masses as barrier to their distribution.

(iv) Impurity and Lack of Salinity in Sea Water:

Most of the corals are found in the clear sea basins, because they cannot survive in dirty or impure waters. For that reason extensive coral reefs or sponge-growing areas are never found near the mouth of large rivers, such as Ganges, Amazon, Orinoco or Mississippi, each of which bears a great load of seaward flowing sediments.

Similarly, there are some corals, sponges and brachiopods which cannot withstand slightest change in salinity of the sea water