Distribution of Animals ,Mean of dispersion, and Barrier to distribution.

 DISTRIBUTION OF ANIMALS:

All animal are not uniformly distributed in all world, because of  environmental condition and other factors that restrict some animal to certain area of the world.

Animals are classified into three categories on the basis of distribution.

• Continues distribution.
• Discontinues distribution.
• Bipolar distribution.

• Continues distribution:
• The uniform or nearly uniform  distribution of most of the animal in whole world is called continues or eurytopic distribution.
• In eurytopic distribution animals have great ability to survive every environmental condition.
• They eat variety of food in order to face different environmental condition.
• They have ability to cross different barrier by swimming, rafting and flying.

Example :

Rat ,Bat ,Lizards, snake ,most of the birds, are some example of continues distribution.

• Discontinues distribution:
• The type of animal distribution in which animals are restricted to certain area of the world is called discontinues or stereotypic distribution of animals.
• In stereotypic distributed animals depend on specific type of food and ,can not cross the barriers of dispersion, and animals are  restricted to certain area of the world.
• According to Darlington animals show discontinues distribution because of  extinction from particular area, by natural hazards, presence of large number of predators are the major cause of discontinues distribution.

Example:

 Peripatus connecting link between Arthropoda and Annelida is found in America Africa ,and news          land.

  Lung fishes also distributed discontinuously, only found in Australia, Africa and America. 

   Kiwi are found only news land, show  discontinues distribution. 

• Bipolar distribution:
• The animals that are restricted in only polar region, and adopt themselves in cold condition due to presence of ice and cannot migrate to warmer places is called bipolar distribution.
• Example:-Polar bear ,and arctic fox are the example of Bipolar distribution.

MEANS OF DISPERSION:

Animals move from one place to an other place in search of food or better environment for survivals. Animals use following means to move from one place to another place.

• By  mean of land bridge
• By mean of air
• By water of water
• Human agency.

• Land bridges:
• Land bridges connection two large part of earth which are separated by sea. Land bridges exist in the past and facilitate movement of animal across them. The theory of land bridges was formulated to explain discontinues distribution.

• By Mean of air:
• Air can carry spore of plant from one place to an other place and help in dispersion of plants.
• Air facilitate migration of birds from one place to an other pace.
• Birds legs consist of eggs of varies animal that disperse from one place to an other place by movement of birds.

• By means of Water:
• Water facilitate migration of those  animal that can swim in water from place to place.
• Water become a barrier for land animals.

BARRIER TO DISPERSION:

• The object that that restrict animal migration and due them animal restrict a limited area of earth is called barrier to dispersion. Barrier are relative no absolute.
• There are three type of barrier:

• Physical barrier.
• Climatical or Ecological barrier.
• Biological Barrier.

PHYSICAL BARRIER:

Physical barrier are mainly following types:

• Topographical barrier.--High mountain.
• Water bodies barrier for land animals.
• Desert barrier.
• Grass land barrier.

ECOLOGICAL BARRIER:

• It includes.
• Temperature.
• Humidity.
• Air pollution.
• Rain fall.

BIOLOGICAL BARRIERS:

Biological barrier includes.

• Predators for prey.
• Prey for predators.