Animals are not uniformly distributed across land and water due to factors like climate, food availability, shelter, and other species. Their distribution can be categorized as continuous, discontinuous, endemic, isolated, or bipolar. Continuous distribution means worldwide presence. Discontinuous distribution occurs when habitat is broken up, such as by oceans or changing land masses. Endemic distribution confines species to particular regions. Isolated and bipolar distributions restrict some animals only to specific isolated areas like Australia or polar regions.

1. ANIMAL DISTRIBUTION
• Animals are not uniformly distributed on land and in freshwater. They are restricted to certain places by
several factors such as climate, food, shelter, flora and fauna etc
• All the living organisms in a given region are termed as Biota of that region.
• Generally distribution can be classified into categories, namely,
1. Continuous/ Cosmopolitan
2. Discontinuous Distribution
3. Endemic Distribution
4. Isolated Distribution
5. Bipolar Distribution.

2. • 1. Continuous/ Cosmopoliton distribution.
• World wide distribution
• Animals may be Eurytopic and Stentopic
• They are well adapted.
• Eurytopic or wide-ranging animals are adapted to a wide variety of environmental
conditions and are not specific to any particular type of food or may have special power to
cross barriers either by flight, rafting or swimming and adapt to new environmental
conditions. Wide ranging animals include rats, bats, hawks, cuckoos, cockroaches, flies,
mosquitoes, lizards, snakes and man. Many of the eurytopic animals have continuous
distribution because they are companions of man and have travelled to long distances with
him.

3. • Discontinuous distribution:
• When continuity of distribution of a species is broken by uninhabited areas which are
sometimes very large stretches of oceans. There are primarily four reasons why animals
are distributed in widely separated areas.
1. Water:
• Animals reach distant areas by sweepstake routes, as insects, snails and rats by rafting,
turtles by floating and swimming and birds blown by storms.
2. Land mass:
• The species was earlier distributed continuously but the land masses in the
intermediate areas submerged, breaking the species into widely separated
populations.

4. • 3. Long Distance:
• Continental drift separated the continents and carried them to long distances, isolating the
animals from other areas.
• 4. Extintion:
• A widely distributed species can become extinct in the intermediate areas due to change in the
climate to which the species is unable to adapt.
• Examples:
• The common camel (Camelus dromidarius) occurs in the Middle East, India and Northern
Africa; Camelus bactrianus is found in Mongolia and China, while two
species, Llamavicuna and Llama guanaco are found in the mountainous regions of South
America.

5. • Example of Discontinous
• The two elephant species surviving today, Loxodonta africana occurs in Africa while
another species, Elephas maximus is found in India, Burma, Thailand and Sri Lanka.
• Alligators occur in America and China; Alligator mississipiensis in Americas, Caiman in
South America and Alligator sinensis in China.

6. • 3. Bipolar distribution:
• Animals are present at both poles and absent in tropical regions.
• Some species because they are adapted to the cold arctic climate cannot migrate to the
warmer areas and hence restricted to the Polar Regions. Polar bears, arctic fox,
lemmings, coyote and reindeers are found in the northern Polar Regions while penguins
are restricted to the Antarctica region. Among fishes, salmons migrate up to the temperate
and polar tributaries for breeding.
Other polar species are Coelenterates (Lampra, Myriothela, Grammaria, Ptychogastria,
Botrynema, Sardina). Mollusca (Limacina, Clione). Urochordata (Didemnus), an ascidian.

7. • Endemic Distribution:
• Endemic, species which are confined or restricted in geographical distribution to an area or
region. The area or region can vary in size, and is defined or identified in different ways.
Endemism is an ecological classification in that it describes the range or distribution of
a species, or group of species. For instance, entire families of different species of birds are
endemic to the island of Madagascar.
• E.g Nilgai, Giraffe, Armadillos, found ony in neotropical regions.

8. • Isolated Distribution.
• Some Animals found only isolated themselves to a specific areas, such forms are said
to have isolated distribution. e.g. marsupials (Duckbill platypus, Kangaroo) are
isolated to Australia.
• Sphenodon reptile isolated to New Zealand.