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Biography is the study of the distribution of animals and plants in the world. It is a subfield of geography that studies spatial patterns of diversity. ‘Bios’ means life, o bhu means earth and ‘graphy’ means writing.
Some scientists state that near the end of the Palaeolithic era some 250 million years ago, all present-day continents formed a large, irregular terrain known as the Pangia. All the oceans together were called pantheias. The landmass first split to form Gondwana land and Laurussia. They eventually split up and the younger landowners rose to their current positions. As the continents drifted, the seas separated them, creating obstacles to the transcontinental movements of organisms. The organisms gradually evolved in their different environments.
The Earth is divided into six biographical locations based on the distribution of animals and plants. They are
1. Australian Territory
2. Tropical Tropical Region
3. Ethiopian Region
5. Spheric Area
6. Controlled Area
-> First proposal for birds by PLSclater in 1857
-> Proposed for animals by ARWallace in 1876
-> No relation to political boundaries
-> Separation of each other by major barriers of sea, mountain or desert.
In some cases descendants of a common ancestor live on different continents and differ from each other. This is called discrete distribution.
(i) Crocodiles – Crocodiles exist only in southeastern USA and eastern China. The North American continent was connected with East Asia in the early Cenozoic by a land bridge in the Bering Strait. The climate of the whole was much warmer than present, and crocodiles, as fossil evidence suggests, were distributed throughout the region. In the later Cenozoic, climate change, due to the ice age, led to the extinction of crocodiles in much of the region. The southeastern United States and East China remained unaffected by glaciers, and crocodiles survived here. Since the alligators of the two regions have long diverged, they have developed different random mutations. Therefore, they are high, but closely related species in the same genus.
(ii) Lung Fishes – In the early stages of continental drift, South America, Africa, Antarctica and Australia were interconnected. Lung fishes can originate in interconnected areas. Later, the continents separated. Antarctica moved to a distant location. Lung fishes are now found, a species in South America, South Africa and South Australia.
We looked at Pangean theory, biographical reams, and discontinuous distributions in this session. In the next session, we can go deeper into the topics.