Biogeography is the branch of science that studies the distribution of plants (flora) and animals (fauna) across the Earth. It explains why certain sp

Biogeography – Distribution of Flora and Fauna

Biogeography is the study of the distribution of living organisms—both plants (flora) and animals (fauna)—across different regions of the Earth and through geological time. It investigates why certain species are found in specific places, how geographical and climatic factors shape biodiversity, and how historical events like continental drift and glaciation influenced the spread of life.

Understanding biogeography is essential not only for academics but also for conservation, ecology, and climate change studies. It helps us appreciate the uniqueness of ecosystems, predict future biodiversity patterns, and develop strategies to protect endangered species.

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What is Biogeography?

Biogeography comes from two words: “bio” (life) and “geography” (earth’s surface). It is the branch of science that examines:

• The distribution of species across continents, islands, and habitats.

• The factors responsible for their presence or absence.

• The evolutionary history of organisms and how they adapted to different environments.

Two major subdivisions exist:

1. Phytogeography (Plant Geography): Deals with the spatial distribution of plants.

2. Zoogeography (Animal Geography): Deals with the spatial distribution of animals.

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Historical Development of Biogeography

The study of biogeography began centuries ago, with early explorers noticing that plants and animals differed greatly between regions. Some key milestones include:

• Age of Exploration (15th–17th centuries): European travelers observed unique species in new lands, like kangaroos in Australia and llamas in South America.

• Carl Linnaeus (1707–1778): The father of taxonomy, who classified plants and animals systematically, aiding the study of their distributions.

• Alexander von Humboldt (1769–1859): Considered the father of biogeography, who studied vegetation zones across altitudes and climates.

• Charles Darwin (1809–1882): Through his voyage on the HMS Beagle, Darwin studied species differences on the Galápagos Islands, leading to his theory of evolution by natural selection.

• Alfred Russel Wallace (1823–1913): Known as the father of zoogeography, Wallace identified faunal boundaries, most famously the Wallace Line separating Asian and Australian species.

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Factors Affecting Distribution of Flora and Fauna

The presence and spread of living organisms on Earth is not random. Several interrelated physical, climatic, biological, and historical factors influence where species live.

1. Physical Factors

• Topography: Mountains, valleys, and plateaus influence plant and animal life. For instance, alpine plants grow only at high altitudes.

• Soil Type: Rich volcanic soils support dense forests (e.g., Java, Indonesia), while sandy deserts support sparse vegetation like cacti.

• Water Availability: Wetlands and river systems sustain diverse species compared to arid deserts.

2. Climatic Factors

• Temperature: Polar regions are home to species like polar bears and mosses, while tropical climates support rainforests and diverse fauna.

• Rainfall: Deserts like the Sahara have drought-resistant plants (xerophytes), while rainforests like the Amazon host dense vegetation.

• Sunlight: Determines photosynthesis rates, thus affecting plant productivity and food chains.

3. Biotic Factors

• Competition: Species compete for food, water, and shelter. Stronger species dominate and limit others’ distribution.

• Predation: Presence of predators affects the survival and spread of prey species.

• Mutualism: Some plants and animals depend on each other, like bees and flowers.

4. Historical and Geological Factors

• Continental Drift: The breakup of Pangaea caused species to evolve separately on different continents.

• Glaciations: Ice ages forced species to migrate, adapt, or go extinct.

• Evolution and Speciation: Isolated populations adapted uniquely, leading to endemic species.

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Major Biogeographic Realms of the World

The Earth has been divided into several biogeographic realms (large areas with distinct plants and animals). These were first proposed by Wallace and later refined.

1. Nearctic Realm (North America)

   • Includes Canada, USA, and parts of Mexico.

   • Flora: Coniferous forests, prairies.

   • Fauna: Bison, pronghorn antelope, black bear.

2. Neotropical Realm (South America & Central America)

   • Rich biodiversity due to the Amazon rainforest.

   • Flora: Tropical hardwood trees, orchids.

   • Fauna: Jaguar, llama, toucan, anaconda.

3. Palearctic Realm (Europe, North Africa, Asia north of Himalayas)

   • Largest realm with varied climate zones.

   • Flora: Oak, pine, tundra vegetation.

   • Fauna: Wolf, reindeer, camel.

4. Afrotropical Realm (Africa south of Sahara, Madagascar)

   • Known for its savannas and deserts.

   • Flora: Acacia, baobab.

   • Fauna: Lion, elephant, giraffe, zebra.

5. Indomalayan Realm (Indian subcontinent, Southeast Asia)

   • Tropical monsoon climate supports dense forests.

   • Flora: Teak, bamboo, mangroves.

   • Fauna: Tiger, Asian elephant, orangutan.

6. Australasian Realm (Australia, New Guinea, Pacific islands)

   • Home to unique marsupials due to isolation.

   • Flora: Eucalyptus, acacia.

   • Fauna: Kangaroo, koala, platypus, cassowary.

7. Oceanian Realm (Pacific Islands excluding New Guinea)

   • Small islands with many endemic species.

   • Flora: Coconut palms, ferns.

   • Fauna: Flightless birds, reptiles.

8. Antarctic Realm

   • Harsh climate with limited life.

   • Flora: Lichens, mosses.

   • Fauna: Penguins, seals, whales.

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Distribution of Flora

The world’s plant life is distributed into different biomes based on climate and geography.

1. Forests

• Tropical Rainforests: Found near the equator (Amazon, Congo). Extremely diverse with tall evergreen trees.

• Temperate Forests: Found in North America, Europe, and East Asia. Deciduous trees like oak and maple dominate.

• Coniferous Forests (Taiga): Found in Canada and Siberia. Dominated by pine, spruce, and fir trees.

2. Grasslands

• Savannas: Found in Africa, Australia, South America. Home to scattered trees and grasses.

• Temperate Grasslands (Prairies, Steppes): Found in North America, Central Asia. Fertile soils support farming.

3. Deserts

• Sparse vegetation due to low rainfall.

• Plants: Cacti, succulents, shrubs.

4. Tundra

• Found in polar regions.

• Plants: Mosses, lichens, dwarf shrubs adapted to cold.

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Distribution of Fauna

Animal distribution also depends on climate, vegetation, and food availability.

1. Tropical Regions

• Rich biodiversity: Tigers, monkeys, reptiles, birds, insects.

• Example: Amazon rainforest (over 2.5 million insect species).

2. Savannas and Grasslands

• Home to grazing animals and large carnivores.

• Example: African savanna with lions, zebras, wildebeest.

3. Deserts

• Animals adapted to drought.

• Example: Camels, fennec fox, reptiles.

4. Polar and Tundra Regions

• Fauna includes polar bears, reindeer, seals, penguins.

5. Marine Life

• Oceans host immense biodiversity: whales, dolphins, sharks, corals.

• Coral reefs (like the Great Barrier Reef) are biodiversity hotspots.

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Endemism and Biodiversity Hotspots

Some species are endemic (found only in one location). For example:

• Kangaroos in Australia.

• Lemurs in Madagascar.

• Giant pandas in China.

Globally, biodiversity hotspots are areas rich in endemic species but under threat from human activities. Examples include:

• Himalaya (Indo-Burma region).

• Sundalands (Indonesia, Malaysia).

• Amazon basin.

India itself is recognized as one of the 17 megadiverse countries with hotspots like:

• The Himalaya,

• Indo-Burma,

• Indo-Malayan region,

• Nicobar and Andaman islands.

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Human Impact on Biogeography

Human activities are rapidly altering natural distributions:

• Deforestation reduces natural habitats.

• Urbanization fragments ecosystems.

• Pollution and climate change shift species ranges.

• Introduction of invasive species disrupts native ecosystems.

Example: Introduction of rabbits in Australia caused ecological imbalance, threatening native species.

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Importance of Studying Biogeography

1. Conservation Planning: Helps identify biodiversity hotspots needing protection.

2. Understanding Climate Change: Predicts shifts in species ranges.

3. Agriculture and Forestry: Guides crop and tree plantation strategies.

4. Disease Ecology: Tracks how diseases spread across regions through animal migration.

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Conclusion

Biogeography reveals the fascinating story of life’s distribution across Earth. From lush Amazon rainforests to icy Antarctic deserts, every region has unique plants and animals shaped by climate, geography, and history.

In today’s world of rapid environmental change, studying biogeography is more crucial than ever. It not only helps us understand past and present biodiversity but also equips us to safeguard ecosystems for the future.

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Related Posts

1. Tropical Rainforest Ecosystem – Characteristics and Importance

2. Endangered Species of India and Their Conservation Efforts

3. The Role of Climate Change in Biodiversity Loss

4. Major Biomes of the World Explained

5. Continental Drift and Its Impact on Species Distribution