Notes Class 11 Chapter 8 Geography Maharashtra Board

Biomes

Introduction to Biomes

A biome is a large geographical area where different types of flora (plants) and fauna (animals) coexist under similar climatic conditions. It is defined as the total assemblage of plant and animal species interacting within specific environmental conditions, primarily determined by climate factors such as rainfall, temperature, humidity, insolation, and soil conditions. Biomes differ from ecosystems, which are smaller-scale interactions between biotic (living) and abiotic (non-living) factors, such as soil, water, sunlight, and nutrients, within a biome.

Key Characteristics of Biomes:

• Determined by climatic conditions.
• Contain multiple ecosystems (e.g., a river ecosystem within a tropical rainforest biome).
• Plants and animals are adapted to the specific climate of the biome.
• Trophic levels (food chains and webs) vary by biome, influencing which species occupy each level.

Difference Between Biome and Ecosystem:

• Biome: Large-scale, defined by climate, includes many ecosystems (e.g., tropical rainforest).
• Ecosystem: Smaller-scale, focuses on biotic-abiotic interactions, nutrient flow, and energy transfer (e.g., a pond ecosystem).
• Example: A river in an equatorial region has different species than a river in a temperate region, even though both are ecosystems within different biomes.

Factors Influencing Biomes:

• Latitude: Influences temperature and sunlight, affecting vegetation and fauna.
• Climate: Rainfall, temperature, humidity, and insolation shape biome characteristics.
• Soil Conditions: Fertility and composition impact plant growth.
• Altitude: In mountain biomes, vegetation changes with elevation.

Latitudinal Influence:

• Vegetation: Near the equator (0°), high temperatures and rainfall support dense, broad-leaved forests (e.g., tropical rainforests). At higher latitudes (e.g., 65°-90° N), cold climates support sparse vegetation like mosses and lichens (e.g., tundra).
• Fauna: Equatorial regions have high biodiversity (e.g., monkeys, parrots), while polar regions have fewer species adapted to cold (e.g., reindeer, arctic foxes).
• Biodiversity: Highest near the equator (tropical rainforests) due to favorable climate, decreasing toward the poles.

Terrestrial Biomes

1. Tropical Rainforest Biome

Latitudinal Extent: 0° to 10° N and S (equatorial region).

Climatic Conditions: High rainfall (200-400 cm annually), high temperatures (25-35°C), and high humidity.

Vegetation:

• Extremely high biodiversity; over half of Earth’s species are found here.
• Dense, broad-leaved, evergreen trees (up to 50 m tall) form a canopy, blocking sunlight.
• Three-layered structure:
  1. Understory: Dense bushes and ground cover.
  2. Mid-layer: Low trees and climbers/creepers.
  3. Canopy: Tall, hardwood trees (e.g., mahogany, ebony, rosewood, rubber, palms, coconut, orchids, ferns).
• Fertile soils rich in humus due to rapid decomposition.

Animal Life:

• Diverse species, including monkeys, vultures, hornbills, parrots, insects, butterflies, and reptiles.
• Each species occupies a specific niche within the three-tier forest structure.

Human Life:

• Indigenous communities (e.g., Pygmies in Congo, Boro Indians in Amazon, Sentinels in Andaman and Nicobar) engage in hunting and gathering.
• Primitive lifestyle due to dense forests and humid climate.

Use of Biome:

• Hardwood used for construction and furniture.
• Overexploitation in regions like Brazil and Java-Sumatra for timber and agriculture.

Current Status:

• Degradation due to agriculture, industrialization, and deforestation.
• Threatened species: Golden lion tamarin, gorilla, orangutan, harpy eagle, chimpanzee, poison dart frogs.
• New species still being discovered.

Major Countries: Brazil, Congo, Indonesia, Malaysia, India (Andaman and Nicobar).

2. Tropical Deciduous Biome (Monsoon Biome)

Latitudinal Extent: 5° to 30° N and S.

Climatic Conditions: Distinct wet and dry seasons, moderate rainfall (100-200 cm), warm temperatures.

Vegetation:

• Deciduous trees shed leaves in the dry season and regrow in the wet season.
• Less dense than rainforests; trees grow in groups, not continuously.
• Key species: Teak (economically valuable), sal, rosewood, sandalwood, bamboo, oiltree.
• Shorter trees and shrub-like vegetation in drier areas.

Animal Life:

• Second-highest biodiversity globally.
• Fauna includes elephants, rhinos, tigers, lions, monkeys, greater coucal, hornbills, peacocks, vultures, ants, butterflies, and worms.
• Many species suitable for domestication.

Human Life:

• Easier than in rainforests; supports primary (forestry) and secondary (animal husbandry) occupations.
• Tribal communities and rural/urban settlements exist.
• Encroachment due to expanding human settlements.

Use of Biome:

• Teak used for furniture, construction, shipbuilding, and railway berths.
• Sandalwood for oil and scented wood; bamboo for construction and agriculture.
• Fruits and spices extracted for commercial use.

Current Status:

• Threatened by deforestation, wildfires, and excessive use of fertilizers/insecticides.
• Endangered species: White-rumped vulture.

Major Countries: India, Thailand, Myanmar, Brazil, Mexico.

3. Savanna Grassland Biome

Latitudinal Extent: 10° to 20° N and S.

Climatic Conditions: Warm temperatures, moderate rainfall (50-100 cm), distinct wet and dry seasons.

Vegetation:

• Continuous cover of tall, coarse, broad-leaved perennial grass (3-6 m, known as elephant grass).
• Few shrubs and trees, supporting grass-eating animals.

Animal Life:

• Rich in herbivores: Antelopes, buffalo, zebras, rhinos, giraffes, elephants, warthogs.
• Carnivores: Lions, leopards, cheetahs, wild dogs, jackals, hyenas.
• Birds: Vultures, great Indian bustards, ostriches.
• Seasonal grass color changes provide camouflage.

Human Life:

• Difficult due to sparse vegetation; inhabited by tribes like Masai in Africa, who rear cattle.
• Historically used for hunting (“heaven for hunting”).

Use of Biome: Trophy hunting in the past; now limited due to conservation efforts.

Current Status:

• Frequent forest fires and overgrazing reduce biodiversity.
• Industrialization and agriculture reduce grassland extent, contributing to desertification (e.g., Sahara expansion).

Major Countries: Brazil, Australia, South Africa, Tanzania, Kenya.

4. Tropical Desert Biome

Latitudinal Extent: 20° to 30° N and S.

Climatic Conditions: Extremely low rainfall (<25 cm), high temperatures (daytime 40-50°C, nighttime near 0°C).

Vegetation:

• Sparse, dispersed vegetation: Date palms, acacia, khejari, cacti, century plants.
• Adaptations: Thick, water-storing leaves, thorny structures to reduce evaporation, trunk-like leaves for photosynthesis.

Animal Life:

• Limited biodiversity; small animals adapted to heat and low water.
• Species: Camels, snakes, lizards, desert turtles, rats, mongoose, goats, sheep, donkeys.
• Birds: Ostriches, desert eagle owls, sand larks.
• Insects: Beetles, moths, termites.

Human Life:

• Harsh conditions limit settlements to oases; nomadic lifestyle (e.g., Bedouin tribes).
• Agriculture possible with irrigation; animal husbandry practiced.

Use of Biome:

• Dates as a key food item.
• Mineral extraction due to minimal vegetation.

Current Status:

• Desertification spreading to nearby regions (e.g., Nile valley) due to sand transport.

Major Countries: Egypt (Sahara), Saudi Arabia (Arabian), Chile (Atacama), Australia.

5. Mediterranean Biome

Latitudinal Extent: 30° to 40° N and S.

Climatic Conditions: Mild, wet winters and hot, dry summers; moderate rainfall (50-100 cm).

Vegetation:

• Mixed evergreen and deciduous trees with waxy, thick leaves to reduce evaporation.
• Species: Rosemary, cork, oak, olive, eucalyptus, peach, pine, sweet chestnut, cedar, cypress.
• Shrubs with colorful flowers.

Animal Life:

• Mammals: Rabbits, deer, goats, pigs, brown bears, foxes.
• Birds: Vultures, eagles.
• Reptiles, alligators, insects, and honeybees.

Human Life:

• Pleasant climate supports flourishing human settlements.
• Industries: Wine production, olive oil processing, fruit canning, perfume making, tourism, cinema.

Current Status:

• Urbanization and tertiary activities reduce biodiversity.

Major Countries: Spain, Italy, Greece, California (USA), Chile, South Africa.

6. Temperate Deciduous Biome

Latitudinal Extent: 40° to 50° N and S (eastern parts of continents).

Climatic Conditions: Cold winters, warm summers, moderate rainfall (75-150 cm).

Vegetation:

• Broad-leaved, deciduous trees in three layers: tall trees (18-30 m), short trees, and shrubs.
• Species: Beech, elm, chestnut, oak, willow, cherry, maple, pine, walnut, deodar.

Animal Life:

• Animals with thick fur: Brown bears, red foxes, sable, mink.
• Birds: Peregrine falcons, woodpeckers, cardinals.
• Diverse insects.

Human Life:

• Forests provide food, wood, and oxygen.
• Wood used for paper, furniture, and construction.
• Encroachment for agriculture reduces forest cover.

Current Status:

• Reduced due to agriculture and settlements.
• Animals enter human areas due to habitat loss, leading to conflicts (e.g., grizzly bear attacks in Yukon).

Major Countries: USA, Canada, China, Japan, Germany.

7. Temperate Grassland Biome

Latitudinal Extent: 40° to 55° N and S.

Climatic Conditions: Moderate rainfall (25-75 cm), cold winters, warm summers.

Vegetation:

• Soft, dominant grasses: Purple needle grass, blue grama, buffalo grass, galleta.
• Few trees (willow, elder, poplar) near streams.
• Flowers: Asters, coneflowers, sunflowers.

Animal Life:

• Herbivores: Gazelles, zebras, horses, deer, rabbits.
• Carnivores: Coyotes, dingos.
• Birds: Ostriches (Veld), kangaroos (Downs).

Human Life:

• Sparse settlements; historically used for hunting.
• Now supports extensive agriculture (maize, wheat) and livestock rearing (meat, milk, wool).
• Exporters: USA (Prairies), Argentina (Pampas), Australia (Downs).

Current Status:

• Overgrazing and commercial agriculture reduce meadows and pastures.

Major Countries: USA, Russia, Argentina, Australia, South Africa.

8. Taiga Biome (Boreal Forest)

Latitudinal Extent: 50° to 65° N.

Climatic Conditions: Long, cold winters; short summers; low rainfall (40-100 cm).

Vegetation:

• Evergreen coniferous forests with one dominant tree species.
• Species: Spruce, fir, pine, juniper, cedar, larch, oak, hemlock.
• Waxy leaves and conical shapes prevent snow accumulation.
• Fruit trees: Raspberry, salmonberry, blueberry.

Animal Life:

• Thick-furred animals: Reindeer, grizzly bears, elk, caribou (herbivores); foxes, mountain lions, pumas (carnivores).

Human Life:

• Sparse settlements due to cold climate.
• Lumbering is a major activity (softwood for sawmills, paper, furniture).

Current Status:

• Deforestation is easy due to softwood and uniform species, threatening the biome.
• Not found in the Southern Hemisphere due to lack of landmasses at similar latitudes.

Major Countries: Canada, Russia, Finland, Sweden.

9. Tundra Biome

Latitudinal Extent: 65° to 90° N (Arctic regions).

Climatic Conditions: Extremely cold, low rainfall (<25 cm), permafrost layer.

Vegetation:

• Sparse, low-growing plants: Mosses, lichens, small shrubs.
• Trees are absent or stunted, staying close to the ground for insulation.

Animal Life:

• Thick-furred animals: Musk ox, bears, reindeer, lemmings, rabbits (herbivores); Arctic foxes, dogs (carnivores).
• Birds: Ptarmigan, snowy owls, ravens.
• Coastal species: Seals, walruses.

Human Life:

• Sparse settlements; inhabited by Lapps, Samoyeds, Eskimos.
• Traditional hunting and fishing; modern tools increase fish exploitation.

Current Status:

• Global warming melts permafrost, affecting species and snow cover.
• Improved transportation enhances development but threatens the biome.

Major Countries: Canada, Russia, Norway, Greenland.

10. Mountain or Highland Biome

Latitudinal Extent: Not specific; found in high mountain ranges (e.g., Himalayas, Andes, Rockies).

Climatic Conditions: Varies with altitude; cold at higher elevations, windy.

Vegetation:

• Varies with altitude: Deciduous trees (oak, laurel) up to 2000 m, pine up to 4000 m, lichens/mosses beyond.
• Small, perennial plants due to low temperatures and thin soils.

Animal Life:

• Adapted to snow: Deer, bears, wolves, mountain lions, yaks (Himalayas), tigers, monkeys.
• Birds, reptiles, and amphibians vary by altitude.

Human Life:

• Occupations: Crop cultivation (tea, rice, barley), grazing, sheep rearing, tourism (trekking, paragliding).
• Communities: Sherpas, Bakarwals, Lepchas, Bhutias (Himalayas).
• Transhumance (seasonal migration) practiced.

Current Status:

• Over-tourism, deforestation, wildfires, and poaching threaten biodiversity.

Major Regions: Himalayas (India, Nepal), Andes (South America), Rockies (USA).

Aquatic Biomes

Aquatic biomes cover ~70% of Earth’s surface, including oceans, rivers, lakes, wetlands, coral reefs, and estuaries. They are divided into freshwater and marine biomes based on salt content.

Marine Biomes:

• Euphotic Layer (0-200 m): Sunlight supports fish, sea turtles, jellyfish, corals, zooplankton, mangroves.
• Disphotic Layer (200-1000 m): Limited light; hosts squid, cuttlefish, eels, swordfish adapted to darkness and pressure.
• Aphotic Layer (1000-4000 m): No light; bioluminescent species like angler fish and giant squid survive on detritus.
• Deepest Zone (beyond 4000 m): High-pressure environment with animals adapted to detritus.

Freshwater Biomes: Rivers, lakes, wetlands with low salt content, supporting diverse aquatic plants and animals.