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Biomes Overview

Definition: Biomes are large ecological areas on Earth’s surface, defined primarily by their climatic conditions, geography, and the plant and animal life that inhabit them. Each biome consists of many ecosystems that share similar environmental features and biodiversity.

Major Classes: There are five main classes of biomes:

1. Aquatic

2. Forest

3. Grassland

4. Desert

5. Tundra

Key Characteristics: Each biome has distinct features, including specific limiting factors like temperature, moisture, and nutrient availability, that influence productivity and species diversity.

Major Biomes of the World

The major biomes include the following:

1. Tundra

2. Northern Conifer Forest (Taiga)

3. Tropical Rain Forest

4. Tropical Deciduous Forest

5. Desert

6. Temperate Deciduous Forest

7. Tropical Chaparral & Rain Forest

8. Grasslands & Savanna

9. Mountains

10. Tropical Scrub Forest

11. Temperate Grassland

Main Biomes

Tropical Rainforest

• Location: Typically located near the equator, within 5 degrees North and South latitude.

• Climate: Characterized by consistently warm temperatures and high humidity, these biomes receive about 200-500 cm of rain annually, with daily temperatures averaging between 26°C and 28°C.

• Ecological Role: Although they cover only about 6% of the Earth’s surface, tropical rainforests are crucial as they produce about 40% of the world’s oxygen and are pivotal in carbon storage.

• Soil Characteristics: Due to leaching, the soils in these forests are often nutrient-poor, making them less suitable for agriculture without specific amendments.

• Biodiversity: Rainforests are one of the most biodiverse ecosystems on the planet, housing approximately 50% of all known plant and animal species.

Structure of Tropical Rainforest

• Multi-storey profile:

  1. Emergent trees can reach heights of up to 55 m, providing habitat for many bird species.

  2. Vines, climbers, and epiphytes thrive in the canopy, competing for sunlight.

  3. An understory composed of smaller trees and shrubs thrives in dim lighting, supporting various species.

  4. The forest floor receives very limited light, leading to specific adaptations in the plants growing there.

Nutrient Cycling in Tropical Rainforests

• Net Primary Productivity (NPP): Extremely high NPP (about 40% of global terrestrial ecosystems) driven by rapid decomposition rates, facilitating efficient nutrient recycling.

• Biodiversity Hotspot: Areas with rich species diversity that are under threat from habitat destruction.

• Medicinal Importance: Many plants provide essential medicines; for example, Vincristine, a chemotherapy drug, is derived from the Rosy Periwinkle found in these forests.

Deserts

• Characteristics: Noted for their extremely low biodiversity and harsh living conditions, with temperature variations that can reach extremes between hot days and cold nights.

• Climate: Deserts generally lie around 30° N or S latitude, receiving less than 25 cm of rain per year.

• Plant Adaptations: Species such as cacti have developed adaptations for drought, like water-storing features and evolved methods to minimize water loss during transpiration.

Types of Deserts

1. Hot Deserts: (e.g., Sahara, Gobi) known for high temperatures.

2. Cold Deserts: (e.g., Atacama) which can have cold temperatures, particularly during nights.

Human Impact

• Activities: Human activities such as nomadic livestock grazing, mining, and oil drilling contribute to the risk of desertification and environmental degradation, impacting the delicate balance of these biomes.

Grasslands

• Types:

  1. Temperate Grasslands (Prairies): Located mainly across North America and parts of Europe, characterized by moderate rainfall and seasonal temperature changes.

  2. Tropical Grasslands (Savannas): Found in regions like Africa and South America, supporting large herbivores and adapted to seasonal droughts.

• Characteristics: Grasslands typically receive between 25-75 cm of precipitation annually, with limited tree growth due to factors like grazing and periodic wildfires, which help maintain the ecosystem.

Deciduous Forests

• Description: Commonly found in the northeastern United States, Europe, and parts of Asia, these forests experience four distinct seasons.

• Climate: Moderate with varying temperatures and significant seasonal changes.

• Biodiversity: Rich in species diversity, though not as extensive as tropical rainforests, it supports various mammals, birds, and insect species.

• Nutrient Cycling: Despite being the second highest for NPP, these forests also have efficient recycling of nutrients, primarily due to substantial leaf litter decomposition.

Taiga (Boreal Forest)

• Location: The largest biome, characterized by coniferous tree species, primarily found in Canada, Alaska, Russia, and northern Europe.

• Climate: Features long, cold winters with significant snow and short, mild summers.

Tundra

• Description: Located around the North Pole and the Arctic Ocean, known for extremely cold and dry conditions, with significant portions of the ground covered by permafrost that prevents deep root growth.

• Challenges: The harsh climate limits biodiversity, with flora adapted to extreme temperatures and low nutrient availability.

Water Biomes

• Types:

1. Marine: Comprises about 70% of the Earth's surface, including vast oceans and saltwater habitats.

2. Freshwater: Encompasses lakes, ponds, rivers, and streams which typically contain low salinity.

3. Estuaries: Transition areas where freshwater and marine environments meet, known for high biological productivity and biodiversity.

• Human Impact: Pollution, overfishing, habitat destruction, and climate change significantly threaten marine ecosystems and the species that rely on them.