Terrestrial & Aquatic Biomes — UPSC Environment Notes

Types of Ecosystems

Ecosystems are broadly categorized into two major divisions:

1. Terrestrial Ecosystem: A land-based community of organisms where biotic and abiotic components interact (e.g., forests, grasslands, deserts).

2. Aquatic Ecosystem: Includes water-based environments, further divided into Marine (oceans) and Freshwater (rivers, lakes) environments.

Biomes

To study terrestrial ecosystems efficiently, we divide them into Biomes. A Biome is a major community of plants and animals that share similar life forms and adapt to similar environmental conditions.

Tropical Evergreen Forest Biome

This biome is the most biologically diverse and productive region on Earth.

1. Distribution

Found between 5 degrees and 10 degrees North and South of the equator.

Major Regions: Amazon Basin (South America), Congo Basin (Africa), and the Indo-Malaysian region (Java, Sumatra, Borneo, Malaysia).

2. Climate

Temperature: Consistently warm and frost-free throughout the year, with a monthly average around 27 degrees Celsius.

Precipitation: Mostly wet throughout the year. Cloudiness and heavy rain help moderate the daily high temperatures.

3. Plant and Animal Species

Flora: Tall, tightly spaced evergreen trees are dominant. Woody vines and climbers (epiphytes) are common. The forest floor is usually dark and shaded by a thick canopy of tree crowns.

Fauna: Includes herbivores like sloths and tapirs; carnivores like jaguars; and various species like monkeys, toucans, and parrots.

4. Productivity

The productivity of this biome is the highest in the world.

It accounts for approximately 40 percent of the total global biological productivity.

Distribution and Location

These forests are found in the tropical regions between 5 degrees and 30 degrees latitude on both sides of the equator.

Key Regions: They are most well-developed in India, Burma (Myanmar), Thailand, Laos, Cambodia, parts of Vietnam, South China, and Northern Australia.

Climate Characteristics

The environment of this biome is defined by a rhythmic cycle of seasons:

Seasons: Characterized by distinct tropical rainy seasons and prolonged dry seasons.

Temperature: Summers are hot, with average temperatures ranging from 27 degrees to 30 degrees Celsius.

Rainfall: The average annual precipitation is approximately 1500mm, mostly concentrated in the monsoon months.

Plant and Animal Species

Flora: The trees are deciduous, meaning they shed their leaves during the dry period to survive drought conditions. While biodiversity is high, there are fewer plant species compared to the evergreen forest biome. Major species include Sal, Teak, and Bamboo.

Fauna: This biome supports large mammals such as rhinos, elephants, tigers, and wild buffalo. It is also home to a vast variety of bird species.

Human Interaction and Economy

This biome is unique because it supports the largest human population in the world.

Agriculture: The primary economic activity is farming. The fertile plains and seasonal rains are ideal for growing major crops like Rice, Sugarcane, and Jute.

Impact: Due to the high population density, large areas of these forests have been cleared for human settlements and intensive cultivation.

Distribution and Regional Names

The Savanna climate is a transitional zone found between the equatorial forests and the hot deserts. It is best developed in Sudan, which is why it is often called the 'Sudan Climate'.

Africa: Extends from West African Sudan to East Africa and Southern Africa.

South America: Known as Llanos in the Orinoco basin (Venezuela/Colombia) and Campos in the Brazilian Highlands.

Australia: Found in Northern Australia.

Climate: The Land of Extremes

Seasons: It has highly distinct wet and dry seasons. Unlike the Monsoon climate, the rainy season is not as long or reliable.

Temperature: The annual average temperature stays above 18 degrees Celsius. The diurnal range (daily difference) is high, with hot days and cold nights.

Plant Adaptation: Park-like Appearance

Because soil moisture is insufficient to support a dense forest, trees are spaced widely apart.

Vegetation Structure: It has an 'open park-like' appearance where tall grasses form a dense lower layer between scattered trees.

Key Species: Famous trees include the Baobab (the 'bottle tree' that stores water), various Palms, and Eucalyptus (in Australia).

Animal Life: The Big Game Country

African Savanna: Hosts the world's largest number of grazing animals (herbivores) like Zebra, Giraffes, Elephants, and African Buffalo.

Australian Savanna: Dominated by Kangaroos.

Human Interaction

The economy is largely tribal and varies by region:

Masai: Located in East Africa, they are primarily pastoralists (cattle herders).

Hausa: Located in Northern Nigeria, they are settled farmers.

Agriculture: Generally underdeveloped due to the extreme dry season and poor soil quality.

Distribution of Hot Deserts

Major hot deserts are found on the western coasts of continents between 15 degrees and 30 degrees North and South latitudes.

Africa: Sahara (largest), Kalahari, and Namib Deserts.

Asia: Arabian, Iranian, and Thar (India/Pakistan) Deserts.

Australia: Great Australian Desert.

Americas: Atacama (driest - South America), and the Mohave, Sonoran, and Mexican deserts in North America.

Climate: Extreme Heat and Scanty Rain

Temperature: Average summer temperatures are around 30 degrees Celsius, but extremes can reach up to 58 degrees Celsius (e.g., Al Azizia, Libya).

Diurnal Range: There is a very high difference between day and night temperatures.

Precipitation: Rainfall is very low, usually below 30 cm annually.

Adaptations: Surviving the Heat

1. Plants (Xerophytes)

Plants in deserts are called Xerophytes. They have specialized features to conserve water, such as:

Thick, fleshy stems to store water.

Spines instead of leaves to reduce water loss through transpiration.

Long root systems to reach deep groundwater.

2. Animals

Common animals include arthropods, reptiles, and small mammals like rodents, foxes, and rabbits.

Adaptation Example: The black-tailed jackrabbit has extra-long ears filled with blood vessels that help radiate excess body heat into the air.

Human Inhabitants

Desert populations are often categorized by their lifestyle:

Primitive Hunters/Collectors: Bushmen (Kalahari) and Bindibu (Australia).

Nomadic Herdsmen: Tuaregs (Sahara), Bedouins (Arabia), and Gobi Mongols.

Others: Caravan traders, settled cultivators near oases, and mining settlers (e.g., copper mining in Atacama).

Distribution and Locations

This biome is found between 30 degrees and 40 degrees latitudes in both hemispheres, typically on the western parts of continents.

Europe/Africa/Asia: Lands bordering the Mediterranean Sea (Southern Europe, North Africa, Western Turkey, Syria, Israel, Lebanon).

North America: Central and Southern California (USA).

South America: Central Chile.

Australia: Coastal zones of Western and Southern Australia.

Africa: The southwestern tip (Cape region).

Climate: Dry Summers and Wet Winters

Unique Feature: Unlike most biomes, the maximum rainfall occurs in winter. Summers are warm and dry.

Temperature: Winters are cool (5-10 degrees Celsius), while summers range from 20-27 degrees Celsius.

Precipitation: Average annual rainfall is between 370mm and 650mm.

Plant Adaptations: Sclerophylls

Plants here are called Sclerophylls. They have small, hard, or thick leathery leaves designed to resist water loss (transpiration) during the long, dry summers.

Trees: Holm oaks, olive trees, laurels, carob, junipers, and cypresses.

Aromatic Herbs: Rosemary, thyme, sage, and oregano.

Animal Life

The biome supports a variety of mammals and birds adapted to hilly and shrubby terrains.

Common Species: Wild goats, sheep, cattle, mouflon (wild sheep), lynx, and wild boar.

Human and Economic Significance

Known as the 'Orchard of the World' for its massive fruit production.

Agriculture: Citrus fruit cultivation (lemons, oranges), cereal production, and olive oil industry.

Viticulture: World-renowned for grapes and winemaking.

Industry: Engineering, mining, and agricultural processing.

Global Distribution and Local Names

Temperate grasslands are found across the globe but are known by specific regional names:

Eurasia: Known as Steppes (stretching from the Black Sea to China).

North America: Known as Prairies (between the Rockies and the Great Lakes).

Argentina & Uruguay: Known as Pampas.

South Africa: Known as Velds (between Drakensberg mountains and Kalahari Desert).

Australia: Known as Downs (Murray–Darling basin).

Climate: Continental vs. Maritime

Northern Hemisphere: Characterized by a Continental Climate with extreme summer and winter temperatures due to their interior location.

Southern Hemisphere: Features a moderate climate because these grasslands are located closer to the sea (maritime influence).

Precipitation: In both hemispheres, rainfall is light to moderate and is received mostly during the summer.

Vegetation and Animal Species

Flora: The natural vegetation consists of treeless grasslands. These grasses are perennial and belong to the family Gramineae. Unlike tropical Savanna grasses, these are shorter and more nutrient-dense.

Fauna: Major species include antelopes, wild asses, horses, and wolves. In Australia, unique species like kangaroos, emus, and dingoes are dominant.

Human and Economic Significance

These grasslands are often referred to as the 'Granaries of the World'.

Agriculture: The flat, fertile land is ideal for extensive, mechanized wheat cultivation.

Crops: Wheat is the primary crop, while maize is grown in the warmer, wetter sections.

Pastoralism: They serve as vast grazing grounds for livestock (cattle and sheep), supporting large-scale dairy and meat industries.

Distribution and Location

The Taiga is located in the sub-arctic region of the Northern Hemisphere, just south of the Arctic Circle.

Regions: It spans across Alaska (USA), Canada, Scandinavia (Northern Europe), and Siberia (Russia).

Alternative Name: It is widely known as the Boreal Forest Biome.

Climate: Harsh and Cold

Temperature: It has the lowest annual average temperatures among forest biomes, ranging from -5 to 5 degrees Celsius. Winters are long and extremely cold, while summers are very short and only mildly warm.

Precipitation: Rainfall and snowfall are generally low throughout the year.

Plant Species: The Softwood Treasury

The biome is dominated by evergreen coniferous trees, which are the world's richest source of softwood. These trees are cone-shaped to allow snow to slide off easily.

Major Conifers: Pine (White, Red, Scots), Fir (Douglas, Balsam), Spruce, and Larch.

Deciduous Members: Some cold-hardy deciduous trees like Alder, Birch, and Poplar are also found.

Animal Adaptations

Animals are highly adapted to survive extreme cold through thick fur or hibernation.

Fauna: Common animals include Moose, Lynx, Bears, and Siberian Tigers.

Birds: Most bird species are migratory, flying south to escape the freezing, harsh winters.

Human and Economic Interaction

Due to the harsh climate, the human impact is centered on resource extraction rather than settlement.

Economy: Lumbering (logging for timber and paper pulp) is the most significant economic activity.

Agriculture: Very little agriculture exists as the growing season is too short and the soil is often acidic (Podzols).

Indigenous Activities: Groups like the Siberian Samoyeds and Yakuts engage in traditional hunting, trapping, and fishing.

Global Distribution

This biome is primarily found in the mid-latitudes of the Northern Hemisphere.

Regions: Eastern United States and Canada, most of Europe, and parts of East Asia (China and Japan).

Climate: The Land of Four Seasons

The region is exposed to both warm and cold air masses, resulting in a well-defined seasonal cycle.

Seasons: It experiences four distinct seasons: Spring, Summer, Autumn, and Winter.

Temperature: The average yearly temperature is approximately 10°C.

Precipitation: Receives 750 to 1,500 mm of precipitation, which is spread fairly evenly throughout the year.

Plant and Animal Species

Flora: Dominated by tall, broadleaf trees. These trees create a dense canopy during the summer but shed their leaves completely in the winter to conserve water and survive the cold.

Key Tree Species: Beech, Oak, Maple, Mulberry, Willow, and Cherry.

Vegetation Structure: The canopy is continuous in summer, but the lower layers of shrubs and small trees are generally weakly developed compared to tropical forests.

Fauna: Common animals include deer, bears, squirrels, and various bird species, many of which migrate or hibernate during the winter months.

What is Tundra?

The word Tundra comes from the Finnish word for 'deserted land.' It represents regions with the most extreme arctic climates and minimal vegetation.

Classification:

1. Arctic Tundra: Found in the high latitudes of the Northern Hemisphere.

2. Alpine Tundra: Found at high altitudes on mountains across the world (even in tropical areas) where trees cannot grow.

Distribution

Primarily found north of the Arctic Circle in the Northern Hemisphere.

Regions: Greenland's coastal strip, the barren lands of Northern Canada and Alaska, and the Arctic coastal regions of Eurasia (Siberia).

Climate: Extreme Cold

Temperature: Mean annual temperature is very low. The warmest month (June) rarely exceeds 10°C. Mid-winter temperatures can drop to -35°C or lower.

Seasons: Long, dark, and harsh winters with brief, cool summers.

Precipitation: Mostly in the form of snow, which is often redistributed by strong winds during snowstorms.

Plant and Animal Species

Flora: Trees are absent. Vegetation is dwarf and grows during the brief summer. Major species include mosses, lichens, grasses, and low shrubs.

Fauna: Animals are adapted to the cold with thick fur or fat layers. Species include Reindeer (Caribou), Polar Bears, Arctic Foxes, Musk-ox, Arctic Hares, Seals, and Lemmings.

Human Interaction

Life is challenging and mostly confined to coastal areas.

Livelihood: People are often semi-nomadic, traditionally engaging in hunting and fishing.

Tribes: Famous indigenous groups include the Eskimos (Inuit) of North America, Lapps (Sami) of Scandinavia, and Samoyeds of Siberia.

Modern Changes: The discovery of minerals (like oil and gas) has led to new permanent settlements and infrastructure.

Characteristics of Aquatic Systems

Aquatic systems have distinct zones with unique plants, animals, and microorganisms. The variations in life forms are primarily driven by:

Physical Factors: Temperature, sunlight (Photic zone), and Mud/Silt.

Chemical Factors: Salinity, dissolved nutrients, and inorganic contents.

Classification Based on Salinity

1. Freshwater Ecosystem: Contains very low salt content, consistently less than 5 ppt (parts per thousand).
Examples: Rivers, Ponds, Lakes, and Streams.

2. Marine Ecosystem: Contains high salt content, usually above 35 ppt.
Examples: Shallow seas and open oceans.

3. Brackish Water Ecosystem: These are transition zones where freshwater mixes with seawater. Salt content ranges between 5 and 35 ppt.
Examples: Estuaries, Mangrove swamps, and salt marshes.

Classification Based on Water Mobility

1. Lotic Ecosystem (Flowing): In this type, the water moves or flows continuously in one direction.
Examples: Rivers and Streams.

2. Lentic Ecosystem (Still): In this type, the water remains relatively still and does not flow.
Examples: Lakes and Ponds.

Characteristics of a Pond

A pond ecosystem is a type of lentic (still-water) aquatic ecosystem. These can be man-made or natural.

Temporality: Some ponds are temporary (monsoon season only), while larger ones (lakes/tanks) sustain an ecosystem year-round.

Depth: Defined by shallow depth, allowing light to often reach the bottom, which supports specialized aquatic life.

Zones in a Pond Ecosystem

Surface Zone: The topmost layer where light is abundant. It supports floating plants like duckweed.

Photic Zone: The area with sufficient light penetration for photosynthesis. It is rich in algae and submerged plants.

Aphotic Zone: The deep, dark bottom layer where light cannot reach. Organic matter (detritus) accumulates here, and life is limited to decomposers.

Flora of the Pond Ecosystem

The plants in a pond are categorized by how they interact with water and air:

1. Algae: Primary producers and the base of the food chain.

2. Emergent Plants: Roots are underwater, but stems/leaves are exposed to air. Found near edges.
Examples: Cattails, Bulrushes, Reeds.

3. Submerged Plants: Grow completely underwater, usually anchored to the bottom.
Examples: Water milfoil, Pondweeds.

4. Floating Plants: Float on the surface without being anchored.
Examples: Duckweed, Water hyacinth.

5. Riparian Plants: Grow along the damp edges/banks; not necessarily aquatic but part of the pond boundary.
Examples: Willows, Alders.

Zonation in the Marine Ecosystem

The ocean is divided into zones based on depth and light availability:

1. Pelagic Zone (Open Ocean)

This refers to the open water column, not in contact with the shore or sea floor. It is vertically subdivided:

Epipelagic (Sunlit Zone): Surface to approx. 200m. Sunlight is abundant, allowing for photosynthesis.

Mesopelagic (Twilight Zone): 200m to 1,000m. Light is very faint. It holds nearly 90% of global fish biomass.

Bathypelagic (Midnight Zone): 1,000m to 4,000m. It is completely lightless. The only light comes from bioluminescence (light produced by organisms).

Abyssopelagic (Abyssal Zone): 4,000m to 6,000m. Pitch-black, high pressure, and near-freezing. Life here relies on detritus (falling organic waste).

2. Benthic Zone (Sea Floor)

Encompasses the entire sediment surface and the water layer immediately above it, from the shoreline to the deepest trenches.

Marine Organisms Communities

1. Plankton Community

Organisms that drift with water currents. They are the foundation of the marine food web.

Phytoplankton (Algae): Microscopic photosynthetic organisms. They lack roots/stems but produce the majority of the world's oxygen.

Zooplankton: Minute animals (crustaceans, larvae). They are Primary Consumers (eat algae) or Secondary Consumers (eat other zooplankton). They link producers to larger predators.

2. Nekton Community

Active swimmers that can move independently of water currents.

Pelagic Fish: Live in open waters, away from the shore or bottom.

Reef Fish: Associated specifically with coral reef structures.

Demersal Fish: Found living on or near the very bottom of the ocean.