- A natural ecosystem is an assemblage of plants and animals which functions as a unit and is capable of maintaining its identity.
- There are two main categories of ecosystems: 1) Terrestrial ecosystem or Biomes and 2) Aquatic ecosystem
- The terrestrial part of the biosphere is divisible into enormous regions called biomes.
- No two biomes are alike. They are characterized, by distinct climate (precipitation and temperature mainly), vegetation, animal life and general soil type.
- The climate determines the boundaries of a biome and abundance of plants and animals found in each one of them.
- Arctic and Alpine Tundra Biome
- Taiga or Boreal Biome (Evergreen Coniferous forests)
- Temperate Deciduous Biome (North Western Europe – British Type Climate)
- Temperate Rainforest Biome
- Sub-Tropical Deciduous Biome in Eastern China, South Eastern USA
- Temperate Deciduous Biome (Mediterranean Climate)
- Tropical Deciduous Biome (Monsoon Climate)
- Savanna or Tropical Wet and Dry Biome
- Tropical Rain Forest Biome
- Steppe or Temperate Grassland Biome
- Savanna or Tropical Wet and Dry Biome (Tropical Shrublands and Grasslands)
- Tropical and Mid Latitude Desert Biome
For detailed explanation ad maps, you must go through Geography > Climatology > Climatic Regions.
- There are two types of tundra – arctic and alpine.
- Alpine tundra occurs at high mountains above the tree line. E.g. High ranges of the Himalayas, Andes, Alps etc.
- There are no trees in the tundra (due to permafrost).
- The lowest form of vegetation like mosses, lichens are sparsely found on bare rocks.
- Coastal lowlands reindeer moss which provides the only pasturage for reindeers.
- In the summer, birds migrate north to prey on the numerous insects which emerge when the snow thaws.
- Insects have short life cycles which are completed during the favourable period of the year.
- Animals like the reindeer, arctic fox, wolves, musk-ox, polar bear, lemming, arctic hare, arctic willow live in tundra region.
- Reptiles and amphibians are almost absent.
- Most of the animals have long life, e.g. arctic willow has a life span of 150 to 300 years.
- They are protected from chillness by the presence of thick cuticle and epidermal hair or fur.
- Mammals have a large body size and small tail and ear to avoid the loss of heat from the surface.
Taiga or Boreal Biome
- Boreal forest soils are characterized by thin podzols and are rather poor. This is because:
- The weathering of rocks proceeds slowly in cold environments
- the litter derived from conifer needle (leaf) is decomposed very slowly and is not rich in nutrients (humus content is low).
- conifers do not shed their leaves frequently.
- The predominant vegetation is an evergreen coniferous forest with species such as spruce, fir and pine.
- The conifers require little moisture are best suited to this type of sub-Arctic climate.
- The productivity of boreal forest is lower than those of any other forest ecosystem.
- Animals found in this region include Siberian tiger, wolverine, lynx, wolf, bear, red fox, squirrel, and amphibians like Hyla, Rana, etc.
Temperate Deciduous Biome (North-Western Europe – British Type Climate)
- Soils of temperate forests are podzolic and fairly deep.
- The natural vegetation of this climatic type is deciduous.
- The trees shed their leaves in the cold season.
- This is an adaptation for protecting themselves against the winter snow and frost.
- Shedding begins in autumn, the ‘fall’ season. Growth begins in spring.
- Some of the common species include oak, elm, ash, birch, beech, and poplar.
Temperate Rainforest Biome
- This is a small biome in terms of area covered. The main stretch of this habitat is along the northwestern coast of North America from northern California through southern Alaska.
- There are also small areas in southern Chile, New Zealand, Australia and a few other places around the world.
- Big coniferous trees dominate this habitat, including Douglas fir, Western red cedar, Mountain hemlock, Western hemlock, Sitka spruce and Lodgepole pine.
- In addition to the trees, mosses and lichens are very common, often growing as epiphytes.
- Grizzly bears are the common mammals found in Alaska.
Sub-Tropical Deciduous Biome in Eastern China, South Eastern USA
- Supports luxuriant vegetation.
- The lowlands carry both evergreen broad-leaved forests and deciduous trees (hardwood).
- On the highlands, various species of conifers such as pines and cypresses are important.
- Perennial plant growth is not checked by either a dry season or a cold season.
Steppe or Temperate Grassland Biome
- They are practically treeless, and the grasses are much shorter.
- Grasses are fresh and nutritious.
- Poleward, an increase in precipitation gives rise to a transitional zone of wooded steppes where some conifers gradually appear.
- Do not have much animal diversity.
Temperate Deciduous Biome (Mediterranean Climate)
- Trees with small broad leaves are widely spaced and never very tall.
- Regions with adequate rainfall are inhabited by low, broad-leafed evergreen trees (mostly evergreen oaks).
- Fire is an important hazardous factor in this ecosystem, and the adaptation of the plants enable them to regenerate quickly after being burnt.
- Plants are in a continuous struggle against heat, dry air, excessive evaporation and prolonged droughts.
- They are, in short xerophytic (drought tolerant).
Tropical Deciduous Biome (Monsoon Climate)
- Tropical Monsoon Forests are also known as a drought-deciduous forest; dry forest; dry-deciduous forest; tropical deciduous forest.
- Teak, neem, bamboos, sal, shisham, sandalwood, khair, mulberry are some of the important species.
Savanna or Tropical Wet and Dry Biome
- The savanna landscape is typified by tall grass and short trees.
- The trees are deciduous, shedding their leaves in the cool, dry season to prevent excessive loss of water through transpiration, e.g. acacias.
- Trees usually have broad trunks, with water-storing devices to survive through the prolonged drought.
- Many trees are umbrella shaped, exposing only a narrow edge to the strong winds.
- Savanna biome is rich in mammal, bird and reptile diversity.
Tropical Rain Forest Biome
- High temperature and abundant rainfall support a luxuriant tropical rain forest.
- The equatorial vegetation comprises a multitude of evergreen trees, e.g. mahogany, ebony, dyewoods etc.
- In the coastal areas and brackish swamps, mangrove forests thrive.
- All plants struggle upwards (most epiphytes) for sunlight resulting in a peculiar layer arrangement (canopy).
- Epiphyte (commensalism – epiphyte benefits without troubling the host): An epiphyte is a plant that grows harmlessly upon another plant (such as a tree) and derives its moisture and nutrients from the air, rain, and sometimes from debris accumulating around it.
Q. Which of the following is/are unique characteristic/characteristics of equatorial forests?
- Presence of tall, closely set trees with crowns forming a continuous canopy
- Coexistence of a large number of species
- Presence of numerous varieties of epiphytes
Select the correct answer using the code given below:
- 1 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Answer: d) All
- The predominant vegetation of both hot and mid-latitude deserts is xerophytic or drought-resistant.
- This includes the cacti, thorny bushes, long-rooted wiry grasses and scattered dwarf acacias.
- Most desert shrubs have long roots and are well spaced out to gather moisture, and search for ground water.
- Plants have few or no leaves, and the foliage is either waxy, leathery, hairy or needle-shaped to reduce the loss of water through transpiration.
- The seeds of many species of grasses and herbs have thick, tough skins to protect them while they lie dormant.
- Aquatic ecosystems refer to plant and animal communities occurring in water bodies.
- Aquatic ecosystems are classified into two subgroups: 1) Freshwater ecosystems, such as rivers, lakes and ponds; 2) Marine ecosystems, such as oceans, estuary and mangroves.
- Aquatic ecosystems are classified on the basis of salinity into the following types:
- Freshwater ecosystems: water on land which is continuously cycling and has low salt content (always less than 5 ppt) is known as fresh water.
- There are two types of freshwater ecosystems: 1) Static or still water (Lentic) ecosystems, e.g. pond, lake, bogs and swamps. 2) Running water (Lotic) ecosystems, e.g. springs, mountain brooks, streams and rivers.
- Marine ecosystems: the water bodies containing salt concentration equal to or above that of seawater (i.e., 35 ppt or above). E.g. shallow seas and open ocean.
- Brackish water ecosystems: these water bodies have salt content in between 5 to 35 ppt. e.g. estuaries, salt marshes, mangrove swamps and forests.
- The aquatic organisms are classified on the basis of their zone of occurrence.
- Neuston: These organisms live at the air-water interface, e.g. floating plants.
- Periphyton: These are organisms which remain attached to stems and leaves of rooted plants or substances emerging above the bottom mud such as sessile algae.
- Plankton: Microscopic floating organisms such as algae, diatoms, protozoans and larval forms are called plankton. This group includes both microscopic plants like algae (phytoplankton) and animals like crustaceans and protozoans (zooplankton).
- The locomotory power of the planktons is limited so that their distribution is controlled, largely, by currents in the aquatic ecosystems.
- Nekton: This group contains powerful swimmers that can overcome the water currents.
- Benthos: The benthic organisms are those found living at the bottom of the water mass.
Factors Limiting the Productivity of Aquatic Habitats
- Sunlight and oxygen are the most important limiting factors of the aquatic ecosystems.
- Sunlight penetration rapidly diminishes as it passes down the column of water.
- The depth to which light penetrates a lake determines the extent of plant distribution.
- Suspended particulate matters such as clay, silt, phytoplankton, etc. make the water turbid.
- Turbidity limits the extent of light penetration and photosynthetic activity in a significant way.
- Based on light penetration and plant distribution they are classified as photic and aphotic zones.
- Photic (or “euphotic”) zone is the portion that extends from the lake surface down to where the light level is 1% of that at the surface. The depth of this zone depends on the transparency of water.
- Photosynthetic activity is confined to the photic zone.
- Both photosynthesis and respiration activity takes place.
- The lower layers of the aquatic ecosystems, where light penetration and plant growth are restricted forms the aphotic zone (profundal zone). Only respiration activity takes place in this zone.
- The aphotic zone extends from the end of the photic zones to bottom of the lake.
- In freshwater the average concentration of dissolved oxygen is 10 parts per million by weight.
- This is 150 times lower than the concentration of oxygen in an equivalent volume of air.
- Oxygen enters the aquatic ecosystem through the air-water interface and by the photosynthetic activities of aquatic plants.
- Dissolved oxygen escapes the water body through the air-water interface and respiration of organisms (fish, decomposers, zooplankton, etc.).
- The amount of dissolved oxygen retained in water is also influenced by temperature.
- Oxygen is less soluble in warm water. Warm water also enhances decomposer activity. Therefore, increasing the temperature of a water body increases the rate at which oxygen is depleted from the water.
- When the dissolved oxygen level falls below 3-5 ppm, many aquatic organisms are likely to die.
- An ice layer on the top of a water body can effectively cut off light. Photosynthesis stops but respiration continues in such water body.
- If the water body is shallow, the oxygen gets depleted, and the fish die. This condition is known as winterkill.
- Since water temperatures are less subject to change, the aquatic organisms have narrow temperature tolerance limit.
- As a result, even small changes in water temperature are a great threat to the survival of aquatic organisms when compared to the changes in air temperatures in the terrestrial organisms.