Lesson 3 of 30

1. Understanding an Ecosystem and its Types

Meaning & Introduction

  1. An Ecosystem is a network of Biotic and Abiotic elements interacting with each other and their physical environment.
  2. This constant interaction between the two results in the transfer of food & energy.
  3. Plants, animals, and other organisms come under Biotic influences. Abiotic factors include inorganic substances such as carbon, oxygen, water; dead organic matter; climatic factors such as humidity, temperature and edaphic factors like soil, topography etc.
  4. The term Ecosystem was coined by Sir Arthur Tansley in 1935.
  5. Ecosystem is a self regulating & self sustaining structural & functional unit of the Biosphere.
  6. The vast network of all interconnected ecosystems constitutes the Biosphere.

IMPORTANT TERMINOLOGIES

A. ECOLOGY

  1. This term was introduced by Sir Hanns Reiter.
  2. It is the scientific study of plants & animals in relation to each other & their environment.

B. BIOME

  1. It is a large geographical area of distinctive vegetation and
    animal groups and is made of many similar ecosystems.

  2. Earth’s whole surface is a series of intertwined habitats. Sometimes, species are linked to a broader biome. Biomes are big parts of land, sea, or atmosphere. For ex, forests, ponds, reefs, and tundra are all kinds of biomes.

  3. For eg, the Sahara Desert biome includes a wide array of ecosystems. This biome is distinguished by its arid climate and hot weather. There are oasis ecosystems within the Sahara that have date palm trees, freshwater, and animals like crocodiles.

    Also, the Sahara has dune ecologies, and the changeable landscape dictated by the wind. Organisms in these ecologies, such as snakes or scorpions, must be able to survive for long periods of time in sand dunes.

    The Sahara even has a marine environment, where cool fogs are produced by the Atlantic Ocean on the coast of Northwest Africa. In this Sahara ecosystem live shrubs and animals that feed on small trees such as goats.

  4. Biomes that sound identical could have separate ecosystems altogether. Throughout Mongolia and China, for example, the Sahara Desert biome is somewhat distinct from the Gobi Desert biome. The Gobi desert is cold, with regular snowfall and freezing temperatures.

    Unlike the Sahara, the Gobi has ecosystems that are not focused on sand but miles of bare rock. The cold, dry environment helps certain grasses to grow. As a result, these Gobi ecosystems have grazing animals like gazelles, and even takhi, an endangered wild horse species.

NOTE- An Ecosystem is much smaller than a Biome

C. ORGANISM, POPULATION & COMMUNITY

Organism– An organism is a fundamental functional unit in ecology because it interacts directly with the environment as well as with other organisms. Ex- Rabbit.

Population– It refers to the organisms of the same species that are in proximity to one another. Ex- a group of Rabbits.

Community– It includes all the population occupying a given area.
Community + Non living Environment = Ecosystem. Ex- a pond with fish and plants.

Types of Ecosystem

There are two types of ecosystem-

a) Natural – These are mainly self regulating. They have less of direct human interference & manipulations. They are further categorised as Terrestrial and Aquatic based on their habitat.

Terrestrial– Forests, Deserts, Grasslands and Aquatic– Ponds, Lake, Rivers, Oceans, Estuaries etc.

b) Artificial- As the name suggests, these ecosystems are man made out of modification due to human activities. Ex- Gardens, Aquariums etc.

Terrestrial or Land based Ecosystems

A. Forest Ecosystem

  1. They consist of trees, bushes, shrubs and are usually found in areas of high rainfall.

  2. Factors like Temperature, Moisture, Nature of soil, Wind and Air currents etc determine the kind of forest vegetation.

  3. There are three major types of forests as per their latitude. They are-

a) Tropical Forests– They witness no Winter. Only two seasons exist that are Rainy & Dry. The biodiversity here mostly consist of Evergreen trees with shallow roots & large green leaves. Orchids, Bromeliads, Vines, Ferns, Mosses etc found here. They host the largest variety of life and animals here are highly adaptable and have stronger defences.

b) Temperate Forests– These experience a moderate climate with a short growing season (Only 3-4 months are frost free). The trees here have broad leaves and shed their leaves annually during dry seasons.

Oak, Hichory, Beech, Maple, Elm, Willow etc are found here. They have a thin canopy of trees that allow sunlight to penetrate and hence small and cold blooded animals such as snakes, turtle etc can survive here. Rabbits, Black bear, Deer etc are also seen. The species here hibernate during the winter months.

c) Boreal or Taiga Forests– Temperatures are very low and rainfall here is in the form of snow. They host cold tolerarant conifers with needle like leaves such as Pine, fir, Spruce. Animals here are mainly birds, rodents and some mammals. Woodpecks, Moose, Fox, Wolf etc are seen here.

B. Grassland Ecosystem

  1. They are characterised by treeless herbaceous plants and are dominated by grass species.

  2. Found on every continent except Antarctica.

  3. Serves as the home for grazing animals. Due to short grasses, the animals here undergo sun stress and strong winds.

  4. They can be grouped under two heads-

a) Tropical Grasslands or Savannas- They lie close to the Equator. Found mostly in Africa and large areas of Australia, South America & India. Climate is the most vital factor in a Savanna. Warm climate, annual rainfall within 6-8 months and followed by a long drought. Occurrence of fires is a common phenomenon during the drought period.

b) Temperate Grasslands- Further from the Equator and experience hot summers coupled with harsh winters. Known by different names in their areas of occurrence, such as – Veldts – South Africa, Pampas – Argentina & Uruguay, Steppes– USSR, Puszia – Hungary, Prairies – Central America. They have hot summers & cold winters with moderate rainfall. Annual Temperature range is very large here.

NOTE– GRASSES GROW FROM THE BASE AND NOT THE TOP. Creeping stems above the ground are called Stolons while those below are called Rhizomes.

C. Desert Ecosystem

  1. They occur in areas with rainfall less than 50 cm a year.
  2. Major deserts of the world are- Sahara; Arabian; Kalahari & Namib of Africa; Atacama of S.America; Mojave, Sonoran & Chihuahuan of N.America, Australian deserts, Thar in India & Pakistan and the Gobi desert of Mongolia.
  3. Soil here is coarse.
  4. Days are very hot and nights too cold.
  5. Plants are succulent and possess thick, waxy leaves to reduce loss of water. Ex- Cactus.
  6. Most animals here are nocturnal.
  7. Deserts can be hot or cold. Ex- Australian desert is hot while Gobi desert is a cold desert.
  8. Largest desert in the world- Antarctica.
  9. Desert plants are- Sagebrush, Creosote etc.
  10. Adaptation is one of the most important characteristic of desert flora & fauna.

Task- Find out about the Rain shadow effect on Gobi desert and its implications.

AQUATIC ECOSYSTEM

A. Freshwater Ecosystem

It is defined as having a less salt concentration. It is further divided into-

Lentic or Standing Water Ecosystems, also better known as Pond Ecosystems such as – Lake, Pond, Marshes, Swamps.

Lotic or Running Water Ecosystems- River, Spring.

1. Pond Ecosystems (Lentic)

  1. Temperature here varies seasonally. and also from the top to the bottom layers.
  2. The middle layer between the top and the low is called the THERMOCLINE. Here, there is a rapid change in the temperature.
  3. The mixing of layers due to winds help circulates the oxygen and also maintains temperature uniformity at times.
  4. Lakes & Ponds are divided into three zones-

a) Littoral Zone- It is the topmost zone near the shore. It is shallow and hence the warmest. It hosts a diverse community of algae, grazing snails, fishes, clams etc. The organisms living here serve as food for other big creatures.

b) Limnetic Zone- This lies below the littoral and near the surface. It is well lighted and is dominated by Phytoplankton and Zooplanktons. One must note that Planktons are an important part of the food chain and without them, there would be no human life!

c) Profundal Zone- This is the bottom most layer and the deep water part of pond ecosystem. It is much denser and colder and they host Heterotrophs who feed on dead organisms.

2. Rivers & Springs ( Lotic)

  1. These can be found everywhere and move in one direction. Their characteristic changes as they travel through distances from their source. Temperature is low at the source than at the mouth of a river. The water at the source is more clear and has high oxygen content than at the mouth where the river tends to be murky on collection of sediments. Due to deficiency of light, there is less flora found here. Catfish, Carp etc are found here since they require less oxygen for survival.

B. Marine Ecosystem

It is divided as Oceans & Coastal Ecosystem. It has a higher salinity.

1. Ocean Ecosystems

  1. This is the largest of all ecosystems.
  2. Depending on light availability, they are classified as – Photic or Euphotic Zone, where the light is ample for photosynthesis and Aphotic Zone is that which is completely devoid of light. Photic zone has green plants and fishes while Aphotic zone is home to bacteria, fungi etc.
  3. The major zones here are-

a) Littoral- It extends between the highest and lowest tea tide. This zone witnesses the highest effect of tides & waves. Algae, Star fish, Crustaceans etc are all found here.

b) Neritic- This is the edge of the Continental Shelf. It is rich in density and diversity due to light penetration and presence of nutrients. Planktons are abundant here and it also hosts whales, sea otters etc.

c) Pelagic- It lies below the Neritic and is an open area.On its surface, some planktons are found alongwith jellyfish and shrimps.

d) Benthic- It is the ocean floor. Low nutrient supply limits production. Host to luminescent organisms ansd sea lilies, sponges etc are found.

2. Coastal Ecosystems

  1. It includes Estuaries and coastal waters and land.
  2. This ecosystem has features of Terrestrial, Aquatic and Marine ecosystem.
  3. It is a Transition zone and a habitat for various organisms.
  4. They are ideal breeding & nesting areas for various birds.
  5. Estuaries are transitional areas between the sea and rivers where the freshwater merges with the ocean.
  6. Sea weeds. mangroves etc found here. Worms, Oysters, Crabs etc are found here.
  7. Level of nutrient is high in estuaries.
  8. The organisms in the estuaries have a special ability to maintain salt & water balance. They are adapted to tidal & wave action also.

Practice questions-

  1. Why is the Ecosystem significant for living organisms? Comment.
  2. Discuss in details about the various types of ecosystem and the biodiversity they host.