ECOSYSTEM

The term Ecosystem was proposed by A.G. Tansley in 1935. The ecosystem is defined as
“the system resulting from the integration of all the living and non-living factors of the environment”.

An ecosystem is also defined as a community made up of living organisms and non-living components such as air, water, and mineral soil, all interacting as a system. Thus, an ecosystem has two basic components:

1. Abiotic Components (Non-living components)

It refers to the physical environment or the non-living factors. Examples of the abiotic component comprise the soil, atmosphere, solar radiation, and water. It determines the functions, distribution, structure, behavior, and inter-relationship of organisms in a habitat. The abiotic component is further divided into two:

a. Climatic Factors

Climatic factors include elements namely rain, light, temperature, humidity, wind, and air.

b. Edaphic Factors

These are elements such as minerals, soil, topography, and pH etc.

2. Biotic Components (Living components)

The biotic components of the ecosystems are the living organisms, including animals, plants, and micro-organisms (Fungi and Bacteria). The biotic components are further categorized into three based on their functions in the ecosystem as producers, consumers, and reducers or decomposers.

a. Producers

Producers or autotrophs, are the green plants with chlorophyll, which gives them the ability to use solar energy to manufacture their own food through photosynthesis.

b. Consumers

Consumers or heterotrophs are on the second level. Since they lack chlorophyll, they depend on producers for food.

• Primary Consumers (First-order consumers / Herbivores): Feed on plants or primary producers.
  Examples: Zebras, goats, cattle, rabbits, grasshoppers, deer, etc.

• Secondary Consumers (Second-order consumers / Primary Carnivores): Feed on herbivores.
  Examples: Rats, foxes, etc.

• Tertiary Consumers: Feed on secondary consumers.
  Examples: Wolves, owls, snakes.

• Quaternary Consumers: Feed on primary, secondary, and tertiary consumers and are not eaten by any other animal. These are animals with little or no natural enemies.
  Examples: Tigers, lions, hawks, polar bears, sharks, etc.

c. Reducers or Decomposers

They are also known as saprotrophs, which include fungi and bacteria. They break down the dead remains of plants and animals into simple nutrients through decomposition/biodegradation.

Ecotone

Ecotone is a transitional area between two biomes or diverse ecosystems (where two communities meet & integrate).
Examples:

• Estuary – Transition between freshwater rivers and marine ecosystem.
• Marshland – Between river and riverbank.
• Grassland – Between forests and deserts.
• Lagoons, etc.

Characteristics of Ecotones

• It may be wide or narrow.
• It is a zone of tension, as it has conditions intermediate to the bordering ecosystems.
• It could contain species that are entirely different from those found in the bordering systems.
• Ecotones can be natural or man-made (e.g., agricultural field & forest boundary).

Edge Effect

It refers to changes in population or community structures that occur at the boundary of two habitats. Generally, there is a greater number of species found in ecotones, and this is called the edge effect.

• The species found here are called edge species.

Ecocline

Ecocline is a zone of gradual but continuous change from one ecosystem to another when there is no sharp boundary between the two in terms of species composition.

Ecological Niche

A niche refers to the unique functional role and position of a species in its habitat or ecosystem.

• The concept was developed by Charles Elton.

Types of Niche

• Habitat niche: Where it lives.
• Food niche: What it eats or decomposes & what species it competes with.
• Reproductive niche: How and when it reproduces.
• Physical & chemical niche: Temperature, land shape, land slope, humidity, and other requirements.

Law of Competitive Exclusion

No two species will occupy the same niche and compete for exactly the same resources in the same habitat for very long.

Resource Partitioning

Minimization of competition for resources allows several species to utilize different parts of the same resource and coexist within a single habitat.

Functions of an Ecosystem

Ecosystem functions are natural processes or exchange of energy that take place in various plant and animal communities of different biomes of the world. These functions include:

1. Energy flow
2. Nutrient cycling (Biogeochemical cycles)
3. Ecological succession (Ecosystem development)
4. Biotic Interaction

Biotic Interactions

The biological community of an area or ecosystem is a complex network of interactions.

• Intraspecific interaction: Interaction among individuals of the same species.
• Interspecific interaction: Interaction among individuals of different species in a community.

Types of Biotic Interactions

1. Amensalism

• A negative association where one species inhibits another species without being affected.
• Example: Bread mold Penicillium produces penicillin, which kills bacteria.

2. Predation

• The predator captures, kills, and eats prey.
• Example: Lions hunting deer.

3. Parasitism

• One species (parasite) benefits, while the host is harmed.
• Examples:
  • Dodder plant (parasitic on flowering plants).
  • Loranthus (parasitic plant).

4. Competition

• Both species are harmed as they compete for limited resources (food, water, shelter, mates, space).

5. Commensalism

• One species benefits, the other is neither harmed nor benefited.
• Example: Remora fish attaches to a shark for protection, free ride, and food leftovers.

6. Mutualism

• Both species benefit.
• Example: Hermit crab & sea anemone – The anemone gets transport and food, while the crab gets camouflage and protection.

7. Neutralism

• Two species interact but do not affect each other.
• True neutralism is rare, and usually, interactions are insignificant or negligible.

---

PDF File:

No PDF attached

---

Subject: Environment

← Back