Ecological Interactions - TNPSC - Environmental Scientist

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Ecological Interactions: Notes with Examples

Organisms in ecosystems constantly interact with each other, influencing survival, reproduction, and distribution. These interactions are central to the structure and dynamics of ecological communities.


 1. Symbiosis

Definition:

Symbiosis refers to a close, long-term biological interaction between two different species. It can be beneficial, neutral, or harmful to the involved organisms.

Types of Symbiotic Relationships:

  • Mutualism
  • Commensalism
  • Parasitism

 2. Mutualism (++)

Definition:

A relationship in which both species benefit.

Example:

  • Bees and flowering plants: Bees get nectar; plants get pollinated.
  • Lichen: A mutualistic relationship between algae and fungi. Algae photosynthesize; fungi provide structure and moisture.
  • Rhizobium bacteria and leguminous plants: Bacteria fix nitrogen; plants provide shelter and nutrients.

Note:

Mutualism can be obligate (essential for survival) or facultative (optional but beneficial).

 

3. Commensalism (+0)

Definition:

One species benefits, and the other is neither helped nor harmed.

Example:

  • Barnacles on whales: Barnacles get transportation and access to food; whales are unaffected.
  • Epiphytic plants (like orchids) on trees: The epiphyte gets support; the tree remains unaffected.
  • Cattle egrets and grazing animals: Egrets eat insects stirred up by cattle.

 4. Proto-cooperation (++) (also called Facultative Mutualism)

Definition:

Both species benefit, but they can survive without each other.

Example:

  • Clownfish and sea anemones: Clownfish get protection; anemones get food scraps.
  • Cleaner fish (like wrasses) and large fish: Cleaner fish remove parasites; large fish get cleaned.

Difference from Mutualism:

In proto-cooperation, the relationship is not obligatory.

5. Amensalism (-0)

Definition:

One species is harmed, and the other is unaffected.

Example:

  • Penicillium fungus releases penicillin, which kills nearby bacteria, but the fungus is unaffected.
  • Black walnut tree (Juglans nigra): Its roots release chemicals that inhibit the growth of nearby plants.

Note:

Amensalism usually occurs through chemical inhibition or accidental destruction.

6. Predation (+−)

Definition:

One organism (predator) kills and eats another organism (prey).

Example:

  • Tiger and deer
  • Frog and insect
  • Eagle and snake

Features:

  • Predators are usually larger than prey.
  • Predation helps control population balance and maintains biodiversity.

 7. Parasitism (+−)

Definition:

One organism (parasite) benefits at the expense of the other (host), usually without immediate death.

Example:

  • Tapeworm in human intestines
  • Malarial parasite (Plasmodium) in humans via mosquito bite
  • Ticks or lice feeding on animals' blood

Types of Parasites:

  • Ectoparasites: Live outside the host (e.g., lice, ticks)
  • Endoparasites: Live inside the host (e.g., tapeworm, Plasmodium)

 

 

 

Summary Table of Ecological Interactions

Interaction Type

Effect on Species A

Effect on Species B

Example

Mutualism

+

+

Bees and flowers

Commensalism

+

0

Barnacles on whales

Proto-cooperation

+

+

Clownfish and sea anemone

Amensalism

-

0

Penicillium fungus and bacteria

Predation

+

-

Tiger and deer

Parasitism

+

-

Tapeworm in human intestine

Conclusion

Ecological interactions are key to understanding ecosystem stability, population control, and evolution. These relationships show how all life is interlinked, and even small changes in one species can impact the entire ecological network.

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Other Topics

Components of Environment - TNPSC - Env Scientist

 Atmosphere

Segments of Environment

Lithosphere

Hydrosphere

 








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