This document summarizes different types of inter-relationships between biotic and abiotic components in an ecosystem. It defines amensalism as a relationship where one species inhibits or destroys the other species with no effect on itself. Examples of amensalism provided include penicillium secreting penicillin that kills bacteria but is not affected, and allelopathy where some plant species release chemicals that inhibit the growth of other plants and microbes. The document also gives examples of black walnut trees and eucalyptus releasing chemicals through their leaves and roots that suppress the growth of surrounding vegetation.

1. Sanduni K. Madarasinghe
University of Ruhuna

2. “Study of the inter-relationship between biotic and abiotic
component as well as the relationships among the individuals of the
biotic component”
Ecology
Biotic factor Abiotc factor Inter-relationships
Competition
Neutralism
Commensalism
Amensalism
Mutualism
Predation,
Parasitism, Herbivory
Matter
Energy
Plants and animals
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3. Types of Interactions
Type Effect on
Species 1
Effect on
Species 2
Amensalism - 0
Neutralism 0 0
Commensalism + 0
Competition - -
Mutualism + +
Predation, Parasitism,
Herbivory
- +
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4. Amensalism
• Any relationship between organisms of different species in
which one organism is inhibited or destroyed while the
other organism remains unaffected
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5. Example 1:
• Penicillium secrete penicillin, a chemical that kills bacteria
Penicillium sp. Penicillium sp. cultured with a
bacteria (Staphylococcus aureus)
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Penicillium
Staphylococcus

6. Example 2:
• Allelopathy involves the production and release of chemical
substances by one species that influence the growth,
survival, and reproduction of other organisms
• These allelochemicals seem to have no direct use in
metabolism
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7. Examples for Allelopathy:
• Black Walnut (Juglans nigra) trees excrete juglone, that
inhibit the growth of nearby trees, shrubs, grasses, and herbs
• The leaf litter and root exudates of some Eucalyptus species
are allelopathic for certain soil microbes and plant species
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8. 8
Casuarina equisetifolia litter completely suppresses germination of understory plants

9. References
• A text book of Plant Ecology (R.S. Ambasht)
• A text book of Plant Ecology (R.S. Shukla)
• http://www.allelopathyjournal.org
• http://csip.cornell.edu/Projects/CEIRP/AR/Allelopathy.htm
• Daizy R. Batish, Harminder Pal Singh (1998) Role of Allelopathy
in Regulating the Understorey Vegetation of Casuarina
equisetifolia. Environmental Forest Science, Vol.54 (Forestry
Sciences) pp 317-323
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