Symbiotic Relationships: Types, Forms, and Related Terms
Dr. Mukul K Sinha
1. Symbiosis:
A close and prolonged association among two (or more) different organisms of different species that may, but not necessarily, benefit or harm each member.
(‘sym’ means ‘with’, and ‘biosis’ means ‘living’)
–> ‘symbiosis’ means ‘living together’.
Each organism independently is called ‘Symbiont’.
1.1 Types of Physical Associations between Symbionts:
– Ectosymbiosis – one organism (symbiont) lives ‘above’
or on surface of another symbiont,
– Endosymbiosis – one organism lives ‘inside’ another.
1.2 Five Forms Relationship between Symbionts:
Used: ‘ + ’ for Advantage to a symbiont,
‘ – ’ for Disadvantage or Harm to a symbiont, and
‘ 0 ’ for No Effect to a symbiont.
Mutualism: ‘+ +’
Commensalism: ‘+ 0’
Parasitism ‘+ -’
Amensalism ‘ – 0’
Synnecrosis ‘ – -’
2. Relationships between Symbionts
2.1. Mutualism ‘+ +’:
Benefit to both symbionts (increase in their fitness),
– Obligate – both depend on each other, for survival of at least one,
– Facultative – both depend on each other, but not for survival,
2.1.1 Types of Mutualism
(i) Obligate – Obligate: Obligate for both the symbionts, or
(ii) Obligate – Facultative: Obligate for one symbiont, and Facultative for another, or
(iii) Facultative – Facultative: Facultative for both the symbionts.
Trophobiosis – A special type of Obligate Mutualistic Symbiosis where one organism protects other in return for some kind of food,
2.1.2 Types of Exchanges in Mutualistic Relationships:
(i) Resource – Resource
Trading / barter of one type of resource with one symbiont
for another type of resource which other symbiont has.
(e.g., Animal husbandry by man for meat / eggs/ milk/..)
(ii) Service – Resource
By provision of resource by one symbioant, get service from other symbioant.
(e.g., Dog for protection / hunting, Horse for transport, Draft Animals)
(iii) Service – Service
Exchange service one kind offered one symbioant by receiving service of another kind by another symbioant.
(e.g., Tiger Reserve for better environment).
2.2. Commensalism ‘+ 0’:
Benefit to one symbiont without affecting the other symbiont,
(commensal – ‘sharing food’ in English, and ‘sharing table’ in Latin)
Types of Commensalism among species
Phorsey – for transportation of one without much affecting the other,
Inquilinism – for housing,
Metabiosis – using something (after their death) that other has created.
2. 3. Parasitism ‘+ -’:
Benefit to one symbiont at the cost of the other.
One symbiont benefits while the other symbiont gets harmed.
Types of Parasitism
(i) Biotrophic – Parasite relies on host’s survival,
(ii) Necrotrophic – Parasite kills its host in long run.
Around half of all the animals have a parasitic phase in their life cycle,
and so is the case of plants and fungi.
– Endoparasite lives within ‘host’
– Ectoparasite lives on the surface of the host.
2.4. Amensalism ‘- 0’:
Detrimental to one symbiont without affecting the other,
Not common – but one affected adversely (inhibited) without other being aware.
For example, sapling under a large tree – being deprived of sunlight / enough water,
or soil nutrients (drawn by the large roots of the large tree).
2.5. Synnecrosis ‘ – –’:
Detrimental to both the symbionts
Mutual destructive relationship
– reduced fitness of both
– inter-specific competition.
3. Other Related Terms
3.1. Symbiogenesis
Not to be achieved by ‘combat’ but by ‘networking’.
Lynn Margulis – Darwin’s theory of evolution based on competition is incomplete. Evolution is mainly based on cooperation, interaction, and mutual dependence of organisms.
3.2. Co-evolution
Change in a biological object triggered by change in another object.
Inter-dependant co-evolution of many plants / insects / birds /..
in contrast to the concept of predation, or competition.
3.2.1 Technological Co-evolution
– Hardware and software engineering in computer science,
– Operating Systems / programming languages and computer applications.
End.
Nov. 06, 2010
Hello Sir,
This the second comment on your post…