POPULATION INTERACTION
Members of biotic community depends upon one another for
food, reproduction, dispersal & production, the phenomenon is called species
interdependence interaction.
Types of interactions that occur amongst different members
of biotic community are–positive and negative.
In positive or beneficial interaction, members of one or both the interacting species are
benefitted but neither is harmed.
In negative interaction, one or both the interacting species is harmed.
POSITIVE OR BENEFICIAL INTERACTION
It is a widespread phenomenon. It includes mutualism,
commensalism, proto-cooperation, scavenging etc.
Mutualism (+/+) or Symbiosis : (coevolution) :
·
It is a positive
interspecific interaction in which members of two different species completely
depend on each other for growth and survival.
·
Physical contact is present
in between both the interacting species.
·
It is an obligatory
relationship.
Examples –
Mutualism between animal and animal-
E.g., Termites and aflagellates
(Trichonympha)
Mutualism between plant and animals
E.g., (a) Zoochlorella and Hydra.
(b) Yucca plant flowers and Pronuba
insects -Pollination of Yucca plant by pronuba (Female yucca moth)
Mutualism between plant and bacteria
E.g., legume plant and Rhizobium.
Mutualism between algae and higher plant
E.g., Nostoc, Anabaena and Anthoceros
plant.
Mutualism between algae and fungi
E.g., Lichens.
Mutualism between fungi and higher plants
E.g., Mycorrhizal association
Commensalism (+/0)
It is an association between members of two species in which
one is benefited while the other is almost unaffected.
Examples –
Lianas :Lianas are woody plants. Their roots are present in soil but
their stem uses other plants or objects for support to get better light. They
are found in dense forest. No nutritional relationship is present. Lianas are
the speciality of tropical rainforest. E.g., Bauhinia, Tinospora
E.g., Orchids, hanging mosses.
Epizones :Those animals which depend on plants or other animals. E.g.,
·
Sucker fish
(Echeneis) – Shark
·
Pilot fish – Shark
·
E. coli bacteria –
Intestine of man
·
Clown fish –
Sea anemone
·
Barnacles –
Whale
·
Cattle ergot birds –
Cattle
Proto-cooperation (+/+)
It is an association in which both the organisms are
benefited but can live separately.
It is a facultative or optional or
occasional association. It is also called as non-obligatory
relationship.
Examples –
·
Hermit crab – Sea
anemone
·
Tick bird (Red-billed
or yellow billed) – Rhinoceros
·
Crocodile – Bird
·
Plants with both self
and cross fertilization.
Scavenging is an association in which one partner (called scavenger or
saprobiont), eats the dead bodies of other animals, which have died naturally
or have been killed by another animal. E.g., Jackal, Vulture, Ant, Crow.
Helotism is an association
between two organisms, when one behaves as a master and another as a slave.
E.g., Lichen.
NEGATIVE INTERACTION
(ANTAGONISM)/DETRIMENTAL
Types of negative interaction are exploitation, amensalism and competition.
Exploitation:
One species harms the other by making direct or indirect use
of it for support, shelter or food.
It is of two types : parasitism and predation.
1.
Parasitism (+/–) :
This association involves individuals of two species of different
sizes in which the smaller (parasite) is benefitted and the larger (host) is
harmed. The parasite gets nourishment and shelter from host but does not kill
the host.
Types of parasite :
1.
Ectoparasite :Lives on the body of the host. E.g.,–
2.
Ectozooparasite :leech on cattle, ticks on dogs, sandfly on man.
3.
Ectophytoparasite : aphids, lac insects, red cotton bug
Endoparasites : Live in the body of the host. E.g., Tapeworm, Taenia, Ascaris,
Entamoeba → Live in intestine of man.
Plasmodium → Lives in
R.B.C. of human.
1. Hyperparasitism : A parasite living on another parasite.
E.g., Plasmodium on female Anopheles mosquito, bacteriophages
on bacteria.
Brood parasitism : Parasitism in which the parasitic bird (cuckoo) lays its
eggs in the nest of its host (crow) and lets the host incubate them, this
relation is known as brood parasitism.
Holoparasite : Parasite which are totally dependent upon the host for
their requirement
E.g., Rafflesia (Total root parasite).
Cuscuta (Total stem parasite).
Hemiparasite : Parasite which partially depends on the host.
E.g., Viscum – on oak and Loranthus –
on mango. Both are partial stem parasites. Santalum is a partial root parasite.
Note :Arceuthobium is the smallest
parasite.
E.g.,
Insectivores fungi :Dactylella, Dactylaria, Arthrobotrys
Carnivores animals :Lion, snake
Insectivores plants :Drosera, Utricularia, Nepenthes
Amensalism (–/0)
In this interaction, one species is inhibited by the toxic
secretion of another species. Inhibitor species is neither benefited nor
harmed.
Type of amensalismare antibiosis and allelopathy.
Antibiosis – secretion of antibiotics E.g.,
Penicillium fungi secretes penicillin which inhibits the
growth of Staphylococcus bacteria.
Chlorella algae secretes bacteriocytes which not only kill
but also inhibit growth of the bacteria.
Microcystis (BGA) secretes hydroxyl amine which causes the
death of fishes.
Allelopathy is the secretion of toxic chemicals and the plant is always harmed
in this case. E.g.,
Parthenium : Trans Cinnamic acid is secreted by Parthenium
which inhibits the growth of some plants like Cassia tora and Vincaregia. This
phenomenon is known as allelopathy.
Sunflower, barley, sorghum, Occimum also show allelopathy.
Silver oak shows autopathy - It destroys its own seed.
Competition
Interaction between two species, where both suffer adverse
effects is known as competition.
It is of 2 types – interspecific and intraspecific.
Interspecific competition occurs between two individuals of two different species occurring
in the same habitat.
Intraspecific competition occurs between individuals of the same species for mating, food
etc.
