INTERACTION & CORRELATION IN ECOLOGY

INTERACTION & CORRELATION IN ECOLOGY

8.  INTERACTION & CORRELATION IN ECOLOGY

In a natural environment, no organism can survive in isolation. It is must to interact with each other and their environment for every species or organism. Every species is dependent on other species for food, shelter, nutrition or may be many other needs.
There is mainly two type of ecological interactions : 
1.    Positive interaction
2.    Negative Interaction
1.    Positive Interaction: An interaction in which either both participating species or at least one of the participants gets benefits and neither is harmed is called positive interaction.
(A)    Mutualism (+, +) - (i)   Obligate mutualism 
                                      (ii)  Facultative mutualism (protocooperation)
(B)    Commensalism (+, 0)
2.    Negative Interaction : An interaction in which either both participating species or one of the participants gets harmed is called negative interaction.
(C)    Competition (–, –)
(D)    Predation (+, –)
(E)    Parasitism (+, –)
(F)    Ammensalism (–, 0)
POSITIVE INTERACTION
8.1.    Mutualism : This is a positive interaction for both of the species which interact with each other. Mutualism is a symbiotic relationship between members of two different species in which both members of the association are benefitted. This mutualism can be differentiated into obligate and facultative mutualism.
(i)         Obligate mutualism :  A type of mutualism in which the species involved are in close proximity and interdependent with one another in a way that one cannot survive without the other.
eg. (a)    Interaction between fungus and alga forming lichen. In nature, the fungus in lichen provides the water and minerals while the alga uses the minerals and water to make food for the fungus and itself by photosynthesis. When the alga and fungus are separate, both of them cannot grow and reproduce without the symbiotic partner.
(b)    Nitrogen-fixing bacteria (Rhizobium) live in root nodules of legumes, where the bacteria, deriving nutrition from the host plant, fixes atmospheric nitrogen and make it available to the plants.
(c)    In the case of coral reef, coelenterates and algae live in obligate relationship.
(d)    Mycorrhizae are mutualistic relationship between fungi and roots of higher plants.
(e)    Termites and the protozoans/bacterias present in their gut-Termite are only able to eat wood because the protozoans and bacteria present in its gut which helps to digest the cellulose.
(ii)    Facultative mutualism : It is also called protocooperation. In this relationship, both organisms benefit by living in close association but is not obligatory.
eg. (a)    A coelenterate, sea anemone- Adamsia palliate attached to the shells of hermit crab-Eupagurus Prideaux. The sea anemone is carried by the crab to fresh feeding sites and crab in turn is said to be protected from its enemies by sea anemone.
(b)    Relation between bullhorn acacia trees and certain species of Ants. These plants give food and shelter to the ants and ants protect the plants from grasshoppers, caterpillars and even from herbivores sometimes. The acacia is considered as a host in this relationship.
(c)    E.coli and large intestine of Human-Human provide food and place for E.coli. In return, the E. coli produce vitamin K and make it tough for pathogenic bacteria to survive in the intestine.
8.2.    Commensalism : In this interaction, two organism live together and one gets benefit from the relationship but another one gets no gain and no harm.
(A)    Sea anemones and clownfish. The anemones travels upon the fish's body, it gets food by buzzing here and there with fish but fish gets nothing, no loss no benefits.
(B)    Barnacles and whales. Barnacles are non moving creatures. They get attached on the body of whales and move around the sea and get food. But whale have neutral effect.
(C)    Epiphytes → Some tropical orchids use trees or branches of trees for support without harm or benefit to the tree. Similarly, several woody climbers take the support of the trees for exposing their canopy above ground without doing any harm to the tree itself. These relationship are also considered example of commensalism.
(D)    The remora, a sucker fish, lives in close association with sharks or their large fishes. The dorsal fin of the sucker fish is modified to form a sucker, it uses this to attach itself to the shark. The sucker-fish small and does not harm or benefit the shark. 
NEGATIVE INTERACTION
8.3.    Competition: Competition is an interaction between individuals or species in which both of them get harm or loss for their food and needs.
eg. - Cheetahs and lions, since both feed on similar prey. They are negatively impacted by the presence of each other. So they get less food if they live in the same place or one replace the another sometimes. 
The competition involves various types:-
(i)    Intraspecific competition
(ii)    Interspecific Competition
(iii)    Interference competition
(iv)    Exploitation competition
(i)    Intraspecific Competition: When the members of the same species compete with each other for their similar needs. Intraspecific competition often occurs due to limited resources. This type of competition provides a type of control on the population size.
eg.–(A) Individual grass plants on the lawn compete for nitrogen and water from the same resource area.
(B)    Competition among packs eats the good portion of the dead body of their prey.
(ii)    Interspecific competition: It is a competition which includes two different species or communities competition for the same resources.
eg. (a)    Leopards and Lions prey for the same animals and compete with each other
(iii)    Interference Competition (Directly affected): When two organisms interact directly by fighting for scarce resources, this type of competition is termed as interference competition.
eg.– Large insects or aphids defend feeding sites on cottonwood leaves by kicking the smaller aphids from better sites.
(iv)    Exploitation Competition (Indirectly affected): It is a competition between two species or two individuals who have the same limited resources. One of them take the resource faster than the other one and exploits itself.
eg. (a)     Two cheetahs run very fast to prey an animal but one of them run faster than the other and catches the prey first.
(b)    In plants, there are many examples of various species in which one plant takes its nitrogen and other nutrients faster than another plant from the soil.
8.4.    Predation: Predation is an interaction between two individuals where one is a predator (who attacks its food) and another is prey (who is attacked and eaten by a predator). It is a relationship between two organisms in which one species (prey) benefits for growth and reproduction and other species (predator) harmed.
eg.    (a)    Snake and Vulture    
(b)    Plants and Grasshopper
(c)    Frog and Snake
8.5.    Parasitism: It is a biological interaction between two organisms of the same or different species which are independent of each other. In some cases, one gets the benefit and others get harm. In some cases, one gets a neutral effect and another one gets the positive effect and some of the cases involve positive and negative effects respectively for both individuals. In this interaction, the organism which is independent to another is termed as the parasite and the other one who is beneficial for the parasite is termed as host. Two types of parasites are ectoparasite an endoparasite. Ectoparasite lines out of the body of the host and endoparasite live in the body of the host. A parasite that feeds on another parasite is termed epiparasite and relationship referred to as hyperparasitism.
The parasitoid is different from the parasite. The parasitoid is an organism that lives the entire life attached to or within a single host unlike a true parasite however, it ultimately sterilizes or kills and sometimes consumes the host. Parasitoids are large relative to their host's.
eg.     (a)     Red-Billed Oxpecker (Ecto parasite)
(b)    Iaemadium-Cysticercosis (Endoparasite)
(c)    Pea crab and mothers pisum (Ecto parasite)
8.6.    Ammensalism: This is a negative interaction between two species in which one species harmed and the other species neither benefits nor suffers.
eg. (a) Allelopathy: Allelopathy is a biological interaction in which an organism produces one or more biochemicals that influence the germination, growth, survival and reproduction of other organisms. These biochemicals are known as allelochemicals that can have harmful effects on the organisms. Allelochemicals are secondary metabolites produced by plants and other organisms.


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