ECOLOGICAL INTERACTIONS

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BIOTIC INTERACTIONS: (ANIMAL ASSOCIATIONS)

There are various types of interactions within a balanced and self sustained ecosystem: 1. Biotic-Biotic interactions 2. Abiotic-Abiotic interactions 3. Biotic-Abiotic interactions

If the members of a particular ecosystem are entirely different from each other, all of them are found to be mutually interdependent for various vital needs.Such interactions are called biotic interactions or population interactions or animal associations. Biotic interactions Mainly 2 types (A) Intra specific interaction: Relationship between members of a same species.

(B) Inter specific interactions : The partners taking part in the relationship will be from different species. 3

INTRA SPECIFIC INTERACTIONS

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a) Cooperative interaction • Positive type of interaction. • Members are getting mutual benefit out of the association. Major types of cooperative interaction between members of same species are

1. 2. 3. 4. 5. 6. 7. 8. 9.

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Mating Group formation Leadership attributes Parental care Territory formation Colonial organizations Division of labour Polymorphism Communication mechanisms etc.

Polymorphism

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Territory

Mating

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(b) Competitive interactions

Intraspecific competition occurs between members of the same species. For example, two male birds of the same species might compete for mates in the same area. This type of competition is a basic factor in natural selection. It leads to the evolution of better adaptations within a species.

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INTER SPECIFIC INTERACTIONS (a) (b)

Positive interactions / Symbiosis Negative interactions /Antagonism

(a)

SYMBIOSIS • Positive type of interaction between animals of different species are commonly called symbiosis

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MUTUALISM Mutually benefitting interactions Eg: Lichens; between algae and fungi

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Eg: Mycorrhiza; between fungi and roots of higher plants.

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COMMENSALISM Interaction in which one species(Commensal) benefits and the other(Host) remains neutral. Eg: Barnacles growing on the back of whales

Eg: Epiphytic orchid on mango tree

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Eg: Cattle Egrets on cattle

(b)Negative interactions / Antagonism The negative type of interactions between animals of different species,are commonly called antagonism(ie,living at the expense of another). By this association one partner is get benefitted out of the association but the other will be completely perished. Major types of antagonistic relationships are the following. 1. 2. 3. 4.

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Antibiosis / Ammensalism Exploitation Predation Parasitism

Antibiosis One animal will kill another present in the same medium by producing certain toxic materials.The toxin used by one organism is called antibiotic. Eg: The fungus Penicillium notatum produces an antibiotic called penicillin, when enters into antibiosis with a number of bacteria.

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Exploitation It is a peculiar type of association,by which one animal make use of the ignorance of the other. Eg:Association between crow and Koel

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Predation One species (Predator) completely eats up the other (Prey). Eg:1. Tiger feeding on Deer

Eg:2. Sparrow feeding on seeds

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Parasitism Interaction in which one species (Parasite) is benefitted by free lodging and meals from the other (Host).

Special parasitic adaptations are: • • • • •

Loss of unnecessary sense organs Presence of adhesive organs or suckers Loss of digestive system Power of anaerobic respiration High reproductive capacity

Types of Parasitism Ectoparasitism: Parasites grows and feeds on the external surfaces of hosts. Eg: Lice on humans : Cuscuta on Plants

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Lice on humans

Cuscuta on plants

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Endoparasitism Parasites grows and feeds within the host body. Eg: Plasmodium in RBC of man : Liver fluke in the bile duct of sheep etc.

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Brood parasitism Parasitic bird lays egg within the nest of the host bird and let the host incubate them. Eg: Cuckoo lays eggs in Crow’s nest.

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COMPETITION Process in which the fitness of one species is significantly lowered in presence of another species.Competition can be intraspecific or interspecific. Eg: Abingdon Tortoise from Galapagos Islands become extinct within a decade after goats where introduced there, due to greater browsing efficiency of goats.

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Competitive Release : A species whose distribution is restricted to a small geographical area,because of the presence of superior species is found to expand its distributional range dramatically when the competing species is experimentally removed. Eg:Balanus that dominates Chathamalus.

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Gause’s Competitive Exclusion Principle:

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Resource Partitioning: This is to avoid competitive Exclusion.If two species compete for the same kind of resources , they could avoid competition by choosing different timing for feeding or different behavioural patterns.

Habitat Partitioning: Habitat partitioning is the best way of coexistence where the different species partition their habitat into microhabitats. Thus, organisms spread themselves in small regions under the ecological niche and start surviving thereby adapting themselves to their microenvironment. A common example of habitat partitioning is anole lizards on the island of Puerto Rico. The differentiation of resources is based on their physical location. The concept of natural selection has made them develop like this by changing their habitats from floor to top of the tree. 11 species of anole lizards live in the same ecological niche and survive successfully by habitat partitioning. They live in their preferred habitat based on food availability, moisture content, sunlight, and height of vegetation.

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Food Partitioning: This is another very important type of resource partitioning where different species change their food habits. For example, the lemur monkeys have food partitioning based on different chemical characteristics of their food. It is completely based on the chemical differentiation in foods made by plants and so different species coexist by having chemically different foods based on priority. Some fruits are raw, less ripen, more ripen or completely ripen and different species like to eat a particular type of fruits out of them. This will help them to stay together without having any competition. Different types of food partitioning are seen where different species prefer different parts of a plant, such as leaves or stems. Thus, their mutual relationship with each other allows them to thrive in the same niche.

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Tree–climbing bird species exploit insect resources in different ways.

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Conclusion

• The species interactions ranges from mutualism to competition among individuals of the same and among other species is instrumental in explaining the concepts of natural balance in an ecosystem. • In a nut shell no species that can survive/ exist in its own without a minimum degree of interaction within itself or with other species. • This implies that this species interaction helps to clarify and justify the issues of interrelationships , association and interdependence among species in the ecosystem .It is capitalized here that species interactions is key to the natural balance in the ecosystem.

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