- There are various species of biotic community living together in the same environment.
- They interact with each other for various things like food, shelter and habits.
- They show positive as well as negative interactions. Some of them are as follows:
1. Positive interactions There are various types of positive interactions which are as follows:
a) Mutualism (symbiosis)
- Two species are in close association with each other and are also benefitted from each other.
- In this association, a close and permanent contact occurs.
- In some cases, they show obligatory contact i.e. essential for survival of both.
- For examples:
i) lichen-association of algae and fungi in which algal partner produces food for both and fungal partner helps in fixation, protection and absorption.
ii) association of nitrogen fixing bacteria in the root nodules of leguminous plants. Plant produces food and Rhizobium fixes nitrates.
iii) relationship between oxpeckers and the rhinos or zebras.
iv) the bee and the flower.
v) the spider crab and the algae.
vi) the bacteria and the human.
- Two organisms are associated, one get benefitted while other is neither benefitted nor harmed.
- For examples:
i) association of sea anemone (Adamsia) and hermit crab (Eupagurus). Here, hermit crab gets unharmed while sea anemone is carried from one place to another for food as it gets attached to the body of hermit crab.
ii) epiphytes (orchids): They are also plants which grow on other plants without harming them.
iii) relationship between cattle egrets and cattle.
iv) spider building web in a tree.
- It is less extreme sort of interaction than mutualism.
- Both the animals get benefitted.
- However, it is not obligatory i.e not essential for both species.
- For examples:
i) relationship between snakes and water birds. Here, both of them are benefitted but there is no obligatory condition.
ii) spur- winged plover and crocodile.
iii) birds and bovines.
- A group of animals of same species live together in a group.
- They are dependent upon each other.
- For examples: corals and sponges are physically connected and function as a single unit.
e) Social organization
- There is division of labour seen among the individuals in the population.
- There are various examples related to this interaction.
- Such organization is exhibited by bees, ants, wasps, termites among insects, certain fishes and birds.
- For examples: honey bee shows excellent division of labour. Its colony consists of functional female or queen, males or drones, sterile females and workers. They work in coordinate manner for welfare of colony.
- Tendency among animals to concentrate in large numbers by their own movements is called aggregation.
- It has survival significance.
- For examples:
i) thousands of lady beetles hibernate under leaves at the forest edge.
ii) millions of bats roost together in a large caves.
iii) migratory locust
iv) birds usually migrate in groups.
There are various types of negative interactions which are as follows:
- It is a direct interaction of two species.
- One organism kills another organisms for food.
- The species that capture, kills and eats up is called predator or enemy and that which is caught is called prey.
- Generally, predator is larger and stronger than its prey.
- For examples: tiger feeds on deer, snake feeds on frogs, etc.
- A parasite is the organism which lives on another organisms.
- They get their nourishment from the host body.
- It is one sided relationship in which parasite gets benefitted and the host is always harmed.
- A large number of organisms grow as parasite on other organisms.
- They absorb their food causing diseases and serious damage to host.
- Several species of fungi, bacteria, arthropods and viruses are well known parasites.
- They live as parasite and cause diseases to plants, animals and man.
- Two individuals or species compete with each other for limited resource.
- They have common nutrients, space, sunlight, food, etc.
- Competition is maximum among same species of organisms as they have similar requirements.
- It may also occur among the individuals of different species.
- For examples: in crop fields, weeds also grow which compete with the crops and if not removed reduces the quantity of crops. Similarly, animals like tiger and lion compete for their prey.
- The term “antibiosis” refers to the complete or partial inhibition or death of one organism by another.
- There is production of some substance or environmental conditions as a result of metabolic pathway.
- None of them derives any benefit.
- This phenomenon is well known among microbial world.
- For examples: production of antibiotics is well known among microorganism, which inhibits the growth of other microorganism.