Biotic interactions, also known as biological interactions, are the relationships between living organisms within ecosystems. These interactions can be classified based on the effects they have on the participating organisms, ranging from beneficial to detrimental. Biotic interactions play a crucial role in shaping ecological communities, influencing population dynamics, species distribution, and ecosystem functioning. Biotic interactions can be categorized into positive and negative interactions based on the effects they have on the participating organisms. Positive interactions benefit one or both of the interacting species, while negative interactions harm one or more of the organisms involved.

POSITIVE BIOTIC INTERACTIONS

1. MUTUALISM

Mutualism also called as symbiosis, is a positive interaction where both participating species benefit from the association. Each species provides resources, services, or protection that enhance the fitness and survival of the other.

Examples include pollination by insects and plants, nitrogen-fixing bacteria and leguminous plants, and cleaner fish and their hosts.

Lichens: lichens are symbiotic association between algae and fungi. the body of lichen composed of fungal matrix in which the algal cells are embedded. The fungi provide protection to algal components and also provide moisture and nutrients to them. The algal components in turn will supply carbohydrates for fungus.

Mycorrhizae: They are the symbiotic association between fungi and the roots of some trees. Fungal components help in the absorption of water and minerals by the plants. The plant in turn supplies foot to fungal components.

2. COMMENSALISM

Commensalism is a positive interaction where one species benefits, and the other is unaffected. The commensal species exploits resources or habitat modifications created by the other species without providing any benefit or harm in return.

Examples include epiphytic plants growing on trees, barnacles attaching to whales, and birds nesting in tree hollows.

Climbers and Lianas such as Bauhinia, Tinospora etc. which are rooted in the soil but climb over large trees. These climbers use other trees as support to get enough sunlight, more than that, the supporting plants do not have any positive or negative effect.

3. PROTO- COOPERATION

In proto-cooperation, organisms engage in interactions that provide some benefit to one or both parties involved. The benefits may include access to resources, increased fitness, reduced predation risk, or enhanced reproductive success. Unlike mutualism, proto-cooperation does not involve a high level of specialization or dependency between the interacting species. Proto-cooperation interactions may vary in intensity and duration, and they can be context-dependent, influenced by environmental conditions, resource availability, and the behavior of the interacting organisms.

Examples

Seed dispersal by animals: Some plants produce fruits with nutritious pulp or seeds that are dispersed by animals. While the plants benefit from the dispersal of their seeds to new locations, the animals may obtain food from the fruits. This interaction provides a benefit to both the plant and the animal, but it does not involve the level of coevolution or mutual dependency seen in more specialized seed dispersal mutualisms.

NEGATIVE BIOTIC INTERACTIONS

1. COMPETITION

Competition is a negative interaction where individuals or species vie for limited resources such as food, water, shelter, or territory. It can occur within or between species. Competition can lead to resource partitioning, niche differentiation, and competitive exclusion, where one species outcompetes another, leading to local extinction or niche restriction. The competition in the ecosystem may be of two types:

a. Intraspecific Competition(within population)

b. Interspecific Competition(between population)

2. PREDATION

Predation is a negative interaction where one organism (predator) captures, kills, and consumes another organism (prey) for food. Predation influences population dynamics, prey behavior, and predator-prey coevolution.

Examples include carnivores hunting herbivores, herbivores consuming plants, and parasitoids attacking insect hosts.

3. PARASITISM

Parasitism is a negative interaction where one organism (parasite) benefits at the expense of another organism (host), which is harmed but usually not killed. Parasites obtain nutrients or resources from the host, often causing damage, disease, or reduced fitness.

Examples include ticks feeding on mammals, tapeworms infecting the digestive tracts of vertebrates, and mistletoe plants parasitizing trees.

4. AMMENSALISM

Amensalism is a negative interaction where one organism is negatively affected, while the other organism is unaffected. The negatively affected organism may experience inhibition, suppression, or reduced fitness due to the presence of the other organism.

Examples include allelopathy, where plants release chemicals that inhibit the growth of nearby plants, and the production of antibiotics by microorganisms.

Chlorella vulgaris produces a toxin(chlorellin, an antibiotic) which is harmful to other algae.

5. CAANIBALISM

Cannibalism is a negative type of interaction of individuals in the same population. In cannibalism, bigger individual of a species kill and feeds on smaller individual of same species. Cannibalism is a natural method of population control in the ecosystem.