Biotic interactions refer to the effects that organisms in a community have on each other. These interactions can be either intraspecific, between individuals of the same species, or interspecific, between individuals of different species. They may be short-term, such as pollination and predation, or long-term, and often play a significant role in the evolution of the species involved. Biotic interactions can also be indirect, occurring through intermediaries like shared resources or common enemies. Overall, understanding biotic interactions is essential in ecology for comprehending the functioning of ecosystems and the maintenance of biodiversity.

1. Positive interaction refers to a type of relationship between different species that is beneficial for one or both partners, without causing harm to either. The benefits of such relationships can come in the form of food, shelter, substratum, or transport.

• Positive interaction can be categorized into three main types: 

1. Mutualism:

In a mutualistic relationship, both species involved derive benefits from the interaction. This relationship can be either obligatory, meaning that the organisms are dependent on each other for survival, or facultative, where the interaction is optional but still beneficial for both parties.

For Example: Lichens are a symbiotic relationship between fungi and algae, where both depend on each other for survival. The fungus provides moisture, minerals, and protection to the algae, while the algae produces food through photosynthesis. It’s a close and permanent relationship that is obligatory for both species.

2. Commensalism:

Commensalism is a type of relationship between different species where one partner benefits while the other is neither benefited nor harmed. The partner that benefits in this relationship is called the commensal.

For Example: Commensalism is exemplified in various ways in nature, including the relationship between a bird and a tree. The bird is provided with shelter and protection by the tree without causing any significant harm to it. Another common example of commensalism is the cattle egret bird feeding on insects that are stirred up by feeding cattle.

2. Negative interaction refers to a type of association between two or more individuals where one or both of them are harmed. The harm can be caused by various factors, such as predation, competition for resources like food, excretion of harmful waste, and more.

Negative interaction can be further subdivided into different categories, including:

1. Parasitism:

Parasitism is a type of interaction between two organisms, where one (known as the parasite) obtains its nutrients from another living organism (known as the host). While a parasite may obtain food from the host, it typically does not kill it.

For Example: Parasites including external parasites or ectoparasites such as ticks, mites, and lice in animals. Fungal parasites like Erysiphe (powdery mildew), Ustilago (smut), and Puccinia (rust) cause diseases that can result in significant losses of economically important crops.

2. Predation: Predation is a type of interaction between two species where one species (the predator) hunts and kills another species (the prey) for food. Unlike parasites, predators are free-living and typically kill their prey.

For Example: A tiger (predator) hunting and eating a deer (prey), or a frog preying on insects.

3. Competition:  

Competition is an interaction between organisms or species where both are negatively affected. This happens when there is a limited supply of at least one resource, such as food, water, or territory, that both the organisms or species depend on.

4. Antibiosis: 

It is a phenomenon where one organism completely or partially inhibits the growth or survival of another organism by secreting a substance or modifying its immediate environment. The substances or conditions produced by an organism are typically harmful to the other organism. Antibiosis is commonly observed in microorganisms that secrete substances known as antibiotics.

For Example: Bacteria, actinomycetes, and fungi are known to produce several antimicrobial substances, which are commonly found in nature. In addition, lichens and many higher plants are also known to produce substances that can inhibit the growth of molds and bacteria.