Symbiosis- Definition, Meaning, Overview, Examples, Types

Symbiosis: Definition, Meaning, Overview, Examples, Types

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:06 PM IST

Symbiosis is the fundamental concept in biology describing a close and long-term association between two different living organisms, such as a symbiotic relationship. The definition of symbiosis in biology involves several kinds of associations, including mutualism, commensalism, and parasitism, which all describe different relationships. Symbiosis definition in biology stresses the interdependence among organisms that underlie the operation and evolution of ecosystems. There are symbiotic relationships found throughout nature, such as those that occur between the fungi and algae of lichens, or for the mycorrhizal fungi, which serve to enhance plant roots. This is the topic of the chapter Organisms And Population of Biology.

This Story also Contains

What is Symbiosis?
Types of Symbiosis
Mutualism
Commensalism
Parasitism
Amensalism
Neutralism

Symbiosis: Definition, Meaning, Overview, Examples, Types

What is Symbiosis?

Symbiosis refers to the mutual relationship between two different living organisms that can interact for an extended period depending on the kind of symbiosis. Symbiosis is said to be a close, long-term interaction between two different species. This kind of relationship is commonly known as a symbiotic relationship.

Symbiosis depends on the kind of interaction involved between species, such as mutualism, where both species benefit commensalism, where one benefits and does not affect the other and parasitism, where one species benefits at the expense of another. Symbiotic relations are important for the interpretation of ecosystems because they put across the idea that they are interconnected and dependent on each other.

Lichens are an example of a symbiotic association between fungi and algae, mycorrhizal fungi and plant roots, and clownfish and sea anemones. In general, symbiosis biology helps study how such interactions influence survival, reproduction, and adaptation. In ecology, the role of symbiosis is underscored in shaping ecosystems and driving evolution.

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Types of Symbiosis

The types of symbiosis are described below-

Mutualism

A symbiotic relationship is best characterised when both the involved species benefit from the arrangement, and one such form of symbiotic relationship is mutualism. Such a relationship can also improve the existence and breeding of both species. An example to well understand is that of the bee and the flower. Bees feed on honey that is collected from flowers and in so doing they transfer pollen needed for the production of seeds onto the flowers.

Mutualistic Relationship between Bees and Flowers

Mutualistic Relationship between Bees and Flowers

Commensalism

Commensalism is another form of showing a symbiotic relationship that is inter-species and in it one of the species benefits while the other remains unbothered in any way. An example is the bit between the barnacles and the whales. Whale lice are parasitic creatures that cling to the whale's skin to be granted a space to live at the same time, the whale is not harmed.

Commensal relationship between Barnacles and Whales

Commensal relationship between Barnacles and Whales

Parasitism

Symbiosis is the living together of two organisms different organisms living together especially with one of them being harmed or benefited. Parasitism is a type of symbiosis where one organism called the parasite benefits while the other one called the host is harmed. Such a relationship most likely hurts the host organism. An example is the association of fleas and dogs. The flea is a parasite that has a host and in this case, the host is the dog and feeds on the dog’s blood leading to uneasiness and even other health complications for the host.

Parasitic relationship between Flea and Dog

Parasitic relationship between Flea and Dog

Amensalism

Amensalism is the type of symbiosis in which one of the species is harmed or even killed with no impact on the other partner. An example is the discharge of chemical substances by some plants to retard the growth of other encroaching plants like the black walnut tree synthesizes jungle.

Comparison of Amensalism with other forms of symbiosis

Type of Symbiosis	Effect on Species A	Effect on Species B
Mutualism	Positive	Positive
Commensalism	Positive	Neutral
Parasitism	Positive	Negative
Amensalism	Negative	Neutral
Neutralism	Neutral	Neutral

Neutralism

Neutralism is quite similar to neutralism, in which the two species tolerate each other’s presence and do not interact. It is the most limited because it is a rarity in most relations since no relation is completely free of any effect. An example might be a spider living with a cactus in the desert, in which case the two are not enemies.

Also Read:

Ecology	Response to Abiotic Components
Adaptations and Habitats	Population Growth
Population Interaction	bacterial growth curve

Frequently Asked Questions (FAQs)

1. What is the definition of symbiosis in biolog

Biology tells us that symbiosis has to do with the close or long-term association that two different biological organisms have with each other. Such relationships can be symbiotic, competitive, parasitic, adverse, or indifferent, and they affect the life, development, and adaptation of individuals.

2. What are the different types of symbiosis?

The different types of symbiosis include: The different types of symbiosis include:

Mutualism: In a way, both species are in it for the taking.
Commensalism: One species is benefited while the other species remains unaffected, positive as well as negative impacts are absent.
Parasitism: The two species live in an environment in which one gains at the loss of the other.
Amensalism: The population of one species is held back or eradicated in some manner while the other is not.
Neutralism: The two species are somehow in different environments and do not intervene in the affairs of the other.

3. How does mutualism differ from commensalism?

The main difference between mutualism and commensalism is that in mutualism, both species that are involved in the interaction gain something in return, while the organism in commensalism benefits while the other neither helps nor harms them. For instance, bees feed directly upon the nectar; therefore, they are getting what they require while on the other hand, flowers benefit from the pollination behaviours of bees. The type of symbiotic relationship which exists between barnacles and whales is mutualism because barnacles receive shelter and a source of food from the body of the whale and in return, it has no negative impact on the whale.

4. Can you provide examples of parasitism?

Examples of parasitism include:

Fleas on dogs: Fleas suck the blood of the dog hence irritating the skin and or resulting in some diseases that affect the dog.
Tapeworms in humans: Tapeworms are parasites in the human body they literately live in the intestines and feed on nutrients hence causing malnutrition and other complications among other health complications for the host.
Mistletoe on trees: Mistletoe parasites nutrients and water from the trees which causes the slow death of the tree that hosts the plant.

5. Why is symbiosis important for ecosystems?

Multiplex cooperation is twice healthcare for ecosystems because it underpins the ecological and evolutionary dynamics of communities, as well as any changes affecting the survival, reproduction, and evolution of species. These interactions help mend the ecosystems by enhancing the availability of nutrients, energy flow, and the balance of the ecosystem.

6. How does commensalism differ from mutualism?

Commensalism differs from mutualism in that only one species benefits while the other is neither helped nor harmed. In mutualism, both species benefit. For example, remora fish attaching to sharks is commensalism - the remora gains transportation and food scraps, while the shark is unaffected. This contrasts with mutualism, where both partners would receive benefits from the interaction.

7. How does symbiosis contribute to the survival of deep-sea organisms?

Symbiosis is crucial for many deep-sea organisms, especially in environments like hydrothermal vents. For example:

8. What is the concept of holobiont in relation to symbiosis?

The holobiont concept views a host organism and its associated microbiome as a single ecological unit. This perspective recognizes that:

9. How does symbiosis contribute to the carbon cycle?

Symbiosis plays several important roles in the carbon cycle:

10. What is the role of symbiosis in the evolution of eukaryotic cells?

Symbiosis played a crucial role in the evolution of eukaryotic cells, as explained by the endosymbiotic theory:

11. Can you explain the concept of mutualism with an example?

Mutualism is a type of symbiosis where both species benefit from the relationship. A classic example is the interaction between clownfish and sea anemones. The clownfish receives protection from predators by living among the anemone's stinging tentacles, while the anemone benefits from the clownfish's waste products as nutrients and its presence to lure prey. This relationship enhances the survival and well-being of both species.

12. What is the symbiotic relationship between humans and their gut microbiome?

The relationship between humans and their gut microbiome is primarily mutualistic. The microorganisms in our gut benefit from a stable environment and constant nutrient supply. In return, they help us by:

13. How do lichens demonstrate symbiosis?

Lichens are a classic example of symbiosis, specifically mutualism. They are composed of a fungus and an alga (or cyanobacterium) living together. The fungus provides structure, protection, and the ability to absorb water and minerals from the environment. The alga or cyanobacterium, capable of photosynthesis, provides food for both partners. This relationship allows lichens to thrive in harsh environments where neither partner could survive alone.

14. How does symbiosis contribute to coral reef ecosystems?

Symbiosis is fundamental to coral reef ecosystems in several ways:

15. How do organisms recognize their symbiotic partners?

Organisms recognize their symbiotic partners through various mechanisms, including:

16. How does symbiosis differ in aquatic versus terrestrial ecosystems?

While symbiosis occurs in both aquatic and terrestrial ecosystems, there are some differences:

17. How does symbiosis affect the behavior of organisms?

Symbiosis can significantly influence the behavior of organisms in several ways:

18. What role does symbiosis play in evolution?

Symbiosis plays a crucial role in evolution by:

19. How do symbiotic relationships affect biodiversity?

Symbiotic relationships can significantly impact biodiversity by:

20. What is the difference between symbiosis and coevolution?

While related, symbiosis and coevolution are distinct concepts:

21. What makes parasitism unique among symbiotic relationships?

Parasitism is unique among symbiotic relationships because it's the only type where one organism (the parasite) benefits at the expense of the other (the host). Unlike mutualism or commensalism, parasitism involves harm to one partner. This creates an evolutionary "arms race" where hosts develop defenses against parasites, while parasites evolve to overcome these defenses, leading to complex and dynamic interactions.

22. Can symbiotic relationships change over time?

Yes, symbiotic relationships can change over time. What starts as one type of symbiosis may evolve into another as species adapt and environmental conditions change. For example, a commensal relationship might become mutualistic if the commensal partner evolves traits that benefit its host. Conversely, a mutualistic relationship could become parasitic if one partner starts to exploit the other more than it contributes.

23. How does symbiosis contribute to the survival of organisms in extreme environments?

Symbiosis often enables organisms to survive in extreme environments by:

24. What is the role of symbiosis in the immune system of animals?

Symbiosis plays a crucial role in animal immune systems:

25. How does symbiosis contribute to the nitrogen cycle?

Symbiosis plays a crucial role in the nitrogen cycle through several relationships:

26. What are the three main types of symbiosis?

The three main types of symbiosis are:

27. What is the difference between obligate and facultative symbiosis?

Obligate symbiosis occurs when at least one partner in the relationship cannot survive without the other. The relationship is essential for the survival of one or both species. Facultative symbiosis, on the other hand, is a relationship that is beneficial but not essential for survival. In facultative symbiosis, the organisms can live independently but may gain advantages from the relationship when it occurs.

28. How does endosymbiosis differ from ectosymbiosis?

Endosymbiosis occurs when one organism lives inside the body or cells of another organism. For example, certain bacteria living inside the gut of humans. Ectosymbiosis, in contrast, involves one organism living on the external surface of another. An example is barnacles attached to the skin of whales. The key difference is the physical location of the symbiont in relation to its partner.

29. What is the role of symbiosis in nitrogen fixation?

Symbiosis plays a crucial role in nitrogen fixation, particularly in leguminous plants. These plants form a mutualistic relationship with nitrogen-fixing bacteria (rhizobia) in their root nodules. The bacteria convert atmospheric nitrogen into a form the plant can use, while the plant provides carbohydrates and a protected environment for the bacteria. This symbiosis is vital for global nitrogen cycling and soil fertility.

30. How do mycorrhizal fungi demonstrate symbiosis?

Mycorrhizal fungi form symbiotic relationships with the roots of most land plants. This is typically a mutualistic relationship where:

31. What is symbiosis and why is it important in nature?

Symbiosis is a close, long-term interaction between two different species. It's important in nature because it allows organisms to form mutually beneficial relationships, adapt to challenging environments, and play crucial roles in ecosystem functioning. Symbiotic relationships can lead to increased survival, better resource utilization, and even the evolution of new species.

32. How does symbiosis differ from other ecological interactions?

Symbiosis is distinct from other ecological interactions because it involves a close, long-term association between different species. Unlike predation or competition, which are often short-term or intermittent, symbiotic relationships are sustained over time. Additionally, symbiosis can result in various outcomes for the organisms involved, ranging from beneficial to harmful, whereas other interactions typically have more defined roles.

33. What is the difference between symbiosis and symbiogenesis?

While both terms relate to close relationships between species, they differ in their outcomes:

34. What is the role of symbiosis in plant pollination?

Symbiosis plays a vital role in plant pollination, often in the form of mutualism between plants and their pollinators. Plants provide nectar or pollen as food for pollinators, while pollinators transfer pollen between flowers, enabling plant reproduction. This relationship has led to co-evolution, with many plants and their pollinators developing specialized structures and behaviors to facilitate their interaction.

35. How does symbiosis contribute to the digestive processes of ruminants?

Ruminants, such as cows and sheep, have a symbiotic relationship with microorganisms in their rumen (first stomach chamber). These microorganisms, including bacteria, protozoa, and fungi, break down cellulose and other complex plant materials that the ruminant cannot digest on its own. In return, the microorganisms benefit from a constant food supply and a stable environment. This symbiosis allows ruminants to extract nutrients from plant material that would otherwise be indigestible.

36. What is the difference between ectomycorrhizae and endomycorrhizae?

Both ectomycorrhizae and endomycorrhizae are types of symbiotic relationships between fungi and plant roots, but they differ in their structure:

37. What is the symbiotic relationship between acacia trees and ants?

Acacia trees and certain species of ants have a mutualistic relationship:

38. What is the difference between primary and secondary endosymbiosis?

Primary and secondary endosymbiosis are two stages in the evolution of certain eukaryotic cells: