What is Symbiosis?
Symbiosis can simply be defined as any kind of close and long-term relationship or association between two different biological organisms. The various types of symbiotic relationships are based on whether or not one or both organisms benefit from the relationship.
For years, the definition of symbiosis was a debate and the definition varied among scientists. Some were of the belief that it should only refer to persistent mutualism whereas some were of the opinion that the definition should apply to all persistent biological associations such as mutualism, commensalism, and parasitism with brief interactions like predation being excluded. However, the latter definition has become widely accepted in the 21st century by biologists.
Definition of Symbiosis in biology
Symbiosis can be defined in biology as a close and prolonged association between organisms of different species. In symbiosis, the organisms involved are of different species and are called symbionts.
A symbiotic relationship can be facultative or obligatory. When the symbionts in the relationship are dependent on each other, the symbiosis is said to be obligatory. A typical example of this type of symbiosis is seen in lichens that consist of fungal and photosynthetic symbionts. These organisms cannot live on their own and depend on each other for survival.
Then, when the symbionts in the relationship can live independently, the symbiosis is said to be facultative. For example, in as much as the algal symbionts in lichens like the Trentepohlia share a relationship, they can live independently.
A symbiotic relationship can also be classified based on physical attachment. It is said to be conjunctive symbiosis when the symbionts form a single body. Whereas, all other arrangements are said to be disjunctive symbiosis.
Also, it is called ectosymbiosis when one of the symbionts lives on the surface of the other like in the case of headlice on humans. When one symbiont lives inside the tissues of the other organism, it is called endosymbiosis like in the case of the genus Symbiodium that lives in reef-building corals.
The planet earth inhabits varieties of species that have to share the same resources and space. As a result, species interact in several forms of symbiotic relationships. Listed above are the six main types of symbiosis that exist among organisms. Following suit are the explanation of each of these types of symbiotic relationships.
Mutualism is a symbiotic association between two different species in a way that each species benefits from the relationship. In mutualism, two organisms interact together and both benefit from the biological interactions. The benefits associated with mutualism could be nutrients, protection, or other life functions.
This symbiotic relationship is seen as a form of biological barter where organisms trade services or resources amongst themselves. It is a type of symbiosis that is common in many organisms. However, for a relationship to be seen as mutualism, the positive effect of the relationship must be greater than the cost. If the benefits don’t outweigh the cost of the relationship, it is no longer mutualism but predation or parasitism.
Mutualism is often likened to cooperation because of the benefits associated with mutualistic relationships. However, it is quite different from cooperation in the sense that cooperation is intraspecific and exists within the same species. Whereas, mutualistic relationships are interspecific and exist between individuals of different species.
Examples of Mutualism
- Nitrogen-fixing bacteria and Leguminous plants
- Plants and humans
- Mycorrhizal association (Tree roots and fungi)
- Lichen (Algae and fungi)
- Aphids and ants
- Zebra and Wildebeest
- Intestinal flagellated protozoans and Termites
- Acacia ants and the bullhorn acacia
- Yucca moths (Tegeticula) and Yucca plants (Yucca)
- Cleaner wrasse fish and other fishes
- Anemones and Hermit crab
Commensalism is a type of symbiotic relationship between two living organisms in which one of the organisms benefits without harming the other organism. In this type of symbiosis, one of the organisms obtains food, locomotion, support, or shelter from an organism without harming it. Hence, the other organism does not benefit from the relationship but is left unharmed.
The organisms that benefit from the commensal relationship are called commensals. They are the organisms that can obtain nutrients, shelter, support, or locomotion from the host organism without the host organism benefiting or getting harmed. In most cases of commensalism, the relationship is usually between a smaller commensal and a larger host organism. The remora is a well-known example of a commensal that rides attached to sharks and other fishes.
In order for the remoras to adhere to the host organism’s bodies, they evolved a flat oval sucking disk structure on the top of their heads. Also, remoras as well as pilot fishes feed on the leftovers of their hosts’ meals. The great egret is another example of a commensal. It feeds on the insects that are turned up by mammals while grazing. There are many cases of commensalism in the ecosystem, and many of the host organisms tend to be undisturbed and unaffected by the presence of the commensal organism.
Examples of Commensalism
- Caribou (Reindeer) and Arctic fox
- Beetles and Pseudoscorpions
- Aspergillus and Humans
- Staphylococcus and Humans
- Birds and Army ants
- Nitrosomonas spp and Nitrobacter spp
- Whales and Barnacles
- Orchids that grow on branches
- Livestock and Cattle egrets
- Milkweed and Monarch butterfly
This is a type of symbiosis where one organism kills and feeds on another organism. In this biological interaction, the organism that kills and feeds on another is the predator while the organism killed is the prey. Predation is different from scavenging on dead prey even though some predators scavenge on dead prey.
Usually, predators search actively for prey, or at times they can be seen pursuing their prey or waiting as they lay an ambush to attack the prey when it crosses their path. Once, the predator succeeds in its attack on the prey, it kills it and feeds on its edible parts. All predators are highly skilled and adapted for hunting. They possess acute senses of hearing, smell, and vision for hunting. Many of them have sharp claws or jaws that enable them to grip their prey and tear it up. There are other adaptations like aggressive mimicry and stealth that some use to improve hunting efficiency.
This type of symbiotic relationship has a powerful selective effect on preys. As a result, preys adopt antipredatory mechanisms such as alarm calls, warning coloration, camouflage, mimicry, and defensive chemicals or spines. This predator-prey relationship has been the main driver of evolution since the Cambrian period. Sometimes, preys and predators find themselves in an evolutionary race: a cycle of counter-adaption and adaptations.
Examples of Predation
- Lions hunt and prey on zebra
- Bears prey on salmon
- Grasshopper feeds on leaves
- Fox hunt and prey on rabbit
- Bears feed on berries
- Rabbit prey and feed on lettuce
This is a kind of symbiosis whereby organisms compete among themselves for limited resources like space, food, mate, shelter, ecological status, etc. It is an act of rivalry that occurs in nature. Organisms constantly compete for mates, territory, resources, goods, etc in the ecosystem. The organisms competing for the limited natural resources may be of the same species or of different species.
In a competitive interaction, the fitness of one organism or species is lowered by the presence of another species. When there is a limited supply of resources needed by both species, competition takes place. Organisms in the competition are impacted negatively by the presence of each other because they will have less food or less accessibility to other natural resources.
Sometimes, the competition may be a resource other than food or space e.g male organisms of the same species can compete for the females for reproduction. However, these organisms still exist and interact together, despite the likelihood that under competition one organism may displace the other. Competition among living things may be intraspecific or interspecific.
In an intraspecific competition, the rivalry is between individuals of the same species. A typical example of this type of competition exists among plants of the same species where they grow very close and strive for soil nutrients, water, and sunlight. As these plants compete for these limited resources, they are affected especially in their structure and growth. Some plants that cannot get much sunlight tend to exhibit positive phototropism (see tropism) and bend towards sunlight. Some other plants adapt by developing bigger roots in order to absorb the soil nutrient better and some grow taller to have a better advantage over other plants when competing for sunlight.
The other type of competition, which is the interspecific competition involves rivalry between different species that inhabit the same ecological area. A typical example is seen among leopards and lions that strive and compete for similar prey. Another example is seen among herbivorous organisms of different species competing for weeds growing in the habitat.
Examples of competition
- Larger aphids compete for cottonwood leaves with smaller aphids.
- Plants of different or the same species compete for nitrogen in the soil.
- Cheetah and lions compete for prey.
- Cows and goats compete for weeds in the same habitat.
Parasitism is a type of symbiotic association between two living organisms in which a parasitic organism benefits at the expense of a host organism. This is a long-term relationship, in which an organism benefits from another organism and likely harms the organism in the process.
This is one of the symbiosis types that is unhealthy because the parasite causes discomfort to the host organisms and deprives it of nutrients. There are many parasites that carry and transmit disease, thus, in most cases, parasitic relationships cause illness to the host organism. Parasitism is different from commensalism where one organism benefits without harming the other or mutualism where both organisms benefit from the relationship.
The parasite evolves together with the host and adapts to the host as its environment. Some host organisms in order to protect themselves from parasites even build a symbiotic relationship with another species that can help them get rid of the parasite. An example is a ladybug that helps plants by feeding on the aphids that attack plants. Thus, the plant benefits from its symbiotic relationship with ladybugs as the ladybug get rid of the aphids that parasitize it.
In parasitism, the parasite lives in or on the organism and causes harm, discomfort to the organisms, or possibly death. It is not intentional for parasites to harm their host because they depend on the host body and its body functions like blood circulation or digestion are needed for the parasite to survive.
Examples of Parasitism
- Tapeworms (segmented flatworms) have a parasitic relationship with humans, pigs, and cows where they depend on the host’s partly digested food for its nutrition. They attach themselves to the intestines of their host and deprive the host organisms of nutrients.
- Fleas parasitize on humans and dogs by biting their skin which causes them to itch. They suck the blood of their host and obtain food and a warm home from them.
- Aphid insects parasitize plants as they feed on the sap of the plants they live on.
- Fungi have a parasitic relationship with hogs and cattle where it causes the disease of a lumpy jaw in them.
- Henneguya ictaluri, a parasitic cnidarian has a symbiotic relationship with catfish that is unhealthy. This parasite infects and causes proliferative gill disease in catfish.
- A parasitic fungus has a parasitic association with wheat whereby it attacks and causes wheat rust in wheat.
- Sphaerospora renicola is a cnidarian that has a parasitic relationship with carp fish whereby it causes infection in them.
This is a kind of symbiosis whereby two organisms interact but do not affect each other either positively or negatively. In this interaction, the fitness of one species has no effect whatsoever on the other species. True neutralism, however, is unlikely and extremely impossible to prove because when assessing the networks of interaction among species in the ecosystem, it is hard to assert positively that there is absolutely no competition between species or that either of the species doesn’t benefit.
Therefore, true neutralism is rare and nonexistent and is used to refer to cases where the interactions among organisms are merely negligible or insignificant. In this symbiosis type, none of the species population affects the other directly. Hence, it is the most common type of interspecific interaction as the presence of the two species does not directly affect the population level of either of them.
Examples of neutralism
- An interaction between a rainbow trout and dandelions living in a mountain valley.
- Cacti and tarantulas that live in the desert.
Other Types of Symbiotic Relationships
This is a kind of symbiosis whereby one organism lives in the tissue (either within or outside the cells) of another organism. In this relationship, the organism that lives in the tissue is called the endosymbiont which gives the cell of the host some nutrients it lacks.
This is like a reverse case of parasitism and a case of mutualism. The host produces specialized cells that favor the growth of the endosymbionts. These specialized cells affect and cause a change in the genetic composition of the host which is passed onto offspring through vertical transmission. The cells also regulate the population increase of the endosymbionts.
Endosymbionts change drastically as they adapt to their host’s lifestyle. Their genome sizes reduce due to the loss of protein-coding genes. They lose many genes during the process of metabolism as well as the repair and recombination of DNA. However, they retain the important genes that partake in the DNA-to-RNA transcription, DNA/RNA replication, and protein translation.
Through vertical genetic transmission, endosymbiotic bacteria that interact with insects are passed on to the offspring. Compared to free-living bacteria, these intracellular bacteria during the process of transmission go through many hurdles that result in a decrease in their population size.
A phenomenon occurs whereby endosymbiotic bacteria are unable to reinstate their wild-type phenotype through a recombination process. This phenomenon is called Muller’s ratchet phenomenon. The accretion of deleterious mutations in non-essential genes of intracellular bacteria is a result of the less effective population sizes and the muller’s ratchet phenomenon.
Examples of endosymbiosis
- Rhizobia (diazotrophic bacteria) live in the root nodules of legume roots and carry out nitrogen-fixing activities.
- Frankia as nitrogen-fixing bacteria lives in alder root nodules.
- Single-celled photosynthetic algae, called zooxanthellae, live in the tissues of reef-building corals.
- There are bacterial endosymbionts that provide essential nutrients to insects (about 10%-15%).
- The siboglinid tube worms have no digestive tract and rely on the symbiotic bacteria that live in them for nutrition. They both live at hydrothermal vents and cold seeps.
Ectosymbiosis is a kind of symbiosis whereby the symbiont lives on the body surface of the host and the inner surface of the ducts of the exocrine glands or digestive tract.
Examples of ectosymbiosis
- Commensal ectosymbionts such as barnacles attach themselves to whales.
- Ectoparasites like lice that live on the body surface of their host,
- Mutualist ectosymbionts like the cleaner fish that lives on and clean the body surfaces of other fishes.
Mimicry can be seen as a form of symbiosis whereby an organism mimics or adopts distinct characteristics of another organism that it may not be taxonomically related to in order to alter its relationship dynamic with the organism being mimicked, to its own advantage.
This is therefore a behavioral adaptation whereby a species evolves to look like another organism in order to help them live longer or escape predation. Some organisms can’t run or hide from their predators and so mimic other animals to trick their predators. Usually, they mimic the animals that their predators fear or don’t eat.
An organism uses this superficial resemblance to deceive another organism of natural selection where the organism of selection interacts directly with the organisms but is deceived by the similarity to another organism.
The superficial resemblance of these organisms is basically for advantageous purposes as mimicry is used to escape detection, predation, or to obtain food. This evolutionary resemblance may be between individuals of different or the same species. There are basically three species involved in this symbiotic interaction which include the model, mimic, and dupe.
The model is either a dangerous or distasteful species that another species resembles or mimics. The mimic is the species that mimics, resembles, or copies the model organism whereas, the dupe is the species that is fooled by mistaking the mimic species for the model species. However, the species deceived could be a symbiont, predator, or host depending on the type of mimicry encountered.
This symbiosis can be seen as a form of mutualism when it may be to the advantage of both species that share a resemblance. Moreso, the symbiotic relationship can be parasitic or competitive when the mimicry is to the detriment of one species. However, the evolutionary convergence between these species involved is driven by the selective action of the dupe.
However, there are cases where mimicry can evolve. For instance, a predator can perceive the similarity between a mimic and a model and changes its behavior. In mimicry, the resemblances that evolve can be visual, electric, tactile, chemical, acoustic, or combinations of these sensory modalities.
Example of mimicry
An example of mimicry is seen between palatable insects and birds. Birds make use of their sense of sight in order to select and avoid noxious insects. They can identify palatable insects and feed on them. However, these noxious insects become models for the palatable insects preyed on to mimic.
Hence, over time they may evolve to resemble the noxious insects that these birds usually avoid. The palatable insects become mimics and the birds become the dupes that are fooled to mistake the palatable insects for the noxious ones. However, the mimics and models in the case of mutualism may be referred to as co-mimics.
This is a symbiosis type between two different organisms whereby one organism is destroyed or inhibited whereas the other is unaffected. In this symbiotic relationship, the success of one organism is restricted by another without it being affected negatively or positively by the other organism’s presence. This happens when a species releases a chemical compound during its normal metabolic activity which causes harm to another organism.
There are two basic types of amensalism:
- Competition: In this type of amensalism, the smaller or weaker species is excluded and deprived of food or living space by a stronger or larger species.
- Antibiosis: This type of amensalism is also called antagonism in which one species is killed by a chemical secreted by another species which leaves the species that secreted the chemical unaffected.
Examples of Amensalism
- A sapling that grows under the shadow of a mature tree can be robbed of necessary sunlight, rainwater, and soil nutrient. However, the mature tree throughout the process is unaffected by the sapling.
- The black walnut plant (Juglans nigra) secrets a chemical called juglone that destroys and harms neighboring plants and the root zone of many herbaceous plants are destroyed.
- Weevils of the genus Tmimarcha and Spanish ibex both feed on the same type of shrub. Even though the weevils have no influence on the availability of food, the ibex being present has a negative effect on the weevils population because they consume a significant amount of the plant matter and also ingest the weevils accidentally.
- The bread mold Penicillium exhibits antagonism as it secrets a chemical, penicillin that kills bacteria.
Examples of Symbiotic Relationships
- Nitrogen-fixing bacteria and Leguminous plants
- Orchids that grow on branches
- Pseudoscorpion and beetles
- Fungus-like organism (Pseudoperonospora cubensis) and vegetables
- Viceroy Butterfly and the Monarch butterfly
- Liver flukes and ruminant animals
- Mycorrhizal association (Tree roots and fungi)
- Staphylococcus and Humans
- Livestock and Cattle egrets
- Cuckoos mimic the eggs of their host in brood parasitism
- Lichen (Algae and fungi)
- Aphids and ants
- Milkweed and Monarch butterfly
- Aspergillus and Humans
- Fig wasp and Fig trees
- Fleas and vertebrates
- Alcon blue butterfly and Ants
- Caribou and Arctic fox
- Zebra and Wildebeest
- Anemones and Hermit crab
- Intestinal flagellated Protozoans and Termites
- Spider crab and the algae
- The zone-tailed hawk mimics turkey vultures
- Birds and Army ants
- Whales and Barnacles
The above are a few examples of symbiosis.
Nitrogen-fixing bacteria and Leguminous plants
The relationship between nitrogen-fixing bacteria and leguminous plants is an example of symbiosis in nature. The root nodules that legumes form are a result of their symbiotic relationship with rhizobium (nitrogen-fixing bacteria).
Nitrogen is taken in from the atmosphere by these bacteria and passed to the leguminous plant which enables them to grow well even in nitrogen-deficient soils. The bacteria in turn benefit from these leguminous plants as they find shelter in their root cells.
Orchids that grow on branches
This group of flowering plants grows on the branches and trunks of trees. Orchids are epiphytic plants that grow mostly in dense tropical forests. They depend on their host plant for the water that flows on their branches and also depends on them for sunlight.
Since orchids do not grow large, they do not affect the host tree in any manner.
They do not extract any nutrient from the host tree because they carry out their own photosynthetic process. However, the only thing orchids obtain from their host plants is the water that flows on the outer bark. The host plant, in turn, gains nothing from the orchids. This is an example of symbiosis that is a commensal association.
Pseudoscorpion and beetles
The relationship that the pseudoscorpion share with beetles is an example of a symbiotic relationship. Pseudoscorpions usually hide in the fur of mammals and under the wings of beetles. They attach to the legs of insects to hitch a ride from one place to another and don’t harm the insect even though they may sound harmful.
Pseudoscorpions do not have a stinger like the traditional scorpion so they don’t harm the beetle. They gain from the beetle transportation and protection from predators and unfavorable weather. The beetle in turn doesn’t benefit from the pseudoscorpions and is unaffected by their presence.
Fungus-like organism (Pseudoperonospora cubensis) and vegetables
The Pseudoperonospora cubensis, a fungus-like organism has a symbiotic relationship with some vegetables. Being parasitic, it parasitizes and causes downy mildew in fruits and vegetables.
This example of symbiosis is a parasitic one as the fungus-like organism causes the downy mildew disease to the plant with which it interacts. This disease is more in wet weather because prolonged wetness of the leaf favors the infection.
Viceroy Butterfly and the Monarch butterfly
The viceroy butterfly mimics the external features of the monarch butterfly as a defensive mechanism. This symbiosis example portrays mimicry. Predators avoid the monarch butterfly because it is toxic and so the viceroy butterfly that is harmless mimics the trait of the monarch butterfly in order to protect itself.
This symbiotic relationship between these organisms is a type of Batesian mimicry. The viceroy butterfly, therefore, benefits from this relationship as it is mistaken for the monarch butterfly and is avoided by predators.
Liver flukes and ruminant animals
The liver fluke like Fasciola hepatica and Fasciola gigantica has a symbiotic relationship with ruminant animals where it parasitizes and lives in the bile ducts and the liver of these animals. This example of symbiosis is a parasitic one as the liver fluke harms its host. The liver fluke causes fascioliasis in humans.
Mycorrhizal association (Tree roots and fungi)
The mycorrhizal association formed by fungi and plants is a typical example of symbiosis. In this symbiotic relationship, the fungi infect the roots of the plant. This infection, however, is different from the type that causes the root rot diseases. Rather, the fungi invade the root of these plants to absorb nutrients and the plants depend on these mycorrhizal fungi for certain mineral nutrients.
Some plants during winter make few or no nutrients and therefore depend on these fungi for sugars, nitrogenous compounds, and other nutrients that the fungi absorb from waste materials in the soil. Hence, the fungi help keep the host plants alive as it shares the nutrients absorbed from the soil with the plant.
Furthermore, soils that contain a lot of mycorrhizal fungi especially in some lowland forests form mycelial networks that connect the trees in the forest together. These mycelial networks are advantageous to the trees and their seedlings as they make use of the fungal mycelium to exchange nutrients and chemical messages.
Staphylococcus and Humans
The relationship between the common bacterial species Staphylococcus aureus and humans can be a parasitic or commensal relationship. This is a common example of symbiosis where many strains of S. aureus are part of the skin flora of humans and can be seen in about 20%-30% of the human population.
Even though these bacteria are known to cause many illnesses and conditions they can be commensals in a symbiotic relationship. They can be seen in the oral and nasal cavities of humans because they benefit from the ambient condition that the mucous membranes in the body create.
Livestock and Cattle egrets
Livestock and cattle egrets have a symbiotic relationship that is commensal. As cattle or horses move, the egret moves along with them and sometimes can be seen on the back of the cattle.
Initially, it was assumed that these birds feed on ticks and parasites on the body of the cattle until it was later discovered that their relationship with the cattle was otherwise. They feed rather on the insects hiding in the vegetation that is stirred up when these livestock feed.
When these birds are not feeding they hop on the back of the animals to hitch a ride. Their presence doesn’t limit the movement of the cattle and the cattle are not affected by the bird because the birds are very light. As the egrets gain food and transportation, the cattle are unaffected. This type of symbiosis is commensalism.
Cuckoos mimic the eggs of their host in brood parasitism
The European cuckoo exhibits a kind of parasitism known as brood parasitism where it lays its eggs in the nest of other birds. This bird lays its eggs in another bird’s nest for the bird to foster its young cuckoo. The relationship between the cuckoos and these host birds is a brood parasitic relationship. This example of symbiotic relationship is common with the species of small songbirds as the host bird and the European cuckoo as the brood parasites.
The eggs of the host bird may vary in color and spots but there is always a striking resemblance with the eggs of the cuckoo. However, if the host bird detects a foreign egg in the nest, it might react unfavorably. It might eject the foreign egg, abandon the nest or build another nest over the first one. Consistently, the female cuckoo lays eggs with color patterns that parasitize a particular host bird species.
Cuckoos that lay their eggs and select the host birds that have similar color with their eggs tend to have more offspring than those that lay their eggs randomly and leave them to chance. However, controlling the coloration of the cuckoo’s egg is genetically determined and the choice of the right host is probably a learning process that occurs when the female cuckoo is a nestling.
Lichen (Algae and fungi)
Lichen is a result of a mutualistic relationship between algae and fungi. The fungi in this relationship provide water and minerals for the algae. In turn, the algae provide food for the fungi.
For the synthesis of food via photosynthesis, the algae utilize the minerals and water that the fungi provide them with. This symbiosis example is obligate as the algae or fungi cannot grow and reproduce without each other.
Hence, an attempt to separate the components of a lichen from each other either by laboratory or scientific means will result in the death of both the algae and fungi.
Aphids and ants
A common portray of mutualism is the ant and aphid. In this example of symbiotic relationship, aphids provide food for the ant; the ants in turn care for and protect the aphids.
Aphids parasitize plants and collect sugar-rich fluids from them which it excretes in large quantities as waste. This excreted waste is called honeydew, which becomes a sugar-rich meal for ants and attracts them. Ants become caretakers of aphids because of this honeydew ensuring the aphids are safe and well-fed.
These ants carry the aphid to another host plant once the present host plant is depleted of nutrients. Also, they aggressively defend aphids against predatory insects that try to harm the aphids. For example, ants know the ladybugs as predators of aphids and as a result, they destroy the eggs of the ladybug.
During winter, these ants still cater to aphids and carry the eggs of the aphid to their nest to store them. They do not hesitate to move the eggs once there is a change in the optimal humidity and temperature of the nest. Then, when the aphids hatch in spring, these ants transport them to a host plant to feed.
Milkweed and Monarch butterfly
The monarch butterfly and the milkweed is one of the examples of a symbiotic relationship. These butterflies attach to specific species of milkweed that contain a toxic chemical during their larval stage. The toxic chemical, a cardiac glycoside is toxic to vertebrates and as a result, the milkweed plant is avoided by many animals.
Monarch butterflies, on the other hand, are not affected by these chemicals and so throughout their lifespan, they extract and store the toxin from these plants. They are resistant to this toxin and as a result of storing it up, they become distasteful to their predators such as birds. Therefore, dues to the monarch butterfly’s symbiotic relationship with the milkweed plant, birds avoid eating them.
Aspergillus and Humans
One of the several genera of fungi and bacteria that live on and in the human body is the fungal genus Aspergillus. This fungus makes up part of the natural flora that live in humans under considerable environmental stress.
These fungi colonize the upper gastrointestinal tract in humans because that is where many of them can survive as a result of the high acidic or alkaline conditions of the gut. The gastric acid and digestive juices are responsible for this condition of the gut that is favorable to some gut flora.
Since humans cannot digest all the food they eat, the gut flora feeds on the undigested food and help to partially digest it which enable human to finish the digestion. Humans benefits as the gut flora help them in digesting the food they eat and the gut flora, in turn, gains nutrition.
Usually, there are no symptoms associated with Aspergillus and it is harmless to people with healthy immune systems breathing it in. However, in people with an immunocompromised system or underlying health issues like tuberculosis, the populations of Aspergillus can grow out of control in a condition called aspergillosis.
Fig wasp and Fig trees
The fig wasp and fig tree have a mutual relationship which exemplifies symbiosis. This interaction is an example of symbiosis that is obligate because their life cycle depends on each other. Through an opening in the fig, the queen fig wasp enters the fruit and in the process loses her antenna and wings.
This wasp carries pollen from another fig tree and deposits it inside the fig. Since the cluster of flowers and seeds of the fig are in the fig fruit, fertilization of the fig’s ovaries takes place as a result of the pollen deposited by the wasp. She lays her eggs inside the fig and dies. Then, the fig gains nourishment as it digests her body.
These eggs eventually hatch and the males and females mate with each other. The males then start to dig through the flesh of the fig while the females get busy collecting pollen grains of the fig. As the males succeed in creating an exit route, the females leave the fig carrying the pollen grains with them to another tree. This process begins the cycle of reproduction all over again of both the fig wasp and the fig tree.
Fleas and vertebrates
Fleas and vertebrates exhibit a symbiosis example that is parasitic. They parasitize warm-blooded vertebrates like dogs, ferrets, birds, rabbits, cats, dogs, rats, mice, squirrels, and humans by biting their skin which causes them to itch. These fleas suck the blood of their host and obtain nutrition as well as a warm home from them.
Alcon blue butterfly and Ants
The Alcon blue butterfly has a relationship that exemplifies mimicry as an example of symbiosis. This butterfly is one of the organisms that exhibit mimicry. These butterflies lay their eggs on the marsh gentian plant and the larvae of the butterfly leave the plant to the ground in order to attract ants.
The larvae then release a chemical that smells like the ant larvae so as to trick ants into thinking the larvae are their kind. These ants are deceived by the chemical secreted by the larvae of the butterfly and then carry it into their own brood to feed among the ant larvae.
This is also an example of brood parasitism which the European cuckoo exhibits too. As soon as the larvae of the butterfly metamorphose into an adult, it is recognized by the ants as an intruder. However, the butterfly manages to escape because it is protected by loosely attached scales.
Caribou and Arctic fox
The commensal relationship between the Reindeer and the arctic fox in the tundra is another example of a symbiotic relationship. Foxes from a distance trail the reindeer as it prowls for food. They keep a distance to avoid spooking the reindeer.
The reason the fox trails the reindeer is because it digs up the soil which exposes lichen plants. These lichen plants eventually attract subnivean mammals that come to feed on them. As these mammals are attracted to the site, they become easy targets for the fox to catch and feed on.
Zebra and Wildebeest
The zebra and Wildebeest is an example of a symbiotic relationship. These two animals have a mutualistic relationship during long-distance migration where they work together as a strategy to thwart predators.
Anemones and Hermit crab
There is a mutualistic relationship between the sea anemones and hermit crab. Anemones inhabit and hide in the shells of the hermit crab and in return for this safe habitat, they attack predators of the hermit crab by stinging them.
Intestinal flagellated Protozoans and Termites
Another common example of symbiosis that is mutualistic is the interaction of the intestinal flagellated protozoans and termites. These two organisms exhibit a type of mutualism that is obligative because the protozoan and the termites cannot live naturally without each other. Among them is a strict interdependency wherein the intestinal protozoans digest the wood that the termites ingest.
Spider crab and the algae
The algae and spider crab share a symbiotic relationship that is mutualistic. An example of symbiosis is observed in the interaction of the algae and spider crab. The algae grow on spider crab which enables the crab to camouflage and blend with its environment.
As the spider crab benefits from the disguise feature the greenish-brown algae gives it, the algae, in turn, benefits from having a place to stay on the crabs back. The spider crab becomes unnoticeable to predators as a result of this association and the algae benefit too by getting a good place to live.
The zone-tailed hawk mimic turkey vultures to catch prey
Zone-tailed hawks mimic and blend in with turkey vultures in order to catch their prey. Healthy animals barely see vultures as dangerous animals because they feed on dead or weak animals. As a result, many of them ignore the vultures flying overhead. The zone-tailed hawks on the other hand are predators that feed on healthy animals. Hence, in order to catch their prey, they disguise themselves among the turkey vulture and take their prey by surprise.
Birds and Army ants
Birds and army ants are an example of a symbiotic relationship that is weird. The commensal relationship between them is odd because both can prey on the other. Ants can feed on birds when dead and birds can prey on ants. However, the birds do not feed on the army ants because of their painful bites, aggressive nature, and poison.
Rather, the birds trail the army ant in order to feed on the insects that escape the army ants as they move across the forest floor. The birds easily catch their prey this way while the army ant remains unharmed.
Whales and Barnacles
The relationship between whales and barnacles is a symbiosis example. Barnacles cant move on their own and so they attach to other organisms during their larval stage. These crustaceans can be seen stuck to whales, shells, ships, and even rocks. It is on these surfaces that they grow and develop eventually without causing any harm to the whale.
These commensals do not feed on flesh or blood. Therefore, as the whale moves, these crustaceans feed on the plankton and other food matter at which they come across. Hence, they gain nutrition and transportation from their commensal relationship with whales while the whale is unaffected.