Mutualism: Symbiotic Relationships

Mutualism: Symbiotic Relationships

Mutualism describes a type of mutually beneficial relationship between organisms of different species. It is a symbiotic relationship in which two different species interact with and in some cases, totally rely on one another for survival. Other types of symbiotic relationships include parasitism (where one species benefits and the other is harmed) and commensalism (where one species benefits without harming or helping the other).

Organisms live in mutualistic relationships for a number of important reasons, including a need for shelter, protection, and nutrition, as well as for reproductive purposes.

Types of Mutualism

Mutualistic relationships can be categorized as either obligate or facultative. In obligate mutualism, the survival of one or both organisms involved is dependent upon the relationship. In facultative mutualism, both organisms benefit from but are not dependent upon their relationship for survival.

A number of examples of mutualism can be observed between a variety of organisms (bacteria, fungi, algae, plants, and animals) in various biomes. Common mutualistic associations occur between organisms in which one organism obtains nutrition, while the other receives some type of service. Other mutualistic relationships are multifaceted and include a combination of several benefits for both species. Still others involve one species living within another species. Following are some examples of mutualistic relationships.

Plant Pollinators and Plants

Insects and animals play a vital role in the pollination of flowering plants. While the plant-pollinator receives nectar or fruit from the plant, it also collects and transfers pollen in the process.

Flowering plants rely heavily on insects and other animals for pollination. Bees and other insects are lured to plants by the sweet aromas secreted from their flowers. When the insects collect nectar, they become covered in pollen. As the insects travel from plant to plant, they deposit the pollen from one plant to another. Other animals also participate in a symbiotic relationship with plants. Birds and mammals eat fruit and distribute the seeds to other locations where the seeds can germinate.

Ants and Aphids

Some ant species herd aphids in order to have a constant supply of honeydew that the aphids produce. In exchange, the aphids are protected by the ants from other insect predators.

Some ant species farm aphids and other insects that feed on sap. The ants herd the aphids along the plant, protecting them from potential predators and moving them to prime locations for acquiring sap. The ants then stimulate the aphids to produce honeydew droplets by stroking them with their antennae. In this symbiotic relationship, the ants are provided with a constant food source, while the aphids receive protection and shelter.

Oxpeckers and Grazing Animals

Oxpeckers are birds that eat ticks, flies, and other insects from cattle and other grazing mammals. The oxpecker receives nourishment, and the animal that it grooms receives pest control.

Oxpeckers are birds that are commonly found on the sub-Saharan African savanna. They can often be seen sitting on buffalo, giraffes, impalas, and other large mammals. They feed on insects that are commonly found on these grazing animals. Removing ticks, fleas, lice, and other bugs is a valuable service, as these insects can cause infection and disease. In addition to parasite and pest removal, oxpeckers will also alert the herd to the presence of predators by giving a loud warning call. This defense mechanism provides protection for the oxpecker and the grazing animals.

Clownfish and Sea anemones

Clownfish live within the protective tentacles of the sea anemone. In return, the sea anemone receives cleaning and protection.

Clownfish and sea anemones have a mutualistic relationship in which each party provides valuable services for the other. Sea anemones are attached to rocks in their aquatic habitats and catch prey by stunning them with their poisonous tentacles. Clownfish are immune to the anemone’s poison and actually live within its tentacles. Clownfish clean the anemone’s tentacles keeping them free from parasites. They also act as bait by luring fish and other prey within striking distance of the anemone. The sea anemone provides protection for the clownfish, as potential predators stay away from its stinging tentacles.

Sharks and Remora Fish

Remora are small fish that can attach to sharks and other large marine animals. Remora receive food, while the shark receives grooming.

Measuring between 1 to 3 feet in length, remora fish use their specialized front dorsal fins to attach to passing marine animals, like sharks and whales. Remora provide a beneficial service for the shark as they keep its skin clean of parasites. Sharks even allow these fish to enter their mouths to clean debris from their teeth. Remora also consume unwanted scraps left over from the shark’s meal, which helps to keep the shark’s immediate environment clean. This reduces the shark’s exposure to bacteria and other disease-causing germs. In exchange, the remora fish get free meals and protection from the shark. Since sharks also provide transportation for remora, the fish are able to conserve energy as an additional benefit.

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Lichens result from the symbiotic union between fungi and algae or fungi and cyanobacteria. The fungus receives nutrients obtained from the photosynthetic algae or bacteria, while the algae or bacteria receive food, protection, and stability from the fungus.

Lichens are complex organisms that result from the symbiotic union between fungi and algae or between fungi and cyanobacteria. The fungus is the major partner in this mutualistic relationship that allows lichens to survive in a number of different biomes. Lichens can be found in extreme environments like deserts or tundra and they grow on rocks, trees, and exposed soil. The fungus provides a safe protective environment within the lichen tissue for the algae and/or cyanobacteria to grow. The algae or cyanobacteria partner is capable of photosynthesis and provides nutrients for the fungus.

Nitrogen-Fixing Bacteria and Legumes

Nitrogen-fixing bacteria live in the root hairs of legume plants where they convert nitrogen to ammonia. The plant uses the ammonia for growth and development, while the bacteria receive nutrients and a suitable place to grow.

Some mutualistic symbiotic relationships involve one species living within another. This is the case with legumes (such as beans, lentils, and peas) and some types of nitrogen-fixing bacteria. Atmospheric nitrogen is an important gas that must be changed into a usable form in order to be utilized by plants and animals. This process of converting nitrogen to ammonia is called nitrogen fixation and is vital to the cycle of nitrogen in the environment.

Rhizobia bacteria are capable of nitrogen fixation and live within the root nodules (small growths) of legumes. The bacteria produce ammonia, which is absorbed by the plant and used to produce amino acids, nucleic acids, proteins, and other biological molecules necessary for growth and survival. The plant provides a safe environment and adequate nutrients for the bacteria to grow.

Humans and Bacteria

Bacteria live in the intestines and on the body of humans and other mammals. The bacteria receive nutrients and housing, while their hosts receive digestive benefits and protection against pathogenic microbes.

A mutualistic relationship exists between humans and microbes, such as yeast and bacteria. Billions of bacteria live on your skin in either commensalistic (beneficial to the bacteria but do not help or harm the host) or mutualistic relationships. Bacteria in mutualistic symbiosis with humans provide protection against other pathogenic bacteria by preventing harmful bacteria from colonizing on the skin. In return, the bacteria receive nutrients and a place to live.

Some bacteria that reside within the human digestive system also live in mutualistic symbiosis with humans. These bacteria aid in the digestion of organic compounds that otherwise would not be digested. They also produce vitamins and hormone-like compounds. In addition to digestion, these bacteria are important to the development of a healthy immune system. The bacteria benefit from the partnership by having access to nutrients and a safe place to grow.

Beneficial Garden Animals: What Animals Are Good For Gardens

What animals are good for gardens? As gardeners, we are all aware of beneficial insects (such as ladybugs, praying mantids, beneficial nematodes, bees, and garden spiders, to name a few) that are responsible for maintaining that delicate balance between good and bad organisms that affect the garden. However, other helpful animals in a garden are either already in residence or can be encouraged to make it their home.

What Animals are Good for Gardens?

Just as there are good and bad insects and pathogens in the garden landscape, there are also a number of beneficial wildlife vertebrates that can be lured into the garden via the provision of shelter, food and water sources.

One such example is incorporating a pond into the garden, which will encourage frog habitation as well as providing a drinking water source for all other creatures. Planting native trees and a lack of domesticated cats will foster native birds important in keeping insect populations from becoming rampant. Many types of flowers can be included in the garden to entice hummingbirds and butterflies.

Lizards, toads, and snakes are extremely beneficial garden animals and can serve to decrease the harmful insect population. Snakes can also keep an overly robust rodent population down to a dull roar.

And don’t forget bats. Bats are the major predator of mosquitoes and thus, protect us from potentially dangerous mosquito bites. A bat house can encourage these valuable mammals to make your home theirs as well. Even if there is no direct correlation between these species and the health of your plants, including native wildlife in the garden landscape creates and conserves the natural habitat of your region.

How to Attract Beneficial Animals

As mentioned, a water source such as a pond or any water feature is a powerful attraction for vertebrates and invertebrates alike. All animals need to drink water and it also gives birds a place to bathe; thereby encouraging their stay as well as a variety of bird houses for nesting sites.

Secondly, you will need areas of shelter where the animals can raise their young and hide from predators. You may want to do a Web search under “native plants,” “natural landscaping” or “wildlife landscaping” and include the name of your region to find out what plants to incorporate for animals indigenous to your area. Additionally, the local government wildlife office can assist you with information regarding the wildlife in the area and may also be able to steer you away from any potential conflicts or damage that could occur in the garden due to a particular animal.

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Consider planting for every season so the animals you are trying to attract have a safe haven whether it’s summer or winter. Evergreens are an ideal wildlife habitat in this regard, maintaining their foliage year round.

Additionally, native grasses provide cover and nesting sites for birds and small mammals all year long, as well as forage for deer, rabbits, woodchucks, field mice and others. It may also be a rich predation site for hawks, foxes, owls, coyotes, and many other wildlife; keep this in mind if you do not wish to encourage some of these predators. Not every wild animal is a vegetarian!

Also, planting plenty of vegetation with different flowering and seed times will ensure the wildlife has year round food and keep them from raiding your veggie garden. Include trees, shrubs and vines that bear seeds, cones, nuts, and berries. Many flowers, ground covers, herbs, ferns and, of course, veggies provide food for native critters. As such, you may wish to plant extra; some for you to harvest and some for your animal friends to nibble on.

Domesticated Beneficial Wildlife

You may also wish to introduce domesticated fowl such as chickens or ducks to the garden. These animals can forage in the garden; thereby reducing the number of less desirable slugs and snails and providing you with delicious, nutritious eggs. Other livestock can provide valuable manure for composting, which will benefit the garden with its nutrients, encouraging bountiful harvests.

Avoid the use of herbicides and pesticides that can be harmful or even deadly to the beneficial garden animals. Never feed the wild animals directly. This can encourage them to go where they are not welcome, reduce their natural instinct in self-preservation and cause conflict which could result in their injury or even death.

The benefits of ants for the forest, garden, animals and humans

Army Ants (Eciton hamatum and Eciton burchelli)

In the tropical rainforest, ants are everywhere. Ants are the most abundant animals, and their total «biomass,» or how much they all weight when put together, is heavier than any other group of animals in the rainforest.

There are many different kinds of ants in a tropical forest. In fact, the famous researcher named E. O. Wilson found over 200 species of ants on a single tree!

The picture to the right is a swarm of army ants, named because they run around in giant raiding groups. Army ants eat other ants and any kinds of insects or arthropods they can find on the forest floor. They are of little danger to humans and other mammals, although the majors (the ones with the big heads) can bite pretty hard.

Leafcutter Ants (Atta cephalotes)

These little ants do a lot of big work in the rainforest. You will usually see worker ants following each other single file into and out of their underground nests. Worker ants carry pieces of leaves along well built trails into the nest. A smaller pilot «hitchhiker» ant usually protects the leaf and the worker ant from pesky parasites (wasps, phorid fly). Without the protection from this tiny ant the entire colony could be destroyed due to infestation from parasite eggs. The worker ant carries the leaves to smaller workers which chew the leaf into smaller pieces, making it all sticky. The sticky leaf mass is then added to the fungus garden that the ant colony eats. The ant needs to defecate (poop) on the leaves in order for the fungus to grow. All of the ants work to take care of the fungus garden, growing fungus just like we grow food. They have help from a bacterium that grows right on their bodies. The bacterium protects the garden from disease. These ants are very sensitive about the needs of their gardens and ‘talk’ to them with chemical signals. They are very important to the rainforest ecosystem.

Bullet Ant (Paraponera clavata)

The Bullet Ant got its name because it’s sting feels like being shot by a bullet. It is the most painful sting of any of the Neotropical rainforest’s ants. Bullet Ants get up to one inch or 2.5 cm in length.

Ants are related to bees and wasps, all belonging the insect order, Hymenoptera. Some ants sting like the bullet ant, and some do not even have stingers. Others use acid to burn your skin.

Check out the video of Bullet Ants coming out of their den below.

Copyright Gerald R. Urquhart
Michigan State University

Students and teachers have permission to quote text and use images from this website in class assignments. Images may be used in classroom and academic presentations with notification of author. All other use should request permission.

Virtual Rainforest development supported by grant #0815966 from the

Benefits Of Insects and FREE Insect Worksheet

When we think of insects, most of us think of pests. We think of them as a nuisance that need to be squished, sprayed, exterminated or ran from. They carry the big “ewwww” factor.

Over at Creation Conversations, Dr. John Ashton wrote an article on termites. He spoke of the destructive nature of these wood eating little beasts that we all associate with termites. However, he went on to describe how some types of termites actually benefit us by fertilizing the soil. This got me thinking. Maybe insects aren’t all bad all the time.

What are the benefits of insects?


Honey bees, moths and butterflies pollinate plants. Without theses pollinating insects, plants wouldn’t reproduce. Without plants, we couldn’t survive.


Insects help with decomposition. For example, when trees die, insects move in, tunnel and colonize the wood. Some eat the wood and some eat the wood eaters. This helps break down the trees much faster than microbial decomposition alone.

Honey and Beeswax

Honey bees make honey and beeswax. Honey has been a sweetener source for centuries and beeswax is still used for candles, cosmetics and more.

Without silkworms, we would not have silk. Silkworms make silk fiber that is spun into cocoons. These cocoons are collected and unraveled to obtain the silk fibers.

Insects are food for animals and humans. Raccoons, birds, some snakes and lizards, frogs, fish are some animals that rely on insects for their food source. In many parts of the world, humans eat insects, as well. They are know to be nutritious, plentiful and quite tasty. (I’ll take their word on it. yuck)

Pest Control

Some insects are helpful to humans in that they actually help control the nuisanse insect population. For instance, ladybird beetles feed on aphids that destroy flowers and crops. Farmers and gardeners have been known to release ladybird beetles onto their crops as a means of controlling harmful insect populations without the use of chemicals.

Have you ever thought of insects as anything but pests? All creatures serve a purpose in the ecosystem. Who will do their job if one of them is removed? All creatures are important. Except for gnats. I can’t find a reason for gnats. Just sayin.


Термины в модуле (49)

e.g., plant pollination (figs and fig wasps; hummingbird-flower, etc.)

bacteria are closely associated with roots; bacteria provide additional source of nitrogen that plants can use when there otherwise might not be any available

Plants fight the ants with a chemical defense in their leaves (+/-) but ants circumvent plant defense by using fungus to digest leaves (+/-/+).

2) buffalo and oxpecker

Ants benefit from aphids because they eat them (trophic).

Bull’s horn acacia trees provide:
1) newly developed bull’s horns (evolutionarily enlarged thorns) filled with a pith that ants easily remove, creating hollow interiors that ants use as a home — safe place to lay eggs
2) extra-floral nectar secreted from glands at the base of leaves
3) beltian bodies=form of protein and fat-rich ant food supplied by trees

(a) Methods: fumigated a sample of Acacia cornigera trees to remove Pseudomyrmex ants. Kept ants from re-colonizing experimental trees using «tanglefoot» (sticky goo) at the base of the trees. Monitored plant growth of cut, re-growing suckers (stems), and ant activity at experimental (defaulted) versus control trees (containing normal densities of ants).

(b) Results: (1) Experimental trees had far less total regrowth, total number of leaves and total number of swollen thorns than did control trees. Therefore, ants have a huge affect on growth, leaves and thorn production. (2) Experimental trees had more insects per shoot during the day time and the nighttime. Therefore, when you remove ants, more insects overtake the Acacia plant.

It is important to keep the pseudomyrmex ants faithful because (1) ants are vital to Acacia fitness and (2) it is expensive to the plants to produce Beltian bodies and nectar secretions year-round.

Unique ant Acacia traits (compared to other species of Acacia): (1) Beltian bodies (with specific protease inhibitors); (2) hollow thorns; (3) nectaries with sucrose, invertase and chitinase secretions.

(2) The outcome depends on the parameter values, as they determine the slopes and y-intercepts of the isoclines.

(1) nitrogen-fixing alders are prevalent in nutrient-poor bogs
(2) legumes in tropics often dominate in nitrogen-poor soils
(3) plants with mycorrhizal fungi are prevalent in phosphorus-poor soils
(4) coral prevalent in nutrient-poor (carbon-limited) tropical waters
(5) termites and cattle use microbial mutualists to digest cellulose (plant cell walls and wood, difficult-to-digest)

(2) cattle and cow egret: egret acts as food beaters because as they graze and move around they pick up insects that cow egrets feed on; cattle are not hurt

(4) algae growing on sloth: larvae graze on algae, but sloth is not harmed

(5) birds feed on leftover carcasses

(6) burrs are transported by humans/animals; humans/animals are unharmed

(7) barnacles on a whale

(8) birds nest in trees

(9) yellow bellied sap suckers and trees: yellow bellied sap sucker drills holes in trees, holes secrete nectar that sap suckers feed on; they don’t do enough damage to harm/kill the tree

(10) diverse trees, shrubs, grasses provide substrate for bird nests

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