Symbiotic Relationships

Symbiotic Relationships

High School

​

Learning Objectives

• Define symbiosis and distinguish it from other ecological interactions.

• Describe the three main types of symbiotic relationships: mutualism, commensalism, and parasitism.

• Identify the specific roles of organisms in each type of symbiotic relationship.

• Analyze and provide examples of these symbiotic relationships in different ecosystems.

Key Vocabulary

​

Symbiosis

A long-term relationship where two different species live in close association with one another.

​

Mutualism

A relationship between two different species where both organisms benefit from the interaction.

​

Commensalism

A relationship where one organism benefits and the other is not affected in any significant way.

​

Parasitism

A relationship where one organism, the parasite, benefits at the expense of the other, the host.

​

Predation

An interaction where one organism, the predator, hunts and consumes another organism, the prey.

​

Competition

An interaction between organisms that both require a resource that is in limited supply.

​

​

What is Symbiosis?

• Symbiosis is a close, long-term relationship between two different species.

• ​The name comes from Greek words meaning 'living together'.

• It is a key part of ecology, showing how species depend on each other.

• Organisms in symbiosis live in a close association, not just a brief encounter.

​

Multiple Choice

What is the best definition of a symbiotic relationship?

• A close, long-term interaction between two different species.

• An interaction where one organism hunts another for food.

• A random and temporary encounter between two species.

• A competition for the same resources between two species.

​

​

Mutualism: A (+/+) Relationship

• Mutualism is a relationship where both organisms involved receive a benefit.

• The boxer crab carries anemones on its claws for protection from predators.

• Anemones consume food particles the crab drops, receiving a meal in return.

• Gut bacteria help humans digest food, and we provide them a home.

​

Multiple Choice

In the mutualistic relationship between a boxer crab and anemones, what does the anemone gain?

• Transportation to new locations.

• Food scraps from the crab.

• Protection from predators.

• A place to hide.

​

​

Commensalism: A (+/0) Relationship

• One organism benefits, while the other organism is not affected in any way.

• This type of symbiotic relationship is often represented by the symbols (+/0).

• For example, remora fish attach to manta rays for transport and protection.

• The remora gets food scraps, but the manta ray is not helped or harmed.

​

Multiple Choice

What correctly describes the relationship between a manta ray and a remora fish?

• The remora benefits, and the manta ray is harmed.

• The manta ray benefits, and the remora is unaffected.

• The remora benefits, and the manta ray is unaffected.

• Both the remora and the manta ray benefit.

​

​

Parasitism: A (+/-) Relationship

• One organism (the parasite) benefits, while the other (the host) is harmed.

• An example is a parasitic copepod that attaches itself to a marine fish.

• The copepod feeds on the fish's tissues, causing significant harm to the host.

• This can cause injuries, gill damage, blindness, and lead to secondary infections.

Multiple Choice

In a parasitic relationship, what is the role of the organism that is harmed?

• The predator

• The commensal

• The parasite

• The host

Other Ecological Interactions

​

Predation

• ​One organism, the predator, hunts and eats another, its prey.

• ​​This interaction is typically short-term, unlike symbiotic relationships.

• ​The predator clearly benefits while the prey is harmed.

​

Competition

• ​Organisms require the same limited resources like food or water.

• ​​The interaction is negative for both parties involved in it.

• ​It reduces the growth, survival, and reproduction of the organisms.

​

Pathogen

• ​A biological agent like a virus that causes disease.

• ​​The pathogen infects another organism, which is called its host.

• ​This relationship is often considered to be a form of parasitism.

Multiple Choice

What is the key difference between predation and competition?

• Predation involves one organism eating another, while competition is a struggle for limited resources.

• In predation both organisms are harmed, while in competition one benefits.

• Predation is a long-term relationship, while competition is short-term.

• Competition involves a pathogen, while predation involves a predator and prey.

​

Common Misconceptions in Ecology

Misconception	Correction
Symbiosis always means both organisms benefit.	Symbiosis is any close relationship. Only in mutualism do both organisms benefit.
Predation is a type of symbiosis.	Predation is short-term; symbiosis involves a long-term association.
Commensalism has no effect on either organism.	In commensalism, one organism benefits while the other is unaffected.

Multiple Choice

Based on their definitions, what is the primary difference in the outcome for the organisms involved in parasitism versus commensalism?

• In parasitism one is unaffected, while in commensalism one is harmed.

• In parasitism one organism benefits, while in commensalism one is harmed.

• In parasitism one organism is harmed, while in commensalism one is unaffected.

• In parasitism both organisms are harmed, while in commensalism both benefit.

Multiple Choice

A bee gathers nectar from a flower, and in the process, it pollinates the flower, helping it to reproduce. How does this relationship demonstrate the principles of mutualism?

• The bee and the flower are competing for the same environmental resources.

• The flower is pollinated, but the bee is unaffected by the interaction.

• The bee benefits from the nectar, but the flower is harmed by losing nectar.

• Both the bee (gets food) and the flower (gets pollinated) benefit from the interaction.

Multiple Choice

A fish is observed with patchy skin damage, and it appears lethargic. Based on the lesson examples, what is the most likely cause, and what does this suggest about the fish's role in the relationship?

• It is likely in a mutualistic relationship that is failing.

• It is likely a host to parasitic copepods, which are harming it.

• It is likely a predator that was injured by its prey.

• It is likely in a commensal relationship where it is the unaffected party.

Multiple Choice

Imagine a habitat where remora fish are abundant. If the population of larger marine animals like manta rays and sharks suddenly declined, what would be the most predictable outcome for the remora fish and why?

• The remora population would be unaffected because they can survive independently.

• The remora would switch to a parasitic lifestyle to survive.

• The remora population would increase because their primary predators have been removed.

• The remora population would likely decline due to loss of transportation, protection, and food scraps.

​

Summary

• Symbiosis is a close, long-term interaction between different species.

• The three main types are mutualism (+/+), commensalism (+/0), and parasitism (+/-).

• Predation and competition are other key interactions that affect populations.

• These relationships are vital for maintaining balance within an ecosystem.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4