Symbiotic Relationship Between Living Organisms: Types and Examples
A symbiotic relationship between living organisms is a close, ongoing interaction between two different species, where at least one of them benefits. It’s a common topic in JAMB and WAEC Biology, and once you know the types, it’s easy to score well on.
Watch the video above for a visual walkthrough, or use the breakdown below if you’d rather read it straight through.
What Is a Symbiotic Relationship?
Symbiosis describes two different organisms living closely together, with at least one gaining something from the interaction like food, protection, transportation, or shelter. It’s not a one-off encounter; it’s an ongoing relationship that affects how both organisms survive.
Types of Symbiotic Relationships
There are three main types tested in JAMB and WAEC.
Mutualism: both organisms benefit. Example: bees and flowers. The bee gets nectar; the flower gets pollinated.
Commensalism: one organism benefits, the other is unaffected. Example: a remora fish feeding on leftover scraps from a shark’s meal, without harming or helping the shark.
Parasitism: one organism benefits while the other is harmed. Example: a tapeworm living in a host’s intestines, feeding off its nutrients.
A fourth, less commonly tested type is amensalism, where one organism is harmed and the other is unaffected, like a large tree blocking sunlight from smaller plants beneath it.
| Type | Organism A | Organism B | Outcome |
| Mutualism | Bee (benefits) | Flower (benefits) | Both gain |
| Commensalism | Remora fish (benefits) | Shark (unaffected) | One gains, one neutral |
| Parasitism | Tapeworm (benefits) | Host (harmed) | One gains, one loses |
| Amensalism | Large tree (unaffected) | Small plant (harmed) | One neutral, one loses |
A Quick Trick to Never Mix Them Up
To get the right answer every single time, just ask yourself these two simple questions about the two organisms:
- Does organism A benefit?
- What happens to organism B? (Does it benefit, stay completely fine, or get harmed?)
Answering both correctly gets you to the right type almost every time.
The biggest mistake most students make is confusing commensalism with mutualism. Here is the secret to remembering the difference: in mutualism, both sides are happy because they help each other. In commensalism, the second side does not care at all, it is completely unaffected.
Frequently Asked Questions
What is a symbiotic relationship between living organisms?
A close, ongoing interaction between two species where at least one benefits.
What are the main types of symbiotic relationships?
Mutualism (both benefits), commensalism (one benefits, one unaffected), and parasitism (one benefits, one harmed).
What is the difference between mutualism and parasitism?
In mutualism, both organisms gain. In parasitism, only one benefits while the other is harmed.
Final Thoughts
Once you understand the differences between mutualism, commensalism, and parasitism and memorize one solid example for each, you are fully ready.
This topic is an easy place to pack free marks in any biology exam.
