* Organism: An individual living thing. It can be a single-celled bacterium, a complex plant, or a large animal. Each organism is a unique entity within its species.

* Species: A group of organisms that can interbreed and produce fertile offspring. Members of the same species share a common gene pool and can generally be distinguished from other species by their shared characteristics.

Think of it like this:

* Organism: An apple tree in your backyard.

* Species: All the apple trees that can interbreed with each other.

In short:

* An organism is a single living being.

* A species is a classification that groups together many organisms that can reproduce with each other.

Let me know if you have any other questions!