When trying to identify species you will sooner or later encounter “keys”. Mostly, they are binary keys. This means you always choose between two possibilities. But there can be more, sometimes there are three possibilities.
On this site I used expandable paragraphs to make it easier to navigate the keys.
The example is for types of objects.
Look at the first two possible traits you can choose. Choose the one that fits. Expand (click) it. And continue to do so:
1a. The object is bigger than a car.
2a. The object is a planet
3a. The object has liquid water
Earth – you found the “species”, therefore it is green
3b. The object is red
Mars – you found the “species”, therefore it is green
2b. The object is not a planet
Uh oh! Here is a warning to not confuse similar properties and be aware of outdated info! (Like pluto is not a planet anymore)
4a. The object is a plant
A tree! – you found the “species”, therefore it is green
4b. The object has the faces of presidents on it
Mount Rushmore – you found the “species”, therefore it is green
1b. The object is as big as a car.
A car – you found the “species”, therefore it is green