Question

Why is earth called a terrarium?

Answer 1

because our planet is like a giant greenhouse. Earth's atmosphere absorbs and holds heat from the Sun through a process called the greenhouse effect. ... Of course, Earth doesn't work exactly like a terrarium.

Answer 2

Terrarium is actually an artificially made greenhouse glass container where sunlight easily passes through and we give other necessary objects for the plant growth inside the glass container.

And our earth is very similar to the terrarium ,our mother nature gives all the necessary objects for plant growth.

That's why we can call our planet as a natural terrarium.