Corrected sentences (simple):
Earth is the only planet we know that has life. Tiny bugs and giant whales all live here.
Another natural way to say it:
Our planet Earth is the only planet we know of where life exists. From tiny bugs to giant whales, all kinds of living things live here.
Why I changed the sentences — step by step (easy to understand):
- Capitalization: We write Earth with a capital E because it is a name, like a person’s name.
- Softer wording: "we know that has life" or "we know of where life exists" sounds more natural than "where we know life exists."
- Clear subject: The word "they" in the second sentence could be confusing. Saying "Tiny bugs and giant whales all live here" names who you mean right away.
- Simple words: For a 7-year-old, "live here" is clearer than "enjoy living here," which talks about feeling. Either is okay, but "live here" is a straightforward fact.
Try this: Which sentence do you like best? You can read them out loud and pick the one that sounds nicest to you.