Okay, so maybe (probably) your world is not called Earth, in fact it probably. isn't. But that's beside the point.
So, what are you going to do about the natural world of the world you built?
Of course, you could have things exactly the way they are on earth. That's the easy way. Follow all the rules of our own good-old terra cotta. Color the sky blue, the trees green, and use the good old official periodic table.
Easy as pie.
But you didn't come here to learn the easy way, did you? No, you didn't.
So how do you mess around with nature in your world. Well, let's break it down.
~The first thing to mess with are elements. You know, the periodic table. Are you going to use good old Helium, hydrogen, sulfur, Carbon, oxygen and all that good stuff? Or will you go back to the four elements: Fire, Water, Air and Earth? How about you make something up? Like ... everything's made of pillians! (don't ask me what a pillian is, I just typed what my fingers came up with.) Options are things to be explored!
~Once you've settled on what your basic elements are, the rest is easy. Now you need to determine what the water is like! Colors ... smell ... medicinal properties ... you can keep it the way it is now ... but hey, if we're changing things, we might as well change it all. Maybe water is safe to drink if it's blue, poisonous if it's green ... and turns you into a mermaid if it's purple!
|You Can see inside this Egg|
~ Color of Leaves. This is a fun one! Sure, we can stick with the color green ... but how better to make your characters go "WHERE ARE WE????!!!!" than for them to walk into a place where leaves are all a delicate shade of pink? The trick here is consistency. In our world, leaves are green because of (anyone? anyone?) chlorophyll, so, if you turn your leaves pink, you'll have to come up with a new chemical that turns them pink (maybe Pinkophyyl?).
~ Animal life. Oooh, this one's fun! Are you going to use normal horses, dogs, and cats ... or are you going to tap into mythology and pull out pegasi, jackalopes and chimeras? Or, perhaps, you want to come up with something completely different ... like a bird that looks like a flamingo, except it has cat ears! Even if you do use real and mythological beasts, that doesn't mean you have to keep the normal names! Call a horse an Equaq ... or a duck a Kakker ... have fun!
~ Climate. Is it always cold? Does it rain a lot? Do they live on the mountains? In the jungle? Does it snow? Is it a desert? Maybe it oobleks!
~ Appearance of intelligent life. You could use normal humans. Or ... you could do elves! Or FAIRIES! Do they have wings? What color is their hair/skin/eyes? How tall are they on average? An inch? A mile? How good is their vision? How smart are they on average?
Right now, that's all I can think of. If I think of more, I'll be sure to come back and add it.