hello,Martians,welcome to the earth,it is my honour to make a simple introdction of our planet.
this planet is made up of ocean,land and outer space,from which humans get resources and live on.
There are thoundsands of creatures living in the ocean,they lead their lives a little different with humans,they are swimming but not walking like humans.they are not breathing in the air but get oxygen from water.
There are also thousands of creatures on the land,like animals,plants,etc..human is one kind of animals,some Animals like human may achieve energy from food like vegetable,fruit or flesh,some only eat plant,and some only eat flesh.the animals all achieve oxygen from air,some walk by two legs,some walk by four.plants can not walk,and breath CO2,they produce xoxygen and submit into the air.
welcome to earth,you may enjoy yourself to have a free trip.