a tree is a kind of plant & a vegetable is a mean of set ->  a tree is a kind of organism  a specific is a mean of frog & trees require a certain thickness of soil to grow -> trees are a kind of organism that require a certain thickness of soil to grow trees are a kind of organism that require a certain thickness of soil to grow  trees are a kind of organism that require a certain thickness of soil to grow & the decrease of something required by an organism has a negative impact on that organism 's survival -> a increase in sand fluidity can effect protect to four a decrease in soil thickness can cause harm to trees  a increase in sand fluidity can effect protect to four & drought decreases the thickness of soil -> drought can cause harm to trees by decreasing the thickness of soil