The unique extent to which flowering plants depend upon insects, birds, and small mammals to carry their pollen and distribute their seeds has brought them into close coevolutionary relationships with these animals.
(The unique extent; depend; upon insects, birds, and small mammals) (The unique extent to which flowering plants depend upon insects, birds, and small mammals; has brought; them; into close coevolutionary relationships with these animals)
The unique extent The unique extent to which flowering plants depend upon insects, birds, and small mammals
depend has brought
upon insects, birds, and small mammals
them into close coevolutionary relationships with these animals