Are human beings a organism?
Yes. Human beings are living organisms because they are composed of cells inside their body.
Malaria is a disease which involves a parasitic organism (a type of paramecium) that lives inside mosquitoes for part of its life-cycle and inside human beings for another part of its life-cycle; it is the mosquitoes and the human beings which are serving as host organisms to the parasite. So no, malaria is not a host.
Any structure that is reduced in function in a living organism but may have been used in an ancestor is known as a vestigial structure?
yes and no. yes some animal and organism are afected by pollution. no, new experiment has proven where organism survives twice the amount of toxic . If human beings get exposed to the same amount of toxic they will die. some organism survives in the most dangerous place. all life and earth evolves from organism.