a) Why do we use the word vector for a mosquito?
A mosquito is called a vector because it transmits disease-causing pathogens (e.g., Plasmodium) from one host to another.
b) What is the name of the organism that transmits malaria disease in humans and birds?
Plasmodium (a protozoan parasite).
c) What was the main purpose of Ronald Ross’s experiment?
To prove that malaria is transmitted by mosquitoes.