Answer:
Because the trophozoites are unable to survive outside a host.
Explanation:
The term infectious is used for a disease or microorganism that can be transmitted from one organism to the other organism through the environment. If we look at the two forms of Giardia, we find that out of the two forms viz. cysts and trophozoites, only the cysts of Giardia have the ability to remain alive in the environment outside the host and thus they are able to be transmitted to the other organisms. On the other hand trophozoites are not able to survive in outside environment so there is no chance of transmission of trophozoites.
Answer:
Explanation:A mechanical wave requires an initial energy input. Once this initial energy is added, the wave travels through the medium until all its energy is transferred. In contrast, electromagnetic waves require no medium, but can still travel through one.
Answer:mammals,fish, bacteria
