direct life cycle
includes definitive host and 1+ intermediate host
A direct life cycle is a type of life cycle that involves a single host species throughout its life cycle. It means that the parasite completes its development within a single host species, without requiring a secondary host to complete its life cycle. The eggs or larvae are directly transmitted from the host to the environment, where they develop into an infective stage that can be ingested by another host.
Examples of parasites that have a direct life cycle include tapeworms, roundworms, and some species of protozoa. For instance, the life cycle of the Ascaris lumbricoides (intestinal roundworm) involves the ingestion of infective eggs that hatch into larvae in the small intestine. The larvae penetrate the intestinal wall and travel through the bloodstream to the lungs, where they undergo further development before returning to the small intestine, where they mature into adult worms.
The direct life cycle is considered the simplest type of life cycle, and it is advantageous for parasites that are adapted to a specific host species, as they can maximize their fitness and reproductive output. However, the absence of a secondary host can also limit the transmission and spread of the parasite, as they rely on the continued presence of the host species for survival.
More Answers:
Parasites: The Importance of Host Nourishment for Survival.Biology and Importance of Parasites’ Dependence on Hosts for Survival
Obligatory Parasites: Their Impacts on Hosts and Importance of Control Measures.