Direct Life Cycle vs. Indirect Life Cycle

The term direct and indirect life cycle is used to denote the life cycles of a parasite. The main difference between direct and indirect life cycle is, in direct life cycle the parasite lives and reproduce inside the host. But some parasites are complex and they need multiple hosts to reproduce, such a life cycle is known as indirect life cycle.

What is Direct Life Cycle?

Parasites are small microscopic organisms that live inside a host cell. Some parasites are obligate parasites, that is they live and reproduce inside a host cell while some can even reproduce outside a host cell. In some cases, host cell even gets benefit from a certain parasite. Some parasites are known to cause harm to the host. Simple parasite reproduce and live inside single host, this is an example of direct life cycle. In direct life cycle, parasite lives its entire life inside the host and reproduce inside it. Such animals or organisms that harbor parasites are suppose to provide shelter and food to the parasite and such a host is called definitive host.

What is Indirect Life Cycle?

In this type of life cycle of  a parasite, it cannot survive inside one host solely. They need to have multiple hosts so that they can reproduce more. A complex type of parasite have this type of life cycle. They infect many host and are that is why more virulent than simple parasites. For their food and shelter, they depend upon host cell. If parasites would not have been able to harm the host cell they they would have died, their existence would have came to an end. Some parasites are also known to cause great degree of harm to the host cell, eventually killing it. Such parasites depend upon the destruction of many host cells. Main purpose of these parasites for having an indirect life cycle is usually reproduction.

Key Differences between Direct Life Cycle and Indirect Life Cycle

  1. In direct life cycle, there is usually single host. In indirect life cycle, there are multiple hosts.
  2. In direct life cycle parasites are not as virulent as in indirect life cycle.
  3. The main purpose for having multiple hosts in indirect life cycle of a parasite is reproduction.
  4. Simple parasites have direct life cycle while complex parasites have indirect life cycle.
  5. Parasite is known to complete its whole life in just one host in direct life cycle but it switch hosts in indirect life cycle.

Video Explanation

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