Arrange in a sequential manner the life cycle of the malaria parasite in the human host A. Merozoits enter red cells B. Multiplication in liver C. Sporozoites enter the human host D. Human blood enters the mosquito E. Infected mosquito bites a person Choose the correct answer from the options given below:
E, C, B, A, D
Understanding the Malaria Parasite Life Cycle in Humans
The question asks us to arrange specific events in the life cycle of the malaria parasite, specifically focusing on the sequence as it occurs involving the human host and the mosquito vector.
Let's look at the events provided:
- Merozoites enter red cells
- Multiplication in liver
- Sporozoites enter the human host
- Human blood enters the mosquito
- Infected mosquito bites a person
The malaria life cycle is complex and involves both the mosquito and the human. The stages listed here describe the transition into the human, development within the human, and the transmission back to the mosquito.
Tracing the Sequence of Malaria Infection Events
The infection begins when a human is bitten by an infected mosquito. This bite is how the parasite enters the human body.
- Event E: Infected mosquito bites a person. This is the starting point of the infection in a human.
- Event C: Sporozoites enter the human host. When the infected mosquito bites, it injects the infective stage of the parasite, called sporozoites, into the human's bloodstream.
- After entering the bloodstream, the sporozoites quickly travel to the liver.
- Event B: Multiplication in liver. In the liver cells, the sporozoites undergo asexual reproduction, multiplying into thousands of merozoites.
- Once development in the liver is complete, the merozoites are released into the bloodstream.
- Event A: Merozoites enter red cells. The released merozoites invade red blood cells, where they multiply further. This stage in the red blood cells causes the symptoms of malaria.
- Inside the red blood cells, some parasites develop into gametocytes (male and female sexual forms).
- Event D: Human blood enters the mosquito. When an Anopheles mosquito bites an infected human, it ingests these gametocytes along with the human blood. This is how the parasite is transmitted back to the mosquito to continue its life cycle.
Arranging the Malaria Life Cycle Stages
Based on the sequence described above, the correct order of the given events is:
- Infected mosquito bites a person (E)
- Sporozoites enter the human host (C)
- Multiplication in liver (B)
- Merozoites enter red cells (A)
- Human blood enters the mosquito (D)
This gives us the sequence E, C, B, A, D.
| Step | Event | Letter |
|---|---|---|
| 1 | Infected mosquito bites a person | E |
| 2 | Sporozoites enter the human host | C |
| 3 | Multiplication in liver | B |
| 4 | Merozoites enter red cells | A |
| 5 | Human blood enters the mosquito | D |
Therefore, the sequential arrangement of the life cycle events of the malaria parasite as listed is E, C, B, A, D.
Revision Table: Malaria Life Cycle in Humans
| Stage Name | Location | Process |
|---|---|---|
| Sporozoite | Bloodstream → Liver | Enters human host from mosquito |
| Schizont (liver stage) | Liver cells | Asexual multiplication (exo-erythrocytic schizogony) |
| Merozoite | Bloodstream → Red blood cells | Released from liver, infects red cells |
| Trophozoite, Schizont (blood stage) | Red blood cells | Growth, asexual multiplication (erythrocytic schizogony) |
| Gametocyte | Red blood cells | Develops from merozoites, taken up by mosquito |
Additional Information: Malaria Transmission and Stages
Malaria is caused by parasites of the genus Plasmodium, transmitted to people through the bites of infected female Anopheles mosquitoes. The life cycle has two phases: one in the mosquito (sexual phase) and one in the human (asexual phase).
- Human Phase: Begins when sporozoites are injected. They go to the liver (hepatic stage), multiply, and release merozoites. Merozoites infect red blood cells (erythrocytic stage), where they multiply, causing cycles of fever and other symptoms. Some merozoites develop into gametocytes.
- Mosquito Phase: Begins when a mosquito ingests gametocytes during a blood meal. Gametocytes develop into gametes, fertilization occurs forming a zygote, which develops into an oocyst. Oocysts produce sporozoites that migrate to the mosquito's salivary glands, ready to infect another human.
Understanding this cycle is crucial for malaria prevention and treatment strategies.
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