Problem 57 - Objective Biology for NEET

Question

Sporozoans possess (a) Spore like stage in life cycle (b) They are infectious (c) They are motile (d) Both (a) and (b)

Step-by-Step Solution

Answer

The correct answer is (d) Both (a) and (b).

Step 1: Review the properties of sporozoans

Sporozoans are a type of single-celled parasites. They have a spore-like stage in their life cycle and they can be infectious to their host.

Step 2: Match the choices with the known properties of sporozoans

From the fact established in step 1, it can be quickly seen that choices (a) and (b) are true for sporozoans. Sporozoans have a spore-like stage in their life cycle and are infectious. Choice (c) states that they are motile. However, this is not true. Most sporozoans are non-motile.

Step 3: Choose the correct choice

So, the correct option here is (d) which includes both (a) and (b).

Key Concepts

Sporozoan Life Cycle

Understanding the life cycle of sporozoans is essential for comprehending how these parasitic organisms function and spread. Sporozoans, belonging to the phylum Apicomplexa, undergo a complex life cycle that often involves multiple hosts and stages.

Typically, the life cycle begins with a spore-like stage called a sporozoite. These sporozoites are highly specialized cells that can infect new hosts. Upon entering the host, sporozoites undergo asexual reproduction to form additional cells called merozoites. These merozoites can then infect red blood cells or other tissues, depending on the type of sporozoan, and continue the cycle of asexual reproduction.

Some sporozoans also have a sexual reproduction stage, which usually happens in a different host compared to the asexual stage. The sexual reproduction leads to the formation of new spores that can then be transmitted to other hosts, continuing the infectious cycle. A well-known example of a sporozoan with such a life cycle is Plasmodium, the causative agent of malaria, which alternates between human and mosquito hosts.

Parasitic Organisms

Parasitic organisms, such as sporozoans, live at the expense of other living organisms, known as their hosts. These parasites can cause varying degrees of harm to their hosts, ranging from mild discomfort to severe illness or even death.

Parasites exhibit specific adaptations that enable them to infect and live inside their hosts. These may include specialized structures for attachment, mechanisms to evade the host's immune system, and the ability to extract nutrients from the host. Sporozoans, in particular, often possess specialized organelles at one end of their cell, known as the apical complex, which helps them invade host cells.

The relationship between parasites and their hosts can be obligate, meaning the parasite cannot complete its life cycle without the host, or facultative, where the parasite benefits from the host but is not entirely dependent on it. Sporozoans are generally obligate intracellular parasites, requiring a host for survival and reproduction.

Infectious Agents

Sporozoans are not just parasitic; they are also considered infectious agents because they can be transmitted from one host to another and cause disease. The infectious nature of these organisms poses a significant risk to public health, as they can spread through populations, contaminating water and food supplies, or being transmitted by insect vectors.

An infectious agent must be able to leave an infected host, survive in the environment or a vector, and then infect a new host. In the case of sporozoans, their spore-like stages (such as sporozoites) and other life cycle stages (like oocysts) are adapted for survival outside the host, facilitating their spread.

It is crucial to understand the modes of transmission and lifecycle of infectious agents to develop effective prevention and control strategies. The more we know about how sporozoans infect hosts and propagate, the better we can devise methods to interrupt their life cycles and reduce the incidence of the diseases they cause.