Problem 77 - Objective Biology for NEET

Question

Phylum whose organism are mostly endoparasites is (a) Platyhelminthes (b) Annelida (c) Arthropoda (d) Mollusca

Step-by-Step Solution

Answer

The correct answer is (a) Platyhelminthes

Step 1: Understand Key Terms

Endoparasites live inside the body of another organism, the host, and benefit at the host's expense. The chosen phylum will have organisms that mostly lead a parasitic lifestyle.

Step 2: Option (a) Platyhelminthes Evaluation

Organisms from phylum Platyhelminthes are flatworms. A number of flatworm species are parasitic, including tape worms and flukes. These organisms are endoparasites.

Step 3: Option (b) Annelida Evaluation

Phylum Annelida consists of segmented worms such as earthworms, which are free-living, not endoparasitic.

Step 4: Option (c) Arthropoda Evaluation

Arthropods, from Phylum Arthropoda, include insects, arachnids, crustaceans, and more. While some members may be endoparasitic, this is not true for most of this phylum.

Step 5: Option (d) Mollusca Evaluation

Phylum Mollusca are invertebrates, including snails, octopus, squids, etc. These organisms are typically free-living, not endoparasitic.

Key Concepts

Platyhelminthes

Platyhelminthes, commonly known as flatworms, form a fascinating phylum in the animal kingdom. They are primitive, soft-bodied invertebrates, characterized by their flattened, ribbon-like appearance. This phylum is primarily known for its remarkable diversity and the inclusion of several parasitic species.

Flatworms play a significant role in both aquatic and terrestrial ecosystems. They can be identified by their bilateral symmetry and lack of body cavity; in scientific terms, they are acoelomates. This means their bodies are solid without a cavity in the mesoderm. This structure allows them to move easily through water sediments or the tissues of their hosts.

While some Platyhelminthes are free-living, like the planarians found in freshwater, many others have evolved into highly effective parasites. These adaptations allow them to thrive in various environments and fulfill their ecological niche.

flatworms

Flatworms encompass a wide variety of organisms within the Platyhelminthes phylum. Their name derives from their distinctive flat shape, which aids in their ability to maneuver through different environments.

Some features of flatworms include:

• Lack of specialized respiratory and circulatory systems.
• Simple digestive systems with only one opening serving as both mouth and anus.
• The ability to regenerate lost body parts, particularly in non-parasitic species.

These organisms have developed unique adaptations to lead diverse lifestyles. While the flat shape aids their parasitic movements, their simple, yet efficient nervous and muscle systems make them adept at surviving under various conditions. Even without specialized systems, they manage to thrive and persist in the ecosystems they inhabit.

tape worms

Tape worms are a fascinating subset of flatworms known for their peculiar parasitic lifestyles. Belonging to the class Cestoda, these organisms have adapted to a life inside the intestines of their hosts. They attach to the intestinal wall using specialized head structures called scolex, equipped with hooks and suckers.

Key characteristics of tape worms include:

• Segmented bodies composed of proglottids, which contain reproductive organs.
• Absence of a digestive system, as they absorb nutrients directly through their skin.
• The ability to grow to astounding lengths, sometimes over several meters long.

Tape worms are prolific breeders. Each proglottid can produce thousands of eggs, contributing to their success as endoparasites. They have a complex life cycle, necessitating one or more intermediate hosts to complete their development. These adaptations make tape worms highly specialized organisms within the Platyhelminthes phylum.

parasitic lifestyle

A parasitic lifestyle involves living at the expense of a host organism. Many organisms, including those from the Platyhelminthes phylum, have gathered various adaptations that allow them to lead such a lifestyle.

Parasitic flatworms, such as tape worms and flukes, have evolved to exploit their hosts effectively. Key features of their parasitic nature include:

• Healthcare and reproductive strategies that maximize survival and spread.
• Structural adaptations like hooks and suckers to attach securely to host tissues.
• Ability to evade host immune responses through complex life cycles.

The parasitic lifestyle presents benefits and challenges. While it offers resources that these parasites might not otherwise access, it also poses risks due to host defenses and potential host death. Nonetheless, parasites like flatworms succeed through evolutionary adaptations, ensuring their continued presence across diverse hosts and environments.