Problem 271 - Objective Biology for NEET

Question

Assertion: Platyhelminthes are known as flat worms. Reason: Platyhelminthes have laterally compressed body.

Step-by-Step Solution

Answer

Both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

Step 1: Understanding the Terms

First, let's understand the terms. Platyhelminthes is a classification of worms, and lateral compression refers to the flattening of the body along the dorsoventral axis, meaning the creature's body is flattened 'sideways.' In other words, they're wider than they are tall.

Step 2: Verifying the Assertion

When searching in relevant taxonomy and biology materials or reputable sources, it can be found that Platyhelminthes are indeed commonly referred to as 'flat worms.' This is due to their physical characteristics.

Step 3: Verifying the Reason

To verify the reason, we need to look at the physical structure of Platyhelminthes. With the help of appropriate resources, it can be discovered that these creatures have a body plan that is significantly flat which indeed is called being laterally compressed.

Step 4: Conclusion

After verifying both the assertion and the reason, we can say that both statement are correct and that the reason is a correct explanation of the assertion. Therefore, the assertion and the reason are both true, and the reason is the correct explanation for the assertion.

Key Concepts

Flatworms

Flatworms, scientifically known as Platyhelminthes, are a fascinating phylum of animals that are aptly named due to their distinct physical appearance. These creatures are characterized by their flat, broad body structure, which gives them their nickname as 'flatworms.' Flatworms can be found in various habitats, including marine and freshwater environments, and even as parasites in other organisms.

Some of their key features include:

• A lack of a specialized respiratory and circulatory system, which is one reason for their flat shape; this form helps in the diffusion of gases and nutrients.
• Being bilaterally symmetrical, meaning their left and right sides are mirror images of each other.

Flatworms play significant roles in ecosystems and, while some are free-living, others can cause diseases as parasites, such as tapeworms and flukes.

Lateral compression

Lateral compression is a defining characteristic of flatworms. This concept refers to the flattening of an organism's body from side to side, which allows these creatures to maintain a low profile in their environment. In the case of flatworms, their laterally compressed bodies are much wider than they are tall, almost giving them a ribbon-like appearance.

The benefits of lateral compression include:

• Enhanced ability to move through narrow spaces or crevices, which is particularly useful for both predators and parasitic flatworms.
• Increased surface area in relation to their volume, aiding in more efficient gas exchange and nutrient absorption directly through their body surface.

This body plan is particularly well-suited to their mode of living and survival tactics, as well as contributing to their distinctive flat shape.

Dorsoventral axis

In anatomical terms, the dorsoventral axis refers to the plane that runs from the dorsal (back) to the ventral (belly) sides of an organism. In flatworms, this axis is noteworthy due to their lateral compression, which is a flattening that occurs along this axis.

Understanding the dorsoventral axis is important because:

• It provides insights into the evolutionary adaptations of flatworms to their environments, highlighting how their flat shape has developed to assist in various functions, such as locomotion and respiration.
• Helps in the study of bilateral symmetry, as the flattening along the dorsoventral axis ensures that flatworms maintain symmetry crucial for their movement and interaction with their surroundings.

These aspects of the dorsoventral axis demonstrate the intricate balance of form and function in biological organisms, particularly in the unique body plan of flatworms.