Problem 36 - Objective Biology for NEET

Question

Select the total number of marine sponges from the following: Leucosolenia, Euspongia, Spongilla, Sycon, Hyalonema (a) 3 (b) 4 (c) 5 (d) 2

Step-by-Step Solution

Answer

The total number of marine sponges listed is 4, hence the correct option is (b) 4.

Step 1: Identify Marine Sponges

Let's start by identifying which of the given organisms: Leucosolenia, Euspongia, Spongilla, Sycon, Hyalonema are marine sponges. According to marine biology references and online databases, Leucosolenia, Euspongia, Spongilla, Sycon, and Hyalonema are all types of sponges. Spongilla is the only freshwater sponge among them, while the rest are marine sponges.

Step 2: Count Marine Sponges

Given that Leucosolenia, Euspongia, Sycon, and Hyalonema are marine sponges, we can count them. This gives us a total of 4 marine sponges among the listed organisms.

Key Concepts

Understanding Leucosolenia

Leucosolenia is a genus of marine sponges found in shallow ocean waters. These simple multicellular organisms are part of the Class Calcarea, primarily characterized by their calcium carbonate spicules, which form their internal skeleton.

Leucosolenia sponges exhibit an asconoid body plan, one of the simplest sponge body structures, consisting of a single-layered tube that filters water through tiny pores called ostia. Water carrying food particles is drawn into the spongethrough these pores and exits through a single large opening called the osculum. Their basic structure allows students to understand the fundamental aspects of sponge feeding and water flow systems.

Euspongia, The Bath Sponge

Euspongia, commonly known as the bath sponge, belongs to the Demospongiae class, the largest class of sponges representing about 90% of all sponge species. Most of them reside in marine habitats, but there are a few freshwater species as well.

Euspongia is known for its soft, absorbent structure which makes it highly sought after for personal use. Their skeletons are made up of spongin fibers rather than the hard spicules that many other sponge species possess. The leathery textures and large pores distinguish Euspongia, offering an excellent example of how structural variations can adapt sponges to different ecological niches.

Sycon, A Marker of Complexity

Sycon represents a step up in complexity among sponges, featuring a syconoid body plan, which differs from the simplicity of asconoid sponges like Leucosolenia. In syconoid sponges, the body wall is folded into canals, which increases the surface area for filtering nutrients from the water.

These folds allow a syconoid sponge, such as Sycon, to filter more water than an asconoid sponge of a similar size. This structure showcases how sponges have evolved to maximize their efficiency in capturing food, offering students a clear progression in the complexity of sponge anatomy from the asconoid to the syconoid body plan.

Hyalonema, The Glass Rope Sponge

Hyalonema, also known as the glass rope sponge, falls under the class Hexactinellida, often referred to as glass sponges. These sponges possess a unique skeleton made of silica, giving them a glass-like appearance.

The siliceous spicules create a lattice that is both beautiful and functional, providing support and a unique filtering system. Hyalonema is known for long, hair-like structures that anchor it to the sea floor, which can be mistaken for ropes or strands of glass, hence their common name. This incredible adaptation shows the diversity of anchoring mechanisms sponges have developed, relevant for ecology and biology lessons on marine organisms.