Question

The unique character of sponges is (a) Choanocytes or collar cells line, the spongocoel and the canals. (b) That they are hermaphrodite. (c) That they live in marine water. (d) It reproduces by asexual means only.

Short answer

The unique characteristic of sponges is option (a) - Choanocytes or collar cells line, the spongocoel and the canals.

Step-by-step solution

- Review the Options

Start by analyzing each option individually.\n(a) Choanocytes or collar cells line, the spongocoel and the canals: Yes, Choanocytes are indeed a unique characteristic of sponges and these cells have an important role in nutrient intake.\n\n(b) Being hermaphrodite: While it is true that many sponges can produce both eggs and sperm, this characteristic is not unique to them. There are many other animal species that are also hermaphroditic.\n\n(c) Living in marine water: Many sponges are indeed primarily marine, but some species can also be found in fresh water. Moreover, living in marine water is not a unique characteristic to sponges as it is also observed in many other animal species.\n\n(d) Reproducing by asexual means only: This is not correct. Sponges can reproduce both sexually and asexually.

- Identify the Unique Characteristic

Based on the above analysis, the only option that represents a unique characteristic of sponges is option (a) - Choanocytes or collar cells line, the spongocoel and the canals. This is their unique feature as these particular cells have a critical role in their feeding and respiration. They are responsible for creating a current of water to flow through the sponges' body, through which they filter out and ingest food particles.

Key concepts

The Role of Choanocytes in Sponges

Within the porous bodies of sponges, a special type of cell known as the choanocyte, or 'collar cell,' plays an integral role in their survival. These unique cells are characterized by their flagellum surrounded by a collar of microvilli. Here's what makes choanocytes fascinating and vital to sponges:

Choanocytes line the inner chambers of sponges, such as the spongocoel, the central cavity, and the canals that run throughout the sponge's body. The whip-like motion of their flagella drives water through the sponge's body, allowing it to filter nutrients and oxygen from the water. In essence, choanocytes are the 'engine' that powers the water filtration system which is central to a sponge's way of life.

In addition to generating water currents, choanocytes capture and digest food particles. Their collars, made up of microvilli, trap these particles which are then engulfed and digested by the cell. This process of filter feeding is what sustains the sponge, making choanocytes critical to their nutrition and respiratory functions.

Hermaphroditic Species in the Animal Kingdom

Hermaphroditism is a fascinating reproductive strategy where an individual organism possesses both male and female reproductive organs. This characteristic is not unique to sponges but is also present in other species across the animal kingdom, from invertebrates like earthworms and snails to some fish species.

In sponges, hermaphroditism is quite common. These creatures are capable of producing both eggs and sperm, often not at the same time, to avoid self-fertilization. This trait provides a reproductive advantage in environments where finding a mate can be challenging. It's a versatile strategy that allows a solitary sponge to contribute genetically to the next generation, reflecting the diverse ways in which life has evolved to ensure its continuity.

Understanding Marine Biology Through Sponges

Marine biology, the study of life in the oceans and other saltwater environments, encompasses the exploration of creatures like sponges. While sponges are predominantly marine organisms, they are not exclusive to saltwater habitats; some species are found in freshwater. However, the majority of sponges thrive in the ocean, and they can be indicators of the environmental health of marine ecosystems.

Sponges can be sessile and filter feeders, playing a role in nutrient cycling and water filtration in their ecosystems. Their ability to adapt to various marine environments, from coral reefs to deep-sea habitats, makes them an integral subject of study for marine biologists looking to understand ecological relationships and the impact of environmental changes on aquatic life.

Asexual Reproduction in Sponges

Reproduction in sponges can occur in two main ways: asexually and sexually. Asexual reproduction allows sponges to create a genetically identical offspring from a part of their own body. This process can occur through budding, fragmentation, or the production of specialized structures called gemmules.

Budding involves the growth of a new sponge directly from the body of the parent sponge. Fragmentation occurs when a piece of the sponge gets detached and is capable of growing into a new individual. Gemmules are internal buds that can survive harsh conditions and germinate into new sponges under favorable circumstances.

Asexual reproduction provides a quick and effective way for sponges to increase their numbers and colonize new habitats. However, it's important to note that sponges are also capable of sexual reproduction, which introduces genetic diversity into their populations and contributes to their adaptive success.