Problem 90 - Objective Biology for NEET

Question

Annelids may be (a) Aquatic (marine and fresh water), terrestrial (b) Free living (c) Parasite (d) All of the above

Step-by-Step Solution

Answer

The correct answer is (d) All of the above. Annelids can be aquatic, terrestrial, free living, and parasites.

Step 1: Consider each option individually

First, look at each option separately. Annelids are known to be both aquatic (including marine and freshwater environments) and terrestrial, so option (a) is correct. Annelids can also be free living, meaning they do not depend on a host for survival, which makes option (b) correct. Additionally, some annelids, like leeches, are parasites which means option (c) is also correct.

Step 2: Consider the 'All of the above' option

Next, consider option (d): 'All of the above.' Since options (a), (b), and (c) have all been determined to be correct, option (d), which suggests that all other options are true, is also correct.

Key Concepts

Annelid Habitats

Annelids, also known as segmented worms, display an incredible ability to adapt to a wide range of habitats. Not limited to a single environment, these creatures are found in locations as diverse as marine depths and terrestrial soils.

Marine annelids often dwell in the sediments of the ocean floor while freshwater species might be found in streams, rivers, and ponds. Terrestrial annelids, like the common earthworm, significantly contribute to soil fertility and are vital for agricultural processes. Their activity in the soil enhances nutrient cycling, soil structure, and aeration, thus promoting plant growth.

Understanding the various habitats of annelids is key to appreciating their ecological roles and the sheer diversity of life within this phylum.

Free-living Organisms

The term 'free-living' describes organisms that do not rely on other organisms for food or shelter. Many annelids are free-living, thriving independently in their environment.

Free-living annelids, such as the ragworms and earthworms, play a critical role in their ecosystems by recycling nutrients as they consume organic material. These creatures can also be great indicators of environmental health because they require certain conditions to survive.

Their survival strategies include a variety of feeding habits, such as scavenging on dead organic materials or hunting smaller invertebrates. The concept of free-living organisms highlights the autonomy and resilience these annelids exhibit within their respective ecosystems.

Parasitic Annelids

While many annelids live independently, some have adopted a parasitic lifestyle, depending on a host organism to survive. Leeches are the most famous examples of parasitic annelids, known for their blood-sucking behavior.

These annelids have specialized structures such as suckers for attachment to their hosts and enzymes in their saliva that prevent blood clotting, facilitating their feeding process. Though often viewed with aversion, medicinal leeches have been used in human medicine to reduce blood coagulation and stimulate circulation in tissue grafts.

Parasitic annelids provide fascinating case studies of coevolution, as they must continually adapt to the defenses of their hosts to survive. Their complex interactions with their hosts add another layer to the biological and ecological significance of the annelid phylum.