Question

Earthworms are most closely related to _______________. a. insects b. tapeworms c. leeches d. roundworms

Short answer

Earthworms are most closely related to leeches.

Step-by-step solution

Identify the Phylum of Earthworms

Earthworms belong to the phylum Annelida. Members of this phylum are characterized by their segmented bodies and include creatures like leeches.

Analyze Options Based on Phylum

Among the given options, we need to identify which organism shares the most similar traits of the phylum Annelida. - Insects are Arthropods, not Annelids. - Tapeworms are part of the phylum Platyhelminthes. - Leeches are Annelids, like earthworms. - Roundworms belong to the phylum Nematoda.

Determine the Closest Relation

Since leeches, like earthworms, belong to the phylum Annelida, they are most closely related in terms of taxonomy.

Key concepts

Phylum Annelida

Earthworms are part of the fascinating phylum called Annelida. This phylum includes organisms that are generally characterized by their segmented bodies. These segmented creatures have bodies divided into ring-like sections, allowing for more flexible movement and complex structure compared to non-segmented animals. Members of this group are often referred to as annelids.

• Includes earthworms and their close relatives, like leeches.
• Known for having a coelom, which is a fluid-filled cavity between the body wall and the digestive tract.
• Annelids have a closed circulatory system, meaning that blood travels through vessels.

These features distinguish them from other types of worms and help define their ecological roles and behavior.

Taxonomy

Taxonomy is the scientific classification system that biologists use to organize all living organisms. For earthworms and their relatives, this system helps place them in the proper biological context within the tree of life. Here's how taxonomy works:

• Kingdom: Animalia  Earthworms fall under this broad kingdom of multicellular eukaryotic organisms.
• Phylum: Annelida  This is where earthworms and leeches are grouped due to shared characteristics like segmentation.
• Class, Order, Family  Further subdivisions place species into more specific categories based on even finer traits.

Understanding taxonomy is key to grasping the relationships among different forms of life and allows scientists to predict characteristics and behaviors of related organisms.

Segmented bodies

Annelids, like earthworms, have segmented bodies which is a defining feature of the phylum Annelida. Each segment contains elements of the earthworm's internal organs, allowing for redundant functionality that aids in survival.

Segments help the worm move efficiently by allowing each segment to operate independently. This segmentation offers several advantages:

• Enhanced locomotion  Segments can expand and contract, assisting in movement through soil.
• Injury resilience  Damage to one segment can be less critical since other segments can often compensate.
• Increased complexity  Segmentation allows for the development of specialized functions within different segments.

This structure sets annelids apart from many other groups of organisms and contributes to their success in various habitats.

Leeches

Leeches are an intriguing group of annelids closely related to earthworms. Although they may look quite different at a glance, they share the characteristic segmentation of the annelids. Leeches often have a more flattened body compared to earthworms, and many are known for their ability to feed on the blood of other animals, although not all species are parasitic.

• They exhibit locomotion through body extension and contraction.
• Leeches have anterior and posterior suckers which help them attach to hosts or surfaces.
• Some species are used in medical therapies, taking advantage of their anticoagulant properties.

Despite their differences, the shared features and evolutionary history link leeches closely to earthworms, offering insights into the diversity within the phylum Annelida.

Related organisms

The phylum Annelida links earthworms not only to leeches but to a variety of other organisms that exhibit segmented bodies. These related organisms can differ vastly in form and habitat but share common lineage traits indicative of their evolutionary path.

• Polychaetes  Often marine worms with bristles, displaying vibrant colors and found in diverse ocean habitats.
• Oligochaetes  Typically includes worms like earthworms, important for terrestrial ecosystems.
• Aquatic and terrestrial species  Annelids are incredibly adaptable, found from ocean floors to garden soil.

This relationship illustrates the versatility and adaptability of annelids, making them an essential group in ecological studies and biological research.