Problem 19 - Biology the Easy Way (E-Z Biology)

Question

The circulatory system of the annelid is (a) open (c) partly closed (b) closed (d) varying

Step-by-Step Solution

Answer

The circulatory system of annelids is closed (b).

Step 1: Understanding the Circulatory Systems

Organisms can have either open or closed circulatory systems. In an open system, hemolymph flows freely through body cavities, whereas in a closed system, blood circulates within vessels.

Step 2: Analyzing Annelids

Annelids are segmented worms, including earthworms and leeches. They have a more advanced system compared to some other invertebrates, which includes vessels for blood flow.

Step 3: Determining Annelid's System

Annelids possess a closed circulatory system, which means their blood is contained within vessels such as arteries and veins, unlike an open system that lacks these vessels.

Step 4: Confirming the Answer

According to the characteristics of their circulatory system, annelids fall into the category of organisms with a closed circulatory system.

Key Concepts

Annelids

Annelids are a fascinating group of animals better known as segmented worms. This group includes creatures like earthworms and leeches that play important roles in ecosystems. For example, earthworms enrich the soil, which helps plants to grow.
Annelids can be found in various environments, from terrestrial areas to aquatic habitats. These worms are characterized by their segmented bodies which allow for flexibility in movement.

• This segmentation means their bodies are divided into ring-like segments.
• Each segment essentially contains repeated organ systems.

This trait provides an advantage in locomotion and escaping predators.

Blood Vessels

One of the key features of a closed circulatory system, which annelids have, is the presence of blood vessels. These vessels are crucial as they transport blood throughout the organism's body.
Blood vessels are classified into different types based on their function.
Here are the primary types:

• Arteries: These carry oxygen-rich blood away from the heart to various parts of the body.
• Veins: These bring deoxygenated blood back to the heart.
• Capillaries: This is where the exchange of water, oxygen, carbon dioxide, and other nutrients takes place between blood and tissues.

This network of vessels ensures efficient circulation, maintaining the organism’s internal environment.

Invertebrates

Invertebrates are a broad category of animals that do not possess a backbone or vertebral column.
This group includes diverse species like insects, mollusks, and annelids; indeed, annelids are noteworthy invertebrates because of their closed circulatory system.
Most invertebrates do not have such systems, making annelids a unique study case among them.

• They exhibit complexity despite lacking a backbone.
• Their adaptations allow them to thrive in numerous environments.

Understanding invertebrates provides insights into the early evolutionary stages of circulatory systems.

Circulatory Systems

Circulatory systems are essential for transporting nutrients, gases, and waste in animals. There are primarily two types: open and closed systems.

Open Circulatory System:

• The blood, known as hemolymph, is not confined to vessels.
• It flows in body cavities, directly bathing organs.
• This system is seen in invertebrates like arthropods and mollusks.

Closed Circulatory System:

• The blood is confined within vessels, ensuring precision in circulation.
• This system is more efficient as it allows higher blood pressure and better oxygen delivery to tissues.
• Animals like annelids, and even more complex organisms like mammals, possess closed systems.

Understanding these systems helps in comprehending how various organisms have evolved to sustain their biological processes efficiently.