Question

Closed circulatory system is found in (a) Arthropod and chordates (b) Molluscs and chordates (c) Amphibians and molluscs (d) Annelids and chordates

Short answer

Option (d) is the correct answer, as both Annelids and Chordates have a closed circulatory system.

Step-by-step solution

Identification of Closed Circulatory System

In the biological classification, a closed circulatory system is one where blood circulates in closed vessels. Oxygen and nutrients are transferred by diffusion into the body fluids. Hence knowing the meaning of a closed circulatory system, let's further identify which groups of animals possess it.

Evaluate Each Option According to the Closed Circulatory System

1) Arthropods have an open circulatory system, whereas Chordates have a closed one, so option (a) is incorrect. 2) Molluscs mostly have an open circulatory system, while Chordates certainly have a closed one, so option (b) is also incorrect. 3) Amphibians, like other Chordates, have a closed circulatory system, while Molluscs usually have an open one, so option (c) is not fit. 4) Lastly, Annelids have a closed circulatory system, so do Chordates, we have found a match, so option (d) is correct.

Key concepts

Annelids

Annelids are fascinating creatures found both on land and in marine environments. They are commonly known as segmented worms, with a familiar example being the earthworm. Annelids are significant because they are one of the earliest groups of animals to develop a closed circulatory system.

• Annelids contain blood vessels through which the blood circulates.
• This closed circulatory system allows them to efficiently transport oxygen and nutrients throughout their bodies.
• The segmented nature of their bodies helps in localization and specialization of body functions, supportive of their circulatory organization.

Annelids' closed circulatory system contrasts with the open systems found in groups like arthropods and certain mollusks. This advancement allows for a more controlled and high-pressure flow of blood, facilitating better oxygen delivery and waste removal. These features make annelids a crucial step in the evolution towards more complex organisms.

Chordates

Chordates represent a broad and diverse group that includes all vertebrates, such as mammals, birds, reptiles, amphibians, and fish. They are known for their distinct structural characteristics, which include a dorsal nerve cord and a supportive notochord. Another defining feature of chordates is their closed circulatory system.

• The closed circulatory system in chordates involves a heart that pumps blood through a network of vessels.
• This system ensures that blood is kept separate from the body's other fluids.
• It allows for a more efficient transportation system for oxygen, nutrients, and waste products, enabling chordates to maintain their active and adaptive lifestyles.

Chordates showcase an extraordinary level of complexity and specialization. Their circulatory system reflects this, supporting various body functions and the high energy demands of many vertebrates. This system explains their ability to thrive in diverse environments across the planet.

Circulatory System Types

The circulatory system is vital for transporting nutrients, gases, and waste products throughout the body. There are two primary types of circulatory systems found in animals: open and closed.

• In an open circulatory system, seen in arthropods and many mollusks, the blood is not always contained within vessels. Instead, it bathes the organs directly in a cavity called the hemocoel.
• Conversely, a closed circulatory system, found in annelids and chordates, involves blood flowing through a systemic network of blood vessels separate from other body fluids.
• Closed systems tend to be more efficient in transporting oxygen and nutrients because the confinement allows for greater regulation of blood pressure and flow.

Understanding the differences between these systems highlights evolutionary efficiencies. The closed circulatory system supports high metabolic rates and complex behaviors and is considered an evolutionary advancement for active and larger organisms.