Question

Annelids and cephalopods have a(n) _____ circulatory system. a. open b. closed

Short answer

Both annelids and cephalopods have a closed circulatory system.

Step-by-step solution

Understanding the Question

We need to determine the type of circulatory system that annelids and cephalopods have. The options given are open and closed circulatory systems.

Defining Open Circulatory System

In an open circulatory system, blood is not entirely contained within blood vessels. Instead, it flows freely through cavities, coming into direct contact with tissues and organs.

Defining Closed Circulatory System

A closed circulatory system has blood contained within vessels at all times. The blood is pumped by a heart and circulates through the body in a series of tubes or vessels.

Characteristics of Annelids

Annelids, such as earthworms, have a closed circulatory system. In these organisms, blood is pumped through a series of vessels, allowing efficient nutrient and gas exchange.

Characteristics of Cephalopods

Cephalopods, which include squids and octopuses, also have a closed circulatory system. Due to their active lifestyles, a closed system allows for more efficient circulation and oxygen distribution.

Conclusion

Both annelids and cephalopods possess a closed circulatory system. Therefore, the correct option is b. closed.

Key concepts

Annelids

Annelids are a fascinating group of invertebrates that include creatures like earthworms and leeches. What sets them apart is their closed circulatory system. This system is highly efficient and involves blood being fully enclosed within vessels. This structure ensures that blood circulates smoothly and consistently, delivering oxygen and nutrients swiftly to all parts of the body.

The closed circulatory system of annelids is quite intricate. It involves a network of vessels, including dorsal and ventral blood vessels, along with a series of smaller capillaries. This network is complemented by sections of muscles that help pump blood, mirroring the function of a heart.

Annelids benefit from this system because it allows them to effectively manage nutrient and gas exchange. Unlike an open circulatory system where blood bathes the organs directly, the closed system in annelids ensures that blood remains under pressure as it swiftly moves through the body. This efficiency is useful for their underground, burrowing lifestyle.

Cephalopods

Cephalopods, such as squids, octopuses, and cuttlefish, are known for their intelligence and agile movements. These marine animals also have a closed circulatory system, which plays a crucial role in supporting their active lifestyles. Unlike simpler organisms, cephalopods possess hearts that ensure blood is kept under pressure as it courses through a network of vessels.

This network is composed of arteries, veins, and capillaries, facilitating efficient transportation of oxygen and nutrients throughout their bodies. The unique feature of cephalopods is their multiple hearts: a systemic heart that pumps blood to the body, and branchial hearts that direct blood to the gills for oxygenation. This system enables cephalopods to engage in rapid, sustained swimming, essential for escaping predators and hunting prey.

Moreover, the efficiency of a closed circulatory system allows cephalopods to maintain high metabolic rates. This is particularly beneficial for their complex nervous systems, supporting their capability for problem-solving and advanced predatory tactics.

Circulatory System Types

The circulatory system is a vital part of any organism, responsible for transporting nutrients, oxygen, and waste products throughout the body. We can categorize circulatory systems into two main types: open and closed.

In an open circulatory system, blood is not entirely confined to vessels. Instead, it flows freely through body cavities where it directly bathes organs and tissues. This type of system is characteristic of many invertebrates, such as insects and crustaceans. However, it is less efficient in terms of nutrient delivery and waste removal.

On the other hand, a closed circulatory system, like those found in vertebrates, annelids, and cephalopods, keeps blood enclosed within vessels. This system is equipped with various vessels, such as arteries, veins, and capillaries. The main advantage of a closed system is its efficiency in maintaining high blood pressure, enabling quick delivery of oxygen and nutrients and equally rapid removal of carbon dioxide and waste products.

Studying these circulatory systems reveals the adaptive strategies different organisms have evolved to meet their energy and metabolic needs based on their lifestyle.