Problem 12 - Biology E/M

Question

$$\begin{array}{l}{\text { (A) Hydra }} \\ {\text { (B) Grasshopper }} \\\ {\text { (C) Earthworm }}\end{array}$$ Exchanges respiratory gases through hemocoels

Step-by-Step Solution

Answer

Grasshopper exchanges gases through hemocoels.

Step 1: Understanding the Options

We have three options (A) Hydra, (B) Grasshopper, and (C) Earthworm. We need to determine which one exchanges respiratory gases through hemocoels.

Step 2: Identify the Feature - Hemocoels

Hemocoels are cavities within the body of certain invertebrates where blood circulates freely, and respiratory gases can be exchanged. This is a characteristic of organisms with an open circulatory system.

Step 3: Analyzing the Organisms

We must analyze each organism: - (A) Hydra does not have a circulatory system, it uses diffusion through its body surface. - (C) Earthworm has a closed circulatory system, using vessels for blood transport. - (B) Grasshopper has an open circulatory system, where hemolymph (blood) serves to exchange gases in hemocoels.

Step 4: Conclusion

Given the analysis, Grasshopper (B) exchanges respiratory gases through hemocoels using its open circulatory system.

Key Concepts

Invertebrate Circulatory System

The circulatory system in invertebrates is quite diverse and differs significantly from that of vertebrates. Invertebrates are organisms without a backbone, and their circulatory systems vary widely.
A common type of circulatory system in many invertebrates is the open circulatory system. In this system, the fluid called hemolymph is not confined exclusively to vessels. Instead, it flows freely within the body's cavities, called hemocoels.
In contrast, some invertebrates have a closed circulatory system. This system features blood vessels that contain the blood, similar to the circulatory system in vertebrates. Earthworms are an example of invertebrates with a closed circulatory system, where blood flows through continuous tubes.
The variety of circulatory systems among invertebrates highlights their adaptability to different environments and lifestyles. Each type of system facilitates the transport of nutrients, gases, and waste products effectively, catered to the specific needs of the organism.

Open Circulatory System

An open circulatory system is one in which the circulatory fluid, called hemolymph, bathes the organs directly. This system is common in arthropods such as grasshoppers, and some mollusks. Instead of a network of blood vessels, like in closed systems, the hemolymph is pumped by the heart into body cavities, or hemocoels.
A few characteristics of open circulatory systems include:

• Direct contact between tissues and hemolymph, ensuring efficient exchange of nutrients and gases.
• A simplistic structure, which is less energetically demanding compared to closed systems.
• Suitable for organisms with slower metabolic rates, such as many insects and mollusks.

Unlike vertebrates that have complicated networks of veins and arteries, animals with open systems rely on the movement of the body and contraction of the heart to circulate the hemolymph. This system is efficient for organisms with relatively simple body plans and those that do not require high levels of oxygen.

Gas Exchange in Arthropods

Arthropods, including grasshoppers, have developed unique strategies for gas exchange due to their open circulatory systems. The key lies in their respiratory system, separate from the circulatory system, which facilitates this process via a network of tubes called tracheae.
The tracheal system in arthropods comprises tiny tubes that penetrate deep into the body tissues. Oxygen from the environment enters these tubes through tiny openings called spiracles, which are located on the surface of the body.
This system allows direct transport of oxygen to body cells and the removal of carbon dioxide. Unlike vertebrates, their circulatory system does not transport gases.

• The tracheal system provides sufficient gas exchange without the need for blood as a medium.
• Spiracles can open and close to regulate airflow and minimize water loss.
• This mechanism is highly efficient for the insect's small body size and terrestrial habitats.

Understanding this separation of functions between the respiratory and circulatory systems is key to appreciating how insects thrive in numerous environments.