Problem 8 - Biology E/M

Question

$$\begin{array}{l}{\text { (A) Hydra }} \\ {\text { (B) Grasshopper }} \\\ {\text { (C) Earthworm }}\end{array}$$ Uses nephridia to remove nitrogenous wastes

Step-by-Step Solution

Answer

An earthworm uses nephridia.

Step 1: Identify the Function

The question asks which organism uses nephridia to remove nitrogenous wastes. Begin by understanding what nephridia are: these are excretory organs in invertebrates that function similarly to kidneys in vertebrates, helping to remove waste products like nitrogenous wastes.

Step 2: Match Function to Organism

Examine the list of organisms provided: Hydra, Grasshopper, and Earthworm. Determine which one uses nephridia. Nephridia are typically found in segmented worms like earthworms, which use them to manage waste.

Key Concepts

Nephridia

Nephridia are fascinating excretory organs commonly found in annelid invertebrates. Think of them as the kidneys of the invertebrate world. Their primary role is to remove metabolic waste from the body, particularly nitrogenous waste products. You'll find these structures to be small, tubular organs that open directly to the external environment.

There are two main types of nephridia:

• Protonephridia
• Metanephridia

Protonephridia are typically present in simpler invertebrates. They feature a network of tubules that are closed at the inner end and open at the outer end. On the other hand, metanephridia are found in more advanced segmented worms like earthworms. These have both an opening that collects bodily fluids and another that expels waste.

Through the action of cilia or flagella, waste products are filtered and expelled outside the organism, maintaining a balance of body fluids and salts. This process is essential for the worm's survival in various environments.

Nitrogenous Waste

Nitrogenous waste is a group of metabolic byproducts that result from the breakdown of proteins and nucleic acids in organisms. In simpler terms, it's the waste your body produces when it uses protein.

Proteins break down into amino acids, and further into ammonia, which is extremely toxic. Different organisms convert ammonia into less harmful substances:

• Ammonia, directly in some aquatic animals, as it's rapidly diluted in water.
• Urea, transformed from ammonia, found in many mammals, including humans.
• Uric acid, prevalent in birds and some reptiles, which conserves water.

Nephridia in organisms like earthworms help expel these waste products as part of their excretory processes. By keeping their nitrogenous waste levels low, earthworms can prevent toxicity and continue thriving in moist soil environments.

This maintenance of nitrogen balance is crucial, because it affects an organism’s hydration and overall health.

Invertebrates

Invertebrates are an incredibly diverse group of animals without a backbone. They account for about 97% of all animal species on Earth. Examples include insects, arachnids, mollusks, and annelids like earthworms.

Despite their lack of a spine, these organisms often have fascinating adaptations for survival. In the case of earthworms, they have a segmented body structure that makes them efficient burrowers in soil environments.

Many invertebrates possess specialized systems for essential life functions:

• Respiration, through structures like gills or skin.
• Nutrient absorption, via a simple or more complex digestive tract.
• Excretion, using organs like nephridia,

Earthworms, for instance, use nephridia to manage waste removal efficiently. This allows them to maintain their internal environment or homeostasis, ensuring they can thrive even in challenging conditions.

Understanding these systems in invertebrates like earthworms highlights the intricate balance organisms achieve despite the absence of complex organ systems found in vertebrates.