Question

Assertion: Nephridia help in osmoregulation in earthworm. Reason: Nephridia maintain fluid and ionic balance in earthworm.

Short answer

Yes, the assertion is correct and the reason is valid. Nephridia do help in osmoregulation in earthworms by maintaining fluid and ionic balance.

Step-by-step solution

Understanding Nephridia and its Role

To begin with, Nephridia are tube-like structures present in every segment of an earthworm's body except the first three. These structures primarily function for excretion. They remove waste materials from the worm's body, thereby playing a significant role in maintaining the internal environment of the organism. They perform a function analogous to kidneys in humans.

Explaining Osmoregulation

Osmoregulation refers to the process of regulating water potential and maintaining homeostasis in an organism's body, that is, maintaining a balance of water and ions in the body fluids. This is crucial for the survival of all organisms.

Connecting Nephridia and Osmoregulation

Nephridia, by excreting waste materials, play an important part in osmoregulation. They are actively involved in maintaining the fluid and ionic balance in an earthworm's body. They remove excess water, salts, and other wastes from the body, which helps in maintaining the osmotic balance. Thus, the reason 'Nephridia maintain fluid and ionic balance in earthworm' supports the assertion 'Nephridia help in osmoregulation in earthworm.'

Key concepts

Nephridia Function

Nephridia are to earthworms what kidneys are to humans. These minute, tube-like structures play a pivotal role in the excretory system of annelids, including earthworms. Each segment of an earthworm, except the foremost three, houses a pair of nephridia.

Functionally, nephridia filter out waste material from the body cavity or the bloodstream of the earthworm. They absorb the waste products from the coelomic fluid – which is a fluid that fills the body cavity of the worm. Through a series of intricate steps involving filtration and reabsorption, nephridia manage to expel waste in the form of urea, maintaining the worm's internal chemical balance.

The waste expelled from the nephridia ultimately exits the worm's body through tiny pores on its skin surface. This process of waste removal is not only critical for excreting toxic substances but is also intrinsically tied to the regulation of the worm's internal fluid and electrolyte levels, demonstrating a key aspect of osmoregulation.

Homeostasis in Organisms

Homeostasis is the self-regulating process by which an organism maintains stability while adjusting to conditions that are optimal for survival. This involves various physiological processes that manage the balance of fluids, temperature, pH, and concentration of electrolytes.

In earthworms, homeostasis involves the regulation of their internal conditions like fluid balance and ionic concentration, which are kept constant through the action of nephridia. For example, when an earthworm is in a dry environment, its nephridia conserve water in the body by excreting more concentrated urine. Conversely, in a moist environment, the urine may be more diluted to expel excess water.

The principle of homeostasis is fundamental in all living organisms and encompasses a broad range of biological functions. From humans sweating to lower body temperature to plants opening or closing stomata for gas exchange, the homeostatic mechanisms ensure that organisms can adapt and thrive in fluctuating environmental conditions.

Excretory System in Annelids

The excretory system in annelids is an elegantly simple yet efficient mechanism that serves to remove wastes and maintain the chemical constancy of the internal fluids. This system predominantly consists of nephridia, which function much like a filtration and excretion unit.

Metabolic activities within the earthworm, as with all living organisms, result in the production of wastes such as ammonia, which is toxic if allowed to accumulate. Annelids convert ammonia into less toxic substances through metabolic processes and then nephridia efficiently handle the excretion of these substances.

The nephridia make this system standout by showcasing a segmentally arranged network through the worm's body. This repeated segmentation means that waste removal is a localized process, with each segment dealing with the metabolic waste produced therein. This local waste management, paired with a closed circulatory system, is what allows these creatures to live in varied environments while maintaining their internal environment—a testament to the effectiveness of the excretory system in annelids.