Question

Solenocytes and nephridia are respectively found in:
A. Platyhelminthes and Annelids
B. Annelids and Nematoda
C. Cnidaria and mollusca
D. Mollusca and Echinodermata

Answer 1

Hint: The physiological mechanism of eliminating metabolic waste from the body is known as excretion. Amino acids, urea, uric acid, carbon dioxide, water, and ammonia are among the excretory chemicals. Amino acids are excreted by certain Molluscs and Echinoderms as waste products from the body. Ammonia is the main excretory substance in animals, and it is made up of proteins found in our food. It is the most toxic nitrogenous waste, and most amphibians and marine animals excrete it by diffusion. Urea is the nitrogenous waste excreted by mammals. It is less toxic and has a lower water solubility. Uric acid is excreted by birds and reptiles as nitrogenous waste.

Complete explanation:
Option A: Solenocytes are Platyhelminthes-specific long, narrow flagellated cells that help in the excretion of nitrogenous wastes. The excretory system of annelids is made up of thin, coiled tubes with glandular walls and abundant blood vessels. Nephridia are these coiled tubular excretory structures.
So, option A is correct.
Option B: One or two unicellular renette glands on the underside of several marine nematodes excrete salt through a pore near the pharynx. These specialised cells have been replaced in most other nematodes by an organ consisting of two parallel ducts linked by a single transverse duct. Nephridia is a nitrogenous waste excretory organ that extracts nitrogenous waste from the body cavity through pores outside the body.
So, option B is incorrect.
Option C: A variety of canals help to disperse both nutrients and gases in cnidarians with thicker mesoglea. Since there is no excretory mechanism or organs, nitrogenous wastes actually diffuse from the animal's cells into the surrounding water or into the gastrovascular cavity. Bojanus organs are excretory glands that act as kidneys in certain Molluscs. In other words, these are metanephridia, which can be found in mollusks such as bivalves. Keber's organ is a type of excretory organ found in some other molluscs.
So, option C is incorrect.
Option D: Bojanus organs are excretory glands that act similarly to kidneys in some Molluscs. In other words, these are metanephridia, which are present in bivalves and other mollusks. Some molluscs include keber's organs, which are excretory organs. Echinoderms do not have main excretory organs and instead expel nitrogenous waste as ammonia through their respiratory system.
So, option D is incorrect.

Hence, Option A is the correct answer.

Note:
The mechanism by which metabolic wastes are expelled from an organism is known as excretion. This work is carried out by the kidneys, lungs, and skin in humans. Carbon dioxide, ammonia (in ammonotelic), urea (in ureotelics), uric acid (in uricotelics), guanine (in Arachnida), and creatine are the major excretory items in animals. Kidneys are found in all vertebrates. Planarians have flame cells and nephridia are present in earthworms. In insects, metabolic waste is excreted through a mechanism involving malpighian tubules. Metabolic waste diffuses through the tubule, which transports the waste to the intestines. Antennal glands or green glands are found on prawns.