Question

Provide appropriate technical terms in the space provided
(A) Blood filled cavity in Arthropods_________
(B) Free floating form of cnidaria__________
(C) Stinging organ of jelly fishes__________
(D) Lateral appendages in aquatic Annelids___________

Answer 1

The organs have their specific function to perform in different organisms. They are specialized structures that help animals in many ways like protection, anchorage, protection as well as locomotion. They are present in some species only.

Complete answer:
Let us answer the above questions:
A. Haemocoel is the blood-fluid cavity in the arthropods that contains hemolymph. The body cavity is reduced and is majorly filled with blood which is referred to as a haemocoel. These animals have a cavity that is filled with blood and organs are suspended in this cavity. The organs do not have a specific blood supply but are suspended in the blood and receive nutrients as the "blood washes'' the organs. The haemocoel can act as a hydrostatic skeleton and it functions as the circulatory system in insects like grasshoppers.
B. Medusa is a form in Cnidaria in which the body is shaped like an umbrella and they can float freely in sea water. The upper surface is called the exumbrella and the lower surface is called the subumbrella. Mouth is present in the lower surface which is usually partially closed by a membrane extending inwards from the margin.
C. Nematocysts are the capsules of specialized cells in cnidaria that act as a paralyzing sting. They are minute, elongated or spherical capsules that occurs on the body surface. They are produced in a special cell called as cnidoblast and contains a coiled, hollow, barbed thread which quickly turns outward from the capsule. When stimulated by a chemical, a lidlike structure comes and the thread everts explosively with a twisting motion. The barb enter the foreign particle and if toxin is present it passes through the hollow thread thus paralysing the prey. The stringing thread of some nematoytes ensure small prey by wrapping them around.
D. Parapodia are the paired, unjointed lateral outgrowths that are present in the annelids. They are fundamental organs of location used for both creeping and swimming. They are highly vascularized and thus assist the function of respiration. They vary greatly in size and form, reflecting their variety of functions such as gas exchange, anchorage, protection and locomotion.

Note:
These structures are unique in their own ways. Haemocoel present in arthropods has a major role of protection of organs, medusa being a form of cnidaria is a free floating form that is produced by polyp asexually as seen in Obelia. Nematocytes are a specialised feature of cnidaria that helps to capture prey whereas parapodia are fundamental organs of annelids that have a major role in creeping and walking.