In which of the following animals does a 13 chambered tubular heart occur, as commonly described in basic zoology textbooks?

Introduction / Context:
Different animal groups show great variety in the structure of their circulatory systems and hearts. Some have simple pulsating vessels, while others have multi chambered hearts. Textbook zoology often highlights the fact that a 13 chambered tubular heart is found in a specific insect, making this a favourite question in exams. This question asks which of the listed animals has such a 13 chambered heart.

Given Data / Assumptions:

• The focus is on the presence of a 13 chambered heart.
• The options list various invertebrates, including leech, earthworm, snail, and cockroach.
• We assume knowledge of basic invertebrate anatomy.
• We also assume that this is a standard fact presented in school level zoology.

Concept / Approach:
Cockroach, an insect belonging to class Insecta, has a dorsal tubular heart that is divided into 13 chambers, each with ostia that allow haemolymph to enter. This structure is characteristic and is repeatedly mentioned in descriptions of cockroach anatomy. Other animals in the options, such as earthworm and snail, have different types of circulatory systems and do not possess a 13 chambered heart. The correct approach is to recall that the phrase 13 chambered heart is closely associated with cockroach in exam oriented material.

Step-by-Step Solution:
Step 1: Recall that the cockroach has a dorsal heart with multiple chambers arranged in a row. Step 2: Remember that the number of chambers in the cockroach heart is commonly described as 13. Step 3: Compare this information with the animals listed in the options. Step 4: Note that leech and earthworm have different circulatory arrangements and are not associated with a 13 chambered heart. Step 5: Select cockroach as the animal with a 13 chambered heart.

Verification / Alternative check:
To verify, we can recall typical exam questions in zoology that directly state that cockroach has a 13 chambered tubular heart with ostia. Earthworms are described as having several pairs of arches sometimes called hearts, but they are not counted as 13 heart chambers in the same way. Snails have a simpler heart with fewer chambers. Therefore, the standard textbook association of 13 chambered heart with cockroach confirms that cockroach is the correct answer.

Why Other Options Are Wrong:
Option A: Leech has a different type of circulatory system and is not described as having a 13 chambered tubular heart. Option B: Earthworm has several pairs of muscular blood vessels sometimes called hearts, but it is not characterised as having exactly 13 chambers in a single tubular heart. Option C: Snail, a mollusc, has a heart with a smaller number of chambers, usually described as two or three, not 13. Option E: Prawn, a crustacean, has a single chambered heart with ostia and does not match the description of a 13 chambered tubular heart.

Common Pitfalls:
Students sometimes confuse the multiple hearts or heart like structures in earthworms with the 13 chambered heart of cockroach. Another mistake is to assume that larger or more complex looking animals have more heart chambers. Instead, the phrase 13 chambered tubular heart specifically appears in the standard description of cockroach anatomy. Memorising this association directly helps answer such questions quickly and accurately.

Final Answer:
A 13 chambered tubular heart occurs in the cockroach.