As a subject matter expert in biology, I can tell you that not all worms have a heart, but many do. The presence and complexity of a heart in worms depend on their classification within the phylum Annelida, which includes various types of segmented worms.

Earthworms, which are a common type of worm, have a simple closed circulatory system with five pairs of aortic arches that function in the distribution of blood. These arches are often referred to as "hearts," but they are not true hearts like those found in vertebrates. Instead, they act as pumps to circulate blood through the body.

Other types of annelids, such as polychaetes, have more complex circulatory systems with a true heart or multiple hearts. For example, some polychaetes have a system with both a single ventricle and multiple atria, which is more similar to the hearts found in fish.

In summary, while not all worms have a heart in the traditional sense, many do possess a circulatory system with structures that serve a similar purpose to a heart.

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2. Earthworms. While it is not technically a ��heart,�� the aortic arch of the earthworm performs a similar function and is commonly referred to as one for the sake of simplicity. An earthworm has five arches/hearts that are segmented and pump blood throughout its body.read more >>