Answer:
The answer is False. Although sensitive cells are <u>more abundant</u> in the <u>anterior portion</u> of the annelid´s body, in general, they are arranged in all the segments.
Explanation:
Annelids, such as the earthworm, have a variety of sensory cells:
- <u>Mechanoreceptors</u>, disposed of in groups in <em><u>each segment</u></em> of their body.
- <u>Photoreceptors</u>: Light-sensitive cells. Although they are <em><u>located in the whole </u></em>body, they are <em><u>abundant in anterior and posterior segments</u></em>, concentrated in the intern and dorsal part of the epidermis.
- <u>Humidity receptors</u> are the most sensitive cells and are <u>located in the first segments</u> of the earthworm body
- <u>Chemoreceptors</u>: sensorial cells cumulus forming a prominent tubercle with prolongations that extends through the cuticle. These tubercles form three rings <em><u>in each segment</u></em> but are especially <em><u>abundant in the anterior part</u></em> of the body.
The tegument is very rich in free nervous terminations, which functions might be tactile.
The oncogenesis process is caused by these mutations in the genetic material of normal cells, which alter the normal balance between proliferation and cell death. As a result there is an uncontrolled cell division and an evolutionary process of these cells through natural selection within the organism. Rapid and uncontrolled reproduction of cells can produce benign tumors and some types of these tumors can become malignant, which is what is known as cancer. Benign tumors do not spread to distant parts of the body or invade other tissues, and usually do not pose a threat to life unless they compress vital structures or have some physiological activity (for example, that they are capable of producing a hormone) . Malignant tumors are able to invade other organs, spread to distant places (a process known as metastasis) and become a threat to life.
