Question

In which of the following animals, Hb (Haemoglobin) is found dissolved in plasma?
A. Planaria
B. Cockroach
C. Sepia
D. Earthworm

Answer 1

Hemoglobin is a protein, which is present in the red blood cells. It usually carries oxygen to the organs of the body and tissues. Meanwhile, it transports carbon dioxide from organs and tissues to the lungs. It is an assembly of four globular protein subunits in most of the vertebrates. Each subunit is made up of protein chains associated with non-protein prosthetic heme groups.

Complete answer:
Option D Earthworm: Earthworm comes under annelids. Annelids contain Hb, the same respiratory pigment, which is also present in humans. Due to Hb only, the blood turns a red color. It is a large extracellular hemoprotein.
Earthworms possess a closed circulatory system. Hb acts as a respiratory pigment, which is dissolved in blood. It aids in the transport of oxygen to the body tissues. The blood cells are nucleated.
Earthworms do not have a proper respiratory system. So Hb is dissolved in the plasma for the diffusion of materials and gases. It does not have lungs and diffusion of carbon dioxide and oxygen occurs through skin.

Hence, Option D is the correct answer.

Additional Information
Option A Planaria : Planaria comes under Platyhelminthes. It lacks circulatory and respiratory systems. Through diffusion in the body wall, entry of oxygen and exit of carbon dioxide takes place. There is absence of Hb.
Hence, Option A is not correct
Option B Cockroach: Blood of cockroaches is colorless. So Hb is not present
So, Option B is not correct
Option C Sepia : Sepia or cuttlefish belongs to the phylum Mollusca. It consists of the respiratory pigment haemocyanin in the blood.
Option C is not correct

Note:
If the Hb test displays lower count of Hb than normal level, then there is lower red blood cell count, a condition called anemia. Low Hb is less than $135$ grams per liter in men and less than $120$ grams per liter. Iron deficiency is a common kind of anemia, where deficiency of iron occurs and the body is not able to make the required Hb. Through eating meat, eggs, dates, figs, fish, green beans, nuts and broccoli, the level of Hb can be raised.