In which of the following vertebrate group/groups, heart does not pump oxygenated blood to different parts of the body?(a) Pisces and amphibians(b) Amphibians and reptiles(c) Amphibians only(d) Pisces only

The correct answer is (d) Pisces only.

Here's the step by step explanation:

1. In vertebrates, the heart is responsible for pumping blood throughout the body. This blood can be either oxygenated (carrying oxygen) or deoxygenated (carrying carbon dioxide).

2. In most vertebrates, the heart pumps oxygenated blood. However, there are exceptions.

3. Pisces, or fish, have a two-chambered heart that pumps blood to the gills first. Here, the blood gets oxygenated and then flows to the rest of the body. So, the heart itself does not pump oxygenated blood directly to the body.

4. Amphibians have a three-chambered heart. Two of the chambers, the atria, receive blood (one gets deoxygenated blood from the body, and the other gets oxygenated blood from the lungs or skin). These two types of blood get mixed in the third chamber, the ventricle, and then pumped out to the body. So, the heart in amphibians does pump some oxygenated blood to the body.

5. Reptiles, except for crocodilians, also have a three-chambered heart and the blood gets mixed in the ventricle. However, the mixing is not as thorough as in amphibians, so more oxygenated blood gets pumped to the body.

6. Therefore, among the given options, only in Pisces (fish) does the heart not pump oxygenated blood to different parts of the body.