(a) “Blood circulation in fishes is different from the blood circulation in human beings”. Justify the statement.
In fishes, blood circulation is single circulation.
- The heart has two chambers: one atrium and one ventricle.
- Blood flows: Heart → Gills (for oxygenation) → Body → Back to Heart
- Blood passes through the heart only once in a complete cycle.
In contrast, in human beings, blood circulation is double circulation:
- The heart has four chambers: two atria and two ventricles.
- Blood flows through the heart twice in each cycle – once for oxygenation and once for distribution.
- This provides efficient separation of oxygenated and deoxygenated blood, essential for warm-blooded animals with high energy needs.
(b) Describe “blood circulation” in human beings.
Humans have a double circulation system:
- Pulmonary circulation – Deoxygenated blood from the right side of the heart is pumped to the lungs for oxygenation.
- Systemic circulation – Oxygenated blood from the left side of the heart is pumped to all parts of the body.
The process:
- Right atrium receives deoxygenated blood from the body.
- It flows into the right ventricle, which pumps it to the lungs via the pulmonary artery.
- In the lungs, blood becomes oxygenated and returns to the left atrium via the pulmonary veins.
- Then it enters the left ventricle, which pumps it through the aorta to the rest of the body.
