During development mammalian heart is initially two chambered, then three chambered and finally four chambered. It is explained by

Options

A. Biogenetic law of Haeckel
B. Lamarckism
C. Hardy weinberg's law
D. Neo Darwinism

Answer

To solve the question regarding the development of the mammalian heart from two chambers to three chambers and finally to four chambers, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Heart Development**:
- The mammalian heart undergoes a developmental process where it starts as a simple two-chambered structure, evolves into a three-chambered heart, and ultimately develops into a four-chambered heart. This progression is critical in understanding the evolution of the heart in mammals.

2. **Exploring the Options**:
- The question provides four options:
1. Biogenetic law of Heckel
2. Lamarckism
3. Hardy-Winkler's law
4. Neo-Darwinism

3. **Identifying the Correct Concept**:
- The correct explanation for the observed developmental stages of the heart is related to the **biogenetic law of Heckel**, which states that "ontogeny recapitulates phylogeny." This means that the development of an individual organism (ontogeny) reflects the evolutionary history (phylogeny) of that organism's species.

4. **Applying the Biogenetic Law**:
- According to this law, during embryonic development, the mammalian heart exhibits stages that resemble the heart structures of ancestral forms. Initially, the heart is two-chambered (similar to fish), then it becomes three-chambered (similar to amphibians), and finally, it develops into a four-chambered structure (characteristic of mammals).

5. **Conclusion**:
- Therefore, the correct answer to the question is the **biogenetic law of Heckel**, as it explains the sequential development of the heart from two chambers to three and finally to four chambers.

### Final Answer:
The development of the mammalian heart from two-chambered to three-chambered and finally to four-chambered is explained by the **biogenetic law of Heckel**.

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