### Step-by-Step Solution:
1. **Definition of Bone and Cartilage**:
- Bone is a hard, rigid tissue that forms the skeleton of vertebrates.
- Cartilage is a softer, flexible tissue that provides support and cushioning in various parts of the body.
2. **Rigidity**:
- Bone is characterized by its rigidity and strength, making it suitable for structural support.
- Cartilage, on the other hand, is more flexible and less rigid than bone, allowing for movement and flexibility in joints.
3. **Presence in Embryos**:
- Cartilage is more abundant in vertebrate embryos and serves as a precursor to bone in many cases.
- As the embryo develops, much of the cartilage is replaced by bone tissue.
4. **Cellular Composition**:
- Both bone and cartilage contain cells and a ground matrix.
- In cartilage, the cells are known as chondrocytes, while in bone, they are called osteocytes.
5. **Presence of Collagen**:
- Both tissues contain collagen, which is a protein that provides strength and structure.
6. **Vascularization**:
- Both bone and cartilage require a supply of blood vessels and lymph vessels for nourishment and waste removal.
- However, bone is highly vascularized, meaning it has a rich supply of blood vessels, while cartilage has a limited blood supply.
7. **Haversian Canal System**:
- A key difference is the presence of the Haversian canal system in bone, which is not found in cartilage.
- The Haversian canal contains blood vessels (arteries and veins), lymph vessels, and bone cells, facilitating the transport of nutrients and waste.
8. **Conclusion**:
- The primary differences between bone and cartilage can be summarized as follows:
- Bone is hard and rigid, while cartilage is soft and flexible.
- Bone contains a Haversian canal system, whereas cartilage does not.
- Bone is more vascularized compared to cartilage.
