The animals that lack blood are primarily those without a circulatory system, meaning they don't have a heart or vessels to pump blood around their body. These animals instead rely on diffusion to transport nutrients and oxygen.
Animals Without Blood:
| Animal Group | Examples | Why They Lack Blood |
|---|---|---|
| Flatworms | Planarians, tapeworms | Their body cavity has no lining or fluid. They obtain nutrients and oxygen directly from the water. |
| Nematodes | Roundworms | They lack a circulatory system and rely on diffusion. Similar to flatworms, they don't have blood for transporting nutrients and oxygen. |
| Cnidarians | Jellyfish, sea anemones, corals | They also lack a true circulatory system and thus lack blood. They obtain nutrients and oxygen directly from the water due to their simple body structures. |
Why These Animals Don't Need Blood
- Simple Body Structure: These animals are typically small and have simple body plans, allowing for direct exchange of substances with their environment.
- Diffusion: They rely on diffusion where molecules move from an area of high concentration to low concentration to transport nutrients and oxygen.
- Aquatic Lifestyle: Many of these animals live in aquatic environments which aids in the efficient diffusion of gases and nutrients.
In summary, flatworms, nematodes, and cnidarians (like jellyfish, sea anemones, and corals) are among the animals that do not have blood due to their lack of a circulatory system. They rely on other means for transporting nutrients and gases.
