This stage of animals that can be compared to a colonial protozoan ancestor

Options

A. Blastula
B. Two layered gastrula
C. Three layered gastrula
D. Zygote

Answer

To answer the question regarding which stage of animals can be compared to a colonial protozoan ancestor, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Colonial Protozoans**:
- Colonial protozoans are groups of individual protozoans living together in a colony. They function collectively, resembling a multicellular organism, and exhibit division of labor among the cells.

2. **Identifying Stages of Animal Development**:
- The development of animals includes several key stages:
- Zygote
- Morula
- Blastula
- Gastrula (which can be further divided into two-layered and three-layered gastrula)

3. **Analyzing the Blastula Stage**:
- The blastula is a spherical structure formed after cleavage of the zygote. It consists of a layer of cells (blastoderm) surrounding a fluid-filled cavity (blastocoel).

4. **Understanding Gastrulation**:
- Gastrulation is the process that follows the blastula stage. During this process, cells move inward, leading to the formation of the gastrula.
- The gastrula can be two-layered (with ectoderm and endoderm) or three-layered (adding mesoderm).

5. **Comparing to Colonial Protozoans**:
- The key feature of colonial protozoans is the division of labor among cells. The three-layered gastrula stage, which consists of ectoderm, endoderm, and mesoderm, allows for specialization of cells and functions, similar to how cells in a colonial protozoan work together for the survival of the colony.

6. **Conclusion**:
- Therefore, the stage of animals that can be compared to a colonial protozoan ancestor is the **three-layered gastrula**.

### Final Answer:
- The correct answer is **three-layered gastrula**.