Which protozoan resembles the ancestral form from which the plants and animals evolved ?

Options

A. Amoeba
B. Paramecium
C. Euglena
D. Plasmodium

Answer

**Step-by-Step Solution:**

1. **Identify the Protozoan**: The question asks for a protozoan that resembles the ancestral form from which plants and animals evolved. The protozoan in question is Euglena.

2. **Describe the Structure of Euglena**: Euglena has a unique structure that includes two flagella—one long and one short. This structure aids in its movement.

3. **Explain the Photosynthetic Ability**: Euglena can perform photosynthesis when exposed to sunlight. This means it can produce its own food using sunlight, similar to plants (autotrophic behavior).

4. **Discuss Heterotrophic Behavior**: In the absence of sunlight, Euglena can switch to a heterotrophic mode of nutrition, feeding on small protozoans or other organisms. This behavior is similar to animals.

5. **Conclude the Evolutionary Significance**: Because Euglena exhibits characteristics of both plants (through photosynthesis) and animals (through heterotrophy), it is considered a representative of the ancestral form from which both plants and animals evolved.

**Final Answer**: The protozoan that resembles the ancestral form from which plants and animals evolved is **Euglena**.

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