Which organism behaves like plants in the presence of light and absence of organic food, but in reverse conditions behaves like animals?

Options

A. Archaebacteria
B. Euglena
C. Nostoc
D. Paramecium

Answer

To solve the question, we need to identify the organism that exhibits both plant-like and animal-like behaviors depending on environmental conditions. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Question
The question asks for an organism that behaves like a plant when light is present and organic food is absent, and behaves like an animal under reverse conditions (absence of light and presence of organic food).

### Step 2: Analyze the Options
1. **Archaebacteria**: These are a group of microorganisms that can be autotrophic (make their own food) or heterotrophic (consume organic material). However, they do not specifically fit the criteria of switching behaviors based on light and food availability.

2. **Euglena**: This is a unicellular organism that can photosynthesize in the presence of light (like plants) and can also absorb organic nutrients when light is not available (like animals). This dual capability makes it a strong candidate.

3. **Nostoc**: This is a genus of cyanobacteria that primarily performs photosynthesis and is known for nitrogen fixation. It does not exhibit animal-like behavior, so it does not fit the criteria.

4. **Paramecium**: This is a ciliate protozoan that is strictly heterotrophic and does not perform photosynthesis. Therefore, it does not meet the requirements of the question.

### Step 3: Conclusion
After analyzing the options, **Euglena** is the only organism that behaves like a plant in the presence of light and organic food absence (through photosynthesis) and behaves like an animal in the absence of light (by consuming organic matter). Therefore, the correct answer is **Euglena**.

### Final Answer
**Euglena**

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