Two different species cannot live for long duration in the same niche or habitat. This law is

Options

A. Allen's law.
B. Malthus theory
C. Weismann's theory
D. Competition -exclusion principle.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question states that two different species cannot coexist for a long duration in the same niche or habitat. This concept is fundamental in ecology and relates to how species interact with each other and their environment.

2. **Identifying the Options**: The question likely provides multiple options, including different ecological laws or principles. We need to evaluate these options to find the correct one that describes the situation where two species cannot coexist in the same niche.

3. **Evaluating Allen's Law**: Allen's Law (or Allen's Rule) describes how animal appendages vary with climate. It states that animals in colder climates tend to have shorter appendages, while those in warmer climates have longer appendages. This law does not address species competition in the same niche, so it is not the correct answer.

4. **Evaluating Malthus's Theory**: Malthus's theory discusses population growth and the limits imposed by food resources. It suggests that populations cannot grow exponentially due to resource limitations. However, it does not specifically address the coexistence of species in the same niche, so it is also not the correct answer.

5. **Evaluating Weismann's Theory**: Weismann's theory, known as the germ plasm theory, focuses on genetic inheritance and how genes are passed to the next generation. It does not relate to species competition or niche occupation, making it an incorrect option as well.

6. **Identifying the Correct Principle**: The only remaining option is the Competitive Exclusion Principle, also known as Gauss's Law. This principle states that two species competing for the same resources cannot coexist indefinitely in the same niche. One species will outcompete the other, leading to the exclusion of the less competitive species.

7. **Conclusion**: Therefore, the correct answer to the question is the Competitive Exclusion Principle, also referred to as Gauss's Law.

**Final Answer**: The law that states two different species cannot live for long duration in the same niche or habitat is the Competitive Exclusion Principle (Gauss's Law).

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