Which of the following is not example of adaptive radiation ?

Options

A. Darwin finches
B. Australian marsupials
C. Cichlid fishes
D. All of the above

Answer

To solve the question "Which of the following is not an example of adaptive radiation?", we will analyze the provided options and determine which one does not fit the definition of adaptive radiation.

### Step-by-Step Solution:

1. **Understanding Adaptive Radiation**:
- Adaptive radiation is an evolutionary process where organisms diversify rapidly into a variety of forms to adapt to different environments, often following the availability of new habitats or resources.

2. **Analyzing the Options**:
- **Option 1: Darwin Finches**:
- Darwin finches are a classic example of adaptive radiation. They evolved from a common ancestor into various species with different beak shapes and sizes to exploit different food sources (seeds, insects, etc.) in the Galápagos Islands.
- **Option 2: Australian Marsupials**:
- Australian marsupials (like kangaroos, koalas, and wombats) also exemplify adaptive radiation. They evolved from common ancestors and adapted to various ecological niches in Australia.
- **Option 3: Cichlid Fishes**:
- Cichlid fishes in Lake Victoria are known for their diversity, but the introduction of the Nile perch led to the extinction of many cichlid species. This situation is more about biodiversity loss due to invasive species rather than adaptive radiation.
- **Option 4: (Not provided in the transcript)**:
- Since the transcript does not mention a fourth option, we will focus on the three analyzed.

3. **Conclusion**:
- Based on the analysis, both Darwin finches and Australian marsupials are clear examples of adaptive radiation. However, the cichlid fishes in Lake Victoria represent a case of biodiversity loss due to the introduction of an invasive species, rather than adaptive radiation.

Therefore, the correct answer is **Option 3: Cichlid Fishes**.