Phylogenetic classification is based on

Options

A. Utilitarian system
B. Habits
C. Overall similarities
D. Common evolutionary descent.

Answer

### Step-by-Step Solution:

1. **Understanding Phylogenetic Classification**:
- Phylogenetic classification is a method of classifying organisms based on their evolutionary relationships. It emphasizes the importance of common ancestry among species.

2. **Defining Key Terms**:
- **Common Ancestor**: This refers to a species from which two or more species have evolved. Phylogenetic classification relies on identifying these common ancestors to establish relationships among different organisms.

3. **Evolutionary History**:
- The classification is based on the evolutionary history or ancestry of organisms. This means that organisms are grouped together if they share a recent common ancestor.

4. **Speciation Events**:
- Phylogenetic classification considers the events of speciation, where one species diverges into two or more species. This divergence is a key factor in understanding the evolutionary relationships.

5. **Evaluating Options**:
- **Option 1: Utilitarian System**: This is not related to phylogenetic classification.
- **Option 2: Habitat**: While organisms may share habitats, this does not determine their evolutionary relationships.
- **Option 3: Overall Similarities**: Similarities in morphology or chemical composition do not necessarily indicate a common evolutionary path.
- **Option 4: Common Evolutionary Descent**: This option aligns with the definition of phylogenetic classification, as it is fundamentally based on the concept of common ancestry.

6. **Conclusion**:
- The correct answer is **common evolutionary descent**, as phylogenetic classification is fundamentally based on the evolutionary history and relationships of organisms.