Enumerate the criteria used by Whittaker (1969) for classification of organisms.

Explanation

**Step-by-Step Solution:**

1. **Introduction to Whittaker's Classification**: In 1969, R.H. Whittaker proposed a five-kingdom classification system for organisms. This system was based on several criteria that helped in categorizing living organisms into distinct groups.

2. **Criteria for Classification**:
- **Mode of Nutrition**: Organisms can be classified based on how they obtain their food. This includes autotrophic organisms (which produce their own food) and heterotrophic organisms (which consume other organisms for energy).

- **Cell Structure**: The classification also considers whether the organisms are prokaryotic (lacking a true nucleus, e.g., bacteria) or eukaryotic (having a true nucleus, e.g., plants and animals).
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