Into how many kingdoms, systematics has been divided from time to time?

Explanation

**Step-by-Step Text Solution:**

1. **Introduction to Systematics**: Systematics is the scientific study of the diversity of organisms and their relationships. Over time, various classifications have been proposed to categorize living organisms.

2. **Two Kingdom Classification**: The first system of classification was the two kingdom system, which divided organisms into two kingdoms: Plantae (plants) and Animalia (animals). This classification was proposed by Carl Linnaeus.

3. **Three Kingdom Classification**: The next advancement was the three kingdom classification, which included the original two kingdoms (Plantae and Animalia) and added a third kingdom called Protista. This classification was introduced by Ernst Haeckel.

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