Over 2/3 of all named species on earth belong to -

Options

A. Arthropoda
B. Annelida
C. Chordata
D. Flatworms

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which phylum contains over 2/3 of all named species on Earth. This means we need to identify the phylum that has the highest number of species.

2. **Analyzing the Options**: The options provided are:
- A) Arthropoda
- B) Annelida
- C) Chordata
- D) Flatworms

3. **Identifying the Largest Phylum**: Among the options, we need to determine which phylum is the largest in terms of species diversity.
- Arthropoda is known to be the largest phylum in the animal kingdom, comprising a vast number of species, primarily insects.

4. **Species Count in Arthropoda**: It is estimated that there are approximately 900,000 species of arthropods, which includes insects, arachnids, and crustaceans. This number represents a significant portion of all named species on Earth.

5. **Comparing with Other Phyla**:
- Annelida (segmented worms) and Flatworms (Platyhelminthes) have far fewer species compared to Arthropoda.
- Chordata (which includes vertebrates) also has a lower number of species compared to Arthropoda.

6. **Conclusion**: Based on the analysis, it is clear that the phylum that contains over 2/3 of all named species on Earth is Arthropoda.

**Final Answer**: A) Arthropoda

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