The term “phylum” was coined in 1866 by Ernst Heinrich Phillipp August Haeckel. He was German zoologist, naturalist, philosopher, etc., He was Award-winning in Linnean Medal in 1894, Darwin – Wallace Medal in 1908.

Explanation:

The term "phylum" was given by Cuvier, who is considered the father of comparative anatomy and vertebrate paleontology. He introduced the concept of phylum as a way to classify and categorize organisms based on their overall body plan and structural characteristics.

According to Cuvier, organisms within a phylum share fundamental similarities in their body organization and structure, which distinguishes them from organisms in other phyla. This classification system helps in organizing and understanding the vast diversity of animals on Earth.

Significance of the Term "Phylum":
The introduction of the term "phylum" revolutionized the field of biology and taxonomy by providing a hierarchical framework for classifying and studying organisms. The concept of phylum allows scientists to group organisms based on their evolutionary relationships and shared characteristics.

Other Options:
- Haeckel: Ernst Haeckel was a prominent biologist and philosopher who coined the term "ecology" and proposed the concept of recapitulation, but he did not introduce the term "phylum."
- Theophrastus: Theophrastus was an ancient Greek philosopher and scientist who contributed to the field of botany, but he did not introduce the term "phylum."
- Linnaeus: Carl Linnaeus, also known as Carolus Linnaeus, is considered the father of modern taxonomy. He developed the binomial nomenclature system and introduced the concept of hierarchy in classification, but he did not specifically introduce the term "phylum."

Therefore, the correct answer is option A, Cuvier, who introduced the term "phylum" in the field of biology.