Various taxonomic categories are

Options

A. Mere morphological aggregates
B. Distinct biological entities
C. International codes used for nomenclature
D. Collection of organisms on structural similarities only

Answer

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

1. **Understanding Taxonomy**: Taxonomy is the science of classification of living organisms. It involves organizing species into hierarchical categories based on shared characteristics and relationships.

2. **Taxonomic Hierarchy**: The taxonomic hierarchy consists of several ranks, each representing a level of classification. The main taxonomic categories, from the broadest to the most specific, are:
- **Kingdom**: The highest taxonomic rank, which groups organisms based on fundamental similarities. Examples include Kingdom Animalia (animals) and Kingdom Plantae (plants).
- **Phylum**: A rank below kingdom, which groups organisms based on major body plans and structural features. For example, Phylum Chordata includes animals with a notochord.
- **Class**: A rank below phylum that further divides organisms based on more specific characteristics.
- **Order**: A rank below class that groups organisms that share even more specific traits.
- **Family**: A rank below order that includes closely related organisms.
- **Genus**: A rank below family that groups species that are very closely related and share a common ancestor.
- **Species**: The most specific rank, representing a group of individuals that can interbreed and produce fertile offspring.

3. **Distinct Biological Entities**: Each taxonomic category represents distinct biological entities. For instance, species are fundamentally different from genera, families, and so on. This means that organisms classified under different categories (like species and genus) are independent of each other in terms of their classification.

4. **Morphological and Internal Characters**: The classification is based not only on external morphological traits but also on internal characteristics. This comprehensive approach ensures that organisms are grouped more accurately according to their evolutionary relationships.

5. **Nomenclature**: The international code of nomenclature governs the naming of organisms, ensuring that each species has a unique and universally accepted name, typically consisting of the genus name followed by the species name (binomial nomenclature).