18.01 Classification: The Species Concept
Understanding Species Diversity
- Diversity of Life:
- Cataloging all species.
- Highlights differences within the unity of life.
Species Definitions
- Biological Species Concept (Biospecies):
- Organisms with similar morphology/physiology.
- Can breed to produce fertile offspring.
- Reproductive isolation from other species.
- Morphological Species Concept:
- Based on physical traits (e.g., morphology/anatomy).
- Useful when reproductive data is unavailable.
- Ecological Species Concept:
- Focuses on populations sharing features in the same habitat/time.
Species Discovery & Naming
- Binomial Nomenclature:
- Developed by Linnaeus (18th century).
- Two-part name:
- Genus Name:
- Higher classification rank.
- Includes species sharing many similarities.
- Always capitalized (e.g., Nesomimus).
- Specific Epithet (species name):
- Combined with genus name forms the full species name (e.g., Nesomimus trifasciatus).
- Example: Mockingbird species of Galapagos (Nesomimus genus).
- Abbreviation:
- After first mention: N. trifasciatus.
- Avoid ambiguity if multiple genera share initials.
Key Points About Classification:
- Appearance isn’t always reliable:
- Example: African mouse (placental mammal) vs. Australian antechinus (marsupial), classified in different orders despite similar appearance.
- Uncertain species count:
- Described species: >1.5 million.
- Estimated total: Up to 100 million.
Key Terms
- Biological Species:
- Breed to produce fertile offspring.
- Isolated from other species.
- Morphological Species:
- Distinguished by physical traits.
- Ecological Species:
- Population sharing features in the same habitat/time.
- Population:
- Organisms of the same species in the same place/time, capable of interbreeding.
Figure:
Fig. A+B: Shows deceptive appearances between two mammals classified in different orders (African mouse vs. Australian antechinus).
A) Australian antechinus mouse
b) Southern African Pouched mouse