Class 11 Biology - The Living World

Activities

Activity 1.1: Understanding the Concept of Species

Aim/Objective: To explore the different biological meanings and criteria used to define a 'species'.

Materials Required:

• Biology textbooks
• Internet access or library resources
• Notebook and pen

Procedure:

1. Research the definition of "species" from different biological perspectives (Biological Species Concept, Morphological Species Concept, Phylogenetic Species Concept).
2. Compare how a species is defined for higher plants/animals versus how it is defined for asexual organisms like bacteria.
3. Discuss with a teacher or peer the limitations of each definition (e.g., hybridisation, fossil records).

Observation:

• Higher organisms are often defined by their ability to interbreed and produce fertile offspring (Biological Species Concept).
• Bacteria are often defined by biochemical and genetic similarities because they do not reproduce sexually.

Explanation:

• A 'species' is the fundamental unit of classification. While the biological species concept (Mayr) is widely accepted for sexually reproducing organisms, it does not apply to asexual organisms or extinct species. Modern taxonomy increasingly uses DNA sequencing (Phylogenetic Species Concept) to establish species boundaries more precisely.

Conclusion:

• The concept of species is dynamic and depends on the biological nature of the organism being classified.