Lecture on Biological Species Concept and Biodiversity
Introduction
- Biological Species Concept: Defines species as groups of interbreeding organisms that produce fertile offspring.
- Requires sexual reproduction with male and female interaction.
- Not applicable to all organisms.
Asexual Reproduction
- Binary Fission: Asexual reproduction in bacteria.
- No male or female, no genetic mixing.
- Horizontal Gene Transfer: Bacteria can exchange DNA without reproduction.
Challenges in Defining Species
- Chromosome Number: Key in determining fertile offspring.
- Example: Horse (64 chromosomes) + Donkey (62 chromosomes) = Mule (63 chromosomes, infertile).
- Hybrid species often face infertility due to chromosome mismatch.
Classifying Species: Tools and Techniques
Dichotomous Key
- Purpose: Identify and classify organisms based on characteristics.
- Divides traits into two different parts.
- Example: Identifying a housefly by wing characteristics.
- Design: Always have one less step than the total number of organisms.
- Efficient for smaller sets; complex for larger organisms.
Environmental DNA (e-DNA)
- DNA Barcoding: Uses common DNA sections for species identification.
- Environmental DNA: DNA collected from environmental samples (e.g., water).
- Can identify species presence without capturing organisms.
Applications of e-DNA
- Ecosystem Health: Identify indicator species sensitive to pollutants.
- Example: Stonefly nymphs (intolerant to pollution) vs. Tubifex worms (tolerant to pollution).
- Presence/absence can signal ecosystem conditions.
Conclusion
- Comparing Techniques: Understand benefits and limitations of species identification methods (important for exams).
- e-DNA is non-invasive but may not provide population sizes.
This lecture emphasized the complexity of defining species and the tools available for classification and ecosystem monitoring, highlighting the limitations of the biological species concept. Further research and development in genetic methods help overcome these challenges. [Music]