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Q3:
Attempt giving a clear definition of the term species.
Solution :
1. Conceptual Foundation of the Biological Species Concept
The term species is fundamentally defined within the framework of the Biological Species Concept (BSC), primarily attributed to Ernst Mayr. According to this definition, a species represents the largest pool of individuals capable of exchanging genetic material through sexual reproduction under natural conditions.
2. Formal Definition
A species is defined as a group of individuals that are morphologically similar, can interbreed under natural conditions, and produce fertile offspring, while being reproductively isolated from other such groups [Per the Biological Species Concept].
3. Granular Criteria for Species Identification
- Reproductive Compatibility: Members must possess the biological potential to interbreed ($A \times B \rightarrow \text{Fertile Offspring}$).
- Natural Environment: Interbreeding must occur under non-experimental, natural conditions. Captive breeding (e.g., in zoos) does not strictly define a species if such mating does not occur in the wild.
- Reproductive Isolation: The group must remain distinct from other groups due to pre-zygotic or post-zygotic barriers (e.g., ethological, temporal, mechanical, or hybrid inviability) [Ref: Evolutionary Biology, Speciation Mechanisms].
4. Comparative Analysis of Limitations
While the BSC is the gold standard for sexual organisms, it possesses specific analytical limitations when applied to the entirety of the biosphere:
| Category | Constraint | Applicability |
|---|---|---|
| Asexual Organisms | Lack of interbreeding mechanics | Not applicable (defined by clonal lineage) |
| Extinct Taxa | Reproductive data unavailable | Morphological/Phylogenetic definition required |
| Hybridization | Gene flow between distinct groups | Challenges rigid boundaries |
5. Illustrative Representation of Reproductive Isolation
6. Synthetic Conclusion
In modern evolutionary synthesis, a species is not merely a static category but a dynamic, evolutionary lineage. It functions as the basic unit of classification and the fundamental level at which evolutionary processes, such as natural selection and genetic drift, operate [Ref: Modern Synthesis of Evolution].
Final Solution: A species is a group of organisms that are capable of interbreeding under natural conditions to produce fertile offspring and are reproductively isolated from other such groups.
More Questions from Class 12 Biology Evolution EXERCISES
- Q1: Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
- Q1: Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
- Q2: Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
- Q2: Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
- Q3: Attempt giving a clear definition of the term species.
- Q4: Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)
- Q4: Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)
- Q5: Find out through internet and popular science articles whether animals other than man has self-consciousness.
- Q5: Find out through internet and popular science articles whether animals other than man has self-consciousness.
- Q6: List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
- Q6: List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
- Q7: Practise drawing various animals and plants.
- Q7: Practise drawing various animals and plants.
- Q8: Describe one example of adaptive radiation.
- Q8: Describe one example of adaptive radiation.
- Q9: Can we call human evolution as adaptive radiation?
- Q9: Can we call human evolution as adaptive radiation?
- Q10: Using various resources such as your school Library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal, say horse.
- Q10: Using various resources such as your school Library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal, say horse.
CBSE Solutions for Class 12 Biology Evolution
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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