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Q3:
Attempt giving a clear definition of the term species.
Solution :
1. Conceptual Foundation of the Biological Species Concept
In evolutionary biology, the most widely accepted framework for defining a species is the Biological Species Concept (BSC), formalized by Ernst Mayr in 1942. This framework defines a species based on reproductive isolation and genetic cohesion within a population.
2. Formal Definition
A species is defined as a group of organisms that are capable of interbreeding under natural conditions to produce viable, fertile offspring, and which are reproductively isolated from other such groups [Per the Evolutionary Biological Species Concept].
3. Core Analytical Criteria
To qualify as a member of the same species, a population must satisfy three primary logical constraints:
- Interbreeding Potential: Individuals must be able to exchange genetic material through sexual reproduction.
- Natural Context: Breeding must occur under natural, non-forced conditions, excluding laboratory-induced hybrids (e.g., tigons or ligers).
- Biological Fitness of Progeny: The offspring resulting from such interbreeding must themselves be biologically viable (capable of survival) and fertile (capable of reproduction).
4. Visual Representation of Reproductive Isolation
5. Limitations and Nuances
While the BSC is the gold standard for sexual organisms, it is subject to specific scientific limitations:
| Category | Limitation |
|---|---|
| Asexual Organisms | Bacteria, archaea, and some fungi reproduce via binary fission or budding; thus, the "interbreeding" criterion is inapplicable [Per Evolutionary Taxonomy]. |
| Fossil Records | Paleontological evidence cannot verify reproductive compatibility, necessitating the use of the Morphological Species Concept. |
| Hybridization | Some distinct plant species can occasionally cross-pollinate, challenging the absolute nature of reproductive boundaries. |
Final Solution: A species is a fundamental unit of classification consisting of a population or group of populations whose members share a common gene pool, can interbreed under natural conditions, and are reproductively isolated from other populations, resulting in fertile progeny.
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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