Evolution of Fishes
Fishes, as the first vertebrates, emerged in the evolutionary timeline around 500 million years ago (mya) during the Cambrian period. This period marked significant evolutionary advancements leading to the diversification of life forms.
Key Characteristics of Early Fishes
- Anatomy: Early fishes possessed simple body structures, primarily characterized by soft bodies and cartilaginous skeletons.
- Adaptations: They developed gills for respiration and fins for movement, crucial for survival in aquatic environments.
Transition to Reptiles
- Evolutionary Link: Fishes are considered the ancestors of all terrestrial vertebrates, including reptiles, amphibians, and mammals.
- Key Evolutionary Changes:
- Development of limbs from fins facilitated the transition from water to land.
- Evolution of lungs allowed for breathing air, leading to the rise of amphibians.
Importance of Fishes in Evolution
- Biodiversity: The emergence of fishes laid the groundwork for the vast biodiversity we see today in aquatic ecosystems.
- Ecosystem Role: Fishes play a vital role in food chains and nutrient cycling within their habitats.
Conclusion
The evolution of fishes around 500 mya was a crucial step in the history of life on Earth, setting the stage for the eventual rise of reptiles and other terrestrial vertebrates. Their adaptations and evolutionary significance highlight the interconnectedness of life and the ongoing process of evolution.

200 mya . NCERT (12) page 140