1. Breathing:
* Dolphins: Mammals, breathe air through lungs, must surface regularly to breathe.
* Fish: Breathe underwater through gills, extract oxygen from water.
2. Body Structure:
* Dolphins: Streamlined body, horizontal tail flukes for propulsion, possess a blowhole on top of their head for breathing.
* Fish: Variety of body shapes, vertical tail fin for propulsion, use gills located on the sides of their heads to extract oxygen.
3. Reproduction:
* Dolphins: Give birth to live young, nourish their offspring with milk from mammary glands.
* Fish: Lay eggs (most species), fertilization usually external.
4. Warm-Blooded vs. Cold-Blooded:
* Dolphins: Warm-blooded, maintain a constant internal body temperature.
* Fish: Cold-blooded, body temperature fluctuates with the surrounding water.
5. Evolution:
* Dolphins: Evolved from land mammals that returned to the sea.
* Fish: Evolved in the ocean, a much older lineage.
6. Sensory Systems:
* Dolphins: Echolocation, use sound waves to "see" underwater, possess a highly developed sense of hearing.
* Fish: Variety of sensory systems, including lateral line system for sensing vibrations in the water, keen sense of smell in some species.
In summary:
Dolphins are mammals adapted to life in the water, while fish are a distinct group of aquatic vertebrates that evolved and developed entirely within the ocean environment. Their differences stem from fundamental evolutionary pathways, breathing mechanisms, and other biological adaptations.