Characteristics of Animals that Swim:
Swimming animals have evolved a variety of adaptations to propel themselves through water. These characteristics can be grouped into:
Body Shape and Structure:
* Streamlined Body: A torpedo-shaped body reduces drag and increases efficiency.
* Fins: Paired pectoral and pelvic fins for maneuvering, and a single dorsal, anal, and tail fin for propulsion.
* Flippers: Broad, flat appendages for powerful strokes (like seals, sea turtles, and penguins).
* Hydrodynamic Body: Smooth, slick skin with minimal protrusions to reduce friction.
* Buoyancy Control: Gas-filled bladders (fish), blubber (whales), and skeletal density adjustments to control depth and effort.
Movement and Propulsion:
* Undulation: Lateral or vertical wave-like motions of the body (fish, eels).
* Fin Propulsion: Strong, coordinated movements of fins to generate thrust (fish, whales).
* Jet Propulsion: Expelling water from the body cavity (squid, jellyfish).
* Flipper Propulsion: Powerful, alternating movements of flippers (seals, sea turtles).
* Wing Propulsion: Alternating downstrokes and upstrokes with wings (penguins, seabirds).
Physiological Adaptations:
* Gills: Specialized respiratory organs for extracting oxygen from water (fish).
* Lungs: Adaptations for holding breath for extended periods (whales, seals).
* Salt Glands: Specialized organs for excreting excess salt from the body (marine mammals, birds).
* Thermoregulation: Insulation (blubber, feathers) and countercurrent heat exchange to maintain body temperature in cold waters.
Examples:
* Fish: Streamlined body, fins, gills, and undulatory movement.
* Whales: Streamlined body, flippers, lungs, and fin propulsion.
* Sea Turtles: Streamlined body, flippers, lungs, and flipper propulsion.
* Penguins: Streamlined body, wings, lungs, and wing propulsion.
* Jellyfish: Bell-shaped body, tentacles, jet propulsion.
Note: These are just some general characteristics. Specific adaptations vary greatly depending on the species, habitat, and swimming style of the animal.