Part 1

The blue whale (Balaenoptera musculus) is the largest animal to have ever lived, reaching lengths of up to 30 meters and weighing as much as 180 tonnes. Despite their massive size, blue whales share many anatomical features with other mammals, though these are adapted to a fully aquatic life. Their streamlined bodies help reduce drag as they swim through the ocean, and they are powered by a strong muscular tail called fluke, which moves up and down to propel them forward. The pectoral fins, which are actually modified forelimbs, help with steering and balance. Each pectoral fin contains bones that are homologous to the arm bones in land mammals, including a humerus, radius, and ulna. Unlike fish, blue whales do not have a dorsal fin along their entire back, but rather a small triangular one located near the tail.

Additional limb-like structures can also be found in other parts of the whale's anatomy. Behind the pectoral fins, blue whales have vestigial pelvic bones—remnants of the hind limbs their land-dwelling ancestors once used. Though these bones are no longer connected to the spine or visible from the outside, they provide insight into the species' evolutionary history. Another significant body part is the blowhole, located on top of the head, which functions as a modified nasal passage through which whales breathe. Though not a limb in the traditional sense, the blowhole is crucial to their survival and is adapted for life at sea. Together, these body parts illustrate how the blue whale's anatomy is a blend of ancient traits and specialized adaptations, enabling it to thrive as a giant of the deep.

In addition to these, blue whales also possess finger bones within their flippers, which are another remnant of their terrestrial ancestry. The phalanges are hidden beneath layers of muscle and skin but are structurally similar to the digits found in the hands of land mammals. While these bones are no longer used for grasping or manipulation, they provide support and flexibility to the flippers, enhancing the whale’s maneuverability in water. The presence of these digit-like structures further highlights the evolutionary journey from land to sea and underscores the complexity of whale anatomy.

Part 2

Hot air balloons are fascinating flying machines that operate based on simple principles of physics. At the heart of a hot air balloon is the envelope, the large, colorful fabric portion that holds the heated air. Made from lightweight, heat-resistant materials like nylon or polyester, the envelope is designed to trap hot air, which is less dense than the cooler air outside. As the air inside the envelope is heated, the entire balloon becomes buoyant and begins to rise. The size and shape of the envelope directly affect how much lift the balloon can generate.

Beneath the envelope is the burner, a crucial component that heats the air to make flight possible. Fueled typically by propane, the burner creates an open flame that shoots upward into the mouth of the envelope. Pilots control the altitude of the balloon by adjusting the intensity and duration of the flame. Directly attached to the burner is the fuel tank, which stores the propane in liquid form. These tanks are often made of lightweight metal and must be handled with care to ensure a safe and efficient flight.

At the bottom of the balloon is the basket, where the pilot and passengers stand during flight. Usually made from woven wicker, the basket is strong yet flexible, helping absorb the shock of landing. It is securely connected to the envelope and burner by sturdy cables and supports. Another important part is the parachute valve, located at the top of the envelope. This is a circular panel that can be opened by the pilot using a cord, allowing hot air to escape and enabling the balloon to descend gradually.