Definition and classification of fins:
Fin refers to a thin and flat structure protruding from both sides of fish, supported by cartilage or hard bone. According to different positions and shapes, fins can be divided into dorsal fin, gluteal fin, caudal fin, ventral fin and pectoral fin.
Function of fin:
Fin is the main tool for fish swimming and has the following functions. Balance: Fins help fish keep balance and keep them in a stable posture in the water, avoiding tilting or tumbling. Propulsion: By swinging and adjusting the angle of fins, fish can push themselves forward. Especially dorsal fin, gluteal fin and caudal fin play an important role in propulsion. Steering: By controlling the movement and angle of fins, fish can change their swimming direction and respond flexibly to water flow and environment.
Structure and characteristics of fins;
Different types of fins are different in structure and characteristics. The dorsal fin and gluteal fin are usually located in the center of the fish's back and abdomen to help the fish maintain balance and propulsion. The caudal fin is usually located at the tail of the body and is the most important propulsion organ, which generates propulsion by swinging. The ventral fin is located in the abdomen of fish and is used for balance and manipulation. Some benthic fish have large ventral fins and can walk underwater. The pectoral fin is located on the side of the fish and is used to balance and adjust the swimming direction.
Morphological adaptation of fins;
According to the different ecological environment and lifestyle of different kinds of fish, the morphological adaptation of fins will be different. For example, fish swimming in the ocean usually have long and flat dorsal fins and anal fins, which provide stronger propulsion. However, fish living in still water such as rivers or lakes may have short fins, which are mainly used for balance and manipulation.
Fins of non-fish animals:
Besides fish, other aquatic animals have similar structures called fins. For example, flippers are tentacle-like structures in some mollusks and invertebrates, which are used for eating, moving or sensing the environment.
Fins and evolution:
Fins play an important role in biological evolution. Through the study of ancient fish, scientists can infer the evolution of fish and reveal the origin of land creatures such as birds and mammals. The constant change and adaptive evolution of fins have contributed to the formation of biodiversity.