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Age can be determined by counting growth rings in fish scales, otoliths, cross-sections of fin spines for species with thick spines such as triggerfish, or teeth for a few species. Each method has its merits and drawbacks. Fish scales are easiest to obtain, but may be unreliable if scales have fallen off of the fish and new ones grown in their ...
Aristotle (ca. 340 B.C.) may have been the first scientist to speculate on the use of hard parts of fishes to determine age, stating in Historica Animalium that “the age of a scaly fish may be told by the size and hardness of its scales.” [4] However, it was not until the development of the microscope that more detailed studies were performed on the structure of scales. [5]
The implications of this model include a rapid increase in environmental ecologists' understanding of how spatial scales impact species diversity in a certain environment. [ 4 ] Another model is Law and Diekmann's 1996 models on mutualism , which is defined as a relationship between two organisms that benefits both individuals. [ 5 ]
A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages.
Scales usually vary in size, the stouter, larger scales cover parts that are often exposed to physical stress (usually the feet, tail and head), while scales are small around the joints for flexibility. Most snakes have extra broad scales on the belly, each scale covering the belly from side to side.
Fisheries-induced evolution is a function of the fishing-induced genetic drift, and to some extent represent the reduction of genetic diversity within the targeted population. For many exploited population, this reduction in genetic diversity has been predicted to reduce their adaptability to both environmental variability and ecological ...
Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology.Studies in this branch of biology examine such phenomena as adaptation, speciation, and population structure.
The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys.