Mechanical waves cannot move without a medium
        
                    
             
        
        
        
According to this dichotomous key, any catfish must be leathery, that is, without scales. They have a flattened body, as in most fish with benthic habits, that is, they live at the bottom of the waters. Coloration varies from bluish gray to yellow. It can reach 1 meter in length and weigh about 5 kilos.
<h3>What is catfish?</h3>
Catfish and catfish are common designations given to fish of the order Siluriformes in most of South America.About 2,200 species of these fish are known, classified into almost 40 families (only two, Ariidae and Plotosidae, have marine species). They are found almost all over the world, but more than half of the known species are native to South America.
With this information, we can conclude that the catfish (Ictaluruspunctatus) is a representative fish of the order Siluriformes, family Ictaluridae, characterized by not having scales.
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The characteristic that can distinguish bacterial cells from cells in the other domains of life is that only bacterial cells have peptidoglycan cell wells.
What is the major difference between a bacterial cell and the cells of other organisms?
Animal and plant cells are different from bacterial cells in a number of ways. One key distinction is that, unlike plant and animal cells, bacterial cells lack internal organelles including mitochondria, chloroplasts, and a nucleus. 
Bacteria can be categorised according to their morphology, such as bacilli (rod-shaped), cocci (sphere-shaped), and spirilli (spirals). In that they have cytoplasm, ribosomes, and a plasma membrane, bacteria resemble eukaryotic cells. A bacterial cell can be distinguished from a eukaryotic cell by its circular nucleoid DNA, absence of membrane-bound organelles, peptidoglycan cell wall, and flagella.
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