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The most well-studied example is the Spike protein of SARS-CoV-2, which independently evolved at the same positions regardless of the underlying sublineage. [272] The most ominent examples from the pre-Omicron era were E484K and N501Y, while in the Omicron era examples include R493Q, R346X, N444X, L452X, N460X, F486X, and F490X.
While amphibians continued to feed on fish and later insects, reptiles began exploring two new food types, other tetrapods (carnivory), and later, plants (herbivory). Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation (in contrast, a complex set of adaptations was necessary for ...
An affinity between the amphibians and the teleost fish is the multi-folded structure of the teeth and the paired supra-occipital bones at the back of the head, neither of these features being found elsewhere in the animal kingdom. [25] The Permian lepospondyl Diplocaulus was largely aquatic
Food crops; Some aquatic plants are used by humans as a food source. Examples include wild rice , water caltrop (Trapa natans), Chinese water chestnut (Eleocharis dulcis), Indian lotus (Nelumbo nucifera), water spinach (Ipomoea aquatica), prickly waterlily (Euryale ferox), and watercress (Rorippa nasturtium-aquaticum). Bioassessment
Skin breathing, known as cutaneous respiration, is common in fish and amphibians, and occur both in and out of water. In some animals waterproof barriers impede the exchange of gases through the skin. For example, keratin in human skin, the scales of reptiles, and modern proteinaceous fish scales impede the exchange of gases.
The food residue passes into the large intestine where excess water is removed and the wastes are passed out through the cloaca. [77] Although adapted to terrestrial life, frogs resemble freshwater fish in their inability to conserve body water effectively. When they are on land, much water is lost by evaporation from the skin.
Evolutionary theory predicted that since amphibians evolved from fish, an intermediate form should be found in rock dated between 365 and 385 million years ago. Such an intermediate form should have many fish-like characteristics, conserved from 385 million years ago or more, but also have many amphibian characteristics as well.
Several authors have suggested that terrestrial eggs evolved from amphibian eggs laid on land to avoid predation on the eggs and competition from other labyrinthodonts. [62] [63] The amniote egg would necessarily have had to evolve from one with an anamniote structure, as those found in fish and modern amphibians. [59]