The common bone structure that is shared in the forelimbs of the lobe fin fish and amphibians are the humerus, radius, ulna, and finger bones. Tetrapods are related by the presence of the named bones. Tetrapods includes all limbed vertebrates constituting the classes Amphibian, Reptilia, Aves, Mammalia.
Answer:
The correct answer is option A, that is, keratin.
Explanation:
Keratin refers to a protein that belongs to one of the families of fibrous structural proteins. It is the essential structural substance that forms nails, hair, horns, feathers, external layer of the skin, and hooves. It is the protein, which safeguards epithelial cells from stress or destruction. Keratin is tremendously insoluble in organic solvents and water.
Gymnosperms are no longer restricted to moist environments, as are ferns and mosses because they have evolved to produce non-flagellated pollens that do not require water or moisture to reach the egg whereas ferns and mosses have flagellated sperm that needs moisture to swim towards the egg.
Another major evolutionary adaption in gymnosperms is the production of seeds instead of spores since seeds contain their own nutrition in the form of endosperm, seeds can travel large distances through wind or animals and can germinate when they find suitable conditions. Seeds can remain dormant for several years whereas spores have a shorter lifespan.
To learn more about endosperm here
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