1.Béchamel Sauce-is probably the simplest of the mother sauces because it doesn't require making stock.
2.Velouté Sauce-is another relatively simple mother sauce, made by thickening white stock with a roux and then simmering it for a while.
3. Espagnole Sauce-also sometimes called Brown Sauce, is a slightly more complex mother sauce. Espagnole is made by thickening brown stock with a roux.
4. Hollandaise Sauce- is unlike the mother sauces we've mentioned so far, due to a liquid and a thickening agent, plus flavorings. Hollandaise is a tangy, buttery sauce made by slowly whisking clarified butter into warm egg yolks.
5. Classic Tomate Sauce- is the classic Tomate Sauce. This sauce resembles the traditional tomato sauce that we might use on pasta and pizza, but it's got much more flavor and requires a few more steps to make.
They are considered as Homologous Structures.
Limbs of a frog, whale, horse, lion, human, bat and bird are the same since they are homologous structures.What are homologous structures?
These are body parts or organs from different organisms which are of the same characteristics. These are body parts with the same anatomical or structural features but not necessarily of the same function. This homology indicates that they are from a common ancestor.
As a conclusion, the above mentioned limbs are considered to be of the same ancestor that is why they are the same.
To read more: