It is true that on the Galapagos islands Darwin observed tortoises with a dome and saddle shaped shells, you can see both in attached image.
Darwin observed that Galapagos Tortoises had the shells with different shapes depending on the Island they live, For example: The tortoises with saddle shaped shells were able to reach up to eat leaves of plants while the tortoises with dome shaped shells would not reach up and they would eat food from on ground sources. This made him think that the differences in tortoise shell is also a strong evidence that indicates that how tortoises have adapted themselves to better get their food as per the available resources and how they have evolved from same ancestral specie into two different species. This point also helped him in proposing the theory of evolution by natural selection.
Archaean cell wall don't have peptidoglycan, yet they may have <em>, polysaccharides, glycoproteins, or protein-based cell dividers </em>
Bacterial cell walls are made of peptidoglycan (likewise called murein), which is produced using polysaccharide chains cross-connected by abnormal peptides containing D-amino acids
Puppies from the same litter commonly share 50% of their genes (on average.) Each litter mate randomly inherits 50% of its genes from his father and the other 50% from his mother. The only thing here is that they do not necessarily the same 50% from each