Great question! The cell type I work with (chondrocytes) are really similar between different species. The tissue they make is very similar between species and that is why they are a great model for looking at human joint tissues. In terms of the basic elements of the cell, all animal cells are very similar, i.e. they do not have a cell wall and they have a nucleus. Dogs have different features to us because they have adapted and evolved to have the features they have. For example, when a puppy is developing, cells receive signals to move to one end of the puppy and develop the tail. A long time ago our ancestors had tails but over millions of years we have lost that feature because we don’t need it to survive.