Convergent evolution in my understanding is the independent evolution of similar features in species of different lineages.
For breaking down lactose
Carbon dioxide is released during cellular respiration.
The epidermis is the outermost layer of skin and is app. .005-1.5mm thick. it is made up of several different types of cells with keratinocutes being the most abundant.
The dermis is the second layer of skin and is app. .3-3.0mm thick. And basically consists of connective tissue.
