Final answer:
The welfare of many dog breeds is often compromised due to selective breeding and inbreeding, leading to health issues and narrowed gene pools.
Step-by-step explanation:
The welfare of many dogs, of numerous breeds, is compromised as a result of selective breeding and/or inbreeding in some cases for a large portion or even all of their lives. Selective breeding has led to the exaggeration of physical traits such as the large heads of English bulldogs that necessitate deliveries by cesarian section, as well as narrowed gene pools that increase proneness to health issues like cancer and hip dysplasia. Inbreeding can exacerbate these issues by increasing the likelihood of hereditary diseases and potentially leading to decreased life spans and increased offspring mortality. Breeders aim to avoid inbreeding by seeking diverse genetic backgrounds to prevent the accumulation of deleterious recessive mutations that can adversely affect animal welfare.