Sentence:  In addition , it would be difficult to imagine chronic generalized emphysema occurring in a cow , considering its marked lobular <WSD>development</WSD> but , conversely , not difficult to imagine this occurring in the horse or the dog . 
Meaning of the word marked with <WSD> tags:  (biology) the process of an individual organism growing organically; a purely biological unfolding of events involved in an organism changing gradually from a simple to a more complex level