First and second generation pesticides differ vastly in terms of their contents and effects.
First generation pesticides were used in early 20th century up until the 1940's and they consisted chemicals such as mercury and lead which were not biodegradable and they started adding up in the soil until it was not fertile anymore. Second generation pesticides were divided into three groups as chlorinated hydrocarbon, organophosphates or carbamates and consisted of chemicals that were less harmful for the soil and did not accumulate over time. Some examples to second generation pesticides can be DDT or dimethoate.
Broad spectrum and narrow spectrum pesticides have the difference of effective range between them. Narrow spectrum pesticides are designed to target a specific organism such as a specific plant or an insect whereas broad spectrum pesticides are applicable to a wider range of organisms and still have the same effect for each.
Chitin Inhibitors can be given as an example of narrow-spectrum pesticides and the second generation pesticides in the answer can be given as an example of broad-spectrum pesticides.
