The first Agriculture is explaining what people did long time ago around 1100 to 2000 BC. They planted and domestication of plants and animals, mainly wheat and they would tame wild animals.
Around this time line the second agriculture happened the fields have doubled their size! the reason behind that is because the population was growing so quickly , so what they would do to make it a little easier , they used plows and horse collars like the image bellow.
The third agriculture started around the 1970 and 1980. it was really using the same amount of land but more crops and the technology is a lot more useful and more common. The lands have grown much larger but there's not as many farms now so less people have jobs for farming.
GMOs refers to the change in the way of any organism. It changes the way people farm because it's taking over the farming industry. For example, ¨In 2014, GMO varieties made up 93 percent of corn acres, 94 percent of soybean acres and 96 percent of cotton acres planted in the country. With the rise of GMO crops, coexistence between organic, non-GMO and GMO production has become more difficult due to the potential for gene flow and commingling of crops at both the planting and harvesting levels.¨ (http://www.foodandwaterwatch.org/insight/how-gmo-crops-hurt-farmers) Pros: lower risk of crop failure and modifying some food can lead to better nutrition. Cons: Food allergies have increased in children and the genes in the food may migrate into other plants such as, weeds.