Farmers have been selectively breeding chickens for thousands of years. The basic method is quite simple. If you breed from the hen which lays the most eggs, the chances are that her daughters will also be good layers. This is because the number of eggs which a hen lays is partly controlled by the genes which a hen inherits from her parents. Egg production can also be increased by environment, for example by providing good feed and keeping the lights on for longer since day length affects the laying pattern.
With modern scientific breeding, hens today lay over 300 eggs per year, around ten times as many as their jungle fowl ancestors. In the same way, broiler or meat chickens have been selectively bred to grow very fast using the same principle.
The result is cheap meat or eggs, but high production can come at a cost to the welfare of the animals. The worksheet discusses the basic principles of selective breeding while raising ethical issues relating to the use of science and technology. Students are encouraged to formulate their own opinions, especially in relation to the different ways we use animals in producing food.