The document discusses using population pyramids to predict population change. It provides population data for the UK in 2010 and 2050 broken down by age and gender. Population pyramids visually depict this data using bars to show male and female populations in each age group. Comparing pyramids from different times allows predicting how a population will change in the future. The homework is to create a 3D population pyramid for the UK in 2050 using materials like Lego bricks or jelly babies and compare it to the 2010 pyramid.