3. how has the human population changed during the last 50 years?

Population in the world is currently (2019-2020) growing at a rate of around 1.08% per year (down from 1.10% in 2018, 1.12% in 2017 and 1.14% in 2016). The current average population increase is estimated at 82 million people per year.

Explanation:

Depending on which estimate is used, human overpopulation may have already occurred. Nevertheless, the rapid recent increase in human population has created concern. The population is expected to reach between 8 and 10.5 billion between the years 2040 and 2050.More than 8 out of 10 people in the world will live in Asia or Africa by 2100. ... Over the past 50 years Asia experienced rapid population growth. Today its population stands at around 4.6 billion. By 2050 it's expected to rise to 5.3 billion, but then fall in the latter half of the century.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.