carbon source An area of an ecosystem that emits more carbon dioxide than it absorbs.
deforestation Cutting down and/or burning trees in a forested area.
greenhouse gas Gases like carbon dioxide that absorb and hold heat from the sun’s in-
frared radiation.
global warming Warming of the Earth brought about by adding additional greenhouse
gases to the atmosphere.
hydrocarbon An organic compound that contains only hydrogen and carbon.
photosynthesis The process using carbon dioxide, water, and energy from sunlight by
which plants and algae produce their own food.
18.3 Human Populations.
Lesson Objectives
- Describe how changes in a limiting factor can alter the carrying capacity of a habitat.
- Discuss how humans have increased the carrying capacity of Earth for our species and
how we may have exceeded it. - Discuss how human activities like agriculture and urbanization have impacted the
planet. - Describe what sustainable development is.
Introduction
Improvements in agriculture, sanitation, and medical care have enabled the human popula-
tion to grow enormously in the last few 100 years. As the population grows, consumption,
waste, and the overuse of resources also grow. People are beginning to discuss and carry out
sustainable development that decreases the impact humans have on the planet.
Populations
The population size of a species depends on the biotic and abiotic factors present in that
ecosystem. Biotic factors include the amount of food that is available to that species and the
number of organisms that use that species as food. For life to thrive, a specific amount of