18.3 HUMAN POPULATIONS Our Biosphere

Learning Targets 1.Describe how changes in a limiting factor can alter the carrying capacity of a habitat 2.Discuss how humans have increased the carrying capacity of Earth for our species and how we may have exceeded it 3.Discuss how human activities such as agriculture and urbanization have impacted the planet 4.Describe sustainable development

Population Growth 1.What determines population size of species in ecosystem? 2.What are important biotic and abiotic factors? 3.When does a population grow? 4.When does a population shrink? 5.What causes a population to grow? 6.What causes a population to shrink?

Population Growth 1.All populations grow until they reach carrying capacity a)Carrying capacity – maximum number of individuals that an environment can support 2.What does carrying capacity depend on?

Population Growth 1.Carrying capacity caused by limiting factors a)Predators, lack of resources, lack of space

Human Population Growth 1.Carrying capacity for humans is unknown a)10,000,000 before agriculture b)7 Billion currently c)Humans have taken away habitats and filled the niches of thousands from other species Mass extinction

Human Population Growth

Green Revolution 1.Huge advances in agriculture in recent decades a)Genetically altered crops b)Fertilizers and chemical pesticides c)Agricultural machinery d)Increase access to water 2.Humans have increased carrying capacity by our genius minds

Overpopulation 1.Even though we have increased carrying capacity through agriculture, is there another limiting factor? 2.Famine, disease, war, space, clean water, sanitation systems, etc.

Carrying capacity is usually only clear after populations have exceeded it

Consequences 1.Pollution: a)Water – Dead Zones b)Air – Farm Machinery c)Land – Pesticides 2.Cancer 3.Any others?

Sustainable Development 1.Idea that natural resources should not be used faster than they can be replaced