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4th Grade Chapter 4 Lesson 4 How do people disturb the balance?

STUDY
PLAY
hazardous waste
substance that is very harmful to humans & other organisms
reclaiming
mining companies must replace rock & soil that were removed
oil
pollutant that can harm the ocean's plants and animals
lichens
good indicator of air quality
polluted
Water becomes ____________ when wastes & chemicals get into rivers, lakes & oceans.
National Parks System
established by the United States to preserve historic sites & habitats of many plants & animals
Yellowstone
world's first national park