Cells use passive and active transport to move materials across cell membranes in order to maintain a constant internal environment. what is the process of maintaining a constant internal environment called?

amber has allowed scientists to study dna that has been preserved over millions of years.

weathering - colorado river carves land in arizona to form the grand canyon. cracks form in a sandstone wall surrounding a house. a marble statue near the science museum is changing color due to rainfall

erosion - after a rainstorm, soil and rock piees litter the roadways. the sand dunes in the sahara desert are changing shape.

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