Eric made a physical model of a cell membrane by putting one zip-top plastic bag inside another. He punched some straws through the plastic so that they led from outside the outer bag to the inside of the inner bag.

Which of the following features of a cell membrane can be seen using Eric's physical model?

Proteins and other molecules can move around within the cell membrane.
A cell membrane is made of two layers.
Some molecules can pass directly through the cell membrane.
Pores and proteins in the cell membrane allow passage through it.

Atree root breaking a rock into smaller fragments is an example of both and mechanical weathering. when rocks are exposed to heat, they which can contribute to thermal stress. when harmful gases, such as sulfur dioxide and nitrogen oxide, react with water in the atmosphere, they can produce the agent of erosion involved in stream erosion is when the ground is so saturated that it can't absorb rainfall or when rain falls so quickly that the ground can't absorb the water, forms. a/an is a huge, heavy, moving body of ice that picks up rocks and sand and erodes the ground beneath it as these materials scrape across it. hot arid climates are prone to erosion by rows of trees and shrubs planted to protect fields from wind erosion are known as