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Each organism in a population produces more offspring than can survive. This is called . In order for natural selection to occur, populations must have . When the environment changes, nature selects favorable . Over time, these in a population.

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

propane is burned to provide the heat in many cooking grills. the chemical reaction for this process is shown in the equation below.

c3h8 + 5o2 ? 3 co2 + 4h2o + energy

what are the products in this chemical reaction?

3co2 + 4h2o + energy

not always but somethings can be reproduced in a laboratory.