What is an advantage of a change in pulse rate after exercising?
(1) the heart needs to produce more energy to supply the active muscle cells and maintain homeostasis.
(2) an increased blood flow carries excess waste products away from the active muscle cells.
(3) the blood is removing oxygen from muscle cells that were not active and carrying it to muscle cells that
are active.
(4) the blood is supplying the active muscle cells with carbon dioxide to neutralize wastes in those cells.

This is a typical grassland food web. it is also a small picture of an important cycle on earth: the carbon cycle. describe how the carbon gets into this food web. a) bacteria and fungi, the decomposers, recycle carbon from dead organisms. b) carbon is found in the grass and is passed from one level to the next in this food web. eliminate c) all living things give off carbon dioxide as a by-product of respiration and it is released into the atmosphere. d) plants use carbon dioxide as a reactant in photosynthesis, to make usable chemical energy in the form of a sugar.