Barter is the correct answer
The body system that directly provides for this demand is the circulatory system. When you exercise, the circulatory and muscle system cooperate, in order to meet the increased needs for strength and energy. The circulatory system involves the network which delivers blood to every part of your body. This flowing of blood ensures that the tissues are oxygenated and rich in necessary nutrients. During exercise, more blood flows to and from your muscles, in order to deliver the necessary amounts of oxygen to complete the aerobic respiration.
They survive without water by entering a special mode, otherwise called as shriveling. They can lose even 95% of water in their body and still live, even though they would look like dead plants, they would actually be alive. In the absence of water, tardigrades use a sugar called trehalose, which becomes their source of life until they find some water.
I believe true because the Precambrian is the first geologic time, going back 4600-570 years ago, meaning it should contain the earliest of things.
<span>Cell Membrane which is a Selectively Permeable Membrane.
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