Animal cells do not have cell walls<span> because they </span>do not need<span> them. </span>Cell walls<span>, which are found in </span>plant cells<span>, maintain </span>cell<span> shape, almost as if each </span>cell has<span>its own exoskeleton. This rigidity allows </span>plants<span> to stand upright without the </span>need<span> for bones or musculature.</span>
<span> cells maintain homeostasis as they are living things. The main way cells maintain homeostasis is through their cell membranes. Cell membranes protect the cell from the outside world, if there is too much of something in the cell, the cell membrane uses pockets to expel some of it, it trasports nutrients across the cell, and it also dictates what goes in and out of the cell. Those are some ways a cell maintains homeostasis. And all living things must maintain homeostasis</span><span>: <span>Regulate intracellular ion control (e.g. maintain very specific [Ca^2+] levels)
Regulate extracelluar to intracellular ion transport. E.g. for maintaining water and blood pressure via the kidneys.
Regulate metabolism, for temperature control (e.g. in brown adipose tissue).
Regulate transcription and translation, for hormone release and
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<span>How long participants practice a task can also be modified to help optimize skill development. Some individuals might need additional sessions to achieve a desired physical activity outcome, whereas others might attain personal goals in fewer sessions. </span>
