Do the cells in bigger animals have bigger size? Explain
......Long Question
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Answer:
They are about the same size, bigger animals just have more cells. You see, an important part of cells is maintaining a specific surface area to volume ratio. ... Although cells vary in size, they are mostly close to the same (microscopic) size. larger animals just have a LOT more of them.
Answer:As with everything it depends. Lets just look at mammals, say from mouse to elephants.
What is important to understand the “why” a bit better is that smaller animals have a much higher metabolism, so need more energy per gram of body weigh per minute. When you look at the graph below, you can see there is an extra strong increase for very small mammals, hence mammals can not get as small as bees, they could not eat enough to deliver all the energy needed:
Scaling of number, size, and metabolic rate of cells with body size in mammals
Cells in the various animals were found to be of two types. The first type shows an invariable size and scales with the metabolic rate:
This means cells stay more or less the same size (horizontal line trend). These cells are very active cells, like fibroblasts, Henle loop (kidney) cells, or erythrocytes (the products of very active cells). But look at the data points, for example the trend is flat for erythrocytes, but elephants have several times larger red blood cells than mice! Some cell types even shrink in size: a mouse has bigger liver cells (hepatocytes) than an Elephant by a factor of about 3! This is because the liver cells are extremely metabolic active, and the size of a cell, the cytoplasm, that can be served by one nucleus decreases with the metabolic activity.
Cell size depends on nuclear information read out speed in metabolic active cells: we bread many polyploid food staples. These have multiple copies of their chromosomes in the nucleus, more single genes can be read in parallel, the amount of cytoplasm served by one nucleus increases, we get bigger cells and bigger edible parts of the plants, like in corn and wheat.
Back to the mammals; some cells scale with the size of the animal and have an invariable rate of metabolism, like fat cells or neurons (they have to reach further, into the legs or all the way to the tip of the trunk!)
However, this still does not make up for the increase of the body size, as the cell numbers even of these growing cells (fat cells and neurons are 15 times bigger in elephants than in mice) are increasing with body size:
So an elephant has one billion times more fat cells and only 10 000 times more neurons than a mouse. Neurons are a special case: you can not afford too many more neurons in between connected points, as each synapse slows the transmission down a lot. Still, a mouse reacts a lot faster than an elephant (you want to see it move, you need slow motion films) and its :frame rate” in the brain is a lot higher than the elephants (hence elephants panic as they can not see fast movements a good). This also explains why bigger brains do not make you more intelligent: an elephant has only a thousand times more brain cells than a human, mainly they are bigger, hence its brain is also bigger (5 times more mass than humans), but busy with the bigger body, not more intelligent. More neurons could make more connections and create more intelligence, but the elephants neurons are 5–7 times bigger, so have less connectivity than humans.
There you go, animals (and plants) differ in size due to the difference in cell numbers, mainly, not due to cell sizes. However, metabolically less active and not dividing cells also increase in size.
This leads to elephants having a pregnancy that is as long as the life span of a mouse!
Since elephants have so much more cell divisions going on, they need better control of them, to avoid cancer. With the human cancer and cell division control elements, every half grown elephant would already have cancer. They have a 5 fold higher number of the main tumor suppressor genes compared to humans.
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