Algae are capable of absorbing water and minerals all over the thallus, therefore, they do not need conductive tissues. The integumentary tissues that protect the body from water loss, the effects of low and high temperatures are also not necessary (in the aquatic environment, temperature fluctuations are smoothed in comparison with the ground-air). Water is 800 times denser than air, has a buoyancy force, which allows algae to maintain their thallus, without mechanical tissue. Therefore, the tissues did not develop in algae, but in their descendants – plants – as an adaptation to existence in the ground-air environment.
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