If there are two organisims in a closed system and they reproduce wouldn't the system gain weight?

Yes I know that the third organizim would consume, taking weight away, but theoreticly wouldn't the system gain weight because the cell in that third organizim split and reproduce?

If you mean a relative large animal, then no, they would die too soon. If you mean microscopic organisms that split into two, three etc, they would be smaller than the parent organism, until they can no more divide as they cannot grow.

Anyway, that's my opinion, I'm not saying that I'm 100% sure of it.

But theroreticly because the cell in that animal are reproducing, woudn't the system as a whole gain weight?

Let's say there are food and water in that closed system. The organism will feed, OK, but then, the organism will gain weight while the food will decrease, meaning there is no overall cahnge in weight.

But the cells in that organizim will still reproduce at a steady rate regardless of food intake.

A closed system cannot gain weight. Otherwise it would not be a closed system. It doesn't matter whether the organisms are large or small.

In real life, the Earth's ecosystems are not a closed system, mainly because they are constantly receiving an influx of energy from the sun.

Well that still seems like schinanigans to me, but it's nice to have an expert answer my question.

Actually, from a physical perspective, mass in a closed system is not constant, but mass-energy is. Some of the chemical processes in the closed system may change mass to energy or energy to mass as described by Einstein. But of course the change is nearly negligible. So the system could weigh slightly more or less depending on the thermicity of the chemical reactions.

You have to remember that the organisms would be taking in food in order for the offspring to grow. The mass of food will be identical (ignoring the effect mentionned above) to the mass of the offspring and any excretion.

Thanks, Cap and asking, for your supporting answers! Lol