Question

All living things,plants and animals are made up of carbon compounds (organic compounds).

But then also the amount of carbon present is very very low, being about 0.02-0.03%.Why?

Answer 1

$because \: it \: is \: harm \: full \: too \: in \: some \: compounds \\ the \: excess \: of \: everything \: is \: bad$

Answer 2

carbon IS found in all organic matter, but NOT in inorganic matter. ... In a more general sense, organic refers to living things. And this is connected to the idea of organic chemistry being based on carbon compounds. Organic (carbon-based) compounds are found in all living things.
Earth, representing approximately 45-50% of all dry biomass. Complex molecules are madeup of carbon bonded with other elements, especially oxygen and hydrogen and frequently also with nitrogen, phosphorus and sulfur. Carbon is abundant on Earth.
So, what can we say about the amount of carbon on Earth?

Carbon is the 15th most common element in the Earth’s crust. It gets sequestered in various substances as part of the carbon cycle like plants and limestone and coal and water bodies.

It’s in the atmosphere as part of carbon dioxide. However, the atmosphere is mostly nitrogen 78.09%, oxygen 20.95%, 0.93% argon, 0.04% carbon dioxide, and a few other trace gases. A tiny fraction is carbon.

So, at first blush, we can see that carbon is not in “everything.”

hope this helps u.. :-)