In animals, nitrogenous wastes are produced mostly from the catabolism of phospholipids and glycolipids proteins and nucleic acids starch and cellulose triglycerides and steroids

Option- "Proteins and Nucleic acid."

In animals, nitrogenous wastes are produced mostly from the catabolism(break down of macro molecules into simpler ones) of Protein molecules.

Explanation:

Proteins and nucleic acids:

Most of the organisms ingest different types of materials. And some of them are proteins which are composed up of different amino acids, as the proteins are important in many ways, they help in cells reproduction and growth etc.

And the nucleic acids are important polymers, which are required for carrying the operation of genetic material from one cell or being to another.Or it may occur simply from one generation to another in the form of RNA and DNA.

Why they are broken down?

Both the polymers consists the Nitrogen atom as the main constituent in there molecular structure, so that is why the break down of these materials results in the form of nitrogenous materials.

When proteins level exceeds from a certain level they need to be controlled and thus required the excessive materials to be excreted from the body. There are different forms or levels of the nitrogenous waste products which are excreted from an animal body. As there levels of organisms excrete them in different forms,which are as below:Beings living on land and Marine Fish: The nitrogenous waste is excreted mostly in the form of urea or uric acid, but mostly in the urea which is just because they have an optimum level of water as the solvent.Along with that the marine fish can also excretes the nitrogenous waste in the form of trimethylamine oxide.Ave's(Birds):Birds have a less availability of water in there body which makes them to excrete the nitrogenous waste product in the form of uric acids.Freshwater Fish: They excrete the amount of nitrogenous waste from the body in form of ammonia, as they have an abundance of water as solvent. While, there is an abundance of water in the environment, which they are able to dissolve the amount of nitrogenous waste products present inside the body and excrete it in the form of ammonia. Which is less toxic form of the nitrogenous waste materials.