Protists excrete waste by diffusion through their cell walls. Food particles diffuse through the cell wall and into a food vacuole. The food is then processed by enzymes, the materials that cannot be broken down are then diffused through the cell wall outside of the organism.
Annelid worms contain nephridium in each segment of their body. Most have two, one for bringing in materials and one for excreting waste. Food goes into one of the nephridium into the intestines where it is broken down, the materials that are used are passed onto the blood system. Waste is small tubules and out of the other nephridium.
Insects excrete waste the same way as humans do. The food they eat is passed through their stomach and intestines to be broken down. After the waste is separated it is passed to the rectum and excreted from the anus.
Amphibians also excrete their waste the same way. After food is digested and waste is separated the waste goes to the rectum and out of the anus.
Mammals excretory system is the same as insects and amphibians. he food goes into their mouth through the intestines and out of the anus.
Non vascular plants do not excrete waste like other organisms. The waste is stored in a vacuole until it is ready to be excreted. When the waste is excreted it is done by photosynthesis.