Question

Why do animals have more complex excretory systems than plants

Answer 1

Plants only take in CO2, water, and sunlight to make sugar (which is their primary source of food)

Animals need a wide range of food (Carbohydrates, proteins, and lipids). We also need to have the right enzymes to break down these food and absorb them due to their size. Because we intake bulk amounts of food, some of the component of the food are waste/ cannot be broken down by the human body (Cellulose).