Final answer:
Animals get sugars from the food they consume and oxygen from the environment. Unicellular organisms rely on diffusion, while larger animals have developed specialized respiratory systems like gills or lungs for oxygen intake. The relationship between plant photosynthesis and animal respiration is mutually beneficial.
Step-by-step explanation:
Animals obtain the raw materials for respiration, specifically sugar and oxygen, through various means. Sugar, in the form of glucose, comes from the food that animals eat. This food is broken down into nutrients including sugars by the digestive system. Oxygen, on the other hand, is obtained from the surrounding environment. This process varies depending on the organism's size and complexity. Simple unicellular organisms can directly absorb oxygen through diffusion across their cell membrane. However, larger animals have evolved specialized respiratory structures, such as gills and lungs, to breathe in oxygen. Therefore, the environment plays a key role in determining the methods animals use to acquire the oxygen necessary for cellular respiration.
In a mutual relationship, both plants and animals respire to derive energy. Plants produce oxygen and organic molecules through photosynthesis, and animals consume these products for energy. In return, animals exhale carbon dioxide, which plants then use in photosynthesis. Hence, animals are dependent on plants and related microbes for these essential compounds.