Here is a picture of a common slime mold growing on an orange. Some cells are unique in that they take in energy from the outside world because they do no have chlorophyll that help other plant cells to manufacture food. Yeast cells are an example. According to Webster's dictionary, yeasts are any of various single-celled fungi that reproduce asexually by budding or division. One site shows yeast budding or dividing.
Plants contain chloroplasts so they can manufacture food through photosynthesis.
You can read more about the definition of photosynthesis and about why leaves change color in the fall . For the complex creatures, explain how the cells become more specialized in comparison to one-celled organisms. What sort of organisms make up the animal kingdom.