How are plants different from Animals and Fungi?

Answer 1

Fungi such as the mushrooms are neither plants nor animals. They belong in their own separate kingdom, the Fungi.

• Unlike plants, fungi are heterotrophic. They do not contain any plastids and cannot make food for themselves. Some are even parasitic. (Though, some plants are parasitic, too.)
• Unlike animals, fungi are generally sessile. For this reason, one might assume that fungi and plants are alike, which is not true. For a fungi, the digestion occurs outside and absorbs the nutrients. For an animal, digestion and absorption occurs on the inside.

Fungi represent a unique evolutionary lineage from plants or animals. Our current philosophy on taxonomy is that it should reflect, as close as possible, evolutionary relationships/history. Thus, fungi are a separate kingdom from plants or animals. Eumycota, or the fungal kingdom, is separated out from plants by the lack of chloroplasts, the type and number of flagella, the use of glycogen (not starch) as an means of storing energy, and the presence of chitin (instead of cellulose) in the cell walls. The fungal kingdom is separated from animals by the presence of the cell wall, the ability to synthesize lysine, and lack of ingestion of food prior to digestion. (I was originally going to write "extracellular digestion;" however, animals also digest extracellularly. Animals secrete enzymes into the digestive tract, which is open to the environment, and absorb the byproducts. The true distinction is that animals ingest the food and section off a portion of the environment in the digestive tract. Fungi secrete the enzymes directly into the external environment.)

I will note there is a move in mycological circles to using the terms "fungi" and "fungus" in the same manner as algae--as a functional group not a taxonomic group. This is because the oomycetes and the slime molds were traditionally classified as fungi. However, molecular and biochemical analyses have revealed that they are indeed members of separate kingdoms. (With a considerable amount of evolutionary distance from the Eumycota.)

Answer 2

The property that sets plants apart from animals and fungi is the fact that plants are generally autotrophs. This means that they can produce their own food through a process called photosynthesis whereas animals and fungi have to obtain their food from other organisms.