The Six Kingdoms of Life: Where Do Mushrooms Fit In?
Biology is all about organizing life. From tiny bacteria to towering trees, scientists use a classification system to group organisms based on their characteristics and evolutionary history. One of the most fundamental ways life is organized is through biological kingdoms.
In this blog, we’ll walk through the six major kingdoms of life, and then we’ll dive into a surprising twist—how mushrooms, and fungi in general, are more closely related to animals than you might think.
1. Kingdom Archaea
Archaea are single-celled microorganisms that look a lot like bacteria—but they’re not. They thrive in extreme environments like hot springs, salty lakes, and deep-sea vents. Archaea have unique genetic and metabolic features that set them apart from all other life forms.
Examples: Thermophiles (heat-loving microbes), halophiles (salt-loving), methanogens (produce methane)
2. Kingdom Bacteria (Eubacteria)
Bacteria are the more familiar single-celled organisms. Found in soil, water, our bodies, and almost everywhere else, bacteria play vital roles in ecosystems and health. Some help us digest food; others cause illness.
Examples: E. coli, Streptococcus, Lactobacillus
3. Kingdom Protista
Protists are a diverse group of mostly single-celled organisms that don’t fit neatly into other kingdoms. Some behave like animals, some like plants, and others like fungi. They’re the biological "miscellaneous drawer."
Examples: Amoebas, algae, slime molds
4. Kingdom Plantae (Plants)
These are multicellular, photosynthetic organisms. Plants use sunlight to create energy through photosynthesis and are the primary producers in most ecosystems.
Examples: Trees, flowers, grasses, ferns, mosses
5. Kingdom Animalia (Animals)
This kingdom includes all multicellular organisms that consume food rather than producing it. Animals have nervous systems, move (at least during some life stage), and digest other organisms for energy.
Examples: Humans, insects, birds, fish, mammals
6. Kingdom Fungi
Now we get to the fungi—mushrooms, molds, yeasts, and more. Fungi were once lumped in with plants, but scientists now know they’re completely different. Fungi do not photosynthesize. Instead, they absorb nutrients from other materials—living or dead.
Examples: Oyster mushrooms, baker’s yeast, truffles, reishi, penicillin mold
Wait—Are Fungi More Like Animals?
Yes, and here’s where it gets really interesting.
While fungi and plants are both stationary and grow from the ground, genetically and biochemically, fungi are more closely related to animals than plants.
Here’s how:
Cell walls: Plants use cellulose; fungi use chitin—the same material found in insect shells.
Energy storage: Plants store energy as starch; fungi (like animals) store it as glycogen.
Digestion: Fungi absorb nutrients from their environment after breaking it down externally—kind of like how animals digest food outside cells, then absorb it.
Genetic similarity: Molecular studies show that fungi and animals share a more recent common ancestor than fungi and plants do.
What Does This Mean for Mushrooms?
Mushrooms are the fruiting bodies of fungi—essentially the reproductive structures. When you eat a mushroom, you’re eating the product of an organism that’s more animal-like than you might expect. This connection explains why:
Mushrooms have umami flavors, often described as “meaty.”
Mushroom-based proteins and meat alternatives taste surprisingly similar to animal products.
Mushrooms interact with human biochemistry in complex ways, such as supporting brain health and immune function—possibly because of our evolutionary similarities.
Final Thoughts
The kingdom system helps us understand the incredible diversity of life on Earth. From bacteria to bears, every living thing has a place. But fungi? They’re a fascinating group of their own—more like us than we often realize.
So next time you sauté mushrooms or take a lion’s mane tincture, remember: you’re not just eating a plant substitute. You’re connecting with a kingdom that’s a little closer to home than you thought.
