Short answers, pulled from the story.
The fungal kingdom is a distinct group of organisms that are heterotrophs and must absorb dissolved organic molecules from their environment. Unlike plants, fungi lack chloroplasts and do not rely on sunlight to create energy. The defining characteristic that sets them apart is the presence of chitin in their cell walls, a tough structural molecule also found in the exoskeletons of insects and crustaceans.
Over 90% of all plant species engage in a symbiotic relationship with fungi through the common mycorrhizal network to trade nutrients for sugars produced through photosynthesis. This partnership dates back at least 400 million years and was essential for the colonization of land by plants. The fungal hyphae extend far beyond the root systems of plants to gather resources like nitrogen and phosphate, while also helping to hold soil together and increase carbon uptake from the atmosphere.
Estimates suggest there are between 2.2 and 3.8 million fungal species, yet only about 148,000 have been described by scientists. The true diversity of the kingdom is staggering and hidden in extreme environments ranging from the deep sea to the Arctic. Some species exist as microscopic single cells or tiny filaments within the soil, while others live as parasites on insects or survive in the intense radiation of space.
The amatoxins found in the death cap mushroom, Amanita phalloides, are responsible for the majority of fatal mushroom poisonings worldwide and cause severe organ failure and death if not treated promptly. Other mycotoxins, such as the aflatoxins produced by Aspergillus species, are highly carcinogenic and can contaminate grains and nuts. The ergot alkaloids produced by the fungus Claviceps purpurea have caused epidemics of ergotism, also known as St Anthony's Fire, which can cause gangrene, convulsions, and hallucinations.
The rice blast fungus, Magnaporthe oryzae, is a major pathogen that causes extensive damage to rice crops and threatens food security for billions of people. Other fungi, such as Ophiostoma ulmi, cause Dutch elm disease, which has wiped out millions of elm trees in North America and Europe. The chestnut blight, caused by Cryphonectria parasitica, nearly eradicated the American chestnut tree, a dominant species in the forests of the eastern United States.
Fossils of the fungal kingdom date back to the Paleoproterozoic era, some 1.6 billion years ago. The oldest fossilized mycelium to be identified from its molecular composition is between 715 and 810 million years old, and a fossilized fungus named Ourasphaira giraldae may have grown on land a billion years ago. Fungi were the dominant life form after the Permian-Triassic extinction event and a dramatic increase in evidence of fungi occurred 65 million years ago, immediately after the Cretaceous-Paleogene extinction event.