Final answer:
Fungi are not plants because they are heterotrophic and have cell walls made of chitin. They play essential roles in ecosystems as decomposers and nutrient cyclers, but can sometimes cause diseases in plants and animals.
Step-by-step explanation:
Fungi are not considered plants because they lack several key characteristics that are typical of plant life. One major difference is that fungi do not perform photosynthesis; they cannot make their own food and are thus heterotrophic. Instead, they absorb nutrients from their environment. Unlike plants, which have cell walls made of cellulose, fungi have cell walls composed of chitin. Moreover, fungi typically disperse a vast number of spores for reproduction, using varied methods such as wind, water, and animal carriers.
Fungi play crucial roles in ecosystems. They are essential decomposers, breaking down dead organic matter and thus recycling nutrients. This process also benefits trees and plants by improving soil health and fertility. Some fungi also form symbiotic relationships with plants, known as mycorrhizae, where they increase a plant's water and nutrient absorption. Despite their benefits, fungi can be bad when they act as plant pathogens, causing diseases that can damage crops and other important vegetation.
While fungi are beneficial decomposers, they can sometimes be bad for environments when they cause infections in humans, animals, or plants. Invasive fungal species can disrupt ecosystems, leading to biodiversity loss and altering habitat structures.