Ch. 24 Fungi
The Greening of Earth
Terrestrial surface of earth was lifeless for the first 2 billion years
Cyanobacteria and protists likely existed on land 1.2 billion years ago
Around 500 million years ago, small plants, fungi, and animals emerged on land
The first forests formed about 385 million years ago
Although not closely related, plants and fungi colonized the land as partners before animals
arrived
Fungi are heterotrophic
o They could be decomposers, mutualistic, or parasitic
Fungi Played a key role in the colonization of land
Earliest land plants did not have true roots or leaves
Fossil evidence indicates that plants formed symbiotic associations with fungi, which may have
helped them obtain nutrients
Fungi are heterotrophs that absorb nutrients from outside of their body
Fungi consist of networks of branched hyphae, filaments adapted for absorption
Fungal cell walls contain chitin, a strong, flexible polysaccharide
The body of the fungus is called the thallus
Mycorrhizae are a plant-fungal symbiosis in which fungal hyphae transfer nutrients to the plant
partner from its roots
Such symbiotic associations may have helped plants without roots colonize land
In mycorrhizae, the fungus improves the delivering of phosphate ions and other minerals to the
plant
The plant provides the fungal partner with organic nutrients, such as carbohydrates
Fungus-plant mutualism includes the endophytes
o Fungi that live inside tissue without damaging the host plant
o They release toxins that repel herbivores or confer resistance to environmental stress
factors such as infection by microorganism, drought, or heavy metals in the soil
Lichens are “mutualism” between
o Fungus-structure
o Algae or cyanobacterium- provides food
Lichens live in environments where neither fungi nor algae could live alone
While the fungi do not grow alone in the wild, some lichen algae occur as free-living organisms
The Origin of Fungi
Fungi and plants are more closely related to each other than to plants or eukaryotes
DNA evidence shows that-
o Fungi are most closely related to unicellular nuclearrids
o Animals are most closely related to unicellular choanoflagellates
Multicellularity arose separately in fungi and in animals
Morphological Adaptations
The Greening of Earth
Terrestrial surface of earth was lifeless for the first 2 billion years
Cyanobacteria and protists likely existed on land 1.2 billion years ago
Around 500 million years ago, small plants, fungi, and animals emerged on land
The first forests formed about 385 million years ago
Although not closely related, plants and fungi colonized the land as partners before animals
arrived
Fungi are heterotrophic
o They could be decomposers, mutualistic, or parasitic
Fungi Played a key role in the colonization of land
Earliest land plants did not have true roots or leaves
Fossil evidence indicates that plants formed symbiotic associations with fungi, which may have
helped them obtain nutrients
Fungi are heterotrophs that absorb nutrients from outside of their body
Fungi consist of networks of branched hyphae, filaments adapted for absorption
Fungal cell walls contain chitin, a strong, flexible polysaccharide
The body of the fungus is called the thallus
Mycorrhizae are a plant-fungal symbiosis in which fungal hyphae transfer nutrients to the plant
partner from its roots
Such symbiotic associations may have helped plants without roots colonize land
In mycorrhizae, the fungus improves the delivering of phosphate ions and other minerals to the
plant
The plant provides the fungal partner with organic nutrients, such as carbohydrates
Fungus-plant mutualism includes the endophytes
o Fungi that live inside tissue without damaging the host plant
o They release toxins that repel herbivores or confer resistance to environmental stress
factors such as infection by microorganism, drought, or heavy metals in the soil
Lichens are “mutualism” between
o Fungus-structure
o Algae or cyanobacterium- provides food
Lichens live in environments where neither fungi nor algae could live alone
While the fungi do not grow alone in the wild, some lichen algae occur as free-living organisms
The Origin of Fungi
Fungi and plants are more closely related to each other than to plants or eukaryotes
DNA evidence shows that-
o Fungi are most closely related to unicellular nuclearrids
o Animals are most closely related to unicellular choanoflagellates
Multicellularity arose separately in fungi and in animals
Morphological Adaptations
