Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 24: Ode To The Fungus Among Us
Document related concepts
no text concepts found
Transcript
Chapter 24: Fungi Characteristics of Fungi Mode of Nutrition Fungi are heterotrophs Most are saprobes Saprobes – obtain nutrients from nonliving organic matter and so cause it to decay Others are parasites Parasites – extract nutrients from tissues of a living host Without the fungi (and heterotrophic bacteria) organisms would slowly become buried in their own waste and life could not go on. 56,000 known fungal species and at least a million more unknown species Fungi evolved before 900 million years ago Some moved onto land 430 million years ago Survey of Fungal Groups Zygomycetes (Zygomycota) Sac Fungi (Ascomycota) Club Fungi (Basidiomycota) The vast majority of species are multicelled Other kinds of fungi known as “imperfect fungi” are lumped together, but not in a formal taxonomic group. Key Features of Fungal Life Cycle Majority of the species are multi-celled Reproduce asexually quite often, but given the opportunity they also reproduce sexually Form lots of nonmotile spores Spores - reproductive cells that germinate after dispersal Spores give rise to a mesh of mycelium Mycelium – a mesh of branched filaments Mycelium rapidly grows over or into organic matter Hypha – each filament in a mycelium Cytoplasm of hypha cells interconnects so nutrients flow throughout the mycelium Have septa – divide the filament into compartments containing a single nucleus When filaments lack septa they are multinucleate or coenocytic Cell walls contain chitin Basidiomycetes - Club Fungi 25,000 or so species of club fungi spores are club shaped saprobic species are important decomposers Ex. mushrooms, shelf fungi, coral fungi, puffballs fungal rusts and smuts can destroy fields wheat, corn, etc Agaricus brunnescens – the common grocery store mushroom Amillaria bulbosa – one of the oldest and largest organisms One individual extends through 15 hectacres of soil and may weigh more than 10,000 kg Has been growing for more than 1,500 years Examples of a Fungal Life Cycle A. brunnescens – common mushroom Produces short lived reproductive bodies, mushrooms, that are its aboveground parts Mycelium is buried in soil A mushroom has a stalk and cap Gills (fine tissue sheets) line the caps inner surface Basidiospores – are spores under cap When spores are dispersed and land on a suitable site, it germinates and gives rise to haploid mycelium If 2 hyphae fuse they form dikaryotic mycelium and form an extensive mycelium When conditions are favorable mushrooms form. After nuclear fusion, the club shaped structure (now 2n) will produce and bear haploid spores at the four tips of the cell diploid (2n) nuclear fusion meiosis haploid (n) club-shaped structures having two nuclei (n+n) form at the margin of each gill spores (n) spores released each germinating spore gives rise to a hypha that grow and becomes a branching mycelium after cytoplasmic fusion, a dikaryotic (n+n) mycelium gives rise to spore-bearing bodies (mushrooms) Spores and More Spores Spores are usually small and dry Air currents disperse them Fungus produces sexual spores, asexual spores or both Which spores that are produced depends on contact with a suitable hypha, food availability, and how cool or damp conditions are Each fungal class produces unique sexual spores Each spore that germinates can be the start of a hypha and mycelium Stalked reproductive structures may develop on many of the hyphae and produce more asexual spores These can form more mycelium Zygomycetes Parasitic species that feed on insects Most live in soil decaying plants or animal material and stored food A thick walled sexual spore (2n) zygote, forms when it reproduces sexually Zygosporangium – a thin clear covering encloses the zygote Zygote goes through meiosis and gives rise to a specialized hypha that bears a spore sac Each spore can give rise to a mycelium Ex. Black bread mold Ascomycetes – The Sac Fungi Sac fungi Most form sexual spores called ascospores within sac-shaped cells (asci) Resemble flasks, globes, and shallow cups Reproductive structures are in asci of multicelled species Ex. Truffles, morels, penicillium, aspergillus (multi-celled) Ex. Yeasts (single celled) Exclusive Spores of the Imperfect Fungi Nobody knows what kind of sexual spores they produce, so they are not classified Fungal Symbionts Fungi was here as symbionists when plants first invaded the land Symbiosis – species that live together in close association Mutualism – benefits both partners or does one of them no harm Lichens Intertwined with one or more photosynthetic species Fungal part is mycobiont Photosynthetic part is photobiont Typically colonize sites on sunbaked or frozen rocks, fence posts, gravestones. Mutualistic associations between fungi and algae Algae is usually cyanobacteria Fungi provides water and protection from the environment Algae provides sugar from photosynthesis and nitrogen is provided if the algae is nitrogen fixing Mycorrhizae Mutualistic association between fungi and roots Fungus increases the ability of the roots to absorb minerals As Fungi Go, So Go The Forests Number and kinds of fungi are declining at alarming rates Decline does correlate with rising air pollution When fungi die trees lose vital support system and they become vulnerable to severe frost and drought Fungi help plants in another way because many of them are premier decomposers. They break down the organic compounds in their surroundings Fungi grow in or on organic matter and secrete enzymes that digest it into pieces that individual cells can absorb Chapter 24: Ode To The Fungus Among Us Characteristics of Fungi Mode of Nutrition Fungi are _______________ Most are _______________ Saprobes – Others are _______________ Parasites – Without the fungi (and heterotrophic bacteria) organisms would slowly become buried in their own waste and life could not go on. ____________ known fungal species and at least a million more unknown species Fungi evolved before ________ million years ago Some moved onto land ________ million years ago Major Groups The vast majority of species are _______________ Other kinds of fungi known as “imperfect fungi” are lumped together, but not in a formal taxonomic group. Key Features of Fungal Life Cycle Majority of the species are multi-celled Reproduce ______________ quite often, but given the opportunity they also reproduce ______________ Form lots of _______________ spores Spores Spores give rise to a mesh of mycelium Mycelium – Mycelium rapidly grows over or into organic matter Hypha – Cytoplasm of hypha cells interconnects so nutrients flow throughout the mycelium Have septa – When filaments lack septa they are multinucleate or coenocytic Consider the Club Fungi __________ or so species of club fungi Spores are club shaped Saprobic species are important decomposers Ex. Fungal rusts and __________ can destroy fields wheat, corn, etc Agaricus brunnescens – Amillaria bulbosa – One individual extends through 15 hectacres of soil and may weigh more than 10,000 kg Has been growing for more than 1,500 years Examples of a Fungal Life Cycle A. brunnescens – Produces short lived reproductive bodies, _______________, that are its aboveground parts A mushroom has a _________ and __________ Gills (fine tissue sheets) line the caps inner surface Basidiospores – When spores are dispersed and land on a suitable site, it germinates and gives rise to haploid mycelium If ____ hyphae fuse they form dikaryotic mycelium and form an extensive mycelium When conditions are favorable mushrooms form. After nuclear fusion, the club shaped structure (now 2n) will produce and bear haploid spores at the four tips of the cell diploid (2n) nuclear fusion meiosis haploid (n) club-shaped structures having two nuclei (n+n) form at the margin of each gill spores (n) spores released each germinating spore gives rise to a hypha that grow and becomes a branching mycelium after cytoplasmic fusion, a dikaryotic (n+n) mycelium gives rise to spore-bearing bodies (mushrooms) Spores and More Spores Spores are usually small and dry Fungus produces sexual spores, asexual spores or both Which spores that are produced depends on contact with a suitable ____________, food availability, and how cool or damp conditions are Each fungal class produces unique ____________ spores Stalked reproductive structures may develop on many of the hyphae and produce more asexual spores Producers of Zygosporangia Most live in soil decaying plants or animal material and stored food A thick walled sexual spore (2n) zygote, forms when it reproduces sexually Zygosporangium – Zygote goes through ____________ and gives rise to a specialized hypha that bears a spore sac Each spore can give rise to a mycelium Ex. Producers of Ascospores Most form sexual spores called ascospores within sac-shaped cells (asci) Reproductive structures are in asci of multicelled species Ex. Ex. Exclusive Spores of the Imperfect Fungi Nobody knows what kind of sexual spores they produce, so they are not classified The Symbionts Revisited Fungi was here as symbionists when plants first invaded the land Symbiosis – species that live together in close association Mutualism – benefits both partners or does one of them no harm Lichens Intertwined with one or more photosynthetic species Fungal part is _______________ Photosynthetic part is _______________ Typically colonize sites on sunbaked or frozen rocks, fence posts, gravestones. Mutualistic associations between __________ and __________ Algae is usually __________________ Fungi provides __________ and protection from the environment Algae provides __________ from photosynthesis and nitrogen is provided if the algae is nitrogen fixing Mycorrhizae Mutualistic association between __________ and __________ Fungus increases the ability of the roots to absorb minerals As Fungi Go, So Go The Forests Number and kinds of fungi are declining at alarming rates Decline does correlate with rising ______ _______________ When fungi die trees lose vital support system and they become vulnerable to severe frost and drought Fungi help plants in another way because many of them are premier decomposers. They break down the organic compounds in their surroundings Fungi grow in or on ___________ matter and secrete ____________ that digest it into pieces that individual cells can absorb
