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Outline of lichens

Outline of lichens is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Outline of lichens rather than just read about it. In short: The following outline provides an overview of and topical guide to lichens. Lichens are composite organisms made up of multiple species.

Outline of lichens — main illustration
Outline of lichens — illustration

Key takeaways

  • Outline of lichens belongs to biology; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Outline of lichens to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Outline of lichens from memory before moving on to harder problems.

Reference excerpt

The following outline provides an overview of and topical guide to lichens. Lichens are composite organisms made up of multiple species. They comprise a fungal partner, one or more photosynthetic partners, which can be either green algae or cyanobacteria, and, in at least 52 genera of lichens, a yeast. In American English, "lichen" is pronounced the same as the verb "liken" (). In British English, both this pronunciation and one rhyming with "kitchen" () are used.

Descriptions of lichens

A lichen can be described as all of the following:

Life form – an entity that is alive. Composite organism – a symbiotic life form composed of multiple partners from different biological domains, families and kingdoms, and from different phyla, classes and divisions within those domains and kingdoms. In the case of lichens, a fungal partner (the mycobiont) combines with one or more photosynthetic partner(s) (the photobiont) as well as (in some cases) a yeast. Eukaryote (domain) – organisms with a cell nucleus within a nuclear envelope; both the mycobiont and any algal partners fall into this domain. Fungi (kingdom) – the fungal partner and any yeast partner fall into this kingdom. Ascomycota (phylum) and/or Basidiomycota (phylum) For the biological classes and families these fungi belong to, see below. Chlorophyta (division) – if the photobiont is a green alga, it falls into this taxonomic division. Trebouxiophyceae (class) Trebouxiaceae (family) Ulvophyceae (class) Trentepohliaceae (family) Prokaryote (domain) – organisms without a cell nucleus; any cyanobacterial partner falls into this domain. Bacteria (domain) Cyanobacteria (phylum)

Nature of lichens

Morphology Lichen anatomy and physiology Apoplast – the symbiotic interface zone between the mycobiont and photobiont, outside the cell membranes or walls of both. Haustorium (pl. haustoria) – a root-like structure which allows the fungal partner to extract nutrients from its photosynthetic partner(s). Lichen morphology – a lichen's external appearance and structures are very different than those of its individual partners. Ascocarp – the fruiting body of a lichen, which contains the asci. Ascus (pl. asci) – a sexual, fungal spore-bearing structure, typically sac-like in shape. Ascospore – a fungal spore, the product of meiosis, produced in an ascus. Epispore – a transparent bag-like outer covering on some spores, which helps to determine spore shape. Cephalodium (pl. cephalodia) – a gall-like structure that contains cyanobacteria Hypha (pl. hyphae) – a long, branching, thread-like structure composed of one or more fungal cells, which typically makes up a large part of lichens; hyphae are densely compacted in the cortex and more loosely interwoven in the medulla. Pycnidium (pl. pycnidia) – a flask-shaped, asexual fruiting body possessed by some lichens. Conidium (pl. conidia) – an asexual fungal spore produced in pycnidia by some lichens. Rhizine – a root-like structure that anchors a lichen to the substrate on which it grows. Soralium (pl. soralia) – a localized region or structure, typically a crack or pore, containing soredium. Soredium (pl. soredia) – asexual reproductive propagules composed of loose clumps of fungal hyphae and photobiont cells, produced in soralia. Thallus (pl. thalli) – the vegetative body of a lichen, made up of both mycobiont and photobiont components. Cortex – the lichen's outer layer(s), made up of tightly woven fungal filaments. Isidium (pl. isidia) – outgrowths of the thallus which contain photobiont cells and provide means of vegetative reproduction for some lichens. Medulla – a loose layer of interwoven fungal hyphae within the thallus. Podetium (pl. podetia) – an upright secondary thallus, which supports the fruiting bodies of Cladonia species.

Ecology

Symbiosis in lichens – the relationship between the lichen partners can be complicated; while generally mutualistic, sometimes it is not. Recent research also shows other partners, including bacteria and "accessory" fungi, may be involved. Asexual reproduction in lichens – many lichens reproduce asexually, using one or more of various methods which allow the dispersal of bundles of both fungal hyphae and photobionts. Sexual reproduction in lichens – most lichens reproduce sexually using ascospores, which means they have to acquire their photobiont partners somehow after germinating. Lichens and nitrogen cycling – some lichens (in particular those with cyanobacteria as a photobiont) can fix nitrogen. Lichen biogeography – the study of the current distribution of extant lichens and the reasons for those distributions. Lichen resynthesis – lichens can be artificially "recreated" by combining partners in a lab. Lichens and pedogenesis – lichens contribute to the formation of soil by breaking down rock. Biological soil crust – lichens are among the common dominant biota in biocrusts, one of the world's largest environmental community types in terms of area covered. Photosynthesis in lichens

Types of lichens

Lichen taxonomical classifications

Lichen systematics – Although they are composite organisms, lichens have traditionally been classified on the basis of their fungal partner. These span eight different biological classes, 39 orders, 117 families, and around 1,000 genera.

Ascolichen – a lichen whose fungal partner is a member of the Ascomycota, one of the two main fungal divisions. Basidiolichen – a lichen whose fungal partner is a member of the Basidiomycota, the other of the two main fungal divisions; these are far fewer in occurrence than ascolichens.

Classes

Lichens fall into eight fungal classes and several subclasses:

Orders

They are split across nearly 40 orders. Those which cannot be assigned to a particular order are assigned instead to "incertae sedis" within the appropriate class. These orders were listed in Lücking, Hodkinson and Leavitt's 2016 treatise on the classification of lichenized fungi, except where otherwise noted, with orders updated in 2021.

Families

They fall into 117 families. Those which cannot be assigned to a particular family are assigned instead to "incertae sedis" within the appropriate order. These were listed in Lücking, Hodkinson and Leavitt's 2016 treatise on the classification of lichenized fungi, except where otherwise noted; families were updated in 2021.

Genera

… excerpt ends here. Continue reading the full article.

Illustrations

Outline of lichens: Usnea filipendula – one of about 20,000 described species of lichen
Usnea filipendula – one of about 20,000 described species of lichen
Outline of lichens: Schematic cross section of foliose lichen: (a) The cortex is the outer layer of tightly woven fungal filaments (hyphae) (b) This photobiont layer has photosynthesizing green algae (c) Loosely packed hyphae in the medulla (d) A tightly woven lower cortex (e) Anchoring hyphae called rhizines, where the fungus attaches to the substrate
Schematic cross section of foliose lichen: (a) The cortex is the outer layer of tightly woven fungal filaments (hyphae) (b) This photobiont layer has photosynthesizing green algae (c) Loosely packed hyphae in the medulla (d) A tightly woven lower cortex (e) Anchoring hyphae called rhizines, where the fungus attaches to the substrate
Outline of lichens: Lichens with a cyanobacteria as the photosynthetic partner, like this Peltigera collina, can fix nitrogen.[26]
Lichens with a cyanobacteria as the photosynthetic partner, like this Peltigera collina, can fix nitrogen.[26]
Outline of lichens: Chaenotheca brunneola falls into Coniocybomycetes, a small fungal class which contains only a handful of lichen species.[34]
Chaenotheca brunneola falls into Coniocybomycetes, a small fungal class which contains only a handful of lichen species.[34]
Outline of lichens: Lecidella elaeochroma is a member of Lecanorales, the fungal order which contains the greatest number of lichen species.[38]
Lecidella elaeochroma is a member of Lecanorales, the fungal order which contains the greatest number of lichen species.[38]

Worked examples

Example 1 — a first encounter with Outline of lichens

Start with the simplest possible case. Write down what Outline of lichens claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Outline of lichens before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Outline of lichens ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Outline of lichens

In research
Outline of lichens appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Outline of lichens in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Outline of lichens is common in secondary-school and first-year university syllabi. It links to neighbouring topics Lichens, Outlines, Outlines of biology, so understanding it makes those chapters shorter.
In everyday life
Look for Outline of lichens outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Outline of lichens in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Outline of lichens means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Outline of lichens out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Outline of lichens in simple terms?

The following outline provides an overview of and topical guide to lichens. Lichens are composite organisms made up of multiple species.

Why does Outline of lichens matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Outline of lichens?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Outline of lichens.

Tags

  • Lichens
  • Outlines
  • Outlines of biology

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