Lichen

2018-05-10T21:02:48Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)

''Crustose lichen'' are lichen that are pressed against their substrate. They form a crust over their substrate. (6) Their medulla is in direct contact with the substrate it is growing on. (7)
[[File:Crustose lichen.jpg|center|thumb|Crustose Lichen (7)]]

''Squamulose lichen'' are lichen with thallus that is small, flat, usually massed with overlapping scales, or squamules. (7)
[[File:Squamulose lichen.jpg|center|thumb|Squamulose Lichen (7)]]

''Foliose lichen'' are lichen with a thallus that generally forms flat, leaf like lobes, with differentiated layers of tissue. The lower cortex is typically a different color and usually has rhizines to attach to it's substrate. (7)
[[File:Foliose lichen.jpg|center|thumb|Foliose Lichen (7)]]

''Fruticose Lichen'' are lichen with a thallus that is extended up into a tufted or pendant branched structure. (7) They are free-standing branched tubes.(5)
[[File:Fruticose lichen.jpg|center|thumb|Fruticose Lichen (7)]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3) The majority of the lichen's body is formed by filaments from the fungal body, and the varying density of these filaments defines the layers of the lichen. (5)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The filaments in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3) The densely packed filaments also helps to reduce the intensity of light, which can cause damage to the alga cells. (5)
==Symbiont Layer==
Below the cortex, the fungal filaments are not so dense. This is the layer where the aglal cells are distributed. (5) This is the layer than photosynthesis occurs in.
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

[6] https://www.fs.fed.us/wildflowers/beauty/lichens/biology/growthforms.shtml

[7] http://www.lichens.lastdragon.org/faq/lichenthallustypes.html

Lichen

2018-05-10T20:56:16Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)

''Crustose lichen'' are lichen that are pressed against their substrate. They form a crust over their substrate. (6) Their medulla is in direct contact with the substrate it is growing on. (7)
[[File:Crustose lichen.jpg|center|thumb|Crustose Lichen (7)]]

''Squamulose lichen'' are lichen with thallus that is small, flat, usually massed with overlapping scales, or squamules. (7)
[[File:Squamulose lichen.jpg|center|thumb|Squamulose Lichen (7)]]

''Foliose lichen'' are lichen with a thallus that generally forms flat, leaf like lobes, with differentiated layers of tissue. The lower cortex is typically a different color and usually has rhizines to attach to it's substrate. (7)
[[File:Foliose lichen.jpg|center|thumb|Foliose Lichen (7)]]

''Fruticose Lichen'' are lichen with a thallus that is extended up into a tufted or pendant branched structure. (7) They are free-standing branched tubes.(5)
[[File:Fruticose lichen.jpg|center|thumb|Fruticose Lichen (7)]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3) The majority of the lichen's body is formed by filaments from the fungal body, and the varying density of these filaments defines the layers of the lichen. (5)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The filaments in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3) The densely packed filaments also helps to reduce the intensity of light, which can cause damage to the alga cells. (5)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

[6] https://www.fs.fed.us/wildflowers/beauty/lichens/biology/growthforms.shtml

[7] http://www.lichens.lastdragon.org/faq/lichenthallustypes.html

Lichen

2018-05-10T20:52:44Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)

''Crustose lichen'' are lichen that are pressed against their substrate. They form a crust over their substrate. (6) Their medulla is in direct contact with the substrate it is growing on. (7)
[[File:Crustose lichen.jpg|center|thumb|Crustose Lichen (7)]]

''Squamulose lichen'' are lichen with thallus that is small, flat, usually massed with overlapping scales, or squamules. (7)
[[File:Squamulose lichen.jpg|center|thumb|Squamulose Lichen (7)]]

''Foliose lichen'' are lichen with a thallus that generally forms flat, leaf like lobes, with differentiated layers of tissue. The lower cortex is typically a different color and usually has rhizines to attach to it's substrate. (7)
[[File:Foliose lichen.jpg|center|thumb|Foliose Lichen (7)]]

''Fruticose Lichen'' are lichen with a thallus that is extended up into a tufted or pendant branched structure. (7) They are free-standing branched tubes.(5)
[[File:Fruticose lichen.jpg|center|thumb|Fruticose Lichen (7)]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

[6] https://www.fs.fed.us/wildflowers/beauty/lichens/biology/growthforms.shtml

[7] http://www.lichens.lastdragon.org/faq/lichenthallustypes.html

2018-05-10T20:48:30Z

Jleidner:

Lichen

2018-05-10T20:48:17Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)

''Crustose lichen'' are lichen that are pressed against their substrate. They form a crust over their substrate. (6) Their medulla is in direct contact with the substrate it is growing on. (7)
[[File:Crustose lichen.jpg|center|thumb|Crustose Lichen (7)]]

''Squamulose lichen'' are lichen with thallus that is small, flat, usually massed with overlapping scales, or squamules. (7)
[[File:Squamulose lichen.jpg|center|thumb|Squamulose Lichen (7)]]

''Foliose lichen'' are lichen with a thallus that generally forms flat, leaf like lobes, with differentiated layers of tissue. The lower cortex is typically a different color and usually has rhizines to attach to it's substrate. (7)

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

[6] https://www.fs.fed.us/wildflowers/beauty/lichens/biology/growthforms.shtml

[7] http://www.lichens.lastdragon.org/faq/lichenthallustypes.html

Lichen

2018-05-10T20:44:12Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)

''Crustose'' lichen are lichen that are pressed against their substrate. They form a crust over their substrate. (6) Their medulla is in direct contact with the substrate it is growing on. (7)
[[File:Crustose lichen.jpg|center|thumb|Crustose Lichen (7)]]

''Squamulose'' lichen are lichen with thallus that is small, flat, usually massed with overlapping scales, or squamules. (7)
[[File:Squamulose lichen.jpg|center|thumb|Squamulose Lichen (7)]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

[6] https://www.fs.fed.us/wildflowers/beauty/lichens/biology/growthforms.shtml

[7] http://www.lichens.lastdragon.org/faq/lichenthallustypes.html

Lichen

2018-05-10T20:43:53Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

[[File:Lichen.jpg|center|250px]]
[[File:Lichen 1.jpg|center|250px]]
[[File:03a Lichen, orange fruits Irongate July 2010.jpg|center|250px]]
[[File:Lichen-usnea-subfloridana-alamy-h7thg8-580x435.jpg|center|250px]]

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)

''Crustose'' lichen are lichen that are pressed against their substrate. They form a crust over their substrate. (6) Their medulla is in direct contact with the substrate it is growing on. (7)
[[File:Crustose lichen.jpg|center|thumb|Crustose Lichen (7)]]

''Squamulose'' lichen are lichen with thallus that is small, flat, usually massed with overlapping scales, or squamules. (7)
[[File:Squamulose lichen.jpg|center|thumb|Squamulose Lichen (7)]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

[6] https://www.fs.fed.us/wildflowers/beauty/lichens/biology/growthforms.shtml

[7] http://www.lichens.lastdragon.org/faq/lichenthallustypes.html

2018-05-10T20:37:40Z

Jleidner:

Lichen

2018-05-10T20:37:22Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

[[File:Lichen.jpg|center|250px]]
[[File:Lichen 1.jpg|center|250px]]
[[File:03a Lichen, orange fruits Irongate July 2010.jpg|center|250px]]
[[File:Lichen-usnea-subfloridana-alamy-h7thg8-580x435.jpg|center|250px]]

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)
[[File:Lichen types.jpg|center|400px|]]

''Crustose'' lichen are lichen that are pressed against their substrate. They form a crust over their substrate. (6) Their medulla is in direct contact with the substrate it is growing on. (7)

''Squamulose'' lichen are

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

[6] https://www.fs.fed.us/wildflowers/beauty/lichens/biology/growthforms.shtml

[7] http://www.lichens.lastdragon.org/faq/lichenthallustypes.html

Lichen

2018-05-10T20:29:50Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

[[File:Lichen.jpg|center|250px]]
[[File:Lichen 1.jpg|center|250px]]
[[File:03a Lichen, orange fruits Irongate July 2010.jpg|center|250px]]
[[File:Lichen-usnea-subfloridana-alamy-h7thg8-580x435.jpg|center|250px]]

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)
[[File:Lichen types.jpg|center|400px|]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

Lichen

2018-05-10T20:29:36Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

[[File:Lichen.jpg|center|250px]]
[[File:Lichen 1.jpg|center|250px]]
[[File:03a Lichen, orange fruits Irongate July 2010.jpg|center|250px]]
[[File:Lichen-usnea-subfloridana-alamy-h7thg8-580x435.jpg|center|250px]]

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)
[[File:Lichen types.jpg|center|250px|(5)]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

Lichen

2018-05-10T20:24:06Z

Jleidner:

Lichen is a compound organism, made up of two species. A fungus and a cyanobacteria or green algae live symbiotically, and both are benefited from this mutualistic relationship. In exchange for a safe habitat to live in, the cyanobacteria or green algae provide food to the fungus from their photosynthetic processes. (1) The body of a lichen is a thallus, or a plant body that is not differentiated into stems and leaves, and lacks roots and a vascular system.

[[File:Lichen.jpg|center|250px]]
[[File:Lichen 1.jpg|center|250px]]
[[File:03a Lichen, orange fruits Irongate July 2010.jpg|center|250px]]
[[File:Lichen-usnea-subfloridana-alamy-h7thg8-580x435.jpg|center|250px]]

=Types of Lichen=
Lichen occur in one of four growth forms. These include crustose, squamulose, foliose, and fruticose. (5)
[[File:Lichen types.jpg|center|250px]]

=Biology=
Unlike plants, lichen do not have a vascular system. This means they do not have a xylem or phloem to move nutrients and water around their plant body. Lichen get their water and nutrients by absorbing them from their surroundings. (3)
[[File:Lichenn.jpg|center|250px]]
==Cortex==
The outer layer of the lichen is called the cortex. The cells in the cortex are thicker and more closely packed, providing a small amount of protection for the organism. (3)
==Medulla==
Fungal filaments, or medulla, make up most of the lichen organism. Fungal cells are loosely packed in the middle of the lichen body, with thin cell walls and a threadlike structure. (3)
==Attachments==
===Rhizines===
Some lichen use rhizines to attach to their substrate. Rhizines are fungal filaments extending out from the medulla. Rhizines do not move water or help the lichen breathe. Their sole purpose is stabilizing the lichen down. (3)
===Holdfast===
[[File:Holdfast.png|thumb]]

Some lichen use holdfasts to fasten themselves down. This is a central peg that extends out from the lichen thallus. (3)

=Ecology=
Lichen play a huge role in the development of ecosystems, and also a huge role in established ecosystems. They play an important role in the water cycle in forests, greatly increasing the interception and absorption of precipitation. (4) Lichen are able to sequester limiting nutrients from the atmosphere, and these in turn become available to other organisms when lichen die, fall, and decompose, or through leachate. (4) The presence of lichen also provides increased habitat complexity for small organisms. There is a close relationship between lichen and invertebrates, including Arachnids such as orabitid [[mites]], insects, [[rotifers]], [[tardigrades]], and spiders. (4) Providing habitat for these micro organisms is the base of the food chain, and provides food sources for the rest of the food web.
=Pioneer Species=
Lichen are considered pioneer species, or the first organism to appear in areas of primary succession. (2) They are able to colonize bare rocks, and an ecosystem is then able to begin developing on them.
=Indication=
An indicator species is a species that tells something about the environment by their presence, or absence, in that environment. Lichens are indicators of environmental pollution. They have no way to detoxify and excrete harmful chemicals from the air, so absence of lichen in an ecosystem can be an indicator of environmental stress due to pollution. (1)

=References=
[1] Lewis, Ricki. "Lichen." Biology, edited by Melissa Sue Hill, 2nd 2d., vol. 3, Macmillan Reference USA, 2016, pp 12-13. Science in Context

[2] Discovery Education Science, Primary and Secondary Succession

[3] “Lichen Biology.” Lichen Biology - Structure, www.fs.fed.us/wildflowers/beauty/lichens/biology/index.shtml.

[4] Ellis, Christopher J. “Lichen Epiphyte Diversity: A Species, Community and Trait-Based Review.” Perspectives in Plant Ecology, Evolution and Systematics, vol. 14, no. 2, 2012, pp. 131–152., doi:10.1016/j.ppees.2011.10.001.

[5] http://www.ucmp.berkeley.edu/fungi/lichens/lichenmm.html

2018-05-09T15:13:56Z

Jleidner:

Diazotrophs are a group of [[prokaryotic organisms]] with the ability to fix atmospheric nitrogen into ammonium or ammonia, forms usable to plants. There are two types of terrestrial diazotrophs: those free living in the soil, and those that form [[symbiotic relationships]] with plants.

[[File:nitrogen cycle.jpg|thumb|right|400px|This photo depicts the complete nitrogen cycle. The diazotrophs are the organisms labeled "nitrogen-fixing bacteria in root nodules of legumes" and "nitrogen-fixing soil bacteria" [8].]]

Nitrogen makes up the majority of the Earth’s atmosphere, but is mostly found in a form unusable to organisms. Atmospheric nitrogen (N2) is found as two nitrogen atoms held together by a triple bond. In this form, nitrogen is inaccessible. Diazotrophs have the ability to split, or “fix” these bonds, freeing the nitrogen molecules. This is crucial to the Earth's ecosystem. Nitrogen lost to anaerobic ammonium oxidation and denitrification need to be replenished to maintain the right amount of biologically available nitrogen in the soil.

The ''nif''H gene is used as an indicator of a diazotroph. It is a gene that encodes for the enzyme that is needed for the reduction of nitrogen, nitrogenase. Oxygen is harmful for this enzyme, so diazotrophs find ways to protect this. They often live in anaerobic environments, including in the roots of a plant or in soils.

==The ''nif''H gene==
Diazotrophs are a group of organisms made up of [[Proteobacterias]], [[Cyanobacterias]], and [[Archeans]]. Nitrogen fixing organisms are very diverse, both physiologically and phylogenetically. The ''nif''H gene is used as a biomarker to identify diazotrophs. The ''nif''H gene encodes for the enzyme nitrogenase reductase, which facilitates the reduction of nitrogen. This gene is the only one currently being used to identify nitrogen fixing organisms, but the presence of other nitrogen fixing systems in some organisms and multiple copies of the genes within other organisms suggests that it is not always an absolute marker of a diazotroph.

== Free Living Diazotrophs ==
Free living diazotrophs are nitrogen fixing organisms that live directly in the soil. They are able to fix nitrogen by using a nitrogenase protein, which is able to break nitrogen bonding. 16 molecules of ATP, plus 8 reducing equivalents, are required to reduce one molecule of atmospheric nitrogen gas.[4] This is a huge energy investment by the diazotroph. The energy investment needed increases in aerobic areas, because soil dwelling nitrogen fixers need to use a lot of energy to protect their nitrogenase from oxygen's damaging effects. The least costly method of nitrogen fixation for free living diazotrophs is in microaerophilic environments, where there is enough oxygen for the bacteria to breathe, but not enough to harm their nitrogenase enzymes.

===The Rhizosphere===
There are greater populations of diazotrophs found in the [[rhizosphere]] than there are found in bulk soil. This is hypothesized to be due to the fact that, during the vegetation period, the amount of amino acids released by plants does not have sufficient amounts of nitrogen to support the microbial life. This can give diazotrophs an advantage, as they are able to fix their own nitrogen.

Common diazotrophs found in the rhizosphere include ''Azotobacter'', ''Azospirillum'' and ''Herbaspirillum''.

== Symbiotic Diazotrophs ==

[[File:lec18_clip_image006.jpg|thumbnail|The process of nodule formation happening between a bacteria and plant, resulting in a symbiotic relationship. The bacteria fixes nitrogen that will become available to the plant, and the plant provides shelter, carbon, and energy to the bacteria. [9] ]]

The enzymes that are needed to fix nitrogen are easily damaged by oxygen, so some diazotophs form symbiotic relationships with plants. In this relationship, diazaotophs have protection from oxygen's damaging properties, while also being supplied carbon, and energy. In exchange for this, plants benefit from the nitrogen being fixed inside their roots. They do this by living in nodules that form on the roots of plants. Inside these nodules live clusters of bacteria that are able to fix nitrogen without the harmful effects of an open environment. The color of the nodule is indicative of the processes occurring within. Green nodules mean the bacteria are reproducing, pink means they are actively fixing nitrogen, and white means they are transitioning.

The most common plant family that creates symbiotic relationships with diazotrophs is the Fabaceae or Leguminosae family, which includes leguminous plants.

Common symbiotic diazotrophs include bacteria from the genus ''Rhizobium'' and ''Frankia'', among others.

===Nod Factor===

Bacteria from the genus ''Rhizobium'' form a relationship with leguminous plants. Parasponia is the only non-legume genus that can form a symbiotic relationship with these bacteria. They do this by using the nodulation factor, or nod factor - a signal of amino acids that alert the plant. The nod factor is sent out as a response to [[flavonoids]] sent out by leguminous plants. When the bacteria sends out this signal, the plant responds with root hairs curling around the bacteria. As the intracellular infection threads from the bacteria begin to grow into the plants, the plant begins nodule formation. The nodule become surrounded by a membrane from plant material. Symbiosome is the name for this compartmentalization of bacteria within the plant, and it is the symbiosome that acts as the pathway between the plant and the bacteria, allowing for nutrient exchange.

==References==
[1] Streng, Arend, et al. “Evolutionary Origin of Rhizobium Nod Factor Signaling.” Plant Signaling & Behavior, vol. 6, no. 10, 2011, pp. 1510–1514., doi:10.4161/psb.6.10.17444.

[2] Stein, Lisa Y, and Martin G Klotz. “The Nitrogen Cycle.” Current Biology Magazine , vol. 26, no. 3, 8 Feb. 2016, pp. R94–R98.

[3] Jetten, Mike S. M. “The microbial nitrogen cycle.” Environmental Microbiology, vol. 10, no. 11, 2008, pp. 2903–2909., doi:10.1111/j.1462-2920.2008.01786.x.

[4] Norman, Jeffrey S, and Maren L Friesen. “Complex N acquisition by soil diazotrophs: how the ability to release exoenzymes affects N fixation by terrestrial free-Living diazotrophs.” The ISME Journal, vol. 11, no. 2, 1 Feb. 2017, pp. 315–326., doi:10.1038/ismej.2016.127.

[5] Burgmann, Helmut, et al. “Effects of model root exudates on structure and activity of a soil diazotroph community.” Environmental Microbiology, vol. 7, no. 11, 1 Nov. 2005, pp. 1711–1724., doi:10.1111/j.1462-2920.2005.00818.x.

[6] Burgmann, H., et al. “New Molecular Screening Tools for Analysis of Free-Living Diazotrophs in Soil.” Applied and Environmental Microbiology, vol. 70, no. 1, Jan. 2004, pp. 240–247., doi:10.1128/aem.70.1.240-247.2004.

[7] Poulin, Jessica. Evolutionary Biology Lab Manual. 8th ed.

[8] http://ib.bioninja.com.au/options/option-c-ecology-and-conser/c6-nitrogen-and-phosphorus/nitrogen-cycle.html

[9] Pearson Education, Inc