Lecture 4 - Exam 2 : Organisms in the Soil Flashcards
What are some examples of fruiting bodies?
Meadow mushroom, black morel, and truffles
Describe the morphology of fungi.
Unicellular or multicellular ; most are filamentous ; contain hyphae 2-30 um in diameter and conform a network called mycelium. These mycelium can either be undifferentiated (filamentous) or fruiting bodies (differentiated). They have a cell wall with chitin (except oomycetes they have cellulous instead).
What are the different types of fungi that have different metabolisms?
Heterotrophs: Organic carbon as carbon source, and organic compounds as energy source. An example: saprophytes which feed on dead material, important for complex organic matter decay
Symbionts: Algae and cyanobacteria have symbiotic relationship with fungi and plants.
Pathogens: Example is endophytes which live inside the plants and can cause problems.
Describe the reproduction of fungi.
Fungi have complex reproduction cycles. There are asexual and sexual spores. Sexual reproduction produces sexual spores and asexual reproduction produces asexual spores. There is also hyphal fragmentation.
What are examples of asexual spores?
Conidia of Penicillium chrysogenum.
Chlamydospores and Sporangia of Phytophthora ramorum.
Zoospores produced by oomycetes (zoospores can have 1 or 2 flagella).
What are examples of sexual spores?
Oospore of Phytophthora ramorum.
Ascospores and Basidiospores.
*Zygospores released by Zygosporangia of Rhizopus nigricans.
What is the sexual and asexual phase of Chytridiomycetes?
Sexual phase: Chytrid cells
Asexual phase: Zoospores
What is the sexual and asexual phase of Zygomycetes?
Sexual phase: Zygospores
Asexual phase: Chlamydospores & sporangiospores
What is the sexual and asexual phase of Arbuscular mycorrhizae?
Sexual phase: Absent
Asexual phase: azygospores
What is the sexual and asexual phase of Ascomycetes?
Sexual phase: Ascospores
Asexual phase: Conidia
What is the sexual and asexual phase of Basidiomycetes?
Sexual phase: Basidiospores
Asexual phase: Chlamydospores & Conidia
What is the sexual and asexual phase of Oomycetes?
Sexual phase: Oospores
Asexual phase: Sporangia & Zoospores
What are the two fungi that have septate hyphae?
Ascomycetes and Basidiomycetes
Every other one is Aseptate hyphae
Which fungi is unicellular?
Oomycetes
What are the two symbiotic relationships?
Lichens: Symbiotic association of a fungus with an alga or a cyanobacteria. Also, ascomycetes and green algae.
Mycorrhizae (fungus root): Symbiotic association between plant roots and fungi.
Note: Plants benefit because they get the water that the fungi bring in. Fungi benefit because plants carry out photosynthesis and produce a carbon source.
What are the types of mycorrhizal association?
Ectomycorrhizae, Arbuscular mycorrhizae, Ericaceous mycorrhizae, and Orchidaceous mycorrhizae.
Ectomycorrhizae
Presence of hyphae between root cortical cells.
Fungi and plants involved.
Fungi: basidiomycetes mostly
Plants: woody perennials (like pine trees)
Arbuscular mycorrhizae
Form highly branched structures within root cortical cells; no apparent change of root appearance.
Fungi and plants involved.
Fungi: members of Glomeromycota
Plants: 90% of vascular plants
Special structures: Arbuscules and vesicles. Auxiliary cells and spores.
Ericaceous mycorrhizae
Only in plant order of Ericales, penetrate cortical cells but no arbuscule formation.
Orchidaceous mycorrhizae
In Orchid family, important for seedlings, form hyphal coil inside a cell.
What are the three special structures that ectomycorrhizae form?
Hartig net (net-like structure), mantle (thick layer of fungal tissue covering root surface), and rhizomorphs (fungal hyphae that extends into soil and form aggregates in strands).
Discuss the mutual benefits in the mycorrhizal symbiosis.
It is overall more beneficial to plants. Fungi receive a carbon source from plants and plants may supply growth factors. Plants get a boat-load of things like increased uptake of phosphorous and increased drought resistance.
Mycorrhizae means what?
Fungus root
When the soil is wet, you can tell what?
You can tell if there is good soil structure because the aggregates will still remain.
What is the substance that coats the spores and hyphae?
Glomalin, a gooey glycoprotein excreted by mycorrhizal fungi.
What are the factors affecting AMF colonization?
Positive: no soil disturbances, host plants present, living roots all year round, low soil fertility
Negative: High P, excess water, and fungicides
Is there such thing as below ground plant communication?
Yes. Plants can produce volatile organic compounds and then that’s released by leaves above ground. They can communicate with their neighbors and warn them of there is an insect attack or something. Recently, mycorrhizal fungi have been found to help this below ground communication. For ex: during a drought, plants experience symptoms and will release chemicals and will be diffused through the mycorrhizal fungi network and warn neighbors.
Have scientists made computers and motherboards using fungi?
Yes!
Are algae eukaryotes?
Yes! Cyanobacteria are prokaryotes, not algae.
Describe the component of soil biota: Algae.
Are oxygenic phototrophs, meaning they produce oxygen. They carry out photosynthesis via chloroplasts. They can me unicellular or multicellular & live wherever there is the most light.
What are the three groups of algae?
Green algae, diatoms, and yellow-green algae.
What are the key characteristics of green algae?
Pigments: Chlorophyll a & b
Storage products: Starch and oil
Cell wall: Cellulose
Reproduction: Sexual and asexual
What are the key characteristics of diatoms?
Pigments: Chlorophyll a &c, carotenoids
Storage products: Chrysolaminarin & oil
Cell wall: Silica and pectin
Reproduction: Asexual
What are the key characteristics for yellow-green algae?
Pigments: Chlorophyll a & c, carotenoids
Storage products: Chrysolaminarin & oil
Cell wall: Cellulose and pectin
Reproduction: Asexual
Which of the types of algae can be unicellular or filamentous?
Green algae and yellow-green algae (diatoms are usually just unicellular)
Describe the shape of diatoms.
They have a unique shape and have two halves. The two halves form the structure we call a frustule.
Describe protozoa.
Most are found in the rhizosphere. 10^3-10^5 per gram of soil. They are unicellular, motile, heterotrophic and predaceous, they reproduce asexually (binary fission) and sexually. There are three groups: flagellates, amoebae, and ciliates. These groups are classified according to the way they move and their morphology.
Flagellates have ________ and move via _______ being propelled.
Flagella ; flagella
Amoeba move by means of _______… they move by expanding and contracting their _______.
pseudopodia ; protoplasm
There are two types of amoeba: _______ and ______. Which type is mostly found in the soil?
Naked (no hard shell) ; tested (have hard shell).
Naked are generally found in the soil.
Ciliate have _________ on their cell surface and move by doing what to these things?
How big are ciliates?
Short hair; they move by beating the short hairs.
Ciliates are much larger. They need a lot of water in order to be abundant. Need water film thicker than 30 um.
How do protozoa prey and feed?
They are phagotrophic, meaning they feed by engulfing.
What do flagellates and ciliates prey on?
Bacteria, yeasts, protozoa, and rotifiers
What do Amoeba prey on?
Bacteria, yeasts, protozoa, algae, and spores
What are the factors affecting protozoa?
Pore dimension and water content (they like to have a lot of water)
What are the ecological function of protozoa?
Regulate the size and composition of microbial community, accelerate microbial biomass and soil organic matter turnover, release nutrients, and transport other microbes.
Describe Nematodes.
Are also called round worms and are eukaryotic and multicellular. 5-100 um wide ; 0.1-1 mm long. Reproduce by laying eggs, and are predators. They prey on plant roots, bacteria, fungi, protozoa, algae, and other nematodes.
How are nematodes generally identified?
By their mouth piece (stylist) and what they feed on.
How are the nematodes in the soil living? Do they cause problems? Do they play roles in the ecosystem?
They are generally free-living and not causing problems. They play important roles in the soil ecosystem, similar to protozoa.
Describe Earthworms.
Much larger than nematodes. About 10 cm long. Three major groups: Epigeic (upon the Earth), Anecic (out of the earth), and Endogeic (in the earth).
What are Anecic Earthworms?
Make vertical burrows and come out at night and drag litter into their burrow. Ex: Nightcrawlers. Medium, dorsal pigmentation
What are Epigeic Earthworms?
They live on top of soil on litter layer. Ex: Red worms
Often heavy pigmentation
What are Endogeic Earthworms?
Make horizontal burrows in the soil. Don’t really come out of the soil. They ingest soil and soil organic matter.
Unpigmented or light pigmented
What is the ecological significance of earthworms?
Litter decomposition, soil mixing, soil aggregate stability, casts, macropores
What are the factors affecting earthworm activity?
Moisture and aeration, organic matter, temperature… If the temperature is too hot, then they become dormant so that’s what we call aestivation.
Are there other macroorganisms in the soil?
Yes! Like mites and rotifer
What is the ecological importance of fauna?
Accelerate organic matter decomposition, mix soil, release N in feces, transport microorganisms, aid in soil aggregation and aeration
If we were to wipe Earthworms out, would they come back quickly?
No, they move very slow and would come back slowly
Describe Viruses.
Viruses are genetic elements that can replicate independently of a cell’s chromosomes but not independently of cells themselves. They are acellular intracellular inhabitants and have no metabolism of their own. Without a host, they’re screwed!
What are the different definitions of living organisms?
Autopoiesis (they make themselves), evolution by natural selection, and autopoietic systems capable of evolution by natural selection. If we use the definition of autopoiesis, then viruses are not living, but if we use the evolution criteria then they are living.
What are the structural components of viruses?
Capsid and genome
What are the shapes that viruses can have?
Cubical, helical or filamentous, and binal (it has cubical head and a long filamentous tail)
Most viruses are what shape?
Binal, like a bacteriophage
How do we classify bacteria?
Based on their hosts: Bacteria, fungi, insects, plants and animals
and based on genetic materials: DNA and RNA (most cold and flu viruses are RNA viruses)
What are the life cycles of bacteriophages?
Lyric (virulent) and Lysogenic (temperate)
What is the ecological importance of viruses?
Genetic material exchange between bacterial cells (transduction), control bacterial population sizes, soil is a reservoir for viruses.
What are the other two ways that genetic material can be exchanged?
Transformation (uptake of free dna into bacterial cell) and conjugation (cell to cell contact)
What causes viruses to lose their infection ability?
Low humidity and high temperature.
