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ENVB 210 > Biosphere I and II > Flashcards

Biosphere I and II Flashcards

1
Q

What is the relationship between soil biota size and abundance?

A

The smaller the biota, the greater the abundance.

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2
Q

What are the three major biomass components in soil?

A

Plants, then bacteria, then fungi

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3
Q

Most of the diversity in soil comes from […]

A

Bacteria and fungi

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4
Q

Why is soil biodiversity so high?

A

There is small-scale heterogeneity in resources, microclimates, oxygen, and water. This creates high microhabitat diversity and many niches, thus promoting diversity.

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5
Q

Name 4 specific attributes of soil bacteria that support high biodiversity.

A
  1. Fast growth rates and high dispersal rates
  2. Rapid rates of evolution and speciation
  3. Dormancy
  4. Adapted to live in extreme environments.
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6
Q

When comparing a sand, silt, and clay soil, which texture would you expect to support the most diverse microbial community? Why?

A

The clayey soil, as there are micropores, and the poor drainage might create microclimates based on anaerobic/aerobic conditions.

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7
Q

Which domains of life are found in soil?

A

All 3: bacteria, archaea, eukarya

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8
Q

Describe the appearance of fungi in soil.

A

They have thread-like hyphae that extend throughout the soil.

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9
Q

Are fungi aerobic, anaerobic, or both?

A

They are exclusively aerobic.

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10
Q

Describe the appearance of bacteria in soil.

A

They are smaller than fungi and are often rod shaped.

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11
Q

Are bacteria aerobic, anaerobic, or both?

A

They can be aerobic or anaerobic depending on the species.

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12
Q

What do fungi and bacteria use to grow?

A

They all require organic carbon to increase their biomass.

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13
Q

In the meta-analysis we looked at, how did reduced-till and no-till affect overall fungi vs bacterial communities?

A

In fungi, no-till and reduced-till had a dramatic positive effect on biomass. In bacteria, the effect was still positive, but much smaller.

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14
Q

In the meta-analysis we looked at, how did soil depth affect the impact of no and reduced till on fungi and bacteria?

A

In both cases, it increased biomass at the surface but decreased biomass in the subsurface soil. This is because the lack of tillage preventing OC from being mixed into the deeper layers.

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15
Q

What are phototrophs?

A

Organisms that obtain energy derived from solar radiation.

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16
Q

What are chemotrophs?

A

Organisms that obtain energy from biochemical oxidation (organic or inorganic compounds)

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17
Q

What are autotrophs?

A

Organisms that obtain their carbon from CO2 gas.

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18
Q

What are heterotrophs?

A

Organisms that obtain their carbon from the breakdown of organic materials.

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19
Q

What are photoautotrophs? What types of organisms can they be?

A

Plants, algae and cyanobacteria: use H2O to reduce CO2 and produce O2 as a byproduct
Photosynthetic green and purple sulfur bacteria: reduce CO2 but not using H2O and not to produce O2

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20
Q

What are chemoautotrophs? What types of organisms can they be?

A

They are hydrogen, sulfur, and nitrifying bacteria (obtain C from CO2 gas).

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21
Q

What are photoheterotrophs? What types of organisms can they be?

A

Green nonsulfur and purple nonsulfur abcteria.

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22
Q

What are chemoheterotrophs? What types of organisms can they be?

A

They respire either aerobically (most animals, fungi, and protozoa, and many bacteria) or anaerobically (some animals, protozoa, and bacteria). Some bacteria and yeasts are also capable of fermentation.

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23
Q

What is the metabolic grouping of humans?

A

We are chemoheterotrophs.

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24
Q

How do cyanobacteria generate their energy?

A

They get their energy from solar radiation and their C from CO2. They essentially undergo photosynthesis and release O as a byproduct.

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25
Q

What is the hypothesized role of cyanobacteria in history?

A

They are thought to have converted the early oxygen-poor, reduced atmosphere into an oxidizing one, which allowed for the emergence of aerobic organisms.

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26
Q

How does CO2 get from the surface to soil microorganisms and back?

A

CO2 starts in plants. They produce reduced organic C compounds, which are used by saphotrophs to produce energy for growth and reproduction. They oxidize the OM and release nutrients that can be used by the plant.

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27
Q

What are saphotrophs?

A

They are heterotrophs that use decaying organic materials as a source of energy, carbon, and nutrients. This is mostly carried out by bacteria and fungi.

28
Q

What 5 conditions affect diversity and abundance of soil biota?

A
  1. Carbon availability
  2. Oxygen, moisture, and temperature
  3. Soil texture
  4. Soil pH
  5. Nutrients
29
Q

Explain how carbon availability affects the location of microorganisms in soil.

A

Because there is fierce competition for food among microorganisms, they tend to concentrate closer to the surface where nutrients and carbon are more abundant.

30
Q

What are the 4 major nutrient sources for bacteria? State their abundances.

A
  1. 50% protein (C, H, O, N)
  2. 30% cell wall and lipids (C, H, O)
  3. 10-20% RNA
  4. 3-4% DNA
31
Q

What are the 4 categories of soil organisms?

A

Microbes, microfauna, mesofauna, macrofauna.

32
Q

What size category do the following organisms fall into? Bacteria, fungi, collembola, amphipoda, protozoa, diplura, earthworms

A

Microbes, microbes, mesofauna, macrofuna, microbes, mesfauna, macro or megafauna.

33
Q

What are the ideal growth conditions for bacteria?

A

Move through water films and soil pore water, optimum growth near neutral pH but have a somewhat wide range of temp, O2, and pH ranges compared to fungi.

34
Q

What are the ideal growth conditions for fungi?

A

They are always aerobic (require O2) and prefer slightly acidic soils.

35
Q

Describe the structure of fungi in the soil.

A

They form fungal hyphae, which are long filaments making up the fungus that are very sensitive to disturbance.

36
Q

What is the purpose of fungal hyphae?

A

To translocate cellular material and growth resources throughout the soil.

37
Q

What is lignin? Describe its major characteristics.

A

It is the structural part of plants, like bark or stems. It can only be digested by some fungi, as it is made up of many aromatic rings, making it hard to break down.

38
Q

What are fungi necessary in wooded environments?

A

Because they are the only ones who can break down lignin, which typically contains the energy-rich cellulose. So fungi must break down the lignin before bacteria can access the cellulose.

39
Q

How do fungi and bacteria differ in terms of metabolism?

A

All fungi are heterotrophs and most are saphotrophic, while bacteria can have a variety of metabolic pathways.

40
Q

How do fungi and bacteria differ in terms of biomass size?

A

Bacterial biomass in soil is much larger than fungal because of their fast turnover rate and death.

41
Q

How do fungi and bacteria differ in terms of nutrient demand?

A

Bacteria have higher N and P demands.

42
Q

How do fungi and bacteria differ in terms of movement?

A

Fungi move by growing new mycelium, and dispersal occurs through sporulation and soil fauna. Bacteria have motile organelles to move through water films.

43
Q

Compare the C:N ratio of fungi vs bacteria and explain what the difference means in terms of abundance.

A

Bacteria have a C:N ratio of 4, while fungi have a C:N ratio of 16. This means that bacteria require more N than fungi, so bacteria will tend to dominate over fungi in N-rich environments rather than in N-poor environments, where fungi might dominate.

44
Q

How do the abundances of fungi and bacteria compare with the addition of alfalfa vs straw? Why?

A

Bacteria are dominant when alfalfa is added, as alfalfa is rich in nitrogen. On the other hand, fungi are dominant when straw is added, as straw is nitrogen-poor which suits fungi better.

45
Q

How does the fungal:bacterial ratio change over the course of decomposition? Why?

A

It decreases. This is because at first, more fungi are needed to break down lignin. Once this is done, more bacteria are needed to access and break down the cellulose.

46
Q

How does species richness of bacteria change over the course of decomposition? Why?

A

It increases over time, as at the start few bacteria are needed because there’s still lignin to be broken down by fungi before most bacteria are useful.

47
Q

How does species richness of fungi change over the course of decomposition? Why?

A

It peaks midway through and then decreases, as after all the lignin has been broken down, fungi become less relevant players in decomposition.

48
Q

Where are fungal:bacterial ratios the highest globally? Why?

A

They are highest in the northernmost latitudes. This is because these soils tend to be more acidic and lacking in nitrogen

49
Q

How is F:B ratio affected by highly aggregated soil vs low aggregation?

A

The F:B ratio is higher in highly aggregated soil, as aggregation is a sign of fungal hyphae.

50
Q

How is F:B ratio affected by conventional tillage vs no tillage?

A

F:B ratio is lower in conventional tillage, as the tillage will disrupt fungal hyphae.

51
Q

How is F:B ratio affected by a more aerobic environment?

A

It increases, because fungi are exclusively aerobic and will thus benefit more from the oxygen than bacteria.

52
Q

How is F:B ratio affected by more soil moisture?

A

It decreases, as bacteria prefer wetter environments while fungi prefer drier environments.

53
Q

How is F:N ratio affected by slightly acidic soil vs higher pH soil?

A

It will increase, because fungi prefer slightly acidic soils while bacteria prefer more neutral pH.

54
Q

How is F:N ratio affected by an annual plant community vs a perennial plant community?

A

It will decrease, because there is higher nitrogen turnover in annual plants communities, which favours bacteria which have higher nitrogen needs.

55
Q

How is F:N ratio affected by a grassland/agriculture ecosystem vs a forest ecosystem?

A

It will decrease in a grassland ecosystem, because fungi are more needed in forests where there is more lignin to break down.

56
Q

How is F:N ratio affected by being in a litter layer vs a mineral horizon?

A

It will increase in a little layer because there will be branches with lignin to break down, necessitating more fungi.

57
Q

What types of environments do archaea typically live in?

A

They are extremophiles, so they live in extreme, highly specialized environments.

58
Q

What types of organisms are included in soil fauna?

A

The eukaryotic micro to macro soil animals.

59
Q

Name 6 functional roles of soil fauna.

A
  1. Predation: grazing on microbes (regulation of population dynamics)
  2. Nutrient cycling
  3. Comminution: fragmentation of material
  4. Can be vectors for parasites and disease
  5. Pathogen suppression: consumption of herbivores and weed seeds
  6. Translocation: movement of materials and of microbes
60
Q

What are the 3 major categories of soil fauna? How big are each?

A

Microfauna (<100 micrometers), mesofauna (100 micrometers to 2 mm), and macrofauna (> 2mm).

61
Q

What are the major functions of microfauna in soil?

A

They are grazers and predators of microorganisms.

62
Q

What are the 3 major feeding preferences of microfauna?

A

Herbivorous: eat live plant roots
Detritivores: eat dead and decomposing plant, animal, and microbial materials
Parasites: eat parasites (especially plant parasites)

63
Q

What effect does microfauna grazing have on nutrient cycling?

A

It increases nitrogen mineralization and aids in the retention of nutrients in biomass.

64
Q

What is the microbial loop?

A

It is part of the effect of microbial predation on nutrient cycling. The predation of microbes by microfauna produces NH4, which is used by microbes, then they are further consumed by microfauna. The predation leads to an increased turnover rate of bacteria.

65
Q

Predation regulates the […] and […] of microbial biomass in the soil.

A

Size, activity

ENVB 210 (16 decks)

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