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Ecosystems Flashcards

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1
Q

What is an ecosystem?

A

A natural system consisting of all plants, animals, and microorganisms (biotic) factors in an area functioning together with all the non-living (abiotic) aspects of the environment

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2
Q

What is a biotic factor?

A

A living, biological factor that may influence an organism or a system

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3
Q

Give three examples of a biotic factor

A

predation, disease, competition

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4
Q

What is an abiotic factor?

A

A non-living, physical factor that may influence an organism or a system

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5
Q

Give three examples of an abiotic factor

A

Temperature, salinity, and light

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6
Q

What provides most of the energy for all ecosystems?

A

Solar energy

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7
Q

What are autotrophs?

A

Producers of complex organic molecules using energy from light

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8
Q

What are heterotrophs?

A

Consumers who cannot fix carbon but use organic carbon for growth

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9
Q

What are saprotrophs?

A

Decomposers break down dead organisms

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10
Q

What is the trophic structure?

A

The transformation and transfer of energy from one trophic level to the next is inefficient so some energy is lost at each level

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11
Q

Give an example of a limiting factor

A

When there too much or too little light

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12
Q

What is succession?

A

The process of change by which biotic communities replace each other and by which the physical environment becomes altered over time.

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13
Q

Is succession predictable and directional?

A

Yes.

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14
Q

What are the types of succession?

A

*Autogenic succession
*Allogenic succession
*Biogenic succession
*Primary succession
*Secondary succession
*Seral stage

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15
Q

What is autogenic succession?

A

Driven by changes in physical, chemical, and biotic environment, it is the most common form, e.g., leaf fall

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16
Q

What is allogenic succession?

A

Dominated by external physical processes (abiotic), independent of biotic community changes, e.g., Volcano, flood, silt deposition, etc

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17
Q

What is biogenic succession?

A

A sudden interference with other forms of succession, e.g., a change in herbivore pressure

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18
Q

What is primary succession?

A

Occurs on newly exposed substrate, not yet altered by living organisms, sites devoid of organic matter. This causes an increase in organic matter and nutrients but a decline in pH.

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19
Q

What is secondary succession?

A

The environment is already modified by living organisms, and then re-colonization, re-growth/or germination of recently cleared ground occurs.

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20
Q

What is the seral stage?

A

The characteristic sequence of biotic communities that successively occupy and replace each other in a particular environment over time.

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21
Q

Are plant succession and soil development independent?

A

Yes

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22
Q

What are the three types of moisture regimes?

A

*xerarch = dry
*mesarch = moist
*hydrarch = very wet

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23
Q

What are the three types of nutrient regimes?

A

*oligotrophic (nutrient-poor)
*mesotrophic (moderate nutrient status)
*eutrophic (nutrient-rich)

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24
Q

What is the climax community?

A

The climax community is the final, stable, and self-sustaining ecological community that develops at the end of succession.

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25
What are the four theories of climax communities?
*Monoclimax theory (Clements): a plant that can reproduce successfully beneath its own shade *Polyclimax theory (Tansley): a mosaic of communities at different cereal stages *Climax Pattern theory (Whittaker): depends on the total environment *Alternative Stable states (Lewontin):shifts due to large perturbations
26
What methods can you use to study succession?
*Space-for-time *Old maps *Palynology (pollen records) *DNA
27
What happens during primary succession?
Nutrient-poor conditions may be improved, nitrogen-fixing species may be important, soil development, lichens weather rocks and accumulate organic matter.
28
What happens are the four ways to start secondary succession
*Advance regeneration *Resprouting *Soil seed bank *Seed rain
29
What does the three-way-model consist of?
*Facilitation *Inhibition *Tolerance
30
What is facilitation?
The presence of one species aids and increases the probability of the growth of a second species
31
What is inhibition?
A species inhibits the presence of another through indirect competition for resources, or direct interference
32
What is tolerance?
There is no interaction with other species. It is all down to individual species’ life history traits. Pioneer species, typically r-strategists, are outcompeted by K-strategists that are better able to compete for limited resources
33
What are the three types of shade tolerance?
*Shade-intolerant (light-demanding) = pioneer plants *Intermediate shade-tolerant *Shade tolerant = late-successional plants
34
What is Tilman's resource ratio hypothesis?
The species that can survive and reproduce at the lowest critical resource level (R*) for a limiting resource will outcompete others for that resource.
35
What is a habitat?
It is where an organism lives, and it must provide a source of food, water, and shelter for the organism
36
What is a niche?
The n-dimensional space in which an organism persists, which encompasses both biotic and abiotic factors
37
Why is diversification a benefit of succession?
Diversification leads to niche complementarity, where different species utilize resources or the environment in ways that minimize direct competition.
38
What is a service?
The benefits that humans obtain from ecosystems
39
What is an ecosystem service?
A collision of ecology and economy, and the diverse benefits that humans freely gain from the natural environment and properly functioning ecosystems.
40
Why is the definition of ecosystem services continually changing?
The primary driver for constant redefinition is for clarity around metrics
41
What has sped up in the last 60 years, harming ecosystems' ability to provide benefits, especially in agriculture?
The pace of change, often involving the simplification of complex ecosystems into managed farmland.
42
When was the green evolution?
1970s
43
What is a major consequence of intensive agriculture?
Intensive agriculture has led to a significant loss of ecosystem services.
44
Are ecosystems static?
No, they can change from things such as deforestation, human development, agriculture
45
What is the ecosystem service cascade?
Landscape structures or process -> landscape function (Capacity) -> Ecosystem service (Flow) -> Benefit (Value)
46
What are the key characteristics and human influences on ecosystems?
*Scale: they exist at various sizes *Human benefits: food, fuel, timber, health, recreation, etc. *Scaling: management at one scale affects other scales *Natural dynamics: they are naturally dynamic but human actions impact these
47
What is a key characteristic of ecosystem health?
Ecosystems are self-regulating and move between equilibrium states
48
What two major factors can cause extreme shifts or collapse?
Demand for ecosystem services (like agriculture) and climate change can drive collapse.
49
How much of the World's forest land has been lost?
50%
50
What percent is considered a "working forest"?
30%, these are trees cut for wood, paper, and pulp-based products
51
How many people currently live in countries experiencing high water stress?
2 billion people
52
By what year is it estimated that how many people could be displaced due to intense water scarcity?
By 2030, 700 million people.
53
What is the Millennium Ecosystem Assessment?
The largest global assessment ever undertaken of the health of ecosystems. Provided the first comprehensive summary of the state of ecosystem health (14 major terrestrial biomes across the globe).
54
What are the four types of ecosystem services?
*Provisioning *Regulating *Cultural *Supporting
55
What is IPBES?
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services
56
What is a trophic structure?
The hierarchy of feeding. It describes who eats whom. A trophic interaction is a transfer of energy e.g. consumption, decomposition, photosynthesis. Energy flows from the bottom to the top.
57
What is a food web?
For every community, a diagram of trophic interactions is called a food web.
58
Do marine or terrestrial systems support more trophic levels?
Marine due to more efficient microbes
59
What is the energetic hypothesis?
Inefficiency of energy transfer along the chain
60
What is the dynamic stability hypothesis?
Long food chains are less stable, and fluctuations at lower trophic levels are magnified, potentially causing the extinction of the top predators
61
What are the dominant species?
A species in a community that has the highest biomass. They can exert robust control over the occurrence and distribution of other species
62
What are keystone species?
Not necessarily the most abundant species, they are disproportionately important to communities, they maintain species diversity.
63
What could the extinction of a keystone species cause?
The extinction of a keystone species may eliminate niches of many other species, they modify their environment in such a way that other organisms can live, and in other cases, it can be a predator that maintains diversity at a certain trophic level. e.g. starfish that feed on mussels
64
What percent of all known animal species on Earth are soil or litter dwellers?
25%
65
What percent of soil microorganisms are known to humankind?
1%
66
At what different scales can soil be considered a habitat?
Field scale, profile scale (5cm), root scale (5mm), pore scale (0.5mm).
67
What are two ways in which earthworms influence soil structure and processes?
*Bioturbation of soil (mixing), processing large amounts of soil (25-40 tonnes ha¹ yr¹), creating soil pores (influencing infiltration and water balance, aeration) *contributing to soil aggregation through their casts (feces deposited on the surface).
68
What is a "litter bag experiment" likely used for in soil ecology?
To study the decomposition rates of organic matter under different conditions.
69
Name four major groups of microscopic organisms found in soil.
Bacteria, nematodes, fungi, protozoa.
70
What is notable about the ecological diversity and habitat distribution of nematodes?
Nematodes are one of the most ecologically diverse groups of animals on Earth and are present in nearly all habitats.
71
What is one way in which nematodes can impact microbial activity in the soil?
They can stimulate microbial growth (e.g., through grazing on bacteria and fungi, releasing nutrients).
72
What are three positive outcomes associated with healthy ecosystems?
Nutrient cycling increases, productivity increases, and nutrient loss is minimized.
73
What is "functional redundancy" in the context of a soil food web?
Functional redundancy refers to the presence of multiple species that perform similar ecological functions within the soil food web. This can provide stability and resilience to the ecosystem if one species is lost.
74
What is soil comprised of?
*Water *Plant roots *Soil particles

Ecosystem Function and Services (5 decks)

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