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biology > Lecture 32 - Ecology (part 3) > Flashcards

Lecture 32 - Ecology (part 3) Flashcards

1
Q

What do community interactions rely on?

A

the species composition

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2
Q

Species diversity

A

number of species present

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3
Q

Relative abundance

A

the evenness or proportion of each species

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4
Q

Trophic structure

A

feeding relationships

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5
Q

Species richness

A

number of species

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6
Q

What do we usually equate biodiversity with?

A 
species richness (number of species)
• Need to also consider the relative abundance of each species….somethings are rarer in some communities than others
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7
Q

Why do ecologists use indexes?

A

to quantify the species composition

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8
Q

Shannon’s diversity index (H)

A
  • ρA = relative abundance of species A, etc
  • ln is the natural logarithm
  • Higher H means higher diversity

𝐻 = −(ρ𝐴 ln ρ𝐴 + ρ𝐵ln(ρ𝐵) + ρ𝐶ln(ρ𝐶)…etc)

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9
Q

Higher H (in Shannon’s diversity index) means…

A

higher diversity

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10
Q

The transfer of food energy up ______ ______ from its source to its apex is called the ______ ______, which are linked together into complex _____ _____

A

trophic level

food chain

food webs

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11
Q

Food webs are _____ ______, but food chains are _____ ______ (4 linkages)

A

quite complex

generally short

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12
Q

Energetic hypothesis

A

suggests the length of a food chain is limited by the inefficiency of energy transfer along the chain

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13
Q

Trophic efficiency

A

is the ratio of production of energy at one trophic level to the next lower level
• Ie. The percentage of energy that consumers in trophic level gain and convert into biomass from the total stored energy of the lower level

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14
Q

Why is there energy loss?

A

Lost via heat from metabolism

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15
Q

What are the species with large impacts?

A
  • Dominant species
  • Keystone species
  • Ecosystem engineers
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16
Q

Dominant species

A

are species in a community that has the HIGHEST abundance or collectively the HIGHEST biomass

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17
Q

What do dominant species exert?

A

Exert great control over the community

• Could be a result of competitive exclusion or the adaptations to avoid predation/herbivory and disease

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18
Q

Example of dominant species:

A

Ex. Sugar maples in eastern North America are dominant, resulting in shading
which affects the abiotic conditions of the underlying soil, which in turn affects
what other species are present
• Could be a result of competitive exclusion or the adaptations to avoid predation/herbivory and disease

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19
Q

Keystone species

A

are not abundant in the community (and quite often rare) yet EXERTS A STRONG CONTROL on community structure

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20
Q

Example of keystone species:

A

ex. Sea otters are keystone species in kelp forests
• They feed on sea urchins, which can eliminate kelp forests
• Removal of the otters resulted in overgrazing of the urchins on the kelps, wiping out kelp populations and altering the community structure

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21
Q

Ecosystem engineers

A

dramatically alter their community by CHANGING the PHYSICAL environments within the community

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22
Q

Examples of ecosystem engineers:

A

• Ex beavers building dams and flooding streams and meadows
• Ex foxes in the arctic
- Den sites are rich in nitrates from fecal matter and decaying prey items
- Add nutrient loads to an otherwise nutrient poor arctic tundra
- Provides nutrients for lush vegetation and grasses in otherwise barren landscape

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23
Q

What controls the biomass of a species?

A
  • Top-down control (Trophic cascade model)

* Bottom-up control

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24
Q

Top-down control (Trophic cascade model)

A

reducing number of predators increases prey

• ie. Predation limits herbivores, which limits plants, which limits nutrient uptake

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25
Q

Bottom-up control

A

increase in food, increases higher trophic levels

• ie nutrient levels control plants, which controls herbivores, which controls predators

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26
Q

Disturbances and succession can also affect…

A

species composition

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27
Q

Intermediate disturbance hypothesis

A

states that MODERATE amounts of disturbance harbours the HIGHEST species diversity
• High levels of disturbance stress species out and low levels of disturbance allows for dominant species to out-compete others

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28
Q

Ecological succession

A

disturbed areas may be colonised by different species, which in turn get replaced by other species

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29
Q

Primary succession

A

building a community from initially nothing (such as a new volcanic eruption or on debris left behind glacial retreat) -> can take 100s to 1000s of years
• Lichens are usually the first to colonise newly disturbed areas and start weather rock into soils. Mosses follow shortly after
• Then they are overgrown by grasses and fast growing shrubs and trees and become the community’s dominant vegetation

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30
Q

Secondary succession

A

occurs when the existing community has been cleared by a disturbance that leaves the soil intact (ie forest fires, floods, insect swarms)
• Earliest plants to take the area over again are faster growing herbaceous plants that had seeds carried by animals or wind
• Woody shrubs and trees come in later

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31
Q

Where does energy flow & chemical cycling occur?

A

in every ecosystem regardless of its size

32
Q

Describe energy flow & chemical cycling:

A
  • Energy enters ecosystems via light
  • Converted to chemical energy by autotrophs (photosynthesis in primary producers)
  • Passed to heterotrophs from eating plants and other animals
  • Lost through heat
33
Q

What do ecologists study?

A

interactions of organisms with the physical environment so they utilise a lot of chemistry and physics concepts

34
Q

What are the conservation of energy (Laws of Thermodynamics)

A
  • Energy cannot be created nor destroyed, but only transferred or transformed
  • The amount of energy stored in organic molecules equals the amount of solar energy intercepted
  • A lot of energy is lost as heat, which increases the entropy of the environment
35
Q

What are the conservation of mass?

A
  • Matter cannot be created nor destroyed (Law of Conservation of Mass)
  • Chemical elements as organisms decay are recycled into the environment
36
Q

Order of trophic levels (bottom to top)

A
  1. primary producers
  2. primary consumers
  3. secondary consumers
  4. tertiary consumers
  5. detritivores
37
Q

Primary producers

A

The largest trophic level (photosynthetic autotrophs)

38
Q

What is the largest trophic level?

A

primary producers (photosynthetic autotrophs)

39
Q

Primary consumers

A

heterotrophs, usually herbivores

40
Q

Secondary consumers

A

usually predators (carnivores)

41
Q

Tertiary consumers

A

carnivores eating carnivores

42
Q

Detritivores

A

There are also detritivores (decomposers) that eat decaying organic matter (dead animals, fecal matter, fallen leaves and wood)

43
Q

What are detritivores considered?

A

a primary consumer

44
Q

What are detritivores eaten by?

A

Eaten by secondary and tertiary consumers

45
Q

Primary production (definition)

A

The amount of light energy converted to chemical energy by photoautotrophs
• Since primary consumers get their energy second hand (by eating primary producers), primary production sets the energy budget

46
Q

Gross primary production (GPP)

A

the amount of energy from light (or chemicals from chemoautotrophs) converted
to chemical energy of organic molecules per unit time

47
Q

Net Primary Production (NPP)

A

GPP – energy used by primary producers for their own metabolism (respiration)
• ~1/2 of GPP • Usually expressed as energy J/(m2 x year) or biomass g/(m2x year)
• Reflected of the amount of new biomass added in a given time

48
Q

Net Ecosystem Production (NEP)

A

total biomass accumulation per unit time (GPP - total respiration of all organisms)

49
Q

In aquatic ecosystems, what are important in controlling primary production?

A

light and nutrients

50
Q

Light limitation

A
  • Depth of light penetration affects the primary production in the photic zones in water bodies
  • Half of all solar radiation is absorbed in the first 15 m of water
51
Q

Nutrient limitation

A
  • Limiting nutrients must be added for primary production to increase (usually N or P, but others can be limiting too)
  • Concentrations are LOWER in the PHOTIC ZONE because they are readily absorbed by primary producers
  • Eutrophication occurs when TOO MUCH limiting nutrient is added (ex. Lake Winnipeg)
52
Q

Limiting nutrients…

A

must be added for primary production to increase (usually N or P, but others can be limiting too)

53
Q

Why are concentration low in the photic zone?

A

because they are readily absorbed by primary producers

54
Q

Eutrophication

A

occurs when too much limiting nutrient is added (ex. Lake Winnipeg)

55
Q

In terrestrial ecosystems, soil nutrients…

A

limit primary production

56
Q

What are often the limiting nutrient?

A

Nitrogen and phosphorous

57
Q

Nitrogen

A

limits plant growth most

58
Q

Phosphorous

A

limitations common in older soils where P has leached away over time or precipitates due to basic soils

59
Q

How does plant symbioses help primary producers?

A

overcome a lot of these limitations
• Mycorrhizae
• Nitrogen-fixing bacteria

60
Q

Climate change increases in…

A

temperatures and changes in precipitation

61
Q

What can affect NPP?

A

climate change

62
Q

Overall NPP has…

A

increased 6% between 1982 – 1999 in terrestrial ecosystems, especially in tropical rainforests

63
Q

NEP >0

A

ecosystem is storing more carbon (ie carbon sinks)

64
Q

NEP <0

A

ecosystem is losing more carbon than it stores (ie carbon source)

65
Q

Secondary production

A

The amount of energy that is converted from the consumer’s food to the consumer’s biomass in the ecosystem
• Cannot completely digest all that they consume, so is eaten by detritivores

66
Q

Production efficiency

A

is the percentage of energy stored in assimilated food that is not used in metabolic processes in an individual

67
Q

Production Efficiency =

A

𝑁𝑒𝑡 𝑠𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝑥 100% /

𝐴𝑠𝑠𝑖𝑚𝑖𝑙𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑝𝑟𝑖𝑚𝑎𝑟𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜�

68
Q

Trophic efficiency

A

is the percentage of production transferred from one trophic level to the next

69
Q

Why is trophic efficiency always less than production efficiences?

A

because they take into account the energy loss via feces and metabolism AND energy stored in organic matter at lower trophic levels that has not been consumed

70
Q

What is trophic efficiency usually?

A
  • Usually about 10%, but can range from 5%-20%

* In other words, 90% of available energy at one trophic level is not transferred to the next

71
Q

What gets recycled within the ecosystems?

A

Chemical

72
Q

What does carbon form?

A

the framework for all of life’s organic molecules

73
Q

What is CO2 used by?

A

by plants in photosynthesis and converted to sugars that are used by consumers

74
Q

How is CO2 returned to the ecosystem?

A

via respiration

75
Q

What is much of the carbon stored as?

A

fossil fuels, soils, sediments in aquatic ecosystems, dissolved in oceans as calcium carbonate, atmospheric CO2 and plant/animal biomass

76
Q

What does burning of fossil fuels & wood add?

A

adds more CO2 to the atmosphere, as well as volcanic eruptions

77
Q

What does increased forest fires & peat bog fires also contribute to?

A

also contribute to everincreasing CO2 levels in the atmosphere

biology (25 decks)

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