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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
Bottom-up control
increase in food, increases higher trophic levels | • ie nutrient levels control plants, which controls herbivores, which controls predators
26
Disturbances and succession can also affect...
species composition
27
Intermediate disturbance hypothesis
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
28
Ecological succession
disturbed areas may be colonised by different species, which in turn get replaced by other species
29
Primary succession
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
30
Secondary succession
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
31
Where does energy flow & chemical cycling occur?
in every ecosystem regardless of its size
32
Describe energy flow & chemical cycling:
* 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
What do ecologists study?
interactions of organisms with the physical environment so they utilise a lot of chemistry and physics concepts
34
What are the conservation of energy (Laws of Thermodynamics)
* 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
What are the conservation of mass?
* Matter cannot be created nor destroyed (Law of Conservation of Mass) * Chemical elements as organisms decay are recycled into the environment
36
Order of trophic levels (bottom to top)
1. primary producers 2. primary consumers 3. secondary consumers 4. tertiary consumers 5. detritivores
37
Primary producers
The largest trophic level (photosynthetic autotrophs)
38
What is the largest trophic level?
primary producers (photosynthetic autotrophs)
39
Primary consumers
heterotrophs, usually herbivores
40
Secondary consumers
usually predators (carnivores)
41
Tertiary consumers
carnivores eating carnivores
42
Detritivores
There are also detritivores (decomposers) that eat decaying organic matter (dead animals, fecal matter, fallen leaves and wood)
43
What are detritivores considered?
a primary consumer
44
What are detritivores eaten by?
Eaten by secondary and tertiary consumers
45
Primary production (definition)
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
Gross primary production (GPP)
the amount of energy from light (or chemicals from chemoautotrophs) converted to chemical energy of organic molecules per unit time
47
Net Primary Production (NPP)
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
Net Ecosystem Production (NEP)
total biomass accumulation per unit time (GPP - total respiration of all organisms)
49
In aquatic ecosystems, what are important in controlling primary production?
light and nutrients
50
Light limitation
* 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
Nutrient limitation
* 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
Limiting nutrients...
must be added for primary production to increase (usually N or P, but others can be limiting too)
53
Why are concentration low in the photic zone?
because they are readily absorbed by primary producers
54
Eutrophication
occurs when too much limiting nutrient is added (ex. Lake Winnipeg)
55
In terrestrial ecosystems, soil nutrients...
limit primary production
56
What are often the limiting nutrient?
Nitrogen and phosphorous
57
Nitrogen
limits plant growth most
58
Phosphorous
limitations common in older soils where P has leached away over time or precipitates due to basic soils
59
How does plant symbioses help primary producers?
overcome a lot of these limitations • Mycorrhizae • Nitrogen-fixing bacteria
60
Climate change increases in...
temperatures and changes in precipitation
61
What can affect NPP?
climate change
62
Overall NPP has...
increased 6% between 1982 – 1999 in terrestrial ecosystems, especially in tropical rainforests
63
NEP >0
ecosystem is storing more carbon (ie carbon sinks)
64
NEP <0
ecosystem is losing more carbon than it stores (ie carbon source)
65
Secondary production
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
Production efficiency
is the percentage of energy stored in assimilated food that is not used in metabolic processes in an individual
67
Production Efficiency =
𝑁𝑒𝑡 𝑠𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝑥 100% / | 𝐴𝑠𝑠𝑖𝑚𝑖𝑙𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑝𝑟𝑖𝑚𝑎𝑟𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜�
68
Trophic efficiency
is the percentage of production transferred from one trophic level to the next
69
Why is trophic efficiency always less than production efficiences?
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
What is trophic efficiency usually?
* 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
What gets recycled within the ecosystems?
Chemical
72
What does carbon form?
the framework for all of life’s organic molecules
73
What is CO2 used by?
by plants in photosynthesis and converted to sugars that are used by consumers
74
How is CO2 returned to the ecosystem?
via respiration
75
What is much of the carbon stored as?
fossil fuels, soils, sediments in aquatic ecosystems, dissolved in oceans as calcium carbonate, atmospheric CO2 and plant/animal biomass
76
What does burning of fossil fuels & wood add?
adds more CO2 to the atmosphere, as well as volcanic eruptions
77
What does increased forest fires & peat bog fires also contribute to?
also contribute to everincreasing CO2 levels in the atmosphere

biology (25 decks)

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