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biology 301 > ch 20 : energy in ecosystems > Flashcards

ch 20 : energy in ecosystems Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

the assemblage of organisms together with their physical and chemical environments

A

ecosystem

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2
Q

what did charles elton do in the 1920s

A

introduced idea of food web and energy transfer within the web

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3
Q

what did AG tansley do in 1935?

A

introduced term “ecosystem” as the fundamental unit of ecological organization

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4
Q

the study of natural systems from the standpoint of energy flow and cycling of matter

A

ecosystem ecology

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5
Q

what are the thermodynamic principles that ecosystems follow?

A
  • conservation of Energy
  • entropy increases due to inefficiency
  • treats ecosystems (and the Earth) as giant thermodynamic machines
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6
Q

energy allocation/flow diagram

A

look over this!! slide 7!!

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7
Q

primary production : what is the ultimate source of energy for most living things?

A

sunlight

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8
Q

what do gross and net mean?

A

gross : total
net : available

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9
Q

photosynthesis equation

A

6CO2 + 6H2O –> C6H12O6 + 6O2

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10
Q

primary productivity : what happens when sunlight is not available?

A

producers rely on chemosynthesis as their source of energy
ex : deep ocean thermal vents

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11
Q

primary productivity : where do producers harness energy and what do they use the energy for?

A
  • producers harness energy and form the basis of food webs.
  • producers use energy for respiration, growth, and reproduction.
  • the energy used for growth and reproduction is the energy available to consumers.
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12
Q

the rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis

A

primary productivity

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13
Q

the biomass of producers present in a given area of an ecosystem at a particular moment in time.

A

standing crop

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14
Q

ecosystems with ______________ may not have a high-standing crop; consumers may eat it as quickly as it grows

A

high primary productivity

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15
Q

the rate at which energy is captured and assimilated by producers in an area.

A

gross primary productivity (GPP)

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16
Q

the rate of energy that is assimilated by producers and converted into producer biomass in an area; includes all energy that is not respired

A

net primary productivity (NPP)

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17
Q

equation for NPP

A

NPP = GPP - respiration
both GPP and NPP are expressed in unites of Jourles/m^2/year

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18
Q

t/f photosynthesis is an effective process

A

false; it’s not

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19
Q

how is primary productivity measured?

A

primary productivity is a rate; the choice of how to measure this rate depends on the particular ecosystem being studied.

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20
Q

how is NPP measured?

A

as the change in producer biomass over time

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21
Q

how do researchers determine mass growth over a period of time?

A

they harvest plants

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22
Q

what will lead to an underestimation of NPP

A

substantial amounts of herbivory or tissue mortality

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23
Q

t/f researchers are able to estimate the biomass lost to herbivory or tissue mortality

A

true

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24
Q

researchers typically only harvest what type of plant growth?

A

above ground
- the amount of below-ground biomass can be substantial

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25
Q

why is harvesting below-ground tissue challenging?

A
  • they are deep and tend to break off when harvested
  • fine roots frequently die and are replaced making it difficult to estimate the biomass accumulation
  • plants also send energy to mycorrhizal fungi; this energy is included in total NPP
26
Q

what allows us to measure NPP by recording the rate of CO2 exchange from the leaf?

A

since producers take up CO2 during photosynthesis and produce CO2 during respiration

27
Q

how does recording the rate of CO2 exchange from the leaf work?

A
  • leaves are placed in a sealed chamber with a CO2 sensor.
  • when a leaf is exposed to light in the chamber, photosynthesis and respiration occur; the net uptake of CO2 represents NPP.
  • when a leaf is concealed in the dark, only CO2 respiration occurs. We can then measure GPP:

GPP = NPP + Respiration

28
Q

what are some other ways to measure CO2 uptake and release?

A
  • researchers can place a leaf into a sealed container with added CO2 that contains trace amounts of a rare carbon isotope (e.g., 14C).
  • to measure NPP, they track the net movement of 14C from the air into the plant tissues and back into the air.
  • on a larger scale (e.g., a forest), researchers measure CO2 uptake and release by using towers that sample CO2 concentrations at different heights above the ground.
  • the differences in CO2 within the forest and in the atmosphere provide an estimate of photosynthesis and respiration in an area.
29
Q

why does measuring CO2 in aquatic systems not provide a good estimate of NPP?

A

CO2 is rapidly converted into bicarbonate ions

30
Q

how does measuring NPP work with aquatic systems?

A
  • since producers release O2 during photosynthesis and take up O2 during respiration, we can estimate NPP and GPP by measuring changes in concentrations of O2.
  • the process is identical to a light-dark bottle experiment in a sealed air chamber, except it is done in sealed water chambers.
  • in a bottle exposed to light, the net increase in O2 is the combined result of photosynthesis and respiration by algae (NPP).
  • in a dark bottle, the decrease in O2 is a result of algal respiration.
  • the sum of NPP and respiration is equal to GPP.
31
Q

a technique that allows measurement of conditions on Earth from a distant location, typically using satellites or airplanes that take photographs of large areas of the globe.

A

remote sensing

32
Q

when is remote sensing used?

A

to assess productivity across large spatial scales (continents or oceans)

33
Q

a technique that allows measurement of conditions on Earth from a distant location, typically using satellites or airplanes that take photographs of large areas of the globe.

A

remote sensing

34
Q

how does remote sensing work?

A
  • chlorophyll pigments absorb wavelengths in the red and blue range but reflect wavelengths in the green range.
  • satellite images that show a pattern of high absorption of blue and red light, and high reflectance of green light indicate ecosystems with high-standing crops.
35
Q

t/f NPP is the same with latitude and across terrestrial and aquatic biomes.

A

false; NPP varies with latitude and across terrestrial and aquatic biomes.

36
Q

in general NPP is ________ correlated with annual temperature

A

positively

37
Q

why do tropical areas have high NPP?

A

tropical areas have high NPP due to intense sunlight, warm temperatures, abundant precipitation, and rapidly recycled nutrients.

38
Q

what happens with productivity at higher latitudes?

A

at higher latitudes, productivity is limited by shorter periods of sunlight and lower temperatures.

39
Q

what happens to NPP in deserts?

A

in deserts, NPP is constrained by lack of precipitation.

40
Q

mean annual precipitation is positively related with NPP until what?

A

until 3 m of annual precipitation is reached

41
Q

what happens to ecosystems that receive more than 3 m of precipitation?

A

experience a decline in NPP because nutrients leach from the soil

42
Q

rates of decomposition are ________ in waterlogged soils.

A

reduced

43
Q

when organic matter is broken down slowly…….

A

…… fewer nutrients are available in the soil for plant growth

44
Q

what can strongly affect NPP in terrestrial ecosystems?

A

nutrients — particularly nitrogen and phosphorus

45
Q

what was concluded after researchers conducted a survey of studies that examined the ratio of NPP in terrestrial ecosystems with added nutrients to NPP in terrestrial ecosystems without added nutrients?

A
  • grasslands, forests, and tundra habitats all experienced increased NPP when nitrogen and phosphorus were added.
  • in some habitats, adding both nutrients causes a greater increase in NPP than adding either alone.
46
Q

in addition to temperature, precipitation, and nutrients, aquatic ecosystems are also limited by _________.

within aquatic ecosystems that have similar temperatures and light levels, NPP is largely limited by __________.

A

light; nutrients

47
Q

both _________ and __________ can limit NPP of aquatic ecosystems.

A

nitrogen and phosphorus

48
Q

experiment : hourglass-shaped lake in ontario

A
  • in an hourglass-shaped lake in Ontario, researchers put in place a plastic curtain that divided the lake into two halves
  • on one side, they added carbon and N; on the other they added carbon, N, and P.
  • on the side that received carbon, N, and P, there was a large increase in NPP due to growth of algae.
49
Q

what was concluded after researchers compiled data from 928 experiments that added nitrogen, phosphorus, or both to freshwater or marine systems?

A

across all ecosystems, adding nitrogen and phosphorus together often generated higher NPP than adding either nutrient separately.

50
Q

in the open ocean, what are some other elements that limit productivity?

A
  • diatoms are often limited by silicon, which is required to build silicate shells.
  • iron is also limiting because it rapidly combines with phosphorus and precipitates to the ocean bottom.
51
Q

what happened when researchers added iron to 64 km2 of ocean, concentrations of phytoplankton tripled.

A

adding iron has the potential to grow algae and subsequently reduce CO2 in the ocean and air, but the increase in the respiration of CO2 by primary consumers may counteract this effect.

52
Q

trophic pyramid

A

a chart composed of stacked rectangles representing the amount of energy (i.e., pyramid of energy) or biomass (i.e., pyramid of biomass) in each trophic group.

53
Q

trophic pyramids: in terrestrial systems, pyramids of biomass and energy look ________.

A

similar
- plants have relatively long lives, many have defenses against herbivory, and only small amounts of terrestrial plant material are consumed.

54
Q

trophic pyramids : in aquatic ecosystems, most producers are ________- that rapidly reproduce and are quickly consumed.

A

tiny algae

55
Q

the standing crop of algae is much smaller than that of consumers, which creates an __________

A

inverted biomass pyramid

56
Q

what percentage of energy is passed onto the next trophic level and why?

A

5-20%
- follow the energy from ingestion to new biomass(production)
- assimilated energy= ingested – egested energy
- production= assimilated energy – respiration - excretion

57
Q

the percentage of net production from one trophic level compared to the next lower trophic level

A

ecological efficiency (food chain efficiency)

58
Q

why do low ecological efficiencies make it difficult to have long food chains?

A

there is little energy to support higher trophic levels

59
Q

why do aquatic ecosystems typically have more trophic levels than terrestrial ones? ?

A

due to the differences in ecological efficiencies
** aquatic ones often have 5 and terrestrial ones have 3-4

60
Q

compare and contrast the defenses of terrestrial and aquatic plants

A
  • terrestrial plants contain many defense compounds, and many have tissues that cannot be consumed (e.g., wood).
  • aquatic algae is small, has no defenses, and is easily consumed; therefore a higher fraction of an ecosystem’s energy can move up the food chain.
  • in addition, consumers in aquatic systems are only slightly larger than the diet they consume; terrestrial systems contain many large producers and herbivores.

biology 301 (6 decks)

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