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Biology (NCERT) - Class XII > XII Chap 14 Ecosystem > Flashcards

XII Chap 14 Ecosystem Flashcards

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1
Q

What is an ecosystem?

A

Structural and functional unit of nature - abiotic and biotic components

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2
Q

Two types of ecosystems?

A

Aquatic

Terrestrial

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3
Q

Which type of ecosystems are these?
Wetland
Grassland
Estuary

A

Wetland - aqua
Grassland - terr
Estuary - aqua

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4
Q

What types of ecosystems are crop fields and aquariums?

A

Man-made

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5
Q

What is stratification?

A

Vertical distribution of species

e.g. Trees at top, shrubs - second, grasses - bottom

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6
Q

4 important components of ecosystems?

A

Productivity
Decomposition
Energy flow
Nutrient cycling

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7
Q

In a pond there is multidirectional movement of energy. T or F?

A

False, unidirectional to the higher trophic levels and dissipation and loss as heat to the environment

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8
Q

___________ is a basic requirement for any ecosystem to function and sustain

A

Constant solar energy

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9
Q

What is primary production?

A

amount of biomass / organic matter produced per unit area
by plant photosynthesis
over a given time period

(g / m^2) or (kcal / m^2)

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10
Q

What is productivity?

A

Rate of biomass production

g / m^2 / year) or (kcal / m^2 / year

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11
Q

Gross vs net primary productivity?

A

Gross - total primary productivity
Net - minus the GPP used in respiration i.e. what is available for heterotrophs (herbivores and decomposers)

GPP - R = NPP

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12
Q

Secondary productivity?

A

Rate of biomass production by consumers

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13
Q

What is the annual NPP of whole biosphere? of oceans?

A

170 billion tons; 55 billion tons

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14
Q

Decomposition?

A

complex organic => inorganic (CO2, water, nutrients)

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15
Q

Detritus?

A

Raw material for decomp.

leaves, bark, flowers, dead remains of animals, fecal matter

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16
Q

Steps in process of decomposition?

A

Fragmentation, leaching, catabolism (simultaneous)
Humification
Mineralisation

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17
Q

What are detritivores?

A

Organisms that decompose detritus

e.g. earthworms

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18
Q

Fragmentation?

A

Decomp by breaking detritus into small particles

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19
Q

Leaching?

A

Water soluble inorganic nutrients => soil => unavailable salts

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20
Q

Catabolism?

A

Bacterial + fungal enzymes turn detritus -> simple inorganic substances

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21
Q

Humification?

A

Accumulation of humus

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22
Q

What is humus?

A 
Dark coloured
amorphous
resistant to microbial action 
colloidal (suspended)
reservoir of nutrients
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23
Q

Mineralisation?

A

Humus further degraded by microbes => inorganic nutrients

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24
Q

Decomposition process requires oxygen. T or F?

A

True

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25
Q

Rate of decomposition is controlled by _____ and _________

A

chemical comp of detritus

Climactic factors

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26
Q

What speeds up decomposition?

A

nitrogen
water-soluble substances like sugars
warm environment
moist environment

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27
Q

What slows down decomposition?

A

Lignin and chitin
low temp
anaerobiosis (absence of oxygen)

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28
Q

Sun is the only source of energy for all ecosystems on Earth. T or F?

A

False, ALMOST ALL. Except for the deep sea hydro-thermal ecosystem

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29
Q

_______ per cent of solar radiation is photosynthetically active radiation

A

50%

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30
Q

Plants capture ______ percent of PAR to sustain the entire living world

A

2-10%

OR 1-5% of total sunlight!

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31
Q

What are the major producers in terr and aquatic ecosystems?

A

Terr - herbaceous and woody plants

Aqua - phytoplankton, algae and higher plants

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32
Q

All animals depend on plants for their food needs. T or F?

A

True (direct or indirectly)

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33
Q

______ are producers / autotrophs and

______ are consumers / heterotrophs

A

Plants;

Animals

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34
Q

Primary vs Secondary consumer

A

Primary - feeds on plants (herbivores)

Secondary - feeds on animals that feeds on plants (carnivores)

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35
Q

Mollusc is what kind of consumer?

A

Herbivore

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36
Q

Grazing food chain begins with _________

Detritus food chain begins with _________

A

Producer;

Dead organic matter

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37
Q

What are saprotrophs?

A

decomposers
feed on dead organic matter
heterotrophic organisms (fungi, bacteria)

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38
Q

How do decomposers break down dead matter?

A

Secrete digestive enzymes and then absorb the dead organic matter

39
Q

In aquatic ecosystem, ______ is the major conduit for energy flow.

In terr, ____

A

GFC - aquatic

DFC - terr

40
Q

Cockroaches and crows are what types of consumers?

A

Omnivores

41
Q

Trophic level?

A

Specific place in the food chain

42
Q

Amount of energy increases at successive trophic levels. T or F?

A

False, decreases

43
Q

1st trophic level?
2nd trophic level?
3rd …

A

1st - producer
2nd - primary consumer (herbivore)
3rd - secondary consumer (carnivore)
…

44
Q

Standing crop?

A

Certain mass of living material at a particular time at a trophic level,

measured as the mass of living organisms OR number in a unit area

45
Q

The measurement of biomass in terms of dry weight is more accurate. Why?

A

The moisture content of a biomass may vary depending upon environmental or physiological conditions

46
Q

Number of trophic levels in the food chain is limited. Why?

A

Because only 10% energy can flow from one trophic level to the next

47
Q

What is the ecological pyramid?

A

Shape when you express food or energy relationship between organisms at different trophic levels

48
Q

3 types of ecological pyramids?

A
  1. number
  2. biomass
  3. energy
49
Q

What does the pyramid of biomass look like for phytoplankton and zooplankton?

A

Inverted. Small number of phytoplankton support large # of zooplankton

50
Q

Can an organism occupy more than one trophic level in a ecological pyramid?

A

Yes

51
Q

Why is the pyramid of biomass in sea generally inverted?

A

Because biomass of fishes far exceeds that of phytoplankton

52
Q

Pyramid of energy for the sea can be inverted. T or F?

A

False, can never be inverted because energy pyramids are always upright (90% always lost at each level)

53
Q

Limitations of ecological pyramids?

A
  1. does not account for same species belonging to 2 or more trophic levels
  2. assumes simple food chain - almost never exists in nature
  3. does not accommodate a food web
  4. no place for saprophytes
54
Q

Ecological succession?

A

gradual and predictable change in species composition of given area

55
Q

Climax community?

A

Community that is in near equilibrium with environment

56
Q

Sere?

A

Entire sequence of communities that successively change in given area

57
Q

The individual transitional communities in an ecosystem are termed _____ or _____

A

seral stages or seral communities

58
Q

Primary vs secondary succession?

A

primary - in area where no living organisms ever existed

secondary - in area that lost all living organisms

59
Q

Succession starts in an area where no living organisms exist. T or F?

A

True

60
Q

Before a biotic community there must be ________

A

fertile soil

61
Q

Which is faster: primary or secondary succession?

A

Secondary because some soil is already present

62
Q

Hydrarch vs Xerarch succession?

A

Hydrarch - in water or wet area, hydric to mesic succession
Xerarch - dry areas, xeric to mesic

mesic = medium water conditions - not too dry or wet

63
Q

______ are the usual pioneer species on rocks

A

Lichens => secrete acids to dissolve rock helping in soil formation

64
Q

_______ are the pioneer species in water

A

Phytoplanktons

65
Q

List species involved in succession on land

A

Lichens => bryophytes => higher plants => climax forest community

66
Q

List the progressive order of species in succession in water

A

Phytoplankton => rooted, submerged plants => rooted, floating angiosperms => free-floating plants => reed-swamp => marsh-meadow => scrub => trees => climax forest community (water body converts to land)

67
Q

Is climax reached faster in primary or secondary succession?

A

Secondary (since soil is already there)

68
Q

What is standing state?

A

Amount of nutrients in soil at any given time,
different in different ecosystems & seasons

nutrients - carbon, nitrogen, phosphorus, calcium

69
Q

What is nutrient cycling?

A

Nutrients are never lost, recycled in ecosystem

aka geochemical cycles

70
Q

What are 2 types of nutrient cycles?

A

Gaseous

Sedimentary

71
Q

What are the reservoirs for the gaseous and sedimentary nutrient cycles?

A

Gaseous - atmosphere

Sedimentary - Earth’s crust

72
Q

What is the function of reservoirs in nutrient cycling?

A

Meet with deficits due to imbalance in rate of influx and efflux

73
Q

Carbon constitutes _____ percent of dry weight of organisms

A

49%

74
Q

______ percent of carbon is found dissolved in oceans

A

71%

75
Q

Fossil fuels are a reservoir of ________

A

Carbon

76
Q

What are the contributors to atmospheric CO2?

A 
Producers & consumers (respiration)
Decomposers
Combustion: Burning wood, forest fire
Fossil fuels
Volcanic activity
77
Q

Some amount of fixed carbon is lost to ____________ and removed from circulation.

A

sediments

78
Q

What do organisms need phosphorus for

A

Biological membranes, nucleic acids and cellular E transfer,

Shells, bones & teeth

79
Q

Reservoir of phosphorus is _______ in the form of ______

A

rock; phosphates

80
Q

How does phosphorus get into plants?

A

Rocks weathered => minute amounts of P dissolve in soil => absorbed by plant roots

81
Q

Decomposers also release phosphorus when breaking down waste products and dead organic matter. T or F?

A

True

82
Q

Differences between carbon cycle and phosphorus cycle?

A
  1. Atmospheric inputs of P due to rainfall are much smaller

2. Gaseous exchange of phosphorus is negligible

83
Q

What are ecosystem services?

A

products of ecosystem processes

e.g. purified air and water, fertile soil, biodiversity, pollination, aesthetic/spiritual value

84
Q

Total cost of fundamental ecosystem services

A

33 trillion;

Soil formation - 50% 
Nutrient cycling - 10%
Recreation - 10%
Climate regulation - 6% 
Habitat for wildlife - 6%
85
Q

What are biotic and abiotic components of ecosystem?

A

Abiotic - air, water and soil

Biotic - producers, consumers and decomposers

86
Q

What are the 2 main structural features of an ecosystem?

A

Species composition

Stratification

87
Q

Arrange in chronological order:

successors, pioneers, stable climax community

A

pioneers => successors => stable climax community

88
Q

Every organism occupies a place in the ecosystem based on source of ________

A

nutrition

89
Q

Which of the following has the largest population in the food chain?
Producers - Primary Consumers - Secondary Consumers - Decomposers

A

Producers

90
Q

Second trophic level in a lake is:

Phytoplankton - Zooplankton - Benthos - Fishes

A

Zooplankton

91
Q

Grasshoppers are herbivores / omnivores / carnivores?

And occupy what trophic level?

A

Herbivores, Second

92
Q

Fishes are herbivores / carnivores?

And occupy what trophic level?

A

Carnivores, Third

93
Q

Secondary producers are herbivores - producers - carnivores or green plants?

A

Herbivores

Biology (NCERT) - Class XII (18 decks)

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