XII Chap 14 Ecosystem Flashcards
What is an ecosystem?
Structural and functional unit of nature - abiotic and biotic components
Two types of ecosystems?
Aquatic
Terrestrial
Which type of ecosystems are these?
Wetland
Grassland
Estuary
Wetland - aqua
Grassland - terr
Estuary - aqua
What types of ecosystems are crop fields and aquariums?
Man-made
What is stratification?
Vertical distribution of species
e.g. Trees at top, shrubs - second, grasses - bottom
4 important components of ecosystems?
Productivity
Decomposition
Energy flow
Nutrient cycling
In a pond there is multidirectional movement of energy. T or F?
False, unidirectional to the higher trophic levels and dissipation and loss as heat to the environment
___________ is a basic requirement for any ecosystem to function and sustain
Constant solar energy
What is primary production?
amount of biomass / organic matter produced per unit area
by plant photosynthesis
over a given time period
(g / m^2) or (kcal / m^2)
What is productivity?
Rate of biomass production
g / m^2 / year) or (kcal / m^2 / year
Gross vs net primary productivity?
Gross - total primary productivity
Net - minus the GPP used in respiration i.e. what is available for heterotrophs (herbivores and decomposers)
GPP - R = NPP
Secondary productivity?
Rate of biomass production by consumers
What is the annual NPP of whole biosphere? of oceans?
170 billion tons; 55 billion tons
Decomposition?
complex organic => inorganic (CO2, water, nutrients)
Detritus?
Raw material for decomp.
leaves, bark, flowers, dead remains of animals, fecal matter
Steps in process of decomposition?
Fragmentation, leaching, catabolism (simultaneous)
Humification
Mineralisation
What are detritivores?
Organisms that decompose detritus
e.g. earthworms
Fragmentation?
Decomp by breaking detritus into small particles
Leaching?
Water soluble inorganic nutrients => soil => unavailable salts
Catabolism?
Bacterial + fungal enzymes turn detritus -> simple inorganic substances
Humification?
Accumulation of humus
What is humus?
Dark coloured amorphous resistant to microbial action colloidal (suspended) reservoir of nutrients
Mineralisation?
Humus further degraded by microbes => inorganic nutrients
Decomposition process requires oxygen. T or F?
True
Rate of decomposition is controlled by _____ and _________
chemical comp of detritus
Climactic factors
What speeds up decomposition?
nitrogen
water-soluble substances like sugars
warm environment
moist environment
What slows down decomposition?
Lignin and chitin
low temp
anaerobiosis (absence of oxygen)
Sun is the only source of energy for all ecosystems on Earth. T or F?
False, ALMOST ALL. Except for the deep sea hydro-thermal ecosystem
_______ per cent of solar radiation is photosynthetically active radiation
50%
Plants capture ______ percent of PAR to sustain the entire living world
2-10%
OR 1-5% of total sunlight!
What are the major producers in terr and aquatic ecosystems?
Terr - herbaceous and woody plants
Aqua - phytoplankton, algae and higher plants
All animals depend on plants for their food needs. T or F?
True (direct or indirectly)
______ are producers / autotrophs and
______ are consumers / heterotrophs
Plants;
Animals
Primary vs Secondary consumer
Primary - feeds on plants (herbivores)
Secondary - feeds on animals that feeds on plants (carnivores)
Mollusc is what kind of consumer?
Herbivore
Grazing food chain begins with _________
Detritus food chain begins with _________
Producer;
Dead organic matter
What are saprotrophs?
decomposers
feed on dead organic matter
heterotrophic organisms (fungi, bacteria)
How do decomposers break down dead matter?
Secrete digestive enzymes and then absorb the dead organic matter
In aquatic ecosystem, ______ is the major conduit for energy flow.
In terr, ____
GFC - aquatic
DFC - terr
Cockroaches and crows are what types of consumers?
Omnivores
Trophic level?
Specific place in the food chain
Amount of energy increases at successive trophic levels. T or F?
False, decreases
1st trophic level?
2nd trophic level?
3rd …
1st - producer
2nd - primary consumer (herbivore)
3rd - secondary consumer (carnivore)
…
Standing crop?
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
The measurement of biomass in terms of dry weight is more accurate. Why?
The moisture content of a biomass may vary depending upon environmental or physiological conditions
Number of trophic levels in the food chain is limited. Why?
Because only 10% energy can flow from one trophic level to the next
What is the ecological pyramid?
Shape when you express food or energy relationship between organisms at different trophic levels
3 types of ecological pyramids?
- number
- biomass
- energy
What does the pyramid of biomass look like for phytoplankton and zooplankton?
Inverted. Small number of phytoplankton support large # of zooplankton
Can an organism occupy more than one trophic level in a ecological pyramid?
Yes
Why is the pyramid of biomass in sea generally inverted?
Because biomass of fishes far exceeds that of phytoplankton
Pyramid of energy for the sea can be inverted. T or F?
False, can never be inverted because energy pyramids are always upright (90% always lost at each level)
Limitations of ecological pyramids?
- does not account for same species belonging to 2 or more trophic levels
- assumes simple food chain - almost never exists in nature
- does not accommodate a food web
- no place for saprophytes
Ecological succession?
gradual and predictable change in species composition of given area
Climax community?
Community that is in near equilibrium with environment
Sere?
Entire sequence of communities that successively change in given area
The individual transitional communities in an ecosystem are termed _____ or _____
seral stages or seral communities
Primary vs secondary succession?
primary - in area where no living organisms ever existed
secondary - in area that lost all living organisms
Succession starts in an area where no living organisms exist. T or F?
True
Before a biotic community there must be ________
fertile soil
Which is faster: primary or secondary succession?
Secondary because some soil is already present
Hydrarch vs Xerarch succession?
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
______ are the usual pioneer species on rocks
Lichens => secrete acids to dissolve rock helping in soil formation
_______ are the pioneer species in water
Phytoplanktons
List species involved in succession on land
Lichens => bryophytes => higher plants => climax forest community
List the progressive order of species in succession in water
Phytoplankton => rooted, submerged plants => rooted, floating angiosperms => free-floating plants => reed-swamp => marsh-meadow => scrub => trees => climax forest community (water body converts to land)
Is climax reached faster in primary or secondary succession?
Secondary (since soil is already there)
What is standing state?
Amount of nutrients in soil at any given time,
different in different ecosystems & seasons
nutrients - carbon, nitrogen, phosphorus, calcium
What is nutrient cycling?
Nutrients are never lost, recycled in ecosystem
aka geochemical cycles
What are 2 types of nutrient cycles?
Gaseous
Sedimentary
What are the reservoirs for the gaseous and sedimentary nutrient cycles?
Gaseous - atmosphere
Sedimentary - Earth’s crust
What is the function of reservoirs in nutrient cycling?
Meet with deficits due to imbalance in rate of influx and efflux
Carbon constitutes _____ percent of dry weight of organisms
49%
______ percent of carbon is found dissolved in oceans
71%
Fossil fuels are a reservoir of ________
Carbon
What are the contributors to atmospheric CO2?
Producers & consumers (respiration) Decomposers Combustion: Burning wood, forest fire Fossil fuels Volcanic activity
Some amount of fixed carbon is lost to ____________ and removed from circulation.
sediments
What do organisms need phosphorus for
Biological membranes, nucleic acids and cellular E transfer,
Shells, bones & teeth
Reservoir of phosphorus is _______ in the form of ______
rock; phosphates
How does phosphorus get into plants?
Rocks weathered => minute amounts of P dissolve in soil => absorbed by plant roots
Decomposers also release phosphorus when breaking down waste products and dead organic matter. T or F?
True
Differences between carbon cycle and phosphorus cycle?
- Atmospheric inputs of P due to rainfall are much smaller
2. Gaseous exchange of phosphorus is negligible
What are ecosystem services?
products of ecosystem processes
e.g. purified air and water, fertile soil, biodiversity, pollination, aesthetic/spiritual value
Total cost of fundamental ecosystem services
33 trillion;
Soil formation - 50% Nutrient cycling - 10% Recreation - 10% Climate regulation - 6% Habitat for wildlife - 6%
What are biotic and abiotic components of ecosystem?
Abiotic - air, water and soil
Biotic - producers, consumers and decomposers
What are the 2 main structural features of an ecosystem?
Species composition
Stratification
Arrange in chronological order:
successors, pioneers, stable climax community
pioneers => successors => stable climax community
Every organism occupies a place in the ecosystem based on source of ________
nutrition
Which of the following has the largest population in the food chain?
Producers - Primary Consumers - Secondary Consumers - Decomposers
Producers
Second trophic level in a lake is:
Phytoplankton - Zooplankton - Benthos - Fishes
Zooplankton
Grasshoppers are herbivores / omnivores / carnivores?
And occupy what trophic level?
Herbivores, Second
Fishes are herbivores / carnivores?
And occupy what trophic level?
Carnivores, Third
Secondary producers are herbivores - producers - carnivores or green plants?
Herbivores
