In ecosystems, what process allows plants to convert carbon dioxide from the atmosphere or water into organic compounds?
Photosynthesis
Forms the base of most food chains by producing organic molecules from inorganic carbon.
Most of the sugars produced by plants during photosynthesis are used for what cellular process?
Respiration
Sugars act as respiratory substrates to release energy for cellular activities.
What term describes the total mass of living biological material in a given area or ecosystem?
Biomass
Usually measured as dry mass or carbon mass per unit area.
How is plant biomass commonly standardised when being measured in ecological studies?
Dry mass
Water is removed to avoid variation caused by differing water content.
What laboratory technique can be used to estimate the chemical energy stored in plant biomass?
Calorimetry
Measures heat energy released when biomass is burned.
What term describes the total chemical energy fixed by plants through photosynthesis per unit area per unit time?
Gross primary production
Includes all energy fixed by photosynthesis before respiratory losses.
What term describes the chemical energy stored in plant biomass after respiratory losses have been deducted?
Net primary production
Represents the energy available for growth and higher trophic levels.
Fill in the blank:
NPP = GPP – ______
R
R represents respiratory losses to the environment.
Why is net primary production important for other trophic levels in an ecosystem?
It is the energy available to consumers and decomposers.
NPP represents plant biomass remaining after respiratory losses.
True or False:
Net primary production includes energy lost through plant respiration.
False
NPP excludes respiratory losses; only remaining stored energy is counted.
In ecological energy calculations, what symbol represents the chemical energy in ingested food by consumers?
I
Used in the equation for calculating consumer production.
What symbol represents chemical energy lost to the environment in faeces and urine when calculating consumer production?
F
Energy not assimilated by the consumer.
What symbol represents energy lost through respiration in consumers?
R
Respiratory losses release energy as heat to the environment.
Fill in the blank:
N = I – F – ______
R
Calculates net production of consumers such as animals.
True or False:
Net production of consumers represents the energy available for growth and reproduction.
True
It reflects the biomass increase of the consumer population.
What general term describes the rate at which biomass or energy is accumulated in organisms or ecosystems?
Productivity
Often expressed per unit area per unit time.
What farming strategy increases energy transfer efficiency by reducing the number of trophic links in a food chain?
Simplifying food chains
Fewer trophic links mean less energy is lost before reaching humans.
True or False:
Increasing respiratory activity in livestock improves the efficiency of energy transfer to humans.
False
Higher respiration increases energy loss as heat, reducing efficiency.
What farming approach aims to increase the proportion of energy converted into useful biomass in livestock?
Reducing respiratory losses
Achieved by limiting movement, controlling temperature and selective breeding.
What group of organisms gain energy directly from net primary production by feeding on plants?
Herbivores
They occupy the second trophic level in most food chains.
Why are nutrient cycles essential in natural ecosystems?
Recycling of nutrients
Matter is continually reused so elements like nitrogen and phosphorus remain available for organisms.
What type of organism feeds on dead organic matter and releases enzymes externally to break it down?
Saprobionts
Commonly fungi and bacteria that carry out extracellular digestion during decomposition.
During decomposition, which process converts organic nitrogen compounds in dead organisms into ammonium ions?
Ammonification
Carried out by microorganisms during decay of proteins, nucleic acids and other nitrogen-containing molecules.
What process converts ammonium ions in soil into nitrite and then nitrate ions?
Nitrification
This occurs in two oxidation stages carried out by nitrifying bacteria.
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1: Biological Molecules138
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1: Enzymes & Digestion16
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1: Cell Structure52
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1: Cell Division20
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1: Membranes & Transport20
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2: Exchange & Transport Systems76
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2: Plant Transport20
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2: Immunology36
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3: DNA & Protein Synthesis27
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3: Genetic Diversity14
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3: Biodiversity & Classification32
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3: Investigating Diversity12
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4: Evolution42
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4: Populations & Ecosystems24
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4: Energy & Nutrient Cycles35
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5: Photosynthesis23
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5: Respiration17
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5: ATP & Energy Transfer11
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6: Homeostasis57
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6: Nervous Coordination53
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6: Stimuli & Response62
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6: Muscles14
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7: Inheritance12
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7: Populations (Hardy–Weinberg)15
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8: Gene Mutations & Expression58
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8: Gene Technologies46
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8: Disease24
