Primary Productions Flashcards
The process by which autotrophic organisms (mainly plants) take in CO₂ from the atmosphere through photosynthesis to produce organic matter.
primary production
Why is primary production important?
It is the base of the food chain, driving energy and carbon flow in ecosystems.
What percentage of Earth’s surface is vegetated?
71% of the terrestrial environment is covered by vegetation.
The total amount of CO₂ converted into sugars by photosynthesis.
Gross Primary Production (GPP)
The CO₂ lost as plants break down sugars to generate energy for growth and maintenance.
Plant Respiration (RP)
The amount of energy available for plant growth and herbivores.
Net Primary Production (NPP)
NPP = GPP – RP
Net Primary Production (NPP)
The total organic carbon accumulation in an ecosystem.
Net Ecosystem Production (NEP)
Formula: NEP = NPP – (Rh + FD + FL)
Net Ecosystem Production (NEP)
Respiration by decomposers.
Rh
Carbon loss from fires, harvesting.
FD
Carbon loss through leaching.
FL
Why is carbon used as a currency for measuring GPP?
CO₂ changes in the atmosphere are easier to track than direct energy accumulation.
How do scientists measure GPP at the leaf level?
By tracking CO₂ exchange
Respiration (RP) is measured.
In darkness
GPP is determined by subtracting RP.
In light
The balance of CO₂ in and out of an ecosystem, measured using eddy covariance.
Net Ecosystem Exchange (NEE)
Formula: NEE = CO₂ out – CO₂ in
Net Ecosystem Exchange (NEE)
If NEE is more negative
More carbon is stored.
If NEE is more positive
More CO₂ is released.
What is the main pigment responsible for photosynthesis?
Chlorophyll
absorbs light in red and blue wavelengths.
Chlorophyll
The light level where photosynthesis = respiration, meaning no net carbon gain.
compensation point in photosynthesis
How does temperature affect photosynthesis?
Photosynthesis follows a unimodal response
Increases with temperature up to an ______
optimum
Declines at high temperatures due to ______
enzyme breakdown
Why do plants close their stomata in dry conditions?
To reduce water loss, but this also limits CO₂ uptake, reducing photosynthesis.
A wasteful process where Rubisco binds to O₂ instead of CO₂, reducing photosynthesis efficiency.
photorespiration
How do C3 plants fix carbon?
They use Rubisco to fix CO₂ directly in the Calvin Cycle.
Why are C3 plants inefficient in hot, dry conditions?
Photorespiration reduces CO₂ fixation, wasting energy.
Examples of C3 plants?
Wheat, rice, trees, most plants.
How do C4 plants avoid photorespiration?
They separate CO₂ fixation into two cell types
_______ Cells fix CO₂ using PEP carboxylase, forming a 4-carbon compound.
Mesophyll
__________ cells release CO₂ for the Calvin Cycle, preventing O₂ interference.
Bundle sheath
Why are C4 plants more efficient in warm environments?
They use water more efficiently and have higher photosynthesis rates under high light and temperature.
Examples of C4 plants?
Corn, sugarcane, grasses.
How do CAM plants conserve water?
Stomata open at night to take in CO₂.
CO₂ is stored as an organic acid and used during the day when the stomata are closed.
Why do CAM plants grow slowly?
They limit water loss but also have low productivity.
Examples of CAM plants?
Cacti, succulents, pineapples.
What determines vegetation type in a biome?
Temperature, water availability, and disturbance (fire, grazing).
Characteristics: Cold, low vegetation, permafrost
Ex: Mosses, shrubs (C3)
Tundra
Characteristics: Evergreen conifers, acidic soil
Ex: Spruce, pine (C3)
Taiga (Boreal Forest)
Characteristics: Deciduous trees, moderate rain
Ex: Oak, maple (C3)
Temperate Forest
Characteristics: Deep-rooted grasses, seasonal rain
Ex: Tallgrass (C3-C4)
Grasslands
Characteristics: Low water, slow growth
Ex: Cacti (CAM), shrubs (C4)
Deserts
Characteristics: Grass-dominated, scattered trees
Ex: Acacia, grasses (C4)
Savanna
The total leaf area per unit ground area – determines light absorption and photosynthesis.
Leaf Area Index (LAI)
Which biome contributes the most to global NPP
Tropical rainforests (60% of global NPP)
Why are forests twice as productive as grasslands per unit area?
They have higher LAI, meaning more light absorption and longer growing seasons.
