Lecture 11
Weather is short-term atmospheric conditions; What is the long-term average of those conditions?
Climate
Ecologists can estimate productivity by harvesting and weighing dry biomass, or by using satellites to detect what pigment?
chlorophyll (remote sensing)
Fungi belong to which domain of life?
Eukarya
What is the largest pool of nitrogen on Earth, but most primary producers can't use it directly?
The atmosphere (as N₂ gas)
A tick now found in Michigan and a flower blooming earlier each spring are examples of what two documented types of change.
Shifting species distribution (range) and a shift in phenology
CO₂ is a trace gas, not a main component of the atmosphere, but it matters because it does what as part of the greenhouse effect?
Absorb and re-emit heat, trapping it near Earth’s surface?
Which biome accounts for the largest share of global NPP, even though its rate per unit area is low?
Open oceans
Fungal cell walls are made of what tough material, the same one found in arthropod exoskeletons?
Chitin
Which two inorganic forms of nitrogen can be taken up by primary producers?
Ammonium (NH₄⁺) and nitrate (NO₃⁻)
An individual plant blooms earlier in warm years with no genetic change. This response is called ---, not adaptation.
Plasticity
Terrestrial photosynthesis (~120 GtC) and respiration (~119 GtC) dwarf the 7.8 GtC from fossil fuels, yet fossil fuels drive the CO₂ rise. Why?
That natural fluxes nearly balance, while fossil fuel burning is an unbalanced, one-way addition of carbon from a long-term reservoir?
A researcher studies a 1 m² grassland plot for one growing season. The plants fix 900 g C through photosynthesis and release 400 g C through cellular respiration. No herbivores graze the plot. How much carbon is available to consumers, and how much new plant biomass accumulated?
500 g C/m² (NPP = GPP − R = 900 − 400)-- The plot gained 500 g C/m² of biomass because nothing was eaten.
How do fungi (chemoheterotrophs) digest food?
Hint: They release digestive enzymes into the environment and then do this.
Absorb the nutrients (Digestion happens outside the fungal body.)
A "pool" of nitrogen, like the atmosphere or the soil, is also called this.
Reservoir
Warming reduces ocean NPP because stratification of the water column does ---.
Limit mixing, so nutrient-rich deep water doesn’t reach the sunlit surface where phytoplankton live
Atmospheric CO₂ is rising while δ¹³C is falling. Explain how this points to fossil fuels.
Fossil fuels come from ancient photosynthetic organisms, which are rich in ¹²C, so adding that carbon lowers the ¹³C/¹²C ratio
In an Arctic tundra ecosystem, grasses produce 50,000 kJ/m²/year of NPP. Lemmings eat the grasses, arctic foxes eat the lemmings, and golden eagles eat the foxes. Assuming 10% of energy is transferred from each trophic level to the next, how much energy per m² per year reaches the eagles? And where does the rest of the energy go at each step?
50 kJ/m²/year ; At each step, 90% is lost as heat from cellular respiration, or never becomes consumer biomass
A mushroom is only the small visible part of a fungus. The huge hidden network of hyphae underground is called this.
Mycelium
In anoxic environments, some decomposing bacteria use NO₃⁻ in respiration, converting nitrogen back to N₂. What is this process called?
Denitrification
The people most harmed by climate change are often those who contributed the least to emissions. Name this pattern and one health impact.
Unequal burden (the most vulnerable are least responsible), with impacts like heat illness or disease vectors expanding their range
A skeptic claims modern warming is natural. Give two independent lines of evidence from this lecture that humans are the cause.
(Any two): the δ¹³C isotope signature of fossil fuel carbon, models matching observations only when human causes are included, and CO₂ levels far above anything in the ice core record
A pond has a GPP of 20,000 kJ/m²/year. The producers use 40% of their GPP in cellular respiration. Energy transfer between trophic levels is 10%. The pond's top predator, a tertiary consumer, needs 40 kJ/m²/year to sustain its population. Can the pond support it? Show how much energy actually reaches the tertiary consumers
No; Only 12 kJ/m²/year reaches the tertiary consumers (30% of what they need)
Mycorrhizal fungi wrap around plant roots. Name what the fungi give the plant and what the plant gives the fungi in return.
Phosphate (fungi to plant) ; Carbohydrates such as glucose and other sugars (plant to fungi)
Put these events in order, starting with fertilizer runoff from the Mississippi River: phytoplankton die, oxygen declines, algal bloom, decomposers increase, huge detrital pool.
algal bloom → phytoplankton die → huge detrital pool → decomposers increase → oxygen declines (dead zone)
Explain why falling solar costs combined with growing battery capacity make grid defection economically viable.
Batteries store solar power for times when the sun isn’t shining, solving the intermittency problem