Exam 1 Flashcards
Why is water essential for life?
Mineral dissolution to ionic forms makes them bioavailable, water allows for biochemical reactions to take place, and water is required for photosynthesis and respiration
Formation of Earth
4.568 BYA
Appearance of life
3.8 BYA
Oxygen in atm
2.5 BYA
Photosynthetic life
3.4 BYA
Cambrian explosion
540 MYA
Evidence of photosynthetic life
Microfossils (3.46 BYA), stromalites (3.45 BYA and 3.0 BYA), isotope fractionation (3.4 BYA in microbial mats)
Stromalites
Result of microbes growing in mats of cells that grow through sediment and form layers
Requirements for life
Liquid water, a stable environment, structural elements (CNPSOH), trace elements (mostly metals), energy (electrons, redox gradients)
Ancient earth
Hotter (more greenhouse gases despite weaker sun), energy from sun and volcanic activity and meteorites, reducing environment with simple organics present. Probably an RNA world (but heat complicates this). Sources: modern volcanic outgas, Miller-Urey experiments
Evidence for life from space
1984 Antarctic meteorite containing iron chains (potential from bacterial activity), amino acids, and PAHs (but all of these can be explained abiotically)
Causes of delay from photosynthetic organism arrival to O2 in atm
Reactions take time, organisms have to reproduce, and there can be changes in which rocks are present on the surface. Additionally, earliest photosynthetic organisms likely did not use O2 (Rubisco is sensitive to oxygen)
Variation in primary productivity
Cyclic wrt/ day and night and seasons (produces Keeling curve in combination with anthropogenic CO2 increase). The North dominates these variations because of its greater land and biomass
Photosynthesis
Energy harvesting (photons -> e- in PSI&II), production of ATP and NADPH (storage), then carbon fixation (CO2 -> Corg in Calvin-Benson cycle by Rubisco)
C3 plants
Single mesophyll cell, 85% of all plants, requires energy and CO2 simultaneously
C4 plants
Spatial separation between mesophyll and bundle-sheath cells allowing for temporal separation of stomata opening and carbon fixation in order to save water. Common in hot climates. More expensive than C3 energy-wise
CAM plants
Temporal separation within single mesophyll cell to save H2O. Common in hot and dry climates. More expensive than C3
Photosynthetic efficiency (net storage of glucose in plants)
Average 1-2%, max 5%
MRT
B/NPP
NCP
GPP-R_A-R_H
Tree in a bag
Assumptions/limitations: representative sample, tree functions the same in the bag as out of it (light, airflow, vapor diff.), must be timed properly to prevent suffocation, other organisms will be in the bag
Eddy correlation
Instruments suspended at different heights along a tower that measure CO2 to quantify its flux from trees into the atmosphere. Assumptions/limitations: measures whole ecosystem, expensive, limited by instrumentation
Generalization of land production
Create a leaf area index (relates leaf area to photosynthesis) for different species and ages of plants through field studies, then use cheap aerial/satellite images to convert from overhead area to total area by accounting for leaf layers, and then perform regression of leaf area duration to NPP - do durations because leaf area varies seasonally
Ocean production measurement
Travel to the ocean in boats with built-in labs, using rosettes to collect 8-20 samples at a time, and collect samples both within and outside of major algal blooms on the ocean surface; use ocean in a box (assumes that organisms function the same in different P, T, light, and nutrient flows) method or C-14 bottle method (assume representivity); then use satellite imagery to scale similar to land method (have to account for depth much greater than what satellites can see - lots of field data)
Global productivity trends
Land dominates in biomass, ocean dominates in productivity
Methods of quantifying food chains/webs
Length or connectance (links/#species^2). Connectance is typically 0.2-0.4
Trophic cascade
Changes in one keystone species change the whole web. Often occurs in top-down ecosystems where apex predators (i.e. starfish, wild dogs, wolves) keep the balance
Bottom-up ecosystems
Ecosystem balance is preserved by limiting nutrients/abiotic factors instead of a top predator
How do we know what things eat?
Observing, checking stomach or fecal contents, or using isotope fractionation (best). Involves measuring two isotopes and plotting them on a graph, then comparing species groupings. The nitrogen fractionation can be used to calculate trophic level (slope is consistent across all ecosystems, but still need to measure TL 1)
Key differences in assimilation efficiency (AE)
Carnivores > herbivores (efficiency is proportional of similarity of food structure to consumer structure; meat to meat vs. plant to meat)
Key differences in production efficiency
Cold blooded individuals are generally more efficient because they need to respire less because they do not need to constantly be keeping warm
Largest water reservoir
Ocean (96.5% of all water)
Least MRT water reservoir
Biosphere (hours to days)
Largest water flux
Atmosphere: precipitation and evapotranspiration
Part of water cycle most impacted by humans
Groundwater & groundwater extraction flux
Potable water stats and challenges
Currently use 10% of all fluxes and 50% of all storage, 90% of use is for agriculture, 25-30% of humans live where use > recharge, resources are becoming degraded and shrinking because of use
Largest carbon reservoir
Rocks: inorganic (60 million Pg), organic (14 million Pg)
Least MRT carbon reservoir
Biosphere (hours)
Largest carbon flux
Photosynthesis & respiration; growth & decay
Part of carbon cycle most impacted by humans
Atmosphere and fossil fuel reservoir by fossil fuel to atmosphere flux
Most changemaking part of the carbon cycle
Atmosphere
Where emissions end up
1/3 atm storage, 1/3 biosphere, and 1/3 ocean storage (acidification)
Chemical carbon pump
The carbonate system. Henry’s Law drives equilibrium of CO2(g) with CO2(aq), CO2(aq) combines with H2O to form H2CO3, which can dissociate into HCO3- and further into CO32-, releasing H+ as it does (drives acidification). General schema is: CO2 in, CO2 consumed, more CO2 in
Biological carbon pump
Photosynthesis/C fixation. Henry’s Law drives equilibrium of CO2(g) with CO2(aq), CO2(aq) is used by phytoplankton and turns into C6H12O6, which can be eaten, used to respirate, or sink to the deep ocean. General schema is: CO2 in, CO2 consumed, more CO2 in
Percentage of dead phytoplankton eaten in shallow ocean
95-99%
Percentage of dead phytoplankton that sink to deep ocean
1-5%
pH of ocean water currently
8-8.2
Important facets of the P cycle
No gas phase; trace amounts of P in dust is very important for downwind ecosystems even though it is small compared to the overall cycle; on a human timescale, the P cycle is a “conveyor belt” and P is essentially a non-renewable resource
How much P is good?
P is necessary for life so there needs to be enough but not too much: “who is growing?” –> eutrophication is bad (when P is limiting factor, usually is for freshwater ecosystems)
P cycle key experiment
Experimental Lakes District in Canada: scientists had two similar size lakes near each other but isolated from one another. They observed them both to determine similarity before adding P to one of them. They observed algal blooms in the one with P added
Limiting nutrient in freshwater
P
Limiting nutrient in nearshore ocean
N
Limiting nutrient in open ocean
N or Fe
Why is eutrophication bad?
Excess nutrients cause excessive and fast growth of algal blooms. As these blooms decay, they use up all the DO, creating hypoxic conditions in which most things die (including fish). These other dead things add to the decomposition oxygen demand
Solutions to the one-way conveyor belt of the P cycle
1) Wastewater treatment to recover resources (C, N, and P); 2) stormwater at both local (rain garden) and municipal (constructed wetlands, street cleaning, other BMPs) scales; and 3) implementing “right-size” (what kind, how much, and when) fertilizer application to reduce contamination from ag runoff (see Lake Erie)
“peak x”
We dig up x and use it but might run out of it; “peak” refers to when we will have the most of it
Largest P reservoir
Ocean sediments (4x10^9) and soils (200,000)
Largest P flux
Internal cycling in ocean (1000) and land (60) ecosystems is large; but functionally river flow (21) and mining (12)
Part of P cycle most impacted by humans
Decrease in rock storage and increase in flux of P to the ocean from runoff because of mining and agricultural application
Importance of N to organisms
Used in DNA, RNA, proteins, and to make chlorophyll
Largest N reservoir
Atmosphere (N2 is 79% of atm)
Abiotic N fixation
Very small; cosmic radiation, lightning, and meteorites
Biotic N fixation
Bacteria (including the rhizosphere: bacteria living on root nodules of legumes, alfalfa, and clover)
Anthropogenic N fixation
Haber-Bosch process (very energy intensive = $$$); feeds 50% of humans
Largest N flux
Biological fixation and denitrification; but anthropogenic fixation is increasing
N flux most impacted by humans
Removal of N from the atmosphere (Haber-Bosch) and release of NOx
Formation of acid rain
NOx and SOx combine with O2/ozone, sunlight, and water vapor in the atmosphere to form nitric acid and sulfuric acid, respectively; mostly mitigated by scrubbers (plants) and catalytic converters (cars)
Largest S reservoir
Atmosphere and lithosphere are primary reservoirs, S is also stored biologically
Natural S fluxes
Bacteria biological processes: sulfate reducing and oxidizing bacteria use sulfur as an electron acceptor and donor, respectively, while purple sulfur bacteria use H2S in photosynthesis. Also seaspray aerosols and volcanic activity
Largest S flux
Human combustion (coal is 1-5% S and oil is 2-3% S) is about equal to all natural source emissions and can be up to 90% of fluxes to the atmosphere in industrial areas
Parts of S cycle most impacted by humans
S to atmosphere from lithosphere by combustion; storage of S in plants due to agricultural intensification
Ecosystems where light is the limiting factor
Deep ocean, tropical rainforest (at floor), tundra (in the winter)
Ecosystems where nutrients are the limiting factor
Surface ocean (N/P/Fe), freshwater (P usually, but can be N), tropical rain forest
Ecosystems where water is the limiting factor
Desert, tundra (summer)
Temperature
Tundra (winter)
Experimentally determining limiting factor
If you add X and see growth, X is the limiting factor
When N-fixing microbes have an advantage
When N is the limiting factor
When N-fixing microbes are at a disadvantage
When P is the limiting factor
Mathematically determining limiting factor
Find ratios of (plant need/abundance in H2O) and the highest ratio is limiting
Redfield ratio
Deep ocean water composition matches surface ocean phytoplankton chemistry. For areas without currents, the C : N : P : Fe ratio is generally 106 : 16 : 1 : 0.005
Niche
For one species, all aspects of their way of life
Fundamental niche
Everywhere an organism could survive in the absence of competition; function of everything an organism needs to survive
Realized niche
Subset of the fundamental niche where the species actually lives; an organism’s place/role/interactions in an ecosystem
Coexistence
Different realized niches; can still be competition, but their niches do not overlap 100%
Population growth in the presence of unlimited resources
Exponential growth; can occur in reality for a short period of time
Population when resources are limited
Logistic growth up to some carrying capacity K determined by environmental factors; more common in nature
Stressors
Wildfires, hurricanes, drought, habitat destruction or compartmentalization, volcanic eruptions, floods, invasive species, disease, eutrophication, climate change, and chemical/physical pollution
Kinds of stress
Species-specific vs whole ecosystem, momentary vs long-term disruption
Kinds of stability
Ideal (horizontal), cyclically stable within bounds (sine curve; more realistic), non-cyclically stable within bounds (what is reasonable fluctuation vs. stress: has to be determined empirically)
Trajectories after perturbation
Collapse (not resilient) or bounce back (resilient; elasticity describes time to bounce back)
Indicator species
Usually the least resilient species: first to decline, last to recover
Measures of ecosystem “goodness”
Biodiversity, connectedness, productivity, physical extent, total biomass, similarity to historical conditions, indicator species health
Measures of ecosystem “stability”
Biodiversity: both species diversity and genetic diversity within species, resilience/inertia: resistance to change in state, elasticity (related to growth rates)
Promoters of stability
Biodiversity, connectedness
What resources do humans need?
Water: liquid, fresh, safe, and potable; food (structural/trace elements and energy); habitat./shelter; and oxygen/clean air
What things do humans need to NOT be there?
Wars, disease, natural disturbances (these are all anomalies in a model)
Projected level off of human population
10.3 billion
Drivers of population leveling off
Replacement rate (# children per reproducing person) tends to decrease as countries industrialize. Birth rates decreases due to access to family planning, access to medical care, culture shifts (religion, societal norms, awareness of population level), economic and workforce changes (less child labor), education and workforce opportunities for women, the cost of having a family, and a decrease in child mortality
The demographic transition
Birth rates and death rates are initially equal, so population is stable. The death rate starts dropping due to medical advances but there is a time delay of information/realization so birth rates remain at previous rates, leading to a large population increase. Then birth rate drops to death rate and population growths slows and then stops or reverses
How is carrying capacity of the Earth determined?
Ultimately linked to food production, which relies on availability of other resources (water, space, nutrients)
Ecological footprint
Food, water, other resources. 1.8 ha per human is available globally but we currently consume 2.2 ha per person (highest consuming countries consume more than this). Can also be thought of as the number of planets needed to sustain the present consumption rate - we passed 1 planets’ worth in the 1980s
When is a resource renewable?
Harvesting rate =< regeneration rate
Positive feedback
System reinforces the response and spirals out of control
Negative feedback
System mitigates the response and stabilizes
Global environmental change indicators
Human population increase, atmospheric carbon, species decline/extinction, natural disaster frequency and intensity increases, sea level rise, and temperature
Evidence of human population increase
Counting people, historical records, and long archaeological records
Evidence of atmospheric carbon
Mauna Loa records, ice cores (400,000 years of record)
Evidence of species decline and extinction
Temporal record of species inventory and records of human/species conflicts
Evidence of sea level rise
Direct measures, sediment records, and record of historical maps (anecdotal/qualitative)
Evidence of temperature
Written records and isotope fractionation (ice cores, # isotopes)
Metrics of “what matters”?
1) human survival 2) with or without mass suffering and 3) life as we know it stays
Ways to respond to global change
Mitigation, adaptation, and geoengineering
Mitigation techniques
Renewable energy, sustainable fisheries management, use less plastic, building energy efficiency, sustainable agriculture, discourage long-distance shipping, eat less beef, resource recovery > waste
Adaptation techniques
Move coastal cities, assisted species migration, genetic modification to allow for crop survival, urban heat island mitigation, xeriscaping, water use decreases, and zoning
Geoengineering nuances
How do we know what to do? How do we know what will happen if we do? What are the side effects? Doing nothing also has bad consequences. What about psychology: will people do less mitigation and adaptation
Ecosystem services categories
Provisioning, regulating, habitat/supporting, and cultural
Methods of valuation
Replacement costs, what are people willing to pay?, avoided costs
