9/30 Flashcards
Molecules
combinations of two or more atoms (N2, CO2, NaCI, H2O)
Atoms held together by bonds (strongest to weakest):
- Covalent bond
- Ionic bond
- Hydrogen bond
Covalent bond
atoms share electrons (CO2)
Ionic bond
atoms bound by electrical attraction (NaCI = Na+ + CI-)
Hydrogen bond
“partial ionic bond” between molecules
Describe a water compound
Partial charges at opposite ends of molecule
“Polar” molecule
High heat capacity
measure of amount of heat energy that must be absorbed by the substance to raise the temperature 1 degree C
Concentrations of H+ (protons) and OH- (electrons) determine pH in an ________ solution.
aqueous
The solution is acidic if
H+ (protons) concentration greater than OH- (electrons)
The solution is basic if
OH- (electrons) concentration is greater than H+ (protons)
T or F: only an acidic solution can be lethal.
F: Both an acidic and basic solution can be lethal
What are examples of high/basic pH?
NaOH (sodium hydroxide), ammonia, seawater
What are examples of low/acidic pH?
acid rain, stomach acid, lemon juice, car battery acid
What are examples of neutral pH?
pure water
What elements are important for soil health and plant growth?
calcium, phosphorus, potassium, sulfur, nitrogen, magnesium
What are the effects of a basic soil?
nutrients (e.g., P, Mg) not soluble (unavailable to plants)
Dark leaves indicates _________ limitation/deficiency
phosphorus
What are the effects of an acidic soil?
toxic metal ions (e.g., Al) more available/soluble
As pH drops/Al availability increases, plants
grow slower
Atoms
elemental units (“building blocks of matter”)
Isotopes
Same number of protons, but different numbers of neutrons
What are the two isotopes of hydrogen?
- Deuterium
- Tritium
Deuterium
stable isotope (not radioactive; does not disappear)
Tritium
radioisotope (radioactive, spontaneous decay occurs)
Mass = ______ + ________
protons; neutrons
What are the stable isotopes of carbon?
12C, 13C
What are the stable isotopes of nitrogen?
14N, 15N
Which carbon isotope is the atmosphere mostly made up of?
12C
Which carbon isotope does grass and shrubs discriminate against?
13C
T or F: Shrubs discriminates more strongly against 13C than grass
T
Grass and shrubs use the CO2 with the preferential isotope, which is
12C
Describe the salmon life cycle
Salmon eggs hatch in a freshwater stream
Return back to the stream they were born in
Female lays eggs; male fertilizes eggs
Salmon die and rot
What are the four different independent developments of agriculture?
China: rice
Fertile crescent: wheat
Central America: potatoes
Mesoamerica: Corn, squash
What are the functions of soil?
Regulates water cycle (controls flow of rain, snowmelt)
Productivity
Filters pollutants (sequester or detoxify)
Nutrient cycling
- Organic → inorganic
Autotrophic plants
CO2 + H2O → carbohydrate
CO2 + H2O + NO3 + PO4 → protein
Heterotrophic fungi, bacteria
Carbohydrate → CO2 + H2O
Protein → CO2 + H2O + NO3 + PO4
Soil = mix of ____ + ______
organic; inorganic
Rhizosphere
interface between plant roots and soil
Rhizobium bacteria are able to break down strong ______ bonds
triple
Nitrogen-fixing bacteria conversion
Convert N2 (gas) → NH4 (ammonium)
Plants → N (organic)
Soil decomposers: N (organic) → NH4 (ammonium) → N2 (gas)
Where are mycorrhizal fungi located?
partly inside and outside the plant root
Describe the relationship between mycorrhizal fungi and plants
Plant root gives some carbohydrate to fungi
Fungi take in water and nutrients from soil environment and feed it to plant
The relationship between mycorrhizal fungi and plants is called a
mutualistic symbiosis
How are non-native earthworms a threat to soil?
Reduce soil biodiversity, productivity
What percent of all freshwater use is for crop irrigation?
70%
Why is over-irrigation a problem?
Over-irrigation → waterlog plant roots → poor growth, death
Soil becomes soggy
Roots need oxygen
Too much water
Oxygen diffuses much slower
Plants are not getting enough oxygen
Salinization
buildup of salts in surface soil layers
Describe the process of salinization
Sfc evaporation removes water, leaves salts:
- Water comes up to surface and evaporates
- Salts in the water do not come up to surface and are left behind
What is the problem with conventional irrigation practices?
< half of water reaches plants
Most of the water released from the rotators is evaporated
Why is drip irrigation a better irrigation practice?
Conserves water, saves money and reduces salinization
Water drips out slowly (reduces chance of evaporation)
As a result of over-fertilization, rain washes off _____ and _____ from lawn into water
nitrogen; phosphorus
Give examples of how isotopes can be used to better understand environmental process?
[Marine 15N/14N] ≠ [terrestrial 15N/14N]
• Marine food —> salmon body —> death, decay —> terrestrial
• Terrestrial invertebrate animals near stream: up to 70% of N in body
• Salmon acts as fertilizers for animals that lice on land far from the ocean
• Salmon collect N from the ocean
• Salmon deposit N after death
