Midterm 2 Environmental Science

Energy

Ecosystems can be viewed as self-contained for all but what?

Watershed

practical delineation of boundaries; determined by topography; united by chemical cycling

Ecosystem energy flow

electromagnetic → chemical → electromagnetic

Fixed by producers

How does energy enter the ecosystem?

No

Is most electromagnetic energy within the visible light spectrum?

1st Law of Thermodynamics

Conservation of energy

transformed

energy not created or destroyed, merely

2nd Law of Thermodynamics

Entropy; energy transfer is never 100% efficient; some is always lost as “unusable” thermal energy

Gross production

increase in stored energy before use

GP = B2-B1+R

Gross Production (GP) Equation (B2 and B1 are biomass at times 1 and 2, R is respiration between times 1 and 2)

Net Production

Change in biomass over a given time

NP=GP-R=B2-B1

Net Production (NP) Equation (B2 and B1 are biomass at times 1 and 2, R is respiration between times 1 and 2, GP is Gross Production)

Measures of Biological Production

Biomass (kg or Gt), energy stored (calories), carbon stored (kg or Gt)

Respiration

chemical energy used for cellular work; organic matter + O2 → energy to CO2 + H2O

90%

% of energy lost as heat per trophic level

10%

% of biomass transfer per trophic level

Primary succession (colonization)

establishment and development of an ecosystem where one did not previously exist

Secondary succession

reestablishment of an ecosystem following a disturbance i.e. hurricanes, floods, fires, etc.

Dune succession

formed along sandy shores → grasses establish → grass runners stabilize soil → other species can germinate

Bog succession

sedge puts out floating runners → wind blows particles into mat of runners → seeds land and germinate → mat thickens w/ shrubs and trees → water body fills from bottom → mat and sediment meet and form solid surface → area farther from shore vegetation still floats

General succession

autotrophs (pioneers, stabilize environment, N-fixing) → autotrophs (rapidly growing, seeds spread quickly) → larger autotrophs (trees, shrubs, etc.) → mature ecosystem

N Fixation Rates

Peaks in early succession periods; slows as ecosystem matures

P Presence in ecosystem

Decreases as succession develops; runoff, soil prevents rocks from weathering

Biogeochemical cycle

complete path an element takes through atmosphere, hydrosphere, lithosphere, and biosphere

amino acids

early bacteria created what?

oxygen in atmosphere

occurred two billion years after development of photosynthesis

prokaryotes

no organelles or nuclei; energy from fermentation → CO2 and alcohol; single or chain structures; no complex structures

eukaryotes

formed 2 billion years ago; contain organelles and nuclei; respire w/ oxygen; can form 3D bodies

multi-celled eukaryotic organisms

formed 1 billion years ago

plants, animals, fungi

formed 700-500 million years ago

Cambrian explosion

name of event occurring 700-500 million years ago

24

number of elements necessary for all organisms

6

number of “macro” elements

18

number of “micro” elements

true

Crucial to maintain even ratio of elements for life?

true

Some elements have neutral effects regardless of ratio?

unstable

Elements of 5-8 are what?

rare

Elements greater than 30 are what?

odd elements (most elements formed by fusion, which produces even elements; odd elements only occur from fission of evens)

Are even or odd elements rarer?

N(7) and P(15)

What are essential, odd, limiting nutrients?

cycles

flux B to A, flux A to B

Geologic Cycles

rates of movement, formation, erosion change w/ time; physical, chemical, and biological processes; tectonic, hydrologic, rock, and biogeochemical

Tectonic Cycle

creation and destruction of lithosphere; about 100 km thick, 15 large plates

lithosphere

Earth’s crust

plate tectonics

movement of Earth’s crust (2-15 cm/yr)

energy for plate tectonics

powered by heat generated from decaying unstable isotopes in the Earth; form convection currents in the mantle

divergent boundaries

plates moving apart

convergent boundaries

plates colliding

transform boundaries

plates moving past each other

hydrologic cycle

evaporation, transpiration, precipitation, runoff, and groundwater

rock cycle

uses tectonic cycle for energy and hydrologic cycle for water

igneous

formed from magma

metamorphic

formed from other rocks changed by heat and pressure

sedimentary

formed by sediment layers pressurizing underground

carbon and rock cycles link

CO2 → CaCO3 (calcium carbonate or lime stone); (atmospheric CO2 decreases during mountain-building periods due to lime-stone production!!)

Physical Weathering (freeze, thaw)

generate sediment such as gravel, sand silt, and “Rock flour” which are nutrient-dense

Chemical Weathering

weak acids in water (i.e. acid rain) dissolve chemicals from rocks and release ions

10^15 g

Gt = ?

10\.2 Gt/y

human impact on carbon cycle

7\.6 Gt/yr

fossil fuel impact on carbon cycle

120 Gt/yr

Plants impact on carbon via photosynthesis + respiration

560-700+ Gt

Plant carbon storage

1500 Gt

Soil carbon storage

92\.4 Gt/yr “in”, 90 Gt/yr “out”

Ocean carbon impact

carbon impact on silicon cycle

carbonic acid in rain weathers silicate-rich rocks → releases Ca2+ and HCO3- → used for shells by marine animals

Nitrogen

Necessary for proteins and DNA; free form is 78% of atmophere BUT most organisms cannot directly use this

Nitrogen cycle

converted to NO3- or NH4+ by N-fixing bacteria → 60% in biosphere is from humans

Nitrification

NO3- forming by decaying organisms or from NH4+

N-fixing bacteria

essential for ecosystems; form symbiotic relationships w/ plants (pioneer species)

Denitrification

process of releasing fixed N back to N2 in atmosphere, completing cycle

Industrial fertilizer

N → NH4+; N combines w/ O at high temps → oxides of N lead to air pollution → acid rain and smog

Human Impact on Nitrogen Cycle

coastal eutrophication; add access N via fertilizer (ends up in runoff); destruction of wetlands (denitrification zones) → increase in N2O

Phosphorous cycle

limiting factor for plants and algae; no gaseous phase → slow rate of transfer; organisms → soil → runoff → oceans → land via guano/migrating fishes; humans mine marine deposits or guano to obtain; enters system via weathering of rocks

Ecosystem Serives

processes by which environment produces resources or goods (i.e. clean water, timber, pollinators, fish, etc.)

Services Ecosystems Provide

moderate extreme weather/impacts; mitigate floods/droughts; disperse seeds; shield UV rays; pollinate vegetation/crops; regulate diseases; purify air and water; stabilize climate; create/preserve fertile soils; maintain biodiversity; moderate coastal erosion (preventing property destruction); control pests; prevent landslides; detoxify/decompose wastes; move/cycle nutrients

Pros of economically evaluating environment

factors nature into economic decisions; speak “their language” ($$); better than not factoring it in; shows true costs; emphasizes function; highlights value of the environment in the economic world

Cons of economically evaluating environment

short-term economic costs; could be unethical; ignores intrinsic value, only highlights function; solely anthropocentric

evaluating economic value

market prices, circumstantial evidence, surveys

Hedonic Pricing Method

estimates value by direct impact on other good; can estimate cost of environmental quality (i.e. pollution), aesthetics, recreation; willingness to pay to avoid areas; property value decline

Market Prices

Hedonic Pricing and Travel Cost Methods

Travel Cost Method

how much are people willing to pay to visit site?

Circumstantial Evidence

Damage cost avoided, replacement cost, and substitute cost methods

Surveys

Contingent value method: how much would you pay for a service if it disappeared?

value of ecosystem services

roughly $33 trillion, or 2x world’s GNP

reasons to value biodiversity

utilitarian, public service, moral, theological, aesthetics, recreational, spiritual, creative, ecological

genetic diversity

genes, base pairs (alleles)

habitat diversity

different kinds of habitats in a given area

species diversity

species richness, species evenness, species dominance

species richness

total # of species

species evenness

relative abundance of species

species dominance

the most abundant species (like mode)

1\.5 to 3 million

number of (known) species on Earth

species categories

Kingdom (domain), Phylum, Class, Order, Family, Genus, Species

Bacteria, Archaea, and Eukarya

3 Kingdoms/domains

Protection policy considerations

Protect sheer number of distinct species? Protect function of species? Protect rare DNA? Protect “charismatic” fauna? Protect habitat over species?

Biological Evolution

change in inherited characteristics/frequency of alleles over generations/time; decided by environmental conditions

amino acids → proteins

Alleles in DNA code for?

New species arise via

Competition for scarce resources, individual’s survivability, “the fittest” reproducing

Four processes leading to evolution

mutation, natural selection, migration, genetic drift

Mutation

error in DNA reproduction; possibly caused by radiation, viruses, chemicals, etc.; could be lethal; adds genetic variability; in rare cases new species is formed in one generation (almost always plants)