Biosphere

Question 1

Define biosphere

Answer 1

‘The sum of all ecosystems on Earth’ or ‘the layer of the planet Earth where life exists’

Question 2

Key features of the biosphere e.g. Vernadsky, 1926

Answer 2

• Materially closed, energetically open
• Activated by radiation (V, 1926)
• Gaia Hypothesis; organism interaction, synergetic self-regulating complex system (Lovelock & Margulis)

Question 3

How are biospheric boundaries explained/described?

Answer 3

Most of biosphere (largest organisms) beneath troposphere but bacterial bioaerosols in statosphere. Lower boundaries in deepest crust, some bacteria 3000m down - limited by temp. Depth of live ocean unknown but 75% of biosphere is in the oceans

Question 4

What is entropy?

Answer 4

Level of disorder - life requires low to high internal entropy (disordered, low energy to ordered, complex high energy state)

Question 5

What is the key input to the biosphere?

Describe photosynthesis.

Answer 5

All energy from the sun - solar energy transformed to chemical energy through photosynthesis (CO2+H2O -> C6H12O6+O2)

Question 6

How can you describe soil and what are its vital functions?

Answer 6

The upper layer/skin of Earth’s crust OR as dynamic/complex 3 phase system (solid, liquid, gas). Supports plant life, habitat for microorganisms, storage/filtration and transformation

Question 7

Pedogenisis - what are the inputs/outputs

Answer 7

Inputs - mineral weathering from rocks, organic matter from leaf litter/roots, carbon levels higher in soils than in the above atmosphere (e.g. Wetlands)

Outputs - wind/water erosion and leaching, minerals lost by percolation

Question 8

Pedogenisis - mixing and transformation

Answer 8

Mixing - bioturbation (orgs. move soil and aerate it) and leaching

Transformation - chemically through dissolving and precipitation/biologically through decomposition

Question 9

What affects the composition of soil?

Answer 9

Parent material - soil forms on rock surfaces, plays role in weathering rates and pH

Climate - temp affects weathering/decomp rate, rainfall affects this and matter redistribution, veg resulting from climate determines org matter

Topography/hydrology - soils shallow on steep gradient. Water logging alters mineral chem/decomp rates

Question 10

Soil fertility - what are the key features of soil and what are they affected by

Answer 10

Water, air and nutrients determine fertility, and these are affected by the texture, structure of porosity of soil

Question 11

Soil fertility - what is the role of water, air and nutrients?

Answer 11

Water - GPP is lowest in soils with low water availability, TEXTURE of small particles like clay = higher field capacity (and vice versa)

Air - soil aeration influences availabiltiy of nutrients, microorganisms need oxygen and roots need air for respiration

Nutrients - in soil solution, absorbed to clay particles as ions (nutrients mostly +charged metals)

Question 12

Give 3 main human impacts on soils, describe them

Answer 12

Compaction - infiltration capacity reduced, increased runoff and floods, leaching encouraged

Loss of organic matter - conversion to agriculture, deforestation ‘slash & burn’, desertification and nutrient cycle break down, org matter improves water holding capacities and aeration, supplies nutrients, binds minerals, reducing erosion rates

Erosion - removal of veg, over grazing = soil surfaces exposed to rainfall/wind, increasing leaching and erosion rates, loss of topsoil = desertification
(Many others like contamination, acidification, salinisation…)

Question 13

Define these key terms - biodiversity, genetic drift and speciation

Answer 13

Biodiversity - “the diversity within species, between species and of ecosystems “ (UN, 1992), the variability among living orgs from all sources

Genetic drift - the change in frequency of a gene variant (allele) in a population due to random processes which may cause some alleles to disappear, differing from natural selection as it does NOT produce adaptation or guarantee extinction

Speciation - the evolutionary process by which reproductively isolated biological populations evolve to become a distinct species

Question 14

Name the 4 types of speciation. What MUST you have in order for speciation to occur?

Answer 14

Allopatric, peripatric, parapatric and sympatric - you must have genetic change and a reduction in gene flow between two populations so a new species emerges

Question 15

What are the two PHYSICAL types of speciation? Explain them.

Answer 15

Allopatric (different) = geographical barrier creates division between one species (to the extent that genetic interchange is prevented) e.g. continents, sea-level change, mountains

Peripatric (outside) = smaller groups to new environment resulting in genetic drift/natural selection and rapid divergence e.g. Darwin’s Galapagos finches finding unique niches on certain islands

Question 16

What are the two NON-PHYSICAL types of speciation? Explain them.

Answer 16

Parapatric (beside) = no barrier, but an environmental gradient/change (e.g. pH, rainfall, temp) leading to unequal gene flow

Sympatric (same/together) = no barrier, occurs within a group, more commong amongst insects/bacteria, very rare amongst higher organisms - disruptive selection and preferential mating e.g. apple/hawthorne berry flies

Question 17

How can conservation efforts be more focused?

Answer 17

Species redundancy - a species is ‘redundant’ if its removal has no effect on how constant the ecosystem is but it is dangerous “because of the uncertainties and impracticality” (Habiba Gitay, J. 1996).
Hard to predict how the removal of a species will change an ecosystem e.g. just because two species have similar characteristics does not mean they play the exact same role

Question 18

Classic experiments - who conducted a study showing the need for biodiversity?

Answer 18

David Tilman (2006) - decade long grassland experiment; stability defined by consistency over time and stability increased as no. of species increased
Higher biodiversity = productivity, stable PP, increased standard deviation meaning LESS RISK

Question 19

What is biogeography? What are the main factors that influence the distribution of a specific set of characteristics (biome, species, weather…)

Answer 19

The science that attempts to document and understand spatial patterns of biological diversity:

1. Climate
2. Topography
3. Interactions with other species e.g. predators
4. Humans

Question 20

What are biomes - how can they be defined?

Answer 20

Large-scale ecosystems containing smaller species and biotic/abiotic factors that interact.
Easily defined by CLIMATIC variables like rainfall and temperature, but also net radiation
Also BIOCLIMATIC variables e.g. PAR, precipitation, evaporation, runoff, water surplus and soil moisture
Remember Holdridge Life Zones System (1947) - evapotranspiration, precipitation, biotemperature

Question 21

Island biogeography - what is it and how is equilibrium determined?

Answer 21

The study of isolated ecosystems because of their ability to reach natural state of equilibrium…

1. The larger the area, the more species (genetic drift more likely)
2. Further away from mainland/similar habitat, the lower the number of species (less immigration, extinction increases)

Question 22

Give 3 main factors that control biodiversity - what is LDG?

Answer 22

Temperature and rainfall have positive relationship with no. species, altitude has negative
LDG = Latitudinal Diversity Gradient; the peak no. of species and plant hotspots occur at the tropics

Question 23

What are 5 reasons/theories for the abundance of life at the tropics? (High speciation, low extinction?)

Answer 23

1. Area - tropics largest proportion of Earth’s surface than any other biome (but not really big enough to account for what is there, a 10-fold increase would be needed to see species doubled…)
2. Age - high latitude ecosystems are younger, re-colonisation after ice age, more speciation opportunities at tropics
3. Productivity - aundant temp, water and light, enabling rapid photosynthesis, rapid nutrient/carbon cycling = many primary producers
4. Climate - warm = faster reactions, short gen. times, so more evolution
5. Dispersal rates - v. low DR, species have no need to migrate, specific adaptations (to constant climatic conditions, annual 24-26C), so genetic flow is limited and speciation is more frequent, particular niches

Question 24

What is biogeochemistry - name 3 key cycles

Answer 24

Studying how the biosphere functions, understanding life support systems; biological, geological and chemical processes of cycling elements through Earth system = Carbon, Nitrogen, Phosphorus

Question 25

Describe the Carbon Cycle - also refer to carbon storage e.g. why is the interaction between geological and biological processes so critical in allowing an oxygen-rich atmosphere?

Answer 25

Long-term and short-term; taken in by autotrophs, make compounds for heterotrophs, which then release C through respiration (aerobic), energy for work (photosynthesis). C released through chemical weathering also, buried into ceust through subduction, can be released through volcanism…

• For every fixed molecule of CO2, one O2 molecule released but only 700GT of C in atmosphere with 100k O, so NOT ALL CARBON in the BIOSPHERE
• Burial/storage in peatlands (coal) and oceans (oil/gas)

Question 26

Human impacts on the Carbon Cycle

Answer 26

Extraction and burning of fossil fuels - gas, oil, coal for industy, power stations, electricity etc.
Extracting fossil fuels releases C from sediments to atmosphere
Anthropogenic forcing disrupting naturally slow release in LT cycle, increasing by ~100x

Question 27

Describe the Nitrogen and Phosphorus cycles

Answer 27

Nitrogen = v. complex, many different oxidation states, N2 approx. 78% of atmosphere, not used by plants as easily as C is; a super stable, covalent triple bond which soil microorgs break down, key processes majorly impacted by fertilizers

Phosphorus = fewer forms than N or C, mainly phosphate, essential for cell membranes, DNA, RNA, ATP, Slow Cycle (main input is weathering), part transportation by dust e.g. Saharan fertilizing the Amazon

(Other key nutrients for life include potassium, sulphur, calcium, magnesium, iron etc.)

Question 28

What are the similarities/differences between N and P cycles?

Answer 28

Sims: effective at recycling within terrestrial ecosystems, transport to oceans through rivers, LT burial in sediments, added to Earth by fertilizers

Diffs: P cycle has no gaseous phase, main geological rock weathering input as opposed to biological N fixation

Question 29

What are the contemporary changes in relation to C, P and N cycles?

Answer 29

• Natural C fluxes being enhanced by anthro forcing, to which biosphere reacts, benefiting plants (better growth conditions, more photosynthesis)
• Increased N, positive fertilization effect
• Contemporary C cycle mitigating impacts at present (ocean and terrestrial storage sinks)
• +ve feedback loop = CO2 increases, temp increases, speed of reactions increases, more respiration = more carbon
• 1/3rd of C in marine sink, oceans more acidic, reduces their solubility, slowing sinks perhaps?

Question 30

Human impacts - outline issues surrounding land use (x3)

Answer 30

1. Population - growing, 7 billion in 2011, need food so large areas of land devoted to feeding us (36-40%!), nearly all NPP ‘appropriated’ for human use, about 1/4 PP of terrestrial biosphere used directly by human kind, loss of pristine land (83% not…), 50% NPP appropriation in Europe - HANPP, Krausmann et al. (2013)
2. Conversion of biomass - masses of land converted by 1980s, agricultrual land, degradation of soils etc.
3. Deforestation - agriculture, large-scale historical loss in Europe/N. America but still huge in the tropics. Since 1970, 1/5 Amazon degraded (700,000km2), discourses and tensions, some UK successful protection methods e.g. SSSI, Green Belt, ASI

Question 31

Human impacts - issues surrounding habitat loss and fragmentation (x5)

Answer 31

1. Island biogeography - fragmentation inreases “islands”, increasing extinction and dispersal rates
2. Ecology/extinction - key species depending on others, if lost = cascade of extinctions; 5 previous mass extinction events, 6th is coming? e.g. European Passenger Pigeon extinction of 4M by 19th century
3. Species invasion - habitat ecology changing for a range of reasons like invasive species whether intended or not e.g. 50% Arctic Skua British seabird pop decline as main diet has had to shift to risky pipefish after climate change induced sand eel decline
4. Climate Enveloping Modelling - models to track movement of climate envelopes and predictions of species migration as a result (minimal CC, high dispersal sees 9-13% species extinction by 2050, up to 52% for worst-case scenario)
5. Marine realm - CO2 higher than in last 700k yrs, increasing acidity, carbonates reduced, damaging corals, bleaching

Question 32

Human impacts - issues surrounding pollution (x2)

Answer 32

1. Key cycles; N, P and C - excessive N input, acidifcation, acid rain (N oxides dissolve in rain), accumulation of toxic soil compounds, P and N change alters species competition
2. Eutrophication; warmer temp + nutrient abundance = algal bloom - N/P concentrations increasing in freshwater due to leaching of fertilizers (and increased runoff, soil compaction etc.), decomposition of dead plants consumes oxygen, animal species lost

Question 33

Human impacts and potential solutions?

Answer 33

Humans having massive impact on biodiversity - need for land increases resulting in further habitat loss, also climate change threats, altering characteristics and food chains, pollution etc.

Solutions - agricultural forms (vertical indoor farms, high density compact cities = sustainable methods with minimal impacts on biodiversity) or initiatives and schemes e.g. UN REDD

Question 34

How are predictions on the world’s response to increasing Carbon made? Examples/issues?

Answer 34

Modelling: climate and biodiversity

• Different models run with different scenarios and influencing factors e.g. carbon uptake by land surface, NPP increase e.g. IPCC
• Difficulties with biodiversity modelling; too many species, so key indicator species targeted
• Creation of Living Planet Index that measure trends in key marine, terrestrial and freshwater species
• Creation of global maps to show predicted changes e.g. Hoffmann et al. (2010) showing extinction

Question 35

Define the following terms - GPP, NPP, NEP, NBP, Autotroph, Heterotroph

Answer 35

GPP - Gross Primary Productivity (rate at which plants uptake CO2 & produce carbohydrates through photosynthesis = total photosynthetic flux)
NPP - Net Primary Productivity (rate at which plants produce biomass)
NEP - Net Ecosystem Productivity
NBP - Net Biomass Productivity
Autotroph - an organism self-dependent for food (plant)
Heterotroph - cannot fix its own C, eats other food

Question 36

How do you calculate NPP, NEP, NBP and total ecosystem respiration (Rtotal)? What are the units?

Ra = autotrophic respiration
Rh = heterotrophic respiration

Answer 36

NPP = GPP - Ra
Rtotal = Ra + Rh
NEP = GPP - Rtotal
NBP = GPP - Rtotal - disturbance

Mg C ha-1 yr-1 = mega grams of carbon per hectare, per year (where Mg means 10^6)

Question 37

Give 5 ways in which carbon fluxes and biomass are monitored, include brief evaluation of each

Answer 37

1. DBH; Diameter Biomass at breast Height - forests, biomass about 50% C; cheap, easy
2. Harvest method - litter collected in mesh/plastic; a useful LT method and easy, cheap but neglects roots and uncertainty of upscaling
3. Chamber method - w/infra-red gas analysers placed on ground to measure C fluxes, a dark condition measures only respiration, a light open condition allowing photosynthesis; more sophisticated, detailed, different fluxes, but expensive and small-scale
4. Eddy Covariance Towers - automated, sonic anemometer, 3D wind speeds, large areas e.g. FLUXNET
5. Flask sampling - holding breath, walking into wind, the valve is opened e.g. Mauna Loa Co2 curve diagram data; old and outdated, less accurate but useful in areas with no access to high tech scientific equipment (lack of funding/unobtrusive approach required)