Topic 2

Biosphere

the living components of the earth system

Atmosphere

gases e.g. carbon dioxide surrounding earth

Lithosphere

rigid, outermost layer of earth’s rocks and minerals → crust and upper mantle

Hydrosphere

water on earth’s surface, includes clouds and other forms of water

E/MSY

extinction per million species yearly

• Natural background extinction rate (expressed as E) is between 0.1 and 1 for most animals

• Current rate of extinction is 100-1000 E/MSY

• Between 100-1000 times higher than background rate of extinction

BII (biodiversity intactness index)

average abundance of originally present species relative to an intact ecosystem

• BII of 90% means the ecosystem is intact and resilient

• BII of <30% means ecosystem has been depleted and is on the edge of collapse

Light Measurement

tool: Light meter

- Affected by cloud cover and time of day.

- Readings can fluctuate due to shadows and reflections

Temperature measurement

tool: Thermometer (digital or analog)

- Temperature varies with depth and time of day.

- External influences (e.g., human handling) can affect readings.

pH measurement

tool: pH meter or pH test strips

- Calibration required for accuracy.

- Readings can be influenced by temperature and contamination.

wind measurement

tool: Anemometer

- Readings can vary due to obstacles (e.g., buildings, trees).

- Short-term gusts may not represent overall wind patterns.

soil texture measurement

tools: Soil sieving and feel method (hand test)

- Subjective if using hand texture method.

- Sieving requires drying soil samples, which takes time.

slope measurement

tool: clinometer

- Requires careful alignment for accurate measurements.

- Small variations in angle can affect results.

soil moisture measurement

methods: Soil moisture probe or gravimetric method (weighing soil before and after drying)

- Probe accuracy varies with soil type.

- Gravimetric method is time-consuming

Mineral Content measurement

method: Loss on Ignition (LOI) test (heating a soil sample in a furnace to burn off organic matter, leaving mineral content)

- Requires specialized equipment (muffle furnace).

- High temperatures can also cause loss of certain mineral-bound water, affecting accuracy.

Flow Velocity measurement

tool/method: Flow meter or floating object method (timing a floating object over a set distance)

- Readings can be affected by debris and turbulence.

- Floating object method is less precise.

Salinity measurement

tool: Conductivity meter or refractometer

- Conductivity meters require calibration.

- Variations in temperature can affect readings

Dissolved Oxygen measurement

method/ tool: Oxygen probe or Winkler titration method

- Probes need calibration and may give fluctuating readings.

- Winkler method requires careful handling of chemicals.

Wave Action measurement

method: Measure oxygen level in water: high wave action causes high oxygen concentration because water and oxygen mix

- changes in wave strength and tides frequently

- variability must be taken into account

Turbidity measurement

tool: Secchi disk or turbidimeter

- Secchi disk method is subjective and dependent on lighting.

- Turbidimeters require calibration and are expensive.

Binomial classification

• Genus and species names

• Only genus capitalised, comes first

• Written in italics when typed, underlined when handwritten

clades

provide a hierarchical framework for classifying organisms, they group species based on evolutionary history

how does knowing an organism’s clade help?

knowing an organism’s clade can give us clues about its likely characteristics and evolutionary history

ecological niche

the range of conditions and resources in which a species could survive and reproduce

Fundamental niche

full range of conditions and resources in which a species could survive and reproduce

Realised niche

actual conditions and resources in which a species exists due to biotic interactions

Herbivory

• When an animal feeds on a plant

• E.g. : hippopotamus eats vegetation on land & in rivers - reduces the population of the vegetation while increasing hippo population

• Hippos become evolutionarily specialised to eat certain vegetation

Predation

• When an animal eats another animal

• E.g. : lions hunting buffalo; lions kill buffalo, decreasing buffalo population and providing food for lions which in turn allows for increase in lion population

Parasitism

• One species benefits and the other is adversely affected

• Parasites rarely kill their hosts as this is counter-productive

• Host organisms may develop processes to resist or expel parasites, parasites may find ways to overcome these processes

mutualism

• Mutualism (aka symbiosis) is when two organisms live and rely upon each other for mutually beneficial purposes.

• E.g. : clownfish living among anemones; clownfish are protected from predators in anemones’ stinging tentacles in exchange for defence from parasites

Disease

• Caused by pathogens like viruses, bacteria or fungi

• Can spread through populations rapidly and cause illness or death

• E.g. : Chytridiomycosis is caused by a fungus and affects amphibians globally

  • Panamanian Golden Frog is critically endangered because of this disease

  • Mountain Yellow-legged Frog has suffered rapid population decline and is now critically endangered because of disease

Competition

• Interaction between organisms that are trying to attain the same resources

  • Resources could be; food, mates, territory, nesting sites

• Interspecific competition is between different species e.g. green and brown anole in florida

• Intraspecific competition is between individuals of the same species e.g. wolves in a pack feeding on a moose

Carrying capacity

average size of a population determined by competition for limited resources 

Density dependent factors

operate as negative feedback mechanisms regulating the population, leading to stability, become more intense as a population grows denser

• Predator-prey relationships

Density-independent factors

generally abiotic, external and not affected by population size

• Extreme weather events, precipitation

J curve

occurs when:

• Limiting factors are not restricting population growth

• Plentiful resources e.g. light, space, food

• Favourable abiotic components e.g. temperature, rainfall

Quadrats

plastic grid that  you use to count organisms in a given space

• Used for random sampling

• Size should be adjusted to biotic factor you are measuring

• Quadrats should be placed at random

transect

a line that you use to measure coverage over a space; count organisms about a metre to each side of you

• Belt transect w quadrats placed at regular sampling intervals

Population density

total number of a species in all quadrants / area of one quadrat × total number of quadrats

Percentage frequency

 the number of actual occurrences divided by the number of possible occurrences, expressed as a percentage

Abundance/ DAFOR scales

different types of species are put into different categories (e.g. seaweeds or algaes and all organisms in these categories are treated the same), quadrants are used to determine the relative abundance of different organisms

• DAFOR is an acronym representing different levels of abundance; dominant, abundant, frequent, occasional, rare

Lincoln Index/ capture-mark-recapture

indirect way of estimating (not directly counting population)

• Population size= number of animals marked x number of animals in the second group / number of animals recaptured

• Population size= N1 x N2 / M

Homologous structure

anatomical structures that are similar structurally but have different functions

analogous structure

anatomical structures that look different but have similar functions

R strategists

reproduce exponentially

• High fecundity, low survivorship

• Live in unstable, unpredictable environments

• Little investment into each offspring

• Lots of offspring

• Size of offspring: small

• Energy to reproduce: low

• E.g insects, fish, amphibians, most reptiles, rodents, bacteria

K strategists

reproduce near the carrying capacity

• Live in stable, predictable environments

• High investment in offspring

• Few offspring

• Size of offspring: large

• Energy to reproduce: high

• E.g. birds, most mammals, marsupials

fecundity

potential to produce offspring (capability of reproducing)

Survivorship

how long they live

1st law of thermodynamics

• Energy cannot be created or destroyed but it can be transformed

• Modelled by the energy transformations along food chains and energy production systems

• Lost does not mean destroyed, it means lost by the organism

• Relevance of the law to environmental systems: all chemical energy comes from light/ is converted by photosynthesis, no new energy is created/ chemical energy is converted but not destroyed, energy entering producers = energy stored + energy dissipated as heat

2nd law of thermodynamics

• Entropy of a system increases over time

• Energy goes from a concentrated form (sunlight) ito a dispersed form (chemical then ultimately heat energy) 

• Heat is the most dispersed form of energy

• When one animal feeds off another there is a loss of heat energy in the process

• In an isolated system entropy tends to increase spontaneously

• Efficiency of photosynthesis/ conversion of solar to the chemical energy is less than 100%/ often only 10% is passed on/ 90% is lost before next trophic level

Entropy

evenness of energy distribution of measure of disorder

Photosynthesis

Carbon dioxide + water (processed by light energy and chlorophyll ) →  glucose + oxygen

Cellular respiration

Glucose + oxygen → carbon dioxide + water

Gross productivity

total gain in biomass by an organism

Net productivity

amount of biomass left after losses due to cellular respiration

primary productivity

Conversion of light energy into a producer’s biomass in a given amount of time

• NP = GP - R

Secondary productivity

ingested food minus faecal waste

why is the length of food chains limited?

10% or less of the energy is available to the next level – limiting the length of food chains

Biomass

amount of organic matter

Dry mass can be used to approximate biomass

• Measured in g/m^2 or joules/m^2

• Only used for producers

Pyramids of number

• Represent the number of organisms in an ecosystem at each trophic level

• Organised from lowest trophic level at bottom to highest at top

Pyramids of biomass

• The measure of mass of all the organisms at each trophic level in an ecosystem

• Estimated by ecologists at a particular point in time

• Recorded as a the total dry mass x number of organisms for each trophic level

• Units are g/m^2 OR kg/ m^2 OR J(energy)/ m^2

• Following 2nd law of thermodynamics, pyramids tend to grow narrower upwards

Pyramids of productivity

• Bars drawn in proportion the total energy utilized at each trophic level in a given area measured for a standard time

• Each bar will be about 10% of the size of the last bar

• Units: g/m^2/yr OR j/m^2/yr

Ecological efficiency

secondary consumer net productivity/ primary consumer net productivity

bioaccumulation

non-biodegradable toxins build up in one organism over time

biomagnification

the effects of non-biodegradable toxins build through trophic levels

Photosynthetic autotroph

energy from carbon dioxide, processed through photosynthesis that is enabled by the sun

chemosynthetic autotroph

chemicals used to facilitate reaction of chemicals into glucose and byproducts, e.g. some bacteria

heterotroph

obtains energy through ingesting other organisms

productivity

the production of biomass per unit area per unit time

Primary productivity

gain by producers (autotrophs) in energy or biomass per unit area per unit time

• Units: kg carbon/m^2/yr

• Depends on: 

  • amount of sunlight

  • ability of producers to convert energy into biomass

  • The availability of other factors needed for growth e.g. minerals and nutrients 

Secondary productivity

biomass gained in heterotrophic organisms, through feeding and absorption, measured in units of mass or energy per unit area per unit time

Gross primary productivity (GPP)

equivalent to the mass of glucose created by photosynthesis per unit area per unit time in primary producers GPP=NPP+R

Net primary productivity

NPP= GPP - R

• NPP represents the amount of energy converted to new biomass that becomes available to the next trophic level

Gross secondary productivity

the gain in biomass by consumers using carbon compounds that are absorbed and assimilated from ingested food GSP= food eaten - faecal loss

Net secondary productivity

NSP= GSP - R

Ecological efficiency (trophic levels)

The percentage of energy transferred from one trophic level to the next

Ecological efficiency equation

(energy used for growth (new biomass)/ energy supplied)x 100

Energy is lost as heat

through inefficient energy conversions of cellular respiration

Carbon cycle

natural process where carbon moves between different stores and flows

residence time

The length of time that one atom of carbon remains in a specific store

Sequestration

natural capture and storage of CO2 from the atmosphere by physical/ chemical processes

ecosystems can act as stores, sinks and sources

• Young forests are effective, important carbon sinks

• Young forest acts as a sink because they are actively absorbing carbon

• Mature forests act more as stores because their growth rates are slower but they hold the carbon they absorbed in the past

• If deforestation or fires are occurring, forests can be sources of carbon

soils as carbon stores/ sinks

• Wet, colder soil stores carbon better

• Plants cannot have greater storage than soil

Short-term cropping

Growing crops for short periods, such as annual grains, often leads to increased soil erosion and carbon loss

Long-term cropping (e.g., timber production)

Growing perennial crops, such as trees, provides extended cover and reduces soil disturbance, promoting carbon sequestration over a longer period

Physical dissolution

happens when CO2 molecules in the atmosphere dissolve in seawater, forming carbonic acid

Biological uptake

• marine organisms such as phytoplankton and algae use carbon dioxide for photosynthesis, incorporating it into their biomass

ocean as a carbon sink

CO2 dissolved in surface water can be transferred to deep ocean water when cold, dense, surface water sinks → carries CO2 deep into the ocean where they remain for a long time

• Level of CO2 diffusion determines ocean acidity

• Burning of fossil fuels is releasing inorganic carbon at a faster rate than oceans can absorb → ocean acidification

• Ocean acidification affects ability of calcifying organisms to function

Carbon capture through reforestation and artificial sequestration

• The process of capturing carbon and storing it where it will not enter the atmosphere

• Direct air capture: remove carbon from atmosphere with things like chemical solvents that attract carbon dioxide, then this is pumped below the ground to be stored

capture of gas

capture gas at the site it is released and store is underground

lithosphere role in carbon cycle

• Plays a crucial role in the global carbon cycle as it contains carbon stores in fossil fuels and rocks such as limestone (calcium carbonate)

• Carbon stores in the lithosphere can have residence time of millions of years

Methanogenesis

microorganisms (methanogens) convert organic matter into methane gas (CH4)

• Process only occurs in anaerobic environments (no oxygen)

methane characteristics

• Methane has a residence time of ~10 years and then oxidised into CO2

• Methane has a higher warming potential than CO2 ~30x stronger

Organic Nitrogen stores

• Proteins and other nitrogenous compounds found in living organisms and dead organic matter

• These compounds are broken down by decomposers , releasing ammonia and other nitrogenous compounds back into the environment

Inorganic nitrogen stores

• Nitrogen gas in the atmosphere

• Ammonia in soil and water

• Nitrites and nitrates in soil and water

Transformation flows

• Conversion of nitrogen from one form to another

• Nitrogen fixation, nitrification, denitrification, ammonification

Transfer flows

• Movement of nitrogen from one location to another

• Mineral uptake by plants, excretion by animals, consumption and decomposition of organic matter

Nitrogen fixation

• Nitrogen-fixing bacteria convert nitrogen gas from the atmosphere into ammonia

• This process is crucial in making nitrogen accessible because plants cannot directly absorb atmospheric nitrogen

Nitrification

Nitrifying bacteria convert ammonia into nitrites and then nitrates which can be absorbed by plant roots

Denitrification

• Denitrifying bacteria can convert nitrates back into nitrogen gas under anaerobic conditions like in waterlogged conditions

• removes nitrogen from the soil and atmosphere