GEOG20009 Lecture Notes - Lecture 10: Carrying Capacity, Chemosynthesis, Chlorophyll
15 May 2018
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LECTURE 10: COMMUNITIES, BIOMES, ECOSYSTEMS
• Conditions that support life:
o Liquid medium (water) – environment where chemical reactions take place)
o Matter (atoms – O, C, H) – for chemical reactions
o Energy Source (sun) – fuelling chemical reactions
▪ Energy exists in many forms: heat, light, chemical, electrical
▪ Energy is the ability to bring about change or to do work
Primary Production
• Primary Production: synthesis of organic compounds (new organic matter) from atmospheric or
aqueous carbon dioxide
• Mostly occurs through photosynthesis
• Not all incoming energy can be converted, only small range which is useful for plants (only
1% of solar energy striking producers is captured by photosynthesis)
• Gross Primary Production (GPP) v Net Primary Production (NPP)
o GPP: all primary production, all new organic matter made
o NPP: GPP – respiration = NPP, amount of carbon uptake after respiration
ENERGY IN COMMUNITIES
2 characteristics of species which are dependent on energy concept, and strongly influence their
effects on community organisation
Trophic Status
• Organisms responsible for primary production are
known as primary producers or autotrophs (self-
feed)
• Energy left over from maintenance & respiration
goes into production (growth)
• Everything above autotrophs consumes them, and
rely on them for energy
• Important to remember decomposers (also heterotrophs) – break down all waste to its basic
mineral components so the cycle can continue
• When primary production > consumption & decomposition = build-up of biomass (peat) –
stored energy
Production Efficiency
• Consumers vary in efficiency of
production
• Efficiencies that describe
resource utilisation
• Determined by metabolism
• Metabolism: processes that the
body needs to function
Body Size
• The larger an organism, the
more energy it requires (for
maintenance, growth,
reproduction etc.)
• Metabolic rate per unit of mass greater in small organisms – mouse has higher metabolic rate than elephant
• Metabolic rate: rate of energy uptake & expenditure
• Storage Capacity: increase in direct proportions to body mass – larger animals can store more energy, endure
longer
• Capacity to withstand prolonged stresses (endurance)
Body Size and Geographic Range
• Influences the spatial scale at which organisms use the environment
• Small Organisms: less resources required per individual, can use smaller areas & be more
specialised (high carrying capacity)
• Large Organisms: lower numbers and broad geographic ranges, low carrying capacity
Topics
• Energy considerations
– life & organisations
of communities
• Productivity concept
• Regional to global
scales of
communities
Chemosynthesis: oxidation or
reduction of inorganic
chemical compounds – life at
geothermal vents
Photosynthesis: changes
sunlight into chemical energy,
splits water to liberate
oxygen and fixes carbon
dioxide into sugar
A: sunlight absorbed by
chlorophyll in leaf
B: carbon dioxide is taken in
from air
C: water is transported from
the roots
D: glucose is synthesised &
distributed throughout plant
E: oxygen is released
Trophic Status & Energy Transfer
• Organisms use energy stored in organic
molecules to perform the work of moving,
growing and reproducing (by oxidising and
producing heat)
• Conversion of assimilated energy is secondary
production
• Primary production limits secondary production
Carrying Capacity:
maximum number of
individuals an ecosystem
can support
Document Summary
Liquid medium (water) environment where chemical reactions take place: matter (atoms o, c, h) for chemical reactions, energy source (sun) fuelling chemical reactions. Energy exists in many forms: heat, light, chemical, electrical. Energy is the ability to bring about change or to do work. Primary production: synthesis of organic compounds (new organic matter) from atmospheric or aqueous carbon dioxide. Productivity concept: regional to global scales of communities, mostly occurs through photosynthesis, not all incoming energy can be converted, only small range which is useful for plants (only. 2 characteristics of species which are dependent on energy concept, and strongly influence their effects on community organisation. Trophic status: organisms responsible for primary production are known as primary producers or autotrophs (self- feed) Energy left over from maintenance & respiration goes into production (growth) Everything above autotrophs consumes them, and rely on them for energy.
