Ecosystems

• Net primary production = Gross primary production - Respiration
• Net primary production of consumers = Food ingested - Respiration - Energy lost as faeces
• Net productivity in plants can be represented as uptake of carbon dioxide as it represents the intake of CO2 for photosynthesis minus the CO2 released in respiration
• An ecosystem is a balanced, self sustaining area of interacting biotic and abiotic factors
• A habitat is an area where an organism lives containing biotic and abiotic features
• An abiotic factor is a non living factor
• A biotic factor is a living factor
• A niche is the role of a species in an ecosystem, no two species can occupy the same niche as one will out compete the other
• Plants are autotrophic, meaning they produce their own energy source from sunlight
• Energy is transferred through trophic levels, from producers to primary consumers such as herbivores, then to secondary consumers
• Energy is lost between trophic levels in the food chain, this is due to loss of energy in excretion, undigestible parts such as bones and hair, and respiration
• Saprobionts are bacteria and fungi which digest food externally by releasing enzymes before absorbing the products, this is decomposition
• Detritivores consume organic debris from plants and animals
• Biomass is the total mass of living material in an area in a given time
• Dry biomass is the mass of dried living material, this produces a small sample which is less representative of a population and involves death of the organism
• Biomass can be measured as grams per square meter or grams per cubic meter in aquatic environments
• A bomb calorimeter is where a sample of dry mass is burned in pure oxygen in an insulated, sealed chamber, the chamber is surrounded by water, its rise in temperature can be used to calculate energy release
• The equation for specific heat capacity is Energy = Change in temperature x mass x specific heat capacity
• The specific heat capacity of a substance is the amount of energy needed to raise 1 gram by 1 degree celsius
• Photosynthetic efficiency = Light incorporated into biomass / Light falling onto plant
• Photosynthetic efficiency is often low due to light being reflected by clouds and the waxy cuticle, not all wavelengths are absorbed, not all light hits a chlorophyll molecule and not all is incorporated due to limiting factors
• Net primary productivity is the amount of biomass available for the next trophic level as well as growth and reproduction
• Efficiency = Energy available after transfer / Energy available before transfer
• Organism mass and energy available decreases at higher trophic levels due to inefficiency
• Intensive farming can be done by growing crops by hydroponics - growing plants in water instead of soil and supplying all needed nutrients as dissolved ions
• Intensive farming can be done by growing crops in glasshouses, allowing control of temperature, humidity, CO2 concentration and light available
• Intensive farming can be done by battery farming and fish farming which has ethical issues
• Growing crops is more efficient land use than animals as there is one less stage in the food chain so less resources are necessary
• Battery farming has animals in small areas to reduce movement, high temperatures to reduce energy needed to maintain body temperature and a diet with the exact amount of nutrients necessary to reduce waste
• Battery farming's downsides include bad quality of life and rapid spread of disease, mass levels of animals on antibiotics increases chances of antibiotic resistance reaching food