B13. Energy and Ecosystems (FINSIHED) Flashcards
What are producers?
Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions
What are consumers?
Organisms that obtain their energy by consuming other organisms rather than energy of sunlight directly
What are the types of consumers and what do they indicate?
Primary consumers, first in chain of consumers, feed off producers; Secondary consumers, consume primary consumers; tertiary consumers - consume secondary consumers, top of the chain
What are saprobionts?
Decomposers, group of organisms that break down the complex material in dead organisms into simple ones.
What is a food chain?
Describes a feeding relationship in which organisms are consumed in this order; Producers > primary consumers > secondary consumers > tertiary consumers
What is a torphic level?
Stage of the food chain eg. producer, primary consume
How is direction of energy flow represented in a food chain?
Arrow shows directional energy flow
What are food webs and why are they produced?
Food chains will be linked together forming a food web due to animals not relying on a single food source within a single habitat
What is biomass?
Total mass of living material in a specific area at a given time
What procedure is necessary to produce reliable biomass results and why?
Biomass is measured using dry mass per given area due to presence of varying amounts of water
How is energy of biomass estimated?
Calorimetry; Bomb calorimetry, sample of dry material is weighed and is then burnt in pure oxygen within a bomb; Bomb surrounded by water bath and the heat of combustion causes a temp rise in water
What is the source of energy for ecosystems?
The Sun
How efficient is energy absorption of the Sun’s energy?
1% - 3%;
What happens to the majority of the Sun’s energy?
Over 90% is reflected back by clouds and dust or absorbed by atmosphere; Not all wavelengths of light can be absorbed by photosynthesis; Limiting factors ie. low CO2 levels limit photosynthesis
What is gross primary production?
Total quantity of chemical energy stored in plant biomass in a given area or volume
What is net primary productivity?
Energy store from gross primary production left after factoring plants 20% - 50% net losses to respiration
What’s the equation for net primary production?
Net primary production = Gross primary production - respiratory losses
Why is less energy available in the upper trophic levels?
Some organisms aren’t consumed; Some parts are consumed but cannot be digested and are lost in faeces; Some of the energy is lost in excretory materials; Some energy lost as heat from respiration
Why is less energy available in mammals and birds?
High energy use due to high body temperature; More energy needed to maintain their body temperature when heat is constantly being lost to the environment
What is the equation for net production of consumers?
Net production = Chemical energy store of ingested food - ( Energy lost in faeces and urine + Energy lost in respiration)
What observations can be made while climbing the trophic levels?
Only 4 - 5 trophic levels due to insufficient energy to support; Total biomass decreases; Total amount of energy available decreases
How is energy conserved of livestock in farming?
Movement restricted, less energy used in muscle contractions; Environment kept warmer, less heat loss; Feeding controlled to optimum amount; Predators are excluded
How does energy flow in an ecosystem and is this a problem?
Energy enters ecosystem as sunlight is lost as heat; Heat cannot be recycled; Linear unidirectional flow; Not a problem as the Sun supplies the energy
What is the simple sequence all nutrient cycles follow?
Nutrient taken up by producers as simple inorganic molecules; Producer incorporates nutrients into complex organic molecules; Producer eaten, nutrient pases into consumer; Passes along food chain; When producers and consumers die their complex molecules are broken down by saprobiontic microorganisms that release the nutrient in its original simple form.
What are the main stages of the nitrogen cycle?
Ammonification, nitrification, nitrogen fixation, denitrification
What occurs in ammonification?
Production of ammonia from organic nitrogenous compounds, urea, proteins, nucleic acids, vitamins. Saprobiotic microorganisms, fungi, bacteria, feed on faeces & dead organisms materials releasing ammonia; Forms ammonia ions in soil
What occurs in nitrification?
Nitrifying bacteria oxidises ammonium ions to nitrite ions; nitrite ions oxidised to nitrate ions
What conditions needed for nitrification?
Nitrifying bacteria require oxygen - Soil with many air spaces
What occurs in nitrogen fixation and when does it occur naturally?
Nitrogen gas is converted into nitrogenous compounds; Naturally when lightning passes through the atmosphere
What are the two main microorganisms that carry out nitrogen fixation?
Free living nitrogen fixing bacteria; Mutualistic nitrogen fixing bacteria, found in nodules on the roots of plants such as peas and beans
What do free living nitrogen fixing bacteria do?
Bacteria reduce gaseous nitrogen to ammonia, using it to produce amino acids; Nitrogen rich compounds are released when they die and decay
What occurs in denitrification?
Anaerobic denitrifying bacteria use nitrates in soil during respiration; Producing nitrogen gas
What are the conditions for denitrification?
Soils that has low oxygen concentration ie. become waterlogged;
Why does denitrification negatively affect crop productivity and how is it counteracted?
Reduces availability of nitrogenous compounds for plants; Soil must be well aerated to prevent build up of denitrifying bacteria, plough field
Explain the phosphorus cycle.
Phosphorus exists as phosphate ions in the form of sedimentary rock deposits; Weather and erosion dissolves phosphate ions; Absorbed by plants into biomass; Consumed by consumers, excess phosphate excreted; On death of plants and animals decomposers and fungi break down releasing phosphate ions into water and soil; Phosphate ions in excreta released by decomposition and dissolved out of rocks; Transported by streams and rivers into lakes and oceans where they form sedimentary rocks;
What is the role of mycorrhiza in nutrient cycle?
Improving the uptake of relatively scarce ions such as phosphate ions
What type of relation does mycorrhizal and plants , fungi have?
Mutualistic; Plant benefits from improved water and inorganic ion uptake and fungus receives organic compounds ie sugars and amino acids from plant
What does natural organic fertiliser contain?
Dead and decaying remains of plants and animals, animal wastes ie. manure, slurry and bone meal
What does artificial inorganic fertiliser contain?
Mined from rocks and deposits, then converted into different forms and blended together to give appropriate balance of minerals; Always contains Nitrogen, Phosphorus and Potassium
What fertiliser causes the greatest long term increase in productivity?
Combination of natural and artificial fertilisers. Vital that minerals are added in appropriate quantities
What are the effects of nitrogen containing fertilisers?
Increases growth, area of leaves, rate of photosynthesis, improves crop productivity; Reduced species diversity, Nitrogen rich soils favours growth; Leaching; Eutrophication
What occurs in leaching?
Nutrients are removed from the soil; Rainwater dissolves soluble nutrients ie. Nitrate ions, carrying them deep into soil, eventually beyond the reach of plant roots
What are the negative effects of leaching?
Leached nitrate ions find their way into watercourses ie. streams and rivers; Harmful effect on humans if its drinking water source; Causes eutrophication
What is eutrophication?
Process by which nutrient concentrations increase in bodies of water
What happens during eutrophication?
Lakes and rivers have low conc of nitrate ions, nitrate ions are limiting factor for plant and algal growth; Nitrate ion conc increases due to leaching; Algae grow at surface, upper layer of water becomes densely populated with algae, algal bloom; Algal bloom absorbs light; Light becomes limiting factor for plants at lower depths, plants die; Lack of dead plants and algae is no longer limiting factor for saprobiontic bacteria; Increased oxygen demand due to saprobiontic bacteria; O2 conc in H2O reduced and nitrates are released from decaying organism; O2 becomes limiting factor for aerobic organisms, death; Less competition for anaerobic organism; Anaerobic organism decompose dead material releasing more nitrates and toxic waste ie hydrogen sulphide, water is putrid
