Ecological pyramids
why do organism need nitrogen
- It is contained within many biological molecules eg Amino acids, Proteins, nucleic acids (DNA, RNA, NAD) NADP, ATP
what are the advantages of pyramid of energy
1. It takes account of the rate of production over a period of time because each block represents energy per unit area / volume per unit time. This is in contrast to pyramid of numbers and biomass, which depicts the standing states of organisms at a particular moment in time. 2.Two species weight for weight may not have the same energy content therefore the biomass is misleading but energy is directly comparable.
what are the processes involved in the nitrogen cycle
1. Nitrogen fixation 2.Nitrification 3. Nitrogen assimilation/Mineralization 4. Ammonification 5. Denitrification
what are the limitations of pyramids of numbers
1. Organisms are treated equally regardless of size. 2. They usually see what we see in an ecosystem, they don't include microorganisms, which are important examples decomposers and parasites. 3. It depends on sampling and estimating numbers. Numbers can be too great to represent accurately. 4. They show numbers at one moment in time, numbers of some species in time. The number of some species change considerably during the year due to reproduction and migration.
what are the limitations of pyramid of numbers
1. The energy value for a given mass of organism is required, which involves complete combustion of a sample. 2.There is still the difficulty of assigning the organisms to a specific trophic level. As well as the organism in the food chains there is the problem of assigning the decomposers and detritivores to a particular trophic level. 3.As with pyramid of numbers and biomass, pyramid of energy suggest that consumers feed on only one trophic level below them. Remember that organisms can feed at several different levels.
what are the limitations of pyramid of biomass
1. They do not indicate how much energy is transferred 2.They depend on sampling and estimating so may not be very accurate 3. Organisms must be killed to measure dry mass. 4. They do not show changes with time, as they are a measure of the standing crop- mass of the organism when samples were taken. as the number of some species change during the year, so does their biomass.
human activities that affect the nitrogen cycle
1. deforestation 2. artificial fertilizers
where can you find inverted pyramids of numbers
1. parasitic food chain (where one organism is host to many parasites: tree-> herbivore bird-> parasites->hyperparasites) 2. detritus food chain (where many organisms feed on one dead plant or animal: detritus->earthworm->birds)
what are the types of ecological pyramids
1. pyramid of numbers 2. pyramid of biomass 3. pyramid of energy
eutrophication
A process by which nutrients, particularly phosphorus and nitrogen, become highly concentrated in a body of water, leading to increased growth of organisms such as algae (algal blooms) or cyanobacteria. thus aquatic organisms become trapped and oxygen will be unable to dissolve in the water, and sunlight will be hindered by the algal blooms, thus plants underneath wont be able to synthesis and die.
rhizobium
A symbiotic bacterium that lives in the nodules on roots of specific legumes and that incorporates nitrogen gas from the air into a form of nitrogen the plant requires while the bacteria gets a home in return (mutualism) Rhizobium forms nodules within the plant roots and supplies ammonia to the plant in exchange for carbohydrates • Ammonia (NH3 ) becomes ammonium (NH4 + ) when mixed with water, and this can be used by plants
NH3
Ammonia (weak base)
NH4+
Ammonium
denitrification
Conversion of nitrates into nitrogen gas It is carried out by denitrifying bacteria (e.g. Pseudomonas denitrificans) in the absence of oxygen (i.e. anoxic conditions) Nitrates can be used instead of oxygen as an electron acceptor during cellular respiration, producing nitrogen gas This will only occur in oxygen-poor conditions (such as waterlogged soils) and reduces the availability of nitrates to plants
dry weight
Dry weight is done by drying plant matter and reweighing to constant mass.
standing crop
Each trophic level has a certain mass of living material at a particular time the amount of biomass present in an ecosystem at a particular time measured as the mass of living organisms (biomass) or the number in a unit area.
ecological succession
Ecological succession is the gradual process by which ecosystems change and develop overtime gradual change in living communities that follows a disturbance
pioneer species
First species to populate an area during primary succession
explain how nitrogen fixation occurs via industrial processes
Haber process in which nitrogen is combined with hydrogen to produce ammonia, NH3; this is then used to manufacture fertilisers such as ammonium nitrate. • This requires a large amount of energy.
inverted pyramid of biomass
Inverted pyramid of biomass exists in aquatic ecosystems. This is possible because of the high turn over rate of phytoplankton. They get rapidly eaten by the primary consumer (zooplankton), so their biomass at any point in time is small. However, they reproduce so fast that despite their low steady-state of biomass, they have high primary productivity to support the large numbers of zooplankton.
explain how nitrogen fixation occurs via lightning
Lightning, which provides very high temperatures that can cause nitrogen and oxygen molecules in the air to combine to form nitrogen oxides; these can then be washed to the ground in rain. When nitrogen oxides mixes with rain water it forms nitrates
NO3-
Nitrate
NO2-
Nitrite
Why is nitrification important?
Nitrites and nitrates are easier for plants to assimilate and hence function as a predominant source of nitrogen for plants It's needed to produce nitrate, a form of nitrogen that marine organisms need in order to grow, and as the amount of available nitrate decreases, smaller species of plankton will gain an advantage over larger ones.
nitrogen fixation
Process of converting nitrogen gas into ammonia by bacteria can be done 3 ways: 1. nitrogen fixing bacteria 2. industrial processes 3. lightning
what percentage of the atmosphere has nitrogen
The air contains about 78% nitrogen gas. However, this is in the form of nitrogen molecules, in which two nitrogen atoms are held together by a very strong triple covalent bond. This is very unreactive. Nitrogen molecules freely diffuse in and out of the bodies of living organisms, but take no part in the metabolic reactions inside their cells.
Sere
The entire sequence of communities that successively change in a given area
Explain primary succession
The species that invade a bare area are called pioneer species. Rocks usually lichens secrete acids to dissolve rockm helping in weathering and soil formation later on small plants like bryophytes, hold in small amount of soil. as the plants get bigger it becomes "stable climax" forest community. this remains stabel as long as the environment remains unchanged 1. originally hostile "only pioneer species live here" 2. pioneer species die "increase organic conent of soil eg: mineral, humus" 3. gradually environment changes and becomes less hostile 4. more nutrient present 5. other species now grow, with more habitat present 6. climax community eventually reach "usually oak trees"
nitrogen cycle
The transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere
pyramid of biomass
This pyramid represents the total amount of biomass of the organisms present at each trophic level. The biomass is expressed in terms of fresh or dry weight. A pyramid that illustrates the total mass of all the organisms in a trophic level. For most ecosystems, the pyramid of biomass is upright, where the biomass decreases with each trophic level.
ecological pyramid
a graphical representation of the relationship between the different living organisms at different trophic levels Pyramids consist of horizontally arranged blocks, with each block representing a trophic level. It can be observed that these pyramids are in the shape of actual pyramids with the base being the broadest, which is covered by the lowest trophic level, i.e., producers. The next level is occupied by the next trophic level, i.e., the primary consumers and so on 1. pyramid of numbers 2. pyramid of biomass 3. pyramid of energy
succession
a process that starts where no living organisms are there The series of predictable changes that occur in a community over time
causes of deforestation to the nitrogen cycle
because roots anchor nutrients (nitrogen and phosphorus) in the soil, once the tress are cut, the nutrients runoff into rivers and into the ocean causing eutrophication. .more rain hits soil .more leaching .soil is water logged allowing denitrifying bacteria to work .NO2 falls
biomass
dead weight- the total mass of organisms in a given area or volume. measured in g/m2
Ammonification
decomposers convert organic waste into ammonia Saprobiotic microorganisms feed on these materials releasing ammonia in the form of ammonium ions in the soil. As a plant or animal decays, saprotrophs will decompose organic materials to produce ammonia (and ammonium ions) This process is known as ammonification and releases ammonium ions into the soil which can be absorbed by plants
what are the advantages of pyramid of numbers
easy method of giving an overview and is good for comparing changes in population numbers over different times or seasons
azotobacter
free living nitrogen fixing bacteria in soil
pyramids of numbers
graphically display the numbers of organisms at each trophic level in a food chain the unit is numbers per unit area usually upright except for some situations like that of the detritus food chain (detritus->earthworm->birds), where many organisms feed on one dead plant or animal. hence they can be upright, inverted, depending on the ecosystem. Inverted pyramid of numbers can be seen when an organism size is not considered. Inverted pyramids are also displayed in a parasitic food chain, where one organism is host to many parasites
Nitrosomonas
nitrifying bacteria that convert ammonia into nitrite (NH3 to NO2-)
nitrobacter
nitrifying bacteria that converts nitrite to nitrate (NO2- to NO3-)
assimilation
process by which plants and animals incorporate the NO3- and ammonia formed through nitrogen fixation and nitrification. Plants take up these forms of nitrogen through their roots, and incorporate them into plant proteins and nucleic acids. Animals are then able to utilize nitrogen from the plant tissues
pyramid of energy
represents the flow of energy from the producers to the final consumers. Pyramid of energy is the only type of ecological pyramid, which is always upright as the energy flow in a food chain is always unidirectional. Also, with every increasing trophic level, some energy is lost into the environment. measured in: J m^-2 yr^-1 or KJ m^-2 yr^-1
seral stages / seral communities
sequential phases of change during succession The individual transitional communities
stable climax
the ¨final¨ mature community and predominant species make up the stable climax
explain how nitrogen fixation occurs via nitrogen fixing bacteria
there are two types of bacterias: azotobacter (soil), rhizobium (plant nodules) Nitrogen-fixing bacteria, which use the enzyme nitrogenase to combine nitrogen and hydrogen to produce ammonium ions.
nitrification
two-step process ammonia (NH3) is converted to nitrate ions (NO3)- Nitrifying bacteria oxidise ammonium ions into nitrite ions which are further oxidised to nitrate ions. 1. nitrosomonas: ammonium ions (NH4+) into nitrites (NO2-) 2. nitrobacter: nitrites (NO2-) into nitrates (NO3-) These reactions require oxygen and hence soil must be well aerated to ensure a rich supply of nitrites and nitrates
climax community
ultimate stable community that is in equilibrium with the abiotic conditions
how does artificial fertilizers affect the nitrogen cycle
when artificial fertilizers containing nitrogen and phosphorus are used in agriculture, the excess fertilizer may be washed into lakes, streams, and rivers by surface runoff. • A major effect from fertilizer runoff is saltwater and freshwater eutrophication.
distorted pyramid of numbers
when problems arise with parasites-numerous parasites on one hos- resulting in a distorted pyramid a pyramid skewed by large numbers of parasites as consumers
secondary succession
when succession starts again in an area where communities have been destroyed, it occurs more quickly eg: abandoned farm lands, burned or cut forests, lands that have been flooded. Since some soil or sediment is present, succession is faster than primary succession.
primary succession
when successions starts from bare, previously uncolonized group or water with no life eg:newly cooled lava, bare rock, newly created pond or reservoir.
