C.6 Biology
Assimilated:
(of the body or any biological system) absorb and digest (food or nutrients)
Outline the process of nitrogen fixation by a named free-living bacterium
-There is nitrogen gas in the atmosphere (78 percent) but it is an inert gas -It is converted to ammonia by azotobacter.
Commercial fertilizers are often applied to agricultural land. Discuss the use of fertilizers on crops and their effect on other ecosystems. [6 marks]-add more
-adding fertilizer increases nitrogen/phosphate in soil/nutrient cycles -adding fertilizer increases crop yield -commercial fertilizers may not stay in ground as long as organic fertilizers/manure. -commercial fertilizers release compounds more rapidly than organic fertilizers /manure. -nutrients run off/leached from land into water/groundwater/lakes/streams -high concentrations of nitrogen/phosphate in water causes eutrophication -high concentrations of nitrogen/phosphate causes algae to multiply rapidly or leads to algal bloom -algae die and decomposed by bacteria -decomposers require oxygen from water -if oxygen levels drop too low fish/aquatic organisms die.
Waterlogging visual
-certain soils love water, other soils water go through it. -much rain-> waterlogged soil(no minerals in top soil) -> minerals leached from surface A primary consequence of waterlogging is the reduction in nitrogen availability within the soil This means that plants are unable to access sufficient quantities of nitrogen from the soil via their roots
two sources of the ammonium in the forest soil apart from deposition in rainfall.
-decomposition from plants/animals. -urine/feces/other nitrogenous waste -activity of soil microorganisms/ammonification/nitrogen fixation -fertilizers (on edge of forest)
Phosphorus characteristics
-does not include a gaseous component (it does not involve the atmosphere). -this means the rate of turnover is much lower than the other cycles (it is released slowly through weathering) -This also means the rate of replenishment is extremely slow (phosphates removed from the soil are not quickly replaced)
Outline how the plants absorb the nitrogen contained in the insects and other animals
-enzymes in the decomposition
The percentage of phosphorus in an ecosystem that is recycled per year is in most cases very small, and far smaller than the percentage of nitrogen that is recycled. Suggest reasons for this difference.
-largest store of phosphorus (in ecosystems) is in marine sediments and minerals/phosphate rock while nitrogen is in the atmosphere. -main source of release of phosphorus is by weathering of rocks (very slow process/nitrogen is by bacterial action) -high concentrations of nitrogen/low concentration of phosphorus compounds in living organisms. -phosphorus is not a very soluble mineral
Suggest factors that could account for the growth curve of the M. gallopavo population.
-natality and mortality -immigration and emmigration -resources/abiotic conditions/carrying capacity -predation/hunting
In depth explanation of nitrogen cycle (add more-on separate loose-leaf paper)
-nitrogen gas (78 percent in atmosphere but it is inert-very stable, plants are unable to break the bonds) -> ammonium/ammonia
Explain how human activities could affect the phosphorus cycle
-phosphorus in rock (reserves) enters slowly into the biosphere by weathering -mining of phosphorus rocks accelerates the natural cycle/faster than natural erosion. -(phosphorus products) transported to agricultural areas (all over the world) -with use of fertilizers phosphorus makes its way into the soil. -run-off/drainage from farms causes phosphorus to move into aquatic ecosystems -use of detergents adds phosphorus to water -release of sewage adds phosphorus to water -excess phosphate can lead to over growth of algae and plants in water -eutrophication can kill fish and other plants -phosphorus removed from ecosystem by the harvesting of agricultural crops
The predominant source of phosphorus is rock containing phosphate (phosphate rock). The graph below shows the world production between 1900 and 2009. Some scientists estimate that available phosphorus reserves in the Earth will be completely depleted within approximately 100 years. Discuss the implications of these estimates.
-production of fertilizers will decrease/price of fertilizers will rise -less food production/increase in cost of foods -development of alternative methods of agriculture -phosphate needed by living organisms for nucleic acids/ATP so lack will affect growth negatively.
Soil lab
-water holding capacity of the soil (retention rate). Take soil, put in funnel, take some water, use timer for five minutes, pour water into soil/sand, look how much water goes through and how fast, when it stops dripping stop, use pyramid, -
waterlogged soil
-waterlogged soil with lose nitrates and nitrites via the process of dentrification. -waterlogging reduces oxygen availability in the soil, creating oxygen-poor conditions favored by denitrifying bacteria. -this bacteria (pseudomonas) will convert available stocks of nitrates into nitrogen gas, reducing soil nitrogen content
Why do we need phosphorus?
1) synthesis nucleic acids, membranes (phospholipids) and ATP (sugar phosphate backbone to DNA-> replace cells, 2) Phosphates are returned to the soil upon the decomposition of plant and animal remains (very slow) use: make fertilizer but when run off happens, hot -> algae bloom.
Nitrogen Cycle(hint)
Count your vowels to help distinguish between each nitrogen compounds. Ammonium (4 different vowels ) NH4+ Nitrites (2 different vowels) NO2- Nitrates (3 different vowels) NO3- (2 comes before 3, so nitrites are converted to nitrates) explaining diagram: -(different options) -first step: fix inert gas into usable. Take nitrogen gas that is very stable and fix it using bacteria to make it usable as an ion (ammonium). Then, nitrification. Then, nitrities into nitrates by adding oxygen. -two types of bacteria. -
Predictions for the future
Current estimates predict that the availability of phosphates may become severely restricted within 50 - 100 years This would greatly limit the crop yield per unit of farmland due to the reduced use of phosphate-based fertilisers There are currently no synthetic ways of creating phosphate-based fertiliser (although this could change in the future)
Eutrophication
Eutrophication is the enrichment of an ecosystem (typically aquatic) with chemical nutrients (nitrates, phosphates, etc.) The nutrients can be introduced via leaching from soil by rainfall or released as part of sewage Eutrophication is common around agricultural lands where the use of artificial fertilisers are prevalent An increase in nutrient supply within waterways will result in several ecological consequences: A rapid growth in algal populations will occur (algal blooms) as a result of the increased availability of nutrients As the algae die, there will be a subsequent spike in the numbers of saprotrophic microbes (decomposers)
Insectivorous plants
Insectivorous plants are able to obtain nitrogen in low-nutrient environments by feeding on invertebrates Insectivorous plants include the Venus fly trap, which is native to subtropical wetlands that have waterlogged soil The plant's terminal leaves form a trapping structure that is baited by nectar to attract insects When trapping has occurred, the plant releases digestive enzymes that allow it to absorb nutrients from the insect Insectivorous plants only obtain nitrogen from feeding on insects - they still derive energy from photosynthesis
Two bacterias involved in nitrification
Nitrites and nitrates are easier for plants to assimilate and hence function as a predominant source of nitrogen for plants (Nitrobacter and nitrosomonas).
soil testing
Soil testing kits can be used to identify the amounts of the different components of soil, including: Nutrients - chemical reagents produce colour changes when testing for nitrogen (N), phosphorus (P) or potassium (K) Soil pH - colour changes can be used to identify the acidity or alkalinity of a soil sample
kits for testing
Soil testing kits can be used to identify the amounts of the different components of soil, including: Texture - soil can be separated into layers according to particle size (different particles retain nutrients with varying efficacy Porosity - Water Holding Capacity Permeability - rate at which flows through the soil
Haber Process
The Haber process is an artificial nitrogen fixation process developed by Fritz Haber and Carl Bosch in 1910 It is currently the main industrial procedure for the production of ammonia The Haber process involves the conversion of nitrogen and hydrogen gas into ammonia using a metal catalyst: Gases are passed over four beds of catalyst at high temperatures and high pressures Between each pass the mixture is cooled and any unreacted gases are recycled Each pass is only ~15% efficient, however recycling allows for a conversion rate of ~97%
Haber process (more)
The Haber process is used to make nitrogen-based fertilisers which can be used for agricultural purposes Currently, there is no comparable process for the artificial synthesis of phosphate-based fertilisers
Soil Content
The bulk of soil is made up of a mixture of organic matter, rock and mineral particles The relative proportion of all these components, along with pH, determines soil type (e.g. sand, clay, loam, silt, etc.) Gardeners and farmers require this information in order to determine the viability of the soil for planting purposes Identified issues may require adjustments to the types of crops planted or types of fertilisers employed
Non-renewable resource
The demand for fertiliser in agriculture is very high, however the rate of turnover in the phosphorus cycle is very low This means that phosphates are being removed from the lithosphere at a much faster rate than they are being replenished Consequently, phosphate minerals are classified as a non-renewable resource
eutro
The high rate of decomposition will result in an increased biochemical oxygen demand (BOD) by saprotrophic bacteria The saprotrophs will consume available quantities of dissolved oxygen, leading to deoxygenation of the water supply Eutrophication will also increase the turbidity of the water, which will reduce oxygen production by photosynthetic seaweeds This will stress the survival of marine organisms, potentially leading to a reduction in biodiversity within the ecosystem
Sulfur Cycle
The sulphur cycle outlines how different forms of sulphur are cycled within the environment Sulphur is an essential component of living organisms, being a constituent part of many proteins and enzyme cofactors Sulphur in the air and soil may be oxidised to form sulphates (SO42-) Sulphates are reduced by plants and bacteria and hence sulphur becomes incorporated into organic molecules Sulphur within the soil can also be mineralised into inorganic forms and incorporated with metals (e.g. iron sulphide) Burning of fossil fuels releases sulphur as sulphur dioxide (SO2), which is an enabling component of acid rain
ammonification
ammonia can also be produced from organic sources of nitrogen (e.g.) amino acids when broken down by decomposers 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
Chemoautorophic:
an organism, typically a bacterium, which derives energy from the oxidation of inorganic compounds.
Dentrification
chemical reaction process that converts nitrates (NO3-) into nitrogen gas (N2). -it is carried out by denitrifying bacteria (e.g.) Pseudomonas denitrificans) in the absence of oxygen (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.
Phosphorus availability (part 2)
he fertilisers are then transported to crops in order to increase their productivity by increasing plant access to phosphate When the crops are harvested, the phosphates that comprise part of the plant's biomass are lost from the phosphorus cycle While the application of fertiliser adds phosphorus at one site, it causes the depletion of phosphorus reserves at another site The continued production of phosphate-based fertilisers is depleting global phosphorus reserves at a rapid rate
Explain the factors that can contribute to the exponential growth phase in a sigmoid population curve. [ 3 marks]
ideal environmental/unlimited resources/below carrying capacity -little disease/predators -high natality/birth rate and immigration (both needed) -natality and immigration greater than mortality and emigration.
Azotobacter
is found living freely in the soil, while Rhizobium forms a mutualistic association with the roots of legumes. Rhizobia are the type of bacteria that live in the roots of legumes and fix nitrogen. In return for the nitrogen, the rhizobia get carbohydrates from the plants. Both receive benefits from this relationship. (plants and bacteria)
Suggest one possible cause for the decrease of the number of animals after 1940.
lack of food, disease, hunting, increase of predators
State two bottom-up factors affecting algal blooms.
minerals, nutrients, phosphorus, nitrogen
forms of nitrogen that plants can use (assimilate)
nitrates(NO3-) and ammonium (NO2-)
Phosphorus availability
phosphates can be removed from the lithosphere via mining and converted into phosphate-based fertilisers This allows phosphates that would otherwise remain inaccessible in buried rocks to become available for plant use
Hunting of M. gallopavo is currently regulated. Predict what would happen if the hunting regulations were removed.
population would decrease/may become extinct, open realized niche for other organisms. food web may change, less intraspecific competition.
biogeochemical
relating to or denoting the cycle in which chemical elements and simple substances are transferred between living systems and the environment.
phosphorus cycle
shows how different forms of phosphorus are transitioned within the environment -certain rocks contain high levels of phosphate, which can be released into the soil and water via chemical weathering (water combines with ions with phosphate and pull it out).
Nitrogen Cycle
the biogeochemical cycle by which nitrogen is converted into various chemical forms -while about 78 percent of the atmosphere is composed of nitrogen (n2), this gas is inert and unable to be used by plants and animals. -chemoautrophic bacteria can convert this nitrogen gas into compounds that can be assimilated by plants and animals.
nitrification
the converstion of ammonium ions into nitrites (NO2-) and nitrates (NO3-) by nitrifying bacteria in the soil -nitrosomonas converts ammonium ions into nitrities while Nitrobacter can convert the nitrites into nitrates. (oxygen is needed for these bacteria to work).
nitrogen fixation
the first stage of the nitrogen cycle is the conversion of inert nitrogen gas (n2) into ammonia (NH3). This reaction is catalysed by the enzyme nitrogenase, which is produced by nitrogen-fixing bacteria in the soil Azotobacter is found living freely in the soil, while Rhizobium forms a mutualistic association with the roots of legumes
Explain how top-down factors control algal blooms.
the herbivores regulate algae bloom -predators of the herbivores help regulate algae bloom/reduce herbivore abundance -overfishing/death of predators/decreased reproduction of predators decreases algal bloom as herbivore population increases -habitat degradation can decrease algal bloom -pathogens of algae will decrease algal bloom
Explain why plants not considered carnivorous
they also photosynthesize
Example of insectivorous plants
venus fly trap
leaching
waterlogged soil will also lose nitrates and nitrites via the process of leaching. -whenever rainfall exceeds evaporation, there will be a buildup of water within the porous soil. -as this water drains downward through the soil, soluble minerals (like nitrates and nitrites) are removed with it. -continual leaching impoverishes the upper layers of soil and concentrates dissolved minerals in the lower bedrock. -leaching is most common in highly porous soils (sandy soils) and least common in textured soils (such as clay).
waterlogging
waterlogging occurs when the soil becomes inundated with water, either through flooding or irrigation with poor drainage. -waterlogging impacts the nitrogen cycle by reducing the levels of nitrates and nitrites in the soil. (water laying on top of the soil-> bad drainage)
