5B nutrients and cell cycles

• What does dry biomass show?

  chemical energy store in an organism
• how do measure the chemical energy of an organism?

  calorimetery of biomass
• What are plants position in ecosystems?

  In any ecosystem, plants are the producers in a food web as they are able to produce their own

  carbohydrates using carbon dioxide in the atmosphere or water.
• what happens between tropic levels

  Between each trophic level in a food web the majority of the energy is lost due to respiration and excretion. The remaining energy is used to form the biomass.
• how do we measure biomass

  The amount of biomass remaining in an organisms can be measured in terms of mass of carbon or dry mass of tissue per given area.
• What does productivity of an ecosystem depend on?

  How productive an ecosystem is depends on the abiotic and biotic factors. Plenty of water, light, warmth and green plants will maximise the rates of photosynthesis and therefore result in more carbohydrates being produced in the plants.
• what ways can we quantify the productivity of an ecosystem

  NPP and GPP
• what is npp

  Net primary production (PP) is the chemical energy store in plant biomass taking into account the energy that will be lost due to respiration (R).
• what is GPP

  Gross primary production (GPP) is the chemical energy store in plant biomass, in a given area or volume. It is the total energy resulting from photosynthesis.
• what is the equation to work out NPP

  NPP = GPP - energy lost through respiration
• what is the equation to work out the net production of consumers

  N= I - F+ R

  N = net production of consumers

  I = the chemical energy store in ingested food

  F = the chemical energy lost to the environment in faces and urine

  R = respiratory losses.
• what do we measure rate of productivity in?

  KJ ha-1 year-1 (KJ per unit area per year)
• why do we measure rate of productivity per area?

  it is recorded as per unit area to standardize the results to enable environments to be compared- it takes into account that different environments will vary in size.
• why do we measure rate of productivity per year?

  The units are also per year to take into account the impact seasons will have on rain, light and heat - it provides an annual average to allow fair comparisons between environments.
• what is the importance of the nitrogen cycle

  The air is 78% nitrogen, however plants and animals cannot obtain nitrogen through gas, exchange as Nitrogen gas (Nz) contains a triple bond.

  
  

  Microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb.

  we use nitrogen to makeup biological molecules such as Proteins, ATP and nucleic acids which are necessary for growth development and therefore survival

  
  

  nitrogen is also finite so must be recycled
• what are the 5 stages of the nitrogen cycle

  1. Saprobiotic nutrition and microbes
  2. Ammonification
  3. Nitrification
  4. Nitrogen fixation
  5. Denitrification
• What are mycorrhizae

  fungal associations between plant roots and beneficial fungi
• why are mycorrhizae are beneficial for plant growth?

  The fungi increase the surface area for water and mineral absorption

  The mycorrhizae acts like a sponge so holds water and minerals around the roots.

  This makes plants more drought resistant and able to take up more inorganic ions.

  Their part in the nutrient cycles is therefore improving the uptake of relatively scarce ions, such as phosphate ions.

  This is a mutualistic relationship.
• what are fertilisers

  Fertilisers are added to soil to replace the nitrate and phosphates ions lost when plants are harvested and removed from nutrient cycles as crops.
• what are the two types of fertilisers

  • natural (manure)
  • artificial (inorganic chemicals).
• evaluate natural fertilisers

  Natural fertilisers are cheaper, and often free if the farmer owns animals.

  However, the exact minerals and proportions cannot be controlled
• what are artificial fertilisers

  Artificial fertilisers are chemicals created to contain exact proportions of minerals
• evaluate artificial fertilisers

  Inorganic substances are more water soluble, and therefore more of these ions dissolve in the water surrounding the soil.

  Whilst this is an advantage to the plant for absorbing the nitrates and phosphates, the downside is that their high solubility means that larger quantities are washed away with rainfall and therefore have a greater impact on the environment.
• what is leaching

  Leaching is when water-soluble compounds are washed away, often into rivers or ponds.

  If nitrogen fertilisers leach into waterways it causes eutrophication.
• What is the environmental impact of fertilisers

  Leaching
• what is eutrophication

  Eutrophication is when nitrates leached from fertilised fields stimulate growth of algae in pond.

  The excessive growth of algae creates a blanket on the surface of the water which blocks out light.

  As a result plants below cannot photosynthesis and die.

  Bacteria within the water feed and respire on the dead plant matter.

  This results in an increase in bacteria, which are all respiring and using up the oxygen within the water.

  Eventually, fish and other aquatic organisms die due to the lack of dissolved oxygen in the water.
• What is an ecosystem

  An ecosystem includes all the organisms living in a particular area known as the community as well as all the non-living elements of that particular environment.
• what affects the distribution and abundance of organisms

  The distribution and abundance of organisms in a habitat is controlled by both biotic factor (living) e.g. predators, disease and abiotic factors (non-living) such as light levels and temperature. Each species has a particular role in its habitat called its niche which consists of its biotic and abiotic interactions with the environment.
• what is the source of all energy

  The Sun is the source of all energy in ecosystems with photosynthetic organisms using this to produce their own food. These can be termed autotrophs and are producers. Those organisms that cannot synthesise their own food are called heterotrophs with all animals being these.
• how much energy is passed on to new organisms and why

  Only around 10% of chemical food energy is passed on between organisms in the food chain.

  The other 90% is lost to the surroundings as:

  • uneaten parts e.g. the bones.
  • decay of dead material e.g. bacteria may decay some material.
  • excretion e.g. energy is lost in faces exothermic reactions e.g. heat lost in respiration.
• how is the efficiency of energy transfer between tropic levels worked out?

  The efficiency of energy transfer between the trophic levels is worked out using the formula:

  Percentage efficiency = energy available after the transfer / energy available before the transfer

  X 100
• how do we measure biomass

  he biomass can be measured in terms of mass of carbon or dry mass of tissue per given area ver given time. The dry mass is used as the wet mass can vary too much. The chemical energy stored in dry biomass can be estimated using calorimetry. This is carried out in a bomb calorimeter in which a sample of known mass is burnt in pure oxygen. The bomb calorimeter is submerged in water and therefore the change in water temperature can be used to calculate the energy in the sample.
• What is ammonification?

  • Ammonification where microbes known as saprobionts break down organic matter to ammonia in a two stage process. Firstly, proteins are broken down into amino acids with the use of extracellular protease enzymes. These are then subsequently broken down further to remove amino groups with the use of deaminase enzymes.Saprobionts use the products of decomposition for respiration.
• what is nitrification?

  Nitrification where nitrifying bacteria convert ammonia to nitrite ions, NOz, in an oxidation reaction, with a nitrate ion, NO, intermediate. Most plants can take in nitrate ions through their roots.
• what is denitrification

  denitrification is where nitrate ions, NO, are converted to nitrogen gas, N2, by the denitryfing bacteria. This process is wasteful and can be prevented from occurring by soil being well drained and aerated.
• what is nitrogen fixation

  • Nitrogen fixation where nitrogen gas is fixed into other compounds by bacteria with nitrogen fixing ability. They do so by reducing nitrogen gas to ammonia which subsequently dissolves to form ammonium ions. Nitrogen fixing bacteria live in root nodules of leguminous plants. The relationship between nitrogen fixing bacteria and the plant is known as mutualistic as it is beneficial to both organisms
• why is the phosphorous cycle important

  Phosphorus like nitrogen is another element found in many biological molecules that needs to be recycled.
• how do plants take up phosphorus

  Plants can take in phosphate ions, PO, from soil. Phosphate is released from sedimentary rocks as a result of weathering, as well as through the decay of bones, shells and the excreta of some birds.
• what are mycorrhizae and what do they do

  Mycorrhizae are important in facilitating the uptake of water and inorganic ions by plants.

  These are associations between certain types of fungi and the roots of the vast majority of plants. They increase the surface area and act as a sponge holding water and minerals. As a result a plant can better resist drought and take up inorganic ions more easily.
• what do we use fertilisers for

  Natural and artificial fertilisers are used to replace the nitrates and phosphates lost by harvesting plants and removing livestock.