13.Energy And Ecosystems Flashcards
What do organisms in any ecosystem rely on?
A source of energy to carry out all their activities
What is a producer
Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide, and mineral ions
What are consumers
Obtain energy by feeding on other organisms rather than using their own energy of sunlight directly.
Primary consumers-plants
Secondary consumers-eat primary
Tertiary consumers-eat secondary
What are saprobionts
Decomposers - break down complex materials in dead organisms into simple ones. Releasing valuable minerals and elements in form that only plants can absorb, work carried out by fungi and bacteria
What is a food chain
Describes feeding relationship in which producers are eaten by primary consumers, etc etc
each stage is called tropic level
Arrows show direction of energy flow
What are food webs
Shows all the consumers and their food sources, all organisms within an ecosystem will be linked to others in the food web
What is biomass
- Total mass of living material in specific area at a given time.
- Fresh mass easy to get but varying amounts of water make it unreliable
- dry mass small sample not representative, organisms killed
How can the chemical energy stored in dry mass measured?
Calorimetry -
How much energy is captured by green plants from sun
Less than 1%
Why is most of sounds energy not converted to organic matter by photosynthesis
- over 90% sun energy reflected back into space by clouds etc
- not all wavelengths of light can be absorbed and used in photosynthesis
- light not fall on a chlorophyll molecule
- factors may limit rate of photosynthesis
What is gross primary production
The quantity of the chemical energy stored in plant biomass at at given time in a given area
What is net primary production
The chemical energy store left after plants have used 20-50%
The chemical energy store left after the losses to respiration have been taken into to account
What’s the equation for npp
Net primary = gross primary — respiratory losses
Production production
What is the low percentage of energy transferred at each stage due to
- Not all of organism not consumed
- some parts consumed not digested so lost in faeces
- some energy lost as excretory materials
- energy losses as heat or respiration
What is the net production of consumers equation
N = I - (F+R)
I is chemical energy store of ingested food
F is energy lost in faeces and urine
R is energy lost is respiration
What does the relative inefficiency of energy transfer between trophies levels explain
- Why only 4/5 trophics levels as not enough energy to sustain more
- total mass of organism in particular place (biomass) is less higher trophic levels
- total amount of available energy is less at each stage
What’s the equation for percentage efficiency
Energy available after transfer
————————————— x 100
Energy available before transfer
What do all nutrient cycles have in common
One simple sequence:
- nutrient taken up by producer as inorganic molecules
- producer incorporates nutrient into complex organic molecules
- when producer eaten, nutrients passes into consumers
- nutrients passes along the food chain when these animals are eaten
- when they die, complex molecules are broken down by saprobiontic microorganisms that release nutrients in original simple form
What percentage of air is nitrogen?
78%
What are the four main stages in nitrogen cycle
Ammonification
Nitrification
Nitrogen fixation
Denitrification
What happens during ammonification
- Production of ammonia from organic nitrogen containing compounds such as proteins, nucleic acids
- ammonia forms ammonium ions in soil
What happens in nitrification
-two stages of oxidation reaction
Ammonium to nitrite
Nitrite to nitrate
What are the two stages of the oxidation reaction in nitrification
Oxidation of ammonium ions to nitrite ions
Oxidation of nitrite to nitrate ions
How do farmers raise the productivity of nitrifying bacteria
As require oxygen, soil can’t get clogged
Soil must be aerated by ploughing, and good water drainage so oxygen isn’t forced out by water
What is happens during nitrogen fixation
Process by which nitrogen gases is converted into nitrogen containing compounds
Carried out industrially and natural through lightening.
Two types by micro organisms:free living nitrogen fixing bacteria, mutualistic nitrogen fixing bacteria
What does free living nitrogen fixing bacteria do
Reduce gaseous nitrogen to ammonia, which they use to manufacture amino acids. Nitrogen rich compounds then released from them when they die
What do mutualistic nitrogen fixing bacteria do
Live in nodules on roots of plants, obtain carbohydrates from plant and plant acquires amino acids from bacteria
What happens during denitrification
- Soils waterlogged, low oxygen conc. microorganisms present changes
- fewer aerobic, more anaerobic denitrifying bacteria
- convert soil nitrates into gaseous nitrogen.
- reduces availability of nitrogen containing compounds for plants.
- soil must be most aerated to prevent build up of denitrifying bacteria
Where is the main reservoir of phosphorous found?
In mineral form
What is the phosphorus cycle
1-weathering and erosion of rocks helps phosphate ions become dissolved and available for absorption by plants which incorporate it into biomass
2-phosphate ions pass into animals which feed on plants.
3-excess phosphatebions excreted by animals, accumulate in waste material
4-death of plants and animals, decomposers break them down releasing phosphate ions back into water or soil, some ions remain as bone that are very slow to breakdown.
5-phosphate ions in excreta released by decomposition are transported by streams and rivers into lakes n oceans where form sedimentary rock
What is the role of mycorrhizae in nutrient cycles
Associations between certain types of fungi and roots of plants.
Vastly increases surface area for water absorption and minerals
Extensions of root system
Acts like sponge
Improves uptake of relatively scarce ions such as phosphate ions
Mutualistic with plant, plant gets water, fungus gets organic compounds
Why are fertilisers needed
- Replace mineral ions in soil that have been absorbed
- As plants don’t decompose in place they grow, and animals don’t either
What are the two types of fertilisers
Natural organic fertilisers - dead and decaying remains of plants and animals as well as animal wastes eg manure slurry and bone meal
Artificial inorganic fertilisers - mined from rocks and deposits, converted into different forms and blended together. Always contain nitrogen phosphorous and potassium
How do fertilisers increase productivity
- Nitrogen is essential for amino acids
- amino acids essential for growth
- when nitrates readily available plants likely to develop earlier, taller, greater leaf area
- increases rate of photosynthesis, improve crop productivity
How has the use of nitrogen containing fertilisers become detrimental
- Reduced species diversity-nitrogen rich soils favour grasses and nettles and other rapidly flowing species, out compete other species
- leaching-pollution of water courses
- eutrophication-caused by leaching of fertiliser into watercourses
What’s leaching
-Process by which nutrients are removed from the soil.
Rainwater dissolves any soluble nutrients, such as nitrate ions and carry them deep into soil, out of reach of plant.
-leached nutrients end up in water courses.
-negative effect on humans if drinking water, prevent oxygen transport in babies and links to stomach cancer
What is eutrophication
Process by which nutrient concentrations increase in bodies of water
Occurs mostly in fresh water lakes
What’s the process of eutrophication
1-low conc of nitrate, limiting factor in plant and algal growth
2-as nitrate ion conc increases as result of leaching, ceases to be limiting factor, populations grow
3-algae bloom, absorbs light
4-light is limiting factor for plants below surface
5-dead organisms used as food, saprobiontic bacteria grow
6-require oxygen, demand increases, oxygen conc reduced, nitrates released from organisms
7-oxygen is limiting factor, without aerobic organisms less comp for anaerobic organism
8-anaerobic further decompose dead material, releasing toxic wastes eg hydrogen sulphide making water putrid
