4.7 Energy efficiency

Why is only 10% of energy passed from one trophic level to the next?


- Not all energy available to next consumer...lost in:

   - Consumer's life processes (Respiration)
   - Undigested food (faeces)

e.g. 90kJ of plant's energy used by aphid for above, 10kJ left for next consumer

...Because the 90% is used by the consumer (not producer, e.g. grass) for life processes, and in undigested food.

4.6 Energy & Substances in food chains

Producer


Light E -- Photosynthesis --> Chemical E 

= Organic molecules (Carbohydrates, Proteins, Lipids) - Food to next in-line food chain

---> Substances / matter =  (C, H, O, N) contain ENERGY in bonds are passed through food chain

4.5c Food Pyramids

Pyramids - develops on food chains, to quantify trophic levels


Number (counting) = no. of organisms / trophic level = Easiest

Note: Draw pyramids appropriate to quantity e.g. 1 / 10 the quantity = 1 / 10 the size

---> DISADVANTAGES: Does not accurately represent energy balance within system

Biomass (dry mass only, w/o H2O)

Living material and their weight (g, kg, etc.)

Gives better understanding of mass of matter 

---> Need to dry out organism for calculation = impractical

Energy Transfer - 'ideal' to show energy transfer = Accurate

Represents as an accurate percentile, the reduction of energy at each trophic level
Does not face 'pyramid inversion' problem


---> Time consuming, difficult to research and produce

4.5b Food Webs

Webs - provides better description of ecosystem (than chains)

Ecosystem - community of organism that interact (through feeding)

Advantages of food webs


Allows us to show organisms feeding at different trophic levels:
  
     --> Multiple predators
     --> Multiple prey

= Causes links to form in web

4.5a Food Chains

Chain - flow of matter / energy


Producer ---> 1st Consumer ---> 2nd Consumer ---> 3rd Consumer

CAN

Show 1 organism per 1 trophic level

CANNOT

Show organisms being omnivores
Show organisms feeding at > 2 trophic levels

4.4 Trophic Levels

Trophic - to feed


Example:

Producers


Plants (photosynthesis) - Light energy ---> Chemical energy

Primary consumer

Herbivore - Chemical energy (Plant) ---- digestion changes to -----> Chemical energy (Fly)

Secondary consumer


Carnivore - CE ---> CE

Tertiary consumer


Top carnivore - CE --> CE

--- eventually all levels ---> DEATH

Broken down by 'decomposer' organisms (fungi, bacteria)

---- Recycles complex molecules -----> Nitrates & Phosphates 

4.3 Samplings with Quadrats

Method - to compare populations / to estimate populations


Sample - Random (no bias), using non-human factors e.g. Online, Tables.
               - Representative (large, estimation close enough to true population), 10% of area

Example: Sampling daisy population in field

1. Set up grid system across field (like x,y co-ordinates on graph) - EQUAL sizes

2. Place quadrat in 'random co-ordinates' (see above) given.

NOTE: Place quadrat in top-right hand side of 'co-ordinate'

3. Count population within quadrat (population/area ----> e.g. 10 daisies/1m^2)

4. Average = total sum of population / total amount of quadrat samplings

     --> (4+3+5) / 3 = 12 / 3 = 4 daisies/m^2

4.2 Quadrates

Quadrates = Method of sampling different locations within an ecosystem, to compare respective population sizes.

Sand Dune Ecosystem (for example) --> Community / Habitat, split by fence

--> Grazed (A)
--> Ungrazed (B)

Counting population (Quadrating): Estimate of population size 
    Using squares (1m x 1m)
    Take sample of population using square grid
    Count number of organisms

4.1 Ecosystems

Ecosystem: '' Community of organisms in a habitat ''

     -> Community of Organisms
             Populations of different species & interactions
              - Number of individuals of a particular species
              - Organisms that reproduce to give fertile offspring
              - Feeding (food chain)


     -> Habitat
            Abiotic: non-biological factors
            - Cycle of daylight (photoperiods)
            - Temperature: local/seasonal/annual cycles
            - Rainfall
            - Humidity
            - Slope of land/geology