Energy and ecosystems

Why are plants considered producers

Produce their own carbohydrates/sugars via photosynthesis

Make biological molecules such as polysaccharides :cellulose,starch lipids and proteins

Define biomass and state how it can be measured

Mass of organic material in living organisms

Measured in terms of

Mass of carbon

Dry mass of tissue per given area per given time

State units of biomass

G/m2/month

Kg/km2/year

Define GPP

Gross primary production- chemical energy store of plant biomass in a given area/volume

Total energy entering as a resulting from the rate of photosynthesis

Define NPP

Net primary production - chemical energy store in plant biomass taking respiratory losses to the environment

Left over to create new biomass to be available for next trohpic level

Suggest why most light falling on producers is not used in photosynthesis + not all energy transferred from sun to producer

-Radiation from sun is reflected or absorbed before it reaches the plant

• light is wrong wavelength to be absorbed by chlorophyll

• Light does not hit chlorophyll molecules

• Another factor limiting photosynthesis. CO2 temp

• Photosynthesis not 100% efficient some energy absorbed not converted into biomass

What equation links NPP and GPP

NPP= GPP-R

Equation for net production of consumers

N= I-(F+R)

I chemical energy ingested as food

F chemical energy lost to environment by faeces and unrine

R respiratory lossless to environment

Suggest why not all energy is transferred from producer to herbivore(primary consumer)

Herbivore does not eat all of the producer -e.g roots

Some parts of producer indigestible do lost due to egestion

Some energy lost in excretion

Suggest why not all energy is transferred from herbivore to carnivore

Some food is indigestible so energy lost in egestion

Energy lost in excretion

Energy lost as heat in respiration ,respiration used to provide energy for muscle contraction +body temp

What is Arable farming 

Growing crops such as wheat barley +oats

What is livestock farming

Rearing animals E.g cows chickens,pigs

How do farmers reduce energy losses to non human food chains

Use pesticides to kill pests

Less crop is eaten by them

Harvest yield higher

How does the use of chemical pesticides increase productivity of crops

Kills pests otherwise damage/eat crops

therefore the crop has to expend less energy on repairing damaged parts 

More energy used for growth 

How do farmers reduce respiratory losses within human food chains 

• Restrict movement of livestock so less energy used for muscle contraction

• Keep animals in warmed environments so less energy used to maintain body temperature 

• Give animals antibiotics so less energy from animals expended on immune system fighting pathogens 

• Give animals concentrated food so less food is indigestible therefore less energy lost in egestion

Why are trophic levels often limited to 4-5

Energy is lost at each level

Efficiency of transfer is low

Total biomass less at higher levels

Insufficient energy available to support large enough breeding population