Section 5.13 Food chain and energy transfer + Energy transfer and productivity

Define Producers:

They are photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions.

Define Consumers:

They obtain their energy by feeding on other organisms.

Primary consumers: Organisms that feed on producers

Secondary consumers: Organisms that feed on primary consumers

Tertiary consumers: Organisms that feed on secondary consumers

Define Saprobionts:

Decomposers that break down complex materials in dead organisms to simple ones, releasing minerals and elements that can be absorbed by plants and contribute to the recycling.

Define Food chain:

Describes the feeding relationships, where the arrows represent direction of energy flow.

Each stage in the chain is called a trophic level

Define Trophic level

The position of organism in a food chain

Define Biomass and information about biomass

Biomass is the total mass of living material in a specific area at a given time.

Problems with biomass:

• Fresh mass is easy to access, however with the varying amounts of water makes it unreliable

• If dry mass needs to be measured this means that the organism needs to be killed, so only a small sample is used, and this sample may not be representative.

Units:

• grams per meter square

• (if volume) grams per cubic meter

The chemical energy stored in dry mass is estimated using calorimeter:

• A sample of dry mass is weighed and burnt in pure oxygen within a sealed chamber called bomb.

• The bomb is surrounded by a water bath

• The heat of combustion causes a temperature rise of the water

• As we know the amount of heat energy to raise the temperature of 1kg of water by 1 degree this is measured in kJ/kg OR kJ/g

Factors that effect how much sunlight gets converted to organic matter in plants?

• Most of the light energy is reflected

• Not all the wavelengths are absorbed

• Light doesn’t fall on chlorophyll

• A limiting factor such as carbon dioxide and temperature can effect the rate of photosynthesis

The equation for productivity in plants:

NPP = GPP - R

• GPP: Is the Gross Primary Production, it is the total quantitiy of chemical energy store in a plant in biomass in a given area or volume.

• R: is respiratory losses

• NPP: Is the chemical energy store left when taking in respiratory losses

This NPP allows the plant to grow and reproduce, and is also available for other trophic levels in the ecosystem.

Why does only some of the biomass get converted between each trophic level?

• Some of the organism is not consumed

• Some of the parts consumed cannot be digested and are lost in faeces

• Some energy lost in respiration (releasing heat to the surroundings)

• Some energy is lost through homeostatsis (regulating body temperature)

What is the Net production of consumers equation

N = I - (F + R)

• N is the net production

• I is the chemical energy store of ingested food

• F is the energy lost in faeces and urine

• R is the energy lost in respiration

What can explain the relative ineffiency of energy transfers between trophic levels?

• Most food chains only have 4 or 5 trophic level, because inefficient energy to support higher trophic levels

• The total mass of organisms in a particular place (biomass) is less at higher trophic levels

What do farmers do to increase biomass?

• Simplify food webs, so there is less competition between crops

• Reducing respiratory losses (such as reducing movement, processed food, controlled temeprature rooms)