Food supply, plant growth and productivity

Describe food security

Food security is the ability of human populations to access food of sufficient quality and quantity

State why food production has to be increased

Increases in human population and concerns for food security leads to a higher demand for increased food production

Food production must be……

Sustainable and not degrade the natural resources on which agriculture depends

How can food production be increased

-Breeding of higher yielding cultivators

-Use of fertilisers

-Protect crops from pests, diseases and competition

What do breeders seek to develop crops with?

-High nutritional values

-Resistance to pests and diseases

-Physical characteristics suited to rearing and harvesting as well as those that can thrive in particular environmental conditions

Describe agricultural production in terms of crops and plant growth

The are to grow crops is quite limited

All food production is dependent on photosynthesis and factors which control photosynthesis.

Compare livestock produce to crop plants

Livestock produce less food per unit area than crop plants due to a loss of energy between trophic levels

Livestock production is often possible in habitats unsuitable for growing crops

State the 3 fates of light energy and name the main photosynthetic pigments

Light energy can be:

-Reflected

-Absorbed by photosynthetic pigments to generate ATP

-Transmitted

Explain the absorption spectra of the photosynthetic pigments

Each photosynthetic pigment absorbs different wavelengths of light. The absorption spectra shows the wavelength of light that each pigment absorbs

Compare the absorption spectra with the action spectra

The absorption spectra shows the wavelength of light that each pigment absorbs whereas the action spectra shows the relative rate of photosynthesis at different wave lengths of light.

Describe how light energy generates ATP when absorbed by the photosynthetic pigment

Absorbed light energy excites electrons in the pigment molecule. The transfer of these electrons through the electron transport chain releases energy to generate ATP by ATP synthase

Describe photolysis

Photolysis uses light energy to split water into hydrogen ions and oxygen

Oxygen is released and the hydrogen ions are transferred to the co-enzyme NADP to form NADPH

Describe carbon fixation

1. The enzyme RuBisCO fixes carbon dioxide by attaching it to ribulose bisphosphate. (RuBP) producing 3-phosphoglycerate (3PG)

2. The 3-phosphoglycerate is phophorylated by ATP and combined with hydrogen ions from NADPH to form glyceraldehyde-3-phosphate (G3P)

3. Glyceraldehyde-3-phosphate is used to regenerate RuBP and for the synthesis of glucose

State the uses of glucose