Unit 3 - Key Area 1 - Food supply, plant growth and productivity. Flashcards
What is food security?
The ability of human populations to access food of sufficient quality and quantity.
What must food production be?
Must be sustainable, must not degrade natural resources such as water and soil nutrients on which agriculture depends.
Why is there an increased demand for food production?
An increasing human population has lead to an increase in demand for food production.
What is sustainable food production?
Organisms are not harvested at a faster rate than they can reproduce.
What is agricultural production?
It is crop production of the likes of cereals, roots, legumes and potatoes.
What is crop yield?
Crop yield is a measure of how much crop is harvested, compared with how much was planted.
How do fertilisers increase crop yield?
Fertilisers add nutrients back into the soil that may have been limiting plant growth, increasing food production.
How do pesticides increase crop yield?
Pesticides reduce the number of weeds which compete with crops and pests that damage/eat crops.
How does biological control increase crop yield?
A natural predator, parasite or pathogen of a crop pest is introduced to decrease crop numbers.
How does planting genetically modified cultivars of crop plants increase crop yield?
Crops can be genetically modified to be pest resistant, disease resistant, higher yielding and tolerant to a wider range of conditions.
What is a cultivar?
‘Cultivated varieties’ Groups of plants that have been selected for desirable characteristics.
What is different about livestock production?
It is possible to raise livestock in habitats which are unsuitable for growing crops.
Why does livestock production produce less food per unit area?
There is a loss of energy between trophic levels (one stage in a food chain).
What is the rate of food production dependent on?
Food production is dependent on factors which limit the rate of photosynthesis.
Factors which limit the rate of photosynthesis and therefore food production?
Light intensity, temperature and carbon dioxide concentration.
What happens when white light hits a leaf?
Majority is absorbed by photosynthetic pigments in the chloroplasts, the rest is transmitted or reflected.
The four main photosynthetic pigments in the chloroplasts?
Chlorophyll a, chlorophyll b, carotene and xanthophyll. (Carotene and xanthophyll are the carotenoids.) Each pigment will absorb different wavelengths of light.
How to calculate the RF value?
Distance travelled by pigment from origin / distance travelled by solvent from origin.
What does an absorption spectra show?
Shows which wavelengths of light are absorbed most strongly by a photosynthetic pigment, each wave has a different absorption spectrum.
What wavelengths do chlorophyll a and chlorophyll b absorb best?
Blue and red.
What is the role of the carotenoids?
They extend the range of wavelengths of light that can be absorbed and the pass energy onto the chlorophyll for photosynthesis.
What is an action spectra?
Shows the effect of different wavelengths of light on the rate of photosynthesis. It is evidence of the importance of photosynthetic pigments in photosynthesis.
Photosynthesis - Stage 1 - Light dependent stage ~ part one.
The photosynthetic pigments absorb different wavelengths of light. All energy absorbed by carotenoids is passed to the chlorophyll in the thylakoids of the chloroplast.
Photosynthesis - Stage 1 - Light dependent stage ~ part two.
All this energy excites electrons in the chlorophyll molecules. The high energy electrons are captured by a primary electron acceptor and are transferred to an electron transport chain in the thylakoid membrane. As electrons pass through the chain they release energy.
