3.1 Food Supply, Plant Growth and Productivity Flashcards
what is food security?
the ability of a human population to access food in sufficient quality and quantity to maintain a healthy population
why is food security an increasing issue in the human population?
there is a rapidly increasing human population but no increase in land available for food production
what is meant by sustainable food production?
food is produced without damaging the environment for the future
describe ‘the 5 factors affecting the productivity of a plant: high yielding cultivars, soil nutrients, pests, disease and competition’
High Yielding Cultivars
- breeding programmes can produce new varieties of crop species which are resistant to disease, drought or salt
- new varieties may require higher nutrient levels or particular soil types
Soil Nutrients
- essential minerals must be present in the soil for healthy growth
- crop rotation and the addition of fertilisers can provide the necessary nutrients
Pests
- insects and other animals can feed on the standing crop or act as vectors for disease
- crops can be vulnerable to damage by rodents during storage
Disease
- bacteria, fungi and virus can attack crop plants and weaken them
- some infections may result in the crop being unsuitable for human consumption
Competition
- the growth of weeds will use up valuable resources (such as soil nutrients and water)
- tall weeds may shade crop plants and reduce light levels
- some weed species will inhibit the germination of seeds
how is energy lost from a food chain?
- movement
- heat
- reproduction
what happens to the energy used for growth within the food chain?
it is passed onto the next tropic level
how does energy that is used for growth within the food chain explain why livestock produce less food per unit area than plant crops?
Because there is a 90% loss at each trophic level, a greater amount of energy is available if plant crops are eaten. If the plant is fed to livestock, there will be 90% less energy available resulting in far fewer people being fed.
explain the statement ‘energy is lost from the food chain as waste but not from the food web’
decomposers and other organisms feed on waste material, making the energy available
why might land be used to farm livestock instead of crops?
if the land is unsuitable for crop growth (e.g. the Highlands of Scotland), then it is more efficient to use the land for livestock (e.g. sheep)
what is the word equation for photosynthesis?
carbon dioxide + water — — —> glucose + oxygen
name the 3 fates of light when it hits a leaf
- absorbed
- transmitted
- reflected
describe ‘the absorption spectrum’
- shows specific wavelengths of light that are absorbed by specific pigments
- the leaves contain the pigments: Chlorophyll A, Chlorophyll B and the Carotenoids
why are chloroplasts green?
blue and red light are both absorbed, only green light is transmitted/reflected making the chloroplasts appear green
why is it useful for the plant to have accessory pigments (such as the Carotenoids) in addition to Chlorophyll?
a greater range of wavelengths of light can be absorbed by the leaf, increasing the amount of light used for photosynthesis
describe ‘the action spectrum’
it shows the rate of photosynthesis at each wavelength of light
