Food Supply, Plant Growth and Productivity (2) Flashcards
What is food security?
The ability to access food in sufficient quantity and quality.
Why is there a higher demand for food?
The rising population.
What is access in terms of food security?
Being able to afford it.
Why must food production be sustainable?
To not have a negative impact on the ecosystem and natural resources.
What is needed to maintain a sustainable food supply when producing more food in the same area of land?
- increased plant productivity
- manipulation of genetic diversity
What are the four plant crops from which most human food comes?
- cereals
- potatoes
- roots
- legumes
What does all food production rely on?
Photosynthesis
What are the four factors that control plant growth?
- Light
- Nutrients
- Water
- Competition
How can you improve the efficiency of food production (four ways)?
- Control of limiting factors - use of fertilisers for example
- Planting crops with a higher yield
- Removing competition - pesticides, fungicides, herbicides
- Developing pest-resistant crops
Why is the production of livestock less efficient than growing crops?
90% of energy is lost between each trophic level - requires a lot more energy and water.
When can livestock be more efficient than growing crops?
When the habitat is unsuitable for growing crops.
How can humans be more sustainable?
Eat more vegetables and cut down on meat.
What is photosynthesis?
The process by which green plants trap light energy and use it to make carbohydrates.
What happens to the 100% of the light that strikes a leaf?
12% is reflected
5% is transmitted through the leaf
83% is absorbed by the pigments within the chloroplasts
What percent of the light that strikes the leaf is actually used for photosynthesis?
4%
What are photosynthetic pigments?
Chemicals within the chloroplasts that absorb light energy and convert it to chemical energy.
What are the principal pigments?
Chlorophyll a and b.
What light does chlorophyll a and b absorb?
Red and blue wavelengths of light.
What are carotenoids?
Carotene and xanthophyll - absorb light from other regions of the spectrum.
What is the absorption spectrum?
Shows the wavelengths of light absorbed by the different pigments in a leaf.
What is the action spectrum?
Shows how effective the different wavelengths of light are at photosynthesis.
What is the benefit of having multiple photosynthetic pigments?
Increase the range of wavelengths of light that a plant can absorb and therefore increases the level of photosynthesis.
What can glucose made from photosynthesis be used for?
- energy source
- energy storage (linked to form starch)
- building material (can be linked to form cellulose used in cell walls)
- produce other food types (can be used to make fat or amino acids).
Describe the first stage of photosynthesis.
Light energy absorbed by the pigments gets captured by the electron transport system which releases energy. Some of the energy released is used to generate ATP by the enzyme ATP synthase. The rest of the energy is used for the photolysis of water. The hydrogen from this bonds to the coenzyme NADP to form NADPH. This is transferred to the Calvin Cycle with ATP.
What is photolysis?
Water is split into oxygen and hydrogen.
What is the second stage of photosynthesis called?
Calvin Cycle or the carbon fixation stage.
Which part of photosynthesis requires light?
The first part; the Calvin Cycle doesn’t.
What is the carbon fixation stage?
A series of enzyme-controlled reactions which do not require light.
Describe the second stage of photosynthesis.
Carbon dioxide enters the cycle and attaches to RuBP by the enzyme RuBisCO and produces 3PG. The 3PG is phosphorylated by ATP and combined with hydrogen from NADPH to form G3P. G3P is used to regenerate RuBP or used to synthesis sugars.
What is RuBP?
Ribulose biphosphate
What is 3PG?
3-phosphoglycerate
What is G3P?
glyceraldehyde-3-phosphate
Which part of photosynthesis is temperature dependant?
The Calvin Cycle/carbon fixation stage.
What can the glucose produced in photosynthesis also be used for?
Passed into other biosynthetic pathways to form DNA.
