Unit 3 Key area 1

Question 1

Define the term food security?

Answer 1

Food security refers to the ability of a human population to produce food of a sufficient quantity and quality.

Question 2

Explain the effects that an increase in population has?

Answer 2

An increase in population can cause a concern for food security. This causes a demand for increased food production. However food production must be sustainable and must not degrade the natural resources on which agriculture depends.

Question 3

Give some examples of factors that food production is dependant on?

Answer 3

Increased food production will be dependant on factors that control plant growth including:
- breeding of higher yielding cultivars
- use of pesticides/herbicides
- use of fertilisers
- reducing diseases and competition.
All of these factors must be used as the area used to grow crops is limited.

Question 4

Give some examples of traits that are selected for by plant breeders in cultivars?

Answer 4

• Higher yielding
• Higher nutritional values
• Physical characteristics that lend themselves to rearing
• The ability to survive in certain climates
• Resistance to pests or diseases

Question 5

Explain the reasons why livestock production produces less energy per unit area than crop production?

Answer 5

As in livestock production energy is lost between the trophic levels. hence it is more energy efficient to plant a field with crops than the same field with grass to feed livestock.

Question 6

What can we use areas that are unsuitable for crop production for?

Answer 6

Areas that are unsuitable for crop production such as grassy hillsides are good for livestock production as crops cannot be grown here efficiently.

Question 7

State the three fates of light when entering a leaf?

Answer 7

Light will either be
- Transmitted
- Reflected (green wavelengths)
- Absorbed (red - blue wavelengths)

Question 8

Describe the role of carotenoids in photosynthesis?

Answer 8

Carotenoids increase the ranges of wavelengths that can be absorbed by the leaf and pass the extra energy on to the chlorophyll to be converted into ATP.

Question 9

Describe what an absorption spectrum is?

Answer 9

An absorption spectrum is a spectrum that shows the ranges of different wavelengths of light absorbed by the leaf and the amount of each wavelength absorbed.

Question 10

Describe what is meant by an action spectrum?

Answer 10

An action spectrum is used to show the rate of photosynthesis at different wavelengths of light.

Question 11

Give an account of the first stage of photosynthesis?

Answer 11

• Absorbed light excites electrons in the chloroplast
• These excited electrons then travel through the electron transport chain releasing energy
• The energy released by the excited electrons can be converted into ATP by the enzyme ATP synthase
• ATP is used in photolysis where water is broken down into oxygen and hydrogen
• oxygen is evolved from the cell
• the coenzyme NADP combines with hydrogen to form NADPH
• This process occurs in the granum of the chloroplast

Question 12

Write notes on the calvin cycle?

Answer 12

• this takes place in the stroma
• The enzyme RuBisCo fixes carbon by attaching it to RuBP forming 3PG
• 3PG reacts with ATP and hydrogen from the light reactions stage to form molecules of G3P
• G3P can either be regenerated back into RuBP or converted to glucose
• The G3P converted to glucose can either be used as a respiratory substrate, stored as starch, converted to cellulose or used for other biosynthetic pathways.
• These biosynthetic pathways can produce fats, proteins, or DNA