Key Area 3.1 - Food supply, plant growth & productivity

What is food security?

The ability of human populations to produce food of sufficient quality & quantity to support the population

Why does food security decease?

Growing human population increases demand for food

How can increased crop yield be achieved?

Using fertilisers & pesticides & intensive farming methods but which can lead to environmental degradation

How should food production be?

Sustainable

What is sustainability?

The ability of food systems to keep production & distribution going continuously without environmental degradation

In which ways should sustainable food be produced?

-contribute to local economies & sustainable livelihoods

-protect the diversity of environment & welfare of farmed & wild species

-avoid damaging natural resources & contributing to climate change

-provide benefits for society

What factors can be manipulated to increase crop yield?

Factors which control photosynthesis

-light intensity

-carbon dioxide concentration

-temperature

How can food production be increased if the area to grow crops is limited?

-identify any factors that are limiting plant growth

-replacing the existing strain of crop plant with a high-yielding cultivar

-protecting plants from factors which reduce growth

What effect will increasing supply of limiting factors have on crop yield?

Growth will increase

How can crops be protected?

With pesticides against pests & diseases, as well as be genetically modified to be self-resistant

How can competition be reduced?

Through use of pesticides against herbicides

What do breeders seeks while developing crops?

Crops with higher nutritional values

Resistance to pests & diseases

Physical characteristics suited to rearing & harvesting

Crops that can thrive in particular environmental conditions

What us a cultivar?

A cultivated variety that has been intentionally selected & bred by humans for specific desirable traits

How much food is passed on in each tropic level of a food chain?

10%

How is energy released in food chains used?

For movement, undigested material & lost as heat to surroundings

What length of food chain if most efficient?

Shorter food chains as a greater quantity of energy is held in the food

Why is livestock production less efficient than crop production?

It generates far less food per unit area of land than plant production

What habitats are better suited for livestock production?

Steep grassy hillsides that are unsuitable for the cultivation of crops

What are the fates of light on a leaf?

Absorbed

Reflected

Transmitted

Why is light energy absorbed?

It's absorbed by photosynthetic organisms to generate ATP for photolysis

Where does photosynthesis occur?

In cells that contain chloroplasts

That are the main photosynthetic pigments?

Chlorophyll a & b

What wavelengths does chlorophyll absorb?

Mainly red & blue

What are carotenoids?

Accessory pigments which extend the range of wavelengths absorbed by chloroplasts & pass the energy to chlorophyll for photosynthesis

What wavelengths do carotenoids absorb?

Blue & green

What is the absorption spectrum?

Shows which wavelengths of light are absorbed by each pigment & to what extent

What are the black bands on an absorption spectrum?

They are the wavelengths that are absorbed by each

What is the action spectrum?

Shows the rate of photosynthesis at different wavelengths of light (how quickly it photosynthesises)

How do we know that there are multiplayer pigments involved with photosynthesis?

The action spectrum never reaches 0 as it's still happening with different wavelengths of light not absorbed by chlorophyll, as they are absorbed by other pigments

Describe the steps in the light reaction.

Absorbed light excites electrons in the pigment molecules

Chlorophyll (a &b) is the main pigment

These high-energy electrons are then transferred through the electron transport chain that releases energy to generate ATP by the enzyme ATP synthase

Energy is also used for the photolysis of water

Water is split into O which is a by-product of the reaction, & H+ ions are transferred to the coenzyme of NADP & combined to produce NADPH

The ATP & H+ ions (carried as NADPH) produced in the light reaction are used in the carbon fixation stage

Describe the steps of carbon fixation.

The enzyme RuBisCO fixes CO2 from the atmosphere by attaching it to RuBP

The 3PG produced is phosphorylase's by ATP & combined with H+ ions form NADPH to form G3P

G3P is used to regenerate RuBP & for the synthesis of glucose

Glucose may be used as a respiratory substrate, synthesised into starch for energy storage or cellulose, a structural carbohydrate, or passed to other biosynthetic pathways

These biosynthetic pathways can lead to the formation of a variety of metabolites such as nucleico acids, protein & fat

What is a limiting factor?

Any factor that restricts the rate of photosynthesis

What are limiting factors?

Light intensity

CO2 concentration

Temperature