Key Area 1(a) : Food supply Unit 3: Sustainability and Interdependence.

Key Area 1(a) : Food supply

Unit 3: Sustainability and Interdependence

Food security and sustainability

• Why is food security an increasing issue in the human population?

• The human population is increasing more rapidly than food production.

• Less land is available for food production.• What is meant by sustainable food

production?• Continuing production of food without

causing damage or degrading the natural resources that were used to produce it.

CfE Higher BiologySustainability

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• Human populations have to access food and use this food over a sustained period of time.

• This is important because?• Survival – avoid starvation• Health – avoid malnutrition (safe and

nutritious food have more benefits)


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Food security


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QUANTITYSufficient amounts of

food

QUALITY

Nutritious and provides a

balanced diet.

ACCESS

Economic means to obtain food.

Food securit

y

Factors affecting food security• Complete the table to give

explanations of these factors.


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Factors that underpin food security

Explanation

Sustainability

Accessibility

Availability

Usage

Factors affecting food security


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Factors that underpin food

security

Explanation

Sustainability A food source that is able to support populations, maintain its productivity and endure over time without causing any ill effects.

Accessibility A food source that is easily available, near to where it is required and ready to use.

Availability It is convenient, ready to use, easily obtained over long periods.

Usage It is easy to use, process and manage.


• Using the case study in the text book on page 226, answer the following questions.

• What reasons are there that present the challenge of providing a secure supply of food?

• What contributions has ‘biological science’ made to meeting this challenge?

• What other agencies could be involved in a more ‘interdisciplinary approach’ to food security.


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• What are the natural factors that can affect food production?

• Drought• Pests• Flooding• Disease• Desertification• Insecticide resistance• Write a short explanation of how each of these

could effect food production. Use a named example where possible.


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Food Production• Natural resources are vital for food

production.• We need to find an appropriate

balance between


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Providing enough

sustainable quality food

Preventing damage/further damage to the environment

Food Production – factors to consider


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SUSTAINABILITY

Global warming

PollutionSoil: erosion & fertility

Deforestation

Write the biological issue or impact each factor could have on the sustainability of current and future food production

Food Production• Ultimately food production depends on plant

growth.• The main producers of human food are displayed

below:


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Food Production• Small numbers of green plant

species are relied on as main sources of food.

• These small numbers equate to approximately 95% of the worlds food supply.

• The earth itself, however, has at least 75000 species of edible plants.


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Food Producti

on

Competition

Weeds or too dense planting will slow growth

Pests

Decrease yield, either by feeding on crops or by making the plant less healthy

Breeding higher yield cultivars

Will increase yield, but some require more intensive farming methods and are more dependent on particular soil profiles and nutrients

Disease

Decrease yield as the plant is less healthy. May also produce food that is unsuitable for eating

Soil profile

The depth of soil / drainage etc will determine what type of crop you can grow

Soil nutrients

Plants need specific nutrient profiles. Some may need to be added using fertlisers. Can also use crop rotations

Food chains and energy loss• The sun is the ultimate source of energy for most

communities of living things.• Green plants absorb some of the sun’s light

energy to make their own food by photosynthesis.• The other organisms in a food chain are

consumers because they all get their energy and biomass by consuming and eating other organisms.

• Not all energy available to organisms at one stage can be absorbed by organisms at the next one.

• The amount of energy decreases from one stage to the next and only about 10% is passed on.


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Pyramids of Numbers• Pyramids of numbers can be produced based on a

food chain and each layer in the pyramid is called a trophic level.

• Grass grass hopper frog snake hawk


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http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/foodchains/foodchains2.shtml

Food chains and energy loss• Draw a food chain where plants are consumed by

humans.• Draw another food chain where animals are

consumed by humans.• What can you deduce by comparing these two food

chains?• The shorter the food chain the greater the quantity

of energy held in the food.• The fewer the trophic levels the less energy lost.• Therefore more food is generated per unit area of

land when plant crops are grown.• Livestock generates less food per unit of land.


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Photosynthesis• Write the summary equation for

photosynthesis.

Carbon + water oxygen + glucoseDioxide sugarCO2 + H2O O2 + C6H6O12

• Other additional factors that are necessary for photosynthesis to take place are: sunlight and chlorophyll


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Photosynthesis – getting the light• When the light hits a leaf there are 3

things that can happen to it.

• It can be Absorbed (usedin photosynthesis)Reflected

Transmitted


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Reflected12%

Absorbed83% but only 4%

used in photosynthesis

Transmitted5%

Photosynthesis• The light that is absorbed is absorbed by

the pigments in the chloroplasts.


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Granum

Starch grain

Inner membrane

Outer membrane

Stroma

Lamella

Photosynthesis• This light is known as ‘visible light’

on the radiation spectrum.• It covers a narrow band of

wavelengths ranging from 380nm to 750nm.


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Absorption Spectra• What does Absorption mean?• taking something in• An absorption spectrum shows the

specific wavelengths of light that are absorbed.

• In a leaf more than one pigment is involved in the absorption of light.

• These can be separated by using paper or thin layer chromatography.


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Name the colours along the spectrum below and shade them in (ROYGBIV)

Wavelength of light (nm)

700600500400

Violet Indigo Blue Green Yellow Orange Red

Wavelength of light (nm)

700600500400

Shade in the spectrum below showing the areas where light is absorbed

Absorption spectra• The absorption spectra shows how

strongly the different pigments absorb at different wavelengths.

• From this information, why are chloroplasts green?

• They are green because they absorb every other colour apart from green.


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Photosynthetic pigments


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It can also be shown by graphing the wavelength in nm (on the x-axis) against the relative absorbance (on the y-axis).

Photosynthetic pigments• Chlorophyll a and b absorb mainly blue

and red light.• The other pigments, called carotenoids

absorb other colours of light (including the blue-green region of the spectrum) and pass this energy on to the chlorophyll.

• These carotenoids are also called accessory pigments.


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Photosynthetic pigments• Why is it useful to the plant to have

several different pigments?• They can absorb more of the

wavelengths of light.


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Action spectra• An action spectra shows the rate of

photosynthesis at different wavelengths.


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Spectra


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Photosynthetic pigments• A close correlation can be seen between

the overall absorption spectrum for the leaf pigments and the action spectra for photosynthesis.

• The action spectra is made up of all the absorption spectra added together.

• It shows the amount of photosynthesis you get from each wavelength of light (all of the different pigments working together)


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Separation of Photosynthetic pigments

• Pigments from leaves can be extracted using a suitable solvent.

• These can then be separated using either paper or thin layer chromatography.

• The different pigments can be identified by their position on the paper and their colour.

• Rf values can be calculated for each pigment.


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Propanone is usually used as the extraction solvent.A mixture of propanone and petroleum ether is used as the chromatographic solvent.


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Key Area 1(a) : Food supply Unit 3: Sustainability and Interdependence.

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Transcript of Key Area 1(a) : Food supply Unit 3: Sustainability and Interdependence.