Why study agriculture?

The impact on the biosphere

The impact on the biosphere

Use of other resources in agriculture

Use of other resources in agriculture

pollutionpollution

The impact on a country’s

development

The impact on a country’s

developmentProducing enough for human survivalProducing enough for human survival

Key facts to find out

What % of the earth’s surface is

used for agriculture?

What % of the earth’s surface is

used for agriculture?

When was agriculture first

developed?

When was agriculture first

developed?

Where was agriculture first

developed?

Where was agriculture first

developed?

Autotrophic & Heterotrophic

NutritionAutotrophic Nutrition

Heterotrophic Nutrition

Most use light energy during photosynthesis and are called photoautotrophs. E.g. plants, algae and some bacteria.Some are chemoautotrophs e.g. bacteria that harness energy by oxidising inorganic substances (e.g. hydrogen sulphide.

Autotrophic Nutrition is……when organisms can produce their own food or energy.

It is the basis of all agriculture as all food production relies directly or in directly on photosynthesis.

For example:CropsLivestockDairy products Farmed Fish

Photosynthesis equation quiz

Word equation to symbol equation

Heterotrophic Nutrition

Title Page

Heterotroph means…

… ‘different-feeders’. Organisms that cannot produce their own high energy molecules and gain their energy from other living organisms.

E.g. animals, fungi and many bacteria

Heterotrophic NutritionHerbivores: eat plant foods eg, cattle, sheep, poultry, carp.Omnivores: eat both plants & animal foods eg. Pigs. Can be fed on wastes.Carnivores: eat animal foods, eg many farmed fish such as salmon and trout are fed on fish waste and low value fish.

All of the food production systems which humans use are inefficient; whether we consume plants or animals we are only able to obtain a fraction of the original energy supplied in solar radiation

Farming System

% of solar radiationavailable as human food

Cereals 0.2

Sugar beet/potatoes

0.25

Intensive beef 0.005 - 0.025

Intensive milk 0.03 - 0.080

Cattle ranching

0.002 - 0.004

Mixed farming 0.03 - 0.150

Grass ManCow

Energy lost

Cow does not eat all of the grass plant

Man does not eat all of the cow

R R R

R = Respiration (energy is lost as heat)

Faeces Faeces

Energy transfer in the food chain

Energy loss in food chains

NB much of the food that is eaten is not digested and therefore is not assimilated.

NB much of the food that is eaten is not digested and therefore is not assimilated.

Feeding relationships

A luxury item?

An 800 g loaf of bread costs £0.80.

A 400 g steak costs £4.00.

How can the costs of these food items be compared fairly?

This equals £1.00 per 100 g. This equals £0.10 per 100 g.

Why is meat more expensive than bread?

How energy efficient is it to eat meat?Food chains can be used to understand why some foods cost

more than others. Which of these chains is the most efficient?

The first food chain is the most efficient because it contains fewest trophic levels, so less energy will be lost.

Is eating meat less energy efficient? Cattle and other livestock are fed grain and cereals.

Would it be more energy efficient if humans ate the plant crops instead?

If a one-acre field of corn is used to feed cows, it can support one person.

If the same area is used to feed humans directly, it can support 10 people.

Why is so much energy lost?

Assimilation Efficiency

A = C - (F + U) and:

AE = x 100AC

A: AssimilationC: ConsumptionF: FaecesU: UrineAE: Assimilation Efficiency

A: AssimilationC: ConsumptionF: FaecesU: UrineAE: Assimilation Efficiency

The closer the similarity between the tissues of the consumer and the tissues of the food it eats, the higher the assimilation efficiencyThe closer the similarity between the tissues of the consumer and the tissues of the food it eats, the higher the assimilation efficiency

Feeding type Typical assimilation efficiency / %

Herbivore 30-60

Ruminant 50

Carnivore 70-90

Homeotherms (animals which regulate their internal temperature) use e.g. 95% of the assimilated material just keeping warm

This means that their growth or production efficiency (P/A) is very low - usually just 1 - 3%

Food chain efficiencies are well below 100%, so the amount of energy available drops rapidly as it passes along successive trophic levels

An animals digestive system may be adapted to enable it to live in a habitat that cannot be

exploited by other species?

Can you think of examples of this?Can you think of examples of this?

Cattle and sheep symbiotic gut bacteria that can digest cellulose. Therefore they can eat foods unavailable to other livestock and can graze poor pasture land which may have no other agricultural uses.

Cattle and sheep symbiotic gut bacteria that can digest cellulose. Therefore they can eat foods unavailable to other livestock and can graze poor pasture land which may have no other agricultural uses.

What trophic level does this food come from?

Why do some animals need more energy? Mammals and birds are

able to regulate their body temperature. This has many advantages but it uses lots of energy.

Other animals, such as snakes, lizards and fish, are unable to regulate their body temperature, so need less energy.

Would it be more energy efficient to farm snakes for food than chickens?

How do you calculate efficiency?Energy efficiency can be calculated using the following equation:

=efficiencyenergy used for growth (input)

energy supplied (output)

For example, if grass receives 1,000,000 kJ of energy from the Sun and uses 20,000 kJ of energy for growth, then:

efficiency =1,000,000 kJ

20,000 kJ

= 0.02 = 2%

Assimilation EfficiencyHowever, homeothermy allows them to exploit cold environments which poikilotherms cannot

PE of animals vary with:1. food quality 2. the length of the life cycle

Most humans are omnivores - they eat both meat and vegetables.In terms of our AE, our digestive systems are better suited to cope with meat than vegetables because:• we lack cellulose-digesting bacteria in the equivalent of a rumen• we don’t eat our soft faeces e.g. as rabbits do.

However, in terms of energy efficiency and land use, humans would be much better off trying to satisfy their energy requirements by eating vegetables and crops, rather than feeding them to cattle and eating the meat

By introducing another stage into the food chain (crop cattle humans rather than crop humans) a huge amount of energy is lost

Farmers try to maximise PE by:1. using high quality foodstuffs (increasing AE)2. reducing metabolic energy loss (by keeping the animals

warm and by restricting their movement)

Energy efficiency calculations