Transcript Section 5: Use of biological resources

Section 5: Use of
biological resources
Food production
Syllabus
Crop plants
 describe how glasshouses and polythene tunnels
can be used to increase the yield of certain crops
 understand the effects on crop yield of increased
carbon dioxide and increased temperature in
glasshouses
 understand the use of fertiliser to increase crop yield
 understand the reasons for pest control and the
advantages and disadvantages of using pesticides
and biological control with crop plants.
Syllabus
Microorganisms
 understand the role of yeast in the production of beer
 describe a simple experiment to investigate carbon dioxide
production by yeast, in different conditions
 understand the role of bacteria (Lactobacillus) in the production
of yoghurt
 interpret and label a diagram of an industrial fermenter and
explain the need to provide suitable conditions in the
fermenter, including aseptic precautions, nutrients,
optimum temperature and pH, oxygenation and agitation, for
the growth of microorganisms.
Fish farming
 explain the methods which are used to farm large numbers
of fish to provide a source of protein, including maintenance
of water quality, control of intraspecific and interspecific
predation, control of disease, removal of waste products,
quality and frequency of feeding and the use of selective
breeding.
Reasons for increase in food production


World population has exponentially increased
Greater pressure on producing sufficient
quantities of food

Pressures are:




Space
Water shortages
Population
Industrial requirements
Human population growth


Known as the Jcurve
Initial growth
slow because
limiting factors
were present
(eg. Disease,
food supply
limited, until
agricultural
revolution)
Human population growth

Limiting factors absent for human population




Health care ensures people live longer
 Reduction of diseases (eg. polio, small pox, typhoid)
 Improvements in water supply
 Sewage treatments
Agriculture technology means improved varieties (eg.
higher yields, more disease resistant) and more efficient
growing and harvesting techniques.
Industrial revolution
 Better manufactured homes
Technology revolution
 GMO (genetically modified organisms)
Human population growth

Social implications

Pollution







Air
Water
Deforestation
Loss of habitats and species
Soil erosion
More demand for freshwater
More disease
Crop production

Increased by:




Increased amounts of carbon dioxide
Increased temperature
Use of fertilisers
Alternative technologies (intensive agriculture)

Eg. hydroponics
Controlling growth in a
greenhouse
Why is maximizing yields important?
Many farmers use intensive farming methods to
maximize their yields. Why do they do this?
 More food produced
in the same amount
of space.
 Cheaper food for
consumers.
 Lower costs for
farmers.
 Increased energy
efficiency.
In what ways can farmers maximize their yields?
Glasshouses

Material


CO2


Glass or plastic retains the heat that
is reflected off the plants
Can regulate the amount by
releasing the gas into the
glasshouse
Temperature

Add warmth during winter, cool
down in summer by opening vents
How do greenhouses increase yields?
Greenhouse operators raise their yields and profits by
maximizing photosynthesis and controlling other factors.
Products can be grown earlier in the year and in conditions
in which they would not normally grow.
What factors would you
need to control to get
the maximum yields
from photosynthesis?
 light levels
 carbon dioxide
 temperature.
Hydroponics


Growth medium is a solution
Solution can be created that is an exact
measure of nutrients required for a particular
crop
What is hydroponics?
Hydroponics is a technique used to grow plants
without soil.
The plants gain all their nutrients and minerals from
specially-treated water circulating around their roots.
Other conditions, such
as the levels of light
and carbon dioxide, are
also closely controlled.
Many salad crops,
including tomatoes,
lettuces and cucumbers,
are grown in this way.
In what conditions would hydroponics be useful?
Why use hydroponics?
There are many advantages of using hydroponics.
These include:
 Lower risk of crops becoming diseased
from soil-based pathogens and pests.
 Fewer weeds.
 A reduced need for
pesticides and herbicides.
 Crops can be grown in places with
poor soil or little water for irrigation.
However, hydroponics requires expensive equipment and
technical knowledge and so will not be suitable for all
situations.
Fertilisers


Can add the minerals that are lacking in
precise quantities
Organic fertilisers can be used


Animal manure
Green manure (plow plants into soil)
How can losses be reduced?
Not all of a crop planted will be harvested. What
happens to the rest?
13% lost to
disease
58% harvested
13% lost
to pests
16% lost
to weeds
What chemicals are used to cut competition?
Herbicides are used to kill weeds, and pesticides are used
to kill pests, such as insects and fungi.
Pests on the farm


Organisms that reduce the crop or animal yield.
Pests can be controlled by:



chemicals called pesticides
biological control.
Pesticides are named according to the type of
organism they kill




Herbicides – kill weeds
Insecticides – kill insects
Fungicides - kill fungi
Molluscicides – kill molluscs
Pesticides



Chemicals used to kill pests
Pesticides can be specific or broad spectrum
Problems



pollution,
mutations & resistance
Advantages


Cheaper
Immediate effect
Pesticide accumulation
How do pesticides accumulate along food chains?
corn is
sprayed
with a
pesticide
owls eat the
shrews
snails on the corn are
covered with the
pesticide
shrews eat the snails
the accumulated pesticide
in the owl results in weak
eggs that break easily
Biological Control

Use natural predators



Use trap crops to attract the harmful pest
Problems



One organism eats another
Never eradicate pest totally only to a level that no
longer causes significant economic loss.
Expensive
Advantages

Reduce pollution
Methods of Biological Control

Introduction of a natural predator – eg
ladybirds control aphid populations

Introduction of a herbivore – eg moths control
the prickly pear cactus weed

Introduction of a parasite – eg the wasp
Encarsia controls whitefly populations in
tomato crops

Introduction of a pathogen – eg myxomatosis
virus used to control rabbits

Introduction of sterile males – reduction in
number of offspring

Using pheromones – (sex hormones) to
reduce reproductive potential of a population
The right chemical for the job
What are genetically-modified crops?
Crops can be genetically engineered to alter their
characteristics. They are usually called geneticallymodified (GM) crops.
For example, potato plants can be
genetically modified so that their
leaves are toxic to pests such as
the Colorado beetle.
This removes the need to spray
the crop with potentially harmful
pesticides and reduces the risk of
both pesticide accumulation and
crop damage.
GM is sustainable
GM crops are more
resistant to insects and
diseases, so fewer
pesticides are needed.
High-nutrition GM
crops need very little
water and fertilizer,
so droughts would
not cause famine.
Crops can be modified
so that less food is
wasted by spoiling
during storage.
GM crops yield more
food and are better
able to feed the world’s
rising population.
GM is not sustainable
Biotech companies
could modify crops to
produce sterile seeds,
so that farmers are
forced to buy new
seeds every year.
GM produce is too
expensive for many
people to afford.
There is a risk of crosspollination between GM
and non-GM crops
The long-term
effects of GM
produce on
human health
are unknown.
How can livestock be farmed efficiently?
Chickens and pigs lose energy through movement and
thermoregulation. How could a farmer increase the yield of
meat from livestock?
The efficiency of meat
production increases if
animals are kept at a
constant temperature and
their movement is restricted.
They can also be fed
concentrates – food that
leaves very little waste –
and given antibiotics to
combat infections.
Is efficiency always the most important consideration?
What are the problems of livestock farming?
If animals are kept in extremely cramped conditions, they
may start to develop abnormal behaviour.
For example, chickens may
pluck out each other’s
feathers.
Animals are also more likely to
catch diseases if they are
living in a cramped, enclosed
environment.
To help prevent these problems, farmers must comply
with EU regulations, but some people do not think these
regulations are strict enough.
Intensive farming and the environment
Intensive farming must be well managed to prevent
environmental problems. These include problems include:
 Pollution of water supplies
by animal waste.
 Accumulation of pesticides
in food chains.
 Eutrophication of rivers and
lakes due to inappropriate
use of artificial fertilizers.
 Destruction of wildlife
habitat for agricultural land.
 Depletion of soil minerals.
Citizens’ panel
Sustainable farming?
Microorganisms

Biotechnology


is the use of microbes, plant cells or animal cells
to make substances that are useful to us.
Yeast

Beer production

Fermenter used


A vessel used to grow microorganisms
Wine production
Microorganisms in food

Mycoprotein





Fungus
Grown in large vats, producing large quantities of
mycelium
The mycelium is harvested, then dried and shaped into
cakes or chunks ready to be eaten.
Eg. Quorn.
Excellent food because:




High protein content
Very little fat
No cholesterol
Lot of fibre
Source: http://www.anselm.edu/homepage/jpitocch/genbios/surveybi04.html, cited 17/11/06
Fermenters


Microbes like yeast and bacteria can be used
to make useful chemicals on a large scale.
The fermenter is filled with nutrients and a
small amount of microbe such as yeast.
Conditions for best growth

Sterile conditions – the fermenter vessel is made of
stainless steel. Super-heated steam is pumped
through it to kill any unwanted microbes.

Oxygen – some types of microbe need oxygen to
grow. Sterile air is bubbled in from the bottom of the
fermenter. Motorised paddles make sure the oxygen
is stirred in.
Conditions for best growth

Heat – the reactions inside the generator
release a lot of heat. Too much would kill the
microbe culture. Enzymes would be
denatured. Water circulates in a cooling
jacket to lower the temperature.

When fermentation is complete, the products
are run off from a tap at the bottom of the
fermenter. The products are separated and
purified. Finally it is packaged and marketed.
Microorganisms in food

Yoghurt


Bacteria (Lactobacillus bulgarius)
The milk is pasteurised before bacteria is added.
 Pasteurisation = milk heated to high temperatures (70
- 90°C) for 15-30 seconds
This kills off any dangerous bacteria and thickens the
milk.
The bacteria is added to warm milk, left for a few hours,
where it anaerobically respires converting the sugar
(lactose) into lactic acid.
The lactic acid lowers the pH of the milk, causing it to
coagulate (clumps form) = natural yoghurt.
Lactic acid gives it the sour taste.




Microorganisms in food

Single cell protein (SCP)


Eg. Bacteria and fungi
Good source of protein
 Advantageous for the developing world because:





Do not need soil to grow in
Use many different substances as food sources (incl. wastes) =
cheap to grow
Wastes less energy than meat (as it is a food source closer to the
producers, therefore less energy ‘lost’)
Problems
 People are worried about eating microorganisms
 Initially they did not taste good, the taste has improved.
Most SCPs are used as animal feed.
Microorganisms in food

Breadmaking

Yeast


Anaerobically respire producing carbon dioxide (CO2).
When the CO2 is trapped inside dough (mixture of flour
and water), the bubbles make the dough rise.
Microorganisms in food

Breadmaking

The flour contains starch, amylase and protein.




Starch = energy for the yeast
Amylase = breaks down the starch into sugar, so that the
yeast can use it in anaerobic respiration.
Protein = important for the texture of the bread. Eg. Gluten,
which helps trap the CO2 bubbles.
The high temperatures used when baking bread kill
the yeast, break down the alcohol and change the
starch and gluten to make firm bread.
Fish farming
Why are aquatic food chains efficient?
The transfer of biomass and energy in aquatic food
chains can be very efficient. Why is this?
 The organisms do not thermoregulate, so they use less
energy for respiration.
 Very little phytoplankton escapes being eaten so
decomposers take less of the energy.
What could reduce the number of large fish caught?
Can fish be farmed?
Most of the salmon and trout eaten in the UK comes
from fish farms. The fish are reared in giant tanks or
cages.
Put yourself in charge. What could you do to make sure
you raised the biggest possible yield of fish?
Fish farming


Designed to maximise profit without making too
much impact on the environment
Can control factors more easily (similar to a
greenhouse for plants)




Predators at kept away
Specialised food fed to fish
 High in protein
 Colouring agent
 Antibiotic
Control disease
Spawning in aquaria helps prevent reduction in stock
as young fish are not eaten
Increasing yields in fish farms


Do you agree with this
advert? Why
What are the
advantages and
Disadvantages of fish
farming?