Lecture 1: Why study plants? Global carbon cycle. Food security.

Question 1

Why study plants?

Answer 1

• Over 90% of Earth’s biomass
• Photosynthesis sustains terrestrial and aquatic ecosystems
• Provide food for an ever‐expanding world population
• Provide energy (biofuels), housing, clothing, pharmaceuticals and
recreation

Question 2

plants have 3 remarkable features:

Answer 2

• physiology
• biochemistry
• development

Question 3

remarkable physiology:

Answer 3

Lack of organismal homeostasis means each cell
has to cope with environmental stresses (temperature, water, nutrients, light
etc).

Question 4

remarkable biochemistry:

Answer 4

Each cell is multi‐functional, simultaneously like
many animal organs. Plants are good at defence (pathogens, herbivory:
secondary metabolites, hence pharmaceuticals).

Question 5

remarkable development:

Answer 5

Development highly influenced by
environmental factors. Development and control of gene expression are
unique.

Question 6

The global carbon cycle:

Answer 6

• Rate of CO2 assimilation and release (respiration & decomposition) are matched
• but rate or release of carbon from fossil fuels (coal, oil gas) is not matched by the rate of sequestration into deep oceans. hence build up in atmosphere

Question 7

is photosynthesis a big process?

Answer 7

• Annual energy use is only ~10% of net primary production
• Total stored fossil carbon only ~70 years of net primary production
• One hour of sunlight falling on our planet is equal to all the energy we use
globally in a year.

Question 8

anthropogenic

Answer 8

originating in human activity.

Question 9

anthropogenic changes in CO2–>

Answer 9

changes in land use = clearing of forests & the cultivation of soils for food or biofuel production
AND combustion of fossil fuels.
BOTH INCREASE CO2

Question 10

atmospheric CO2 concnetrations at mauna loa (PPM)

Answer 10

1960 just below 320 ppm

in dec 2016 = 404 ppm. v quick increase

Question 11

patterns of CO2 conc at Mauna Loa due to

Answer 11

decreases in summer, increases in winter. WHY?

most vegetation in northern hemisphere. in summer much more carbon fixation

Question 12

CO2 and O2 conc ove rlast 3500 million years

Answer 12

CO2 has reduced from 50,000
O2 has increased to 21%
has been fluctuations in both. Due to rubsico, O2 - evolving photosynthesis and land plants

Question 13

how can you date O2 -evolving photosynthesis

Answer 13

2-2.5 billion years ago
Stromatolites - cyanobactierum found
BIFs : iron –> oxidised, precipitate out. Date shows oxygen increase

Question 14

in 2010-2012 how many were suffering from chronic undernourishment

Answer 14

870 million / 7.1 billion people in the world (1 in 8) - almost all in developing countries

Question 15

production of food must increase by at least 50% by

Answer 15

2050 even to maintain status quo

Question 16

complications with increasing food production

Answer 16

• Less land : Arable land area 3.9% of the
Earth’s surface area. Land for agriculture is
declining (urbanisation).
• Less water: Water resources declining,
currently 1% of global water
• Fewer inputs: Some nutrient resources
are largely non‐renewable (P), costs of
fuel and fertilisers (N) are increasing
• Increased dietary demand for animal
protein (from feed grain)
• Increased demand for biofuels
• Less labour (urbanisation)
• Climate change
• Weak technology and infrastructure of
developing countries

Question 17

form 1960 - 2000 3 main crops: comment on production & price DUE TO

Answer 17

Production increased rapidly
price decreased.
because of green revolution - creation of genetically improved crop varieties (by breeding), & improved agronomic practices. more food & cheaper food

Question 18

food security requires a

Answer 18

Second Green Revolution.
A 50% increase in crop yields in 40 years requires a
compound rate of increase of ~1% per annum

Question 19

The green revolution: is there any evidence that we’ll reach the 50% increase by 2050?

Answer 19

NO.
Average yield beginning to plateau.
Avergae yearly increase over previous 10 yrs - increased now decreasing again (upside bell)

Question 20

Are we using food efficiently? Uses of USA corn (maize)

Answer 20

for every 10 ears of corn that are grown, only 2 are consumed directly by man as food. 8 are used in almost equally amounts for animal feed and for ethanol

Question 21

is animal farming an efficient way of using crops?

Answer 21

NO 
4kg - 8kg of grains in animal feed produce 1kg of meat. 
In Brazil, an area the size
of all the agricultural land
in Switzerland is used to
grow soybeans to feed
Swiss livestock.

Question 22

3 types of biofuel

Answer 22

• first generation biofuels
• second generation biofuels
• third generation biofuels

Question 23

first generation biofuels

Answer 23

primarily from food products:

• bioethanol (from starch)
• biobutanol (from starch)
• biodiesel (soya beans)

Question 24

second generation biofuels

Answer 24

primarily from crop and forest residues and from non‐food energy crops:
-direct combustion of biomass, pyrolysis, gasification
-Cellulosic ethanol
Current technologies and costs are based on small‐scale plants only
recently commercialised.

Question 25

third generation biofuels

Answer 25

-algae

Question 26

Dedicating all U.S. corn and soybean production to biofuels would meet only
__% of gasoline demand and _% of diesel demand

Answer 26

12%

6%

Question 27

is production of biofuels efficient?

Answer 27

Life cycle analysis: Farming, transport and processing all involve inputs and
environmental burdens that must be set against the energy obtained from the biofuel.
Energy yields vary. corn ethanol = 1.25
whereas sugar can biodiesel = 12-14
neither fab

Question 28

EU’s aim of cutting greenhouse gas emissions by 20% by 2020 is causing a surge in palm oil demand leading to :

Answer 28

rainforest destruction.

• Within 15 years, 98% of the rainforests of Indonesia and Malaysia will be destroyed
• Burning forests releases large amounts of CO2