IGCSE BIOLOGY
SECTION 2 LESSON 2
Content
Section 2
Structures
and
functions
in living
organisms
a) Levels of organisation
b) Cell structure
c) Biological molecules
d) Movement of substances
into and out of cells
e) Nutrition
f) Respiration
g) Gas exchange
h) Transport
i) Excretion
j) Coordination and response
Content
Lesson 2
e) Nutrition
Flowering plants
2.15 describe the process of photosynthesis and
understand its importance in the conversion of
light energy to chemical energy
2.16 write the word equation and the balanced
chemical symbol equation for photosynthesis
2.17 understand how varying carbon dioxide
concentration, light intensity and temperature
affect the rate of photosynthesis
2.18 describe the structure of a leaf and explain
how it is adapted for photosynthesis
2.19 understand that plants require mineral ions
for growth and that magnesium ions are needed
for chlorophyll and nitrate ions are needed for
amino acids
2.20 describe experiments to investigate
photosynthesis, showing the evolution of
oxygen from a water plant, the production of
starch and the requirements of light, carbon
dioxide and chlorophyll
Content
Lesson 3
e) Nutrition
Humans
2.21 identify sources and describe functions of
carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
Flowering plants
AUTOTROPHS –organisms that can
produce complex organic compounds
from simple inorganic molecules.
They are the PRODUCERS in a food
chain.
Flowering plants
AUTOTROPHS –organisms that can
produce complex organic compounds
from simple inorganic molecules.
They are the PRODUCERS in a food
chain.
HETEROTROPHS – organisms that
cannot produce their own food, but
acquire complex organic molecules by
consuming plants or other animals.
Photosynthesis
LIGHT form
the Sun
CARBON
DIOXIDE
from the air
WATER from
the soil
Photosynthesis
LIGHT form
the Sun
CARBON
DIOXIDE
from the air
WATER from
the soil
GLUCOSE
for biomass
and energy
OXYGEN
released to
the
atmosphere
Photosynthesis
LIGHT
ENERGY
CHEMICAL
ENERGY
Photosynthesis
Light
Carbon dioxide + water
Glucose + oxygen
Chlorophyll
Photosynthesis
Light
6CO2
+ 6H2O
C6H12O6 + 6O2
Chlorophyll
Photosynthesis
Light
6CO2
+ 6H2O
C6H12O6 + 6O2
Chlorophyll
Some of the glucose produced is used in respiration by the plant
itself, but most of it is converted into insoluble STARCH for storage in
stems, roots and leaves.
Factors affecting photosynthesis
Factors affecting photosynthesis
1. Temperature
2. CO2 concentration
3. Light intensity
Factors affecting photosynthesis
Rate of photosynthesis
Temperature
Temperature
Factors affecting photosynthesis
Temperature
Rate of photosynthesis
As temperature rises,
so does the rate of
P/S. Here temperature
is limiting the rate.
Temperature
Factors affecting photosynthesis
Rate of photosynthesis
Temperature
As temperature
approaches 45oC,
enzymes start to
denature and rate of
P/S falls to zero
Temperature
Factors affecting photosynthesis
Carbon dioxide concentration
Rate of photosynthesis
As CO2 increases, so
does the rate of P/S.
At this point [CO2] is
the limiting factor.
CO2 concentration
Factors affecting photosynthesis
Rate of photosynthesis
Carbon dioxide concentration
Increasing [CO2] has no
further effect. The
limiting factor must
now be sunlight or
temperature.
CO2 concentration
Factors affecting photosynthesis
Light Intensity
Rate of photosynthesis
As light intensity
increases, so does the
rate of P/S. At this
point light intensity is
the limiting factor.
Light intensity
Factors affecting photosynthesis
Rate of photosynthesis
Light Intensity
Increasing light
intensity has no further
effect. The limiting
factor must now be
[CO2] or temperature.
Light intensity
Plant mineral requirements
Plant mineral requirements
• For healthy growth plants also need certain
minerals
Plant mineral requirements
• For healthy growth plants also need certain
minerals
• Farmers use fertilisers to add minerals to
soil.
Plant mineral requirements
• For healthy growth plants also need certain
minerals
• Farmers use fertilisers to add minerals to
soil.
• Natural fertiliser = dead plants and animals
and organic waste.
Plant mineral requirements
• For healthy growth plants also need certain
minerals
• Farmers use fertilisers to add minerals to
soil.
• Natural fertiliser = dead plants and animals
and organic waste.
• Artificial (manufactured fertiliser) = made in
factories from chemicals.
Plant mineral requirements
Element
Needed for
Nitrogen (in nitrates)
Proteins for growth of
stems and leaves
Phosphorus (in
phosphates)
Healthy roots
Potassium
Healthy leaves and
flowers
Healthy growth of new
stems
Making chlorophyll
Calcium
Magnesium
Plant mineral requirements
Fastgro
fertiliser
NPK
20:50:30
Elements- Nitrogen,
Phosphorus, Potassium
Ratio of the elements in
the fertiliser
Leaf adaptations
Leaf adaptations
Leaf adaptations
Broad
Thin
Flat
Internal air
spaces
Leaf adaptations
Large
surface
area
Broad
Thin
Flat
Internal air
spaces
Leaf adaptations
Leaf adaptations
Stomata (stoma) on the undersurface of
leaves that allow CO2 to diffuse in and O2
to diffuse out. Water is also lost through
the stomata by transpiration.
Leaf adaptations
Cross section through a leaf
Leaf adaptations
Cross section through a leaf
Waxy cuticle –
stops too much
water from just
evaporating away
from the leaf.
Leaf adaptations
Cross section through a leaf
Waxy cuticle –
stops too much
water from just
evaporating away
from the leaf.
Plants in hot, dry
or windy
conditions have a
thicker wax layer.
Leaf adaptations
Cross section through a leaf
Palisade layer–
most of the
chloroplasts are
found here,
containing
chlorophyll, the
pigment needed
for photosynthesis
Leaf adaptations
Cross section through a leaf
Spongy mesophyll
layer – less
chloroplasts here.
Note the large
number of air
spaces.
Leaf adaptations
Cross section through a leaf
Lower epidermis – note the presence here
of stomata (tiny pores surrounded by
guard cells).
Photosynthesis experiments
Light source
Photosynthesis experiments
Bubbles of oxygen gas
being produced
Light source
Variable: distance of the light
source (= intensity) away from the
pond weed.
Photosynthesis experiments
Testing leaves for starch
Photosynthesis experiments
Testing leaves for starch
Variegated
leaves
Photosynthesis experiments
Testing leaves for starch
Chlorophyll
No chlorophyll
Photosynthesis experiments
Testing leaves for starch
Photosynthesis experiments
Testing leaves for starch
Photosynthesis experiments
Testing leaves for starch
Photosynthesis experiments
Testing leaves for starch
Photosynthesis experiments
Testing leaves for starch
Positive starch result
where the chlorophyll has
been extracted (the
green parts)
Negative starch result in
variegated (white) part of
leaf where chlorophyll is
absent.
Photosynthesis experiments
Carbon dioxide requirements
Geranium plant
Soda lime
Photosynthesis experiments
Carbon dioxide requirements
Leave the plant for a
couple of days – the soda
lime should absorb all the
CO2 in the jar
Geranium plant
Soda lime
Photosynthesis experiments
Carbon dioxide requirements
After a couple of days
there should be no starch
in the leaves.
Geranium plant
Soda lime
End of Section 2 Lesson 2
In this lesson we have covered:
Nutrition – flowering plants