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Title: IB Biology SL Unit 2 notes
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 2 from the new syllabus (first examination in 2016)
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 2 from the new syllabus (first examination in 2016)
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2
...
U1 living processes in terms of the
chemical substances involved
...
Some scientists think that the reductionist
approach alone is ultimately limited
...
g
...
2
...
U2 covalent bonds allowing a
diversity of stable compounds
to exist
...
g
...
4
Covalent bonds are the strongest type of bond
between atoms
...
Covalent bonds formed when 2 adjacent atoms share a pair of
electrons (1 electron contributed by each atom)
2
...
U3 compounds including
carbohydrates, lipids, proteins
and nucleic acids
...
Only one
saturated fat is expected and its
specific name is not necessary
...
The
structure of individual Rgroups
does not need to be
memorized
...
1
...
[Students should be able to
recognize from molecular
diagrams that triglycerides,
phospholipids and steroids are
lipids
...
Proteins or parts
of polypeptides should be
recognized from molecular
diagrams showing amino acids
linked by peptide bonds
...
1 Metabolism is the web of all the
...
Most metabolism happens inside cells, some are extracellular (e
...
food digestion in intestine)
Metabolism sum of reaction occurring in an organism
Metabolic pathway 1 type of molecule is transformed into another
(chains of reactions/cycles)
2
...
U5
2
...
U6
Anabolism is the synthesis of
complex molecules from
simpler molecules including the
formation of macromolecules
from monomers by
condensation reactions
...
A
ribosome condenses two
amino acids into a
dipeptide forming a
peptide bond
The bonds formed are
types of covalent bonds
...
● DNA synthesis during replication
...
● Synthesis of complex carbohydrates including starch,
cellulose, glycogen
Catabolic reactions
release energy, includes:
● Digestion of food in mouth, stomach, small intestine
● Cell respiration in which glucose and lipids are oxidized to
carbon dioxide and water
...
2
...
A1
Urea as an example of a
Wöhler accidentally synthesised urea in 1828, whilst attempting to
compound that is produced by
prepare ammonium cyanate
...
synthesised only by organisms
...
1
...
[Only the ring forms
of Dribose, alpha–Dglucose
and betaDglucose are
expected in drawings
...
2 Water molecules are polar and
...
•ater (H
W
O) is made up of two hydrogen atoms covalently bound
2
to an oxygen atom
•While this bonding involves the sharing of electrons, they are not
shared equally
•The number of protons in each atom is different; oxygen atoms
have 8 whilst hydrogen atoms have just 1
•having more protons the oxygen atoms attract the electrons more
strongly
•Thus the oxygen end of the molecule becomes slightly negative
and the hydrogen end becomes slightly positive
(i
...
the oxygen has a higher electronegativity)
Polar molecules covalently bonded molecules that have a slight
potential charge
The slightly charged regions of the water molecule can attract other
polar or charged compounds
Water molecules can associate via weak hydrogen bonds (between
O and H)
Hydrogen bonds are transitory in nature – they constantly form,
break and reform
Intermolecular bond between molecules
Intramolecular bond in molecules
2
...
U2 dipolarity explain the cohesive,
adhesive, thermal and solvent
properties of water
...
Transparency of water
and maximum density at 4°C do
not need to be included
...
g
...
1)due to polarity of a water molecule and its ability to form
hydrogen bonds
2)Although H bonds are weak large number of bonds
(each water
molecule bonds to four others in a tetrahedral arrangement)
gives
cohesive forces great strength
E
...
water can only be sucked up in xylem if molecules stay
together
Adhesion:
Water molecules tend to stick to other molecules that are charged
or polar for similar reasons that they stick to each other
+1),3) point from coh
...
g
...
Solvent:
dissolves many organic and inorganic substances that have
charged or polar regions
...
g
...
g
...
metabolic reactions happen most readily in solutions of water –
water in cells dissolves the reactants /substrates
soluble substances, e
...
sucrose can be easily transported around
the plant in the phloem
...
Thermal:
has a high
specific heat capacity
(4
...
, which is hard energy required)
has a
high heat of vaporisation
(amount of energy needed to
change from liquid to gas/vapour)→ great cooling effect
has a high
boiling point
(amount of energy needed to evaporate
liquid)
These properties are due to many H bonds that need to be formed
or broken to change the temperature or state of water
Therefore the temperature of water remains relatively stable
Water is used by Leaves as a coolant
...
If the leaves get too hot
enzymes in their cells will start to denature
...
2
...
2
...
U3 or hydrophobic
...
•Substances that water adheres to, cellulose for example, are also
hydrophilic
...
2
...
Glucose
Modes of transport of glucose,
amino acids, cholesterol, fats,
oxygen and sodium chloride in
blood in relation to their
solubility in water
...
2
...
[Comparison of the
thermal properties of water and
methane assists in the
understanding of the
significance of hydrogen
bonding in water
...
E
...
methanogenic prokaryotes live in swamps and other wetlands
...
CH4 nonpolarcan’t form H bonds
...
Methane has
molecular mass 16, water 18
...
Methane has
negative melting and boiling points
...
3 Monosaccharide monomers are
...
Glucose forms the base unit for many polymers
Galactose is also a hexose sugar
...
Most commonly found in milk, but also
found in cereals
[Sucrose, lactose and maltose
Fructose is another pentose sugar
...
It is the sweetest naturally occurring carbohydrate
of disaccharides produced by
Ribose backbone of RNA
combining monosaccharides
...
]
Glucose+glucose → maltose
Glucose +galactose ⇒ lactose
Glucose + fructose → sucrose
Glycosidic bonds can be 14 and 16 C links
2
...
A1
Structure and function of
cellulose and starch in plants
and glycogen in humans
...
(unbranched)
Condensation reactions link carbon atom 1 to carbon atom 4 on the
next
βglucose
...
→ the cellulose molecule is a straight chain, rather than curved
...
The linked molecules form bundles called cellulose microfibrils
...
The tensile strength of cellulose (the basis of cell walls) prevents
plant cells from bursting, even under very high (water) pressure
...
Size of the molecule is not fixed
In amylopectin the chain is branched, so has a more globular
shape
...
Typically amylose is made up of 3003,000 glucose units
Starch is only made by plant cells
...
easy to add or remove extra glucose molecules to starch
→ starch is useful in cells for glucose, and consequently energy,
storage
...
Starch is made as a temporary store in leaf cells when glucose is
being made faster by photosynthesis than it can be exported to
other parts of the plant
...
Branches occur where a
condensation reaction instead links carbon atom 1 – 6
...
stored in liver and some muscles
used in cells where large stores of dissolved glucose would cause
osmotic problems
...
e
...
2
...
U2 monounsaturated or
polyunsaturated
...
]
2
...
S2
2
...
U3 cis or trans isomers
...
g
...
the hydrogen atoms are on the the hydrogen atoms are on the
same side of the two carbon
opposite sides of the two
atoms
carbon atoms
The double bond causes a
bend in the fatty acid chain
The double bond does not
causes a bend in the fatty acid
chain
Therefore cisisomers are only
loosely packed
Transisomers can be closely
packed
Triglycerides formed from
cisisomers are usually liquid
at room temperature, they are
oils, they have low melting
point
Triglycerides formed from
transisomers are usually solid
at room temperature with high
melting point
2
...
A4
Evaluation of evidence and the
methods used to obtain the
evidence for health claims
made about lipids
...
The more
widely spread the data the smaller the significance can be placed
on the correlation and/or the conclusion
...
g
...
3
...
Saturated Fatty acids → CHD (Coronary Heart Disease)
Mediterraneans lowsaturatedfat diet, high
cismonounsaturateddiet low CHD rate
Correlation between transfats and CHD, patients who die coz of
CHD have had high conc
...
3 Triglycerides are formed by
...
Lipids are glycerol combined with 1, 2 or 3 fatty acids, therefore
triglycerides are lipids
Triglycerides e
...
in human adipose tissue and in sunflower seeds
2
...
A3
Lipids are more suitable for
longterm energy storage in
humans than carbohydrates
...
Structure: Phospholipids are a main component of cell membranes
Hormonal signalling: Steroids are involved in hormonal signalling
(e
...
estrogen, progesterone, testosterone)
Insulation: Fats in animals can serve as heat insulators while
sphingolipids in the myelin sheath (of neurons) can serve as
electrical insulators
Protection: Triglycerides may form a tissue layer around many key
internal organs and provide protection against physical injury
Storage of energy: Triglycerides can be used as a longterm
energy storage source, whereas carbohydrates are used for
shortterm energy storage
The lipids that are used are fats
...
Adipose tissue is located
immediately beneath the skin and also around some organs
including the kidneys
...
This is especially critical for active
animals as energy stores have to be carried
...
3
...
2
...
S2
Determination of body mass
index by calculation or use of a
nomogram
...
4
...
4
...
Drawing molecular diagrams to
show the formation of a peptide
bond
...
1
...
4
...
4
...
[Students should know that
most organisms use the same
20 amino acids in the same
genetic code although there are
some exceptions
...
]
Amino acids can be linked
together in any sequence giving
a huge range of possible
polypeptides
...
Hydroxyproline is an example of an amino acid created not by the
genetic code, but modification, after polypeptide formation, of
proline (by the enzyme prolyl hydroxylase)
...
Collagen
is a structural protein used to provide tensile strength in
tendons, ligaments, skin and blood vessel walls
...
4 The amino acid sequence of
...
Ribosomes are the site of polypeptide synthesis, but ribosomes
need a template – the messenger RNA (translated by transfer RNA
molecules carrying specific amino acids)
The amino acid sequence of each polypeptide is stored in a coded
form in the base sequence of a gene
...
4 A protein may consist of a
...
Integrin embrane protein with 2 polypeptides, each has
m
hydrophobic portion in membrane
...
, wounding reduces chance of
breaking
Hemoglobin
4 polypeptides associated nonpolp
...
4 The amino acid sequence
...
Unique properties of amino acids:
● Some are polar/nonpolar
● Some are positively/negatively charged
● Some contain S
The propertied of the amino acid determine how a polypeptide folds
up into a protein
In
globular proteins
(soluble
in aqua) the hydrophobic R groups are folded into the core of the
molecule, away from the surrounding water molecules, this makes
them soluble
...
Amino acid
sequence prevents folding up and ensures that the chain of amino
acids remains elongated
2
...
U7 many different proteins with a
wide range of functions
...
Which level a protein
conforms to is determined by its amino acid sequence
...
g
...
g
...
g
...
4 Every individual has a unique
...
Genome:
all of the genes of a cell, a tissue or an organism
The genome determines what proteins an organism can possibly
produce
...
Example factors would be nutrition,
temperature, activity levels and anything else that affects a cell’s
activities
...
Being a function of both the genome and the environment to which
the organism is exposed the proteome is both variable (over time)
and unique to every individual (including identical twins and
clones)
...
g
...
g
...
4
...
[The detailed
structure of the six proteins
selected to illustrate the
functions of proteins is not
needed
...
Found in high concentrations in leaves and algal cells
Insulin:
●
●
●
A hormone – signals many cells (e
...
liver cells) to absorb
glucose and help reduce the glucose concentration of the
blood
...
Secreted by β cells in the pancreas and transported by the
blood
...
Two antigen (a molecule on the pathogen which provokes
an immune response) binding sites one on each ‘arm’
Binding sites vary greatly between immunoglobulins
(hypervariable) to enable them to respond a huge range of
pathogens
...
g
...
About a quarter of all protein in the human body is collagen
Forms a mesh of fibres in skin and in blood vessel walls
that resists tearing
...
Forms part of teeth and bones, helps to prevent cracks and
fractures to bones and teeth
Spider silk:
●
●
●
●
●
2
...
A2
Different types of silk with different functions
Dragline silk is stronger than steel
When first made it contains regions where the polypeptide
forms parallel arrays (bottom)
Some regions seem like a disordered tangle (middle)
When the stretched the polypeptide gradually extends,
making the silk extensible and very resistant to breaking
...
[Egg white or albumin groups
...
]
2
...
U1
2
...
U2
Heat can cause denaturation: vibrations within the molecule breaks
intermolecular bonds or interactions
...
Soluble proteins often become
insoluble and form a precipitate, as hydrophobic R groups become
exposed to water
...
g
...
Thermophiles are organisms (often archea or eubacteria) that live
in relatively hot conditions (45 to122 °C)
...
Enzymes have an active site to
which specific substrates bind
...
Enzyme:
A globular protein that increases the rate of a
biochemical reaction by lowering the activation energy threshold
(i
...
a biological catalyst)
Substrate reactant in a biochemical reaction
Collision
coming together
of a substrate molecule and
an active site
Most enzyme reactions
occur when the substrates
are dissolved in water
All molecules dissolved in
water are in random motion,
with each molecule moving
separately
If not immobilized the enzyme can move too, however enzymes
tend be larger than the substrate(s) and therefore move more
slowly
Collisions are the result of the random movements of both
substrate and enzyme
The substrate may be at any angle to the active site when the
collision occurs
Successful collisions are ones in which the substrate and active
site happen to be correctly aligned to allow binding to take place
2
...
...
5 Temperature, pH and substrate
...
[Students
should be able to sketch graphs
to show the expected effects of
temperature, pH and substrate
concentration on the activity of
enzymes
...
]
a change in structure→ change in the active site→ the substrate
is no longer able to bind to it
...
g
...
2
Substrate concentration:
● Increase conc
...
All active sites are working at full
capacity
● After opt
...
any increase in conc
...
5 Immobilized enzymes are
...
2
...
A1
Methods of production of
lactosefree milk and its
advantages
...
]
Detergents
contain proteases and lipases to help
breakdown protein and fat stains
● Enzymes are used to breakdown the starch in grains into
biofuels
that can be combusted
● textiles
industry enzymes help in the processing of fibres,
e
...
polishing cloth to make it appear more shiny
● In the
brewing
industry enzymes help a number of
processes including the clarification of the beer
● In
Medicine & Biotechnology
enzymes are widely used
in everything from diagnostic tests tests to contact lens
cleaners to cutting DNA in genetic engineering
...
g
...
Stability of the enzyme to changes in temperature and pH is
increased reducing the rate of degradation, again resulting in cost
saving
...
g
...
g
...
5
...
5
...
Experimental investigation of a
factor affecting enzyme activity
...
Catalyses the
conversion of hydrogen peroxide, a toxic byproduct of metabolism,
into water and oxygen
...
2
...
U1 RNA are polymers of
nucleotides
...
6 DNA differs from RNA in the
...
Nucleotides are linked into a single strand via
condensation reaction
bonds are formed between the phosphate of one
nucleotide and the pentose sugar of the next
The phosphate group (attached to the 5'C of the sugar)
joins with the hydroxyl (OH) group attached to the 3'C of
the sugar
→
phosphodiester bond
between the two nucleotides and
the formation of a water molecule
2
...
U3
2
...
S1
DNA is a double helix made of
two antiparallel strands of
nucleotides linked by hydrogen
bonding between
complementary base pairs
...
[In
diagrams of DNA structure, the
helical shape does not need to
be shown, but the two strands
should be shown antiparallel
...
]
In order for bases to be facing each other and thus able to pair, the
two strands must run in opposite directions (i
...
they are
antiparallel), i
...
one has direction 3’ to 5’, the other 5’ to 3’
● approximately 10 15 bases per twist
...
6
...
2
...
U2 helix and separates the two
strands by breaking hydrogen
Whilst others worked using an experimental basis Watson and
Crick used stickandball models to test their ideas on the possible
structure of DNA
...
they realized:
DNA must be a double helix
...
●
●
●
Separates the two polynucleotide strands by breaking the
hydrogen bonds between complementary base pairs
ATP is needed by helicase to both move along the DNA
molecule and to break the hydrogen bonds
The two separated strands become parent/template
strands for the replication process
2
...
U3 nucleotides together to form a
● This protein family consists of multiple polypeptides
new strand, using the
subunits
preexisting strand as a
● The polymerisation reaction is a condensation reaction
template
...
]
●
●
catalyses the covalent phosphodiester bonds between
sugars and phosphate groups
DNA Polymerase proof reads the complementary base
pairing → mistakes are very infrequent occurring approx
...
7 The replication of DNA is
...
2
...
A1
Use of Taq DNA polymerase to
produce multiple copies of DNA
rapidly by the polymerase chain
reaction (PCR)
...
7
...
1) complementary base pairing
each
of the nitrogenous bases can only
pair with its partner (A=T and G=C)
2) The two new strands formed will be
identical to the original strand
...
It is useful when only a
small amount of DNA is
avaliable for testing e
...
crime scene samples of
blood, semen, tissue, hair,
etc
...
Denaturation: DNA
sample is heated to separate it into two strands
2
...
Elongation: A heattolerant DNA polymerase (Taq) copies the
strands
1 cycle of PCR yields two identical copies of the DNA sequence
Reannealing when increased temperature to break H bonds
between DNA strands but then low temperatures again DNA
double helix
2
...
U4
2
...
U5
Transcription is the synthesis of
mRNA copied from the DNA
base sequences by RNA
polymerase
...
Transcription and translation work together to create a polypeptide
which in turns folds to become a protein
...
● RNA polymerase separates the DNA strands and
synthesises a complementary RNA copy from the
antisense DNA strand
● It does this by covalently bonding ribonucleoside
triphosphates that align opposite their exposed
complementary partner (using the energy from the
additional phosphate groups to join them together)
●
Once the RNA sequence has been synthesised:
○ RNA polymerase will detach from the DNA
molecule
○ RNA detaches from the DNA
○ the double helix reforms
Transcription occurs in the nucleus (where the DNA is)
and, once made, the mRNA moves to the cytoplasm
(where translation can occur)
Sense strand
DNA strand with the same base sequence as RNA
Antisense strand
the other strand that acts as the template and
has a complementary base sequence to both the RNA and the
sense strand
Translation
the process of protein synthesis in which the genetic
information encoded in mRNA is translated into a sequence of
amino acids in a polypeptide chain
A ribosome is composed of two halves, a large and a small subunit
...
7 The amino acid sequence of
...
●
●
●
●
The length of mRNA molecules varies the average length
for mammals is approximately 2,200 nucleotides (this
translates to approximately 730 amino acids in the average
polypeptide)
Only certain genes in a genome need to be expressed
depending on:
○ Cell specialism
○ Environment
Therefore not all genes (are transcribed) and translated
If a cell needs to produce a lot of a certain protein (e
...
β
cells in the pancreas specialize in secreting insulin to
control blood sugar) then many copies of the required
mRNA are created
...
7 Codons of three bases on
...
genetic code
the set of rules by which information encoded in
mRNA sequences is converted into proteins (amino acid
sequences) by living cells
Codons
a triplet of bases which encodes a particular amino acid
As there are 4 bases, there are 64 different codon combinations (4
x 4 x 4 = 64)
...
g
...
● Different codons can translate for the same amino acid
(e
...
GAU and GAC both translate for Aspartate) therefore
the genetic code is said to be degenerate
● The order of the codons determines the amino acid
sequence for a protein
● The coding region always starts with a START codon
(AUG) therefore the first amino acid in all polypeptides is
Methionine
● The coding region of mRNA terminates with a STOP codon
the STOP codon does not add an amino acid – instead it
causes the release of the polypeptide
● Amino acids are carried by tRNA
● The anticodons on tRNA are complementary to the
codons on mRNA
2
...
U8 complementary base pairing
between codons on mRNA and
anticodons on tRNA
...
2) The mRNA contains a series of codons (3 bases) each of
which codes for an amino acid
...
tRNA
molecules bind to a specific amino acid that corresponds to
the anticodon
4) The large subunit binds to the small subunit of the
ribosome
...
e
...
2
...
A2
Production of human insulin in
bacteria as an example of the
universality of the genetic code
allowing gene transfer between
species
...
Porcine insulin has only
one difference in amino acid sequence from human insulin and
bovine insulin has three differences
...
However, some diabetics develop an allergy to animal insulins, so it
is preferable to use human insulin
...
● Each codon produces the same amino acid in transcription
and translation, regardless of the species
...
● Therefore, we can take genes from one species and insert
them into the genome of another species
...
The
same restriction enzyme cuts into the plasmid
...
coli plasmid
...
7
...
7
Use a table of the genetic code
to deduce which codon(s)
corresponds to which amino
acid
...
S3
2
...
S4
and their corresponding amino
acids to deduce the sequence
of amino acids coded by a short
mRNA strand of known base
sequence
...
2
...
U1 release of energy from organic
compounds to produce ATP
...
]
Cell respiration
the controlled release of energy from organic
compounds in cells to produce ATP
ATP retained and useable from of energy
Usually from glucose (carbohydrates), fatty acids/lipids, sometimes
proteins
Cell respiration is controlled by enzymes (metabolic pathways and
cycles)
ADP+P requires energy (energy come from breakdown of organic
compounds)
2
...
U2 immediately available as a
source of energy in the cell
...
The heat energy initially can be used to raise the temperature of
the organism, but eventually it is lost to the environment and cannot
be used for metabolic processes → we need continoius supply of
ATP
ATP splitting → ADP+P releases energy needed for the above
processes
...
8 Anaerobic cell respiration gives
...
Quick anaerobic respiration is needed for fast supply of energy,
when there’s no O2
...
8 Aerobic cell respiration requires
...
We must get rid of the CO2, coz toxic, but water is useful
2
...
A1
Use of anaerobic cell
respiration in yeasts to produce
ethanol and carbon dioxide in
baking
...
Usually an ingredient is added to
the dough to create bubbles of gas, so that the baked bread has a
lighter texture (e
...
yeast)
...
Yeast can respire aerobically or anaerobically, but oxygen in the
dough is soon used up so the yeast is forced to respire
anaerobically
...
Ethanol is also produced by anaerobic cell respiration, but it
evaporates during baking
...
Most bioethanol is produced from sugar cane and
maize, using yeast
...
Fermenters are used to keep the yeast in optimum conditions
...
The ethanol produced by the yeasts is purified by distillation and
water is removed to improve combustion
...
8
...
Aerobic respiration generates a much greater yield of ATP, but
muscle contractions
...
8
...
Rapid generation of ATP enables us to maximise the power of
muscle contractions
...
Afterwards lactate must be broken down
...
It can take several minutes for enough oxygen to be
absorbed for all lactate to be broken down
...
Analysis of results from
experiments involving
measurement of respiration
rates in germinating seeds or
invertebrates using a
respirometer
...
Students are
expected to know that an alkali
is used to absorb CO2, so
reductions in volume are due to
oxygen use
...
]
Aerobic respiration uses 6 molecules of gas (oxygen) and creates 6
molecules of gas (carbon dioxide) = no change in volume, but
carbon dioxide is absorbed therefore the volume of gas in the
respirometer decreases
...
If
the diameter of the capillary tube is known then a volume can be
calculated
Rubber bungs seal tubes
Closes the system to prevent changes
in air volume not due to respiration
Syringe
Used to reset the position of the coloured oil
Metal cage
Keeps the organism in place and away from contact
with the hydroxide solution
...
Tube A
Acts as a control to ensure that changes in the level of
coloured oil are due to respiration, not the reaction of the akali with
atmospheric gases other than carbon dioxide
...
Ethical questions of using live animals:
Is it acceptable to remove animals from their natural habitat for use
in an experiment?
Can the animals be safely returned to their habitat?
Will the animals suffer pain or any other harm during the
experiment?
Can the risk of accidents that cause pain or suffering to the animals
be minimized during the experiment? In particular, can contact with
the alkali be prevented?
Is the use of animals in the experiment essential or is there an
alternative method that avoids using animals?
2
...
U1 production of carbon
compounds in cells using light
energy
...
Carbon dioxide and along
with water is used to produce carbohydrates
...
2
...
U4
2
...
U5
Oxygen is produced in
photosynthesis from the
photolysis of water
...
O2 generated comes from photpysis of H20
Reactions and processes than absorb energy from their
surroundings are
endothermic
2
...
U2 wavelengths with violet the
shortest wavelength and red the
longest
...
Shorter
wavelengths such as
xrays and ultraviolet
radiation have high
energy, longer
wavelengths such as
infrared radiation and
radio waves hav are
energy
...
Visible light wavelengths – 400 to 700 nm
...
sunlight is made up of all the wavelengths of electromagnetic
radiation our eyes can detect
...
9 Chlorophyll absorbs red and
...
[Students should
know that visible light has
wavelengths between 400 and
700 nanometres, but they are
not expected to recall the
wavelengths of specific colours
of light
...
Pigments that absorb all of the colors appear black,
because the inmates no light
2
...
S1
Drawing an absorption
spectrum for chlorophyll and an
action spectrum for
photosynthesis
...
9 Temperature, light intensity and
...
2
...
A1
Changes to the Earth’s
atmosphere, oceans and rock
deposition due to
photosynthesis
...
2%)
...
5 billion years ago
...
Oxygen levels remained at 2% until about 750 million years ago
(mya)
...
Oxygen generation also allowed the formation of an ozone layer
(O3)
...
This, in turn, lead to the evolution of a wider range of
organisms
...
Time and further sedmentation has produced rocks with layers rich
in iron ore called the banded iron formations
...
g
...
2
...
S2
Design of experiments to
investigate the effect of limiting
factors on photosynthesis
...
]
Glucose production can be (indirectly) measured by a change in a
plant's dry biomass
...
2
...
S3
Separation of photosynthetic
pigments by chromatograph
...
]
Gather leaves of different types and colours and use Thin Layer
Chromatography (TLC) to separate the pigments, including
chlorophyll present in a leaf
Title: IB Biology SL Unit 2 notes
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 2 from the new syllabus (first examination in 2016)
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 2 from the new syllabus (first examination in 2016)