Table Of ContentO X F O R D I B S T U D Y G U I D E S
Andrew Allott
B i o lo g y
FO R TH E I B D I PLO M A
2014 edition
2
3
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Introduction and acknowledgements
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IntroductIon and acknowledgements iii
Contents
1 cell BIologY
Autosomal genetic diseases 43
Cell theory 1 Sex-linkage 44
Unicellular and multicellular organisms 2 Co-dominance 45
Stem cells 3 Mutation 46
Light microscopes and drawing skills 4 Genes and alleles 47
Electron microscopes and ultrastructure 5 Gene sequencing 48
Prokaryotic cells 6 DNA technology 49
Eukaryotic cells 7 DNA proling 50
Models o membrane structure 8 Genetic modication 51
Membrane structure 9 Cloning 52
Diusion and acilitated diusion 10 Questions genetics 53
4 ecologY
Osmosis 11
Active transport 12 Modes o nutrition 54
Origins o cells 13 Communities and ecosystems 55
Mitosis 14 Energy fow 56
Cell cycles and cancer 15 Food chains and energy pyramids 57
Questions cell biology 16 Nutrient cycles 58
2 molecular BIologY
Carbon cycle 59
Molecules to metabolism 17 Global warming and the greenhouse eect 60
Water 18 Rising carbon dioxide concentrations 61
Water and lie 19 Questions ecology 62
5 eVolutIon and BIodIVersItY
Carbohydrates 20
Molecular visualization o polysaccharides 21 Introducing evolution 63
Lipids 22 Further evidence or evolution 64
Lipids and health 23 Natural selection 65
Amino acids and polypeptides 24 Natural selection in action 66
Protein structure and unction 25 Naming and identiying 67
Enzymes 26 Classication o biodiversity 68
Factors aecting enzyme activity 27 Classication o eukaryotes 69
Structure o DNA and RNA 28 Cladistics 70
DNA replication 29 Questions evolution and biodiversity 71
Transcription and translation 30 6 Human PHYsIologY
The genetic code 31
Digestion 72
Cell respiration 32
Absorption 73
Respirometers 33
The cardiovascular system 74
Photosynthesis 34
The heart 75
Investigating limiting actors 35
Deence against inectious disease 76
Chromatography 36
Antibodies and antibiotics 77
Questions molecular biology 37
Ventilation 78
3 genetIcs
Gas exchange 79
Chromosomes 38 Neurons and synapses 80
Karyograms 39 Nerve impulses 81
Meiosis 40 Regulating blood glucose and body temperature 82
Meiosis and genetic variation 41 Leptin and melatonin 83
Principles o inheritance 42 Reproductive systems 84
iv contents
Conception and pregnancy 85 Chi-squared and continuous variation 126
Research into reproduction 86 Speciation 127
Questions human physiology 87 Questions genetics and evolution 128
7 nucleIc acIds 11 anImal PHYsIologY
Landmarks in DNA research 88 Antigens and allergy 129
DNA replication 89 Antibody production 130
Base sequences in DNA 90 Vaccination and monoclonal antibodies 131
Bioinormatics and nucleosomes 91 Muscle 132
Gene expression 92 Muscle contraction 133
Epigenetics 93 Movement 134
Ribosomes and transer RNA 94 Excretion and osmoregulation 135
Translation 95 Kidney structure and ultraltration 136
Primary and secondary structure o proteins 96 Urine production and osmoregulation 137
Tertiary and quaternary structure o proteins 97 Kidney unction and kidney ailure 138
Questions nucleic acids 98 Excretion and osmoregulation in animals 139
8 metaBolIsm, cell resPIratIon Spermatogenesis 140
and PHotosYntHesIs Oogenesis 141
Fertilization 142
Enzymes and activation energy 99
Pregnancy and childbirth 143
Enzyme inhibition 100
Structure and unction o the placenta 144
Controlling metabolic pathways 101
Questions animal physiology 145
Glycolysis 102
a neuroBIologY and BeHaVIour
Krebs cycle 103
ATP production by oxidative phosphorylation 104 Neurulation 146
Mitochondria 105 Development o the nervous system 147
Light-dependent reactions o photosynthesis 106 Functions o the brain 148
Chloroplast structure 107 Cerebral hemispheres 149
Light-independent reactions o photosynthesis 108 Perception o stimuli 150
Calvins experiments 109 Vision in humans 151
Questions metabolism, cell respiration and Hearing in humans 152
photosynthesis 110 Innate behaviour (HL only) 153
9 Plant BIologY Learned behaviour (HL) 154
Transpiration 111 Neurotransmitters and synapses (HL only) 155
Investigating transpiration 112 Ethology (HL only) 156
Water uptake and water conservation 113 Questions neurobiology and behaviour 157
B BIotecHnologY and InFormatIcs
Vascular tissue in plants 114
Water transport in xylem 115 Microorganisms and ermenters 158
Phloem transport 116 Microorganisms in industry 159
Research in plant physiology 117 Genetic modication o crop plants 160
Plant hormones and growth o the shoot 118 Bioremediation 161
Reproduction in fowering plants 119 Biotechnology in diagnosis (HL only) 162
Propagating plants 120 Biotechnology in therapy (HL only) 163
Questions plant biology 121 Bioinormatics (HL only) 164
10 genetIcs and eVolutIon Questions biotechnology and bioinormatics 165
c ecologY and conserVatIon
Mendels law o independent assortment 122
Dihybrid crosses 123 Community structure 166
Genes linked and unlinked 124 Interactions and energy fow 167
Crossing-over 125 Nutrient cycles and change in ecosystems 168
contents v
Impacts o humans on ecosstems 169 Cardiolog 179
Biodiversit and conservation 170 Endocrine glands and hormones (HL onl) 180
Populations (HL onl) 171 Carbon dioide transport (HL onl) 181
Nitrogen and phosphorus ccles (HL onl) 172 Ogen transport (HL onl) 182
Questions ecolog and conservation 173 Questions human phsiolog 183
d Human PHYsIologY
Human nutrition 174 ExAM ADVICE 184
Defcienc diseases and diseases o the gut 175 NATURE OF SCIENCE A SUMMARy 186
Digestion and absorption 176 ADVICE FOR INTERNAL ASSESSMENT (IA) 188
Liver 177 ANSWERS TO QUESTIONS 189
Cardiac ccle 178 INDEx 196
vi contents
1
C E LL B I O LO G Y
Cell theory
INTRODUCING THE CELL THEORY
One the most important theories in biology is that cells are the o indivisible subunits, but the invention o the microscope
smallest possible units o lie and that living organisms are settled this debate. Cells consist o cytoplasm, enclosed in a
made o cells. The ancient Greeks had debated whether living plasma membrane. In plant and animal cells there is usually a
organisms were composed o an endlessly divisible uid or nucleus that contains genes.
Human cheek cell
Moss leaf cell
cytoplasm chloroplasts
plasma
membrane
cell wall
nucleus
plasma
cytoplasm
membrane
nucleus mitochondria sap in vacuole
vacuole membrane
EXCEPTIONS TO THE CELL THEORY DRAWINGS IN BIOLOGY
The cell theory was developed because biologists observed The command term draw is defned by IB as: Represent
a trend or living organisms to be composed o cells. Scientifc by means of a labelled, accurate diagram or graph, using
theories can be tested by looking or discrepancies cases a pencil. A ruler (straight edge) should be used for straight
that do not ft the theory. There are some tissues and lines. Diagrams should be drawn to scale.
organisms that are not made o typical cells: A sharp pencil with a hard lead (2H) should be used. This allows
1. Skeletal muscle is made up o muscle fbres. Like cells clear, sharp single lines to be drawn. In exams, diagrams should
these fbres are enclosed inside a membrane, but they not be drawn aintly as they will not show clearly in scans.
are much larger than most cells (300 or more mm long)
and contain hundreds o nuclei.
2. Giant algae such as Acetabularia (below) can grow to a
length o as much as 100mm so we would expect them
to consist o many small cells but they only contain a
single nucleus so are not multicellular.
bad good
There should be no gaps, overlaps or multiple lines.
cytoplasm
bad good
Labelling can be in ink or pencil, with labelling lines rather
20 mm
than arrows. Labelling lines should be drawn using a ruler and
they should point precisely to the structure being labelled.
nucleus
3. Aseptate fungi consist o thread-like structures called
hyphae. These hyphae are not divided up into sub-units
containing a single nucleus. Instead there are long
undivided sections o hypha which contain many nuclei.
cell cell
Despite these and some other discrepancies, there is still a
bad good
strong overall trend or living organisms to be composed o
cells, so the cell theory has not been abandoned.
CELL BIOLOGY 1
Unicellular and multicellular organisms
FUNCTIONS OF LIFE IN UNICELLULAR ORGANISMS
Unicellular organisms consist o only
one cell. They carry out all unctions o
cilia
lie in that cell. Two examples are given agellum
here: Paramecium lives in ponds and contractile vacuole
is between a twentieth and a third o a eye spot
millimetre long. Chlamydomonas lives in plasma membrane
reshwater habitats and is between 0.002 nucleus
cell wall
and 0.010 millimetres in diameter. They
cytoplasm chloroplast
are similar in how they carry out some
unctions o lie and dierent in others. food in vesicles
Paramecium Chlamydomonas
Function Paramecium Chlamydomonas
Nutrition Feeds on smaller organisms by ingesting and Produces its own ood by photosynthesis using a
digesting them in vesicles (endocytosis) chloroplast that occupies much o the cell
Growth Increases in size and dry mass by accumulating Increases in size and dry mass due to
organic matter and minerals rom its ood photosynthesis and absorption o minerals
Response Reacts to stimuli, e.g. reverses its direction o Reacts to stimuli, e.g. senses where the brightest
movement when it touches a solid object light is with its eyespot and swims towards it
Excretion Expels waste products o metabolism, e.g. CO Expels waste products o metabolism, e.g. oxygen
2
rom respiration difuses out o the cell rom photosynthesis difuses out o the cell
Metabolism Both: produces enzymes which catalyse many diferent chemical reactions in the cytoplasm
Homeostasis Both: keeps internal conditions within limits, e.g. expels excess water using contractile vacuoles
Reproduction Both: reproduces asexually using mitosis or sexually using meiosis and gametes
MULTICELLULAR ORGANISMS DIFFERENTIATION
As a cell grows larger its surace area to volume ratio An organisms entire set o genes is its genome. In a
becomes smaller. The rate at which materials enter or leave multicellular organism each cell has the ull genome, so it
a cell depends on the surace area o the cell. However, the has the instructions to develop into any type o cell. During
rate at which materials are used or produced depends on the diferentiation a cell uses only the genes that it needs to ollow
volume. A cell that becomes too large may not be able to take its pathway o development. Other genes are unused. For
in essential materials or excrete waste substances quickly example, the genes or making hemoglobin are only expressed
enough. Large organisms are thereore multicellular they in developing red blood cells. Once a pathway o development
consist o many cells. has begun in a cell, it is usually xed and the cell cannot change
Being multicellular has another advantage. It allows to a diferent pathway. The cell is said to be committed.
division o labour diferent groups o cells (tissues)
Heart muscle tissue
become specialized or diferent unctions by the process 20 m
o diferentiation. The drawings (right) show two o the
hundreds o types o diferentiated cell in humans.
EMERGENT PROPERTIES
Emergent properties arise rom the interaction o the Pancreatic islet cell
component parts o a complex structure. We sometimes sum
this up with the phrase: the whole is greater than the sum
o its parts. Multicellular organisms have properties that
emerge rom the interaction o their cellular components.
For example, each cell in a tiger is a unit o lie that has
distinctive properties such as sensitivity to light in retina
cells, but all o a tigers cells combined give additional
4000
emergent properties or example the tiger can hunt and kill
and have a proound ecological efect on its ecosystem. vesicles of insulin
2 CELL BIOLOGY
Stem cells
STEM CELLS ETHICS OF THERAPEUTIC USE OF
Stem cells are dened as cells that have the capacity to divide STEM CELLS
and to diferentiate along diferent pathways. Human embryos
Ethics are moral principles that allow us to decide
consist entirely o stem cells in their early stages, but gradually
whether something is morally right or wrong. Scientists
the cells in the embryo commit themselves to a pattern o
should always consider the ethics o research and its
diferentiation. Once committed, a cell may still divide several
consequences beore doing it.
more times, but all o the cells ormed will diferentiate in the
The main argument in avour o therapeutic use o stem cells
same way and so they are no longer stem cells.
is that the health and quality o lie o patients sufering rom
Small numbers o cells persist as stem cells and are still
otherwise incurable conditions may be greatly improved.
present in the adult body. They are ound in most human
Ethical arguments against stem cell therapies depend on the
tissues, including bone marrow, skin and liver. They give
source o the stem cells. There are ew objections to the use
some human tissues considerable powers o regeneration
o an adults own stem cells or cells rom an adult volunteer.
and repair, though they do not have as great a capacity to
Newborn babies cannot give inormed consent or stem cells to
diferentiate in diferent ways as embryonic stem cells.
be harvested rom their umbilical cord, but parental consent is
Other tissues lack the stem cells needed or efective
given and the cells are stored in case they are needed during
repair brain, kidney and heart, or example. There has
the babys subsequent lie, which seems unobjectionable.
been great interest in the therapeutic use o embryonic stem
However, the ethical issues concerning stem cells taken rom
cells with organs such as these. There is great potential or
specially created embryos are more controversial. Some argue
the use o embryonic stem cells or tissue repair and or
that an embryo is a human lie even at the earliest stage and
treating a variety o degenerative conditions, or example
i the embryo dies as a result o the procedure it is immoral,
Parkinsons disease.
because a lie has been ended and benets rom therapies
using embryonic stem cells do not justiy the taking o a lie.
There are a several counter-arguments:
earlystageembryosarelittlemorethanballsofcellsthat
have yet to develop the essential eatures o a human lie
earlystageembryoslackanervoussystemsodonotfeel
pain or sufer in other ways during stem cell procedures
ifembryosareproduceddeliberately, no individual that
would otherwise have had the chance o living is denied
the chance o lie
largenumbersofembryosproducedbyIVFarenever
implanted and do not get the chance o lie; rather than
kill these embryos it is better to use stem cells rom them
Removing a stem cell rom an embryo to treat diseases and save lives.
EXAMPLES OF THERAPEUTIC STEM CELL USE
1. Stargardts macular dystrophy is a genetic disease that 2. Leukemia is a type o cancer in which abnormally
develops in children between the ages o 6 and 12. Most large numbers o white blood cells are produced in the
cases are due to a recessive mutation o a gene called bone marrow. A normal adult white blood cell count
ABCA4. This causes a membrane protein used or active is 4,00011,000 per mm3 o blood. With leukemia the
transport in retina cells to malunction, so photoreceptive count rises above 30,000 and with acute leukemia above
cells degenerate and vision becomes progressively worse. 100,000 per mm3.
The loss o vision can be severe enough or the person to Adult stem cells are used in the treatment o leukemia:
be registered as blind.
A large needle is inserted into a large bone, usually the
Researchers have developed methods or making pelvis and uid is removed rom the bone marrow.
embryonic stem cells develop into retina cells. This was
Stem cells are extracted rom this uid and are stored by
done initially with mouse cells but, in 2010, a woman in
reezing them. They are adult stem cells and only have the
her 50s with Stargardts disease was treated by having
potential or producing blood cells.
50,000 retina cells derived rom embryonic stem cells
A high dose o chemotherapy drugs is given to the patient,
injected into her eyes. The cells attached to the retina
to kill all the cancer cells in the bone marrow. The bone
and remained there during the our-month trial. There was
marrow loses its ability to produce blood cells.
an improvement in the womans vision, and no harmul
side efects. Further trials with larger numbers o patients The stem cells are then returned to the patients body. They
are needed, but ater these initial trials at least, we can re-establish themselves in the bone marrow, multiply and
be optimistic about the development o treatments or start to produce red and white blood cells. In many cases
Stargardts disease using embryonic stem cells. this procedure cures the leukemia completely.
CELL BIOLOGY 3
Light microscopes and drawing skills
USING LIGHT MICROSCOPES MAGNIFICATION CALCULATIONS
1. Treat the specimen with a stain that makes parts o the Microscopes are used to investigate the structure o cells and
cells o the specimen visible. tissues. Most microscopes use light to orm an image and can
2. Mount the specimen on a microscope slide with a cover make structures appear up to 400 times larger than their actual
slip to make it at and protect the microscope. size. Electron microscopes give much higher magnications.
3. Put the microscope slide on the stage so the specimen is The structures seen with a microscope can be recorded
below the objective lens. with a neat drawing or a photograph can be taken down
the microscope called a micrograph. An important skill
4. Plug in the microscope and switch on the power so that
in biology is calculating the magnication o a drawing or
light passes through the specimen.
micrograph. Use these instructions:
5. Focus with the low power objective lens rst.
1. Choose an obvious length, or example the maximum
6. Use the ocusing knobs to bring the slide and objective
diameter o a cell. Measure it on the drawing.
lens as close as possible without touching.
2. Measure the same length on the actual specimen.
7. Look through the eyepiece lens and move the slide and
3. I the units used or the two measurements are diferent,
objective lens apart with the coarse ocusing knob until
convert them into the same units.
the specimen comes into ocus.
One millimetre (mm) = 1,000 micrometres (m)
8. Use the ne ocusing knob to ocus on particular parts o
the specimen. 4. Divide the length on the drawing by the length on the
actual specimen. The result is the magnifcation.
9. Move the slide to bring the most interesting part o the
_siz_e o _imag_e
specimen into the centre o the eld o view. Magnication =
size o specimen
10. Turn the revolving nose piece to select the high power
Example
objective, then reocus using steps 57 again.
The scale bar on the drawing o heart muscle tissue on
11. Adjust the illumination using the diaphragm. page 2 represents a length on the specimen o 20 m
and is 10 mm long, which is 10,000 m.
eye piece
_10,0_00
Magnication = = 500
20
The magnication equation can be rearranged and used to
nose piece
calculate the actual size o a specimen i the magnication
objective lens and size o the image are known.
stage _size _o im_age
coarse focusing Size o specimen =
magnication
condenser lens knob Example
and diaphragm ne focusing knob The length o the beta cell in the pancreatic islet on page 2
is 48mm, which is 48,000 m, and the magnication o the
drawing is 4000.
lamp
_48,0_00 _m
Actual length o the cell = = 12 m
4000
SCALE BARS
A scale bar is a line added to a micrograph or a drawing to help to show the actual size o the structures. For example, a 10 m
bar shows how large a 10 m object would appear. The gure below is a scanning electron micrograph (SEM) o a lea with the
magnication and a scale bar both shown.
50 m S.I. size units
1000mm = 1 m
1000m = 1nm
1000nm = 1m
Scanning electron micrograph
o lea (x480)
4 CELL BIOLOGY
