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IB BIOLOGY CORE

• Kerri Humphreys •

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of Science Press. ABN 98 000 073 861

© Science Press 2016First published 2016

Science PressPrivate Bag 7023 Marrickville NSW 1475 AustraliaTel: +61 2 9516 1122 Fax: +61 2 9550 [email protected] www.sciencepress.com.au

Contents

Words to Watch iv

Introduction v

Dot Points

Cell Biology vi

Molecular Biology vi

Genetics vii

Ecology vii

Evolution and Biodiversity viii

Human Physiology ix

Questions

Cell Biology 1

Molecular Biology 63

Genetics 127

Ecology 163

Evolution and Biodiversity 193

Human Physiology 225

Answers

Cell Biology 292

Molecular Biology 316

Genetics 337

Ecology 349

Evolution and Biodiversity 357

Human Physiology 367

Appendix

Index 390

Dot Point IB Biology Core iii Dot Points

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account, account for State reasons for, report on,

give an account of, narrate a series of events or

transactions.

analyse Interpret data to reach conclusions.

annotate Add brief notes to a diagram or graph.

apply Put to use in a particular situation.

assess Make a judgement about the value of

something.

calculate Find a numerical answer.

clarify Make clear or plain.

classify Arrange into classes, groups or categories.

comment Give a judgement based on a given

statement or result of a calculation.

compare Estimate, measure or note how things are

similar or different.

construct Represent or develop in graphical form.

contrast Show how things are different or opposite.

create Originate or bring into existence.

deduce Reach a conclusion from given information.

define Give the precise meaning of a word, phrase or

physical quantity.

demonstrate Show by example.

derive Manipulate a mathematical relationship(s) to

give a new equation or relationship.

describe Give a detailed account.

design Produce a plan, simulation or model.

determine Find the only possible answer.

discuss Talk or write about a topic, taking into account

different issues or ideas.

distinguish Give differences between two or more

different items.

draw Represent by means of pencil lines.

estimate Find an approximate value for an unknown

quantity.

evaluate Assess the implications and limitations.

examine Inquire into.

explain Make something clear or easy to understand.

extract Choose relevant and/or appropriate details.

extrapolate Infer from what is known.

hypothesise Suggest an explanation for a group of facts or phenomena.

identify Recognise and name.

interpret Draw meaning from.

investigate Plan, inquire into and draw conclusions about.

justify Support an argument or conclusion.

label Add labels to a diagram.

list Give a sequence of names or other brief answers.

measure Find a value for a quantity.

outline Give a brief account or summary.

plan Use strategies to develop a series of steps or processes.

predict Give an expected result.

propose Put forward a plan or suggestion for consideration or action.

recall Present remembered ideas, facts or experiences.

relate Tell or report about happenings, events or circumstances.

represent Use words, images or symbols to convey meaning.

select Choose in preference to another or others.

sequence Arrange in order.

show Give the steps in a calculation or derivation.

sketch Make a quick, rough drawing of something.

solve Work out the answer to a problem.

state Give a specific name, value or other brief answer.

suggest Put forward an idea for consideration.

summarise Give a brief statement of the main points.

synthesise Combine various elements to make a whole.

Words to Watch

Dot Point IB Biology Coreiv

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Words to Watch

What the book includes

This book provides questions and answers for each dot point in the IB Biology Core syllabus from the International Baccalaureate Diploma Programme for Biology:

• Cell Biology

• Molecular Biology

• Genetics

• Ecology

• Evolution and Biodiversity

• Human Physiology

Format of the book

The book has been formatted in the following way:

1.1 Subtopic from syllabus.

1.1.1 Assessment statement from syllabus.

1.1.1.1 First question for this assessment statement.

1.1.1.2 Second question for this assessment statement.

The number of lines provided for each answer gives an indication of how many marks the question might be worth in an examination. As a rough rule, every two lines of answer might be worth 1 mark.

How to use the book

Completing all questions will provide you with a summary of all the work you need to know from the syllabus. You may have done work in addition to this with your teacher as extension work. Obviously this is not covered, but you may need to know this additional work for your school exams.

When working through the questions, write the answers you have to look up in a different colour to those you know without having to research the work. This will provide you with a quick reference for work needing further revision.

Introduction

Dot Point IB Biology Core v

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Introduction

Verbs to Watch

Cell Biology1.1 Introduction to cells 3

1.1.1 Cell theory. 31.1.2 Organisms carry out functions of life. 51.1.3 Surface area to volume ratio. 61.1.4 Emergent properties. 91.1.5 Specialised tissues. 101.1.6 Differentiation. 111.1.7 Stem cells. 121.1.8 Applications and skills. 14

1.2 Ultrastructure of cells 21

1.2.1 Prokaryotes. 211.2.2 Eukaryotes. 251.2.3 Electron and light microscopes. 291.2.4 Applications and skills. 31

1.3 Membrane structure 34

1.3.1 Phospholipid bilayer. 341.3.2 Membrane proteins. 361.3.3 Cholesterol. 371.3.4 Applications and skills. 37

1.4 Membrane transport 38

1.4.1 Movement across the membrane. 381.4.2 Endocytosis and exocytosis. 391.4.3 Applications and skills. 40

1.5 The origin of cells 43

1.5.1 Cells from pre-existing cells. 431.5.2 Cells from non-living material. 441.5.3 Endosymbiotic theory. 501.5.4 Applications and skills. 52

1.6 Cell division 53

1.6.1 Mitosis. 531.6.2 Supercoiling. 541.6.3 Cytokinesis. 541.6.4 Interphase. 561.6.5 Cyclins. 581.6.6 Mutagens, oncogenes, metastasis. 601.6.7 Applications and skills. 61

Answers to Cell Biology 292

Molecular Biology2.1 Molecules to metabolism 65

2.1.1 Molecular biology and living processes. 652.1.2 Carbon atoms. 67

2.1.3 Carbon compounds. 682.1.4 Metabolism. 692.1.5 Anabolism. 692.1.6 Catabolism. 702.1.7 Applications and skills. 70

2.2 Water 72

2.2.1 Polar and hydrogen bonds. 722.2.2 Properties of water. 732.2.3 Hydrophilic and hydrophobic. 752.2.4 Applications and skills. 76

2.3 Carbohydrates and lipids 79

2.3.1 Monosaccharides, disaccharides, 79 polysaccharides.

2.3.2 Fatty acids. 812.3.3 Cis and trans isomers. 832.3.4 Triglycerides. 842.3.5 Applications and skills. 84

2.4 Proteins 89

2.4.1 Amino acids and polypeptides. 892.4.2 Polypeptides synthesised at 90

ribosomes.2.4.3 Range of polypeptides. 912.4.4 Genes code polypeptides. 912.4.5 Proteins and polypeptides. 922.4.6 3-D form of proteins. 922.4.7 Range of proteins. 942.4.8 Proteome. 962.4.9 Applications and skills. 96

2.5 Enzymes 99

2.5.1 Active site. 992.5.2 Catalysis and molecular motion. 992.5.3 Enzymes and pH, temperature, 100

substrate concentration.2.5.4 Denaturation. 1022.5.5 Immobilised enzymes. 1022.5.6 Applications and skills. 103

2.6 Structure of DNA and RNA 105

2.6.1 Nucleotides. 1052.6.2 DNA different to RNA. 1062.6.3 Double helix. 1062.6.4 Applications and skills. 107

2.7 DNA replication, transcription 108 and translation

2.7.1 Replication semi-conservative. 1082.7.2 Helicase. 109

Dot Points

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Dot Points

Dot Points

2.7.3 DNA polymerase. 1092.7.4 Transcription. 1102.7.5 Translation. 1112.7.6 Amino acid sequence and 111

genetic code.2.7.7 Codons. 1122.7.8 Base pairing. 1122.7.9 Applications and skills. 113

2.8 Cell respiration 114

2.8.1 Respiration releases energy. 1142.8.2 ATP in cell. 1142.8.3 Anaerobic respiration. 1162.8.4 Aerobic respiration. 1172.8.5 Applications and skills. 117

2.9 Photosynthesis 119

2.9.1 Photosynthesis definition. 1192.9.2 Visible light. 1192.9.3 Absorption by chlorophyll. 1202.9.4 Photolysis. 1202.9.5 Energy to make carbohydrates. 1212.9.6 Factors limiting photosynthesis. 1222.9.7 Applications and skills. 124

Answers to Molecular Biology 316

Genetics3.1 Genes 129

3.1.1 Gene definition. 1293.1.2 Gene locus. 1293.1.3 Alleles. 1293.1.4 Different alleles. 1303.1.5 Alleles and mutation. 1303.1.6 Genome definition. 1303.1.7 Human Genome Project. 1313.1.8 Applications and skills 132

3.2 Chromosomes 134

3.2.1 Prokaryote DNA. 1343.2.2 Plasmids. 1343.2.3 Eukaryote DNA. 1343.2.4 Eukaryote chromosomes. 1353.2.5 Homologous chromosomes. 1363.2.6 Diploid nuclei. 1363.2.7 Haploid nuclei. 1363.2.8 Chromosome number. 1363.2.9 Karyogram. 1373.2.10 Sex chromosomes and autosomes. 138

3.2.11 Applications and skills. 138

3.3 Meiosis 140

3.3.1 Meiosis and daughter cells. 1403.3.2 Chromosome number halved. 1403.3.3 DNA replication. 1403.3.4 Early stage meiosis. 1423.3.5 Homologous chromosome orientation. 1423.3.6 First division meiosis. 1423.3.7 Genetic variation. 1423.3.8 Gamete fusion and variation. 1433.3.9 Applications and skills. 143

3.4 Inheritance 146

3.4.1 Mendel. 1463.4.2 Gametes haploid. 1473.4.3 Alleles of gene separate. 1473.4.4 Zygote diploid. 1473.4.5 Dominant alleles. 1473.4.6 Genetic diseases recessive alleles. 1493.4.7 Genetic diseases sex-linked. 1503.4.8 Genetic diseases often rare. 1523.4.9 Radiation and mutagenic chemicals. 1523.4.10 Applications and skills. 153

3.5 Genetic modification and 154 biotechnology

3.5.1 Gel electrophoresis. 1543.5.2 PCR. 1543.5.3 DNA profiling. 1563.5.4 Genetic modification and 156

gene transfer.3.5.5 Clone definition. 1573.5.6 Natural cloning. 1583.5.7 Animals cloned embryo stage. 1593.5.8 Cloning methods. 1593.5.9 Applications and skills. 160

Answers to Genetics 337

Ecology4.1 Species, communities and 165

ecosystems4.1.1 Species definition. 1654.1.2 Reproductive isolation. 1654.1.3 Autotrophs and heterotrophs. 1674.1.4 Consumers. 1674.1.5 Detritivores. 1674.1.6 Saprotrophs. 167

Dot Point IB Biology Core vii Dot Points

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4.1.7 Community and populations. 1694.1.8 Community and ecosystem. 1694.1.9 Autotrophs. 1694.1.10 Nutrient cycling. 1694.1.11 Sustainability. 1704.1.12 Applications and skills. 170

4.2 Energy flow 174

4.2.1 Dependence on sunlight. 1744.2.2 Photosynthesis definition. 1744.2.3 Energy through food chains. 1744.2.4 Energy lost as heat. 1754.2.5 Living organisms and heat. 1754.2.6 Heat lost from ecosystems. 1754.2.7 Energy losses and trophic levels. 1764.2.8 Applications and skills. 178

4.3 Carbon cycling 179

4.3.1 Autotrophs convert carbon dioxide. 1794.3.2 Aquatic ecosystems carbon. 1794.3.3 Carbon dioxide into autotrophs. 1794.3.4 Carbon dioxide and respiration. 1794.3.5 Methane and methanogens. 1804.3.6 Methane oxidised. 1804.3.7 Peat formation. 1804.3.8 Formation of coal, oil, gas. 1814.3.9 Combustion and carbon dioxide. 1814.3.10 Formation of limestone. 1824.3.11 Applications and skills. 182

4.4 Climate change 184

4.4.1 Carbon dioxide and water vapour. 1844.4.2 Other greenhouse gases. 1844.4.3 Absorption of longwave radiation. 1854.4.4 Earth warmed longer wavelength 185

radiation.4.4.5 Greenhouse gases and heat 186

absorption.4.4.6 Global temperatures and climate 186

patterns.4.4.7 Industrial revolution. 1874.4.8 Combustion of fossilised organic 188

matter.4.4.9 Applications and skills. 188

Answers to Ecology 349

Evolution and Biodiversity5.1 Evidence for evolution 195

5.1.1 Evolution definition. 1955.1.2 Fossil record. 1955.1.3 Selective breeding. 1965.1.4 Homologous structures. 1975.1.5 Populations diverge. 1985.1.6 Continuous variation. 1985.1.7 Applications and skills. 199

5.2 Natural selection 201

5.2.1 Need for variation. 2015.2.2 Mutation, meiosis and sexual 201

reproduction.5.2.3 Adaptations. 2025.2.4 Overproduction offspring. 2035.2.5 Some individuals survive. 2045.2.6 Characteristics inherited. 2045.2.7 Natural selection and character 204

frequency.5.2.8 Applications and skills. 204

5.3 Classification of biodiversity 206

5.3.1 Binomial system. 2065.3.2 Naming new species. 2075.3.3 Taxonomy. 2075.3.4 Three domains. 2085.3.5 Seven levels of taxa for eukaryotes. 2115.3.6 From common ancestor. 2115.3.7 Reclassification with new evidence. 2115.3.8 Classification show shared 212

characteristics.5.3.9 Applications and skills. 213

5.4 Cladistics 219

5.4.1 Clade definition. 2195.4.2 Evidence for clade. 2195.4.3 Differences and common ancestor. 2205.4.4 Analogous and homologous traits. 2215.4.5 Cladograms definition. 2215.4.6 Cladistics and evolutionary origins. 2225.4.7 Applications and skills. 222

Answers to Evolution and Biodiversity 357

Dot Points

Dot Point IB Biology CoreviiiDot Points

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Human Physiology6.1 Digestion and absorption 227

6.1.1 Muscles in small intestine. 2276.1.2 Pancreas secretes enzyme. 2286.1.3 Digestive enzymes. 2306.1.4 Villi and surface area. 2316.1.5 Villi and absorption. 2326.1.6 Membrane transport. 2346.1.7 Applications and skills. 235

6.2 The blood system 239

6.2.1 Arteries definition. 2396.2.2 Artery muscle walls. 2396.2.3 Muscle walls maintain blood 239

pressure.6.2.4 Capillaries. 2396.2.5 Veins definition. 2396.2.6 Valves in veins. 2396.2.7 Pulmonary circulation. 2416.2.8 Initiation of heartbeat. 2436.2.9 Sinoatrial node. 2436.2.10 Signal from SA. 2446.2.11 Heart rate. 2456.2.12 Epinephrine. 2456.2.13 Applications and skills. 246

6.3 Defence against infectious 248 disease

6.3.1 Skin and mucous membranes. 2486.3.2 Skin cuts and blood clotting. 2496.3.3 Clotting factors. 2506.3.4 Fibrinogen to fibrin. 2506.3.5 Phagocytosis. 2526.3.6 Antibody production. 2526.3.7 Antibiotics. 2546.3.8 Virus and antibiotics. 2556.3.9 Applications and skills. 256

6.4 Gas exchange 260

6.4.1 Ventilation. 2606.4.2 Type I pneumocytes. 2616.4.3 Type II pneumocytes. 2626.4.4 Pathway of air into lungs. 2626.4.5 Muscles and ventilation. 2646.4.6 Different muscles for inspiration 264

and expiration.6.4.7 Applications and skills. 265

6.5 Neurons and synapses 267

6.5.1 Neuron definition. 2676.5.2 Myelination of nerve fibres. 2676.5.3 Sodium and potassium ions. 2686.5.4 Depolarisation and repolarisation. 2696.5.5 Action potential. 2696.5.6 Propagation and threshold potential. 2706.5.7 Synapse definition. 2716.5.8 Release of neurotransmitter. 2726.5.9 Threshold potential. 2736.5.10 Applications and skills. 274

6.6 Hormones, homeostasis and 275 reproduction

6.6.1 Insulin and glucagon. 2756.6.2 Thyroxine. 2786.6.3 Leptin. 2816.6.4 Melatonin. 2816.6.5 Development of testes. 2826.6.6 Testosterone. 2826.6.7 Estrogen and progesterone. 2836.6.8 Menstrual cycle. 2846.6.9 Applications and skills. 286

Answers to Human Physiology 367

Dot Points

Dot Point IB Biology Core ix Dot Points

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ContentsDot Point IB Biology Core 1

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CORE 1 Cell Biology

DOT POINT

1

Cell Biology

CORE 1

1.1 Introduction to cells.

1.1.1 According to the cell theory, living organisms are composed of cells.

1.1.1.1 State the three points of the cell theory.

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1.1.1.2 Complete the table to summarise the historical development of the cell theory.

Year Person Contribution

Zacharias Janssen

Robert Hooke

Antonie van Leeuwenhoek

Rene Henri Dutrochet

Mathias Schleiden

Theodor Schwann

Jan Evangelista Purkinje

Rudolf Virchow

Walther Flemming


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CORE 1 Cell Biology

1.1.1.3 Outline why the development of the compound microscope was essential in the formation of the cell theory.

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1.1.1.4 Outline how the development of the specific dyes assisted in the discovery of the internal structures of cells and assisted in the cell theory.

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1.1.1.5 The diagrams show the microscope used by a scientist and what he observed using this microscope.

Identify the scientist, what he was studying and explain why this evidence was important in the development of the cell theory.

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1.1.1.6 When studying unstained specimens under a light microscope, light passes through the cells and unless the cell is naturally pigmented, there is little contrast. Staining provides contrast to identify cell components. Identify one problem with staining.

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1.1.1.7 When Antonie van Leeuwenhoek (1632-1723) reported the presence of ‘little animals’ in lake water, the Royal Society asked Robert Hooke to investigate the findings. Comment on this request.

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Contents Dot Point IB Biology Core4

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CORE 1 Cell Biology

1.1.2 Organisms consisting of only one cell carry out all the functions of life in that cell.

1.1.2.1 Complete the table to summarise the functions carried out by living things/cells.

Function Description of function

Metabolism

Excretion

Growth

Reproduction

Movement

Nutrition

Homeostasis

Response to stimuli

1.1.2.2 The diagram shows a Paramecium. Identify each component and outline how that structure is involved in life processes.

A

B

C


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CORE 1 Cell Biology

1.1.3 Surface area to volume ratio is important in the limitation of cell size.

1.1.3.1 Complete the following measurement conversions.

1 centimetre (cm) = �� metres (m)

1 millimetre (mm) = �� metres (m)

1 micrometre (µm) = �� millimetres (mm) = �� metres (m)

1 nanometre (nm) = �� micrometres (µm) = �� metres (m)

1.1.3.2 The table shows a logarithmic scale from 0.1 nm to 1 m. Place each of the following on the table to show the size range of cells.

Eukaryotic cell 10 to 100 µm Hydrogen atom 0.1 nm

Prokaryotic cell 1 to 5 µm DNA double helix 2 nm diameter

Nucleus 10 to 20 µm Ribosome 25 nm

Chloroplast 2 to 10 µm Large virus (HIV) 100 nm

Mitochondrion 0.5 to 5 µm Cell membrane 7.5 nm thick

Size range of cells

10 mm 1 cm 1 m0.1 m1 mm100 mm1 mm100 nm10 nm1 nm0.1 nm

Proteins

Ribosom

es

Viruses

Electron microscope

Light microscope

Unaided eye

Sm

allest bacteria

Som

e nerveand m

usclecells

Chicken egg

Frog eggs

1.1.3.3 Use the grid to draw each of the following cells to show a comparison of the size of a bacterium (2 µm), a human red blood cell (10 µm), a cheek cell (60 µm) and a plant cell (100 µm).

100 µm ��

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80 µm ��

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60 µm ��

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40 µm ��

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20 µm ��

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CORE 1 Cell Biology

1.1.3.4 If you are given a photograph or diagram with a scale bar or information about the magnification, what equation can you use to calculate the real size of the object in the photograph or diagram?

1.1.3.5 Study each of the following diagrams and work out the real size of each.

Cell type Ciliated epithelium Palisade mesophyll Amoeba Vorticella

Diagram with scale

20 mm 20 mm 30 mm100 mm

Real sizeLength �� Length �� Length �� Length ��

Width �� Width �� Width �� Width ��

1.1.3.6 Study each of the following diagrams and work out the real size of each.

Organelle Mitochondrion Chloroplast

Diagram with scale

1 mm 1 mm

Real sizeDiameter �� Length �� Width ��

1.1.3.7 Estimate the diameter of the camilla flower and the height of the jade plant.

Diameter of camilla flower

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Height of jade plant in pot

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CORE 1 Cell Biology

1.1.3.8 Explain why cell size is dependent upon the surface area to volume ratio.

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1.1.3.9 The diagram shows three cubes with dimensions: large cube is 3 mm × 3 mm × 3 mm, medium cube is 2 mm × 2 mm × 2 mm and the small cube is 1 mm × 1 mm × 1 mm.

Assume each cube represents a living cell.

(a) Complete the following table to summarise the surface area : volume ratio (SA : V) for each cube/cell.

Cube/cell Surface area Volume Ratio SA : V Reduced ratio

Large

Medium

Small

From the table identify which cube has the largest surface area : volume ratio and explain how this relates to the size of most cells.

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1.1.3.10 The diagram shows four different shapes. Which shape would be the most efficient for a functioning cell and explain your reasoning.

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1

1

2 2

1

2

Shape D2

2

2

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1

1

Shape CShape BShape A


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CORE 1 Cell Biology


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Answers

DOT POINT

291

ANSWERS

CORE 1 Cell Biology

1.1.1.1 The cell theory states that: 1. All living things are made of cells and the products of cells. 2. All cells come from pre-existing cells. 3. The cell is the basic unit of life in which the processes of living take place.

1.1.1.2

1.1.1.3 The development of the compound light microscope provided the magnification necessary to observe cellular structures of plants, animals and unicells.

1.1.1.4 Specific dyes are used to show specific chemicals in cells and outline different structures inside cells. For example, in 1849, Hartung developed the carminic acidic procedure and in 1882 Robert Koch introduced a staining technique to show the tuberculosis bacterium. The stained cells provided evidence for the cell theory and enabled further research, e.g. observation of cells and nuclear division.

1.1.1.5 One diagram shows the microscope used by Robert Hooke and the other diagram shows his drawing of the cork he observed using that microscope. His book, Micrographia, published in 1665, has pictures of the objects he saw through his microscope, e.g. animal, vegetable and mineral. The structures in cork he named ‘cells’ and his evidence provided the basis for the cell theory.

1.1.1.6 Staining requires the cell to be preserved and ‘fixed’. This reduces the ability to observe living cells carrying out specific functions.

1.1.1.7 The report of ‘little animals’ in pond water required verification. The Royal Society needed independent confirmation of the presence of small organisms. Robert Hooke had a microscope and was a suitable person to ask to repeat van Leeuwenhoek’s experiment. Hooke observed the organisms and van Leeuwenhoek’s work was accepted.

1.1.2.1

1.1.2.2

Year Person Contribution

1590 Zacharias Janssen Invented the compound microscope with two lenses to give greater magnification.

1665 Robert Hooke Studied cork using a compound microscope and names ‘cells’.

1675 Antonie van Leeuwenhoek Observed micro-organisms.

1824 Rene Henri Dutrochet The cell is the basic unit in living bodies.

1838 Mathias Schleiden All plants are made of cells.

1839 Theodor Schwann All animals are made of cells. Created the term ‘cell theory’.

1840 Jan Evangelista Purkinje Names cellular contents ‘protoplasm’.

1858 Rudolf Virchow Proposed that cells come from pre-existing cells.

1880 Walther Flemming Described mitosis and cell division using living and stained cells.

Function Description of function

Metabolism Chemical processes within a cell where compounds are being broken down (catabolism), synthesised (anabolism) and converted from one form to another. Respiration is a process which releases energy, e.g. ATP energy is made available from the breakdown of sugars such as glucose.

Excretion Cells of living things remove unwanted products of metabolism present in excess in the cell.

Growth Living things, e.g. cells can increase in size.

Reproduction The cells of living things can divide to form new cells from the parent cell. Reproduction can be sexual or asexual.

Movement Living things show movement, e.g. internally and/or externally.

Nutrition Cells take in inorganic materials to form protoplasm and carry out the functions of living things.

Homeostasis Cells maintain a constant internal environment within narrow limits.

Response to stimuli Cells respond to external stimuli, e.g. interact with their environment.

A

B

C Vesicles, food vacuoles digest foodto provide energy for the call.Undigested contents are releasedwhen the vacuole fuses with aspecialised area of plasma membranethat acts as an anal pore.

Cilia are short appendages forlocomotion to move the parameciumthrough the water in response tostimuli or to search for food. Cilia inoral groove move food into cell mouth.

Contractile vacuole fills up with waterand uses energy to expel excesswater through the plasma membrane.


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CORE 1 Cell Biology

1.1.3.1 1 centimetre (cm) = 10−2 metres (m)

1 millimetre (mm) = 10−3 metres (m)

1 micrometre (µm) =10−3 millimetres (mm) = 10−6 metres (m)

1 nanometre (nm) = 10−3 micrometres (µm) = 10−9 metres (m)

1.1.3.2

1.1.3.3

1.1.3.4 If given a photograph/diagram with given magnification, you can use the equation:

Real size = magnified size (measured by ruler) _________________________________

magnification1.1.3.5

1.1.3.6

1.1.3.7 Diameter of camilla flower is 100 mm ± 5 mm. Height of jade plant is 1.4 metres.

1.1.3.8 Surface area to volume ratio determines the ability of a cell to exchange substances through the membrane with its environment and for the substances to reach all parts of the cell. A cell with a low surface area to volume ratio will retain heat and substances/wastes while a cell with a larger surface area to volume ratio will lose heat more quickly and diffusion will be more efficient in exchanging materials with the environment.

Size range of cells

10 mm 1 cm 1 m0.1 m1 mm100 mm1 mm100 nm10 nm1 nm0.1 nm

Proteins

Ribosom

es

Viruses

Electron microscope

Light microscope

Unaided eye

Sm

allest bacteria

Som

e nerveand m

usclecells

Chicken egg

Frog eggs

Hydrogenatom

DNACell

membrane HIV

Prokaryoticcells

Eukaryoticcells

NucleusChloroplast

Mitochondrion

0

20 mm

Human redblood cell

Plant cellBacterium Cheek cell

60 mm

40 mm

80 mm

100 mm

Cell type Ciliated epithelium Palisade mesophyll Amoeba Vorticella

Diagram with scale

20 mm 20 mm 30 mm100 mm

Real size Length – 40 µmWidth – 14 µm

Length – 68 µmWidth – 20 µm

Length/width – 550 µm ± 100 µm

Length – 420 µmWidth (top) – 200 µm

Organelle Mitochondrion Chloroplast

Diagram with scale

1 mm 1 mm

Real size Diameter 2 µm Length 4 µm Width 2 µm


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CORE 1 Cell Biology

1.1.3.9 (a)

(b) The calculations show that the smallest cube has the greatest surface area : volume ratio. This means smaller cells are more efficient in exchanging substances with their environment than larger cells. Larger cells have a larger surface area, however it will take longer for substances to move throughout the entire large cell. To remain efficient, most cells remain small, e.g. they will divide when they reach a certain size.

1.1.3.10 Shape A would be the most efficient for a functioning cell. Surface area : volume ratio for each shape is – Shape A = 6 : 1, Shape B = 3 : 1, Shape C = 5 : 1, Shape D = 4 : 1. Shape A has the largest surface area : volume ratio and is therefore the most efficient shape.

1.1.4.1 Emergent properties are properties that are found in higher biological orders where the sum of all the parts gives rise to new abilities.

1.1.4.2 An emergent property in humans is the ability to solve abstract problems. Lower biological orders have neurons to transmit signals and an anterior area that forms a brain. The architecture of the human brain enables rational thought processes, memory and abstract problem solving at a level not found in other species.

1.1.4.3 A unicellular organism carries out all the basic requirements for life, e.g. growth, reproduction and homeostasis. Multicellular organisms show emergent properties as individual cells cooperate to form tissues, tissues form organs, organs form systems and the combined systems cooperate to maintain life. The interaction and cooperation between cells, tissues, organs and systems provides multicellular organisms with abilities beyond the limitations of a single cell.

1.1.4.4 There is a hierarchical organisation from molecules, e.g. DNA molecules, to the organisation in a multicellular plant. The diagram shows the steps from molecule to cell to tissue to organ to plant. At each step there are interactions that give the next level new properties. For example, chlorophyll is a compound, in chloroplasts it is involved in photosynthesis in a cell. Photosynthetic cells are a part of leaf tissue which is also involved in gas exchange. Leaves, stems and roots are other organs that make up plants.

1.1.5.1 Differentiation is a process when cells become more specialised as they mature. They are no longer similar to the parent cell in structure or function.

1.1.5.2 The nucleus of each cell (except gametes which are haploid) contain a full set of chromosomes. Specialised cells change shape and function when specific genes are ‘switched on’. This is differential gene expression and in humans leads to around 200 different cell types.

1.1.5.3 The experiments by FC Steward showed that mature cells, which have already differentiated (e.g. into root cells in the carrot), contain the genetic information and ability to produce a complete organism. Differentiation does not involve irreversible changes to DNA.

1.1.5.4 When particular genes are ‘switched on’ they cause the cell to differentiate and become specialised. Proto-oncogenes code for proteins that regulate differentiated and cell growth. Health can be affected if the proto-oncogene becomes defective as it becomes an oncogene. Oncogenes increase the malignancy of tumour cells.

1.1.6.1 Differential gene expression occurs when different genes are expressed in cells with the same genome.

1.1.6.2 In eukaryotes DNA codes for: 1. Proteins. 2. RNA products, e.g. ribosomal RNA and transfer RNA. The rest of the DNA, which varies in amount with different species is non-coding.

1.1.6.3 New technologies have dramatically increased our ability to investigate differentiation. Improved DNA sequencing techniques and DNA microarray technologies have provided information about the coding on specific chromosomes and the genomes of many species. The growth in computing power has allowed the large databases of DNA information to be analysed and the functionality of specific genes to be determined. This has enabled molecular biologists to determine finer details about eukaryotic gene regulation and differentiation.

1.1.6.4 The quantity of a product produced by a particular gene can vary between different cells in the body of the individual, e.g. gene expression to make cholesterol. The differences in the amount of a product of gene expression can then lead to the formation of a particular tissue. The amount of product has determined the development of the cell and put it on a particular differentiation pathway.

1.1.6.5 The diagram shows a single cell that undergoes mitotic divisions to produce daughter cells. Differential gene expression occurs in the daughter cells so that one cell becomes a muscle cell, one cell becomes a neuron and another cell becomes an epithelial cell. The other cell remains undifferentiated, the same as the original parent cell.

1.1.7.1 A stem cell is a relatively unspecialised cell that can divide by cell division to produce an identical daughter cell and to differentiate to form different specialised cells.

1.1.7.2 Totipotent stem cells can give rise to any type of differentiated cell while pluripotent stem cells are able to give rise to many, but not all cell types. Young embryos contain totipotent stem cells while adult stem cells are pluripotent. Multipotent stem cells, e.g. from the umbilical cord can become a limited number of particular types of cells.

1.1.7.3 Once a cell has differentiated cell determination occurs so that even if the cell is moved to another location it will not change into the type of cell at that location. Embryonic stem cells are totipotent and can reproduce indefinitely. Depending on the conditions they can become many types of cells. If these cells are removed from the embryo, the embryo dies.

Cube/cell Surface area Volume Ratio SA : V Reduced ratio

Large 3 × 3 × 6 = 54 mm2 3 × 3 × 3 = 27 mm3 54 : 27 2 : 1

Medium 2 × 2 × 6 = 24 mm2 2 × 2 × 2 = 8 mm3 24 : 8 3 : 1

Small 1 × 1 × 6 = 6 mm2 1 × 1 × 1 = 1 mm3 6 : 1 6 : 1


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CORE 1 Cell Biology

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