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Biology IB revision notes TOPIC 1-TOPIC 11 RESPECTFULLY.
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Biology IB revision notes TOPIC 1-TOPIC 11 RESPECTFULLY.Biology IB revision notes
Instructions: Use bioninja.com, ibworld.me, and bioguides.com to improve these notes
Table of Contents
Topic 1: Cell Biology..............................................................................................................................3
1.1 Introduction to cells.....................................................................................................................3
1.2 Ultrastructure of cells..................................................................................................................6
1.3 Membrane structure.................................................................................................................11
1.4 Membrane transport.................................................................................................................14
1.5 The origin of cells.......................................................................................................................16
1.6 Cell division................................................................................................................................18
Topic 2: Molecular Biology.................................................................................................................22
2.1 Molecules to metabolism..........................................................................................................22
2.2 Water.........................................................................................................................................22
2.3 Carbohydrates and lipids...........................................................................................................25
2.4 Proteins.....................................................................................................................................28
2.5 Enzymes.....................................................................................................................................31
2.6 Structure of DNA and RNA.........................................................................................................33
2.7 DNA replication, transcription and translation..........................................................................34
2.8 Cell respiration...........................................................................................................................36
2.9 Photosynthesis..........................................................................................................................37
Topic 3: Genetics.................................................................................................................................39
3.1 Genes.........................................................................................................................................39
3.2 Chromosomes............................................................................................................................39
3.3 Meiosis......................................................................................................................................41
3.4 Inheritance.................................................................................................................................43
3.5 Genetic modification.................................................................................................................44
Topic 4: Ecology..................................................................................................................................47
4.1 Species, communities and ecosystems......................................................................................47
4.2 Energy flows..............................................................................................................................48
4.3 Carbon cycling...........................................................................................................................49
4.4 Climate change..........................................................................................................................50
Topic 5: Evolution and Biodiversity....................................................................................................51
5.1 Evidence for evolution...............................................................................................................51
5.2 Natural selection........................................................................................................................52
5.3 Classification of biodiversity......................................................................................................54
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,Biology IB revision notes TOPIC 1-TOPIC 11 RESPECTFULLY.
5.4 Cladistics....................................................................................................................................56
Topic 6: Human Physiology.................................................................................................................57
6.1 Digestion and absorption...........................................................................................................57
6.2 The blood system.......................................................................................................................62
6.3 Disease defences.......................................................................................................................68
6.4 Gas exchange.............................................................................................................................71
6.4 Neurons and synapses...............................................................................................................74
6.5 Hormones, homeostasis and reproduction...............................................................................80
Topic 7: Nucleic acids..........................................................................................................................88
7.1 DNA structure and replication...................................................................................................88
7.2 Transcription and gene expression............................................................................................89
7.3 Translation.................................................................................................................................90
Topic 8: Metabolism, Cell respiration and Photosynthesis................................................................93
8.1 Metabolism................................................................................................................................93
8.2 Cell respiration...........................................................................................................................93
8.3 Photosynthesis..........................................................................................................................97
Topic 9: Plant biology........................................................................................................................101
9.1 Transport in the xylem of cells.................................................................................................101
9.2 Transport in the phloem of cells..............................................................................................103
9.3 Growth in plants......................................................................................................................106
9.4 Reproduction in plants.............................................................................................................109
Topic 10: Genetics and Evolution.....................................................................................................113
10.1 Meiosis..................................................................................................................................113
10.2 Inheritance.............................................................................................................................114
10.3 Gene pools and speciation.....................................................................................................115
Topic 11: Animal Physiology.............................................................................................................118
11.1 Antibody production and vaccination....................................................................................118
11.2 Movement.............................................................................................................................122
11.3 The Kidney and osmoregulation............................................................................................127
11.4 Sexual reproduction...............................................................................................................135
Option D: Further Human Physiology...............................................................................................144
D.1 Human nutrition......................................................................................................................144
D.2 Digestion.................................................................................................................................146
D.3 Functions of the liver...............................................................................................................149
D.4 The heart.................................................................................................................................152
D.5 Hormones and metabolism.....................................................................................................155
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,Biology IB revision notes TOPIC 1-TOPIC 11 RESPECTFULLY.
D.6 Transport of respiratory gases................................................................................................158
Topic 1: Cell Biology
1.1 Introduction to cells
The cell theory-
• Every living cell is surrounded by a membrane, which separates the cell contents
from everything else outside.
• Cells contain genetic material which stores all of the instructions needed for the
cell’s activities- mostly chemical reactions
• The chemical reactions are catalysed by enzymes produced inside the cell.
• Cells have their own way of releasing the energy required for all the activities.
3 key points:
• Cells are the basic unit of life
• New cells are always formed from pre-existing cells
• Cells and cell products make up the structures of all living things
Characteristics of cells-
All cells should be able to carry out most, if not all, of the life processes:
• Nutrition- obtaining food, to provide energy and the materials needed for growth
• Metabolism- chemical reactions inside the cell, including respiration to release energy
• Growth- an irreversible increase in size
• Response- the ability to react to changes in the environment
• Excretion- getting rid of waste products of the metabolism
• Homeostasis- keeping conditions inside the organism within tolerable limits
• Reproduction- producing offspring either sexually or asexually
All cells contain DNA/RNA, they all have the ability to evolve and should maintain a constant
ecology (by adapting to their surrounding environment).
Limitations of cell size
Cells are small so that they have a greater surface area to volume ratio. Smaller cells have less
metabolic activity taking place, so they require less oxygen and will be able to work efficiently even
when conditions aren’t entirely aerobic.
The bigger the cell the more oxygen it requires, but the more difficult it is for the cell to get oxygen,
so larger cells aren’t very efficient.
Villi and red blood cells are adapted to get a large surface area. These adaptations haven’t affected
the volume.
Limitations on cell size explained:
• Reactions within cells are known as metabolism
• The metabolic rate of the cell is proportional to the volume of the cell
• Metabolism requires an intake of substances into the cell via the cell’s plasma
membrane, waste products must also be removed.
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, Biology IB revision notes TOPIC 1-TOPIC 11 RESPECTFULLY.
• So: if the surface area to volume ratio is too small then it make take too long for substances
to enter the cell and waste products will accumulate because they will build up more
quickly than they can be excreted
• If the surface area to volume ratio is too small then the cell may overheat as metabolism
will produce heat faster than it is lost out of the cell’s surface
• The bigger the cell the smaller the surface area to volume ratio
Unicellular and Multicellular organisms-
Unicellular organisms consist only of one cell and carry out all the functions of life, because of this
the structure of unicellular organisms is more complex than most cells in multicellular organisms.
As a cell grows larger its surface area to volume ratio becomes smaller. Large organisms therefore
have to be multicellular.
Being multicellular also allows the division of labour. Different groups of cells can become specialised
for different functions by the process of differentiation.
Specialised tissues can develop by cell differentiation in multicellular organisms
Multicellular organisms can have:
• Developed circulatory systems to deliver nutrients and oxygen and remove waste products
• Evolved exchange surfaces which help to achieve this
Multicellular organisms show emergent properties:
• They are organised and have an input of energy
• The abilities of the multicellular organisms will be greater than the sum of its parts-
the components of a system together have more properties than they have as
individual
elements.
• These properties emerge from the interaction of the cellular components.
Cell differentiation-
Groups of cells will differentiate from non-specialised cells that can divide to produce new cells.
Undifferentiated cells are called stem cells.
An organisms entire set of genes is its genome. In a multicellular organism each cell has a full
genome, so it has the instructions to develop into any kind of cell.
When a gene is being used in a cell, we say it’s being expressed, this means that it is actively being
used to make a protein or other gene product. Cell differentiation happens because a different
sequence of genes is expressed in different cell types.
During differentiation a cell only uses the genes it needs to follow it pathway of development. Once
a pathway of development has begun in a cell, it is usually fixed and the cell cannot switch to a
different pathway.
Stem cells-
• Stems cells have the capacity to divide and differentiate along different pathways
• Stem cells can divide again and again to produce copious quantities of new cells. They are
therefore useful for the growth of tissues or the replacement of cells that have been lost
or
damaged.
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