Leaving Cert Biology
Study Notes
Contents
The Scientific Method ............................................................................................................................................. 2
Food ........................................................................................................................................................................ 3
The General Principles of Ecology .......................................................................................................................... 4
Cell Structure .......................................................................................................................................................... 7
Cell Continuity – Cell Cycle, Mitosis, Meiosis ......................................................................................................... 8
Cell Diversity – Tissues, Organs, Systems and Tissue Culture ................................................................................. 9
Movement of Substances ....................................................................................................................................... 9
Enzymes ................................................................................................................................................................ 10
Photosynthesis ..................................................................................................................................................... 11
Respiration ............................................................................................................................................................ 12
DNA ....................................................................................................................................................................... 14
Genetic Engineering.............................................................................................................................................. 15
Genetic Inheritance – Principles of Inheritance and Genetic Crosses .................................................................. 16
Genetic Crosses .................................................................................................................................................... 17
Evolution ............................................................................................................................................................... 20
Viruses .................................................................................................................................................................. 20
Bacteria ................................................................................................................................................................. 21
Fungi ..................................................................................................................................................................... 22
Amoeba ................................................................................................................................................................ 23
Plant Anatomy and Transport .............................................................................................................................. 24
Plant Growth Regulation and Responses – tropisms, plant hormones ................................................................ 26
Sexual Reproduction in Flowering Plants ............................................................................................................. 27
Vegetative Propagation of Flowering Plants ........................................................................................................ 29
Circulatory System ................................................................................................................................................ 30
Breathing System .................................................................................................................................................. 32
Digestive System .................................................................................................................................................. 33
Excretion, Osmoregulation and Homeostasis....................................................................................................... 34
Skeleton – bone arrangement and structure, joints, skeletal muscles ................................................................ 36
Nervous System .................................................................................................................................................... 37
Sense Organs – eye, ear, skin, .............................................................................................................................. 38
Endocrine System ................................................................................................................................................. 39
Defence System .................................................................................................................................................... 40
Human Reproduction ........................................................................................................................................... 41
MANDATORY PRACTICAL ACTIVITIES .................................................................................................................... 43
Biology Higher Notes 2018
Page | 1
M Kavanagh
The Scientific Method
A hypothesis is an educated guess to explain an observation. A hypothesis is an untested explanation.
It is unsupported by experiments. An experiment is carried out to test a hypothesis. Experiments need
to be repeated or replicated a number of times to make sure the results are correct and to make sure no
mistakes were made.
The information collected in the experiment is called data. Data can be presented in table form or
chart form. A hypothesis can develop into a theory.
A theory is an explanation of an observation supported by results of experiments.
A control is used as a comparison with the results of an experiment eg water and iodine is the control
used when testing food for starch. A placebo is a control used when testing new medicines. It is a
substance similar in appearance and taste to the test medicine but has no medication. Often called
“sugar pills”
In double blind testing neither the tester nor the patient knows what treatment is being given. This
removes bias.
The scientific method is limited by the extent of our scientific knowledge and by our ability to
interpret results. The basis of the experiment and the way it is carried out (poor expt design, low
sample numbers) can also limit the value of the scientific method. Scientists usually publish the
results and conclusions of their investigations in scientific journals.
Biology Higher Notes 2018
Page | 2
M Kavanagh
Food
Carbohydrates always contain the elements carbon, hydrogen and oxygen.
Hydrogen and oxygen are always in the ratio 2:1.
Cellulose is a structural carbohydrate in plants (it forms the cell walls).
Starch is a food storage carbohydrate in plants.
The general formula for carbohydrates is Cx(H2O)Y
Glucose is a monosaccharide (single sugar unit), its formula is C6H12O6. It provides energy.
Maltose is a disaccharide – it contains 2 monosaccharide‟s (2 glucose molecules) joined together.
Glucose and maltose are both reducing sugars as they form a red colour when heated with Benedict‟s
solution. Sucrose is a disaccharide – it is not a reducing sugar.
Polysaccharides are many monosaccharide‟s joined together.
Starch is a food storage polysaccharide formed from many glucose monosaccharides‟s joined.
Wholegrain cereal contains a high amount of fibre (cellulose) that prevents constipation.
Proteins contain the elements carbon, hydrogen, oxygen and nitrogen and sometimes phosphorous or
sulphur (all non metallic elements). The body needs protein for growth and the repair of body cells.
Proteins are made from subunits called amino acids. There are 20 common amino acids.
A chain of amino acids is folded into a 3D shape to form a protein. Globular proteins are highly
folded. Fibrous proteins show little folding.
Meat is mostly composed of the protein myosin, the biomolecules found in muscle tissue.
Keratin in nails and hair and collagen in skin are examples of structural fibrous proteins.
Enzymes (amylase) and hormones (insulin) are functional globular proteins that play a part in the
body‟s metabolism.
Lipids (fats and oils) contain the elements carbon, hydrogen and oxygen but contain a higher
hydrogen ratio than carbohydrates. Fatty foods include butter, cooking oils, cakes and crisps.
Fat is a source of energy and is needed to insulate the body and prevent heat loss.
Lipids are made up of 2 smaller biomolecules -fatty acids and glycerol.
A triglyceride is made up of 1 glycerol molecule and 3 fatty acid molecules.
Phospholipids (found in cell membranes) are made up of 1 glycerol molecule, 2 fatty acids and 1
phosphate (fats don‟t have phosphates – phospholipids do)
Fats are solid at room temperature; oils are liquid at room temperature.
Fats differ from other fats by having different fatty acids
Vitamin C (found in apples and oranges) is water soluble; A lack of vitamin C causes scurvy
(Bleeding gums) Vitamin D in milk is fat soluble. A lack of vitamin D causes rickets (weak bones)
Human cells contain between 70 -95% water. Water is a good solvent and is used to transport
substances in the blood. Water helps to keep the temperature of the body constant. It is the main
component of the cytoplasm and is the liquid in which chemical reactions occur in the cell. Water is
lost from the body by breathing out water vapour and by sweating and urination. Water maintains
turgidity in plant cells.
Metabolism is the sum of all the chemical reactions in an organism.
Catabolic reactions release energy.
Catabolic reactions break large molecules down into smaller molecules eg digestion, respiration.
Anabolic reactions build large molecules from smaller ones eg photosynthesis, protein synthesis,
making ATP. Anabolic reactions require energy.
The body needs the mineral calcium for bone formation. Milk is a good source of calcium
The body needs the mineral iron for haemoglobin in blood. Liver and spinach are good sources of iron
Trace elements are needed in small amounts by the body. Zinc, Iron and Copper are trace elements.
Magnesium is needed to make chlorophyll in plants. Calcium is needed to make the middle lamella
which binds plant cells together
Biology Higher Notes 2018
Page | 3
M Kavanagh
The General Principles of Ecology
Ecology is the study of the interaction between organisms and their environment.
Sunlight is the main source of energy in an ecosystem.
Organisms that make their own food are called autotrophs. Plants (Flora) are producers as they make
their own food. In heterotrophic nutrition organisms can‟t make their own food and must get food
from other organisms. Animals (fauna) are consumers as they feed on other organisms.
Biosphere – Everywhere on earth life is possible
Habitat – A place where organisms live
Ecosystem is the organisms interacting in their environment. Woodland and seashore are ecosystems.
Niche means the role of the organism in the ecosystem.
A Parasite obtains its food from a living host.
A Saprophyte is a decomposer such as Rhizopus fungus, it breaks down dead organic matter so that
elements can be reused.
In Symbiosis 2 different species live closely providing benefit to each other e.g. nitrogen fixing
bacteria and legumes such as clover.
Competition occurs when 2 organisms are struggling for the same resource such as food that is limited
in supply. Competition is usually very intense between organisms of the same species as they need the
same resources.
Contest competition is a struggle in which one organism wins all the resource, in scramble
competition the resource is shared. Competition and diseases limits the size of populations.
A population is the total number of individuals of a species. A population is stable when the death rate
equals the reproduction rate
Grassland food chain = Grass (producer)  Rabbit (primary consumer)Fox (secondary consumer)
Adaptations
Rabbits are adapted to the grassland ecosystem with large ears to hear predators.
Nettles are adapted with stings to keep away herbivores.
A fox is adapted to its role of a predator with eyes in the front of its head for
better focus on prey. Prey such as rabbits have eyes on the side of their head to
give a wider field of view to detect predator danger.
Trophic level is the feeding level of an organism in a food chain.
A pyramid of numbers shows the number of organisms at each trophic level
level of the food chain ie there are less rabbits than grass plants and less
foxes than rabbits. The number of trophic (feeding) levels in a food chain is
limited by the small transfer of energy from one level to the next.
Approximately 10% of the energy in a trophic level is passed along the food
chain, the rest is lost as heat produced by respiration. An inverted pyramid of
numbers starts with a single large producer such as a tree or can end with
many small consumers such as parasites.
A food web shows many food chains with links in common. In
the food web shown the oak tree is a primary producer. The
caterpillar is a herbivore as it eats only plants and the Hawk is a
carnivore as it eats only animals. The thrush is an omnivore as it
eats both plants and animals. The thrush is therefore both a
secondary and a primary consumer as it is a member of 2 food
chains.
If all the thrushes died the caterpillars would increase in number
because they would have no predator.
Biology Higher Notes 2018
Page | 4
M Kavanagh
Harmful insects could be controlled by introducing a predator that feeds on that insect eg carnivorous
mites feeding on strawberry mites which can damage strawberry crops. This is called biological
control.
A primary consumer (rabbit) feeds on a producer. A
secondary consumer (fox) feeds on a primary
consumer. The fox is a predator as it hunts and kills its
prey for food. Predator prey graphs are out of sync and
the prey peaks are higher than the predator peaks. An
increase in prey population provides more food for
predators so predator population increases. As prey
numbers decrease there is less food for predators to
their numbers also drop. There is a short delay period before a change in prey numbers directly affects
the predator population. Predators play a role in controlling the population of the prey they feed on.
If as a result of pollution, a species of plant disappears from an ecosystem then there may be a drop in
the number of herbivores that feed on that plant. There may be an increase in the numbers of other
plants that competed with it.
A biotic factor is a living factor in an ecosystem. Eg predation or competition with other organisms.
An abiotic factor is a non living factor. eg temperature, light intensity, soil pH, current speed. Edaphic
factors are abiotic factors linked to soil condition such as soil pH, permeability and mineral content.
Climate refers to long term conditions of rainfall, temperature and wind, Weather refers to short term
conditions. Aquatic factors refer to factors such as current speed in a river or the salinity (amount of
salt) of a rock pool.
A quantitative study tells the number of organisms in an area.
A qualitative study tells the types or names of organisms in an area.
Nutrient Recycling is necessary to allow other organisms to reuse elements and minerals in the
ecosystem. There is a limited amount of elements on earth and nutrient recycling allows them to be
reused when an organism dies.
In the carbon cycle photosynthesis takes carbon dioxide out of the air. Burning, respiration (including
bacterial respiration during decomposition) return carbon dioxide back to the air.
Biology Higher Notes 2018
Page | 5
M Kavanagh
In the nitrogen cycle nitrogen fixing bacteria convert atmospheric nitrogen (N2) into compounds of
nitrogen such as nitrate (NO3) which are absorbed by the roots of plants. These nitrogen fixing
bacteria can be found free in soil or in symbiosis with legumes such as peas and clover. These
nitrogen fixing bacteria live in symbiosis in root swellings of legumes such as clover. Nitrogen
compounds are passed from plants to animals during feeding. Decomposing bacteria convert the
protein in dead organic matter and excretory products such as urine into ammonia. Nitrifying bacteria
convert ammonia into nitrites and then nitrates which are absorbed by the roots of plants again.
Denitrification is when bacteria convert nitrogen compounds back into atmospheric nitrogen
maintaining constant levels of nitrogen gas in the air. Farmers often spread compounds of nitrogen
such as nitrate onto fields when crops are removed after harvesting.
Humans can impact negatively on the ecosystem by causing pollution or by not managing their waste
correctly. Pollution is any harmful addition to the environment or ecosystem e.g. burning fossil fuels
releases sulphur dioxide which dissolves in rain forming acid rain which kills trees. Alternative
sources of energy such as solar power reduces the need to burn as much fossil fuel. Continual
monitoring of the environment can detect pollution. Smell is a problem associated with waste
disposal. Many organic waste pollutants can be broken down or decomposed by microorganisms such
as in compost bins.
Slurry is an agricultural waste. It should be stored in leak proof pits and spread onto the land in dry
weather as fertiliser (source of nitrogen and other minerals for plants). If slurry is washed into rivers it
causes eutrophication (algal bloom) which is a rapid growth of microscopic plant life or alga caused
by the minerals. When these plants die they are decomposed by bacteria which use up all the oxygen
in the water. The lack of oxygen cause fish kills.
Waste disposal can be difficult because of cost, the lack of landfill sites and the danger of pollution.
Reducing the amount of packaging, recycling and reusing are ways to minimise waste.
Conservation is the wise management of the environment. Conservation is a positive impact on the
ecosystem. Conservation is important to provide food sources, to keep the balance of nature, to
maintain biodiversity, to prevent extinction of plants or animals, to provide areas for leisure
Conservation in the fisheries industry – Nets with large holes allow younger fish to escape so they can
mature and reproduce. Fishing quotas limits the amount of fish that can be taken from the sea.
Human population is affected by war, famine, contraception, natural disasters and disease.
Human population rose rapidly from mid 1800‟s because of better healthcare and medicines,
improved farming practices, improved food preservation techniques.
Biology Higher Notes 2018
Page | 6
M Kavanagh
Cell Structure
Cells can be classified as either prokaryotic or eukaryotic. Eukaryotic cells have a nucleus and other
membrane enclosed organelles such as mitochondria. Prokaryotic cells don’t eg bacteria don’t have
a nucleus or mitochondria.
The cell membrane is made from a phospho-lipid bilayer (double layer). The cell membrane controls
the entry and exit of substances to the cell. Oxygen glucose and amino acids all need to pass into a
cell and wastes such as water and carbon dioxide need to pass out. The cell membrane allows osmosis
– the movement of water - to occur.
Plant cells have cell walls made from a carbohydrate (or polysaccharide) called cellulose. The cell
wall prevents the cell from bursting when water is absorbed by osmosis. Plant cell walls are fully
permeable.
Plant cells have chloroplasts (containing chlorophyll) and large vacuoles, animal cells don‟t.
The vacuole contains cell sap made from water, sugars and salt.
An electron microscope is more powerful than an ordinary light microscope and is used to see
structures such as mitochondria and ribosomes. Mitochondria produce energy in the form of ATP
from glucose in respiration. Ribosomes make protein.
Chloroplast
Biology Higher Notes 2018
Page | 7
M Kavanagh
Cell Continuity – Cell Cycle, Mitosis, Meiosis
Tissues grow by a type of cell division called mitosis. Mitosis produces 2 identical cells - no
variation. Mitosis occurs in the root tip meristems of plants. Cancer is uncontrolled cell division by
mitosis. Cancer can be caused by radiation or smoking.
Single celled organisms use mitosis for asexual reproduction. Multicelled organisms use mitosis for
growth
Another type of cell division is called meiosis. Meiosis produces 4 non identical cells and halves the
number of chromosomes in a cell. It converts a diploid cell with 2 sets of chromosomes to a haploid
cell with 1 set of chromosomes. Meiosis is used to form gametes and results in variation.
The majority of time in the cell cycle is called Interphase. During
interphase the cell is not dividing. Organelles such as mitochondria and
chloroplasts are replicated during interphase and a store of ATP energy is
built up. DNA replication (making new DNA), protein synthesis (making
proteins from amino acids) and respiration are all processes that occur
during interphase. At the end of interphase the nuclear membrane
disappears and the chromosomes become visible as replicated condensed
threads.
Mitosis involves 4 stages- Prophase, Metaphase, Anaphase and Telophase.
During prophase the nuclear membrane breaks down and chromosomes become visible as sister
chromatids (newly replicated chromosomes still attached at centromere)
During metaphase the chromosomes lie along the centre or equator of the cell. Spindle fibres form and
attach to the centromere of each chromosome.
During anaphase the spindle fibres contract to pull the chromosomes apart to opposite poles of the
cell. During Telophase the nuclear membrane reforms around the chromosomes at each pole of the
cell and the chromosomes unravel to form chromatin.
The cell now splits in 2 with an identical nucleus in each daughter cell. In animal cells the cell
membrane pinches together – a cleavage furrow forms - this is called cleavage. In plant cells a cell
plate forms in the middle producing new cell walls and cell membranes - no cleavage furrow in
plants because of rigid cell wall.
Biology Higher Notes 2018
Page | 8
M Kavanagh
Cell Diversity – Tissues, Organs, Systems and Tissue Culture
A tissue is a group of similar cells with a common function.
The 3 types of tissue in plants are dermal, vascular and ground.
The 4 types of animal tissue are Muscle, Connective, Nervous and Epithelium.
Muscle tissue contracts and causes movement; Connective tissue contains living cells in a non living
material such as bone cells in calcium compounds. Epithelium forms skin and inner lining of
intestines. (Endothelium is a thin layer of flattened cells that line inside of blood vessels) Nervous
tissue transport nerve impulses within the body.
Tissues are specifically adapted to their function. Xylem tissue is a type of vascular tissue consisting
of long hollow tube like cells suitable to transport water. Nervous tissue consists of nerve cells with
long axons ending with synaptic knobs to transmit nerve impulses.
An organ is a group of tissues working together, A leaf is an organ in a plant. The heart is a human
organ.
A System is a group of organs working together.
Tissue culture is the growth of cells on a nutrient medium by mitosis outside the organism in a lab.
Oxygen is needed for tissue culture. Sterile conditions are needed to prevent the growth of
microorganisms. The tissue should be kept at a suitable pH and temperature. Hormones or growth
regulators can be used to stimulate the growth of tissues. Growing skin cells in a lab to transplant to
burn victims is an example of tissue culture. Growing white blood cells in the lab to produce useful
antibodies is a type of tissue culture.
Movement of Substances
Diffusion is the movement of molecules from a high concentration to low concentration. Eg the
movement of oxygen gas from the alveolus to red blood cells. Diffusion is called passive transport
because no energy is needed.
Osmosis is the movement of water through a semi-permeable membrane from a region of high water
concentrationto a region of low water concentration. Cell membranes are selectively permeable or
semi permeable as they only allow certain molecules to pass through. This allows needed substances
to be kept inside the cell.
Osmosis is a special case of diffusion as it involves the movement of water from areas of “high water
concentration” (which we call dilute or low concentrated solutions) to an area of “low water
concentration” (which we call concentrated solutions)
The entry of water from the soil into plant root hairs is by osmosis as the cell sap of root hairs is more
concentrated than the soil water.
Solutions with high sugar concentrations are used to
preserve foods such as canned fruits because the high
concentration draws water out of bacterial cells killing
them.
Turgor is the outward pressure of the cell contents on
the cell wall of plant cells because of the entry of water
to the cell vacuole by osmosis. This outward pressure
causes the cells to remain turgid supporting the plant.
Plant cells remain turgid because they take in as much
water by osmosis as they lose.
Plasmolysis is the shrinking of the cell contents from the cell wall as the plant vacuole loses water by
osmosis. This loss of turgidity causes wilting.
If animal cells are placed in distilled water (pure water) they may gain water by osmosis and burst
because they have no cell wall to prevent over expansion. Animal cells place in concentrated solutions
of salt or sugar may lose water by osmosis causing the entire cell to shrink or shrivel. (crenation)
Biology Higher Notes 2018
Page | 9
M Kavanagh
Enzymes
The body needs enzymes to control metabolism to allow reactions to occur at lower temperatures than
would normally be needed. Enzymes control processes such as respiration, photosynthesis, protein
synthesis and DNA replication. An enzyme is a protein (made from the elements N,O,C,H) that
speeds up a chemical reaction in the body without being used up. Enzymes are made up from small
building blocks called amino acids. Enzymes are made by ribosomes in the cell cytoplasm.
The lock and key theory of enzyme action - Enzymes have a 3D shape. The active site of an enzyme
is complimentary to a specific substrate. Enzymes are specific because they only attach to one
substrate that has the correct shape. The enzyme binds to the substrate forming an enzyme substrate
complex. The enzyme is unchanged when the product is formed. In the induced fit theory the active
site changes shape slightly to bind with substrates with slight variations.
Amylase is an enzyme. Its substrate (substance changed by enzyme) is the carbohydrate starch. Its
product is maltose.
An immobilised enzyme is trapped in an inert (unreactive) substance. Sodium alginate is used to
immobilise enzymes.
The advantage of an immobilised enzyme is that it can be reused and the product is easily separated.
Enzyme activity is affected by temperature and pH (how acid or base it is)
The optimum pH is the pH at which the enzyme work at its maximum rate or speed.. (for pepsin in the
stomach the optimum pH is 2)
A denatured enzyme has lost its shape and no longer functions. An Enzyme may be denatured by high
temperatures or very low pH. (Some enzymes such as pepsin can survive low pH)
Bioprocessing or biotechnology is using cells or enzymes to produce useful products such as
antibiotics. A bioreactor is a vessel in which enzymes (or microorganisms) are used to produce a
useful product. Temp, pH, food and oxygen are all controlled in a bioreactor.
Enzymes such as amylase and lipase are found in biological washing powder to breakdown biological
or food based stains. These enzymes have an optimum temperature of around 40 degrees and would
be denatured in very hot washes. Enzymes are not found in body soap because they may be harmful to
skin.
Batch cultures
Batch bioreactors carry out product formation in one step. A fixed amount of substrate and enzyme is
added to the bioreactor. The reaction is allowed to occur. The product(s) is removed before waste
products build up. The bioreactor has to be emptied, cleaned and sterilised before use again.
Continuous-flow cultures
Nutrients or substrates are continuously added into the bioreactor. The product(s) is continuously
removed.
Biology Higher Notes 2018
Page | 10
M Kavanagh
Photosynthesis
Photosynthesis is the method by which plants make their own food.An autotroph makes its own food.
Animals depend on plants for the oxygen and food made in photosynthesis.
Chlorophyll in plant cells absorbs the energy in sunlight and converts it to chemical energy.
Water and carbon dioxide are needed for photosynthesis. Carbon dioxide, needed for photosynthesis
enters the leaf through openings called stomata or can be produced inside the cell by the mitochondria
during respiration.
Photosynthesis occurs in the chloroplasts of palisade cells (just under upper epidermis) in the leaf.
6CO2 + 6H2O  C6H12O6 + 6O2
Carbon dioxide + Water →
Glucose + Oxygen
There are 2 stages in photosynthesis.
1 The light stage (light dependent stage) occurs in grana of chloroplast
2. The Dark stage (light independent stage) occurs in stroma of chloroplast
ATP (adenosine triphosphate) is a molecule that contains high
energy bonds. The energy from ATP can easily be released
when the 3rd phosphate is removed. ATP can store energy
within a cell and transfer energy to processes that need it such
as protein synthesis, DNA replication or nerve transmission..
ATP is made from ADP and Phosphate. ADP is a low energy
molecule
NADP – nicotinamide adenine dinucleotide phosphate is an electron carrier molecule. NADP is
reduced (gains electrons) to NADP- and combines with protons (H+) to form NADPH.
Light stage
In the light stage sunlight is absorbed by chlorophyll. Energised electrons are released from
chlorophyll and can follow 2 pathways.
In pathway 1 electrons leave chlorophyll and are picked up by an electron acceptor and passed along
a carrier chain, losing energy, back to chlorophyll. ATP is formed from ADP and P in this process.
In pathway 2 electrons leave chlorophyll are passed to NADP+ giving it a negative charge NADP-.
During pathway 2 water is split using light energy (photolysis) into protons (H+), electrons and
oxygen. The H+ (protons) are transferred to a proton pool where they will be used in the dark stage.
The electrons return to chlorophyll making ATP (energy) along the way as they pass along a carrier
chain. The oxygen is released into the atmosphere or may be used in respiration.
NADP- combines with protons from the proton pool to form NADPH. NADPH is used in the dark
stage reactions. NADP therefore carries protons from the light stage reactions in the grana to the dark
stage reactions in the stroma.
Light Independent or Dark stage.
The second stage is called the light independent stage or dark stage because it does not require light.
During the second stage (Dark stage) carbon dioxide is absorbed by the plant and combined with
protons to form glucose in a series of reactions called the calvin cycle.. ATP formed in the light stage
provides the energy for this. NADPH formed in the light stage provides the protons to the dark stage
reactions. The dark stage reactions are controlled by enzymes and so are affected by changes in
temperature. Dark stage reactions are anabolic as CO2 and H2O combine to form larger molecules of
glucose. In the dark stage electrons and protons are transferred from NADPH to CO2 to form glucose.
ADP and NADP+ reformed in the dark stage return to the light stage to be reused.
A gardener can increase the rate of photosynthesis by using artificial light to increase the light
intensity greater than daylight or by excess adding CO2 to increase the concentration beyond normal
atmospheric levels. Adding CO2 increases the supply of C atoms to the dark stage reactions.
Increasing the temperature increases the rate of enzyme action in the dark stage.
Biology Higher Notes 2018
Page | 11
M Kavanagh
Respiration
Aerobic Respiration is the release of energy from food using oxygen. Energy is needed to grow,
move, send nerve impulses etc. Metabolism is all the chemical reactions in the organism. Anabolic
reactions such as protein synthesis need energy.
Water and carbon dioxide are products of aerobic respiration.
Aerobic respiration produces more energy than anaerobic respiration.
C6H12O6 + 6O2  6CO2 + 6H2O
Glucose + Oxygen → Carbon dioxide + Water
Anaerobic Respiration is the release of energy from food without oxygen. Anaerobic respiration
occurs entirely in the cytosol and produces less energy than aerobic respiration.
Glucose  Alcohol +Carbon dioxide + energy..(in yeast)
or
Glucose Lactic Acid + energy..(in muscle cells)
Alcohol and carbon dioixide are products of respiration by yeast cells (used in brewing and baking).
Lactic acid is a product of anaerobic respiration in muscles.
Respiration occurs in 2 stages.
Stage 1 is called glycolysis – the glucose molecule is split into 2 smaller molecules of pyruvic acid
(pyruvate). Stage 1 of respiration occurs in the cytosol (cytoplasm without organelles) and produces a
small amount of energy (ATP). The pyruvic acid produced at the end of stage 1 is converted to lactic
acid (in muscle cells) or ethanol (in yeast) if no oxygen is present. Glycolysis is anaerobic as no
oxygen is required.
During heavy exercise the muscles may not receive enough oxygen so stage 2 of respiration is not
possible. When muscles break down glucose in the absence of oxygen lactic acid is formed. Lactic
acid builds up in the blood and forms painful cramps and must be broken down by the liver. If only
stage 1 of respiration occurs it is called anaerobic respiration.
Anaerobic respiration by micro-organisms is called fermentation. Yeast is an organism capable of
anaerobic respiration used in the fermentation of beer. Ethanol CO2 and are made when yeast ferments
glucose.
Biology Higher Notes 2018
Page | 12
M Kavanagh
Stage 2 occurs in the mitochondria and produces a large amount of energy. Stage 2 needs oxygen,
stage 1 doesn‟t. In stage 2 pyruvic acid enters the mitochondria and forms a 2 carbon molecule called
acetyl co A with the loss of a carbon dioxide molecule. This acetyl molecule enters a series of
reactions called Krebs cycle in the lumen of the mitochondria. CO2 is produced by krebs cycle in the
mitochondria. In Krebs cycle protons (H+) are released and combine with NAD to form NADH.
NADH delivers electrons to the electron transport chain on the cristae of the mitochondria..
Electrons pass along the transport chain forming ATP before returning to the hydrogen ion (proton)
and combining with oxygen to form water.
Biology Higher Notes 2018
Page | 13
M Kavanagh
DNA
DNA (Deoxyribonucleic acid) is found in the nucleus of all cells. It is also found in the chloroplasts
and mitochondria of cells. DNA contains the instructions to make protein, these instructions are called
the genetic code.
DNA has 3 parts: a phosphate group, a sugar group (deoxyribose sugar) and one of four nitrogen
bases. A nucleotide is a sugar, phosphate and base, chemically combined. It is the base that varies
from one nucleotide to the next. DNA is arranged in a double strand.
The four types of bases are: adenine (A), thymine (T), guanine (G) and cytosine (C). The bases occur
in complimentary pairs – each base has a matching base. Base pairs link by a type of bonding called
hydrogen bonding. Adenine links with Thymine, Guanine links with Cytosine.
The genetic code is the sequence of different bases in a gene. (a gene is a series of bases)
Base are classed as pyrimidines or purines.
Adenine and Guanine are the two purine bases. They are double ring molecules (remember “pure as
gold”) Cytosine and Thymine are the two pyrimidines bases. They are single ring molecules
Mitosis produces exact copies of the amount of DNA in daughter cells.
Replication occurs when 2 exact copies of DNA is made from one original strand.
The DNA strand opens or unzips and 2 new strands are made from free nucleotides in the
nucleoplasm.
RNA (Ribonucleic acid) is similar to DNA however it has the base uracil instead of thymine, It has
the sugar ribose instead of deoxyribose and it is a single strand (DNA is a double helix strand)
There are 3 types of RNA.
1.Messenger RNA (mRNA) gets its code from DNA, it is a complimentary copy of a section of DNA
made in the nucleus.
mRNA carries the instructions to make protein from the nucleus to ribosomes in the cell.
2.The ribosomes are made from ribosomal RNA (rRNA).
3.Transfer RNA (tRNA) carries amino acids to the ribosomes in protein synthesis.
Transcription occurs in the nucleus when the DNA code is copied to messenger RNA (mRNA).
The DNA molecule untwists at the site of the gene; a complimentary sequence of bases is built using
an enzyme called RNA polymerase. (polymerase joins nucleotides together – it builds up DNA or
RNA it is anabolic)
Translation occurs in the ribosomes in the cytoplasm when the RNA code is used to put amino acids
together in a particular sequence to form a peptide (small protein). A series of 3 bases is called a
Codon (or triplet). A codon can specify the start of the protein , can code for a single amino acid in the
sequence and can carry the instructions to stop the production of the protein. Each amino acids that
enter the cell is labelled with a codon of RNA called transfer RNA (tRNA). As the ribosomes read the
mRNA codons, amino acids with complimentary tRNA codons are attached to the protein molecule
being produced. The peptide is then folded into a 3D shape to form a protein,
Non coding DNA (once called Junk DNA) does not code for a protein (doesn‟t have genes)
Biology Higher Notes 2018
Page | 14
M Kavanagh
Genetic screening is checking for presence of specific gene.
If an embryo produced in in-vitro fertilisation is found to contain a harmful gene during screening
parents may decide not to implant it into the mother.
DNA profiling can be used to prove someone was at a crime scene based on matching blood or hair.
DNA profiling can also be used to prove a family relationship eg to show the biological parents of a
child. DNA profiling was used to identify traces of horse DNA in meat labelled as beef.
A DNA profile is a unique pattern of one persons DNA. There are 4 steps to creating a DNA profile.
1.Cells are broken down to release the DNA.
2.The DNA is then cut into fragments with restriction enzymes. (cut DNA at a particular point)
3.The fragments were then separated by size.
4.The pattern of fragments is analysed and compared to other samples of DNA.
Genetic Engineering
Genetic engineering is the deliberate changing or manipulation of an organisms DNA.
Genetic engineering can be used to produce bacteria that produce human insulin.
Genetic engineering can be used to produce long-life or frost resistant tomatoes, weed killer-resistant
crops, rice producing vitamin A or medicines (antibodies) from genetically modified sheep.
Main steps in genetic engineering
Cut the DNA from a donor cell (eg human insulin gene from a human cell) and cut an opening in the
DNA of the bacteria with restriction enzymes. Attach the cut DNA onto bacterial DNA with ligase
enzymes (ligation). Allow the genetically transformed bacteria to reproduce and make copies of the
inserted gene. The cloned cells produce the desired product.
Biology Higher Notes 2018
Page | 15
M Kavanagh
Genetic Inheritance – Principles of Inheritance and Genetic Crosses
The study of biological inheritance is called genetics.
Eye colour is an inherited human characteristic. Playing piano is a non inherited human characteristic.
Differences within a population are called variations.
Variations can be caused by genetic differences or by environmental differences such as diet.
Variations are caused by sexual reproduction, meiosis and mutations of genes and chromosomes.
A mutation is a change in DNA structure, change in a gene or a change in a chromosome.
Mutations are caused by chemicals, by radiation or can be spontaneous.
Sickle cell anaemia is a caused by a change to a gene.
Downs syndrome is caused by a chromosome number change (extra chromosome 21)
Chromosomes and genes are responsible for inherited human characteristics.
A chromosome is a thread like structure in the nucleus made from DNA and protein.
A haploid cell has a single set of chromosomes.
A diploid cell has 2 sets of chromosomes. If the diploid number in a cell is 46, the haploid number is
23. Gametes or sex cells are always haploid.
A gene is a section of DNA that controls the production of a protein.
Gene expression is the production of a particular protein usingthe gene’s code
A loci is the position of a gene on a chromosome.
An allele is an alternative form of a gene
A recessive allele is a weak gene that can be prevented from working by a dominant gene
A dominant allele is the allele expressed in the heterozygous condition, it prevents a recessive gene
working.
Incomplete dominance or codominance : neither allele is dominant or prevents the other working. The
heterozygous condition produces a different phenotype.
Homologous chromosomes: Pairs of chromosomes having the same allelic genes.
Multiple alleles: More than two different forms of the same gene e.g. blood grouping in man is
governed by 3 alleles A, Band O. Only two of the possible number of alleles will be in any one
organism.
Heterozygous means both alleles are different. EgTt
Homozygous means that both alleles are identical Eg TT or tt.
Phenotype is the physical appearance of the organism caused by the genes.
Genotype is the genetic makeup of an individual
There is 1 pair of sex chromosomes that determine the sex of a person. In a woman the sex
chromosomes are XX; in a man they are XY. The other 22 pairs of chromosomes are called
autosomes. However bird, butterfly and moth females are XY and their males are XX
If genes are linked they are on the same chromosome.
If genes are sex linked they are on the X chromosome. Eg haemophilia- inability to clot blood and
colour blindness – inability to tell red and green colours apart.
Males are more likely to suffer sex linked diseases as they only need
to inherit a single recessive allele from the mother whereas females
require a recessive allele from each parent to cause the disease.
Mendels first law:Law of Segregation - Traits are governed by
pairs of genes that separate at gamete formation (each gamete
receiving one gene). Segregation means separation.
Mendels second law:Law of Independent assortment - Either
member of a pair of alleles can combine with either member of another pair in gamete formation.
Linked genes do not assort independently as they are passed on to a gamete on the same chromosome.
Biology Higher Notes 2018
Page | 16
M Kavanagh
Genetic Crosses
Example 1
In humans, brown eye (B) is dominant to blue eye (b). Two parents, one heterozygous foreye colour
and the other with blue eyes, start a family.The blue eyed parent is (bb) and can produce gamete (b).
The heterozygous parent is (Bb) and can produce gametes (B), (b)
Genotypes of parents
(Bb) × (bb)
Possible gametes
(B ) (b ) × (b )
Genotypes of offspring
(Bb ), (bb )
Phenotypes of offspring
Brown eyes, Blue eyes
Note 1:1 ratio if one parent is heterozygous and one parent is homozygous recessive.
Example 2
In snapdragon plants the allele for red flower (R) is incompletely dominant to the allele for white
flower (r). Heterozygous plants have pink flowers. Give the genotypes of the parents and find the
genotypes and phenotypes of the offspring of the following cross:
Note:sometimes in this cross the allele for white can be given as (W)
Parents
Genotypes of parents
Possible gametes
Pink-flowered snapdragon x Pink-flowered snapdragon
(Rr) × (Rr)
(R ) , (r) × (R ) , (r)
Note ratio 1:2:1 red:pink:white
Example 3
The allele for brown eye (B) is dominant to the allele for blue eye (b). Use a Punnet square to find the
possible genotypes of children of parents who are both heterozygous for brown eye. State the eye
colour resulting from each of these genotypes.
Genotypes of parents
Possible gametes
(Bb) × (Bb)
(B ) , (b) × (B ) , (b)
Phenotypes:
brown and blue
Note ratio is 3:1 if both parents are heterozygous.
Biology Higher Notes 2018
Page | 17
M Kavanagh
Example 4
Use a Punnet square to show that there is a fifty percent chance that fertilization will lead to a male
and fifty percent chance that it will lead to a female
Parents
Gametes
Male (XY)
X,Y
X
X
Female (XX)
Phenotypes:
Males 50% , Females 50%
Example 5
Sex linked inheritance
In humans sex-linked genes (i.e. those on the X chromosome with no corresponding part on the Y
chromosome) include those governing red-green colour blindness, muscular dystrophy and
haemophilia (inability to clot blood).Females with both recessive genes for haemophilia do not
survive beyond the first four months.
H = normal, h = haemophilia.
Parents:
Female carrier
XHXh
X
Male normal
XHY
Gametes:
XH , X h
XH
F1
XHXH
XHY
Female
Male
Normal Normal Carrier
XHXh
XhY
Female
Male
Haemophiliac
,
Y
25% chance of producing a haemophiliac child50% chance of producing a haemophiliac son.
It is the mother that determines if the son is haemophiliac or not since the father always passes the Y
chromosome to his son.
Example 6
Dihybrid cross in linked genes do not obey memdels 2nd law of independent assortment as the genes
enter the gametes on the same chromosome.
Seeds may be yellow or green in colour. They may also be round or wrinkled in shape.
Let Y = yellow (dominant) y = green (recessive) R = Round (dominant) r - wrinkled (recessive
Parents Phenotype: Yellow & Round
(heterozygous)
Parent Genotype:
YyRr
Gametes:
YR, yr
Green & Wrinkled
(homozygous recessive)
X
yyrr
X
yr
F1 genotype:
Note ratio 1:1 same as parent phenotypes when genes are linked and one parent is double
heterozygous and the other is homozygous recessive.
Biology Higher Notes 2018
Page | 18
M Kavanagh
Example 7
Dihybrid cross when genes are not linked obey Mendel’s 2nd law as any allele can enter a gamete with
any other allele.
Leaf colour is controlled by the dominant allele G for green and g for yellow. Thorns are controlled
by another pair of alleles T thorns t no thorns located on a separate pair of chromosomes – not
linked.Describe the cross between a heterozygous green leafed thorned plant and a yellow leaf plant
with no thorn. When genes are not linked a greater variety of gametes and thereforea greater variety
of offspring are produced.
Parents Phenotype:
Parents Genotype
Green thorned
heterozygous for both)
GgTt
X
X
Gametes:
GT, Gt, gT, gt
X
(remember gametes contain one member of each allele pair)
Yellow, no thorns
(homozygous recessive)
ggtt
gt
Note that the ratio of phenotypes is 1:1:1:1 when genes are not linked and one parent is double
heterozygous and the other is homozygous recessive.
Example 8
Dihybrid cross both heterozygous , not linked
This type of croos produces 4 types of gametes for each parent producing a punnet square with 16
offspring.
The ratio of offspring will be 9:3:3:1. With 9 producing the double dominant phenotype, 1 producing
the double recessive phenotype and 3 and 3 producing recombinant phenotype of dominant recessive
traits appearing together.
Biology Higher Notes 2018
Page | 19
M Kavanagh
Evolution
Evolution is the genetic changes in populations over many generations,in response to environmental
changes, to become better adapted eventually forming new species.A species is a group of organisms
that can successfully interbreed to produce fertile offspring. Charles Darwin and Alfred Wallace were
scientists who first studied evolution
In his studies Darwin made the following observations that led to his theory of evolution.
 More offspring produced than survive to adulthood,
 There are variations in a population.
 There is competition for scarce resources.
 Natural selection occurs of best adapted organisms.
Natural selection means “Survival of the fittest” only the better adapted organisms survive to
reproduce and pass on that adaptation to the next generation. Natural selection occurs when there is
competition for scarce resources.
Organisms have variations or differences that are inherited. These variations are as a result of sexual
reproduction, meiosis in gamete formation and mutations caused by chemicals in the environment or
radiation. Some of these variations are beneficial and give the organism a better chance of
reproducing and passing on these variations
Fossils give us evidence that evolution has occured.Fossils are the remains or imprint in rock of
structures such as bones from organisms that lived millions of years ago.
Fossil bones of horses that lived millions of years ago show that horses legs were much smaller than
the more recent fossil bones. This shows how horses adapted to the changing environment from
jungle to grassland
Comparative anatomy indicates that organisms have descended from common ancestors. The arm
bones of horses, humans and dogs are all similar.
Viruses
Viruses are difficult to classify as living because they are not made of cells. They have no internal
metabolism such as respiration. They do not feed or excrete. Viruses are
obligate parasites – they must enter a living host cell to replicate.
A virus has 2 parts a protein coat called a capsid and a nucleic acid either
DNA or RNA.
Viruses can cause diseases such as Aids and Measles. The flu is caused
by a virus and has symptoms of fever, cough and sore throat.
Aids is caused by the HIV virus which attacks the body‟s immune
system leaving a person exposed to common infections which can
become life threatening. HIV is spread from person to person through
infected blood or semen during sex or by sharing needles when taking
drugs. The body does produce antibodies against HIV but these are
ineffective as the virus targets Helper T cells that play a major role in the
immune response.
Antibiotics have no effect on a virus.
A virus reproduces by replication. It attaches itself to a host cell membrane and inserts its DNA into
the host. The viral DNA controls the cell activities then uses the cell to make new virus parts and
assemble them to new viruses which burst out of the cell.
Viruses may be useful as a way of inserting DNA containing useful genes into a cell in genetic
engineering. Bacteriophages are viruses that kill bacteria.
Biology Higher Notes 2018
Page | 20
M Kavanagh
Bacteria
Bacteria are in the kingdom Monera. Bacteria are prokaryotes – they do not have membrane enclosed
organelles such as a nucleus. Human cells are eukaryotic – our cells have a nucleus.
Bacteria are useful to humans in food production eg yoghurts. Bacteria are also used to make
antibiotics and hormones such as insulin. Pathogenic bacteria cause disease. EgTB/ syphilis/ cholera/
tetanus/ sore throat/.Bacteria are grouped into different shapes - Rods, Spiral and spherical (cocci)
Some bacteria have flagella for movement and a slimy outer capsule
for protection. Bacteria have a nitrogen rich cell wall which prevents
the cell from bursting. Bacteria contain plasmids – small loops of
DNA which can easily be exchanged with other bacteria.
Plasmids are used in genetic engineering when genetically modified
plasmids with human DNA inserted are taken in by bacteria which
then start to produce human insulin.
Bacteria reproduce and split in 2 by a method called binary fission.
Bacteria that need oxygen for respiration are aerobic. Anaerobic
bacteria don‟t need oxygen.
Bacteria need food, suitable temperature and a suitable pH to grow. In unsuitable conditions the
bacterial DNA replicates and is enclosed by a thick wall forming an endospore which can remain
dormant and survive until conditions for growth return. The growth of bacteria is controlled by Temp
/ O2 / water/ food /pH /Anaerobic bacteria don‟t use oxygen
The initial slow division rate of bacteria on a new food source is
called the lag phase – the bacteria are adapting to a new food
source. The log phase is a period of rapid growth in ideal
conditions. In the stationary phase space and food become limited
and the number of new bacteria that are formed by binary fission
equals the number that die. In the decline phase there is a lack of
food and a build up of waste products and the number of bacteria
that die is greater than the number of new bacteria.
Bacteria that make their own food are autotrophic. They can be
photosynthetic (get energy from sunlight eg purple sulphur bacteria ) or chemosynthetic (get energy to
make food from chemical reactions eg nitrogen fixing bacteria)Bacteria that feed on other organisms
are heterotrophic – they can‟t make their own food. Saprophytic bacteria feed on dead organic matter
– they are important in recycling nutrients in nature. Parasitic bacteria obtain food from living hosts
and can be pathogenic (harmful). Symbiotic bacteria provide a benefit to the host organism. e.coli
bacteria in the human large intestine provide vitamin K.
Antibiotics are chemicals produced by microorganisms such as bacteria which kill or inhibit other
microorganisms. The overuse of antibiotics can lead to resistant strain of bacteria such as MRSA
developing. The rapid reproduction of bacteria allows resistant strains to develop quickly.
Bacteria are used in the food processing and bioprocessing industries to make yoghurts, food colours,
antibiotics, antibodies etc. In batch processing bacteria and nutrients are added to a bioreactor (usually
a stainless steel container in which products are made by microorganisms), allowed to grow in ideal
conditions producing a product and then everything is removed before wastes build up. Batch
processing has a definite end and allows the bioreactor to be used again, once cleaned, for a different
product. In continuous flow processing the process runs non-stop. Nutrients are constantly added and
material containing product is constantly being removed.
Sterile = free from all microorganisms, Asepsis = free from pathogens.
Biology Higher Notes 2018
Page | 21
M Kavanagh
Fungi
Rhizopus is a multicellular member of the Fungi
kingdom.Fungi are either single celled or
composed of thread like filaments called hypha.
There are 3 types of hypha in rhizopus1. Rhizoids,
2 Stolons and 3 Sporangiophores.
Rhizoids anchor the fungus onto a food source
such as bread and release enzymes onto the bread
to break it down. The rhizoids can then absorb the
nutrients from bread. Stolons grow along the
surface of the bread (the bread is the substrate)
and absorb nutrients. Sporangiophores support the
sporangia. Sporangia produce spores which are
single cells that can grow into a new fungus.
Only fungi produce spores.
All fungi cells have cell walls made from chiten not cellulose as in plants and are heterotrophs – they
can‟t make their own food. Rhizopus is an example of a fungus that is a saprophyte because it feeds
on dead organic material. This allows recycling of nutrients in nature. Decomposition is the way dead
organisms decay and rot away.
Potato blight is a parasite that absorbs food from living potato plants.
Some fungi are useful because they can produce antibiotics. Edible fungi are used as food but some
mushrooms are poisonous. Harmful fungi can cause food spoilage and diseases such as athletes foot.
In asexual reproduction sporangiophores grow upwards and form a sporangia . Haploid spores are
produced by the sporangia. The sporangia dries up, splits and the spores are released. When they land
on a substrate or food source the spores germinates to produce hypha.
In Sexual reproduction + and – strains of rhizopus
grow side by side. A bulge forms on each hypha.
Nuclei enter the bulge and form a progametangia. A
gametangia forms when a wall forms and encloses the
nuclei inside the bulge.
The gametangia fuse and nuclei fertilise each other to
form diploid zygotes (normally rhizopus is haploid).
A dormant zygospore is formed which can survive
poor growth conditions.
In suitable conditions the zygospore divides by
meiosis (back to haploid again) and germinates to
form a haploid hypha which produces a sporangia and
spores.
Yeast is a single celled fungus that reproduces
asexually by budding. Asexual reproduction is
reproduction involving 1 parent.
Budding involves mitosis which produces
identical cells with identical genes.
Examples of harmful fungi are potato blight,
athlete‟s foot, mildew, poisonous mushrooms.
Yeast is a beneficial fungi used in brewing and
baking.
Biology Higher Notes 2018
Page | 22
M Kavanagh
Amoeba
Amoeba belongs to the Protista kingdom which are mostly one celled. Amoeba is a single celled
organism that lives in ponds and damp soil, it has a nucleus so it is eukaryotic. Amoeba doesn‟t have
a cell wall It is a heterotroph – it feeds on other organisms. It surrounds its food with pseudopods and
traps it in a food vacuole. The pseudopods are for movement and surrounding prey (food)
Amoeba releases acids and enzymes into the food vacuole to break down the food and absorbs the
nutrients. Amoeba removes waste by simple diffusion.
Water enters fresh water amoeba by osmosis as the cytoplasm is more concentrated than the
surrounding fresh water..The contractile vacuole removes water from amoeba. Salt water amoeba
don‟t need contractile vacuoles because their cytoplasm is the same concentration as the surrounding
water so water doesn‟t enter the cell by osmosis.
Biology Higher Notes 2018
Page | 23
M Kavanagh
Plant Anatomy and Transport
Plant stems support the arial parts of a plant and transport water upwards from the root.Plant stems
have nodes from which leaves grow. Buds called axillary buds are found just above each node in the
angle the leaf petiole makes with the stem.
Plants have 3 main types of tissue - dermal, vascular and ground tissue. Meristem tissue is rapidly
dividing by mitosis and can be found at the shoot tip and root tip (apical meristem) Meristem tissue
divides to form the 3 types of plant tissue, Dermal, Ground and Vascular.
Dermal tissue protects the plant. Root hairs are a special type of microscopic dermal tissue that
absorbs water by osmosis. Minerals such as nitrates enter the root hair dissolved in water by active
transport which requires energy.
Ground tissue provides support for the plant and makes and stores food.
Vascular tissue transports substances within a plant. Found in veins in the leaf.
There are 2 types of vascular tissue xylem and phloem.
Xylem cells dead at maturity and are adapted to carry water by being narrow continuous tubes. They
are covered with spiral bands of lignin which give strength and support to the plant in general. Xylem
cells have holes called pits which allow sideways movement of water.
There are 2 types of xylem –vessels and tracheids
Adaptations of xylem to function - Xylem cells are hollow dead cells. Xylem vessels are long
continuous pipes while xylem tracheids are individual cells with tapered ends that overlap. Xylem has
holes called pits in the side walls to allow sideways movement of water.
Water enters the root hairs by osmosis as the water in the soil is more dilute than the contents of the
root hair cell cytoplasm. Water is partly pushed up the xylem against the force of gravity by root
pressure caused by water entering the roots by osmosis and pushing water upwards and partly by the
capillary action (upward movement) of water in narrow continuous tubes. The Water is pulled
upwards by a tension caused by transpiration of water from the leaves above. Transpiration is the loss
of water from a leaf through openings called stomata. Water continuously moves upwards to replace
the water lost by the leaf by transpiration. The upward movement of water in a plant from root to stem
to leaf is called the transpiration stream.
The column of water that is pulled upwards through the xylem doesn‟t break because of the strong
cohesive forces between water molecules. This explanation is called the transpiration pull-cohesion
theory and was developed by 2 Irish scientists Dixon and Joly.
Transpiration stops at night time (as the stomata close) so there is very little upward movement of
water in the stem at night. As water uptake increases the rate of transpiration also increases. The
highest rate of transpiration occurs on the hottest and brightest days. The stomata can close to prevent
wilting in extreme temperatures because of excess water loss by transpiration.
Biology Higher Notes 2018
Page | 24
M Kavanagh
Phloem is living tissue that carries food (sucrose) made in the leaf during photosynthesis.
Phloem cells do not have lignin. The end plates of phloem cells are called sieve plates, they have
small openings or holes which allows food to be transported from one cell to the next. Companion
cells beside sieve tubes control the sieve tube cells.
The Dicot stem TS diagram has vascular bundles in a ring. The monocot stem diagram has scattered
vascular bundles. The leaves of dicots plants have netted veins while the leaves of monocot plants
have parallel veins. The dicot root TS diagram has a central vascular bundle and root hairs.
The roots of a plant absorb water through root hairs by osmosis, they anchor the plant in the ground
and can sometimes store food (carrots).
Gas Exchange of oxygen and carbon dioxide and
water in plants occurs in the leaves through openings
called stomata and openings on the stem called
lenticels. Stomata and lenticels allow the excretion of
wastes such as CO2andwater produced in respiration
as well as O2 produced in photosynthesis..Carbon
dioxide enters the stomata by diffusion and oxygen
leaves by diffusion. The opening and closing of
stomata is controlled by guard cells. Higher carbon
dioxide levels at night cause the guard cells to close
the stomata.
The palisade mesophyll cells are close to the upper
surface of the leaf and so have a greater amount of
chloroplasts for photosynthesis than other parts of the leaf.
Plants can be monocotyledon or dicotyledon. Grass is a monocot, Dandelions are dicot.
Monocotyledons have one cotyledon food store in seed. Dicotyledons have two cotyledons
Monocotyledons have parallel venation in leaves. Dicotyledons have reticulate (netted) venation
Monocotyledons have scattered vascular bundles, Dicotyledons have vascular bundles in a ring.
Biology Higher Notes 2018
Page | 25
M Kavanagh
Plant Growth Regulation and Responses – tropisms, plant hormones
A tropism is a growth response of a plant to a stimulus.
Phototropism is a plants growth response to light. In positive phototropism the plant grows towards
the stimulus (light) in negative phototropism the plant parts such as roots grow away from light.
Plants can get more light and make more food with phototropism.
Geotropism is a plants growth response to gravity.
Plants can get more water if the roots grow down because of geotropism.
Thigmotropism is the growth response of a plant to touch. Eg ivy grows touching a wall.
In Hydrotropism the roots grow towards water.
Auxin is a growth regulator (chemical) produced by plants which controls plant responses by
stimulating growth. In high concentrations auxin can inhibit growth. Other growth regulators, such as
abscisic acid and ethene, specifically inhibit growth. Ethene is a growth regulator used as a ripening
agent for fruit.
Auxin is made in the meristem of plants just behind the growing roots tip and shoot tips and travels
through the Phloem of plants where it has an effect lower down in the plant stem. Auxins are similiar
to hormones in animals as they are chemicals made at one location and transported to another location
where they have an effect.
If a plant is exposed to light from one side then more auxin is produced along the darker side causing
cells to stretch more on the darker side than on the side exposed to light. This causes unequal growth
so the stem bends towards the light.
Certain auxins, are use as rooting powders (substances that stimulate roots to grow).24D is a type of
auxin used as a synthetic (man-made) weed-killers.
All plants have guard cells in the epidermal layer that prevent excess water loss.
Plants can protect themselves with stings and thorns.
Poison ivy produces a chemical to protect the plant from herbivores.
Plants produce heat shock proteins to protect important enzymes at high temperatures.
Biology Higher Notes 2018
Page | 26
M Kavanagh
Sexual Reproduction in Flowering Plants
There are 2 forms of plant reproduction: Sexual & Asexual reproduction. Asexual reproduction
involves 1 parent and is sometimes called vegetative propagation. Sexual reproduction involves 2
parents. The life cycle in flowering plants follows the sequence
1. germination, 2.growth, 3.pollination, 4.fertilisation ,5.seed and fruit formation, 6.dispersal
In the flower the anther produces the pollen. The carpel produces the egg. The petal attracts insects.
The sepal protects the flower as a bud. The receptacle is the swollen top of the stem just below the
carpel. Pollination is the transfer of pollen from the anther to the stigma. In self pollination the pollen
from an anther is transferred to a stigma on the same flower. In cross pollination the pollen is
transferred to a different flower. Pollen can be transferred by wind or insect. Although self pollination
is possible cross pollination between different plants allows more variation in the offspring which
increases the chance of adapting to new environments.
Wind pollinated plants (grass) have feathery stigmas, anthers outside petals, petals absent or reduced.
They produce large amounts of smooth pollen.
Insect pollinated plants (buttercups) have brightly coloured petals / anthers within petals, nectaries
(produce a sugary liqud to attract insects).The ovary contains the ovule. The ovule produces the
embryo sac which is the female equivalent of the pollen grain. He female gamete is formed in the
embryo sac.
Both male and female gametes in flowering plants are formed from “mother cells” which divide first
by meiosis and then by mitosis a number of times.A pollen grain develops from a pollen mother cell
which divides by meiosis to form 4 haploid cells (a tetrad). The nucleus of each cell divides by
mitosis to form a generative nucleus and a tube nucleus. The pollen cell forms a tough outer coat
called the exine.
Biology Higher Notes 2018
Page | 27
M Kavanagh
A pollen tube grows through the style towards the ovary. The generative nucleus in the tube divides
by mitosis to form 2 male gametes. The male gametes enter the embryo sac. Fertilisation occurs in the
embryo sac in the ovule.. The tube nucleus controls the growth of the pollen tube. Fertilisation is the
fusion of gametes to produce a zygote. Fertilisation occurs when the male gamete fuses with the
female gamete.
The pollen tube carries 2 male gametes, one fuses with the egg to form a diploid zygote, the other
fuses with the polar nuclei to form a triploid endosperm nuclei. The ovary becomes the fruit. The
zygote divides by mitosis to form the embryo.
The ovule forms the seed which contains an embryo and a food store called a cotyledon (some seeds
have a food store called an endosperm formed from the fertilised polar nuclei). The embryo has a
young shoot called a plumule and a young root called a radical. The seed coat is called the testa
(formed from the integuments around the embryo sac)
Dormancy is a period of inactivity or low metabolism when the seed does not grow. Dormancy is
caused by a plant growth regulator called absicisic acid. It allows the seed to wait until the cold, dark
winter weather has passed. Dormancy allows time for the embryo to develop and also allows time for
dispersal. Gardeners sometimes need to break dormancy in a seed by scratching the seed to damage
the testa or by placing the seeds in a fridge for a short while to mimic winter conditions.
Fruits can be fleshy such as tomatoes or dry such as acorns. Fruits are structures designed for
dispersal. Seed dispersal allows new plants to avoid competition with the parent plants for space, light
and water. .Seeds can be dispersed by wind (eg sycamore, dandelions – fruits are modified as wings),
animals (blackberries – fruit eaten and seeds egested) or self (peas).
Germination is the growth of an embryo after dormancy into a plant. During germination the radical
of the embryo becomes the root and the plumule becomes the shoot
Seeds need water, oxygen and a suitable temperature to germinate.
During germination water activates enzymes such as amylase which are produced by the embryo to
break down stored starch into sugars. The digestion of stored food such as starch makes food soluble
and available to the embryo. The sugars are used in respiration as the embryo grows. Oxygen is
needed by the embryo for respiration. A suitable temperature provides optimum conditions for the
enzymes to work.
Seedless fruits can be formed by Genetic engineering, growth regulators or selective breeding
Biology Higher Notes 2018
Page | 28
M Kavanagh
Vegetative Propagation of Flowering Plants
Vegetative propagation is asexual reproduction in plants. Vegetative propagation has one parent and
produces less variation in the next generation than sexual reproduction. Vegetative propagation
produces genetically identical plants called clones as all growth is from mitosis which produces
identical cells If the parent plant is diploid then all offspring are also diploid in vegetative
propagation.
The advantages of vegetative propagation compared to propagation by seeds- faster/ keeps good
qualities of parent. The disadvantages – lack of variation , prone to same diseases, no dispersal
leading to more overcrowding. The advantages of sexual reproduction are increased variation leading
to evolution. The disadvantages of sexual reproduction in plants are that 2 parents are required and a
more complex lifecycle often requiring external factors such as wind or insects.
Many plants have structures modified for asexual reproduction and
food storage.
Strawberries reproduce asexually by producing modified horizontal
stems called runners. A new strawberry plant grows where a node
(leaf growth point) touches the ground.
A potato is a modified underground stem called a stem tuber.
Potatoes store food overwinter for the following year‟s growth. Each potato produces a number of
new plants the following year so it is also an organ of asexual reproduction.
A bulb is a modified bud eg daffodil, onion. Onions have leaves swollen with stored food (starch). A
bud is an area of new growth.
A root tuber is the name given to modified a root eg dahlia.
Artificial propagation is a form of artificial asexual reproduction that is used to quickly get new plants
and maintain desirable traits such as colour or taste.eg Grafting/cutting/layering/micro-propagation.
Biology Higher Notes 2018
Page | 29
M Kavanagh
Circulatory System
The liquid part of blood is called plasma. Plasma contains water and dissolved food such as sugar and
salt. Plasma transports substances around the body and distributes heat.
There are 3 types of blood cells, 1. Red blood cells carry oxygen, 2.White blood fight infection,
3.Platelets clot the blood. Red blood cells contain haemoglobin for carrying oxygen.
The ABO blood group system has four blood groups Type A, Type B, Type AB, Type O.
The rhesus system groups blood in positive and negative.
Knowing a person‟s blood type allows compatible blood to be given in a transfusion.
Blood cells are made in the bone marrow.
Red blood cells have no nucleus (so they don‟t divide), they are biconcave in shape and they contain
haemoglobin.
Smoking, fatty foods and lack of exercise have a harmful effect on our circulatory system.
The body has 2 blood circuits – the systemic system carries blood from the heart to and from the
body, the pulmonary system carries blood to and from the lungs.
Arteries have thick walls, small lumens (centre) and carry blood away from heart. They don‟t have
valves because the blood is under high pressure.
Veins have thin walls, large lumens (centre) and carry blood towards the heart. They have valves to
prevent the backflow of blood.. Blood is kept moving through veins by the contraction of surrounding
skeleton muscles. Carbon dioxide levels are usually higher in venous blood than in arterial blood as
venous blood has collected carbon dioxide produced by respiration from body cells
Capillaries have small lumens and very thin walls one cell thick for the easy diffusion of food, oxygen
and carbon dioxide to and from body cells. They don‟t have valves. The thin walls allow food and
oxygen to diffuse from the blood to body cells.
Valve
A portal vein has capillaries at each end and does not connect to heart. The hepatic portal vein
connects the small intestine to the liver.
The renal artery carries blood from the aorta to the kidneys. The renal vein carries blood from kidney
to vena cave. The hepatic artery and hepatic vein connect to liver.
The heart is located in the chest (thorax) protected by the ribcage. The heart beats about 72 beats per
minute on average. Heavy exercise and certain chemicals (caffeine) make the heart beat faster. Blood
low in oxygen enters the heart through the vena cava.The right ventricle pumps blood to the lungs in
the pulmonary artery.. Blood from the lungs high in oxygen returns to the heart through the
pulmonary vein and leaves the heart through the aorta to travel all around the body. Blood in the
pulmonary vein is low in carbon dioxide as it has been removed by the lungs. The wall of the left
ventricle is thicker as it has to pump blood all around the body.
Biology Higher Notes 2018
Page | 30
M Kavanagh
The bicuspid and tricuspid valves prevent blood flowing from ventricles back to atria. The semi lunar
valves prevent blood flowing from arteries back to ventricles.
The coronary artery on the surface of the heart carries blood to the cells of the heart provides the heart
muscle with oxygen. The coronary vein carries blood from the tissues of the heart back to the right
atrium directly.
Branches of the aorta supply different organs of the body: the renal artery supplies the kidney.
The heart is made up of contractile muscle tissue that can shorten or contract when stimulated. The
SA node (pacemaker) regulates heart beat and is found in the right atrium. The AV node is found in
the septum between the ventricles.
Blood pressure is caused by the blood being pushed into arteries by the contraction of the heart.
Lymph
Blood plasma containing food and oxygen leaks from capillaries to surround body cells. It is then
called extra cellular fluid or tissue fluid. Tissue fluid allows an exchange of substances with body
cells. Some tissue fluid is collected by capillaries again and carried to venules and some is collected
by the lymphatic system. The lymphatic system is a system of tubes that return tissue fluid to the
blood stream and also transports fats from the small intestine. The lymphatic system is where white
blood cells called lymphocytes mature and fight infection. Lymph vessels have valves to prevent
back flow of lymph. Lymph has no blood cells or clotting proteins and has a higher level of fat than
blood. Lymph vessels have swellings called nodes where lymph is filtered and pathogens are removed
by white blood cells.
Biology Higher Notes 2018
Page | 31
M Kavanagh
Breathing System
Breathing is the inhalation of gas into the lungs for gas exchange and the exhalation of waste gases.
Respiration is the breakdown of glucose releasing energy
Cilia are tiny hairs in the nasal passage and trachea. The cilia moves back and forth and produce a
mucus which traps dust. Movement of the cilia carry the dust particles to the throat to be swallowed.
Air passes through the larynx (voice box), trachea, bronchus, and bronchioli to the alveoli. Rings of
cartilage around the trachea prevent it from collapsing.
Gas exchange is the swapping of carbon dioxide and water for oxygen and occurs in the alveoli. The
alveoli are adapted to gas exchange by having thin walls / moist surfaces / surrounded by capillaries/
large surface area.
The pulmonary artery carries blood low in oxygen and high in carbon dioxide to the lungs. The
pulmonary vein carries blood rich in oxygen and low in carbon dioxide back to the heart.
Be able to draw a labelled diagram of the human breathing tract including trachea, bronchus
and bronchioles and alveoli.
The larynx makes sound : it is the voice box. The epiglottis is a flap of tissue at the top of the trachea
that closes when swallowing to prevent food entering the trachea.
The Medulla oblongata in the brain registers blood CO2levelsMore CO2results in faster breathing.
Less CO2results in slower (breathing)
During inhalation (breathing in) high levels of carbon dioxide concentration in the blood is detected
by the brain, an impulse is sent from the brain causing the intercostal muscles (between the ribs) and
diaphragm (below the lungs) to contract. The rib cage moves up and out and the diaphragm flattens.
The volume of the thoracic cavity increases. Pressure drops in the thoracic cavity and air is sucked in
to the lungs.
Asthma is a disorder of the human breathing system. Asthma can be caused by allergens in the air
such as dust mites that cause the bronchioles to constrict. It can be treated with an inhaler. Asthma can
be avoided by removing sources of allergens by replacing dusty carpets with wooden floors or by
removing carpets.
Biology Higher Notes 2018
Page | 32
M Kavanagh
Digestive System
Digestion is the breakdown of food into smaller molecules. Digestion is needed so that molecules are
small enough to enter blood and enter body cells.
A „balanced‟ diet contains all the food types in correct proportions.
Mechanical digestion (physical) is the crushing of food by teeth and peristalsis in the stomach.
Chemical digestion is the breakdown of food using chemicals such as the breakdown of starch by
amylase produced by the salivary glands in the mouth.
The dental formula (arrangement of teeth) for humans is i 2/2, c 1/1,pm 2/2, m 3/3
Incisor teeth cut food, Canines tear food, Premolars and molars crush and grind food.
Peristalsis is muscular contractions/in the walls of the alimentary canal to move food along and helps
in mechanical digestion. Food is churned in the
stomach into chyme and protein is broken down.
Hydrochloric acid (pH 2) made in the stomach
kills bacteria and activates pepsinogen (an
inactive enzyme that becomes pepsin). Partially
digested food leaves the stomach and enters the
duodenum. The liver makes bile which is
secreted into the duodenum. Bile neutralises
stomach acid and breaks fats up into small
droplets (emulsify the fats). The approx pH of the
duodenum is pH 7. The gall bladder stores bile.
The pancreas secretes enzymes into the
duodenum such as amylase enzyme to break
starch into maltose and lipase enzyme to break
fats into fatty acids and glycerol and protease
enzyme to break proteins down to amino acids. The
pancreas has a non digestive function also – it makes the
hormone insulin to control blood glucose levels.
Small finger like projections in the ileum are called villi.
They increase surface area to absorb food. The lacteal
inside the villi absorbs fat and the capillary network
absorbs molecules such as monosaccharide‟s (glucose)
and amino acids. The capillary network and thin walls
are adaptations for the absorption of nutrients.
The digested food then goes to the liver in the hepatic
portal vein. A portal vein has capillaries at both end and
connects 2 organs together instead of to the heart. The
liver breaks down excess protein (deamination) and
breaks down poisons such as alcohol.
Digested food leaves the small intestine and passes into
the blood by diffusion.
The passage of digested food from the intestine to the blood is called absorption.
Symbiotic bacteria provide us with benefit – they live in the large intestine and produce vitamin K
and compete against harmful bacteria.
The large intestine absorbs water and the rectum stores the solid waste.
Dietary fibre found in wholegrain foods, vegetables and cereals stimulates peristalsis and prevents
constipation- it keeps food moving through the alimentary canal and reduces the chance of bowel
cancer. Water is reabsorbed back into the bloodstream in the large intestine. Egestion is the removal
of unabsorbed material through the anus.
Biology Higher Notes 2018
Page | 33
M Kavanagh
Excretion, Osmoregulation and Homeostasis
Homeostasis means maintaining constant internal environment such as a constant temperature, blood
pH, tissue fluid concentration or blood glucose level. Homeostasis is important to allow normal
metabolic activity to occur and to provide optimum conditions for enzymes to work. An endotherm is
an organism that produces heat internally by metabolic activity such as respiration. Endotherms can
significantly vary their metabolic activity to maintain a constant
body temperature. An increase in metabolic activity leads to a
rise in temperature of the organism (this needs increased food
intake).
In the graph the dogs temperature remains constant in order to
maintain optimum conditions for enzyme activity. An ectotherm
(eg snake or lizard ) cannot directly control its body temperature
and depends on the environment to cool down or warm up. The
lizards temperature goes up as the environmental temperature
increases and goes down as the environmental temperature
drops. Lizards need to hibernate in low temperatures to allow
the body metabolism to slow down or can use heat from the sun to warm up when necessary.
Excretion is getting rid of wastes of metabolism from the body. Every cell in the body produces CO2
and H2O as waste products of respiration and urea is a waste product of the breakdown of excess
amino acids by the liver (deamination). The kidneys have 2 functions excretion and osmoregulation.
The kidney removes excess water when the blood becomes too dilute. Osmoregulation means
balancing salt or water concentration of the blood.
The kidneys are located in the abdomen in the small of the back. They excrete urine which contains
water, salt and urea (a product of the breakdown of excess proteins in the liver). The lungs excretes
carbon dioxide and water vapour. The skin excretes sweat which contains water and salt. The kidney
is an exocrine gland as it has a duct – the ureter.
The renal artery carries blood high in water and waste from the aorta into the kidney. The kidney
filters out urea, salt and excess water. The renal vein carries blood low in urea, salt and water from the
kidney to the vena cava. The ureter carries urine to the bladder. The cortex of the kidney filters the
blood. The cortex and medulla of the kidney reabsorbs useful substances back into the blood.
Biology Higher Notes 2018
Page | 34
M Kavanagh
The kidney contains many small filtering units called nephrons which remove waste from the blood.
Blood containing wastes enter each kidney through the renal artery (which comes from the aorta) and
travels to the nephron by the afferent artiole. The afferent artiole supplies blood to a ball of capillaries
called the glomerulus located in bowmans capsule of the nephron. Bowmans capsule is located in the
cortex. Filtration occurs in bowmans capsule in the cortex. Blood is under pressure in the glomerulus
due to pressure from the heart and the narrower exiting efferent arteriole.
The liquid part of blood (plasma) containing water, salt, sugars, amino acids and wastes such as urea
are filtered from the glomerulus through the thin wall of bowmans capsule into the lumen (centre) of
the nephron to form the glomerular filtrate. Blood cells and large proteins such as blood clotting
proteins are too large to be filtered and are normally absent from urine. The thin wall of bowmans
capsule and the pressurised blood of the glomerulus are features that enable efficient filtration. Useful
products such as water glucose and amino acids are absorbed from the proximal convoluted tubule
into the capillary network. Glucose is absent from urine as it is reabsorbed back into the blood from
the proximal tubule (in cortex.
Water is reabsorbed back into the blood in the descending loop of henle (in medulla). Reabsorbtion
therefore occurs in the cortex and medulla. Salt is removed from the loop of henle into the tissues of
the medulla creating an area of high concentration which draws water out of the collecting duct in the
presence of ADH. Potassium ions are secreted from the capillary network into the distal convoluted
tubule to regulate the bloods pH.
The liquid that remains in the collecting duct is urine and contains water, salt, urea and secretions
such as potassium ions. The body regulates the water concentration of the blood by fine tuning the
amount of water that remains in the collecting duct. The pituitary gland at the base of the brain
secretes the hormone ADH as a response to high water levels when water needs to be conserved (after
sweating during exercise or after a salty meal)). ADH travels to the kidney in the blood. ADH opens
pores in the collecting ducts and allows water to be reabsorbed back into the blood by osmosis
because of the concentration difference between the medulla (where the capillaries are located) and
the collecting duct. High levels of ADH produce a smaller volume of more concentrated urine. The
urine travels from the collecting duct to the pelvis of the kidney, then to the ureter and to the bladder.
Urine leaves the bladder by the urethra.
Biology Higher Notes 2018
Page | 35
M Kavanagh
Skeleton – bone arrangement and structure, joints, skeletal muscles
The skeleton supports and protects the body. The skeleton allows movement.
The vertebrae protect the spinal cord which runs through it. The axial skeleton consists of the skull,
vertebrae, pelvis and shoulder blade and collar bone. The 7 cervical vertebra are in the neck, the 12
thoracic vertebra hold the ribs in the upper back, the 5 lumbar vertebra are in the lower back and the
the sacral vertebra are at the hips. Bone marrow is found in the medullary cavity of long bones.
Yellow bone marrow acts as a store of fat, red bone marrow produces blood cells.
Bone cells called osteoblasts build bone. Osteoclasts dissolve or remove excess bone. Continued
renewal of bone depends on calcium in the diet, age, gender and exercise.
A joint is where 2 bones meet. The elbow and knee are examples of
hinge joints; the hip and shoulder are ball and socket joints. Cartilage
prevents bones rubbing against each other causing pain. Discs of
cartilage are found in between the vertebrae and act as shock absorbers.
Synovial fluid lubricates the joint.
Tendons attach bone to muscle, Ligaments attach bone to bone.
Antagonistic muscles work opposite each other in pairs.eg the biceps
contracts to raise the lower arm. The triceps contracts to lower the lower
arm. As one contracts the other must relax.
Arthritis is inflammation or swelling that affects the joints and can limit movement of the joint and
cause pain. It can be caused by wear and tear of the joint during manual work or can be caused if the
white blood cells of the body attack the cartilage of the joint. It can be treated with anti-inflammatory
painkillers and artificial joint replacement.
Biology Higher Notes 2018
Page | 36
M Kavanagh
Nervous System
The nervous system is faster than the endocrine (hormonal) system. The effects of a nervous response
is short lived and localised, the effect of a hormonal response is long lived and widespread.
Two main parts of the central nervous system in humans are the brain and spinal cord. The other
nerves in the body (in the arms and legs) are part of the peripheral nervous system. There are 3 types
of nerve cells or neurons. 1.Motor Neuron, 2.Sensory Neuron, 3. Interneuron.
A motor neuron carries impulses from the CNS to muscles (or effectors)
Sensory carry impulses to the CNS from sense organs (or receptors)
Interneurons are found in the CNS they connect motor and sensory neurons.
Dendrites receive nerve impulses from another neuron or receptor. The axon of the neuron carries
nerve impulses from the cell body. Schwann cells found along the axon of a neuron make a fatty
substance called myelin which insulates the axon and speeds up nerve impulses. The gap between one
neuron and the next is the synapse.
The small gap between neurons is called a synaptic
cleft. Vessicles in the synaptic knobs release
neurotransmitter into the synaptic cleft (gap). The
neurotransmitters cross the gap and bind with receptor
sites on the next neuron to generate an electrical
impulse. The movement of ions into nerve cells
stimulates nerve impulses.
The neurotransmitters are then either reabsorbed
by the neuron or broken down by enzymes.
Dopamine is an example of a neurotransmitter.
Reflex actions react quickly and protect the body from damage by sudden dangers. A reflex action is
not under conscious control of the brain it is an
automatic response to a stimulus. In a spinal reflex the
spinal cord passes an impulse directly from a motor
neuron to a sensory neuron through an interneuron.
Pulling your hand away from a hot object is a reflex
action.
The cerebrum of the brain is the forebrain located at the
front it controls speech, emotion, language, vision and
memory. The cerebellum is the hind brain at the back
and controls voluntary muscle activity. The
hypothalamus regulates temperature. The medulla
oblongata controls involuntary muscles such as breathing. In the CNS grey matter contains mostly cell
bodies of neurons and white matter contains mostly axons of neurons.
Parkinsons is a disorder of the nervous system. It occurs when the brain stops making a
neurotransmitter called dopamine. It is treated with physiotherapy, electro therapy (DBS) and drugs
such as levodopa.
Biology Higher Notes 2018
Page | 37
M Kavanagh
Sense Organs – eye, ear, skin,
The cornea is transparent to allow light into the eye and has a curved surface which along with the
lens helps to focus light onto the retina. The lens is transparent, curved and can change shape. The
coloured part of the eye is the iris; it controls the amount of light entering the eye through the pupil by
changing the diameter of the pupil. The retina detects light and generates nerve impulses. The retina
has cones to detect coloured bright light and rods
to detect dim light.
The optic nerve carries impulses to the brain.
The suspensory ligaments hold the lens in
position. The ciliary muscle contracts to change
the shape of the lens to view close objects. The
suspensory ligaments relax and the lens becomes
more convex or round to view close objects.
To view distant objects the ciliary muscle relaxes
and the suspensory ligaments contract to make
the lens slimmer and less convex. The changes in
the shape of the lens is called accommodation.
The skin acts as a sense organ, protects against infection and
makes melanin to protect against UV radiation . The skin
helps to maintain a constant temperature. In cold conditions
erector muscles in the skin contract and cause the hairs to
stand up – this is called piloerection - and traps air to insulate
against heat loss. Arteriole blood vessels (small arteries in the
skin) constrict or narrow reducing blood flow close to the
skin and so reducing heat loss from the blood. This narrowing
of arterioles in the skin is called vasoconstriction.
In hot conditions the skin excretes sweat from sweat glands –
sweat is an excretory product and also helps to cool the body
down. Arterioles expand or dilate allowing blood flow close
to skin surface to lose heat. Erector muscles relax and hairs
lie flat against the skin.
.
The ear is divided into the outer ear (pinna, auditory
canal and eardrum), the middle ear and the inner ear.
The pinna collects sound and directs it towards the
eardrum. The middle ear contains air and the inner ear
contains a type of lymph fluid.The ossicles are 3 small
bones in the middle ear, the hammer, anvil and stirrup,
that pass and magnify sound vibrations from the
eardrum to the inner ear. The cochlea in the inner ear
converts these vibrations to nerve impulses for hearing.
The semicircular canals in the inner ear control
balance. The semicircular canals consist of 3 tubes
filled with fluid at 90 degrees to each other which
control balance in 3 planes.
The Eustachian tube connects the air in the middle ear
to the throat to equalise air pressure between the middle ear and the outer ear. Glue ear is a disorder of
the ear caused by a build up of fluid in the middle ear. It is treated with grommets. (small plastic tube
in eardrum) which allows excess fluid to drain away.
Biology Higher Notes 2018
Page | 38
M Kavanagh
Endocrine System
A hormone is a chemical messenger produced by endocrine glands which is carried by the blood to
other parts of the body where it has an effect. Endocrine glands are “ductless glands” as they secrete
hormones directly into the blood.
The pancreas is both an exocrine and endocrine
gland as it has a pancreatic duct to secrete
enzymes (exocrine function) and islets of
langerhans to secrete insulin hormone (endocrine
function).
Hormones are chemical in nature and slower
than the electrical nerve impulses passed by the
nervous system. Hormones have a wider target
area and a longer lasting effect.
Adrenaline is a hormone produced by the adrenal
glands which can make the heart beat faster; it
prepares the body for fight or flight. Insulin is a
hormone made in the pancreas. It allows body
cells to absorb glucose. A lack of insulin causes
diabetes.
The thyroid gland produces thyroxine hormone to regulate the body‟s metabolism. A deficiency of
thyroxine causes tiredness and weight gain. It can be caused by a lack of iodine in the diet. It is treated
with with iodine tablets or injections of manufactured thyroxine hormone.
An overactive thyroid gland – hyperthyroidism - produces excess thyroxine causing Graves Disease nervousness, increased heart rate, difficulty sleeping and weight loss. It can be treated with surgery to
remove part of the thyroid or by using radioactive iodine to kill parts of the thyroid gland.
Low levels of thyroxin cause the pituitary gland to produce thyroid stimulating hormone which in turn
cause the thyroid gland to make more thyroxin. The higher levels of thyroxin then inhibit the pituitary
gland from making TSH which in turn switches off thyroxine production in the thyroid gland. This is
an example of a feedback mechanism where the high level of one hormone negatively effects the
secretion of another hormone.
Hormone supplements are medical doses of hormones to replace hormones that the body doesn‟t
make. Eg insulin can be injected by diabetics.
Biology Higher Notes 2018
Page | 39
M Kavanagh
Defence System
Immunity is the body‟s defence against disease. The skin acts as a barrier to keep out harmful
bacteria, The skin can form scabs over cuts to prevent bacteria entering. Platelets clot the blood to
form scabs. Sebaceous glands in the skin produce an oil called sebum which prevents the skin from
cracking. Stomach acid kills bacteria. Mucus made by tiny cells in the throat trap bacteria.
All white blood cells are made in the bone marrow.There are 2 main types of white blood cells
Monocytes and Lymphocytes. Monocytes leave the bone marrow when mature. They can engulf or
eat bacteria. A macrophage is an example of a monocyte.
Lymphocytes leave bone marrow early and mature in the lymph system. Lymphocytes can be B cells
or T Cells. Plasma B Cells make antibodies against foreign cells such as bacteria. Antibodies are
proteins produced by the body in response to an invading cell or infection. Antibodies attach to
Antigens on the bacteria surface causing them to clump together. Bacteria that are clumped together
cannot infect cells and are easily destroyed by monocytes. Some B cells become memory cells which
can quickly turn into plasma B cells if an infection returns.
There are 4 types of T cells.
 Killer T cells which destroy infected cells.
 Helper T cells which recognise antigens and activate killer T cells. They stimulate B cells to
produce antibodies.
 Suppressor T cells which turn off the immune response when the infection is defeated and
 Memory T cells which can remember antigens and react quickly if the infection returns.
In active immunity the person with the infection makes antibodies – long lasting effect.
In passive immunity antibodies are transferred from another organism into the infected person – short
lived effect.Breast milk provides antibodies from the mother to the baby so is a form of natural
passive immunity.An injection of antibodies as in the case of a Tetanus injection is a form of artificial
passive immunity. This type of injection is given when the patient is unable to make antibodies or
there is not enough time to do so.
A vaccination is a non disease causing dose of a pathogen causing antibody production to protect
against infection. Vaccinations lead to active immunity as the person makes antibodies to defend his
own body. Older people have a greater amount of antibodies and memory lymphocytes in their blood
than younger people as they have been exposed to many different antigens in their lifetime. This
means older people are often immune to infections that recur in the community.
A person is more likely to pick up infections in hospital as there are antibiotic resistant strains there,
there are more pathogens in a hospital, more people and patients in a hospital may have an already
weakened immune system.
Biology Higher Notes 2018
Page | 40
M Kavanagh
Human Reproduction
The male gamete, the sperm is produced by meiosis
in the testes. The midpiece of the sperm provides
energy – it has many mitochondria. The nucleus of
the sperm contains the haploid number of
chromosomes (23).Sperm is stored in the
epididymis and carried to the urethra by the sperm
duct.
The seminal vesicle and prostate gland provide a fluid to the sperm to allow them to swim and
provides them with food. The sperm and seminal fluid form semen which leaves the body in the
urethra through the penis. Testosterone (made in testes) is the main male sex hormone that causes
males to produce sperm. Males and females become sexually mature at puberty. Secondary sexual
characteristics are features that distinguish the sexes apart from the sex organs essential for
reproduction. Testosterone causes secondary sexual characteristics such as deep voice, wide
shoulders, more body hair, more muscle.
The female gamete the egg is produced by meiosis in the ovary. The ovary also produces oestrogen
which causes the development of secondary sexual characteristics in girls such as widening of the hips
and development of breasts.
The menstrual cycle is the monthly 28 day cycle in female.
Days 1-5 The lining of uterus (endometrium) breaks down and blood is lost through the vagina.
Menstruation is the loss of the lining of the womb through the vagina.
Days 6 – 13 the hormone oestrogen repairs the womb wall and stimulates release of LH.
Day 14 the hormone LH (made in pituitary) causes ovulation when an egg is released.
Days 15-28 the womb lining is maintained by the hormone progesterone, if no fertilisation occurs
then the womb lining breaks down at the end of the cycle.
FSH is made in the pituitary gland, it stimulates immature eggs in ovary to develop into graffian
follicles. Oestrogen, made by graffian follicle repairs womb lining -. Oestrogen levels are higher in
the first half of the menstrual cycle. After ovulation the graffian follicle becomes the corpus luteum.
Progesterone, made by corpus luteum maintains womb lining -. Progesterone levels are higher in the
second half of the menstrual cycle and inhibit LH and FSH.
After sexual intercourse the sperm can survive for 3 days in the woman‟s body. The egg can survive
for 2 days after ovulation. The fertile period is the time when a woman may become pregnant (day 11
– 16 approx).
Biology Higher Notes 2018
Page | 41
M Kavanagh
Fertilisation is the union of the male and female gamete to form a zygote. Fertilisation occurs in the
fallopian tube. The zygote forms and divides by mitosis to form a solid ball of cells, the morula and
then a hollow ball of cells called the blastocyst. Implantation occurs when the blastocyst attaches to
the lining of the womb, the endometrium.
Cells from mother‟s womb lining and cells from embryo form the placenta. The placenta allows
oxygen to move from mother‟s blood to embryos blood and allows wastes to move from embryos
blood to mothers. It also makes progesterone to maintain womb lining.
A germ layer is a layer of cells in the embryo from which different body systems develop
The 3 germ layers are ectoderm, mesoderm and endoderm. The ectoderm forms the skin and nervous
system. The mesoderm develops into the digestive system and skeleton. The endoderm forms the
lining of the digestive system.
Fibroids are non cancerous growths in the uterus caused by a hormonal imbalance. Large fibroids are
removed by surgery.
The amnion is a membrane around foetus (embryo) it secretes amniotic fluid to cushion / protect the
embryo. The baby is connected to the placenta by the umbilical cord.
During birth the mother stops producing progesterone and the level of oxytocin hormone in the
mother rises causing the uterus to contract, the amnion bursts releasing amniotic fluid (the waters
break), the cervix dilates, the baby is pushed out usually head first, the cord is cut and the placenta is
pushed out (the afterbirth).
Breastfeeding is the ideal nutrient for a baby, it is sterile, it is at the correct temperature and it has
antibodies to protect the baby. Breastfeeding stimulates prolactin hormone which causes the
production of more breast milk.
Infertility is the inability to produce offspring or the inability to produce gametes.
Infertility in men can be caused by a low sperm count (caused by smoking or hormonal imbalance).
Infertility in women can be caused by Inability to ovulate / blocked oviducts.
Invitro fertilisation (IVF) means that the egg is fertilised by sperm outside the body in a glass dish in a
lab. The fertilised egg develops into an embryo and can then be implanted back into the mother‟s
womb.
Contraception is the prevention of fertilisation or prevention of pregnancy.
Examples of contraception are condoms (mechanical) and the birth control pill (chemical).
Mechanical - condom covers penis and forms a barrier to prevent sperm entering woman‟s body.
Chemical - contraceptive pill contains oestrogen and progesterone which prevents ovulation
Avoiding sex during the fertile period is a natural method of contraception.
Vasectomy is the surgical cutting of the sperm duct to sterilise a man. It is 100% successful but it is
irreversible.
Biology Higher Notes 2018
Page | 42
M Kavanagh
MANDATORY PRACTICAL ACTIVITIES
1. Qualitative Food Tests
Food samples are often crushed with a mortar and pestle with water before being tested.
To test a food for starch add iodine using a dropper to a food sample. No heat is needed. A change
from yellow to blue black colour shows starch is present. Water and iodine is used as a control – stays
yellow.
To test a food for protein add biuret solution (or sodium hydroxide + copper sulphate).. No heat is
needed. A change from blue to violet colour shows protein is present. Water and biuret is used as a
control – stays blue..
To test a food for reducing sugars add benedicts solution and heat in hot water. A change from blue to
brick red shows reducing sugar is in the food. Water and benedicts are used as a control- stays blue.
To test a food for fat rub a sample of food in brown paper. A permanent translucent stain shows the
presence of fat. Water and brown paper is the control – no stain.
2. Using a Field Identification Key
A biological key is a series of questions used to identify a plant or animal
In the key above organism A is identified using the key pathway 2,3, - Tribolium
Organism B is identified using the key pathway 2,4 – Planarian
Organism C is identified using the key pathway 2, 4, - Nematode
Be able to construct your on key to identify 5 plants and 5 animals of your own choice.
Biology Higher Notes 2018
Page | 43
M Kavanagh
3. Fieldwork Methods of Capturing Animals (Fauna)



A pooter is used to collect small insects by sucking them into the jar.
A pitfall trap collects small insects that walk on the soil surface at night. They fall into the jar
but cant climb out the smooth side.
A sweep net is dragged through tall grass to collect insects such as grasshoppers and flies.
4. Quantitative Surveys – distribution and population of plant/animal
Ecological surveys are an important way to monitor biodiversity
and to identify pollution.
To find the frequency of Daisy‟s in an area. Select the area to be
studied. Identify any safety hazards such as wet grass or broken
glass. Throw a quadrat (square frame) behind your back to ensure
it is at random. Random sampling techniques prevent bias on the
side of the experimenter. Count the number of daisies in the
quadrat. Record the results in a table. Repeat ten times. Calculate
an average and draw a graph. The results of a sample quadrat area
can be scaled up to represent the entire habitat. A possible source
of error would be not selecting a random sample area, not counting correctly or misidentifying an
organism. A quadrat would not be suitable for studying animals as the animals would run away.
Quadrats are not used to study trees as trees are too big.
To estimate the number of animals such as beetles in a habitat use the capture recapture method.
Catch a number of beetles overnight in a pitfall trap and count them. Mark each with dull paint so as
not to attract predators and release in the same area. Catch more beetles the following night and count
them. Record the number of beetles that are marked.
Calculate the population of beetles as followed.
5. Investigation of Three Abiotic Factors
An abiotic factor is a non living factor that effects plants or animals.
Soil temperature is measured with a soil thermometer, Light intensity is measured with a light meter.
Soil pH is measured with universal indicator and a pH colour chart.
Biology Higher Notes 2018
Page | 44
M Kavanagh
6. Use of the Light Microscope
The total magnifaction is found by multiplying the eyepiece magnification by the objective lens
magnification. An eye piece magnification of 10 and objective lens magnification of 40 gives a total
magnification of 400. If the specimen is .002 mm in size then the image will be 400 times bigger and
appear as 0.8 mm in size. From 2014 higher level exam
A cover slip holds the specimen in place on a microscope slide and also prevents the specimen drying
out.
7. Preparation of Animal Cells for Light Microscope Examination
Rubbed inside of your cheek with a swab or cotton bud to collect cheek cells and transfer to a
microscope slide. Methylene blue is added to cheek cells with a dropper to stain them and make them
easier to see..Leave the stain for 3-4 minutes then rinse off. Lower a cover slip at an angle using a
mounted needle onto the cells The cover slip prevents the specimen drying out and protects the lens
from the stain. Place the slide onto the stage, turn on the lamp, and focus with the coarse focus first
and the focus with the fine focus. The nucleus stains a darker blue than the cytoplasm.
Biology Higher Notes 2018
Page | 45
M Kavanagh
8. Preparation of Plant Cells for Light Microscope Examination
Cut or peel an onion with a scalpel and transfer onto microscope slide on a drop of water . Use a
dropper to add iodine to stain the onion cells. Iodine stains the cells yellow and the nucleus a dark
brown. Lower a cover slip one edge first at an angle to avoid trapping air bubbles. Place onto the
microscope stage and turn on the lamp. Examine under low power magnification first and draw the
cells. The cell walls can be seen which are only found in plant cells.
9. Osmosis Demonstration
Add water to a beaker. Add sugar solution to visking tubing and seal. The visking tubing is a semi
permeable membrane and acts as a model cell membrane in this experiment. Find the mass of the
visking tubing bag and sugar solution and place it in the beaker of water for 24 hours. Reweigh the
visking tubing bag and observe any other changes. The bag is heavier and firmer as it has gained
water by osmosis. As a control repeat with a visking tubing bag that contains water and place in a
beaker of water. As both solutions are the same concentrations there is no movement of water across
the membrane and the visking tubing bag doesn‟t change.
Biology Higher Notes 2018
Page | 46
M Kavanagh
10. The Effect of pH on the Rate of Enzyme Activity
The enzyme used is called Catalase. The Substrate is Hydrogen peroxide. The products are water and
oxygen. Celery is used as a source of catalase. The pH is varied by using different pH buffers The
temperature is kept constant with a thermostatically controlled waterbath. Chopping the celery
releases more catalase.
Mix together chopped celery, water and pH buffer 2 and place in a test tube in a water bath at 300 C.
Place Hydrogen peroxide in a graduated cylinder and place in the water bath. Leave both solutions in
the water bath for 10 minutes to allow time for the enzyme to be affected by the change in pH.
Add the celery extract solution to the hydrogen peroxide and record the height of oxygen foam
produced after 10 seconds... The speed or rate of reaction is measured by the height of foam after 10
seconds. Repeat the experiment at different pH‟s using different pH buffers..
The optimum pH (enzyme works fastest so more foam) was 10. At other pH‟s the enzyme is
denatured.
Biology Higher Notes 2018
Page | 47
M Kavanagh
11. The Effect of Temperature on the Rate of Enzyme Activity
The enzyme used is called Catalase. The Substrate is Hydrogen peroxide. The products are water and
oxygen. Celery is used as a source of catalase. The pH is kept constant by using pH 7 buffers
Mix together chopped celery and water and place in a test tube in a water bath at 100 C. Place
Hydrogen peroxide in a graduated cylinder with some pH 7 buffer and place in the water bath. Leave
both solutions in the water bath for 10 minutes.
Add the celery extract solution to the hydrogen peroxide and record the height of oxygen foam
produced after 10 seconds. The speed or rate of reaction is measured by the height of foam after 10
seconds. Repeat the experiment at different temperatures. The temperature is varied with a
thermostatically controlled waterbath.
The optimum activity of an enzyme is when it is most efficient or working at the best rate. The
optimum temperature (enzyme works fastest so more foam) is 30o C. At higher temperatures the
enzyme is denatured and at lower temperatures the enzyme moves slowly and does not meet the
substrate with the same frequency.
Biology Higher Notes 2018
Page | 48
M Kavanagh
12. Preparation and Application of Enzyme Immobilisation
The enzyme in this experiment is sucrase (or invertase) found in yeast cells. Its substrate is sucrose
(table sugar), its product is glucose and fructose (we can test for glucose with clinistix)
An immobilised enzyme is fixed or trapped in an uncreative or inert material. Immobilised enzymes
can be reused and it is easy to separate the product from an immobilised enzyme.
The enzyme sucrase (in yeast) is trapped when mixed with Sodium alginate. Beads are formed when
this mixture is dropped into calcium chloride from a syringe.
Add the beads to a dropping funnel with sucrose solution. Wait 10 minutes and test drops from the
funnel with a glucose test strip. A purple colour shows the product glucose is formed. The control is
dropping funnel with free yeast solution and sucrose. The control also produces glucose but the
solution is cloudy as the yeast is not separated from product. Immobilised enzymes can be reused.
13. To Investigate the effect of heat denaturation on the activity of catalase.
The enzyme used is called Catalase. The Substrate is Hydrogen peroxide. The products are water and
oxygen. Catalase is used as a source of catalase.
Prepare a solution of chopped catalase and water. Prepare a heat treated enzyme solution by boiling a
solution of chopped catalase and water for 10 minutes.
Add hydrogen peroxide, pH buffer 7 and washing up liquid to a graduated cylinder and place the
cylinder in a water bath at 20 oC. Add the heat treated enzyme solution to the graduated cylinder and
record the height of any bubbles produced after 10 seconds. Repeat the experiment with the untreated
enzyme as a control. There should be no bubbles of oxygen produced with the heat treated enzyme.
The untreated enzyme should produce oxygen bubbles within the graduated cylinder.
Biology Higher Notes 2018
Page | 49
M Kavanagh
14. Influence of Light or Carbon Dioxide on Photosynthesis Rate
Carbon dioxide concentration, light intensity and temperature all affect the rate of photosynthesis.
Place elodea pondweed in a test tube of pond water. Pondwater contains carbondioxide due to
respiration of aquatic organisms. An aquatic plant is used as it produces visible bubbles of oxygen
which can be easily counted. An increase in temperature would increase the rate of photosynthesis
because enzyme activity increases with temperature increase. Temperature is kept constant by using a
water bath. Carbon dioxide can be kept constant by saturating the pondwater with sodium hydrogen
carbonate. Light intensity is varied by moving the lamp different distances. Allow 3 minutes after
moving the lamp to allow the plant to adjust to the new light intensity. To measure the rate of
photosynthesis count the number of oxygen bubbles produced per minute.
As light intensity increases the rate of photosynthesis also increases as electrons are being released
from chlorophyll faster. At high light intensities the rate of photosynthesis stops increasing as carbon
dioxide may be in limited supply.
Light intensity can be measured with a lux meter. Arbitrary units for light intensity can be use
calculated by using the formula 1/d2.
Biology Higher Notes 2018
Page | 50
M Kavanagh
15. Prepare and Show the Production of Alcohol by Yeast
Place yeast cells in a solution of water and glucose
in a conical flask. Use boiled cooled water to
remove the oxygen. Place the flask in a water bath at
30oC. A second flask with water and glucose but no
yeast can be used as a control.
A fermentation lock (air lock) is used to keep out
oxygen. (an oil layer would also keep out oxygen)
Carbon dioxide is produced during the experiment
and can be seen as bubbles.
Fermentation is finished when the bubbles stop.
Filter the mixture into a test tube.
The alcohol produced is detected with the Iodoform
test. Add potassium iodide, Add sodium
hypochlorite, Heat, The colour changes from orange
to yellow (crystals) showing alcohol present.
16. Isolate DNA from Plant Tissue
Isolate DNA from Plant Tissue
First chopped the onion into very small pieces to break
cell walls.
Water, salt and washing up liquid is added to the chopped
onion.
Detergent was used to break down cell membranes.
The salt removes the charge from the DNA and helps it
form clumps and makes it easier to separate.
The mixture was heated in a water bath at 60oC for 15
minutess to denature enzymes called DNases that would
destroy DNA then cooled in ice.
The mixture was blended for a maximum of 3 seconds to
break up cell walls and release DNA. Any longer than 3
seconds and the DNA would be broken down.
The mixture is then filtered through coffee filter paper.
The DNA is dissolved in the filtrate.
Protease was then added to the mixture to break down
protein holding the DNA.
Freezer-cold alcohol is used to bring DNA out of solution so that it can be seen
Biology Higher Notes 2018
Page | 51
M Kavanagh
17. Culturing Leaf Yeasts
Collect leaves from an ash tree in a bag. To avoid contaminating the leaves with bacteria carry out the
following aseptic techniques. Don‟t handle the leaves with your hand. Wipe the bench with
disinfectant or antiseptic wash solution and sterilise the scissors and tweezers in boiling water or
alcohol . Cut small sections of the leaf and attach to the lid of a petri dish, lower surface facing agar,
with Vaseline or petroleum jelly using a tweezers. Place the lid over a petri dish of a nutrient medium
such as malt agar (provides ideal food for yeast cells). The nutrient medium should be sterile – free
from bacteria or other microorganisms. Place the dish in an incubator at 25oC for 3-4 days. The leaf
yeast shows up as pink colonies. Place a petri dish of malt agar in the incubator without leaves as a
control. The control shows no pink colonies. After the experiment dispose of the dishes by burning or
by soaking in disinfectant before adding to waste bin.
18. Dicot Stem T. S. – preparation and microscope examination
Cut a thin slice of a busy lizzy stem with a scalpel. Place the section into water and then transfer onto
a microscope slide with a paintbrush (delicate). Add a cover slip one edge first to avoid trapping air
bubbles which would make the specimen harder to see. The cover slip prevents the specimen drying
out. Place the microscope slide onto the stage of the microscope.
Turn on the light source and use the low power objective first and look through eyepiece. Adjust
coarse focus knob and fine focus knob to view the section clearly. Move to higher objective lens.
Biology Higher Notes 2018
Page | 52
M Kavanagh
19. Effect of water, oxygen and temperature on seed germination
Germination occurs when the radicles are seen emerging from the seeds. Place cress seeds onto wet
cotton wool in a petri dish and leave in a warm area. This is the control. They have all the conditions
needed – water, oxygen and a suitable temperature. The seeds all germinate. Leave another dish of
seeds in the fridge. The temperature is not suitable.. These seeds don‟t germinate. Leave another dish
in an anaerobic jar (removes oxygen) . These seeds have no oxygen and they don‟t germinate.
Alkaline pyrogallol is a chemical that can be used to remove oxygen. Use dry cotton wool in another
dish. These seeds don‟t germinate because they have no water. Water is needed to activate the
enzymes in the seed for germination. A warm temperature provides an optimum temperature for these
enzymes to work. Oxygen is needed for respiration in the growing seed.
20. Digestive Activity of Seeds during Seed Germination
When seeds germinate enzymes are produced to digest food
stored in the cotyledon or endosperm. Digestion is the break
down of food to smaller molecules such as glucose. Seeds
produce the enzyme amylase to breakdown starch to maltose.
Maltose is then converted to glucose and is used in respiration
providing energy for the germinating seed. Soak broad beans
overnight to activate the enzymes and start germination. Boil half
the seeds to kill them –they will act as the control. Disinfect both
sets of seeds to remove any bacteria or mould. Cut the seeds with
a sterile blade and place the seeds cut surface down onto starch
agar. This exposes the enzymes in the seed to the substrate. The
starch agar provides the substrate for amylase enzymes produced
by the germinating seeds. Leave for 3 days. Add iodine solution
to the starch agar in each dish. The dish that contained the live
germinating seeds showed clear patches (negative result with
iodine test) under and around the seeds where the starch was broken down by enzymes. The dish
containing the dead seeds (the control) showed no clear patches – it was all blue black showing that
no digestion had occurred and that the starch was still there. Boiling the seeds denatured the enzymes
which prevented any digestion of starch.
Biology Higher Notes 2018
Page | 53
M Kavanagh
21. Effect of I.A.A. Growth Regulator on Plant Tissue
IAA is growth regulator. It can stimulate or inhibit root growth in plants such as radish seedlings
depending on the concentration used.
Prepare different concentrations of IAA solution by serial dilution. Start with a solution of 102 ppm
(parts per million) IAA and water. Transfer 1 ml of this to 9 ml of water to create a 101 ppm solution.
Transfer 1 ml of this to 9 ml of water to create a 1 ppm solution. Repeat this procedure to create a
series of more dilute solutions.
Add each IAA solution to separate petri dishes of cotton wool and 5 radish seeds. As a control add
just water to a petri dish of cotton wool and radish seeds. Leave the dishes on edge (to allow roots to
grow down and shoots up) in a warm location. After 4 days measure the length of the roots and
shoots of the seedlings using a plastic grid marked in mm. Calculate the average length of the roots
and shoots at each concentration. Compare to the length of roots and shoots in the control. Results- at
very high concentrations of IAA ( 102) root and shoot growth is inhibited. At 10-4 ppm (low
concentration) root growth is stimulated.
Biology Higher Notes 2018
Page | 54
M Kavanagh
22. Heart Dissection
Wash the heart and place it ventral (front) side facing up on a tray. Identify the front of the heart by
the diagonal coronary artery. The left hand side of the heart feels firmer. Use a scalpel to cut through
the left side of the heart to see the bicuspid valve and the right side of the heart to see the tricuspid
valve. Cut the Aorta and pulmonary artery to show the semi lunar valves. The semilunar valves are
found at the base of the aorta and pulmonary artery. Pin the heart with flag labels. Dispose of the heart
by burning it when finished.
23. Effect of Exercise on the Pulse of a Human
As a control measure the resting rate in beats per minute (BPM) by sitting down and place a finger on
the wrist and feel the pulse. The pulse is the regular expansion of an artery close to the skin in the
wrist as the heart contracts and pumps blood. Count the number of pulses in 1 minute. Repeat 3 times
and get an average. Take exercise by running on the spot for 1 minute and take the pulse rate again.
Measure recovery time by counting the pulse rate immediately after exercise and record the time until
the resting rate is reached again. The fitter a person is the faster the recovery time and the less the
increase in BPM during exercise. The pulse rate increases because the body needs more oxygen
during exercise to provide the extra energy from respiration..
Recovery time for fit compared to unfit person.
Biology Higher Notes 2018
Page | 55
M Kavanagh