Vegetative Propagation of Flowering Plants
Vegetative Propagation
Asexual formation of new plants that develop from multicellular structures that grow by mitosis and become separated from the parent plant.
Examples
Stem Example of Vegetative Propagation: potato tuber
Textbook Diagram: Potato Plant and its Tubers
The potato tuber is a stem modified for winter survival and asexual reproduction.
The tuber ‘germinates’ in spring growing into a new plant.
The potato plant forms many underground stem tubers during the growing season.
The aerial parts die away at the end of the season and the tubers survive.
Root Example of Vegetative Propagation: root tuber
Textbook Diagram: Root Tubers of Orchid or Dahlia
The root tuber is a root modified for winter survival and asexual reproduction.
Some of the roots become greatly swollen with food reserve.
The aerial parts die down at the end of the season.
The root tubers survive each with the base of a stem containing buds.
Buds on the stem bases germinate in spring forming new plants fuelled with food from the tuber.
Leaf Example of Vegetative Propagation: plantlets of Bryophyllum (‘mother of thousands’)
Textbook Diagram: Bryophyllum plant.
Small plants develop at the margins of the leaves.
The plantlets fall off the leaf and will grow into a new plant if the conditions are suitable.
Bulb Example of Vegetative Propagation: onion bulb
Textbook Diagram: longitudinal section of onion bulb.
The onion bulb is a short stem carrying fleshy leaves, axillary buds and a terminal bud.
The terminal bud of the bulb develops into a new plant in the growing season.
At the end of the season food is transported to one or more axillary buds.
These buds become swollen with food each forming a new bulb.
Comparing Reproduction by Seed and Vegetative Propagation
Greater genetic variation by seed – population is better adapted to survive environmental change.
Greater dispersal by seed – less competition and greater colonisation of new habitats.
Greater number of offspring by seed: greater success in local habitat
Less food reserve per individual by seed: reduced success on germination.
Genetic similarity by vegetative propagation: more successful colonisation of stable habitat.
Artificial Propagation
Cuttings
Textbook Diagram: cutting set up.
Cutting is the detachment of part of a plant to grow a new plant.
Young healthy lateral branches are suitable.
Some of the leaves may be removed to reduce transpiration and so conserve water.
Place cut end of stem into well-drained aerated compost.
A new root system develops at the cut end.
Advantages: fast, easy, cheap and new plants are genetically identical to parent plant.
Grafting
Textbook Diagram: grafting procedure.
Grafting produces new plants by joining a branch of the desired shoot system (scion) of one plant onto the vigorous root system (rootstock) of another.
Complementary shaped cuts are made in stem of scion and rootstock.
The scion stem is joined to the rootstock stem.
The meristematic tissue of scion and rootstock are in contact and its growth unites them.
Advantages: fast, flowers and fruit are identical to the scion parent.
Layering
A young healthy stem is bent into a small hole with the terminal bud above soil level.
The hole is filled with soil.
A new root system develops at an underground node.
The terminal bud forms a new shoot system.
The new plant can then be separated from the ‘parent stem’.
Tissue Culturing (Micropropagation)
Textbook Diagram: tissue culturing set up.
Remove a very small sample of meristematic tissue from the tip of a branch.
This tissue sample is likely to be free of virus infection.
Place the tissue sample on sterile nutrient agar in a dish.
Plant growth regulators can be added to stimulate and control development.
A plantlet will grow from the tissue sample.
Transfer to a suitable compost for further growth.
Transport in Plants
Uptake of Water
Water is absorbed in plants by young roots.
The water is absorbed in the dermal cells by osmosis.
The cell sap of the epidermal cells is much more concentrated than soil water.
Roots hairs greatly enhance water absorption.
Root hairs increase the root surface area and catchment space for water uptake.
Water uptake is fast as these epidermal cells do not have a cuticle.
Textbook Diagrams: transverse and longitudinal sections of a young root.
Water Transfer to Xylem
Water passes into the dermal cells by osmosis from the soil.
Water can move across the root ground tissue from cell to cell to the xylem by osmosis.
Water can also move towards the xylem through the intercellular spaces.
Water can pass through the cells walls towards the xylem.
Direct entry into the xylem tracheids and vessel members is by osmosis.
Upward Movement of Water
Root Pressure
The xylem sap is more concentrated than soil water.
Water passes from the soil into the xylem by osmosis.
The force of the osmotic flow of water drives the water from the roots up into the stem.
The rise of water is short – a metre at most.
The rise also varies with changes in the concentration of xylem sap.
The xylem sap concentration varies with mineral ion absorption.
Transpiration Pull
Transpiration is the loss of water from the surface of a plant by evaporation.
Transpiration mostly takes place from the leaves.
Water in soil, roots, stems and leaves is one continuous mass – the water in the leaves is in direct contact with water in the soil.
Water has great cohesion – water molecules are glued tightly to each other.
Due to its cohesion, a change in the movement of one water molecule affects all.
The loss of water from the leaf cells pulls water in from the xylem, this pulls water up the xylem, and this in turn pulls water from the ground tissue of the roots causing water to be pulled in from the soil.
Transpiration supplies the ‘pull’ or tension force that lifts the water up the plant.
The flow of water up the plant is called the ‘transpiration stream’.
The rate of water flow is directly related to the rate of transpiration.
The weight of the column of water is supported by water’s great adhesion to cell walls.
ATP is not used in water transport therefore it is a passive process.
Water flow is upward only in a plant.
The rate of transpiration from leaves is affected by the thickness of the cuticle.
The opening and closing of the stomata is a major factor in controlling water loss by transpiration.
Note: Dixon and Joly, two Irish professors, were the first to put forward the ‘cohesion-tension model’ of water transport in xylem.
Textbook Diagram: pathway of water flow into the plant and up to the leaves.
Mineral Nutrients
Plant mineral nutrients are in solution in soil water.
The root dermal cells absorb the mineral nutrients by diffusion and active transport.
The root dermal cells are rich in the ATP producing mitochondria.
The mineral nutrients are actively ‘pumped’ into the xylem.
The mineral nutrients are transported throughout the plant in the xylem.
Food Transport
Food is transported in the sieve tube elements of the phloem.
Food transport is an active process because ATP is needed.
Phloem sap is really a sugar solution.
In the growing season sugar made by in the leaves by photosynthesis is transported to the growing points and excess is often sent to the roots for storage.
At the start of the growing season the food is transported from the storage regions to the growing points.
Transport of food can be up and down the stem.
CO2 Transport
Carbon dioxide gas enters the leaves by diffusion through the stomata.
Carbon dioxide diffuses to the photosynthetic cells through the leaf’s air spaces.
Aerobic respiration produces carbon dioxide gas as a waste.
Carbon dioxide will diffuse into the intercellular air spaces from respiring plant tissue.
This carbon dioxide gas will diffuse through the air spaces to photosynthetic tissue.
Diffusion in air is much faster than diffusion in water.
Plant Growth Regulation and Responses
Tropisms
A tropism is a growth response of a plant to an external stimulus.
A tropism can be positive or negative.
Positive: the growth response is in the direction of the stimulus.
Negative: the growth response is away from the stimulus.
Light intensity, day length, gravity and temperature are major factors that influence plant growth.
Phototropism is the growth response of a plant in response to light direction.
Geotropism is the growth response of a plant in response to gravity.
Thigmotropism is the growth response of a plant to physical contact (touch).
Chemotropism is the growth response of a plant to a particular chemical.
Hydrotropism is the growth response of a plant to water.
Tropisms are adaptive responses; they increase the plant’s chance of survival and reproduction.
Significance of Phototropism and Geotropism
Stems
Positive phototropism and negative geotropism of stems.
The stems will grow towards the light and up away from gravity.
This places the leaves in better light with increase in photosynthesis.
More food means better growth and reproduction.
Roots
Negative phototropism and positive geotropism of roots.
The roots grow away from light and down in the gravity of direction.
The roots are more likely to find ‘soil’ in this direction.
Soil is important for plants for anchorage, water and mineral nutrients.
Plant Growth Regulators
Tropisms are controlled and moderated by special chemicals called growth regulators.
A plant growth regulator is an organic substance that is made in tiny amounts by the plant and has very definite specific effects on tissue metabolism and growth.
The target tissue of the growth regulator may be the local tissue or tissue in a different part of the plant.
The growth regulator affects the cell cycle, cell enlargement and cell differentiation.
Natural plant growth regulators that move to their target are called plant hormones.
The transport of plant hormones to distant targets may be by diffusion, in xylem or in phloem.
Five Major Groups of Plant Growth Regulators
Auxins: growth promoters – stimulates stem cell elongation, flower and fruit formation.
Gibberellins: growth promoters – stimulates stem cell elongation and seed germination.
Cytokinins: growth promoters – stimulates cell division and differentiation.
Abscisic Acid: a growth inhibitor – causes seed and bud dormancy, represses cell elongation.
Ethylene: often a growth inhibitor – fall of leaves and fruit.
Many growth responses are not cause just by one growth regulator but by a combination of different regulators and the concentration of each in the ‘mix’.
Auxin and gibberellin are together involved in stem cell elongation – each affecting a different part of the process.
Auxin and cytokinin are together involved in the terminal bud suppressing the development of lateral buds – this is termed ‘apical dominance’.
Auxin
Production Sites
meristems – apical and lateral,
young leaves,
developing fruit and seeds.
Functions
increase the plasticity of plant cell walls for enlargement and shaping.
influences the expression of specific genes involved in growth.
role in stimulating cell division.
Effects
change in growth direction of stem and root,
apical dominance – prevent lateral bud growth,
fruit development,
formation of adventitious roots.
Mechanism of a Plant Response
E.g. positive phototropism of a stem to unilateral light.
Auxin is produced in the apical meristem of the stem.
In unilateral light much auxin moves to the shaded side of the stem apex.
Auxin moves away from the stem apex towards the elongation zone.
There will be an unequal distribution of auxin in the elongation zone.
The shaded side will have a higher auxin concentration.
High auxin concentration in stems stimulates cell elongation.
The shaded side cells are stimulated to greater elongation than the cells on the other side.
This unequal growth causes the stem to bend towards the light.
Synthetic Plant Growth Regulators These are inorganic substances made by physical chemistry that affect plant growth. Some mimic the natural growth regulators in structure and action. Many are completely different to natural regulators both in structure and action.
Commercial Use of Plant Regulators Any two of:
Rooting Power: increase the success of stem cutting by promoting extensive early rooting.
Cytokinin: use in tissue culture to stimulate cell differentiation.
Ethelene: quick ripening of mature ‘green bananas’ for the market.
Auxin: as a selective weed killer to reduce competition and so promote crop growth.
Gibberellins: production of seedless fruits e.g. oranges.
(Practical use of abscisic acid has not yet been extensively developed.)
Plant Protection Adaptations
Cuticle: protection against leaf infection by bacteria, fungi and viruses.
Cork: protection against insect pest damage.
Cuticle and Stomata Closure: protection against excessive water loss.
Stinging Dermal Hairs: protection against ‘large’ herbivores.
Spines and Thorns: protection against ‘large’ herbivores.
Toxic Substances: protection against insect pests and ‘large’ herbivores.
Foul Tasting Chemical: discourage ‘large’ herbivores.
Warning Chemicals: to alert neighbouring to start making protective chemicals.
Heat Shock Proteins: prevent specific proteins from denaturing so they remain functional.
Mandatory Activity
Investigate the Effect of Auxin on Plant Tissue
Germinate 60 pea seeds until plumule is 1.5 cm long.
Remove the tip from each plumule – removes the source of auxin.
Cut the plumule to a length of one centimetre.
Organise six sets of 10 ‘decapitated’ plumules.
Measure and record the total length of each set.
Place one set in sucrose solution without auxin – control.
Place the other sets in a sucrose solution of different auxin concentrations.
The concentrations are 100 ppm, 10 ppm, 1 ppm, 0.1 ppm, 0.01 ppm
Sucrose will be a food source for the live plant tissue.
Replace the solutions every day.
After three days measure the total length of each set.
Compare the results to the control.
Graph the results with auxin concentration on the x-axis and change in length on the y-axis.
Repeat the entire process many times to verify the results.
Preparation of Auxin Solutions
Method: Serial Dilution
Five small10 cm3 screw-top bottles.
Separate syringe for each jar.
10 cm3 of auxin solution at 100 ppm (parts per million) in the first jar.
9 cm3 of distilled water in the other four jars.
Remove 1 cm3 of auxin solution from the first jar with a syringe.
Transfer this1 cm3 of auxin solution to the second jar.
Close both jars with their lid.
Shake the second jar vigorously to thorough mix the distilled water and the auxin solution.
Repeat the same procedure from second jar into third jar.
Repeat until the fifth and last jar.
After mixing the last jar discard 1 cm3 of its solution.
All jars contain 9 cm3 of auxin solution each successive one is 10 times more dilute.
Circulatory System
Circulatory System: blood and lymphatic systems.
Blood System |
Lymphatic System |
Liquid: blood |
Liquid: blood |
Vessels: arteries, arterioles, capillaries, venules, veins |
Vessels: capillaries, ducts + nodes |
Pump: heart |
No specialised pump |
Circuit Flow: from heart to organs back to heart . |
Linear Flow: to subclavian veins from organs |
The Blood System
Functions of Blood System
Transport: to and from tissue cells
Nutrients to tissue cells: amino acids, glucose, vitamins, minerals in solution in the plasma; lipids as lipoproteins.
Oxygen: by red blood corpuscles.
Wastes: urea, uric acid and some CO2 in solution in the plasma. Most CO2 is carried in the red blood corpuscles.
Temperature Regulation: by altering the blood flow through the skin.
Immunity: protection against pathogens — blood clotting; phagocytes, lymphocytes and antibodies distributed in blood.
Communication: hormones distributed to all parts of the body in the blood.
Composition of Blood Plasma: pale yellow sticky liquid; 55% of blood volume.
Components: water 92%, dissolved protein 8%, glucose, amino acids, vitamins, minerals, urea, uric acid, CO2, hormones, antibodies.
Suspended Solids
Textbook Diagram: structure of suspended solids of blood.
Red Blood Cells
Tiny biconcave disc-shaped cells.
Do not have a nucleus.
Do not have mitochondria.
Their cytoplasm is rich in haemoglobin.
O2 binds to the iron in haemoglobin.
Made in the bone marrow.
Survive for about four months.
Destroyed and recycled by the liver and spleen.
White Blood Cells (leucocytes)
These are colourless cells and possess a nucleus.
They function in defending the body against pathogens.
Some ‘feed’ on pathogens by phagocytosis.
Others produce antibodies, the specific defence proteins.
Made by the bone marrow and lymphatic tissue.
Platelets
These are tiny fragments of large bone marrow cells.
They carry specialised blood clotting chemicals.
The clotting chemicals are released where blood and lymph vessels are injured.
A nucleus is not present in platelets.
Specialist White Blood Cells
Monocytes: largest white blood cells – engulf viruses, cancer cells, damaged and dead tissue cells.
T Lymphocytes (T cells) – made in the bone marrow, mature in the thymus.
Helper T Cells: stimulate the multiplication of other lymphocytes.
Killer T Cells: inject lethal chemicals into pathogenic cells.
Suppressor T Cells: halt the immune response when the infection has been overcome.
Memory T Cells: give immediate future protection against the same pathogen.
B Lymphocytes (B cells): specific antibody producing cells.
Blood Grouping
ABO Blood Grouping System
Four groups. The blood group depends on the presence or absence of antigen A and antigen on the surface of red blood cells.
Group A: antigen A only.
Group B: antigen B only.
Group AB: antigen A and antigen B are both present.
Group O: antigen A is not present and antigen is not present.
Rhesus Blood Grouping System
Two groups. The group depends on the presence or absence of the Rhesus-antigen.
Rh-positive: the Rhesus-antigen is present.
Rh-negative: the Rhesus-antigen is not present.
Blood Vessels
Textbook Diagrams: transverse sections of artery, vein and capillary.
Artery compared to vein
The wall of the artery is thicker: thicker connective tissue layer, thicker mixed layer of muscle and elastic tissue.
The lumen of the artery is much narrower.
Arteries do not have valves along their length, veins do.
Valves in the veins prevent the backflow of blood so the flow is in one correct direction towards the heart.
Blood flows away from the heart in arteries; blood flows towards the heart in veins.
Blood pressure in arteries is higher and so also the speed of blood flow.
Pulse flow in an artery, steady flow in a vein.
Muscle tissue in not present in the capillaries
The muscle layer allows change in the diameter of vessels. This helps to regulate blood flow to and from the tissues in response to their requirement.
Capillaries
The real work of the blood, exchange with tissue cells, is carried out at the capillaries.
Capillaries are the microscopic links between arteries veins.
The capillary wall is one cell thick and somewhat porous — ideal to allow materials to pass in and out.
All tissue cells very close to a capillary so exchange is very efficient.
Exchange at the capillaries is by diffusion, mass flow and active transport.
Blood flow in capillaries is slow giving enough time for effective exchange.
Closed System of Blood Vessels
The blood does not make direct contact with the tissue cells.
The blood is retained in the blood vessels.
A closed system is very responsive to the change needs of the organs and is highly efficient.
Double Circuit
Pulmonary Circuit: deoxygenated blood flows from the heart to the lungs, oxygen is taken on and carbon dioxide is excreted, oxygenated blood flows from the lungs back to the heart.
Systemic Circuit: oxygenated blood flows from the heart to the organ systems of the body, oxygen is delivered and carbon dioxide is taken on, deoxygenated blood flow from the organs systems back to the heart.
The double circuit does not allow mixing of oxygenated and deoxygenated blood. Therefore oxygen supply is highly efficient.
Portal System
A portal blood vessel has a set of capillaries at each end.
The blood flows from one set of capillaries along the portal vessel to the other set of capillaries.
The hepatic portal vein carries blood rich in absorbed nutrients from the capillaries in the alimentary canal to capillaries in the liver.
The Heart
Textbook Diagram: structure of the heart.
The heart is located in the thoracic cavity between the lungs protected by the rib cage.
The heart is a double pump.
The right side collects deoxygenated blood from all parts.
The right side pumps deoxygenated to the lungs for oxygenation and excretion of CO2.
The left side collects oxygenated blood from the lungs and pumps it to all parts.
The right and left side fill and empty in unison.
Each side pumps the same volume of blood.
The wall of the left ventricle is about three times thicker than that of the right ventricle.
The left ventricle needs more cardiac muscle to give the blood a much stronger push.
The oxygenated blood has to be driven a far greater distance.
Heart action
Deoxygenated blood from the inferior and superior vena cava flows into the right atrium and on into the right ventricle.
Oxygenated blood from the pulmonary veins flows into the left atrium and on into the left ventricle.
The right and left ventricles fill with blood.
Then the atria now fill with blood.
The pacemaker (sino-atrial node) in the right atrium generates a nerve impulse causing the atria to contract.
Contraction of the atria adds extra blood to the ventricles.
The transmission of the impulse to the ventricles is delayed giving time for them to receive the additional blood.
The impulse enters the ventricles at the atrio-ventricular node and travels through the septum to the ventricles.
The ventricles contract and force the blood towards the openings of the arteries, pulmonary artery and aorta.
The cuspid valves close (lub sound) preventing blood returning to the atria.
The semilunar valves are pushed open by the inrushing blood.
The elastic arteries expand quickly taking the blood.
When the ventricles stop contracting the arteries recoil elastically.
The elastic recoil squeezes the blood in the artery forcing it further away from the heart.
The closure of the semilunar valves prevents blood flowing back into the ventricles from the arteries.
The blood flows completely along the artery into the distant capillaries.
Cardiac cycle
Diastole: relaxed cardiac muscle — the heart fills with blood under low pressure from the veins.
Systole: cardiac muscle contracting — the chambers of the heart are emptying of blood.
Atrial Systole: contraction and emptying of the atria supplying extra blood to the ventricles.
Ventricular Systole: contraction and emptying of the ventricles ejecting blood from the heart into the arteries.
Cardiac Muscle
The muscle making up the heart is called cardiac muscle.
It is myogenic, i.e., stimulates itself to contract — contracts without any external stimulation.
It is an involuntary, strong muscle that does not fatigue.
The Pacemaker
It is a small area of cardiac muscle in the wall of the right atrium.
It lies close to the entry of the superior vena cava.
Its automatic rhythmic contraction starts each cardiac cycle.
Two nerves from the medulla oblongata connect to it influencing its rate of contraction.
One nerve quickly accelerates the heart rate and the other can quickly reduces it back to resting rate.
Factors affecting heart rate
Increase: exercise, increased body temperature, stress, mental excitement, infection.
Decrease: increased physical fitness, sleep, and mental relaxation.
Coronary circulation
The blood flowing through the heart does not directly serve the heart.
Like all other organs the heart muscle has its own blood circuit.
Two coronary arteries arise from the aorta just beyond its semilunar valve.
The right coronary artery mostly serves the right atrium and right ventricle.
The left coronary artery is much larger and supplies the left atrium and left ventricle.
There is a very extensive capillary network throughout the cardiac muscle.
The coronary veins collect the blood from the capillaries.
The coronary veins deliver the deoxygenated blood to the right atrium.
Textbook Diagram: General Circulation and learn the names of the major blood vessels.
Pulse
This is a wave of vibration that passes from the heart along a systemic artery.
The vibration is caused by the forceful ejection of blood from the heart.
The pulse wave travels much faster than the blood.
The pulse rate is the same as the heart rate.
Blood Pressure
The blood is pressing against the blood vessel walls.
Pressure is how concentrated is the push.
The pressure varies along the circuit – decreasing from artery to arteriole to capillary to venule to vein.
Pressure is highest at the start of the artery and lowest at the entrance to the atrium.
Blood pressure is much higher in the aorta than in the pulmonary artery.
Reference blood pressure is measure in a large artery in the upper arm.
The pressure need to stop blood flow in this artery is measured at diastole and systole.
Standard healthy readings: 80 mm Hg diastolic, 120 mm Hg systolic.
Effect of Smoking
Hardening of the arteries.
Increased risk of heart disease.
Raised blood pressure.
Increased risk of stroke.
Effect of Diet
Anaemia: lack of iron.
High Blood Pressure: excessive salt.
Low Blood Pressure: lack of protein.
Effect of Exercise
Lower resting heart rate – more efficient heart.
Dilated arteries – improved blood flow to all the organs.
Less risk of heart disease.
The Lymphatic System
The lymphatic system is a collection of special drainage vessels collecting excess tissue fluid from the different parts of the body. This excess tissue fluid re-enters the blood at the left and right subclavian veins.
Once the tissue fluid enters the lymphatic capillaries it is called lymph. Lymph is a clear liquid similar in composition to the plasma but with only 2% protein in comparisons to the plasma’s 8%.
The lymphatic capillaries unite to form lymphatics (lymph veins) and larger lymph channels. The lymphatics are richly supplied with valves. The valves keep the lymph flowing in the one direction towards the subclavian veins.
Distributed along the lymphatics are lymph nodes. The lymph nodes filter the lymph and produce lymphocytes. The lymphocytes protect against pathogens by phagocytosis and antibody production.
Lymphatics from the lower regions merge forming the thoracic duct. The thoracic duct drains lymph into the left subclavian vein. The thoracic duct also receives lymph from the lymphatics draining the upper left part of the body. The right thoracic duct collects lymph from the upper right part of the body draining it into the right subclavian vein.
The lymph is moved along the lymph vessels by the squeezing action of the skeletal muscles, pressure changes in the thorax during breathing and by the rhythmic contraction of the lymph vessel walls.
Blood is the source of the excess tissue fluid
Textbook Diagram: formation of tissue fluid and lymph.
As the blood enters the capillaries the pressure forces some of the plasma out through the wall.
The escaped fluid is called tissue fluid similar in composition to plasma with only about 2% protein.
The tissue fluid is the true environment of the cells of the body — our cells are aquatic.
At the venule end most (90%) of the escaped tissue fluid is drawn back into the blood by osmosis.
The escaped proteins do not return to the blood at the capillary.
The 10% excess tissue fluid must be drained away to allow the tissue to function normally.
The lymphatic system carries out this function.
Summary of the major functions of the Lymphatic System
Circulatory role
Return the excess tissue fluid to the blood: this maintains blood volume, pressure and concentration.
Collect and deliver the absorbed lipids from the small intestine to the blood (enters at the left subclavian vein).
Defence role
The lymph nodes filter out pathogens in the lymph.
Production and ‘export’ of lymphocytes to the blood system for general distribution.
Detection of antigens and production of specific antibodies.
Mandatory Activities
Investigate the effect of exercise on your heart rate
Find a strong pulse in your wrist.
Each pulse is a heartbeat.
Three times measure and record the heart rate at rest.
Calculate the average.
Count the number of pulses in 20 seconds and multiply by three - this is the heart rate-beats per minute.
Repeat the measurements again three times during gentle exercise — slow jogging on the spot.
Repeat the measurements again three times during strenuous exercise — fast jogging on the spot.
Rest must be taken between each exercise session.
Compare the results for rest, gentle and vigorous exercise.
Repeat many times to verify the results.
Conclusion: exercise increases the heart rate and the more vigorous the exercise the higher the heart rate.
Dissect, display and identify an ox’s or a sheep’s heart
Squeeze the ventricles – the soft side is the right ventricle.
Squeeze to locate the position of the septum.
Use a blade to cut into the right ventricle just to the side of the septum.
Cut from the base of the layer of fat to the pointed end.
Then cut across just below the layer of fat.
Pull back this angular flap to see inside the right ventricle.
Now repeat on the left side.
Remove the top of each atrium to see into the atrial cavity.
Identify the arteries – pulmonary connected to right ventricle, aorta to left ventricle.
Look into the stumps of the arteries to see the semilunar valves.
Pin down the dissection and flag label.
Breathing System
Functions
Effective absorption of oxygen from the air
Excretion of carbon dioxide to the air
Structure
Textbook Diagram: macrostructure of the breathing system.
Nasal Cavity
hairs and mucus filter out much of the dust and small particles like bacteria
the wet surface moistens the air
the rich blood supply warms the air to body temperature
Mouth Cavity
air may enter via the mouth but it does not get the same high level of cleaning, moistening or heating
Epiglottis
protects the trachea against the entry of food and drink
by a reflex action the glottis (opening of trachea) is closed by the epiglottis during swallowing
Larynx
uses the flow of air along the trachea to produce specific sounds
Trachea
a channel for air to flow to and from the bronchi
its mucus lining traps dust and bacteria
the beating of cilia on its surface move the mucus to the pharynx for swallowing
the C-shaped rings of cartilage support the wall of the trachea keeping it permanently open
Bronchus
an open tube for air to flow in and out of a lung
it is similar in structure to the trachea but narrower
Bronchioles
a narrow open tube for air to flow in and out of the alveoli
Alveoli
the sites of gas exchange in close extensive contact with blood capillaries
Lungs
two large spongy respiratory organs in the thoracic cavity
possess a large surface area for gas exchange of relatively small volume
Pleural Membranes
surround and protect the lungs
line the thoracic cavity
‘glues’ the lungs to the chest wall and diaphragm
permits smooth moving of lungs across chest wall and diaphragm during breathing movements
Ribs
protective bony cage around the lungs and heart; play a role in breathing
Diaphragm
a broad sheet of muscle between the thoracic and abdominal cavities
its contraction is responsible for 75% of the air drawn into the lungs
Intercostal Muscles
changes the shape and volume of the rib cage during breathing
responsible for 25% of the inspired air