The tower group 4 built was 55 cm tall. It was not very successful as the design we had come to a consensus on had difficulty standing without falling. In order to improve, we could have generated more ideas during the brainstorming time. Instead of a cylindrical design as the base, we should have thought of a conical design. Although everyone helped in the building of the structure, more members should have contributed to the building up of ideas. Our strengths however, are that we were cooperative with each other, and this is a quality we should exhibit in other activities as well.
Author Archives: phoebezhouhuixin
Science Investigative Project
Name : Phoebe Zhou Huixin ( 25 ) Class: 208
Chaos Theory and the Double Pendulum
Introduction
Background information:
Although chaotic systems were first observed in the 1880s by Henri Poincaré, a French physicist, the Chaos Theory was pioneered only in 1961 by Edward Lorez, who at that time was working on weather prediction. Lorenz published “The Essence of Chaos” in 1993, providing more insight on chaotic systems. He put forward the idea of the Butterfly Effect, which describes how the flapping of a butterfly’s wings in Brazil, although only a tiny part of initial conditions of a chain of events, can lead to a tornado in Texas.
Despite it being hard to define chaos in the fields of mathematics and science , the universally accepted ideas of the Chaos Theory are that chaotic systems that may appear random are reliant on simpler deterministic equations, and that small variations in initial conditions can cause very complex behaviors in the system after some time. Most physical systems exhibit chaotic behaviour as there are many initial conditions and contributing factors that affect long-term behaviour. The weather is an example whereby there exist too many influencing factors to track to predict with total accuracy. However, the Chaos Theory is still being developed. One of the theory’s limitations is that it is a frustrating process to determine if experimental data are random or deterministic. This is because it is not clear how much data should be used to construct a phase set, and large biological systems usually do not stay in the same state long enough to gather the required amounts of data. Also, slow systems do not seem to benefit from the results of the Chaos Theory in general i.e. when events are infrequent and large amounts of friction dissipates energy and damps out disturbances. (Ceorote, 2012)
The Chaos Theory states that chaotic motion of non-linear dynamic systems obeys particular laws. Non-linear systems are systems that do not satisfy the superposition principle, whereby the net response at a given time caused by two or more stimuli is the sum of the responses each stimuli would have caused individually. A dynamical system is a system that changes over time, and whose behvaior can be (in theory) described as a function that takes time as a parameter. (Scienceblogs, 2009) The double pendulum, which are two rigid pendulums attached one above the other, is a real-life example of a non-linear dynamic system that exhibits chaotic motion. Variations in initial conditions such as length, mass and angle of release of the pendulum can greatly affect the motion path of the pendulum. The second pendulum may make unpredicatable but continuous 360 degree spins (i.e. flipping). However, when the double pendulum is released at small angles, it demonstrates linear motion. Assuming that a double pendulum starts to display chaotic behaviour only when the swing of the second pendulum makes a full circle, the experiment seeks to determine how the following conditions predispose the setup to behave chaotically:
- How does the length of the first pendulum affect the angle at which the first pendulum has to be released in order for the second pendulum to flip?
- How does the length of the second pendulum affect the angle at which the first pendulum has to be released in order for the second pendulum to flip?
My hypothesis for the first research question is: when the length of the first pendulum increases, the angle of release of the first pendulum can be decreased in order to cause the second pendulum to flip. My hypothesis for the second question is: when the length of the second pendulum increases, the angle of release of the first pendulum has to be increased in order to cause the second pendulum to flip. The idea for the experiment was formed when I was watching a tennis match and wondered how many factors affected the accuracy of the swing of the racquet. After that I found out online that not only the swing of the racquet, but also activities such as golf and running, can be associated with the motions of double pendulums. Answering the research questions above will thus help in the understanding of sports theory, for example, in tennis, how does the length of the racquet affect the angle at which the racquet has to come into contact with the ball in order for the player to return the ball well?
Apparatus and Materials
- Aluminium pieces to be used as first pendulums
- Length= 20.3 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 25.3 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 30.3 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 35.3 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 40.3 cm, Width= 3 cm, Thickness= 0.15 cm
- Aluminium pieces to be used as the second pendulums:
- Length= 8 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 21.5 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 26.5 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 31.5 cm, Width= 3 cm, Thickness= 0.15 cm
- Length= 36.5 cm, Width= 3 cm, Thickness= 0.15 cm
Note:
There are only 6 pendulums of
a) 8 cm (not used as first pendulum)
b) 20.3 cm or 21.5 cm when used as first or second pendulums respectively
c) 25.3 cm or 26.5 cm when used as first or second pendulums respectively
d) 30.3 cm or 31.5 cm when used as first or second pendulums respectively
e) 35.3 cm or 36.5 cm when used as first or second pendulums respectively
f) 40.3 cm (not used as second pendulum)
- Retort stand
- Two smooth rivets
- Helix Oxford brand protractor
- SureMark brand stick tack
- Smooth, thin plastic sheet
Aluminium is an appropriate material for the pendulums as it is lightweight and thus will not cause the retort stand to fall over, and is unlikely to be able to come off its hinges, which ensures the safety of those nearby.
Methodology
Steps taken:
To test first research question: How does the length of the first pendulum affect the angle at which the first pendulum has to be released in order for the second pendulum to flip?
- Draw a thin line lengthwise in the middle of all the aluminium pieces. This will aid in determining the angles of release during the experiment.
- Embed one end of the first rivet tightly in the wooden block and use the retort stand to clamp the wooden box tightly.
- Place the first pendulum of length 20.3 cm on the first rivet, followed by a small piece of plastic sheet (approximately 5 cm by 5 cm), followed by stick tack. The stick tack secures the first pendulum to the rivet and ensure the first pendulum does not fall off when swinging. This also ensures the safety of those nearby. The plastic sheet is placed between the first pendulum and stick tack to minimize friction should the rubbing of the first pendulum and stick tack occur.
- Put the second rivet thorugh the hole on the bottom of the first pendulum.
- On the second rivet, place another piece of plastic sheet, followed by the second pendulum of length 8cm, followed by yet another piece of plastic sheet, followed by stick tack to secure the second pendulum to the rivet. The first plastic sheet is placed between the first and second pendulums to minimize friction.
- Using a protractor, release the first pendulum at increments of 5 degrees, up till 170 degrees. Record the angle of release at which the second pendulum starts to flip. Release the first pendulum at the same angle five times to ensure reliability of results.
- Repeat steps 3-6 using 25.3 cm, 30.3 cm, 35.3 cm and 40.3 cm aluminium pieces for the first pendulum.
- From the table of results, make a conclusion on how the angle of release is affected by increments of 5 cm in length of the first pendulum.
Front view and side view of set-up with 20.3 cm and 8 cm first and second pendulums
To test second research question: How does the length of the second pendulum affect the angle at which the first pendulum has to be released in order for the second pendulum to flip?
- Draw a thin line lengthwise in the middle of all the aluminium pieces. This will aid in determining the angles of release during the experiment.
- Embed one end of the first rivet tightly in the wooden block and use the retort stand to clamp the wooden box tightly.
- Place the first pendulum of length 40.3 cm on the first rivet, followed by a small piece of plastic sheet (approximately 5 cm by 5 cm), followed by stick tack. The stick tack secures the first pendulum to the rivet and ensure the first pendulum does not fall off when swinging. This also ensures the safety of those nearby. The plastic sheet is placed between the first pendulum and stick tack to minimize friction should the rubbing of the first pendulum and stick tack occur.
- Put the second rivet thorugh the hole on the bottom of the first pendulum.
- On the second rivet, place another piece of plastic sheet, followed by the second pendulum of length 8cm, followed by yet another piece of plastic sheet, followed by stick tack to secure the second pendulum to the rivet. The first plastic sheet is placed between the first and second pendulums to minimize friction.
- Using a protractor, release the first pendulum at increments of 5 degrees, up till 170 degrees. Record the angle of release at which the second pendulum starts to flip. Release the first pendulum at the same angle five times to ensure reliability of results.
- Repeat steps 4-6 using 21.5 cm, 26.5 cm, 31.5 cm, 36.5 cm aluminium pieces as the second pendulum.
- From the table of results, make a conclusion on how the angle of release is affected by increments of 5 cm in length of the second pendulum.
Variables:
Independent variables:
- Length of first pendulum (for first experiment)
- Length of second pendulum (for second experiment)
Dependent variable:
- Angle at which the first pendulum has to be released in order for the second pendulum to flip
Constants:
- Weight of the first pendulum (ideally)
- Weight of second pendulum (ideally)
- Environmental conditions (such as wind)
- Amount of stick tack used to secure the first and second pendulums to the rivets
- The method of releasing the first pendulum (in this case pinching the first pendulum lightly to bring it to required angle before release)
Limitations:
Firstly, when varying the length of the first pendulum, the weight of the first pendulum has to be constant throughout. However, this is a difficult criteria to meet as the longer the aluminium bar, the greater its mass. Secondly, the angle of release when measured with a protractor may not be completely accurate owing to human error. Thirdly, to allow the pendulums to move without their movement being hindered, the rivets are not completely tightened. The pendulums may “wobble”, thus affecting the results of the experiment. Fourth, a double pendulum is theoretically a perpetual-motion machine, but this is not possible in real-life as there will always be the presence of friction, which will cause the double pendulum to stop swinging after some time. In conclusion, it is challenging to obtain completely accurate results as the double pendulum is a chaotic system, and as mentioned, the Choas Theory states that small variations in intitial conditions may cause complex behaviors in systems.
Assumptions:
The assumption was that only if the second pendulum flipped had the motion of the double pendulum started to become chaotic. However, this assumption was proven invalid after analysing the tables of results (which can be found at http://phoebe208sip.wordpress.com/, please see appendix). As mentioned earlier, small angles of release will cause the double pendulum to exhibit linear motion. However, linear motion may not be exhibited even if the second pendulum does not flip. I have thus deduced that the motion of the double pendulum is only linear if two identical double pendulums when released with the same initial conditions swing in exactly the same manner. Therefore it is incorrect to assume that the onset of chaos is when the second pendulum flips, as the onset of chaos may have occurred even before the double pendulum started to flip.This explains the deviation in motion of the double pendulum during various releases even though initial conditions were kept constant.
Conclusion:
Based on the table of results (see appendix), it can be concluded that:
- The length of the first pendulum does affect the angle at which the first pendulum has to be released in order for the second pendulum to flip, but the effects are unknown as the results are inconclusive.
- The length of the second pendulum does affect the angle at which the first pendulum has to be released in order for the second pendulum to flip, but the effects are unknown as the results are inconclusive.
The results are inconclusive because the double pendulum is a system that is inherently chaotic. The onset of chaos may have occurred even before the double pendulum started to flip. With reference to the Butterfly Effect, factors such as human error when releasing the first pendulum, the wobble of the pendulums on their rivets, or a slight unnoticeable breeze in the room can affect the chaotic motion of the pendulums. Thus, even if the initial conditions are kept as constant as the set-up can manage, extremely small variations in initial conditions can lead to complex behavior in the double pendulum and thus the motion of the double pendulum is unlikely to be exactly the same for each release. Therefore, a set-up with an extremely high level of technology and controllability is required to track the chaotic motion of the double pendulum. This leads me to realize that I do not have the means to derive conclusive results from varying any of the factors which affect chaotic motion of the double pendulum. I have thus decided not to do any follow-up experiments to determine how the Chaos Theory governs chaotic motion of the double pendulum. However, even though the results from this experiment do not explicity show the effect of the length of the pendulums on the critical angles of release, the length does affect the critical angle as length is a major variable of all pendulums, chaotic or not, and thus it can be assumed that length of both the first and second pendulums affect the angle at which the first pendulum has to be released in order for the second pendulum to flip.
This experiment has led me to discover that like the chaotic motion of the double pendulum, it is very difficult to track how factors such as the length of the tennis racquet, the length of the arm of the player and the angle of the arm of the player affect the accuracy of the return of the ball in the sports theory of tennis.
References
· Ceorote, A., 2012: Chaos Theory: An Introduction. Internet: <http://www.slideshare.net/anthaceorote/chaos-theory-an-introduction>.
- Chu-Carroll, M.C., 2009: Defining Dynamical Systems. Internet: < http://scienceblogs.com/goodmath/2009/06/12/defining-dynamical-systems/>.
Appendix
Please refer to my e-journal at http://phoebe208sip.wordpress.com/ for the tabulation of results, documentation of process, pictures and videos.
Glossary
DEFINITIONS
1. Carrier—A person or animal that harbors a specific infectious agent without discernible clinical disease and serves as a potential source of infection. The carrier state may exist in an individual with an infection that is inapparent throughout its course (commonly known as healthy or asymptomatic carrier), or during the incubation period, convalescence and postconvalescence of an individual with a clinically recognizable disease (commonly known as an incubatory or convalescent carrier). Under either circumstance the carrier state may be of short or long duration (temporary or transient carrier, or chronic carrier).
2. Communicable disease—An illness due to a specific infectious agent or its toxic products that arises through transmission of that agent or its products from an infected person, animal or inanimate reservoir to a susceptible host; either directly or indirectly through an intermediate plant or animal host, vector or the inanimate environment. (Synonym: infectious disease)
6. Communicable period—The time during which an infectious agent may be transferred directly or indirectly from an infected person to another person, from an infected animal to humans, or from an infected person to animals, including arthropods.
3. Contact—A person or animal that has been in such association with an infected person or animal or a contaminated environment as to have had an opportunity to acquire the infection.
4. Contamination—The presence of an infectious agent on a body surface, in clothes, bedding, toys, surgical instruments or dressings, or other inanimate articles or substances including water and food.
5. Disinfection—Killing of infectious agents outside the body by direct exposure to chemical or physical agents.
Concurrent disinfection is the application of disinfective measures as soon as possible after the discharge of infectious material from the body of an infected person, or after the soiling of articles with such infectious discharges; all personal contact with such discharges or articles should be minimized prior to such disinfection.
Terminal disinfection is the application of disinfective measures after the patient has been removed by death or to a hospital, or has ceased to be a source of infection, or after hospital isolation or other practices have been discontinued. Terminal disinfection is rarely practiced; terminal cleaning generally suffices, along with airing and sunning of rooms, furniture and bedding. Disinfection is necessary only for diseases spread by indirect contact; steam sterilization or incineration of bedding and other items is recommended after a highly infectious diseases.
Sterilization involves destruction of all forms of life by heat, irradiation, gas or chemical treatment.
6. Endemic—The constant presence of a disease or infectious agent within a given geographic area; it may also refer to the usual prevalence of a given disease within such area.
7. Epidemic—The occurrence in a community or region of cases of an illness (or an outbreak) with a frequency clearly in excess of normal expectancy.
The number of cases indicating presence of an epidemic will vary according to the infectious agent, size and type of population exposed, previous experience or lack of exposure to the disease, and time and place of occurrence.
8. Host—A person or other living animal, including birds and arthropods, that affords subsistence or lodgment to an infectious agent under natural (as opposed to experimental) conditions.
A transport host is a carrier in which the organism remains alive but does not undergo development.
9. Immune individual—A person or animal that has specific protective antibodies and/or cellular immunity as a result of previous infection or immunization, or is so conditioned by such previous specific experience as to respond in such a way that prevents the development of infection and/or clinical illness following re-exposure to the specific infectious agent.
Immunity is relative: a level of protection that could be adequate under ordinary conditions may be overwhelmed by an excessive dose of the infectious agent or by exposure through an unusual portal of entry; protection may also be impaired by immunosuppressive drug therapy, concurrent disease or the aging process. (See Resistance.)
10. Immunity—That resistance usually associated with the presence of antibodies or cells having a specific action on the microorganism concerned with a particular infectious disease or on its toxin.
Passive immunity is attained either naturally by transfer from the mother, or artificially by inoculation of specific protective antibodies. It is of short duration (days to months).
Active humoral Immunity, which usually lasts for years, is attained either naturally by infection with or without clinical manifestations, or artificially by inoculation of the agent itself in killed, modified or variant form, or of fractions or products of the agent.
11. Incubation period—The time interval between initial contact with an infectious agent and the first appearance of symptoms associated with the infection.
In a vector, it is the time between entrance of an organism into the vector and the time when that vector can transmit the infection.
12. Infected Individual—A person or animal that harbors an infectious agent and who has either manifest disease or inapparent infection (not seen physically, needs stool or blood test). An infectious person or animal is one from whom the infectious agent can be naturally acquired.
13. Infection—The entry and development (of many parasites) or multiplication of an infectious agent in the body of persons or animals.
14. Infectious agent—An organism that is capable of producing infection or infectious disease.
Infectivity expresses the ability of the disease agent to enter, survive and multiply in the host; infectiousness indicates the relative ease with which a disease is transmitted to other hosts.
15. Infectious disease—A clinically manifest disease of humans or animals resulting from an infection. (See Infection.)
16. Infestation—For persons or animals, the lodgment, development and reproduction of arthropods on the surface of the body or in the clothing. Infested articles or premises are those that harbor or give shelter to animal forms, especially arthropods and rodents.
17. Insecticide—Any chemical substance used for the destruction of insects, whether applied as powder, liquid, atomized liquid, aerosol or “paint” spray; residual action is usual.
The term larvicide is generally used to designate insecticides applied specifically for destruction of immature stages of arthropods (larvae).
18. Isolation—As applied to patients, isolation represents separation, for the period of communicability, of infected persons or animals from others in such places and under such conditions as to prevent or limit the direct or indirect transmission of the infectious agent from those infected to those who are susceptible to infection or who may spread the agent to others.
There are two basic requirements that are common for care of all potentially infectious cases:
• Hands must be washed after contact with the patient or potentially contaminated articles and before taking care of another patient; and
• Articles contaminated with infectious material should be appropriately discarded or bagged and labeled before being sent for decontamination and reprocessing.
19. Mortality rate—A rate calculated by dividing the number of deaths occurring in the population during the stated period of time, usually a year, by the number of persons at risk of dying during the period.
A total or crude mortality rate utilizes deaths from all causes, usually expressed as deaths per 1,000. A disease-specific mortality rate covers deaths due to only one disease and is often reported on the basis of 100,000 persons. The population base may be defined by gender, age or other characteristics. (Synonym: death rate)
20. Pathogenicity—The property of an infectious agent that determines the extent to which overt disease is produced in an infected population, or the power of an organism to produce disease.
21. QuarantIne—Restriction of the activities of well persons or animals who have been exposed to a case of communicable disease during its period of communicability (i.e., contacts) to prevent disease transmission during the incubation period if infection should occur.
- 1) Absolute or complete quarantine: The limitation of freedom of movement of those exposed to a communicable disease for a period of time not longer than the longest usual incubation period of that disease, in such manner as to prevent effective contact with those not so exposed. (See Isolation.)
- 2) Modified quarantine: A selective, partial limitation of freedom of movement of contacts, commonly on the basis of known or presumed differences in susceptibility and related to the danger of disease transmission. It may be designed to accommodate particular situations. Examples are exclusion of children from school, exemption of immune persons from provisions applicable to susceptible persons, or restriction of military populations to the post or to quarters. It includes: personal surveillance, the practice of close medical or other supervision of contacts to permit prompt recognition of infection or illness but without restricting their movements; and segregation, the separation of some part of a group of persons or domestic animals from the others for special consideration, control or observation; removal of susceptible children to homes of immune persons; or establishment of a sanitary boundary to protect uninfected from infected portions of a population.
22. Reservoir (of infectious agents)—Any person, animal, arthropod, plant, soil or substance (or combination of these) in which an infectious agent normally lives and multiplies, on which it depends primarily for survival, and where it reproduces itself in such manner that it can be transmitted to a susceptible host.
23. Resistance—The sum total of body mechanisms that interpose barriers to the invasion or multiplication of infectious agents, or to damage by their toxic products. Inherent resistance—an ability to resist disease independent of immunity or of specifically developed tissue responses; it commonly resides in anatomic or physiologic characteristics of the host and may be genetic or acquired, permanent or temporary. (See Immunity.) (Synonym: Nonspecific immunity)
23. Source of infection—The person, animal, object or substance from which an infectious agent passes to a host. Source of infection should be clearly distinguished from source of contamination, such as overflow of a septic tank contaminating a water supply, or an infected cook contaminating a salad. (See Reservoir.)
24. Susceptible—A person or animal not possessing sufficient resistance against a particular pathogenic agent to prevent contracting infection or disease when exposed to the agent.
25. Transmission of infectious agents—Any mechanism by which an infectious agent is spread from a source or reservoir to a person. These mechanisms are as follows:
1) Direct transmission: Direct and essentially immediate transfer of infectious agents to a receptive portal of entry through which human or animal infection may take place. This may be by direct contact such as touching, biting, kissing or sexual intercourse, or by the direct projection (droplet spread) of droplet spray onto the conjunctiva or onto the mucous membranes of the eye, nose or mouth during sneezing, coughing, spitting, singing or talking (usually limited to a distance of about 1 m or less).
2) Indirect transmission:
- a) Vehicle-borne—Contaminated inanimate materials or objects (fomites) such as toys, handkerchiefs, soiled clothes, bedding, cooking or eating utensils, surgical instruments or dressings; water, food, milk, and biological products including blood, serum, plasma, tissues or organs; or any substance serving as an intermediate means by which an infectious agent is transported and introduced into a susceptible host through a suitable portal of entry. The agent may or may not have multiplied or developed in or on the vehicle before being transmitted.
- b) Vector-borne—(i) Mechanical: Includes simple mechanical carriage by a crawling or flying insect through soiling of its feet or proboscis, or by passage of organisms through its gastrointestinal tract. This does not require multiplication or development of the organism. (ii) Biological: Propagation (multiplication), cyclic development, or a combination of these (cyclopropagative) is required before the arthropod can transmit the infective form of the agent to humans. An incubation period (extrinsic) is required following infection before the arthropod becomes infective. The infectious agent may be passed vertically to succeeding generations (transovarian transmission); transstadial transmissionindicates its passage from one stage of life cycle to another, as nymph to adult. Transmission may be by injection of salivary gland fluid during biting, or by regurgitation or deposition on the skin of feces or other material capable of penetrating through the bite wound or through an area of trauma from scratching or rubbing. This transmission is by an infected nonvertebrate host and not simple mechanical carriage by a vector as a vehicle. However, an arthropod in either role is termed a vector.
3) Airborne: The dissemination of microbial aerosols to a suitable portal of entry, usually the respiratory tract. Microbial aerosols are suspensions of particles in the air consisting partially or wholly of microorganisms. They may remain suspended in the air for long periods of time, some retaining and others losing infectivity or virulence. Particles in the 1- to 5-pm range are easily drawn into the alveoli of the lungs and may be retained there. Not considered as airborne are droplets and other large particles that promptly settle out (see Direct transmission, above).
- a) Droplet nuclei—Usually the small residues that result from evaporation of fluid from droplets emitted by an infected host (see above). They may also be created purposely by a variety of atomizing devices, or accidentally as in microbiology laboratories or in abattoirs, rendering plants or autopsy rooms. They usually remain suspended in the air for long periods of time.
- b) Dust—The small particles of widely varying size that may arise from soil (as, e.g., fungus spores separated from dry soil by wind or mechanical agitation), clothes, bedding or contaminated floors.
26. Virulence—The degree of pathogenicity of an infectious agent, indicated by case-fatality rates and/or the ability of the agent to invade and damage tissues of the host.
27. Zoonosis—An infection or infectious disease transmissible under natural conditions from vertebrate animals to humans. May be enzootic or epizootic (see Endemic and Epidemic)
Pathogens and Diseases Lesson Notes
Equilibrium
Homeostasis is the tendency of an organism or a cell to regulate internal conditions, usually by a system of feedback controls, to maintain equilibrium or stability within its internal environment, regardless of the outside changing conditions. A system in equilibrium may return to the same state of equilibrium if the disturbances are small (e.g. during exercise, perspiration bring body temperature down). However, large disturbances may cause it to escape that equilibrium and eventually settle in to some other state of equilibrium (e.g. when our body temperature increases, even though we perspire, the body temperature continues to increase).
Communicable and non-communicable diseases
A disease can modify or affect chemical reactions in the body and set it to disequilibrium. Non-communicable diseases are self-inflicted or created by environmental conditions, such as dietary deficiency diseases or cancers (e.g. scurvy, rickets, obesity, anorexia, CHD). Communicable diseases are due to agents such as viruses or bacteria, which are passed from one organism to another (e.g. cough, flu, malaria, athlete’s foot).
Types of pathogens
Pathogens can cause the disruption of the equilibrium of the body and the immune system helps to restore and maintain the equilibrium. Pathogens are organisms that cause disease and lives in or on another organism.
When they infect and organism, they destroy cells, produce toxins, interfere with normal functions and invokes immune response that, if excessive, harms the organism. To infect an organism, the pathogen must be able to survive the transmission from one host to another, enter the host and be virulent- the ability to overcome body defenses (through its own replication) and only need to be initially present in small numbers.
There are 5 different classes of pathogens.
- Bacteria
- Viruses
- Parasites
- Protozoa
- Fungi
Bacteria are microscopic, unicellular organisms which can cause cholera, whooping cough, tetanus, tuberculosis, salmonella and gonorrhea.
Viruses are sub-microscopic (too small to be seen under a microscope) but complex molecules that typically contain a protein coat surrounding a DNA or RNA core of genetic material. They can cause measles, mumps, rubella, common cold and rabies.
Parasites usually refer to small organisms (e.g. ticks, fleas etc.) that live on other organisms and cause them harm. Tapeworms can cause schistosomiasis.
Protozoa are single-celled parasites that may form large colonies. They resemble animals as they contain organelles not found in metazoan cells such as cilia and flagella used in swimming. They can cause malaria, African sleeping disease and leishmania.
Fungi are single or multi-celled organisms that produce spores and obtain food directly by absorption. They can cause athlete’s foot, fungal nail infection, ringworm etc.
Modes of transmission
- Direct à Contact
- Indirect à Vehicle borne (food and water), vector borne (mechanical and biological), airborne
Direct transmission
Direct and immediate transfer of infectious agents to a receptive portal of entry through which human or animal infection may take place. This may be by direct contact such as touching, biting, kissing or sexual intercourse, or by the projection of droplet spray onto eyes, nose and mouth when sneezing, coughing, talking etc.
Indirect transmission
Vehicle borne
Transmitted by means of contaminated inanimate materials (fomites) such as toys and bedding; water, food and biological products etc. by which an infectious agent is transported and introduced into a susceptible host.
Vector borne diseases- Mechanical
Include simple mechanical carriage by a crawling or flying insect through soiling of its feet or proboscis, or by passage of organisms through its gastrointestinal tract. This does not require multiplication or development of the organism.
Vector borne diseases- Biological
A biological vector develops an infected organism in its body and passes it along to its host (e.g. mosquito)
Airborne
In airborne/ droplets transmission, pathogens are suspended in the air and travel from source to host. The source can be humans, animals, soil, food and water. Transmitted by coughing, sneezing and vocalization.
Prevention and control
- Hygiene practices (sterilization, washing etc.)
- Physical protection (use of surgical face masks, gloves etc.)
- Control of vectors (fumigation, trapping and killing of vectors etc.)
- Control of microbes (use of antiseptics, antibiotics (only for bacteria) etc.)
- Vaccination
Body identifies antigen and produce antibodies. Antibodies bind to antigens and destroy. When infected again, antibodies are remembered. Injections (dead viruses/ attenuated (harmless but alive) viruses) allow the immune system to have memory of antigens. Booster jabs allow the immune system to continue to remember antigen configuration for fast production of antibodies when actually infected. Mortality rate. Incubation period. Bacterial infections only can be cured by antibiotics. Viral infection cannot, only meds to subdue. Narrow spectrum antibiotics (vancomycin> methicillin) (last resort because) destroy small range of bacteria but are very powerful. Broad range spectrum vice versa. Methicillin (powerful antibiotic)-resistant Staphylococcus aureus (MRSA). There is also VRSA.
Homeostasis Lesson Notes
Homeostasis Lesson Notes
Why are transport systems necessary?
Exchange of materials and energy occur at cellular level. Nutrients and oxygen move across the plasma membrane to the cytoplasm. Diffusion alone is insufficient over distances of more than a few millimetres. Therefore, the circulatory system solves this problem by ensuring that no substance must diffuse very far to enter or leave a cell. Large organisms require an effective transport system as the larger the organism, the smaller the SA: V ratio. This affects the rate of diffusion.
The circulatory system
The human circulatory system works with the respiratory (gaseous exchange), digestive (nutrients and wastes) and excretory (waste to kidney for removal) systems. The human circulatory system is made up of the cardiovascular system and the lymphatic system. The cardiovascular system is further divided into the pulmonary (lungs), coronary (heart) and systemic systems. The cardiovascular system is made up of blood, arteries and veins, capillaries and the heart.
The cardiovascular system
The heart
- Left/ right ventricle
- Left/ right atrium
- Tricuspid, mitral, pulmonary, aortic valve
- Chordae tendineae, papillary muscles
Consists of 2 ventricles, 2 atria and 4 valves. The ventricle pumps blood at high pressure out to the arteries. The pressure generated by the left ventricle is greater than that generated by the right ventricle as the systemic circuit is more extensive than the pulmonary circuit. The left ventricle is thus more muscular than the right ventricle.
The atria receive blood at low pressure from the veins. The pressure generated by the atria is less than that generated by the ventricles since the distance from atria to ventricles is less than that from ventricles to circulatory system. Thus, the muscle around the atria is thinner than the muscle around the ventricles.
Valves are important as they ensure that blood flows in the right direction. The tricuspid valve separates the right atrium from the right ventricle. It opens to allow deoxygenated blood to flow into the right ventricle. It closes as the right ventricle contracts, preventing blood from returning to the right atrium and forcing blood to exit thorough the pulmonary valve into the pulmonary artery. The bicuspid valve separates the left atrium from the left ventricle. It opens to allow oxygenated blood collected in the left atrium to flow into the left ventricle. It closes as the left ventricle contracts, forcing blood to exit through the aortic valve into the aorta. The pulmonary valve separates the right ventricle from the pulmonary artery. As the ventricles contract, it opens to allow the deoxygenated blood collected in the right ventricle to flow to the lungs. The aortic valve separates the left ventricle from the aorta. As the ventricles contract, it opens to allow oxygenated blood from the left ventricle to flow to the rest of the body. It closes as the ventricles relax to prevent the backflow of blood.
Chordae tendineae are tendons that connect papillary muscles to the tricuspid and mitral valves. They prevent flaps of the valves from being inverted into the atria. Papillary muscles of the heart serve to limit the movements of the mitral and tricuspid valves. They contract to tighten the chordae tendineae, which prevents inversion.
The heart wall is divided into three layers: the epicardium, myocardium, and endocardium. The myocardium is the muscular middle layer of the wall of the heart.
There are two phases of the cardiac cycle that are the diastole and systole phases. During the diastole phase, the atria and ventricles are relaxed and blood flows into the atria and ventricles. In the systole phase, the ventricles contract sending blood to the rest of the body.
Major arteries and veins
- Superior/ inferior vena cava
- Aorta
- Pulmonary artery
- Pulmonary vein
The superior vena cava brings deoxygenated blood from the head and upper body into the right atrium while the inferior vena cava brings deoxygenated blood from the legs and lower torso to the right atrium.
The aorta carries oxygenated blood from the left ventricle to the systemic circulation. The aorta is and elastic artery, and as such it is distensible. The stretching of the aorta gives potential energy that will maintain blood pressure during diastole.
The pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs. It branches into left and right pulmonary arteries, which deliver deoxygenated blood to the corresponding lung. The 4 pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart.
Blood vessels
Endothelium is composed of a simple squamous epithelial tissue.
Both arteries and veins have three similar layers. On the outside, a layer of connective tissue with elastic fibres allows the vessel to be distensible. The middle layer has smooth muscle and more elastic fibres. Smooth muscle is responsible for the contractibility of hollow organs such as vessels. The endothelial layer lines the lumen, which is a single layer of cells that minimize resistance to blood flow.
The flow of blood
Oxygenated blood enters the left atrium via the pulmonary vein. When the right atrium is filled up, it contracts, opening the bicuspid valve, allowing blood to travel to the left ventricle. The left ventricle contracts and the aortic valve opens, allowing oxygenated blood to travel through the aorta to other parts of the body. The aorta branches off into arteries, which then branch off into arterioles, which branch off into capillaries. By then, the speed of flow of the blood is reduced. Red blood cells have to travel through capillaries in a single file, allowing exchange of gases and nutrients between the blood and interstitial fluid that bathes the cells. Capillaries converge to form venules. Deoxygenated blood flows through venules, which converge to form veins, which converge to form the vena cava, which empties into the right atrium. When the right atrium is filled, it contracts, opening the tricuspid valve, allowing deoxygenated blood to travel to the right ventricle. The right ventricle contracts and the pulmonary valve opens, allowing blood to travel through the pulmonary artery towards the lungs. Blood is re-oxygenated at the lungs, after which the blood will travel through the pulmonary vein back to the left atrium of the heart.
The coronary system
The heart is composed primarily of cardiac muscle that continuously contracts and relaxes, thus it needs a constant supply of oxygen and nutrients. Coronary arteries carry oxygen and nutrient-rich blood to the cardiac muscle tissue. Larger vessels travel along the surface of the heart. Capillaries penetrate the heart muscle.
The components of blood
- Red blood cells
- White blood cells
- Plasma
- Platelets
RBCs (erythrocytes) are responsible for carrying oxygen to respiring cells and transporting carbon dioxide away from the cells. RBCs contain hemoglobin that binds oxygen molecules. Hemoglobin unloads oxygen when passing through capillaries. RBCs lack nuclei, allowing more hemoglobin to be packed and hence bind more oxygen. RBCs are disc-shaped, making it more flexible, allowing it to squeeze between the walls of capillaries, which have very narrow lumens. RBCs are bi-concave, which increases the SA: V ratio for rapid diffusion. RBCs only live 110-120 days, after which they are destroyed in the liver, where iron from the hemoglobin is salvaged and used by bone marrow cells to make new RBCs.
WBCs (leukocytes) are present in five major types. Their function is to fight infection and defend the body against invading pathogens by engulfing them. WBCs synthesize antibodies. They contain nuclei and are colourless.
Plasma is about 90% water. Plasma carries substances such as digested food, hydrogencarbonate ions (CO2 in different form), enzymes and nitrogenous wastes in transit from one part of the body to another. Enzymes are biological catalysts that speed up the rate of chemical reactions without themselves becoming chemically changed by the end of the reaction. Enzymes are protein in nature and are thus sensitive to pH and temperature. Different enzymes have different specific roles. Examples of substances in living systems that are protein in nature include enzymes, hormones, antibodies etc. Some examples of enzymes are insulin and glucagon, which are involved in the regulation of the blood glucose level in the body. Blood electrolytes are dissolved in plasma, which are important in maintaining osmotic balance of blood and buffering against pH changes. Antibodies help combat foreign agents. Fibrinogen proteins help repair damaged blood vessels. Functioning of muscles and nerves depend on the concentrations of key ions in interstitial fluid. This reflects concentrations in the plasma.
Platelets (thrombocytes) maintain homeostasis. They are produced in the bone marrow. They clot blood in case of injury, preventing pathogens from invading the bloodstream.
Blood related diseases
- Inability for blood to clot: Hemophilia, Von Willebrand Disease
- Problems with RBCs: Thalassemia, Sickle Cell Anemia, Hemolytic Anemia
- Leukemia
Hemophilia is a hereditary disorder, which impairs the body’s ability to control blood clotting. When a blood vessel is injured, missing coagulation factors prevent fibrin formations, which is necessary to maintain the clot. Thus, hemophiliacs bleed for a much longer time. VWD is caused by a deficiency of proteins required for platelet adhesion.
Thalassemia is a hereditary blood disease that reduces the rate of synthesis of one of the globin chains, which make up hemoglobin. This causes the formation of abnormal hemoglobin molecules, causing anemia. Anemia is a deficiency in hemoglobin, accompanied by a decrease in the number of RBCs. Anemic tire easily because of the insufficient amount of oxygen being supplied to the body. Sickle cell anemia is a genetic mutation that causes an abnormal type of hemoglobin, which changes the shape of RBCs. The sickle shaped cells deliver less oxygen to the body’s tissues and get stuck in small vessels easily, interrupting healthy blood flow. Hemolytic anemia is a condition where there are not enough RBCs in the blood due to their premature destruction. The bone marrow is unable to increase production of RBCs to make up for their premature destruction.
Leukemia is the production of abnormal WBCs, which do not function as normal WBCs. They are unable to fight infection and may attack other healthy cells, causing anemia and infections. Damage is done to the bone marrow when normal bone marrow cells are replaced by immature white blood cells, causing a decrease in platelet production, causing prolonged bleeding.
Predisposing conditions for heart disease
- Smoking
- Physical inactivity
- Elevated cholesterol levels
- Other factors
Nicotine in cigarettes stimulates excess production of adrenaline and noradrenaline, which causes blood pressure and heart rate to increase, forcing the heart to work harder. Carbon monoxide from cigarette smoke is irreversibly bound to RBCs, thereby reducing the oxygen carrying capacity of RBCs. Platelets in blood become sticky and clump together in vessels, which can damage organs.
Elevated cholesterol levels are associated with diets rich in saturated fats, which are low-density lipoproteins.
Risk of heart disease increases with age. Males are more susceptible. Excess body weight causes strain on the heart. Family history of heart problems can increase susceptibility. Stress increases adrenaline levels, which forces the heart to work harder.
Cardiovascular disease
- Formation of plaqueà Atherosclerosis à Stroke, coronary heart diseaseà Angina, heart attack
Lipid from low-density lipoproteins accumulates in the wall and fibrous tissue forms around the deposit in the vessel wall. Hard plaque is formed when calcium is deposited there, further narrowing the lumen. The endothelial lining of the vessel is damaged. The underlying smooth muscle proliferates (increases), thickening the arterial wall, increasing the risk of a blood clot in the vessel. Strokes are cause when a blood clot occurs in the cerebral arteries. Coronary heart disease, which causes angina and heart attacks, are caused when coronary arteries are blocked or narrowed, reducing blood supply to the heart muscles. Angina is a chest pain caused by reduced blood flow to the heart muscle, especially during exercise when there is not enough blood delivered to the heart muscles to meet demand. Heart attacks are caused by the deprivation of the heart muscle of glucose and oxygen, and poisonous wastes such as lactic acid will build up. Part of the heart muscle will stop contracting, depriving other parts of the body of glucose and oxygen.
Treatment for cardiovascular diseases
- Heart bypass
- Coronary angioplasty
Bypass surgery is the grafting (transplanting of tissue) of veins from other parts of the body around occluded coronary arteries, which restores adequate blood flow to affected area. Coronary angioplasty involves inserting and then inflating a small balloon in an occluded coronary artery. The plaque in the arterial wall is broken up, widening the lumen. A stent (metal coil) is permanently implanted to prop open a narrowed artery.
Investigation of Rate of Reaction
|
Surface area of strip/mm^2 |
Vol of strip/mm^3 |
SA:Vol ratio |
Height of bubbles at 60s/mm |
|
280 |
200 |
7:5 |
3.5 |
|
208 |
140 |
52:35 |
1.5 |
|
160 |
100 |
8:5 |
0.5 |
How Biological Diagrams are Drawn
Mealworm Experiment
Stage 1- Exploration and Discovery:
Observations:
– Brownish-yellow
– 6 legs in the front
– Many sections
– 2 antenna
– Tail is pointed
– Head is round
– Shiny and smooth texture
– Makes no sound
– 2 short things on the… abdomen
Questions:
– How do they respond to sound?
– How do mealworms prefer black or white surfaces?
– Do they respond to different smells?
– How do they react to vibration
Stage 2- Testing Ideas and Stage 3- Preliminary Experiment:
Answers to the 4 questions:
Aim of the experiment: To find out if they respond to sound
Hypothesis: Yes they do respond to sound
Materials: Catanet
Procedures:
1) Make the clicking sound with the catanets and record observations
2) Make the bells ringing sound and record observations
Variables:
Independent → The type of sound
Dependent → The mealworm reaction
Observation: It crawls away from the sound of bells but crawl towards the sound of the clacking
Data interpretation: They respond to sound
Assumptions made: Every mealworm reacts the same way to stimuli
Data reliability: Repeated experiments multiple times
Aim of the experiment: To find out if they prefer black or white surfaces
Hypothesis: They prefer black surfaces
Materials: Black and white sheet of paper
Procedures:
1) Place the mealworm on the middle of paper such that it can see both the black and white surfaces of the paper.
2) Record the mealworm’s reactions
Variables:
Independent →
Dependent → The mealworm reaction
Observation: When put between the two colors, both crawl quickly towards the black side of the paper on more than one occasion
Data interpretation: They prefer black surfaces
Assumptions made: Every mealworm reacts the same way to stimuli
Data reliability: Repeated experiments multiple times
Hypothesis: They react to smell.
Materials: a clear plastic tube and a clear plastic tube with a vinegar infused cotton ball
Procedures:
1) Place a mealworm at the end of each of the tubes.
2) Record the mealworm’s reactions
Variables:
Independent → the presence of the vinegar infused cotton ball
Dependent → The mealworm reaction
Observation: The mealworm placed in the clear plastic tube with a vinegar infused cotton ball, crawled away and stayed at the end which was furthest away from the vinegar infused cotton ball.
Data interpretation: They do not like the smell.
Assumptions made: Every mealworm reacts the same way to stimuli
Data reliability: Repeated experiments multiple times
Aim of the experiment: To find out if they respond to vibration
Hypothesis: Yes they do respond to vibration
Materials: tuning fork and rubber bung
Procedures:
1) Hit the tuning fork against the rubber bung
2) Place the tuning fork near the mealworms
30 Record observations
Variables:
Independent → The amount of vibration of the tuning fork
Dependent → The mealworm reaction
Observation: It crawls away from air vibrations.
Data interpretation: They respond to vibrations.
Assumptions made: It was because of the vibration they crawled away
Data reliability: Repeated experiments multiple times
Fossweb Lesson
WALKINGSTICK PREDATION: BUSH ENVIRONMENT ACTIVITY
Try the simulated population of walkingsticks that exhibit colour variation to investigate the impact of predation on the insects in 3 different environments.
Conduct predation interactions over 5 generations, collect population statistics, and graph the numbers of individuals with colour trait in each generation.
You should be able to see that the ratio of individuals with specific colour traits varies, depending on the colour of the environment in which they live.
Record the data of your findings in your journal.
You are a predator. You prey on walkingsticks. This is what the walkingstick looks like.
a. Open the walkingstick multimedia program to Level 1—Eat Insects.
b. Select the 30 Clicks to Eat Insects button.
c. Use your 30 clicks to eat as many as you can.
d. Then click the Results button.
e. Record your results in the table shown below in your journal.
f. Click Start Over and select 30 Seconds to Eat Insects. Eat as many insects as you can in 30 seconds.
g. Record your results in the table below in your journal.
| Brown | Green-brown | Green | ||
| 30 clicks | Eaten | 8 | 9 | 13 |
| Survived | 8 | 7 | 3 | |
| 30 seconds | Eaten | 10 | 10 | 10 |
| Survived | 6 | 6 | 6 |
Write responses to these items in your journal.
- Which color of walkingstick was easiest to find? Which was hardest? Why do you think that was the case?
As I chose a bush environment, the brown walkingsticks were the easiest to find as they were less camouflaged with the green surroundings. THe hardest to find were the green walkingsticks as they camouflaged well with the environment.
- Which color of walkingstick survived best when there was a time limit on feeding? Why do you think that color survived best?
The green walkingsticks survived best. I think this is because the time limit prevents the predator from looking hard enough to spot the well-camouflaged green walkingsticks.
- Discuss the results of the walkingstick predation in terms of adaptations.
ENRICHMENT: NEW BREEDING RULE ACTIVITY
a. Open the walkingstick multimedia program to Level 3—New Breeding Rules.
b. Select to Eat Insects for 30 seconds.
c. Choose the Population Size at 48.
d. Then click the Continue button.
e. Choose the bamboo environment and beging “eating” the walkingsticks
f. Click on Results when the time runs out. Continue to the next generation and repeat for 5 generations.
g. When you have completed all 5 generations, click on the Print results. Enter your name and class.
h. When the dialog box pop up don’t print but “save as pdf”. You will be able to save a copy of the table in your desktop.
Glossary
- Independent variable: variable which you change in an experiment
- Dependent variable: measure of the independent variable
- Control variable: every other variable the experiment may have, and these must be kept constant.
- Qualitative variables: variables where an amount is given but without exact numbers, e.g. Liz has MORE dogs than Sue
- Quantitative variables: variables where an exact numerical value is expected, e.g. Liz has 4 dogs
- Hypothesis: a tentative statement about the relationship between two or more variables
- Eukaryotes: any of the single celled or multicellular organisms whose cell contains a distinct, membrane-bound nucleus
- Prokaryotes: any of the group of organisms primarily characterized by the lack of true nucleus and other membrane-bound cell compartments
- Taxonomy: taxonomy is the science of naming, describing and classifying organisms and includes all plants, animals and microorganisms of the world
- Taxon: a taxonomic category as a species or genus
- Binomial nomenclature: the system of nomenclature using two terms, the first one indicating the genus and the second the species
- Abiotic factors: non-living factors such as temperature
- Biotic factors: of or related to life, e.g. species, food web
- Habitat: the natural home or environment of an animal, plant, or other organism
- Ecosystem: a biological community of interacting organisms and their physical environment
- Population: a particular section, group, or type of people or animals living in an area or country
- Community: all of the groups of animals or plants living together in the same area or environment and usually interacting with each other
- Niche: the specific area where an organism inhabits OR the role or function of an organism or species in an ecosystem OR the interrelationship of a species with all the biotic and abiotic factors affecting it
- Biome: climatically and geographically defined as similar climatic conditions on the Earth
- Biosphere: the regions of the surface and atmosphere of the earth or other planet occupied by living organisms.
- Pyramid of numbers: a pyramid shaped visual which shows the amount of organisms in the chain
- Pyramid of biomass: a pyramid shaped visual which shows the biomass (mass of living things) of each organism in the chain
- Biomass: the total mass of all living material in a specific area, habitat or region.
- Predator-prey relationship: an interaction between two organisms of unlike species in which one of them acts as predator that captures and feeds on the other organism that serves as the prey
- Commensalism: a form of symbiosis between two organisms of different species in which one of them benefits from the association whereas the other is largely unaffected or not significantly harmed or benefiting from the relationship
- Ammensalism: a symbiotic relationship in which one organism is harmed or inhibited and the other is unaffected, e.g. the shading out of one plant by a taller and wider one
- Mutualism: a symbiotic relationship between individuals of different species in which both individuals benefit from the association
- Symbiosis: a relationship between different species where both of the organisms in question benefit from the presence of the other.
- Parasitism: a form of symbiosis in which one organism (called parasite) benefits at the expense of another organism usually of different species (called host). The association may also lead to the injury of the host.
Biology Notes 