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MAINTAINING A BALANCE: Homeostasis: is the process by which organisms maintain a relatively constant or stable internal environment. RBC – 7-8 micrometres WBC – 8-12 micrometres Fish remove waste(ammonia- HIGH TOXICITY) across their gills Mammals excrete urea from kidneys (moderate toxicity) Insects excrete uric acid (LOW TOXICITY) from gut. BLUEPRINT OF LIFE: Practicals: #1 – The peppered moth #2 – The pentadactyl limb #3 – History of the theory of evolution #4 – Modelling natural selection (green and white toothpicks) #5 – Monohybrid Crosses- using Punnet squared #6 – Pedigrees #7 – Modelling Meiosis #8 – Solving Problems: Sex-linkage and co-dominance #9 – The effect of the environment of phenotype (flamingo, Siamese cat and hydrangea research) #10 – A model of the polypeptide synthesis. The effects of changes in the environment: Changes in physical conditions: temperature, availability of water. Changes in chemical conditions: Salts and elements such as iron. Competition for resources: within and between species. Food, space, mates. Evidence for the theory of Evolution: Palaeontology (fossil record) Biography (distribution of species – both fossil and living) Comparative embryology (similar embryos of vertebrae’s suggest common ancestor) Comparative anatomy (e.g. pentadactyl limb) Biochemistry (comparison at a molecular level) Homologous feature: feature that appears in different organisms that shows and ancestral pattern Analogous feature: a body structure found in different (unrelated) organisms that have a similar function. Bat and fly wing Natural Selection: Variation within a species Not all individuals reproduce Well suited organisms survive (survival of the fittest) Favourable variations are passed on to the offspring, and become more and more common in a population. ISOLATION. For new species to evolve, natural selection must work in conjunction with isolation of groups within a species. If the two groups can no longer interbreed and are no longer subject to the same environment, they could become a different species. CONTINENTAL SEPERATION ADAPTIVE RADIATION: When organisms spread into new habitats over millions of years they adapt to the new environment. Adaptive radiation can lead to divergent and convergent evolution. DIVERGENT EVOLUTION: A species descend from a common ancestor and become less similar as they adapt to their new environments. CONVERGENT EVOLUTION: Unrelated species evolve similar characteristics because they live in similar environments. Shark and Dolphin DARWIN AND WALLACE: Darwin and Wallace believed in natural selection and isolation, and the formation of a new species as a result of these things. GREGOR MENDEL: Cross-pollinated purebred plants w/ particular traits and observed the outcome. HE noticed a 3:1 ration in the offspring two generations down. PEOPLE IGNORED HIM. He concluded: The inheritance of each trait is determined by genes that are passes on to descendants unchanged An individual inherits one such gene from each parent for each trait. A trait may not show up in an individual, but can still be passed on to the next generation. Mendel’s law (the law of segregation): inherited characteristics are controlled in pairs, in genes. They come from each gamete. Mendel’s law of independent assortment: each allele in inherited independently of other gene pairs during gamete formation. GARROD: first to connect human disorder with Mendel’s law of inheritance. He studied arthritis. Published the first account of a case of recessive inheritance in humans SUTTON AND BOVERI: Discovered the role of chromosomes. Boveri worked on sea urchins and showed that the chromosomes were not all the same. Sutton worked on grasshoppers and showed that they were distinct entities. He said that even though they duplicate and divide, the remain a distinct structure. Both relied on Mendel’s work to understand their own. FORMATION OF GAMETES: Haploid gametes form through meiosis Contain half the normal (diploid) number of chromosomes Homologous pairs of chromosomes line up during meiosis and then are separated during cell division. When the homologous pairs line up some genetic material is exchanged before the pairs are separated.(‘crossing-over’). MONOHYBRID CROSS: when two individuals which are heterozygous for a single characteristic are cross-bred. Locus: the specific place on a chromosome where a gene is found. Haploid: A cell with only one of each gene. NOT ALL GENETIC CROSSES GIVE A PURE MENDELIA RATIO. IT DEPENDS ON INTERATIONS BETWEEN THE ALLELES CONCERNED. Incomplete dominance: both are expressed at the same time (pink instead of red or white flowers) Co-dominance: both are expressed, but there is not blending (splotchy cat fur) Sex-linkage: Genes that are on the X or Y chromosomes (haemophilia). If men get one dodgy X chromosome, they are screwed! Women have a back-up which may be dominant and override the dodginess. GENOTYPE + ENVIROMENT = PHENOTYPE. MORGAN: Discovered sex-linkage in fruit flies. Eye colour. White is recessive, Red is dominant. Females are more likely to have red eyes. WATSON AND CRICK: Suggested double-helix structure of DNA and the pairing of bases. FRANKLIN: Provided the scientific evidence upon which Watson and Crick based their double helix model. Used X-ray diffraction and found the image of DNA. Wilkins initially gave her the DNA to X-ray, but he didn’t like her (sexism, of course). WILKINS: Stole the image of the DNA from Franklin and showed Watson and Crick. The DNA in the nucleus never leaves. The sequence of the polypeptide is decided by the DNA. mRNA codons form as they match up with the corresponding codon in the nucleus. They leave the nucleus and meet up with the tRNA anticodon. A ribosome reads the section of RNA and connects amino acids to form a polypeptide chain. Transcription: the process of transcribing (writing down) the DNA information and producing and mRNA molecule. Translation: the process of decoding the information in mRNA into a polypeptide chain. RNA is similar to DNA except that the base T is replaced by U (uracil). RNA is single-stranded. BEADLE AND TATUM: Concluded that each defective enzyme there was one gene on one specific area of the chromosome that had been mutated by irradiation. ‘One-gene-one-enzyme’ theory. Discovered mutants. Genes are responsible for the production of specific proteins. Changes in DNA sequences: Wrong proteins may be produced. An example of this is Sickle-Cell anaemia. They RBC are the wrong shape, and cannot carry oxygen. GRADUALISM PUT FORWARD BY DARWIN. PUNCTUATED EQUILIBRIUM PUT FORWARD BY ELDGRIDGE AND GOULD (long periods of stability followed by rapid short changes) A SEARCH FOR BETTER HEALTH: Practicals: #1 – exposing agar plates (fingers and 5, 10 and 15 minutes) to the air and incubating. #2 – fish tank water, tap water, distilled water and bread on agar plates. Incubated and looked for fungus and bacteria. All grew bacteria, none grew fungi. #3 – Pasteur’s experiment: boiled broth and left in two flasks with a straight, and an s-bend stopper. Straight stopper grew fungi, s-bend remained sterile. #4 – Infectious disease study: Syphilis #5 – Epidemiology + graphs. #6 – Diary entry of someone with a non-infectious disease #7 – Australian quarantine and Inspection Service Normal processes in the body that maintain health: The function of genes Mitosis Cell differentiation Cell specialisation Correct gene expression allows for maintenance and repair of body tissues and this maintains health. Two genes that are of great important to the maintenance of cellular processes: Proto-oncogenes: produce proteins that speed up cell division. Tumour Suppressor Genes: produce proteins that slow down cell division. PASTEUR AND KOCH: Pasteur – discovered that vats with good alcohol contained yeast cells that were round and reproducing. When lactic acid formed instead of alcohol, he observed small rod-like microbes mixed with the yeast. In this, he discovered that yeast caused the fermentation of sugar into alcohol and that containing microorganisms made the fermentations sour. This went against the simple ‘sugar broken down into alcohol’ theory of the time. This turned into the ‘germ theory of disease’. Pasteurisation of wine beer and milk, used today, were because of him and his discovery of living things role in fermentation. Pasteur’s experiment: To disprove spontaneous generation. He heated two flasks with stock inside, one was straight, the other swan-necked. He heated until they were sterile, and watched as the straight necked flask became reinfected with bacteria and mould, while the swan-necked one remained sterile. Koch – investigated Pasteur’s theory that microorganisms caused disease. He isolated the bacteria from the blood of animals dying from anthrax. He grew the bacteria and isolated it from other bacteria mixed with it. He injected it into healthy mice and they developed anthrax. He made criteria needed to prove that a particular organism causes a particular disease: The organism believed to be the cause of the disease must always be present when the disease occurs. The organism must be isolated from the host and grown in a pure culture. Organisms from the pure culture, when inoculated into healthy, suitable, susceptible hosts must cause the disease. The organisms must be re-isolated, grown in a pure culture and compared with the organism first injected. The immune system is designed to recognise cells/ substances as ‘self’ or ‘non-self’. Antigen: molecules that trigger an immune response. (includes toxins produced by bacteria) Pathogen: an organism (or virus or prion) that causes a disease to occur in another organism Infectious Disease: a disease caused by a pathogen. Antibiotics: are chemicals made by microbes that can kill or stop the growth of bacteria and fungi. (E.g. penicillin) Antibodies : proteins produces by plasma B-cells in response to a specific antigen. Bind to antigens in a ‘lock-and-key’ fashion. Y-shaped. Role: recognise and bind to antigen. They are specific to each antigen. Interleukins: chemicals secreted by the T-cell to stimulate B-cell function. ‘Selective Toxicity’ – chemicals that could destroy or inactivate bacterial cells, but not the animal host’s cells Immunosuppressive drugs: given to someone who has received a transplant to prevent their immune system from destroying the foreign organ. Passive immunisation: involves injecting the antibodies themselves into a person and does not activate the immune system. Only short-term immunity. Active immunisation: stimulated a person to make his or her own antibodies. Vaccination: a method of introducing a dead or weakened antigen into the body to produce an immune system response. Epidemiology: The study of the factors involved in the occurrence, prevalence and spread of disease within a population. Types of pathogens: Prions – infective proteins. No DNA or RNA. Not regarded as cells. Not ‘alive’. Causes degeneration of brain tissue. Mad-cow Disease. CJD Viruses – Very small. Reproduce by taking over a host and hijacking other cells. Not cells. DO HAVE DNA AND RNA. No cures, but vaccination reduces prevalence. Measles, mumps, polio, chicken pox, AIDS, Myxoma virus. Bacteria – prokaryotic (no membrane bound organelles). (0.5-5 micrometres) Single strand of DNA. Present in air, soil, water, and many body parts. Reproduce by binary fission. Produce toxins. Classified by shape. Bubonic plague, diphtheria, gonorrhoea, syphilis, tetanus. Protozoans – single celled eukaryotic microscopic organisms. (2-1000 micrometres). Some are pathogenic. Malaria, African sleeping disease. Fungi – Eukaryotes. Can be unicellular (yeast) or multicellular (mushrooms). Cause plant diseases. Leaf curl, black-spot, powdery mildew, rust, rot. Fungal animal diseases are less serious. Ringworm, thrush, athlete’s foot. Macro-parasites – Visible to naked eye. Live in or on host. Flatworms, roundworms, lice, fleas, ticks, mites, aphids, mites, borers. A vector is something that transports and transmits a pathogen. E.g. a mosquito Malaria: Malaria is caused by Plasmodium; a protozoan. It infects the liver cells, then after 2-4 weeks, bursts out and infects the blood, always multiplying. Symptoms include shivering, fits, high fever, headache, nausea and profuse sweating. This occurs every 48-72 hours. Destruction of RBC causes anaemia. FLEMMING: Discovered penicillin, a chemical produced by a fungus, which could kill bacterial cells. FLOREY AND CHAIN: Discovered that penicillin was effective in the treatment of infectious disease, and also developed a method for its production in large quantities. DEFENDING THE BODY 1ST LINE OF DEFENCE: entry preventing barriers. Mechanical and physical barriers to substances and organisms Skin – perfect barrier if not broken Mucous membranes Cilia – minute hairs lining respiratory surfaces. Enzymes Natural microbial flora Complement proteins Chemical barriers – e.g. acidic stomach 2ND LINE OF DEFENCE: non-specific immune response. If substances or pathogens get past the first line and enter deeper tissue, this line is triggered Inflammation – chemical signals cause inflammation (e.g. histamine). Causes rapid and increased blood supply to area, which brings white blood cells. Histamine also causes the walls of blood vessels to become more permeable and this means phagocytes can escape from the blood vessels and go directly to the wound site to engulf the invaders before they get into the blood. Phagocytosis - Phagocytes (white blood cells - natural killer cells) attack and engulf foreign substances. This is not always successful as some pathogens repel phagocytes and some bacteria cannot be grasped. Sometimes they just escape before they are completely destroyed. Pus is a mixture of dead phagocytes, bacteria, tissue fluid and damaged body cells. Granulocytes and Macrophages (white blood cells that are continuously in search for foreign antigenic molecules). Lymph system – acts as a filter, removing microbes from fluid that returns to the blood. White blood cells are concentrated in lymph nodes and are immediately activated when an antigen is detected. Cells die to seal off pathogen – after phagocytes have been released from the blood, a cluster of cells surround the invaders and damaged tissues and seal off the area. Many cells are sacrificed to make sure the pathogen and broken skin are sealed off. 3RD LINE OF DEFENCE: specific immune response. Learned and specific!!!!! Antibodies Lymphocytes – white blood cells that arise from stem cells in the bone marrow by mitosis. Some become T-cells in the thymus and circulate in the blood. T-cells – control cell-mediated response and stimulate the production of antibodies by B-cells (helper T-cells). They direct and regulate immune responses. Mature in the thymus gland. Killer T-cells directly attack and destroy infected, abnormal and nonself cells. Helper T-cells attract macrophages and activate phagocytes. Suppressor Tcells inactivate T and B cells after an infection has occurred. B-cells –Mature in bone marrow and produce antibodies. Differentiate into plasma cells which make antibodies, and B-memory cells that are stored in lymph nodes. The memory cells change to plasma cells when they are exposed to a remembered antigen. Microflora is a mixture of organisms - usually bacteria- that is regularly present in humans. They are microscopic organisms that live on or in the body without causing disease. An imbalance of microflora causes disease. E.Coli, chlamydia Memory B and T cells are produced when a person is immunised. They ‘remember’ and can recognise previous antigens and act to quickly destroy further infections. How white blood cells (leucocytes) separate: Phagocytes white blood cells lymphocytes B-cells or T-cells B-cells differentiate when they are exposed to antigens. They become active plasma cells, or memory B-cells. EDWARD JENNER: used cowpox as a vaccine for smallpox. MACFARLANE BURNET: Developed the theory of immunisation called ‘clonal selection theory’. This theory explained how the immune system is able to combat an antigen so quickly and specifically once it enters the body for the second time. He explained that several million B memory cells circulated the body at any one time, and each one was programmed to produce an antibody specific to an antigen. They were created in response to the exposure to antigens during foetal development or later in life. Each memory cell has receptors on its membrane which are specific for the antigen. When re-exposed, they rapidly divide and produce plasma cells which also divide and make an abundance of antibodies which fight the antigen. Non-infectious diseases: Inherited diseases. Cystic fibrosis, Down’s syndrome, haemophilia. Nutritional deficiencies. Arthritis, heart disease, anorexia. Environmental diseases. Burns, cuts, cancer, drug addiction, alcoholism, frostbite. Australian Quarantine Inspection Service: Preventative measure. They keep foreign pests and diseases from entering into Australia. They must be efficient and highly effective in order for it to work. The word quarantine means 4o days. COMMUNICATION: Practicals: #1 - Detecting the Electromagnetic spectrum. Rainbow + using prism to separate light #2 – Mammalian eye dissection Stimulus Receptor Messenger Effector Response Stimulus: external or internal trigger. E.g. light, heat, chemical. Receptor: means of detecting stimulus. E.g. nerve ending, single receptor cell. Messenger: the path via which the information about stimulus is transmitted E.g. nerve pulses Effector: means of carrying out response. E.g. muscles, glands Response: the action as a result of the stimulus. E.g. moving arm away from heat Sensory receptor cells within each sense organ receive and convert specific stimuli into electrochemical impulses which and strung along sensory nerves to the brain. The nervous system sends rapid, brief signals using electrical impulses along fixed paths. The endocrine system sends slow, long-lasting signals using hormones through the blood. Mechanoreceptors: stimulated by all forms of mechanical energy. E.g. pressure, touch, sound Nociceptors: or ‘pain receptors’, but pain is a sensation rather than a stimulus so the term is wrong. Thermoreceptors: respond to heat or cold, helping to regulate body temperature. Send signals to the hypothalamus. Chemoreceptors: E.g. osmoreceptors. Osmoreceptors in the mammalian brain detect changes in the solute concentration of the blood (osmolarity) and stimulate both thirst and reabsorption in the kidneys. Gustation is ‘taste’. Electromagnetic Receptors: Detect various forms of electromagnetic energy, such as light, electricity, or magnetism. They are often organised around the eyes and are responsible for vision. Many animals migrate using the magnetic field lines of the earth to help orient themselves. Animals detecting the electromagnetic spectrum: Vampire bat – Infrared sensor on nose tuned to the temperature of blood. Copper-mouth snake – infrared detection in pit organs below eye Bees – eyes sensitive to blue, green and UV light. Piranha – eyes can see infrared. The eye and light: The light is admitted into the eyes by the cornea, which begins to refract the light. The light passed through the aqueous humour, then the pupil, then the vitreous humour, before reaching the retina. Light is sharply focused on the retina by the lens Photoreceptors of the retina detect light signals and convert them into electrochemical impulses. This information is carried to the brain via the optic nerve. Structure of the eye: Part of eye: Structure: Function: Conjunctiva Protects the cornea against friction Cornea Sclera Choroid Retina Iris Pupil Delicate membrane that covers the surface of the eye and the inside of the eyelids Curved transparent layer at the front of the eye. Continuous with the cornea but not transparent. The outside layer, white of the eye. Made of tough fibres. Lies on the inside of the sclera. Middle layer of the eye. Thin black membrane containing pigment and blood vessels. Innermost layer of the eye. Lines the back of the eyeball and contains the light-sensitive cells (photoreceptors called rods and cones) and nerve fibres. Coloured (has pigments) part at the front of the eye. Composed of muscles. Circular opening in the centre of the iris, thus the pupil is not really a structure. The size of the pupil is controlled by the iris. Admits light into the eye and refracts light. Protects the eyeball against mechanical damage. Maintains shape Nourishes retina (blood vessels) and prevents internal reflection (the pigment absorbs stray light) Detects light and converts it into electrical impulses that travel via the optic nerve to the brain. Contracts and dilates to regulate the amount of light entering the eye. Admits light to the back of the eye. Lens A flexible, curved transparent structure. Aqueous Humour Watery liquid Vitreous Humour Ciliary Body More viscous, jelly-like fluid Optic Nerve Contains suspensory ligaments and Ciliary muscles. Bundles of sensory neurons. A bundle of 1.2 million neurons. Allows light to enter the rear of the eye; refracts light to allow fine focusing on the retina. Maintains the shape of the front of the eye and transmits and refracts light. Also brings nutrients to the lens and cornea. Maintains the shape of the back of the eye. Transmits and refracts light. Ligaments hold the lens in position and the Ciliary muscles alter the shape of the lens. Collects nerve information from the retina and transmits signals to the visual cortex of the brain. Myopia and Hyperopia: Myopia is short-sightedness (can see near objects). Object is over focused. Image falls before retina. Eyeball may be too elongated Refractive power of cornea may be insufficient Lens may not become flat enough. Concave glasses help (separate light out) Hyperopia is long-sightedness (can see far objects). Object is under focussed. Image falls behind retina. Eyeball that is too rounded Lens is too flat. Refractive power of the cornea is too great for the shape of the eye. Convex lenses in glasses are helpful. (light is focused more)