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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:
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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:
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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:
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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:
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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:
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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:
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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:
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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:
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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
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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
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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
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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
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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!!!!!
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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
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white blood cells
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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:
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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:
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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:
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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.
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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.
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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)