Biology Summary Notes

1. Maintaining a balanceMost organisms are active in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates.

Enzymes Role

o Acceleration of chemical reactionso Lowering of activation energyo Action on specific substrates

Chemical Compositiono Globular proteins made up of protein and amino acids folded into a #D

shape Specificity

o Lock-and-key methodo Induced fit model, shape of active site changes to accommodate the

substrate, saturation point – highest rate the enzyme can work at with substrates

Effects of:o Temperature – if it heats up hydrogen bonds break and alter shape, the

enzyme denatures, excessively cold the enzyme slows or stops but can be reversible

o pH – if pH is altered dramatically enzyme will denatureo substrate specific – each enzyme catalyse one specific substrate, e.g.

amylase acts on starch changing it to glucose rennin acts on protein in milk to curdle catalase acts in most living things to convert toxic hydrogen

peroxide to harmless water and oxygen gas Why homeostasis is important

o pH and temperature: low temperatures can cause cater in the cells to freeze, this brings about changes in concentration of solutes in cytoplasm, which in turn affects pH and osmotic balance of the cell. Cell damage or organelles rupture. Very high temperatures cause both enymes and other proteins to denature.

o Metabolites: chemicals working in metabolism rely on ATP energy in cells, otherwise a ripple effect happens and other metabolic activity will be affected

o Water and salt concentrations (osmotic balance): reactants must be dissolved in water for a chemical reaction to happen, hence the concentration and balance of water and salt is important.

o An absence of toxins; otherwise it will affect pH

pH pH is a scale related to the concentration of hydrogen ions in a solution pH value of 0-6 is acidic, 7 is neutral, 8-14 is basic

Homeostasis Process by which organisms maintain their internal environment, despite changes in

their behaviour and the external environment. “internal equilibrium by adjusting their physiological processes.” They control:

Need to add examples and pracs

o Body temperature and metabolic rateo Concentration of dissolved salts and mineralso Concentrations of nutrients, such as glucose in the bloodo Input and output of watero Nitrogenous wasteo Oxygen and carbon dioxide concentrationso removal of foreign substances, damaged cells

2 stage process (feedback process – self-regulating mechanism that maintains balance or homeostasis)

o Nervous system and the endocrine system

o The central nervous system and peripheral nervous system provide rapid coordination of internal organ systems, detects and responds environmental changes.

o Organisms live in ambient temperatures ranging from less than 0 degrees (e.g. bacteria in snow) to 100 degrees (bacteria in undersea boiling springs)

o Individual organisms cannot survive this range of temperatures, generally 0-45 degrees.

Ectothermso Cannot generate their own body heat or maintain a constant body

temperature. Rely on ambient temperature, e.g. environmental temperatures are low, the activity and metabolism of the ectotherm is low. Most animals are ectotherms.

o They can adapt structurally, functionally or behaviourally to their environment. Example, desert lizard in central Australia:

Avoid high temperatures, seek shelter or burrow Increase body temperature by basking in the sun in the morning Raise body away from surface to allow convection currents to carry

heat away, right angle to the sun-lowered volume area Changing colour

Endothermso Can generate their own body heat and so generally maintain a constant

body temperature – metabolic processes and mechanisms such as fat layers,

blubber, hair, fur, feathers, reduced blood flow to the extremities, hibernation, burrowing, nocturnal habit and migration. Decreasing surface area to volume ratio.

o Example, red kangaroo Sheltering during the heat of the day Licking forelimbs to increase heat loss by evaporation of water Panting, sweating, pulls tail in (SA/V)

Plantso Need certain temperatures for growth and germination of seeds.

Ability to orient leaves vertically (SA/V), support convective cooling Drop their leaves if it gets too cold Germination Budding in heat Close stomates to reduce water loss

Plant and animal transport of dissolved nutrients and gases in a fluid medium Form Substances are carried in, in mammalian blood

o Carbon dioxide – bicarbonate ions – plasmao Oxygen – oxyhaemoglobin – red blood cellso Water – blood plasmao Salts – dissolved as ions – plasmao Lipids – glycerol and fatty acids – plasma o Nitrogenous wastes – uric acid/ammonia – ureao Other products of digestion – amino acids, glucose – dissolved and

suspended in plasma

o Size of red and white blood cells at the magnification of 1000x

Red (no nucleus) – 5 to 9 microns, White – 9 to 15 microns (no nucleus)

Haemoglobino Complex molecule that gives blood it’s colour, enables red blood cells to

carry oxygen.

Dissolved carbon dioxide in water prac

o Protein portion consists of peptide chains, each with an iron-containing haeme group

o Oxygen carried in a loose combination called oxyhaemoglobino Adaptive Advantage

Oxygen readily reacts to form an acid and therefore can only be held in water in solution, this way would limit the amount of oxygen

Haemoglobin allows increased capacity of oxygen to be carried in blood.

Easily combines and releases oxygen Haemoglobin dissolved in plasma can upset the osmotic balance Red blood cells without nucleus – more room for haemoglobin,

oxyhaemoglobin – 4 units Increases rate and efficiency of oxygen intake and transport

o Technologies to measure oxygen saturation and carbon dioxide concentrations in blood

ABG (arterial blood gas) analysis measures the amounts of oxygen and carbon dioxide in the blood.

Pulse oximeter – non-invasive, continuous monitoring of oxygen saturation levels.

Used to assess respiratory diseases and other conditions that may affect the lungs, such as emphysema, pneumonia and silicosis and/or to manage patients receiving oxygen therapy, mechanical ventilation or anaesthesia.

Arteryo Carry blood away from the heart, o thick, muscular wallso No valveso Carry oxygenated blood (except for pulmonary artery)o Blood is pumped

Veinso Thin-walledo Valves to prevent back-flowo Carry blood towards hearto Carries deoxygenated blood (ex. Pulmonary vein)o Blood under low pressure, body muscles

Capillarieso Thin walled, often one cell thicko Carry blood between arteries veins and body cells

Chemical Composition throughout the bodyo Deoxygenated right atrium right ventricle lungs left atrium left

ventricle aorta body tissuesChemical Composition Tissues which change occursBlood receives oxygen, carbon dioxide released

Lung tissue

Blood receives carbon dioxide, oxygen released

General body tissues such as skin tissue

Water diffuses into blood, some substances such as alcohol, pass into stomach tissue from the blood through the walls of the stomach

Stomach tissue

Need to add examples

Digested foods, amino acids, glucose – diffused into the blood, go straight to the liver. (Fatty acids diffuse into lymph)

Small intestinal tissue

Glucose is added or removed. Poisonous or unwanted substances removed. Excess amino acids removed and converted to urea, which is then added to the blood.

Liver tissue

Water, salts and vitamins are absorbed in the large intestine and pass into the blood

Large intestinal tissue

Urea, excess water, and salts are removed from the blood to be excreted

Kidney tissue

Hormones are secreted directly into the blood stream

Endocrine tissue

Products of donated blood and useso Red blood cells

Increase amount of oxygen carried to body’s tissues (anaemia)o Platelets

Essential for blood clotting (cancer, people undergoing cancer therapy)

o Plasma Liquid portion containing immunoglobins. Clotting disorders, such as

haemophilia, adjust osmotic pressureo Immunoglobins

Infection-fighting, people whose immune systems are not working properly, AIDS

o Cryoprecipitate People with bleeding disorders (clotting agents)

o White blood cells Infection fighting, for life-threatening infections, when white blood

cells are not working.o Whole blood is only used when a patient has lost more than 20% blood

volume to restore blood volume Artificial Blood

o Increases plasma volume – artificial plasma volume expanders are used in cases of severe burns

o Carry oxygen (and carbon dioxide)o No substitutes have been developed to replace functions of coagulation and

immune defenceo Artificial blood

Perflurochemicals are synthetic materials ca dissolve fifty times more oxygen than blood plasma, cheap, no risk of disease. However, does not flow as well, has to combine with other substances in order to work.

Only stay in circulation for 20 – 30 hours, red blood cells – 100 days Emergencies, unmatched, long storage

Oxygen and carbon dioxide in cellso Oxygen needed for aerobic respiration to release energy, carbon dioxide a

by-product of respirationo Accumulation of carbon dioxide to a great extent is toxic to the cell. Carbon

dioxide reacts with water to form carbonic acid –toxic to pH Movement of materials through plants in xylem and phloem tissue

o Xylem (dead tissue)transports water Physical process responsible for upward movement of water and

minerals, current theory Cohesion-Tension Theory

o Cohesiono Transpiration - water evaporated through the

stomates and is replaced by more watero Tension – water moves up xylem due to cohesion

and transpirationo Adhesion, when pull (transpiration stops at night for

example) water sticks to the sides of the tubes and does not fall down

o Phloem (living tissue) transports sugars and nutrients Movement of materials in phloem is called translocation, materials

move both up and down the stem. Current theories Processes rely on cytoplasmic streaming and diffusion of

sugar in the sieve elements. This generates moving force “vigorous stirring of nutrients, metabolites, genetic material and even organelles to all parts of the cell”. Accounts only for solute not solvent

Source to sink model, osmosis in solute concentrate cells pulls water with dissolved solutes in it to where sugar is being removed (sink).

Plants and animals regulate the concentration of gases, water and waste products of metabolism in cells and in interstitial fluid

Respiratory and excretory systems help maintain balance of gases, water and waste in cells and interstitial fluid

Concentration of water in cellso Medium for chemical reactions to occuro Relatively constant temperature

Removal of waste is important becauseo Some are poisonous

Transverse and longitudinal of phloem and xylem

o Take up spaceo Create problems for osmoregulationo Maintains constant blood composition and internal environment in cells

The role of the kidney in the excretory systemo Excreting nitrogenous wastes and maintaining the water balance in

mammals o Filtration, reabsorption secretion

Diffusion and osmosis in waste removalo Diffusion is too slow and non-selective of soluteso Osmosis would mean waste would stay in the body and water could leave ito Kidney dumps everything outside the body whilst actively reabsorbing still-

useful materialso In the kidney

Active – reabsorption of sodium salts, glucose and amino acids, drugs secreted

Passive – water reabsorption Nephron

o Structural and functional unit of the kidney, approx. one million nephrons in each kidney

Nephron functioning

Aldosterone and ADH (vasopressin)o Aldosterone – steroid hormone produced by the adrenal cortex of the

kidney, maintains balance of water and salts in the body by stimulating the nephron to decrease reabsorption of potassium and increase reabsorption of sodium into the blood. This leads to an increased reabsorption of chloride ions and water, this in turn causes a rise in blood volume and pressure.

o ADH (vasopression) – antidiuretic hormone, ADH, vasopressin, a hormone produced by the hypothalamus stored in the posterior pituitary of the brain. Stimulates the nephrons to reabsorb more water, decreases urine volume, increase urine concentration and blood pressure

Hormone replacement therapy for people who cannot secrete aldosteroneo Fludrocortisones, people with addison’s disease with a destroyed or

shrinking adrenal cortex which produces cortisone and aldosterone, controls salt and water balance which if upset, volume of blood falls dangerously low. Many functions throughout the body disrupted.

Enantiostasis and salt concentrationso Enantiostasis – the maintenance of metabolic and physiological functions in

response to variations in the environment. Allows metabolic functioning to continue despite fluctuations in internal environment, e.g. Blue crabs – in brackish water they change the pH of their blood to increase ability to bind with oxygen.

o Estuarine environments where salinity varies Osmoregulation – marine mammals and most fish maintain

homeostasis by osmoregulation, carrying out a range of activities to maintain a constant body fluid composition despite external environment e.g. excreting salt or concentrating urine, excrete ammonia by diffusion through gills, kidney for water balance

Osmoconformers – most plants an marine invertebrates rely on Enantiostasis to survive, the composition of their bodily fluids varies along with the environment, adjustments are made in their physiology, enzymes keep functioning despite changes to conditions or metabolic pathways

Renal dialysis

Both homeostasis and Enantiostasis are essential to maintaining the diversity of estuarine ecosystems,

Salt regulation in plants in saline environmentso Plants in mangroves (halophytes) use three main processes for keeping the

growing stems and leaves mostly free of salt. Grey mangroves, avicennia marina

o Salt barriers, special tissues in the roots and lower stems filter out salt but allow water through

o Secretion, some plants concentrate salt and get rid of it through special glands on the leaves which is then washed off by rain

o Salt deposits, deposit salt in older tissues which are then discarded – shedding leaves

Adaptations of Australian plantso Eucalypts waxy cuticle, hairy leaves, sunken stomata, few stomates, leaves

rolled inwards, and leaves reduced to spikes (cactus) phyllodes, leaves hanging vertically, cladodes – casuarinas

2. Blueprint of LifeEvidence of evolution suggests that the mechanisms of inheritance, accompanied by selection, allow change over many generations.Evolution on plants and animals

Physical conditionso Includes natural conditions such as temperature and availability of water

and weathero Australian land mass has become drier over time leading to changes in

kangaroos that are present today. 25 million years ago Australia was wetter with large areas of rainforest, kangaroos were small and omnivorous with unspecialised teeth, food was nutritious and abundant

o Australia has become more arid and grass became the dominant vegetation in some areas, environmental selective pressure favoured larger kangaroos with teeth suitable for grass grinding low-nutrition grass into a more digestible paste

Chemical conditionso Many parts of Australia have soils of high salinity, range of salt tolerant

plants that have evolved to inhabit those areaso The sheep blowfly, lucilia cuprina, major problem to sheep industry, can be

lethal to sheep. Chemicals such as dieldrin and organophosphates have been used to control it, however genetic resistance has evolved within the fly population making the chemicals ineffective due to resistance

Competition for resources

o Occurs within a species and between a species, competition can lead to different species using different resources

o Resources can include food, space or mates. If a species could specialise on slightly different resources or breed at different times, they could avoid direct competition.

o Two distinct species of the fruit fly has evolved as they prefer different trees.o Plants competing for light can develop wider canopieso Allelopathy – production of inhibitory chemicals released into the

environment Areas of study supporting evolution

o Paleontolgy – the stud of fossils, providing a record ofver time of how living things have evolved.

Fossils that have been considered as transitional fossil forms are those that features that make them an intermediate form between major groups of organisms e.g. seed ferns – have features of both ferns and gymnosperms, resembles a fern in structure but produces seeds not spores. Archaeopteryx – bird like reptile, had wings, reptilian teeth and long jointed tail.

o Biogeography – earth has a number of different biogeographical zones, such as the arctic zone, each with specific environmental features and each, therefore containing organisms with special adaptive features. Study of the distribution of organisms over earth providing evidence that species have originated from common ancestors, become isolated, diversified

o Comparative Embryology – enzymes of many different species (specially vertebrates) are very similar in the early stages of development. All vertebrate embryos have gill arches, notochords, spinal cords and primitive kidneys. Vertebrate embryos have the same type of skin that later develops into a variety. Pattern of vertebrate development, three germ layers give rise to different organs and this derivation of the organs is constant, similarities point towards a common ancestor.

o Comparative anatomy – similar bone structures (pentadactyl limbs)o Biochemistry – DNA differences

Theories of evolution Darwin/Wallace theory of evolution

o Natural selectiono Divergent evolution – evolving to be different e.g. finches on Galapagos

islands o Convergent evolution – evolving to be similar, e.g. the Australian marsupial

mole and unrelated placental mole, Cape golden mole, both live in burrows and are insectivorous.

Advances in technology have allowed for a variety of new analysis and conclusions, molecular biology has amplified the fossil record. E.g. the human DNA shows a close relationship with apes

(table of theory evolution)Gregor Mendel (1822 – 1884)

Garden peas, methodical careful experimentation for years Chose peas because plants “bred true” for the characteristics he studied, e.g. long

stem, short stem, green/yellow seeds. His conclusions were:

o Inheritance is not a blending of characteristics

o Inheritance is controlled by a pair of particles in the cells which he called factors

o Two factors segregate from one another when sex cells are formedo Characteristics are either dominant or recessive

Experimental techniqueso Allowed valid and reliable data to be collected, analysed his results

statistically Monohybrid crosses involve looking at one characteristic only. Homozygous Tt, heterozygous TT

Alleles-Different forms of the same gene Genes – discrete segments of the long molecules of DNA that are found on chromosomes and code for a polypeptide Mendel’s work was not recognised until 1900 because scientists did not have the

background or technology to understandChromosomal structure

The number of chromosomes in a body cell is called the diploid number

Punnet squares (practice ratios)

The half-number of chromosomes is called the haploid number as seen in sex-cells Sutton and Boveri

o Boveri, German biologist in 1902 showed with sea urchins that a complete set of chromosomes is necessary for normal development of a organism.

o Sutton, American scientist in 1902 studied grasshoppers, his observations provided evidence that chromosomes could carry Mendel’s factors. 1903 he showed segregation and recombination of genes showed striking similarities to the behaviour of chromosomes

Chromosomes are the carriers of hereditary units which are transmitted through chromosomes

Chromosomes occur as homologous pairs As a result of meiosis, every gamete receives only one chromosome

of each chromosome pair Chromosomes keep their individuality throughout cell division Distribution of each homologous pair is independent of each other Since hereditary factors are more numerous than chromosomes,

each chromosome has to carry many units.o Suggested genes are part of chromosomeso Chromosomes are made of DNA and protein (histone). Beads – genes, links –

protein, doubles-stranded molecule twisted into a helixo Structure of DNA (made up of nucleotides)

A nitrogen base A sugar A phosphate

o Simple definition for a genetic unit is a 3-base code sequenceo DNA contains four different nitrogen bases: thymine, adenine, guanine,

cytosine Structure and behaviour of chromosomes during meiosis and the inheritance of

geneso Meiosis – produces sex cells

Different pairs of homologous chromosomes behave independently of each other and each pair segregates randomly to the daughter cells

Gene pairs on different chromosomes sort themselves in the same manner as the chromosome pairs, daughter cells are genetically different

Gamete formation and sexual reproduction in variability of offspringo Gamete formation results in the halving of the diploid number, sexual

reproduction results in combining gametes to produce a new diploid organism, this results in variability of offspring

o Meiosis leading to variability Random segregation of individual chromosomes with their

associated genes Process of crossing over where the maternal and paternal

chromosomes of each pair may exchange segments of genes making new combinations of genes on the chromosomes

o In sexual reproduction each male and female cell produces 4 sex cells from meiosis, variability is introduced depending on which sex cells are successful in fertilisation, the resulting embryo will have a completely different set of genes from either of the parents

Dna stucture

Sex-linked inheritance produces variations to Mendel’s predicted outcome

Meiosis

Mitosis

This results from genes carried on either the male or female chromosome, usually on the female sex chromosome with no corresponding gene on the male chromosome. Sex chromosomes determine the sex of the offspring, sex chromosome pairs separate during meiosis. Haemophilia and red-green colour blindness are examples of sex-linked diseases.

1910, Morgan and his students began a series of breeding experiments with a small fruit fly. The results could not be explained by Mendel’s method. His hypothesis was

that the gene for white-eye in Drosophilia melanogaster is actually part of the X chromosome. Morgan discovered other genes which he concluded were carried on the X chromosome, these genes were said to be sex-linked.

Co-dominanceo Homozygous genotypes are expressed, e.g. Andalusian fowl – black fowl BB,

white fowl WW, blue fowl BW. Also in humans AB blood type is an example of co-dominance

The effects of environment on the expression of geneso Factors of the environment can include availability of water, nutrients and

sunlight, the type of soil, the presence of poisonous substances and competition from other organisms determine how the genes are expressed.

o The appearance of an individual is not based solely on their genetic information, environment also plays a part

Practice sex-linkage punnet squares

Plant prac

o E.g. hydrangeas in acidic soil – blue, in basic – pink, (nature, nurture theory

Structure of DNA can be changed and such changes may be reflected in the phenotype of the affected organism DNA replication

o When the cell is not dividing the DNA within it is undergoing replication

Why DNA replication is importanto To support growth, repair and reproductiono Essential in cell division for identical daughter cells in mitosiso For variety in meiosis

Scientist Role in determining structure of DNAJames Watson and Francis Crick

Suggested double helix structure of DNA and pairing of the bases, that this made possible a copying mechanism for DNA

Rosalind Franklin Provided crucial scientific evidence which Watson and Crick based their assumptions off, sexism was rife and she was vilified and did not gain recognition for a while

Maurice Wilkins A physicist provided X-ray diffraction models of large molecules which Watson and Crick based their theory off, in 1962 the three won the Nobel prize

Process by which DNA controls the production of polypeptideso Controls production of long chains of amino acids (polypeptides) which

make up proteins. Up to twenty different amino acidso Different DNA sequences provide different proteins, some genes control the

production of proteins that will become haemoglobin, a specific hormone or an antigen. Still other genes control the production of structural proteins which make up muscle and skeletal tissue, the order in which the bases are arranged in the DNA molecule forms the genetic code, therefore

o Instructions on the DNA molecule control the chemical process of life.o DNA controls cell activity by directing synthesis of all proteins in the cell.

DNA replication

o DNA is transcribed onto RNA (which is single stranded and replaces thymine with uracil which makes it out of the nucleus to the cytoplasm where protein is being made to give instructions. RNA synthesis is controlled by enzyme RNA polymerase

Relationship between proteins and polypeptideso A protein is made up one or more polypeptides. A polypeptide is made up of

a chain of many amino acids

Beadle and Tatum ????

Mutations as a source of new alleles in organisms o Mutation is a change in DNA, usually involving changes in bases, a change in

the DNA information on a chromosome. New alleles in organisms come about as a result of mutations. Many mutations are harmful.

o For evolutionary change to take place, a mutation needs to occur at the right time, place, need. There may be a delayed response

Practice DNA - RNA diagram

Model of polypeptide synthesis

o Mutations in body cells may cause changes in the organism’s body such as cancer; these changes cannot be passed on to offspring but mutations in sex cells can be passed on to offspring.

Evidence for the mutagenic nature of radiationo Environmental factors that may increase the rate of mutations include

exposure to x-rays, atomic radiation and ultra-violet light. Studies of cancer have provided much indirect evidence for the mutagenic nature of radiation. Increased numbers of cases with cancer after x-ray use and grape-picking suggest they are directly linked.

o Laboratory experiments have shown that mice exposed to alpha radiation from plutonium-238, even in small doses, had a high frequency of chromosome damages

How this provides support for Darwin’s theory of evolutiono Most organisms produce more offspring than can survive. Darwin observed

variations in organisms and showed how they form a pool of features on which natural selection acts (i.e. the environment selects the organisms with beneficial features). Now known that variations in the genetic pool occur due to recombination of genes in sexual reproduction, crossing over and mutations. Organisms with DNA-controlled features are able to survive and make them better able to exploit available resource, therefore able to produce more offspring.

Modern example of ‘natural’ selectiono Insecticide resistance in insect pests is an example of ‘natural’ selection. This

is due to a build up of resistance. Concept of punctuated equilibrium and how it differs from Darwin’s view

o Darwin’s theory – evolution occurs over a long timeo 1970s , theory of punctuated equilibrium was proposed, states that most

species adapt until they reach a stable stage and are in a state of equilibrium with their environment. This explains why fossil record can be seen as incomplete.

Current reproductive technologies and genetic engineering have the potential to alter the path of evolution

1970’s, understanding of evolution exploded with the development of powerful laboratory techniques for studying and manipulating genes.

Current reproductive techniques Artificial insemination

o Requires fertilisation, sperm selected from a selected organism with desirable traits. Artificially inserted into another selected organism with desirable traits as well.

Genes that would have been eliminated in natural populations, because the organism is sterile, will be passed onto offspring and remain part of the population. Sperm banks are created, from which breeders select desired characteristics, thereby increasing the proportion of certain genes in a population.

Artificial Pollinationo Requires fertilisation, pollen taken from selected breed of plant and

artificially transferred to the female stigma. Can create new hybrid species, altering the composition of the

population: new gene combinations are created and some genes are now more common than before.

Can result in reduction of biodiversity as we produce what humans prefer

Cloningo Does not require fertilisation

Animal and plant cloning refers to the making of generally identical organisms asexually from single cells without fertilisation

DNA extracted from the organism’s tissue and inserted into egg

Cells are taken from an embryo and allowed to develop into several embryos with identical genes.

o Characteristics strictly controlledo Organisms produced in short periods of timeo Identical, population is less likely to survive sudden

environmental changes. Transgenic species

o Specimens can now snip genes from one species and insert them into another species to produce genetically altered organisms. These organisms have not come about because of natural processes. They have not existed on Earth until now.

Reason for use – processes to produce transgenic species are used because they enable scientists to artificially combine the qualities of different organisms.

Example – transgenic tomatoes have been developed to have a longer shelf life in the supermarkets.

o Ethical Issues – relate to rights of humans in general, as well as other species. Ethical issues relate o possible mistakes with the technology, the possibility that genetically modified foods have difference that are not yet determined or understood, the possibility that they could damage the environment, the welfare and rights of the animals being used and our ability to deal with problems that might arise.

Reproductive technologies and genetic diversity of specieso The introduction of foreign genes from genetically engineered organisms

into the environment is linked strongly to concerns about loss of biodiversity. The effects of genes are not always obvious. Changes are not always predictable.

o Potential impacts: Transgenic species depends on how well the species competes, if

the change is beneficial then it could result in the gene pool increasingly include a greater proportion of these genes.

Genes from genetically engineered organisms have the potential to move from their original release point to affect the gene pool of other plants and animals.

Short term, genetic engineering can increase genetic diversity because it allows genes to be moved from one species to another to produce new combinations.

Long term, engineering artificial identical copies (clones) of organisms decreases genetic variation. Selection of desired genes and the creation of new genetic combinations can reduce the original genetic material of the organisms. This can occur to the point where the original genes may be lost forever.

Potential impact with a plant

o Incorporation of insecticides into crops such as cotton and rice The non-specific nature of the impact on insects (other endangered

insects may die) The chances of genes spreading via pollen into other plants.

Potential impact with animalo Genetically modified fish for aquaculture. Designed for rapid growth and to

attract females. If released there is a high chance that their engineered genes will be transferred to wild populations. Can potentially wipe out other fish populations.

3. The Search for Better HealthThis chapter takes a historical approach to our understanding and treatment of disease. The resulting diversity of methods of treating and preventing disease and options for the future research and treatment are explored.

Difficulties of defining the terms ‘health’ and ‘disease’o Vaguely, disease is any condition that impairs normal living processes and is

recognised by the presence of specific symptoms. Many diseases are best understood as a disturbance of homeostasis. Health refers to the overall well-being of an organism, not just absence of disease. As part of the living process, an organism automatically responds to cell malfunctioning and disturbances to homeostasis and tries to repair itself and retain balance. Different organisms, even of same species, will differ in health, susceptibility to disease and the ability to respond to fluctuations in homeostasis.

How function of genes, mitosis, cell differentiation and specialisation assist in the maintenance of health

o the degree to which an organism is health depends on whether or not its cells are functioning properly and how well the body can repair a malfunction or imbalance. Growth of tissues and the healing of tissues are dependent on protein metabolism. Protein metabolism is controlled by genes. Diseases such as cystic fibrosis can result from genes that produce faulty enzymes.

o Mitosis is the cell division that will allow normal growth and repair. If the processes controlling mitosis go wrong than cancer may occur. Cell specialisation and differentiation are important to help prevent entry of pathogens or to respond quickly when infectious agents are present.

Maintenance and repair of body tissues in relation to gene expressiono “Switching on” a segment of DNA to produce a polypeptideo Manipulating the polypeptide into the required proteino Transporting and manipulating the protein to become either a component

of cytoplasm or to function as an enzyme and control the production of other cellular molecules.

o Constitutive genes – expressed continually to maintain normal body functions. E.g. saliva

o Facultative genes – are only expressed when neededo With sufficient cellular materials and organelles, mitosis allows cells to

divide. o Specialised cells often do not possess the ability to survive, some such as

nerve cells cannot be easily replaced. – Stem cells have the ability to divide and become specialise.

Over 3000 years ago the Chinese and Hebrews were advocating cleanliness in food, water and personal hygiene

o Some understanding of cause and effect may have underpinned the religious beliefs and practices of many ancient civilisations that advocated personal hygiene and cleanliness.

o Infectious and No-infectious diseases Infection – the presence of a disease-causing organism in or on the

body of a host. Infectious diseases can be caused by prions, bacteria, viruses, protozoa, fungi or macroscopic parasitic animals. Can be spread by direct or indirect transmission.

Non-infectious diseases cannot be spread from one organism to another, non-infectious diseases can be caused by genetic factors, environmental factors, diet or physiological malfunction, such as diseases associated with aging.

o Control of disease Ways of preventing contamination of food and water through

proper sanitation, proper food handling, personal hygiene and water treatment processes.

Ways to prevent decomposition and spoilage of food Ways to prevent transmission of the disease and infection by using

disinfectants, sterilisation and antiseptics and through minimising contact with food and water. Crowded conditions, poor sanitation and untreated sewage increase the spread of disease.

o Conditions under which an organism is described as a pathogen An organism living in or on another organism that is capable of

causing disease Have enough virulence (number of particular pathogen

needed to cause the disease). Survive in or on the body without being destroyed by the

body’s natural acidity and mucus Escape from one host to another Survive transmission from one host to another

Pathogens cause disease symptoms by: Large number of pathogens present too much for tissue to

function properly Pathogens actually destroy cells or tissues Bacteria produce poisons called toxins The pathogen may not directly harm the host but an

excessive immune by the host may cause tissue damage.o Example of treating drinking water

Drinking water is screen and filtered to remove large and small particles. Membrane filtration is used with an increased level of control of pore size. Activated carbon may be added to water as it absorbs many contaminants that can then be removed by filtration. Ion exchange resins can also be used to remove dissolved contaminants. Such materials form the basis of desalination plants. Coagulent can be added to cause suspended particles to flocs that settle rapidly and are easily filtered. Ozone or chloride dioxide disinfect and oxidise a range of substances such as algal toxins, taste and odour compounds and even trace levels of insecticides in water. Ultraviolet irradiation, fluorine can be added too.

During the second half of the nineteenth century, the work of Pasteur and Koch and other scientists stimulated the search for microbes as causes of disease

o Pasteur and Koch Pasteur – before lenses and microscopes it was believed that living

matter, such as moulds and maggots, could come spontaneously from non-living matter. He discovered that microbes such as bacteria can cause disease. With his famous swan-neck flask experiment, he demonstrated that bacteria and mould cannot generate spontaneously.

Koch – showed that bacteria were the cause of a disease called anthrax in horses, cows, sheep and humans. Demonstrated that bacteria were the cause of tuberculosis in humans. Designed rules of procedure called Koch’s postulates

Must be shown that the microorganism believed to be cause of the disease is always present in the diseased organism.

Micro-organism must be isolated and grown in a pure culture – a culture containing only that micro-organism

Micro-organisms from the pure culture must be able to produce the disease in a healthy organism

“ “ isolated from experimental organisms, grown in pure culture and compared with the micro-organisms in the original culture and shown to be identical.

Cause and preventiono Vector is an organism, usually an anthropod acting as a carrier of the

pathogenic organism. Malaria is transmitted by female mosquitoes

Pasteur’s experiment

control and prevention involves:o Reducing the population of the vector – insecticide, removing breeding sites,

introducing minnow fish that eat mosquito larvaeo Reducing the contact between the vector and the host – programs inform

people of the risk of contracting malaria and ways to prevent mosquito bites, such as using insect repellent and netting

o Drugs – people are advised to take chloroquine before going to malaria infested area.

Types of pathogens that cause infectious disease in plants and animals

Type of pathogen

Some distinguishing features Example

Prion Defective form of a protein moleculeDoes not contain DNA or RNAMostly attacks brain or nerve cells

Scrapie in sheep

Virus Non-cellularContains DNA, RNA and protein coatRequires a living host cell to replicate

InfluenzaHepatitisMeasles

Bacteria Prokaryotic cellDivides quickly and/or produces toxins

BoilsCholera

Protozoan Eukaryotic cell – single-celled organism Amoebic dysentery

Mosquito cycle and malaria cycle

May have a complex life cycle GiardiaFungi Eukaryotic cell with cell wall

Spreads via spores or rapid divisionSome internal external skin and nails, while others enter the host’s body

RingwormTinea

Macro-parasites

Eukaryotic cells – multicellular organismMostly arthropods or worms

Fleasticks

Infectious diseasesInfectious disease

Cause Transmission Host response and major symptoms

Treatment, prevention and control

Food Poisoning

Staphylococcus bacteria that produce a toxin

Contaminated food

Nausea, vomiting, diarrhoea

Usually treated with rest and drinking water to replace lost fluids; preventing contamination of food and water; improved sanitation, proper food preparation and refrigeration; health regulations and laws

How antibiotics assist the management of infectious diseaseso They are compounds that kill or inhibit bacterial pathogens. For example,

penicillin is made from a fungus – the Penicillium mould. Can be used to prevent infection.

o Resistance to antibiotics an increasing problem hence vaccinations to prevent need for antibiotics

Often we recognise an infection by the symptoms it causes. The immune response is not so obvious, until we recover

o Defence barriers to prevent entry of pathogens in humas Skin – is a mechanical barrier. Unbroken skin protects other tissues,

and collects and holds pathogens. Mucous membranes – occur along the alimentary canal, trapping

pathogens. Respiratory surfaces and urogenital surfaces also lined with mucous membranes.

Cilia – motile cilia are found in the lining of the trachea. Cilia beat in one direction to sweep mucus containing trapped pathogens and small particles out of the lungs. Coughing also.

Chemical barriers – such as lysosymes found in body fluids and secretions inhibit pathogens. The pH of body fluids may also inhibit some pathogens. Acid pH on the skin discourages growth of many microbes and acidity of the stomach destroys many micro-organisms.

Other body secretions – oil glands on the skin secrete fatty acids that inhibit the growth of some bacteria and fungi

o Antigens Used for any substance that is usually foreign to an organism’s own

body, e.g. part of a bacterium or a virus. They are protein molecules

that trigger an immune response, often because of the production of specific antibodies. Each pathogen has its own antigen.

o Why organ transplants trigger an immune response Antigen-antibody response result in rejection of transplanted tissue.

It is recognised by the body as a foreign antigen, triggering the immune response.

o Defence Adaptations Inflammation response – designed to isolate and destroy foreign

particles and prepared the tissue for healing. Dilation of blood vessels occurs, increasing the blood flow and raising the temperature of the tissue.

Phagocytosis – cells that engulf and destroy micro-organisms. Important as the body’s immediate defence against infection.

Some white blood cells Scavenger cells that remove foreign particles Macrophages

Lymph System Returns intercellular fluid to the blood system, filters cell

debris and produces white blood cells responsible for the immune response.

Cell death to seal off pathogen Some pathogens, macrophages and lymphocytes completely

surround a pathogen so that it is enclosed in a cyst. The white cells involved die, so that the pathogen is isolated from its food supply and also dies.

o A disease caused by an imbalance of microflora Thrush, a disease caused by the fungus Candida albicans, one of the

natural micro-organisms of the human body. Occurs in the mouth, respiratory tract, female genital tract and gastrointestinal tract. Occurs when there is an imbalance in the number of pathogen cells. Usually kept in balance from competition such as lactobacilli.

MacFarlane Burnet’s work in the middle of the twentieth century contributed to a better understanding of the immune response and the effectiveness of immunisation programs

o Ability of an organism to prevent or overcome infection by a pathogen is through natural resistance and acquired immunity. Can be natural or artificial. Immunity can vary from even a few weeks to many years and in some cases for the life of the organism.

o Burnet suggested how an organism’s body is able to distinguish between its own cells and those of other organisms:

Individual lymphocytes have the genetic capacity to make one or possibly a few particular antibodies

The lymphocytes have receptor molecules on their surface. These receptors have the same specificity for antigens as the antibody that the lymphocyte cell can make.

Therefore, when an antigen enters the body, those lymphocytes with receptors that can react with the antigen will be stimulated to differentiate and will produce plasma cells producing antibodies with specificity toward the antigen.

o Components of the immune response

T cells, B cells and antibodies are components of the body’s main immune responses. These responses help the body to build up resistance and fight long-term infection.

o Antibodies Antibodies are proteins found in blood plasma and other body fluids

that can combine with and help to neutralise an antigen by: Combines with the antigen to cover its active site so it has

no effect on the body May dissolve parts of the cells walls of bacteria, destroying

them Neutralises the toxins produced by the antigen May cause bacteria to clump together, making it less active

and more easily taken up by the lymph system. May make the antigen more susceptible to phagocytosis

T cells (are immunocytes that leave the bone marrow to differentiate in the thymus. T cells circulate between the lymph nodes and the spleen and mediate immunity but do not produce antibodies.) – some white blood cells – phagocytes, some non-phagocytic cells called lymphocytes which are receptor cells for antigen. T cells and B cells are the two different types of lymphocytes responsible for the immune response in the human body. T cells destroy antigens, do not produce antibody-producing plasma cells.

Directly destroy the antigen Stimulate the activity of phagocytes Responsible for cellular immunity. Produced in thymus which is sutuated under the sternum Constantly circulating blood to the lymph nodes and spleen

and then back to the blood. B cells (are immunocytes, precursors of the plasma cells that

synthesise and secrete antibodies) – lymphocytes that are stimulated to produce plasma cells

Presence of antigen molecules stimulates the lymphocyte cells which begin to divide and produce more lymphocyte cells and specialised cells called plasma cells, which make antibodies. B cells accumulate in the spleen and lymph nodes and do not circulate

o Immune response in the human body Interaction between B and T lymphocytes

T cells influence and help B cells. Two mechanisms have been proposed to explain the cooperation between T cells and B cells in antibody formation.

Mechanisms that allow interaction between B and T lymphocytes Mechanism 1: T cell produces a soluble factor after

interaction with an antigen. B cell reacts with the soluble factor and the specific antigen to become a functional antibody-producing cell.

Mechanism 2: based on cell contact between the T cell and the B cell. The close contact comes about because of interaction with the antigen. This contact allows the T cell to

signal the B cell to become a functional antibody-producing cell.

Range of T lymphocytes and the difference in their roles, exposure to an antigen makes the particular responding T cells differentiate into a range of T lymphocytes

o Killer T cells, secrete substances that destroy antigens directly, enhance the activity of macrophages and inhibit replication of viruses

o Helper T cells, which enhance antibody production by B cells. HIV infects T4+ cells (or T-helper cells). Chronic infection with HIV leads to a decrease in the number and function of T4+ cells

o Suppressor T cells, which help to turn off the immune response after an infection which has been controlled

o Memory T cells, which retain the ability to recognise the original invading antigen so that a subsequent invasion can be dealt with quickly.

Summary of the body’s own protection and immune response

Two models to explain the cooperation between T cells and B cells in antibody formation

How vaccinations prevent infectiono Artificial required immunity is called immunisation.o Involves injecting or ingesting into the body antigens from living, dead,

weakened or non-virulent strains of micro-organisms.o Stimulate a person’s own immune response to develop immunity

Effectiveness of vaccination programso Smallpox – one the most dreaded disease in the world, in 1700s one in three

people who caught the disease died. In 1796, Jenner developed a vaccine. 1960s, the World Health Organization started a world wide immunisation program. Using jet injector guns with high pressure sprays made it possible to inoculate one thousand people per hour. 1980 WHO declared the world free of smallpox.

o Diphtheria – bacterial infection transmitted by close physical or respiratory contact, commonly infected pre-school and school-aged children in temperate climates. In 1923 a vaccine was released. Took until 1940s 50s for the spread of the disease to shift from cyclical epidemics to occasional outbreaks of low intensity. Vaccine DTP because it prevents Diphtheria, tetanus and pertussis. 1974 – WHO began expanded program on Immunisation(EPI), goal to immunise all children against diseases such as diphtheria, polio and tuberculosis by 1990.

2002 5000 deaths due to D, 4000 of those under 5yr olds 2005 vaccination rate was 95% across 183 countries.

o Polio – mainly a disease in young children that results in paralysis (usually permanent) and even death. The poliomyelitis virus enters through the mouth but attacks nerves. More frequently leg nerves. Until 1955 when a vaccine was introduced, thousands of children in industrialised countries became crippled with polio each year. By 1960s an oral vaccine was introduced and was bought under control in industrialised countries, but not in developing countries, 1988 WHO began another EPI, now worldwide the numbers of cases are down 99%.

Suppression of the immune response in organ transplant patientso Transplanting tissues from one animal to another brings about an antigen-

antibody response because the tissue proteins of one individual are not the same as those of another, except for twins or inbred strains). T cells are the main cell type responsible for the rejection of transplanted organs. Transplant patients are then given powerful drugs to suppress the immune response to allow the transplant to become part of their body. These substance can have side effects though such as diabetes, renal impairment,

and leave recipients susceptible to infection. Therefore antibiotics are also given to a transplant patient.

Epidemiological studies assisting the causal identification of non-infectious diseases Many diseases are not caused by infections, epidemiology is one approach to this. Main features of epidemiology

o Called the science of prevention, it is based on the systematic and ongoing collection, collation, analysis and interpretation of data.

Lung cancer as an exampleo Linking of cause and effect requires many studies with large populations to

ensure that there is not just a correlation between two things in a population.

o Doll and Hill in England and Hammond and Horn in the US established independently that cigarette smoking markedly increases the chances that a person would develop lung cancer

o Other evidence comes from comparisons of trends in smoking rates across sexes and trends in lung cancer. More males smoked and more males had lung cancer, male smoking rates declined before the rate declined in females.

o NSW Cancer Council reports: Smoking is a major cause of lung cancer Workers exposed to industrial substances such as asbestor, nickel,

chromium compounds, arsenic, polycyclic hydrocarbons and chloromethyl ether have a significantly higher risk of developing lung cancer.

Link between passive smoking and lung cancer 1995-2004, the age-standardised incidence rate of lung cancer fell

by 18% in males and rose by 11% in females 2003 lung cancer was the leading cause of cancer-related death Reports epidemiology studies on nicotine replacement therapy and

environmental tobacco smoke. They report an increase in public acceptance of bans on smoking in pubs, clubs and gaming areas.

Causes of non-infectious diseaseo Inherited disease – caused by genetic factors inherited from parents include

Down’s syndrome, phenylketonuria, haemophilia, colour blindness and muscular dystrophy.

o Nutritional deficiencies – can lead to obesity, malnutrition diseases such as scurvy or night blindness that are caused by protein or vitamin deficiencies. Inadequate or imbalanced diets have a role in diseases such as arthritic, heart and circulatory problems, kidney, liver or gall bladder disease. Nutritional deficiencies resulting from anorexia nervosa and bulimia can be fatal.

o Environmental diseases – can be factors such as high stress levels, noise, overcrowding, drugs and pollutants. Chemicals include nicotine, asbestos, mercury and food additives. Cancer – causing substances are called carcinogens. Carcinogens may get into the nucleus of the cell and combine with the cell’s DNA, making it abnormal.

o Some diseases can be a combination of these though. Non-infectious disease example (Atherosclerosis) Occurrence and cause

o High occurrence in developed countries such as Australia; caused by narrowing and hardening of the artery walls by deposits of fat; caused by smoking, a diet high in fats, lack of exercise and stress.

Symptomso Restricts the flow of blood through arteries; causes breathlessness, fainting,

loss of blood to parts of the body; if the blood flow is restricted to the brain, it can cause a stroke; if the blood flow is restricted to the heart it can cause a heart attack; the person has pains in the chest, high blood pressure; blood clots may form.

Treatment/managemento Surgery is used to treat the condition

Arteries are unclogged or replaced A ‘balloon’ is often inserted to keep the artery open; drugs to lower

blood pressure and/or blood cholesterol are administered; prevention includes low-fat diet, lowering of stress, no smoking and a regular exercise program.

Strategies to prevent and control disease Role of quarantine in preventing the spread of disease, plants and animals n

Australia.o Australia’s natural isolation has not only protected many native species in

the past from predation and competition, it has also served to prevent the introduction of new diseases for plants and animals. Quarantine regulations are therefore very strict.

o Within Australia, some areas are free from certain diseases such as the bunchy top virus in bananas. Movement of plant material, such as fruit and plant stock, across regions of Australia has been restricted by quarantine laws to prevent the spread of disease.

o Before quarantine many problems have arisen from the introduction of plant and animal pests such as rabbits, foxes, feral pigs and camels, the cane toad being a well-known, well-intended by disastrous introduction.

o Effectiveness of quarantine Fire blight is a bacterial disease that infects pears, apples and

related ornamental plants. The disease organism is native to North America but has spread to Europe, Middle East, Central America and New Zealand.

o Strategies for controlling and/or preventing disease Public health programs

Such as “slip, slop, slap” campaign designed to prevent skin cancer, raise public awareness. The ‘grim reaper’ campaign was used to warn of the risks involved in contracting the AIDS virus. The childhood immunisation program, run by the Commonwealth Department of Health and Aged Care includes a public health program. Raising awareness about obesity is targeted at younger generation.

Pesticides Use of pesticides helps control insect-borne diseases such as

malaria. Mosquitoes are vectors of malaria, yellow fever, dengue fever, lymphatic filariasis, West Nile Virus and equin encephalitis.

DDT strictly limited

Some pesticides target mosquito larvae, they can be either biological

Organophosphates applied directly to water source to contain larvae.

Genetic engineering to produce disease resistant plants and animals Mosaic virus resistant gene into tomatoes Virus-resistant genes have also been engineered into yellow

squash, zucchini, potatoes and papaya Used to produce transgenic plants that contain the gene

from a naturally occurring insecticide Genetic engineering of the malaria vector anopheles

mosquito to prevent life cycleo Shift from treatment and control to management or prevention

with advances in our understanding of genetics, epidemiology has now entered the field of genetic epidemiology – the analysis in large populations of the interactions of genes, genetic variations and environmental factors. Genetic epidemiology will contribute to the discovery of new drug treatments that could be tailored to an individual’s future likelihood of getting a particular disease. Continuing to change the emphasis of health care from treatment to prevention.

Response to avian influenza, we have become increasingly conscious of the ability of viruses to change and transmit across species. Bird mobility has a major impact on the effectiveness of quarantine to prevent the spread of this disease, at least among bird populations. The WHO has a website called EPR – Epidemic and Pandemic Alert and Response.

4. Communication Humans and other animals, are able to detect a range of stimuli from the external

environment, some of which are useful for communicationo How receptors detect stimuli – the skin has pressure, pain, heat and cold

receptors. In taste, there are five main types of receptors: salt, sour, sweet, bitter and umami. There are 1000 different smell receptors that can detect, in total, over 10 000 different odours.

o Response to a stimulus – response to a stimulus involves the following stages

Messenger that reflects changes in the environment Receptor that detects the stimulus. Messenger that involves receptors that change the energy of the

stimulus into energy that is used to start a nerve impulse Effector that is the organ that receives the message and carries out

the response Response is carried out

Diagram of stimulus-response

Senses and communicationo Visual – communication by colour, pattern of plumage (in birds), posture,

body movement, facial expression; used in courtship behaviour, to signal breeding times, to signal threat, to defend territory.

o Olfactory – communication via specific chemical signals; used in scent marking of boundaries and territories; to search for and identify food and water; species and sex recognition; to detect and avoid harmful substances

o Auditory – communication by sound; used to defend territory; make distress calls to alert others to danger; used in courtship, bird song helps females find males of the same species

o Tactile – used in avoiding obstacles, fighting, defence mechanisms, friendship behaviour and copulation; many animals use tactile signals in courtship behaviour

o Taste – bees and blowflies have ‘taste’ receptors on their feet that help them locate food

o Other senses – these include senses to detect electric fields, magnetic fields, polarised light and gravity.

Visual communication involves the eye registering changes in the immediate environment

o Anatomy and function of the human eye Conjunctiva – a fine transparent membrane that covers and protects

the surface of the cornea Cornea – a transparent front window through which light enters the

eyeball. It performs much of the initial focusing of the image. Sclera – is the white of the eye, tough outer layer and protects the

eyeball Choroid – underneath the sclera is the choroid, a sheet of blood

vessels that carry oxygen and nutrients to the eye and remove carbon dioxide and wastes. Also prevents light in the eye from reflecting internally.

Retina – complex structure of photoreceptors (rods and cones) on the back of the eye. Photoreceptors allow us to see shape, movement and colour; retinal nerve cells convert incoming light into nerve impulses.

Iris – the coloured part of the eye, which is a ring of muscle with a hole in the middle (pupil). Controls the amount of liht entering the eye. In dim light the iris relaxes and the pupil dilates to let more light in, while in bright light the iris tightens and the pupil contracts.

Lens – sit behind the iris and focuses the light onto light-sensitive cells

Aqueous and vitreous humor – are the clear jelly that fills two pressurised chambers. They give the eye its spherical shape.

Ciliary body – circular, muscular ring that focuses the lens. Optic nerve – contains a million nerve fibres that conduct the nerve

impulses to the vision centres in the brain.

Diagram of the human eye

o Range of wavelengths of the electromagnetic spectrum detected by humans Human eye can detect wavelengths between 380 and 750 nm of the

electromagnetic spectrum. This range is called ‘visible light’ and it is composed of the colours red, orange, yellow, green, blue, indigo and violet.

Other vertebrates can detect different ranges of electromagnetic ranges compared to humans. Many are not able to distinguish different colours. Dogs for example see only black, white, yellow or blue shades.

Invertebrates can also detect different ranges of electromagnetic radiation. Many insects and some spiders see ultraviolet light. They are less sensitive to the higher wavelengths (red).

o Detection of electromagnetic radiation Colour sensitivity is related to the structure of the eye. The number

of types of colour-sensitive cones and their sensitivity range in many vertebrates determines their colour vision.

Colour vision is related to evolution. Most nocturnal animals have vision that is less sensitive to colour. It is believed humans and our primate line evolved from a nocturnal ancestor, so our colour vision evolved separately from many of the other placental mammals. Colour vision can be important for the recognition of food sources. Particularly bees, birds and herbivorous primates. Snakes and some fish detect infra-red radiation will be able to easily detect their prey, as the heat from their bodies will result in infra-red radiation being

emitted. This allows the snake to successfully compete for food at night.

Orientation and navigation in some birds have been linked to a dependence on the presence of blue and green light. Monarch butterflies, which can migrate over great distances, navigate by ultraviolet light in the sky.

The clarity of the signal transferred can affect interpretation of the intended visual communication

o Refraction of light – refers to bending of light rays, occurs when light passes through a denser medium (such as water), because it’s sped is slowed down. The denser the medium, the more it decreases it’s speed and the greater the refractive index of the medium as compared to air. If light waves hit the new medium at an angle, the light waves are bent or refracted.

o Role of the cornea, aqueous humor, lens and vitreous humor in refraction of light

Each of these structures is made of a substance with differing optical density. Most of the refraction in the eye take splace in the cornea, here there is the largest change in the index of refraction, as light leaves air and enters the cornea. Because the ciliary muscles can change the shape of the lens the amount that the lens refracts the light varies, enabling focus on objects at differing distances.

o How the eye focuses on an object Cornea and the anterior and posterior surface of the lens refract

light rays entering the eye. The lens is a convex lens. In birds and mammals the lens is focused with the ciliary body.

Accommodation of the eye – the process by which the lens change shape to focus images from objects at different distances onto the retina. Image needs to fall on the fovea which has the greatest density of cones to ensure visual acuity. Light rays from distant objects tend to be parallel and need less refraction to form a clear image.

Changes in the lens – distant objects – ciliary muscles are relaxed and the lens tend to remain thin. Near objects – the ciliary muscles contract, forming the lens into a more rounded shape, being the diverging rays more so that a clear image forms on the fovea.

Importance of this process – focusing is the result of accommodation, it is essential for a clear vision.

Diagram of accommodation

o Change in the refractive power of the lenso Can be compared using the SI unit dioptre, which is inversely proportional to

the focal length of a lens (the larger the number of dioptres, the less refraction). In humans it is approximately 60 diopters, to read at a distance of 30cm, 3 diopters of refractive power is needed.

o Myopia and Hyperopia

o Myopia (short-sightedness) - when the distance between the lens and the retina is too great or the lens is too strong, so the image will be focused in front of the retina, the image appears blurred.

o Hyperopia (far-sightedness) – occurs when the distance between the lens and the retina is too short or the power of the lens it too weak, so light rays coming onto the eye from a near object will be focused on an imaginary spot behind the retina, receiving only a blurred image.

o Correcting these conditions – glasses, surgery to reshape the curvature of the cornea, a thin flap of corneal tissue is cut then folded back and a laser beam is applied to the exposed corneal tissue. The flap is then returned after it’s done.

o Cause and treatment of cataracts – condition where the lens grows cloudy and eventually become opaque, preventing light from the retina and the person becomes blind, cataract surgery involves replacing the damaged or cloudy lens with intraocular lens.

o Discussing the implications of this tech. for society – means thousands of people, who are cataract blind, can now see. Cataracts often happens in older people. With surgery these people can lead more independent lives. Fred Hollows Foundation brings affordable, sight-restoring eye surgery to indigenous Australians and very poor communities in other parts of the world. An estimated 3.5 million people are cataract blind in sub-saharan Africa. Many of these people will die within four years of going blind, their sight can be restored with the intraocular transplant operation that takes twenty minutes.

o Depth perceptiono Production of two different images can result in depth perception which

depends on binocular vision, in predatory animals the eyes are placed towards the front of the head, giving greater distance and depth perception. Animals that are preyed upon need to know what is approaching them. Their eyes are found on the side of the head, giving them wider fields of view but little depth perception.

The light signal reaching the retina is transformed into electrical impulseo Photoreceptor cells

The retina is a thin sheet of cells that contain photoreceptor cells, these contain light sensitive pigments.

Convert light images into electrochemicals signals that the brain can interpret.

Two types of receptors – rods and cones that contain photosensitive chemical substance that undergo reactions when they absorb light energy

o Distribution, structure and function of photoreceptor cells in the human eye Human eye has 125 million rods and 6.5 million cones Distribution – cones are most densely concentrated in the central

fovea, a small depression in the centre of the macula lutea. Rods are absent from the fovea and macula. They are more densely concentrated at the edges of the retina.

Function – rods function in dim light. Rods allow us to detect shape and movement and to discriminate between shades of light and dark. Cones are stimulated by bright lines. Cones are specialised for colour vision and visual acuity.

Insects – most insects have compound eyes with thousands of lenses each focusing light on a few photoreceptors

Simple light receptors are eyespots – patches of light sensitive cells used by some invertebrates, for example flatworms, to distinguish light from dark.

There are three types of cones – blue, red or green light, the pigments are almost the same as those in rods but require bright light and reform quickly.

o Colour blindness in humans In humans colour blindness results from the lack of one or more of

the colour-sensitive pigments in the cones. The most common type of colour blindness is red-green, in which the cones best receptive to red light and to green light are missing.

Colour vision is known to be present in bony fish, frogs, turtles, lizards and birds. Birds, as in many animal species, communicate by colour to signal breeding times, in courtship behaviours and as threat signals. Colour is also used in camouflage and mimicry. Colour vision is apparently rare among mammals, other than primates.

Sound is also a very important communications medium for humans and other animals

o Sound is a form of energy that requires a medium for propagation. Sound is a useful and versatile form of communication because it can be produced as well as detected. Sound can be used both day, night, when animals cannot see, smell or touch each other.

o Sound is produced by vibrating objects.

Diagram of fovea, macula lutea and retina

o Velocity = frequency x wavelength

o The structure of the human larynx The larynx is the voice box. Vocal cords are located in the larynx.

Vocal cords are flexible folds of muscle and ligament. They enable humans to make sounds that are then modified by the tongue, lips,

nose and mouth Terrestrial vertebrates – communicate by means of sounds

produced by the breathing system. Bats, for example, emit ultrasonic signals in their search for insects and other prey and to avoid obstacles in the darkness. Ultrasonic waves are a high

Diagram wave

Diagram of the human larynx

frequency sound waves. Ultrasonic signals are produced by the bat’s larynx

Fish – produce sounds by rubbing their fins or gills or by vibrating the swim bladder

Male grasshoppers – and crickets produce sound in two main ways: by rubbing the veins on the bases of their forewings together; or by creating friction between he inner surfaces of their hind legs

o Animals that produce vibrations also have organs to detect vibrations The detection of vibrations by insects, fish and mammals

Hearing is the ability to detect sound waves by changing the vibrations of sound to electrical energy of nerves. Hearing is only found in vertebrates and arthopods

Insects – only a few insects are capable of hearing – crickets, grasshoppers, cicadas, butterflies, moths and flies

Fish – have two main systems for underwater detection of sound: A labyrinth (series of tunnels in the ear) that contain sound

receptors A visible lateral line that runs along the body and contains

receptors sensitive to disturbances of the surrounding water. Fish have no middle ear cavity, ossicles or cochlea. In some bony fish, pressure on the air-filled swim bladder helps to conduct sound to the inner ear.

Mammals – hearing is most developed in mammals. Marine mammals, such as seals, close off their ear canals when diving. Vibrations are detected through special organs in their head. About 20% of known mammals use sound as their main way of ‘seeing’ their environment.

Sometimes parts of the human body, such as the stomach, can detect low frequency sound waves. This is used in cinemas with the effect called ‘sensuround’.

o The anatomy and function of the human ear

Structure FunctionPinna – the flap Collects sound waves from a wide area and funnels the sound into the

external ear passageTympanic membrane – eardrum

Stretched across the end of the auditory canal; separates the outer ear from the middle ear. Sound waves cause the tympanic membrane to vibrate. These vibrations are then conveyed from the tympanic membrane to the oval window by three tiny bones called the ear ossicles.

Ear ossicles Three intricately formed bones – the hammer, anvil and stirrup – transmit the sound waves to the inner ear. (sound vibrations travel well through bone)

Oval window and round window

The oval window and round window are two thin membranes. Sound reaches the inner ear at the oval window. Pressure is then transmitted in the fluid in the tympanic canal. This pressure causes the round window, at the end of the tympanic canal, to bulge outwards. The oval window helps to amplify the pressure of the sound vibrations.

Cochlea – snail-like spiral coiled tube, in the inner tube

The cochlea contains the receptors for sound and the vestibular apparatus that is associated with a sense of balance. As a result of the round window bulging outwards, fluid in the cochlear tubes vibrates

Organ of Corti Contains the auditory receptor cellsAuditory Nerve Transmits the sound vibrations to the brain

o Pathway of sound through through the external, middle and inner earo The path of sound: external ear (ear canal and ear drum) middle ear

(vibrations are transmitted by the ear ossicles – the hammer, anvil and stirrup) sound reaches the inner ear at the oval window (vibrations are transmitted through the oval window to the round window through the spiral cochlea containing fluid and nerve endings) impulse to auditory nerve auditory area of the cerebrum

Diagram of the human ear

Relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different frequencies

o Sound receptor cells in the organ of Corti are hair cells.