Life Of Stars By Nitin Mohan

Picture As supplied from http://zoomschool.com

Life Of Stars By Nitin Mohan
Stars are born in nebulae. Huge clouds of dust and gas collapse under gravitational forces, forming protostars. These young stars undergo further collapse, forming main sequence stars. Stars expand as they grow old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright. This is a red giant or a red super giant (depending on the initial mass of the star). It will eventually collapse and explode. Its fate is determined by the original mass of the star; it will become either a black dwarf, neutron star, or black hole.

Science Yearly 2005 - By Eugene Siu

Science Yearly 2005 Notes

Earth History

Intrusive Igneous Formations (Plutonic)

Plutonic rocks have larger grain sizes. They tend to form gabbros, diorites and granites.

Extrusive Igneous Formations (Volcanic)

Shield Volcanos

• low sloping sides


• fluid, low viscosity lava


• basalts

Strato Volcano

• steep sides


• higher viscosity lava


• may be explosive


• basalts, andesites, and rhyolites

Cinder Cone

• medium-steep sides


• basalts, ash, pyroclastic debris

Fossils and Sedimentary Rocks

• fossils are the remains of ancient plants and animals


• some fossils are found whole, e.g. insects trapped in tree sap, while others are found as imprints of the animal, such as a footprint or shell impression


• fossils can tell us what the environment the animal lived in was like


• fossils are generally found in sedimentary rocks


• organisms were generally destroyed before fossilisation


• occasionally they are found in other types of rock such as marble and slate, but they are generally damaged by the heat and pressure applied to the rock during its formation


• can only be found once the surface has erode to expose the sedimentary rock or if the rock is exposed by tunnels or mining


• fossils found in rocks are animals and plants that have died at the same time as the sediment layers were being laid down


• they are the same age as the layer of rock they are found in


• most fossils are the hard parts of animals


• many organisms fail to fossilise as the conditions must be perfect; oxygen must be excluded so that decay is slowed


• underwater fossils are much easier to be formed

Kinds of Fossils

1. Unaltered Soft Parts: if bacteria and mould can be prevented from decomposing the soft remains then a fossil can form that includes the soft parts of the body


2. Unaltered Hard Parts: in very recent fossils, the original hard parts may still be present


3. Altered Hard Parts: replacement occurs when the fossil’s hard parts, such as its skeleton, are replaced with other minerals such as pyrite


4. Trace Fossils: sediment packs hard around an organism such as a shell, then the impression of the shell in the hardened sediment is called a mould

Law of Superposition

The youngest rock layers are found on top of older rock layers. Intrusive igneous rocks are younger than the rocks they intrude on.

The Rock Cycle

1. Volcanic Activity


2. Weathering


3. Erosion


4. Transportation


5. Sea


6. Deposition


7. Sedimentary Rock


8. Heat and Pressure


9. Metamorphic Rock


10. Molten Magma- Source of Igneous Rock


11. Movement of plates causes earthquakes


12. Folding and Faulting


13. Uplift of Rocks

Sedimentary Rock Formation

Weathering

• Physical


• Chemical

Erosion

• transport : ice (glaciers), water (rivers as suspended load or bed load)

Deposition

• rocks come to rest of river or glacier bed, flood plain or ocean floor

Compaction

• deposition of new layers over old ones compacts older layers

Lithification

• compaction and cementation hardens sediments into rocks

Uplift and Erosion

• Rocks are folded and lifted to surface where they are subjected to new weathering and erosion.

Classification of Rocks

Sedimentary

1. Clastic: Conglomerate, Breccia, Sandstone, Siltstone, Mudstone, Shale


2. Chemical: Limestone, Dolostone, Evaporites


3. Biologic: Coal, Chert

Igneous

1. Intrusive: Gabbro, Diorite, Grandionite, Granite


2. Extrusive: Basalt, Andesite, Dacite, Rhyolite

Metamorphic

1. Foliated: Slate, Schist, Gneiss


2. Non- Foliated: Quartzite, Marble

Sedimentary Rocks

Sedimentary rocks may be made of rock fragments- sediments- or by chemical reactions.

Sediment Size Chart

Boulder: 256mm+
Cobble: 64-256mm
Pebble: 4-64mm
Granite: 2-4mm
Sand: 1/16-2mm
Silt: 1/256-1/16mm
Clay: less than 1/256mm


Roundness

The more rounded the grains the longer they have travelled and/or the faster they travelled. The 3 types are: Angular, Semi- Rounded, Rounded

Waves

Frequency- the number or repetitions per unit of time of a complete waveform
Wavelength- the distance between one peak or crest of a wave of light, heat, or other energy and the next corresponding peak or crest
Speed- the rate of measure of the rate of movement
Amplitude- the maximum absolute value of a periodically varying quantity

Transverse Waves

As a transverse wave travels through the medium, the particles oscillate along a path which is at right angles to the direction of motion of the waves which include visible light waves, radio waves and X-ray waves. Water waves approximate transverse waves, but the motion is more complex.  

Longitudinal Waves (compression waves)

The particles of the medium oscillate in the same direction as the waves travel. Where the particles are bunched up together is called a compression. Where they are spread out is called a rarefaction.

Sound waves are a good example of longitudinal waves. When a tuning fork is made to vibrate, the prongs move back and forth. They can travel through liquids, solids or gases.

Sound

Compression waves of energy transmitted by vibrating matter. A sound is compression waves. Particles move forwards and backwards along the direction of the wave.

Wave Direction

Particle Movement

The frequency of the wave is the number of complete waves to pass a point in a single sound. It is measured in hertz (Hz). Frequency and pitch are related. High frequency waves produce high pitched sounds and vice versa.
Speed waves eventually stop and cannot be heard because they travel in 3 dimensions and energy is needed to spread out in those 3 dimensions. Eventually the energy runs out.

Light

Light is a transverse wave. It is part of the electromagnetic spectrum. Different types of electromagnetic waves have different wavelengths. Electromagnetic waves all travel at the speed of light (300 000km/s)

Light is a very small part of the electromagnetic spectrum. Its wavelength is approximately 0.000 0005m. Microwaves and radiowaves have wavelengths if 10m. Gamma rays have the shortest wavelength and carry the most energy. It can cause injury to the cells of living things. In general, waves with shorter wavelengths have more energy.

Wavelengths (from shortest to longest)

Gamma rays, x-rays, ultraviolet, visible light, infrared, microwaves, radiowaves

Properties of Light

Absorption- When light hits an object, like soot, most of the light is absorbed so it looks black. When light hits a white object, most of the light is bounced back and the object looks bright.

Reflection- A handball bounced to another player bounces up at the same angle as the angle which it hit the ground. Light waves bounce in the same way.

Refraction- When you look at a ruler in a beaker, it looks twisted and doesn’t line up properly with the ruler out of the water. This is refraction. Your line of sight is bent by the glass and the water.

Reflection

The laws of reflection are:

1. The angle of incidence is equal to the angle of reflection.


2. The incident ray and reflected ray are in the same plane and on opposite sides of the normal.

  


A plane mirror gives an image as far behind the mirror as the object is in front. The image is also laterally inverted and virtual.

Regular reflection occurs with a smooth, shiny surface. It produces a clear image. Irregular reflection occurs with a rough surface where no clear image is produced.

Real images are those that can be projected on a screen. Although virtual images can be seen by the eye, these images cannot be focused on a screen.

Focus- the point where the rays of light meet when they are reflected

Concave mirror- telescopes, shaving mirrors
Convex mirror- rear-vision mirror

Scattering

Light waves bounce off and around as it travels so that it may reach your eyes from different angles. This process is called scattering. For example, the sky past the moon is space which is black but during the day, the sky is blue and in the evening it is red or yellow. White light is made of all the colours of the rainbow. When the light comes in straight down the atmosphere is thin and only a small amount gets scattered so the sky is blue, at sunset, the light has to travel further through the atmosphere and the blue light is scattered out so we don’t see it. We only see the reds and oranges which get through.

Refraction

Light waves travel at different speeds through different materials similar to how water waves travel in water. Notice how waves bend as they come into shore. This is because waves slow down as they reach shallow water while the waves in deep water are still travelling fast. As the light changes mediums through which it is travelling part of the wave will bend especially if it hits on an angle. The light on the inside hits first will slow down. When it changes on the other side, the bit that hits first speeds up.











Laws of Refraction

1. Light that moves at an angle from a less dense medium to a more dense medium bends towards the normal


2. Light that moves at an angle from a more dense medium to a less dense medium bends away from the normal


3. Light that moves straight on from one medium to another does not bend

In Sickness and in Health

Microbes

Viruses

These are the smallest microbes. They cannot be classified as cells because they do not have any cell structure. They cannot carry out any life processes. These characteristics make them appear non-living but if they are inside living cells they can replicate or reproduce themselves. There are many more viruses with many different shapes. They are a protein coat that holds the genetic material (strands of DNA). It is the protein coat, called a capsid, which determines the virus’s shape. They vary in shape from 1/100 000mm to 1/2000mm. Viruses cause the common cold as well as many serious diseases like polio, small pox, hepatitis and AIDS. When a virus comes into contact with a cell, it uses the cell like a factory, causing it to make more viruses.

Bacteria

Tiny, single-celled organisms that is very simple with few structures. Some are harmful and can cause disease while others are helpful. Bacteria have a cell wall and a cell membrane but no nucleus. The rigid cell wall on the outside may also be surrounded by a slimy capsule. The membrane surrounds the cell contents, including the genetic material. Some bacteria have pili or hairs and other s may have a long whip-like structure called a flagellum, which helps them to move. Some bacteria live as single cells while others cab live together in groups of 2 or 4. Some can form long chains and others can form grape-like branches called clusters. The size of bacteria vary from 1/10 000mm to 1/20mm. Bacteria reproduce by a process called binary fission. They simply divide into 2 identical cells. If conditions are ideal, bacteria can divide every 20mins to produce huge number sin a short time. Before division can take place, a bacterial cell must grow to twice it normal size and make enough genetic material for each new cell.

Protozoa

Protozoa are single-celled organisms that have a variety of shapes. These microbes have cell membranes that surround the cell’s contents or cytoplasm. The genetic material in these organisms is contained in a nucleus. Protozoa vary in size from 1/10mm to 2mm. Most protozoa are harmless but some cause serious diseases like malaria. Protozoa divide by binary fission.

Fungi

Most fungi are multi-cellular organisms, e.g. mushrooms. Their cells are surrounded by a cell wall. However, there are also single-celled fungi such as yeast. Fungi absorb nutrients from their surroundings by feeding in dead organisms or other non-living matter. They release digestive juices outside their cells to digest food. The chemicals they release break down the organic matter into simple substances that the fungi use as nutrients. Multi-cellular fungi have thread-like filaments called hyphae from which they absorb their food. Fungi also vary in size from 1/200mm to about 50cm. Some of the microscopic fungi can infect humans and cause diseases like thrush, ringworm and athlete’s foot.

Transmission of Microbes

Air:

• when people cough, sneeze or breathe, millions of microbes are released into the air


• dust particles that float in the air could contain pathogens or their spores


• e.g. whooping cough, tuberculosis, colds and flu

Contact:

• some highly contagious diseases are transmitted by physical contact with the infected person, e.g. smallpox

Food:

• bacteria reproduce very quickly if they enter food


• food is easily contaminated by microbes from the air or from the water


• e.g. typhoid, food poisoning

Water:

• untreated water that is polluted with sewage is the main source


• can be drunk, or may be used to wash hands that touch food


• poor water sanitation can result in cholera, dysentery and typhoid

Wounds:

• some pathogens can enter the body through cuts in the skin, e.g. tetanus, rabies (if bitten by animal with rabies)

Vectors:

• can be animals like mosquitoes, rats, cockroaches and house flies


• can pass directly or can be a link in a chain


• e.g. malaria, bubonic plague

Infectious and Non-Infectious Diseases

Disease

• ill at ease, sick, malady


• the result of the body not working correctly due to infection or injuries

Infection

• disease resulting from an invasion by microbes or other disease producing pathogens


• e.g. bacteria- cholera, virus- chicken pox and influenza, protozoans- malaria, amoebic dysentery, fungi- athlete’s foot and ringworm

Non-Infectious Disease

• a disease that can’t be spread to other people and was not caused by a pathogen


• e.g. hereditary- down syndrome, haemophilia, nutritional- obesity, anorexia nervosa, physiological- diabetes, cancers, environmental- cancers, deafness, lead poisoning

First Line of Defence

Skin:

• hardened outer layers of cell


• antibacterial and antifungal substances produced by sweat glands and oil glands


• bacteria that live on the surface of the skin

Mucous Membranes:

• found lining the alimentary canal, respiratory tract and the urogenital tract


• they secrete mucous which traps pathogens

Cancer

Cancer is a group of disease that result from uncontrolled cell division. This is called a tumour. An oncogene is a gene that causes cancer. A carcinogen is a chemical that causes cancers. Malignant grows into surrounding tissues and benign do not.





Chemistry

Structure of the Atom

Nucleus, Quarks, Proton, Electrons, Neutrons, Shells, Orbitals

Electrons have a negative charge
Protons have a positive charge
Neutrons have no charge
Protons and neutrons carry almost all of the weight of the atom. Electrons have 1/1840 of the mass of a proton.
Atomic mass is the average atomic weight of all the isotopes.

What makes elements different from each other?

The number of protons is what differentiates elements from each other. The number of electrons equals the number of protons. The number of neutrons can vary a little allowing for isotopes. Elements that have the same number of protons but different number of neutrons, e.g. Carbon 12- 6 protons, 6 neutrons and Carbon 14- 6 protons and 8 neutrons.

If an atom loses one or more electrons, it becomes positively charged- Cation. It becomes positive because it loses negatively charged electrons. An anion will be formed if an atom gains one or more electrons. It will become negatively charged because it gains more electrons. The difference between an atom and a molecule is that a molecule if formed when 2 or more atoms join. If the atoms of a molecule are the same, then it is an element.

First 20 Elements

1. hydrogen


2. helium


3. lithium


4. beryllium


5. boron


6. carbon


7. nitrogen


8. oxygen


9. fluorine


10. neon


11. sodium


12. magnesium


13. aluminium


14. silicon


15. phosphorus


16. sulphur


17. chlorine


18. argon


19. potassium


20. calcium

Valency- electrons available to donate or accept, e.g. Li+1, Be+2, C+-4, N-3, O-2, F-1, Ne

Isotope- an element that has different number of neutrons than its stable form, they can be added or removed naturally or artificially.

Radical- A group of elements that stick together in an element. The radical is always mentioned second, after the metallic element, e.g. sodium chloride.

Ions- Charged particles that have a different number of electrons than normal. A positively charged ion is called an anion and a negatively charged one is called a cation.

Naming Chemical Compounds

Two elements compounds- metal and non-metal

1. The metallic element is named first


2. The name of the non-metal element is shortened


3. The suffix ‘-ide’ is added to the shortened name

For example:
KBr = potassium bromide
MgO = magnesium Oxide
AlCl3 = aluminium chloride

Rules for naming a compound containing a radical

1. The metallic element is named first


2. The chemical radical is named second

For example:
MgNO3 = magnesium nitrate
Ca(HSO4)2 = calcium hydrate sulfate

Rules for naming compounds containing no metallic elements

1. The name of the first element is given in full


2. If only two elements are present, the prefixes ‘mon’, ‘di’, ‘tri’, ‘tetra’ and so on are used to indicate how many atoms of the second element are in the molecule


3. If only 2 elements are present, the name of the second is shortened and the suffix ‘ide’ is used as before


4. If more than 2 elements are present, the first is named, followed by the name of the radical

Electrolytes

Electrolytes are basically ions. When a substance dissolves in water it dissociates to form the ions which are free to roam around in the solution. They can be negatively or positively charged.

For example, when normal table salt (NaCl) is stirred into a cup of water it dissolves and forms stable ions. These are:

• sodium ion (Na+) cation


• chloride (Cl-) anion

The main electrolytes in your body are:

• Sodium (Na+)


• Potassium (K+)


• Chlorine (Cl-)


• Calcium (Ca 2+)


• Magnesium (Mg 2+)


• Bicarbonate (HCO 3-)


• Phosphate (PO4 2-)


• Sulphate (SO4 2-)

Valency refers to the bonding power of an element or radical (PO4 or OH). Can be determined from periodic table charge refers to the difference between protons and electrons in an ion (after it dissociates).

They have a number of uses both in the body and out of the body. The most important is that by having an electric charge they can allow a current to pass through a solution containing them. This is essential in the cell membrane of our bodies as they allow electrical impulses (nerve impulses and muscle contractions) to cross into other cells.

This is why it is essential to replace lost electrolytes when exercising as they are lost in sweat. Sports drinks have extra electrolytes such as sodium chloride and potassium chloride added to help replace those lost in exercise. The sugar and flavouring is added to enhance the flavour and provide extra energy.

Electrolytes also have the useful property of being able to be electrolysed to remove them from the solution. By running a current through the solution, the positive cations will precipitate out on the negative cathode and the negative anion will precipitate out on the positive anode.

Radioactivity

Marie and Pierre Curie discovered radioactive rays coming from certain elements. These elements have unstable nuclei. The radiation is given out as the element decays. The rate of radioactive decay is called its half-life (the time for half of the sample to decay to its daughter atoms), e.g. phosphorus 32 decays to stable sulphur atoms (its half-life) in approximately 14days.

3 Types of Radiation

Alpha Particles (α particle): α particle is 2 protons and 2 neutrons bound together. It is given off by an unstable nucleus and can be stopped by sheets of paper. It has a positive charge.

Beta Particles (β particle): β particle are electrons given out when a neutron decays. It is stopped by aluminium or 1cm wood and is negatively charged.

Gamma Particles (γ particle): γ radiation is very high energy electromagnetic rays. Not charged and they can travel great distances. It can be stopped by 2-3cm lead or several metres of concrete.

Background Radiation- Unavoidable radiation around you in the atmosphere and it is usually harmless.

Alpha, Beta and Gamma Decay

Alpha Decay Rules:

• mass number decreases by 4


• atomic number decreases by 2


• the element changes because the atomic number changes

Beta Decay Rules:

• mass number does not change


• atomic number increases by 1 (one neutron changes into one p+ and one e-. The photon remains and the electron is emitted)


• the element changes because the atomic number changes

Nuclear Reactions

Fission

When uranium is bombarded with neutrons, the neutrons make the very large uranium nuclei split into 2 smaller nuclei, with 2 or 3 more neutrons being given off. At the same time large amounts of energy were released. This splitting of atoms is called fission.

Fission reactions which give off 2 or 3 neutrons have a very special property. Each of the neutrons given off in a fission reaction can in turn strike another nucleus and be absorbed into it. This will cause another splitting which, in turn, produces 2 or 3 more neutrons and releases even more energy.

This process is known as a chain reaction. Unless the number of neutrons which are produced is controlled, this process becomes faster and faster, and in a vert short time huge amounts of energy are released because of the large amounts of atoms being split.

If there is only a small amount of uranium present, the fission process will proceed very slowly. This is because most of the neutrons produced will escape into the air or will not have the correct amount of energy to split other uranium atoms. However, if a piece of uranium is pure enough and is bigger than a certain size, called the critical size, most of the neutrons will not escape. They will go on to split other uranium atoms.

Nuclear Reactors

The purpose of a nuclear reactor is to control the chain reaction in nuclear fission to generate electricity.

Rods made mainly of uranium oxide are placed in the reactor between large blocks of graphite. The graphite is called the moderator and acts to slow down the neutrons so they can more easily split atoms. The pile of graphite blocks with uranium between them is enclosed in special concrete and steel walls. These are to protect the outside from exposure to the very dangerous and powerful radiations produced in the reactor. Control rods, which can be pulled out in and out of the pile, absorb neutrons which are released by the fission of uranium. If the control rods are pushed right in, they will absorb enough neutrons to stop the chain reaction going on in the reactor.

Not all reactors use graphite as the moderating material to slow down the neutrons. Some use heavy water.

Nuclear Waste

Mining and processing uranium ore and the subsequent use of uranium in power stations, nuclear power engines (submarines) and the nuclear weapons industry all produce radioactive waste products.

The disposal of that radioactive waste is a problem for all countries using nuclear power. Radioisotopes with short half-lives can be stored in shielded containers until they are safe, but the storage of long-living isotopes for thousands of years is a real problem. Several alternatives have been suggested and tried:

1. Dumping in sea


2. Storage in vaults


3. Storage in mines


4. Synroc


5. Firing into space


6. Transporting the waste

Radioisotopes

Isotopes are atoms of an element that have different numbers of neutrons in their nuclei. Some are stable and some are not. Those that are not can decay or break up giving off high energy radiations and forming different atoms. These unstable isotopes are called radioisotopes. Radioisotopes can occur naturally or made artificially made in a nuclear reactor.

The isotopes or carbon both occur naturally. Carbon-12 is a stable isotope. It is not radioactive. However, carbon-14 is formed when high energy cosmic rays hit caerbon-12 atoms. The percentage of Carbon-14 in the air is 0.000001%.

There is only one nuclear reactor in Australia in Lucas Heights, Sydney. It is used for making radioisotopes for medical use.

Treating Cancers:

A high dose of radiation, often from the cobal-60 isotope, directed at cancer cells can kill them. Unfortunately, despite the development of machines that can direct very thin beams of radiation onto cancer cells, the radiation also affects any healthy cells it passes through. Often it doesn’t kill all the cancer cells so the cancer may reappear later.

Chemotherapy:

Makes use of the fact that some parts of the body absorb some elements and others do not. The thyroid gland absorbs iodine. A person with thyroid cancer could be given an injection containing a measured does of radioactive iodine, which would be concentrated in the thyroid and hopefully kill the cancer cells there. Of course, while it is flowing through the bloodstream the isotope can kill many other cells.

Bone Scans:

Technetium-99 is absorbed by injured bones but not healthy bones. Technetium-99 injected into the bloodstream will concentrate at any bone injury and can be detected using a gamma camera.


Radioactive Tracers:

Used to study how plants absorb different chemicals, how water flows through the ground, or how and element behaves in a chemical reaction. To follow a leak in a pipe, radioisotope is added to the water and the leak pinpointed by detecting radioactivity at the surface where water leaks out of the pipe.

Detecting Flaws:

Radioisotopes are used inside a pipe or on the other side of a metal sheet. Any flaws in a welded join in a pipe or in the internal structure if a metal sheet itself can be detected if any radiation appears through the weld or on the other side of the sheet. Stress fractures in aeroplane wings are detected this way.

Astronomy

Astronomical Distances

The unit that is chosen for most distances in space is called light years. The light year is the distance that light travels in a year. Light travels at 300 000km/s. 1 light year is approx. 10 000 000 000 000 000 km.

Astronomical Unit:

• the average distance between the earth and the sun (approx. 150 000 000km)

Parsec:

• the distance at which the baseline of length 1au subtends an angle of 1 second (one-sixtieth of a degree)


• one parsec is about 30 857 200 000 000 km

Brightness of Stars

The apparent magnitude is a measure of the brightness of a star viewed from earth. It is a measure of the flux of the star, which is the amount of light received by the viewer.

The absolute magnitude is the apparent magnitude of the star if it was 10 parsecs away from earth. A star 10 parsecs away from earth would have the same apparent magnitude as its absolute magnitude. It is a measure of its luminosity, which is the total amount of energy radiated per second.

Absolute magnitude is more useful that apparent magnitude for comparing stars. It removes the problems associated with a star being much further away from earth, which will make it appear less bright. By removing the distance factor all stars can be compared on their actual brightness and strength of radiation.

Star Fuel and Nucleosynthesis

Stars are giant nuclear reactors. In the centre of stars, atoms are taken apart by tremendous atomic collisions that alter the atomic structure and release an enormous amount of energy. This makes stars hot and bright.

Nuclear fusion is an atomic reaction that fuels stars. In fusion, many nuclei combine together to make a larger one (which is a different element). The result of this process is the release of a lot of energy (the resultant nucleus is smaller in mass than the sum of the ones that made it; the difference in mass is converted into energy by the equation E=mc2).

Stars are powered by nuclear fusion in their cores, mostly converting hydrogen to helium.

The production of new elements via nuclear reactions is called nucleosynthesis. A star’s mass determines what other type of nucleosynthesis occurs in its core (or during explosive changes in its life cycle). Each of us is made from atoms that were produced in stars and went through a supernova.

Small stars- the smallest stars only convert hydrogen into helium

Medium-sized stars- (like our sun) late in their lives when the hydrogen becomes depleted stars like our sun can convert helium into oxygen and carbon

Massive stars- (greater than 5 times our sun’s mass) when their hydrogen becomes depleted. Light mass stars convert helium atoms into carbon and oxygen, followed by the fusion of carbon and oxygen into neon, sodium, magnesium, sulphur and silicon. Later reactions transform these elements into calcium, iron, nickel, chromium, copper and others. When theses old, large stars with depleted cores supernova, they create heavy elements (all the natural elements heavier than iron) and spew them into space, forming the basis for life.

The Colour and Temperature of Stars

Colour (K= Kelvin)

Blue: 30 000K
White: 15 000K
Yellow: 6 000K
Orange: 4 500K
Red: 3 500K
Determining a star’s temperature from its colour

Scientists use filters on their telescopes to view light from only certain wavelengths (colours). The wavelengths at which the most energy is given out will be the brightest.

Wein’s displacement law is a formula that links the wavelengths of light at which the most energy is given out are the objects temperature.

In this way a star’s surface temperature can be determined. Hot stars thus brightest at short wavelengths (blue-white stars).

Cool stars are brightest at long wavelengths (orange-red stars).

Dopplershift/Hubble’s Law

The Dopplershift is a shift in wavelength of frequency of a wave due to relative motion of the source and receiver. If the source if waves is moving towards the receiver (or vice versa) each successive wave, it is emitted a small distance closer to the receiver, the wavelengths will be closer together and the wave will be squashed (shorter wavelengths and higher frequency). Similarly, if the source of waves is moving away from the receiver each successive wavecrest is emitted a small distance further away, the wave crests will be further apart and the wave will be ‘stretched’ (longer wave lengths, lower frequency). This is the phenomenon that causes the apparent shift in pitch (from higher approaching to lower receding) as a train passes by sounding the whistle.

These Dopplershifts have been used to determine the most stars are in fact moving away from each other. The light from stars has been examined and it shows that most light is shifted towards the red end of the spectrum, hence a red shift.

It can be used to measure distance. It refers to a change in wavelength caused by relative speed. As an object producing a sound approaches an observer, the wavelength of the sound is shorter and the sound produced is perceived to have a higher frequency than when the object is moving away from the observer. This everyday phenomenon also applies to light. The Doppler Shift of an object that is receding quickly (and thus further from the Earth). Because the universe is expanding at a tremendous rate, the distant nebulae we want to observe are moving at a very high speed. The more distant a nebula is, the faster it is moving away from us. From our viewpoint it’s just as if our galaxy ware at the centre of the universe.




Transformation of Radiation into Matter after the Big Bang

One of the basic predictions of the Big Bang theory is that the universe is expanding. This expansion indicates that the universe was smaller, denser and hotter in the distant past. At various times in the universe’s history, the temperature has gone down in proportion to the universe.

Since the universe was really hot through most of its early history, there were no atoms in the early universe, only free electrons and nuclei. The cosmic microwave background photons easily scatter off of electrons. Thus photons wandered through the early universe.

Eventually, the universe cooled sufficiently that photons and electrons could combine to form neutral hydrogen. This was thought to occur roughly 3 minutes after the Big Bang when the universe was about one-eleven hundredth of its present size. At the same time helium and deuterium were being created.

Elements heavier than lithium are all synthesised in stars. During the late stages of stellar evolution, massive stars burn helium into carbon, oxygen, silicon, sulphur and iron. Elements heavier than iron are produced in two ways: in the outer envelopes of super-giant stars and in the explosion of a supernova. All carbon based life on Earth is literally composed of star dust.

The Standard Big Bang Model

There was a big bang some 15 million years ago, when the size of the universe was zero and the temperature was infinite. The universe then started expanding at near light speed. The sequence of events in this model is:

Time t = 0 (15million years ago)
Radius = ∞
Temperature T = infinite
Density = mass per volume = infinite

t = 0.01 seconds
T = 1000 000 000 000°C
Energy is mostly radiation

t = 2 seconds
T = 10 000 000 000°C
Density = 100 million kg per cubic metre
Proton-antiproton and neutron-antineutron pairs begin forming

t = 3 minutes
T = 1 000 000 000°C
Protons and neutrons begin forming hydrogen and helium
t = 20 minutes
About 25% if the protons and neutrons in the universe are now helium
T = 10 000 years
Density = 0.000 000 000 000 000 01 kg/cubic metre
Most energy is now mass, not radiation
Condensation into stars begins

t = 15 billion years (now)
T = - 270°
Density = 10^-27 kg/cubic metre

Dynamic Earth

Story of our Continents

The continents have not always been where they are now. They used to be all joined in a giant super continent called Pangaea. This continent split into 2, Laurasia and Gondwana. Gondwana broke up and the continents moved towards their present positions.

The forces that drive the movement of the continents are found within the Earth. When material is heated up it will rise up, move across whatever boundary it comes into contact with, until it cools down when it will fall back to the heat source. This process is called ‘convection’ and it happens in the asthenosphere, a partially molten region part of the mantle below the crust (100-700 km deep). The continents move around very slowly (2-20cm/year) riding or surfing on these convection currents.

The continents however, do not move smoothly, because of the asthenosphere is only partially liquid and the continents are solid. They sometimes stick against each other. When the continents get stuck the pressure builds up and eventually the continents will ‘slip’ past each other. This causes earthquakes and volcanoes. This leads to a common link between the continental plates and earthquakes and volcanic activity around the edges of plates.

Plate Boundaries

Type of Boundary

Subduction/convergent:

• occur when a thinner oceanic plate collides with a thicker continental plate


• located between South American Plate and Nazca Plate


• causes both volcanoes and earthquakes

Collision:

• two continental plates colliding


• between Australian Plate and Eurasian Plate


• causes both volcanoes and earthquakes

Divergent:

• two plates move away from each other


• between South American and African Plates


• causes volcanoes

Transform Fault:

• two plates slide past each other


• Pacific plate moving past North American Plate


• Causes earthquakes

Folding and Faulting

Folding is when land is compressed to form mountains or valleys (anticlines or synclines). The land does not break. Can occur away from earthquake zones. Faulting is when land slips past other land. The land is broken. It occurs near plate boundaries.

Types of Faulting

Transform Fault
Normal Fault
Block Faulting
Horst Fault
Reverse Fault


By Eugene Siu (thanks a heap, this guy contributed a ton!!!) Everyone rememba to thank him!!!

Science Notes by: Unknown

Topic 1 – Atomos: Inner Space

• Atoms: Elements and compounds made up of atoms. 1 element = 1 type of atom. COMPOUND is 2 or more types of atoms.


• Atoms: ELECTRONS, NEUTRONS AND PROTONS.

If there are the same number of protons and electrons, the atom is neutral.

• Atomic Number: number of protons


• Mass Number: sum of number of protons and neutrons.


• Atomic mass unit: proton = 1, neutron = 1, electron = 0


• Isotopes: atoms of the same element which have a different number of neutrons. E.g. Argon 36, 38, 40. Lithium 6, 7. Bromine 79, 81.


• Ions: atoms which are negatively or positively charged. Combine to form new compounds.


• Electrons: matter = mass and volume.

                              Same charge = repel
                              Unlike charge = attract

• Shells: 1 = 2 max.

                  2 = 8 max.
                  3 = 18 max.
                  4 = 32 max.

• Periodic Table: The arrangement of elements in order of increasing atomic number. Includes, metals, non-metals, semi-metals.


• Radioactivity: The spontaneous decay of unstable nuclei, releasing matter and energy in the process. As nucleus breaks down it emits radiation in particles or rays. Marie Curie discovered radio activity.


• Radioactive decay: (Alpha, Beta and gamma radiation)


• ALPHA PARTICLES – 2 protons, 2 neutrons, positive, travel few cm’s in air, stopped by thickness of a sheet of paper.


• BETA PARTICLES – electron, negative, travel few m’s in air, stopped by sheet of aluminium, 1 cm thick wood.


• GAMMA RAYS – high energy, not charged, travel few km’s, stopped by thick concrete wall, 2 – 3 cm’s thick lead.


• Background Radiation: the radiation which surrounds a particular area. E.g. school lab. It is measured in sieverts. ( 1 million msv = 1 sv)


• Half-Life: Impossible to predict exactly when nucleus will decay. Half life is the time it takes for exactly half the nucleuses present to decay. Its rate is constant.


• Effects of Radiation: Alpha, beta and gamma rays and x-rays = ionizing radiation. They disrupt atoms as they pass through       changing them to ion. Large doses of radiation can kill cells. Sever radiation exposure = immediate death. Lower dose of radiation can damage body, chance of cancer. 1 msv per year is recommended (excluding background and medical).


• Radioisotopes: Unstable isotopes emit radiation.


• TRACERS – Used to follow path of atoms. Can reveal structure/ functioning of organs.


• GAMMA RADIATION – Used to sterilize food, medical supplies, treat cancer.


• NUCLEAR REACTOR – Device for making radioisotopes.


• CYCLOTRON

- Phosphorus 32 (leukaemia)        - iron 59 (blood diseases)
- Cobalt 60 (cancer)                    - Barium 137 (digestive illnesses)
- Iodine 131 (Thyroid)                 - Carbon 14 (artefacts). When a plant  
                                                      dies, it takes in no more C 14 and
                                                     present C 14 decays.    

• Nuclear Fission: Nuclear energy is released when changes occur in nucleus. Nuclear fission is splitting heavier atoms into lighter atoms. When this occurs 2 or 3 neutrons, heat energy and gamma radiation is released.

• Advantages and Disadvantages of Nuclear Energy:

Advantages

• PRODUCING POWER – electricity, ships, submarines


• MEDICINE – * radioactive isotopes (tracers) for organs, tumours, cancers

                           * nuclear medication
                                 * radiation services for human bones, tissue                      

• INDUSTRY – Radiation – how fast it wears off moving tyre, thickness of metal strips, how fast liquid/ gas flows through pipes

                             - Lucas Ht Reactor – radiate large crystals of silicon into wafers (video cameras, fax, and air conditioning)

• AGRICULTURE – Isotopes (tracers) – animals/ plants


• ENVIROMENT – Monitor pollution and erosion

Disadvantages

• WEAPONS – war


• RADIATION – cause damage to humans (cancer)


• NUCLEAR WASTE – need safe methods of disposal

Topic 2 – Shaking All Over

Layered Structure of the earth

• Crust: thin layer of rock. Forms continents and islands. Thickest under continents (60 km) and thinnest under ocean (10km).


• Mantle: Thick layer (2800km) of rocks. Upper part is in a ‘plastic state’ (magma) which comes to surface when volcanoes erupt.


• Core: Consists of large ball like shape in middle. Two parts: the inner core (solid) and the outer core (liquid).

Plate Tectonic Theory: Based on theory that earth’s crust is broken into 12 plates which slowly move. ‘Tectonic’ means forces which lead to movement. This is determined using satellites. Forces come from the ASTHENOSPHERE, region below the solid lithosphere. CONVENTION CURRENTS cause the movements from here.
Surface Features created from Plate Collisions: Collide on land or under sea.

• Deep Sea Trench: When 2 plates collide under sea and one plate pushes under another. Slipping between plates earthquakes. As plate is pushed deeper, rock melts.


• Volcanoes/Earthquakes: when a plate with a continent on it collides with a plate under sea. Friction of plate, melts rocks. Melted rock pushes up forming mountains eg. Andes Mountains.


• Fold Mountains: when two plates both with continents collide and rock material piles up.


• Faults: When plates slide by each resulting in earthquakes. Comes in jerks e.g. San Andreas Fault in CA, U.S.A.


• Mid Ocean Ridge: Found in the Atlantic Ocean, almost all around the world. Deep trench found in the middle and molten material forced up forming new crustal material.

Earthquakes:Natural phenomena caused by movements of earth’s crust. (compression or tension). Caused by slipping between plates and plates sliding by each other. Located usually on edge or near plates.
Detecting an Earthquake: energy released causes waves that spread out in all directions.

• P Waves: Primary, monitored first. Compression waves (shake in wave direction). Fastest waves at 5-13 km/s. Can travel through solid and liquid. Least destructive.


• S Waves: Secondary, monitored second. Transverse waves (shakes across the wave direction). Faster than L waves- 3-8 km/s. Travels through solid only.


• L Waves: Long, monitored last. Transverse waves. Slowest waves at 3-4 km/s. Surface waves only and most destructive.

Earthquake waves recorded on SEISOMETERS to form SEISMOGRAMS.
Scales: MERCALLI – (what happens and how people respond). Roman numerals.
                RICHTER – (measurement of size, amplitude)

• Locating Earthquakes:


• FOCUS – the place where the slip occurs. Small area or a long line.


• EPICENTRE – the point or line directly above the focus


• Three seismographs at 3 different places. 3 arcs drawn on a map using distances derived from time-travel curve (difference between P and S waves). Radius of arc is the distance to the earthquake. Point where arcs intersect is the location of earthquake (epicentre).

Effects of Earthquakes:

• shaking of ground


• horiznyal warping


• cracks in surface


• changes to stream course


• tsunamis


• land/mud/ice slides


• damage to buildings, roads rails and fencing.


• Fires from pipes


• Loss of life

Evidence for Continental Drift:

• Wegener’s Ideas:

Many of the continents ‘fit’ together, just like a jigsaw puzzle (movement of continents)

• ‘Pangaea’ – super continent


• North America, Europe and Asia form ‘Laurasia’


• Antarctica, Australia, India, Africa, and South America formed ‘Gondwanaland’.


• Both split into separate continents

Many rock types and ages are similar between continents (glaciation and tillite). There are a number of ancient climatic zones in lands which are very different to their climates today. There is a certain distribution of many fossil plants and animals across different climates. These similar or identical fossils occur on continents now far away.

Volcanoes: various types of eruptions. Depends on plate boundary.

• Explosive Eruptions: where plates collide, periods of violent and quite activity, mainly ash, lava bombs and gases.


• Quieter Eruptions: lava moves out flows down         steep cone with layers of ash and lava called COMPOSITE CONE.


• Cinder Cones: steep cones made entirely of ash and rock.


• Shield Volcanoes: low, flat cones with little ash formed from lava of large volcanoes which have built up from the seafloor.


• Mid-Ocean Ridge Volcanoes: located where plates separate on ocean floor. Quieter eruptions.


• Volcanic Island Chains: form as the plate moves over a hot spot or magma chamber in the upper mantle.


• Intrusions: movement of magma up through structures.


• ####: cuts across bedded rock.


• Sill: parallel to beds of rock. Form between beds.


• Batholith: large dome shape.

Joints: (tectonic plate movement can result in joints) Joints are cracks in the earths crust

• Faults: formed when compression/ stretching forces cause blocks to move or   against each other.


• Joint: cracks are joined up and level.


• Normal Fault: when right side of block moves up and the left side moves down, both stretching forces.


• Reverse Fault: when right side moves down and left side moves up, both by compression forces.


• Normal Fault: earth’s crust increases.


• Reverse Fault: earth’s crust decreases.


• Folding: Changes in crust cause folding, faulting and tilting. Folding results from sideways pressure on rock layers.


• Strata: horizontal layers.

Topic 3 – Chemistry in the Home

• Matter: particles which can be arranged in different ways.


• Elements, Compounds and Mixtures:

Elements: Substances that are made up of one type of atom only. Sulphur, lead, mercury, copper.
Compounds: substances which are mad up of at least 2 different kinds of atoms joined together by chemical bonds. Hydrochloric acid, ammonia, sodium chloride.
Mixtures: made up of at least two elements. Washing powder, sodium hydroxide 0.2H

• Atoms and Molecules:

Atoms: Simplest form of matter, smallest unit of an element. Consists of a single particle.
Molecules: Made up of 2 or more atoms joined together by chemical bonds.

• Common Chemical Properties:

Acids: All acids are substances that contain hydrogen that can be released as hydrogen gas when a metal is corroded by the acid. Antaciols neutralize or destroy the properties of the acid to produce a neutral solution.
Bases: compounds with properties opposite of acids

• Alkalis: soluble bases that contain a group of charged atoms called the hydroxide ion (OH  )


• Salts: sodium chloride= table salt. Ionic compounds formed when acids and bases react together (neutralization).

Acid + base              salt + water. Properties of acid and base are destroyed, new substance formed. Salt formed can be recovered by evaporation and filtration (precipitate formed).
RULE: Salt = 1st part of base and 1st part of acid.
E.g. Sodium hydroxide + hydrochloric acid        sodium chloride + water.

• Carbonates: Ion = CO (valency is -2).


• Hydrocarbons: Molecules that are only made up of hydrogen and carbon.


• Compound Groups:

Molecular Compounds: (covalent: both non-metals).

• don’t conduct electricity in solution/


• aren’t uncharged


• solutions of molecular compounds are non-electrolytes


• Prefixes used e.g. Carbon dioxide, water.


• E.g. Nitrogen monoxide, methane.

Ionic Compounds: (metal and non-metal)

• ion – charged atom


• atoms of metallic elements usually form positive ions


• atoms of non-metallic elements usually form negative ions


• charge of an ion = valency


• POLYATOMIC IONS = when some ions consist of groups of atoms such that the group as a whole has gained/ lost 1 or more electrons. E.g. nitrate, sulphate.


• Ionic compounds formed from an ionic bond, when oppositely charge ions are attracted to each other.


• E.g. sodium carbonate, aluminium nitrate.

• Chemical Bonds: Bonds are strong forces that hold atoms of elements together

Covalent Bonding: Atoms share one or more of each other’s outer electrons. Two or more NON-METALS combine to form compounds that have MOLECULES.
Ionic Bonding: When a nucleus with a stronger attraction COMPLETELY takes over one or more outer electrons orbiting another nucleus. Results in a positive and negative ion which then attract each other. They are formed when METALS and NON-METALS react to usually produce an ionic crystal lattice.

• Equations/ Formulas:


• writing formulas for ionic compounds: charges of ions (valencies). Sum total of charges = 0. Positive ions symbol written first. The number following the symbol = number of atoms/ ions of the element.


• Remember to BALANCE equations!!! Put in brackets. Number to be placed only at FROMT of formula.


• Chemical reactions = reactants                products

• Combustion and Fire: fuel + oxygen                carbon dioxide + water


• fuel combines with oxygen to release energy.


• Requirements: ignition source, oxygen, fuel


• Extinguishing fires: * remove/ separate unburnt fuel, remove ignition source, remove oxygen supply


• Common fuels: wood, petrol, methane


• Common ignition sources: frictional heat, matches, cooking appliances

Aborigines used fire for:

• driving animals from bush


• cooking


• regeneration


• prevent natural fires

Bushfires in Australia:

• dehydrated foliage ignites and releases burst of heat radiation


• oils and waxes in eucalyptus leaves readily ignite and cause green leaves to burn.

• Corrosion: fuel + oxygen            carbon dioxide + water


• slow decay/ degradation of metal resulting from contact with gases and liquids in enviroment (rust)


• protection: coat with protective barrier to keep out moist air using substances like vaseline

• Precipitation: soluble salt + soluble salt               insoluble salt + soluble salt


• insoluble compounds which form when solutions containing positive and negative ions are mixed


• when one compound is INSOLUBLE and the other is SOLUBLE


• compounds switch around

eg.  silver    +   potassium          silver       +    potassium
       nitrate         chloride           chloride           nitrate
         (aq)             (aq)                  (s)                   (aq)

Aqueous = not pure liquid

• Acids on Metals: metal + acid              salt + hydrogen


• Aim: observe the reaction of acids on metal


• Results: metal dissolved and hydrogen was produced.


• Conclusion: when metals react with acids. Hydrogen gas and a salt is produced.


• Eg. zinc + hydrochloric acid                zinc chloride and hydrogen

• Neutralization: acid + base               salt + water


• when bases and acids react together and form salts


• see ‘salts’ 3 pages back.

• Indicators and Colour changes:


• indicators are chemicals which change colour according to acidity/ basicity of enviroments


• use acid/ base indicators to test level of acidity/ basicity of chemicals.

Litmus:

• red in acidic solutions


• blue in basic solutions (alkali)


• doesn’t change in neutral solutions

Phenolpthalien:

• magenta in basic solutions


• colourless in acidic and neutral solutions

• Acids on Carbonates: acid + metal carbonate             salt + carbon dioxide + water

• Decomposition: compounds can be decomposed by heat.

Topic 4 – Field Studies

• Biotic: the biological components of the environment.

Biotic factors that affect an ecosystem:
- competitors – food – shelter – predators (2nd order consumers) – producers (make food by photosynthesis)  
- 1st order consumers (herbivores)

• Abiotic: parts of the environment which are non living. Includes physical and chemical.

Abiotic factors that affect an ecosystem:
- air/water temp.    - wind speed/ direction   - humidity
- depth/ speed of water    - characteristics of the soil    
- acidity of water/ soil    - salinity of soil/ water    - light penetration in water    - light penetration of canopy

• Balance of Nature: an ecosystem is an area and the community that lives in it. The system involves giving and taking between living and non-living. In nature, ecosystems are in BALANCE. Enough light energy is taken in to replace the energy lost in heat, and matter is cycled between the community and its surroundings.


• Methods to estimate plant and animal pop.


• QUADRANT SAMPLING: sample square placed at random and the population is measured within the squares. Cons: not good for animals that move.


• CAPTURE RECAPTURE: involves tagging a sample of the pop. Then calculations are made of the proportion of marked animals in a recaptured sample.

Total Pop. =       # of tagged animals x # recaptured  
                       Average # of tagged animals recaptured
Cons: trapping techniques are hard to master

• Impact of Human Activity on Australian ecosystems


• removal of trees and clearing of land for agriculture


• introduced species.


• Clear land for cities- destroy ecosystems


• Dams are built


• Transportation systems built e.g. roads, rail


• Disposal of waste – sewage system, garbage removal


• Removal of other man-made materials


• Photosynthesis: occurs in producers.

Two outcomes (a) light energy stored             stored chemical energy
                        (b)  carbon dioxide and water                  sugar and oxygen

• Respiration: a process where sugar is broken down for the energy it contains


• Australian Ecosystems:

-DESERT- widely spaced grasses, salt bush, high temp., low rain
-GRASSLANDS- spinifex grasses, very low coverage >30%  
  < 500mm rainfall, temperate or tropical
- SHRUBLANDS- mallee, mulga 30%-70% coverage, low rain, high
   temp.
- WOODLANDS- trees, shrubs, grasses, widely spaced canopy, low
   coverage w/ shrubs, high rain in tropical, temperate or tropical.
- ALPINE- snow gums, heaths, continuous cover, variable rainfall (or snow), temp. increases with altitude.
- SCLEROPHYLL FOREST- trees (jarrah, blue gum), shrubs, grasses, open canopy but ground cover, rain depends, no distinct seasonal rain, warm temp.
- RAINFOREST- trees (cedars, southern beach), lianas, ferns, dense canopy, distinct layers within, high rain, temperate or tropical (little season variation)
- REEFS & MARSHES- mangroves, reeds, dense growth, temp. and rain vary at different spots on the coast

• Key Vocabulary

PIGMENT: a chemical that absorbs light energy
BIOSYNTHESIS: a process which the chemical of the body are built from other (simpler) chemicals.
REDUCER: organism that breaks down other organisms into simpler things.

Topic 5 – Seeing is Believing

• Sight: sight is caused by rays of light which are reflected of an object. These rays carry with them an image that enters our eye.


• Light: light travels in straight lines and at a constant speed as long as the medium it travels through doesn’t change. Light travels at 300’000 kms -1 in a vacuum but slows when entering more dense mediums. Light may change direction (refract) when passing through different mediums leading to optical illusions. Light is a form of energy that travels as a transverse wave.


• Transverse Wave: as it travels, the particles themselves oscillate along a path that is at a right angle to the direction of motion of the wave. E.g. light or radio waves.


• Longitudinal Waves: The particles of the medium oscillate in the same direction as the waves travel. Also know as compression waves. E.g. sound waves.


• V = f    used to work out measurement in a wave.

                       Wavelength=
                       Frequency = f Hz (hertz)
                       Amplitude   = a metres
                       Velocity       = v ms-1
                       Period/ wavelength = T
                       f = 1/ T     T = 1/f    

• Laws of Reflection: Governed by two laws.

(1) The angle of incidence is equal to angle of reflection
(2)  The incidence ray and reflected ray are in the same plane a, and on opposite sides of, the normal.

• Refraction: The bending of light rays as they travel from one medium to another.

GLASS RECTANGULAR PRISM:  as it passes through the prism, the light travels away from the normal.
CONCAVE LENS: the rays of light diverge
CONVEX LENS: the rays of light converge

• Translucent Objects: A translucent object let light through, but the direction changes. E.g. frosted glass


• Transparent Objects: allows light through with very little change to direction. E.g. clear glass


• Opaque Objects: doesn’t allow light to pass through. E.g. wood, bricks. Colour is caused by some of the waves that make up visible light being absorbed and some reflected. Black: all absorbed   White: all reflected.


• Human Eye:

RETINA: layer at back which detects image. Contains sensitive nerve endings which detect light.
CORNEA: transparent bulge at front. Window that allows light to enter.
LENS: convex lens. Tough, flexible and transparent. Helps focus light rays on retina.
CILIARY MUSCLES:  muscles that control the curvature and shape of the lens thus power of the lens.
CHLORIOD: thin black layer on the inside of the sclerotic coat. Absorbs all light after it’s passed through the retina.

• Short Sightedness: can see near objects clearly but not distant ones. Corrected with concave lens.


• Long Sightedness: can see distant objects clearly but not near ones. Corrected with convex lens.


• Dispersion: the spreading out and separation of light rays as they are dispersed. Into separate colours.


• Different forms of Electromagnetic Radiation

Wavelength (m)                       Type                 Uses
100                                      Radio waves         radio
                                              Microwaves

1                                                                       microwave ovens
  
1/ 1000
                                              Infra Red              electric fires

1/ million
                                              Light                    electric lighting
                                              Ultra violet           ultra violet lamps/                                                                                                                        
                                                                          Sunbathing
1/ 1000 mil.
                                             X-rays                 x-ray photographs

1/ Mil. Mil.                          Gamma rays            radio activity


Topic 6 – The Body Under Attack

• Microbes: microscopic organisms


• Pathogens: Microbes that cause disease.


• Kingdom Monera: Bacteria and cyanobacteria belong in this category. Their cells do not have a nucleus with a membrane. A cyanobacterium is 20 um in size. A bacterium is approx. 5 um in size (types include spirillum, bacillus and coccus). Tuberculosis and tetanus are both members of this kingdom.


• Kingdom Protistia: Many unicellular organisms as well as algae belong in this kingdom. Their cells have membrane- bound nuclei. They are approx. 50 um in size. The kingdom includes amoeba, ciliates and flagellates. Protozoa that cause malaria and sleeping sickness are part of this kingdom.


• Kingdom Fungi: Fungi are organisms that do not contain chlorophyll but their cells are surrounded by cell walls and have membrane bound nuclei. They are approx. 100 um in size and include yeast (which is beneficial to us), bread mould and penicillin. Tinea and thrush are examples of pathogenic fungi.  


• Viruses and Prions: Viruses are bodies much small than cells which are composed of some genetic material (codes required for reproduction and control) surrounded by a protein coat. Viruses cannot reproduce unless they first invade a host cell. Influenza, polio, mumps and AIDS are caused by viruses. They are approx. 100 nm in size. Prions are protein particles that cause disease such as Creutz- Jakob disease and Mad Cow Disease.


• Resisting/ fighting Micro-organism Infection

- SKIN: microbes can not penetrate unbroken skin. Harmless bacteria live on your skin and use the oil from your pores to create acids that prevent other bacteria and fungi from growing.
- ACID IN YOUR STOMACH: if pathogens enter your body as you eat, they usually are killed by your stomach acidic gastric juices.
- MUCUS IN YOUR AIRWAYS: the cells of the membranes that line your trachea and bronchi produce a sticky mucus. It traps pathogens you breathe in. Microscopic hairs transport these trapped particles back out you mouth when they are coughed out or swallowed and destroyed.
- STERILE, ACIDIC URINE: urine constantly flushes the bladder, ureters and urethra. Because urine is acidic, microbes cannot readily grow.
- WHITE BLOOD CELLS: your body produces white blood cells called phagocytes that consume and destroy microbes that enter the bloodstream.
- ANTIBODIES: these are proteins produced by the body that attach themselves to pathogens or foreign substances and allow the phagocytes to destroy them.
- IMMUNITY: when the body has experience a disease and fought it off successfully, they often become immune to it. That means that now that your defence system has killed the invading pathogen, they now have ready antibodies to fight it off again if necessary.

• Antibiotics: Antibiotics are a form of medicine that kills many disease organisms. Antibiotic drugs have saved many lives. Unfortunately, some microbes have become resistant to their effects. Antibiotics can not cure viral diseases.


• Hygiene: Hygiene is a very effective way to resist infection or disease. If your body is kept clean, then you make the risk of contracting a disease much lower.  By washing your hands regularly you can stop yourself from contracting many diseases which are transferred through your dirty hands.


• Immunization: an active process that seeks to protect you before you are attacked by certain microbes. Scientists have developed vaccines from dead or ineffective microbes. If these vaccines are injected into your blood, you develop immunity to that disease. Active immunizations have been developed for bacterial and viral infections.


• Non-Infectious Diseases: not all diseases are caused by microbes. Non- infectious diseases include genetic diseases (e.g. Down syndrome), nutritional diseases (e.g. anorexia), environmental diseases (e.g. lead poisoning) and organ and tissue diseases (e.g. cancer, heart disease). Some environmental diseases are caused by factors in the environment, such as heavy lead poisoning and radiation.


• Cancer: cancer is caused by abnormal cell division, which creates abnormal cells which don’t function properly. The defence system usually removes these cells, but if it can’t the cells continue to divide forming a mass of cells called a tumour or cancer. There are two types of tumours, benign and malignant. Benign tumours grow within a membrane, but malignant do not and often invade other tissues and organs. Cancer is caused by cells being exposed to an agent called a carcinogen. This causes the genetic code in the chromosomes to change (mutation). This leads to their abnormal behaviour. Some common carcinogens include tobacco smoke, benzene, hep. B virus, HIV, x-rays and Gamma rays.


• SKIN CANCER- Caused by exposure to UV rays, which are invisible.

Topic 7 – Multiplication

• Life Cycle: the cycle of a certain organisms life, including birth, growth, reproduction and death.


• Fertilization: the combination of the sperm and the egg to create a new living cell.


• Sexual Reproduction: involves the production of specialized sex cells called gametes. The male gamete (sperm) must meet the female gamete (egg) at FERTALIZATION to produce the first new call of the next generation. Examples of sexually reproducing organisms include humans, mammals, lizards, frogs, fish and some flowers. Many organisms sexually reproduce differently. For example, fish and frogs reproduce EXTERNALLY, where the female eggs and the male sperm meet and unite in the water. Mammals reproduce INTERNALLY, yet monotreme mammals such as the platypus lay eggs which are held in a skin fold till the young is ready to be born. Marsupials are born at an immature stage of their development and are held in a pouch until they have fully grown. Placental animals, such as cows and horses and humans, give birth to their live young at a late stage in development.


• Asexual Reproduction: asexual reproduction is the reproduction of an organism without the help of another organism. Many simple protests and bacteria reproduce asexually by making IDENTICAL copies of their cell through normal cell division. Examples include bacteria, protozoa, fungi, and many types of plants.

Fission: simple cell division to produce identical cells that are approx. the same size. Some yeasts or hydra reproduce this way yet the new cells are smaller and called BUDS.
Spores: produced by field mushrooms, moulds etc., they are grown in spore sacs and opened to spread around.
Vegetative Reproduction: RUNNERS: new stems that grow along the soil surface and produce new shoots e.g. strawberries. BULBS: onion and daffodil bulbs produce buds that develop into new plants. TUBBERS: potatoes are swollen stems called tubers that grow vegetatively underground.  RHIZOMES: underground branching stems. E.g. couch grass, irises. CUTTINGS: a small part of a plant which is cut off and replanted. Roots grow from where it was cut. E.g. roses, apple trees.

• Organisms that reproduce both sexually and asexually: some organisms can reproduce both sexually and asexually, such as onions, potatoes, roses, grass, hydra, irises and daffodils. Often plants reproduce asexually because it leads to a higher success rate but sexually reproduction is important because it can create new varieties, some of which could survive sudden changes in the environment.


• Pollination: Fertilization of plants using pollen. Pollination occurs when the pollen of a male plant (with the sperm in it) enters the stigma of a female flower and they unite in the ovary to create a new seed.


• Human Reproduction: Once an egg is release into the fallopian tube during OVULATION a woman is ready to be fertilized. When a man and a woman have sexual intercourse, the man ejaculates sperm in to the woman. It travels into the uterus and to the fallopian tubes and fertilizes the egg. The new zygote moves into the uterus and implants itself into the wall. It grows for approx. 9 months, and then is delivered live and developed from the woman’s uterus through the vagina.


• Menstruation: Menstruation occurs in the female only. It is the cycle which prepares the body for fertilization.  Firstly FSH stimulates the growth of an egg in the follicles within the ovary. After so many days, LH stimulates ovulation, where the egg is released from the follicle into the fallopian tube. LTH stimulates the growth of the corpus luteum. Once it is developed, it produces oestrogen which continues building up the lining of the uterus. The oestrogen also stops the production of FSH. Progesterone also stimulates the lining of the uterus to grow. However if the egg is not fertilized, the lining is shed and a new cycle begins.


• Puberty:

Males: Begins on at average 12-14 and lasts about 4 years. Hormones stimulate secondary sex characteristics to begin. These include: growth of hair (pubic, body, underarm, facial); enlargement of the testes and penis; increased muscle development; deepening of the voice; stimulations of the sweat and oil producing glands; sexual desire; growth spurt.
Females: Begins on average between 11 and 13 and lasts about 4 years. Hormones begin secondary sex characteristics which include: growth of pubic and underarm hair; growth of breast; change in bones, especially the widening of the hips; redistribution of fat on the hips and thighs, the development of sexual desire; growth spurt; and the beginning of menstruation.