Eddie Playfair

Science in Society: what you need to know.

May 13, 2015 9:25 am

AS Science in Society (AQA)

A very condensed list of the key science concepts you need to understand well.

Infectious disease, medicines and the germ theory of disease:

All living things (organisms) are composed of cells. Most of the chemical reactions that are needed for organisms to stay alive, grow and reproduce take place in cells. The mechanisms are similar in the cells of all living organisms. Infectious diseases are caused by microbes suchas bacteria, fungi and viruses. How the body defends itself against infections or other foreign tissue with its immune system, the specific immune response and vaccination, exposing the individual to a form of the microbe that has been altered or attenuated so that it is unable to cause disease but will still stimulate the production of antibodies. The processis known as vaccination. Why it is difficult to develop an effective vaccine against some diseases such as the common cold, malaria and HIV. Drugs are chemicals derived from natural or synthetic sources that influence the normal chemical processes in the body. Antibiotics and antibiotic resistance. Cancers occur when cells divide uncontrollably. Mutations in certain genes damage the normal controls on cell division. The dividing cells form a tumour.

Genetics, reproductive choices and ethical issues in medicine:

Instructions for development are found in the form of genes which are part of the chromosomes in the nucleus of every cell in the organism. Each gene is a segment of a very long molecule of DNA. Chromosomes contain a large number of genes. All cells except sex cells, and red blood cells, contain two sets of chromosomes. Both chromosomes in a pair carry the same genes in the same place, but the two chromosomes may carry slightly different versions, called alleles. In sexual reproduction, a single specialised cell from a female merges with another specialised cell from a male. Each of these sex cells contains a randomly selected half of the parent’s genes. The single cell which they form then contains a full set of genetic information, one of each gene pair coming from a different parent. This process means that there is a very large number of possible combinations of the parents’ genes, so offspring can be quite varied in their characteristics. As a new organism grows from a single cell, its full set of genes is replicated in each cell. In any cell only a fraction of all the genes are expressed, that is, determine the functioning of the cell. The genes that are not expressed have no influence on the cell. Each cell contains two genes with the same function, and each gene may occur in two or more different versions called alleles. The way one allele affects cell function may dominate the effects of other alleles. This allele is known as dominant, and the others as recessive alleles. The effects of recessive alleles are only seen if both chromosomes carry the recessive alleles.

Most characteristics are determined by an interaction between several genes as well as by the effect of the environment. The environment can influence gene expression. In addition to the variation which arises through sexual reproduction, change can occasionally happen to a gene itself. This is called mutation. It can be caused by certain chemicals, by ionising radiation (including ultraviolet rays, X-rays or gamma rays). If a mutated gene happens to be in a sex cell, copies of it can be handed on to an offspring, perhaps giving it new characteristics. These may be undesirable or beneficial, or have no effect on the offspring’s ability to survive and reproduce.

Most cells in large organisms are specialised and carry out particular functions. The processes by which this specialisation occurs in the early development of an organism are very complex and are still not fully understood. Once they have become specialised, cells of animals stay specialised so that it is not easy to produce clones. Stem cells are cells that have not specialised. Embryonic stem cells can give rise to any type of specialised cell under the right conditions. Adult stem cells have developed partial specialisation and can only give rise to a limited number of new types of cell. Cloning is a way of making a genetically identical copy of an organism. Because all organisms use the same genetic code to carry units of information, a gene can be taken from the nucleus of one cell and placed in a different cell. This is called genetic modification. The resulting organism will display new characteristics.

Evolution:

The first living organisms are thought to have developed from molecules that could copy themselves. All the Earth’s present species, and the many more species that are now extinct, evolved from the same very simple life forms that first appeared on Earth about 3.5 billion years ago. All species can therefore be linked in a single branching tree structure in which many of the branches are ‘dead ends’. One of the mechanisms central to the explanation of evolution is natural selection. There is usually variation between individuals of the same species. Some have characteristics which give them a better chance of surviving and reproducing in a particular environment. These individuals will pass on their characteristics to the next generation. The genes for the advantageous characteristics will become more common as a result. Natural selection leads, over many generations, to a gradual change in the characteristics of a whole population.

Among the implications of this theory (Darwin’s theory of evolution) are that the process is not driven by any overall direction or aim; and that the path which evolution has actually taken is a result of chance factors at every stage and could, with minor changes in circumstances, have been different. In any given environment, or ecosystem, there is competition between several species for the materials they require to live and reproduce. Species may also be dependent on other species in the ecosystem. As a result of these complex patterns of interdependence and competition for resources, changes which affect one species can have extensive knock-on effects on other species.

Transport:

Atomic structure, elements, bonding, compounds and mixtures. Chemical reactions involve the recombination of atoms to form new and different substances. All changes require a fuel, or some other concentrated source of energy, to make them happen. Fuels are concentrated sources of energy. There is a finite amount of fossil fuel (coal, oil, natural gas) on Earth. Other energy sources (wind, wave, biomass such as wood) are renewable and can be replaced in the same sort of time scale as they are used. Energy can be transferred from one object to another mechanically (by forces acting), thermally (by heat flowing from high to low temperatures), electrically (by an electric current), or by radiation. A system of chemicals (for example, a fuel plus oxygen) can release energy when the chemicals react. When a change happens energy is not destroyed. Instead it is dispersed and ends up in a wider number of places. As a result it is less useful for driving any further changes. The principle of conservation of energy, energy efficiency (the percentage of the energy originally available which ends up where you want it to be). In many processes, energy is wasted and ends up heating parts of the system.

Radiation:

Although all atoms of an element have the same number of protons and electrons they may have different numbers of neutrons. Atoms of the same element with different numbers of neutrons are called isotopes. Most atoms are stable but some of these isotopes have unstable atoms. A substance containing unstable atoms is said to be radioactive. Radioactive atoms decay, emitting radiation. The decays occur randomly but with a definite probability. As they proceed, the number of radioactive atoms left in a sample falls, so the rate of emission drops. The number of emissions per second is called the activity of the source (in becquerel). The time which it takes for the activity of a sample of radioactive isotope to fall from any initial value to half of that value can be measured and is called the half-life of the radioactive isotope. The half-life is characteristic of the isotope.

Radioactive materials emit three types of radiation. Alpha particles are easily absorbed e.g. by a thin layer of paper, or a few centimetres of air. Beta emissions (a stream of electtrons) pass fairly easily through many substances but can be absorbed by a thin sheet of any metal. Gamma radiation (part of the electromagnetic spectrum) are very penetrating and can only be significantly reduced in strength by a thick sheet of a dense metal such as lead or by concrete several metres thick. When radiation is absorbed it ceases to exist as radiation, instead causing heating. Shorter wavelength radiation, ultraviolet, X-rays and gamma rays, can bring about chemical changes by breaking up molecules into fragments. The fragments are often electrically charged particles which we call ions. Radiation that produces ions is called ionising radiation. All three types of emission can cause damage to the molecules in living cells, either killing the cells or causing mutations in the genes. Alpha does most damage (per centimetre of their path), followed by beta, then gamma. The radiation dose equivalent (in sieverts) which a person receives is a measure of the amount of damage caused by the radiation within their body. Effects of radioactivity can be spread in two ways: by irradiation (the emissions from a radioactive substance striking and being absorbed by another object); and by contamination (the transfer of pieces of the radioactive substance itself on to, or into, another object).

The universe:

The solar system was formed about 5 billion years ago. The Sun is a star. Stars originate from clouds of gases drawn together by the force of gravity. In stars hydrogen atoms fuse to form helium atoms releasing energy until most of the hydrogen is used up – another 5 billion years for our Sun. The Sun is one of billions of stars clustered in a group called the Milky Way galaxy. The size of this galaxy is huge, even compared to the distances between our Sun and the nearest stars. Light travelling at 300 million metres per second takes about 100 000 years to get from one side of the galaxy to the other. Most of the galaxy is empty space. There are millions of other galaxies in the Universe. The distances between galaxies are very large compared to the size of the galaxies themselves. The distances between the galaxies are not fixed, but increasing. The Universe is expanding. The further apart galaxies are from each other, the faster they are moving apart. This suggests that all the universe, all of space, matter, energy and time started from a tiny size with a huge explosion (the Big Bang) which occurred 13.7 billion years ago. The rate at which the Universe is expanding seems to be increasing. We do not know what is causing this to happen and this unknown force is called as dark energy. Gravity is the force of attraction between any two masses, including planets, stars and other objects in the universe. The strength of the force is proportional to the masses of the two attracting objects and inversely proportional to the square of the distance between them.

Science in Society Quiz: 100 questions you should be able to answer

Don’t be satisfied with just finding the word, make sure you can explain the concept

A word which means the share of the total amount (a percentage, a fraction or a decimal)
A word which describes the amount of change as a share of the total amount
Diseases caused by microbes
Microbes which cause disease
Diseases which are caused by human behaviours
A very small micro-organism which needs to get into a cell in order to replicate
A substance which is recognised as non-self and triggers an immune response
A protein made by lymphocytes which binds with specific non-self molecules
When one variable changes in the same way as another variable
The relationship between two variables, when one rises, the other rises too
The relationship between two variables, when one variable rises and the other falls
A substance which destroys specific bacteria
When experiments can be repeated and show the same results
When it can be shown how one thing leads to something else
Gradual change over a long period
Sudden change over a short period
The study of development before birth
The study of fossils
The study of the progress of disease
The study of rocks and changes in the Earth over time
Passing characteristics from one generation to the next
When two structures are basically the same thing in different contexts
Comparing two things which have some similarities
Being able to cope better with a particular environment
Having lots of differences within a population
The study of animals
The study of plants
Five-fingered
The man who came up with the theory of evolution by natural selection
An Italian scientist who supported a Sun-centred view of the universe
A Polish astronomer who supported a Sun-centred view of the universe
An ancient scientist who supported an Earth-centred view of the universe
Earth-centred view
Sun-centred view
An unproven proposition
An explanation which has been thoroughly tested and is generally accepted as accurate
‘Bottom-up’ reasoning which draws general conclusions from specific cases
‘Top-down’ reasoning which starts from general statement to make predictions
Universally recognised scientific belief system which shapes the work of scientists
A statement about what will happen in the future
A proposed explanation which still needs to be properly tested
The biological process by which energy is released from food
The biological process by which food is produced from carbon dioxide and water
The process of stimulating the production of antibodies in order to protect against disease
The Austrian doctor who promoted antiseptic practice
The French scientist who promoted the germ theory of disease
The overall death rate in young children
The average time people live for
The thing which spreads a disease
Energy producing substances which originate from very ancient living things
The fact that higher levels of certain gases in the atmosphere causes more heat to be retained
A sex cell
A word which means that sex cells have only half the genetic material of body cells
Cell division which produces more body cells
Cell division which produces sex cells
The first cell or ‘fertilised egg’ which can then divide and grow into a full organism
Different genes for the same characteristic
The version of a gene which will be expressed even if it’s the only one present
The version of a gene which will only be expressed if two copies are present
When both versions of a gene are the same for a particular individual
The structure in the cell nucleus on which genes are found
The chemical which genes are made of
The 4 different nucleotides
The molecules which are strung together to form proteins
How many base pairs are needed to code for one amino acid
Ways of producing energy which will not run out
The products of the combustion of a hydrocarbon
A medical treatment which has no active ingredient
A test where the patient does not know whether they are getting an active treatment
A test where neither the patient knows whether they are getting an active treatment
A group in a trial who are not receiving the active treatment
Two particles which are present in the nucleus of an atom
How many electrons can occupy the first and the second shells of an atom
A form of electromagnetic radiation which can kill cells
A form of electromagnetic radiation with a very long wavelength and low frequency
An instrument for measuring radiation
An instrument which uses radiation to ‘see’ inside our bodies
The colour of visible light with the longest wavelength
The colour of visible light with the highest frequency
The nucleus of a Helium atom
A stream of electrons
Different versions of an atom of the same element which have different atomic mass
A substance made of atoms of the same atomic number
A charged atom
The connection between atoms when they share electrons
The connection between atoms which one gives electrons to the other
The unit of energy
The unit of mass
The unit of frequency
The unit of radioactive decay
The unit of radioactive dose
The speed of light
The speed of sound in air
The distance which light travels in a year
The time it takes for the amount of radioactivity emitted by a substance to fall by 50%
When the frequency of a wave changes because the source is travels away from, or towards, us
Our Sun and the planets which orbit it
A massive cluster of stars – the one we are in is called the Milky Way
The American scientist who discovered that the universe is expanding
The event which we think started the universe as we know it

Eddie Playfair

Science in Society: what you need to know.

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