An excellent example of Cryptic colouration, camouflage and natural selection.
Sunday, 29 May 2016
Friday, 27 May 2016
Pathogens
Defending against infection
Pathogens are microorganisms - such as bacteria and viruses - that cause disease. Bacteria release toxins, and viruses damage our cells. White blood cells can ingest and destroy pathogens. They can produce antibodies to destroy pathogens, and antitoxins to neutralise toxins.
In vaccination pathogens are introduced into the body in a weakened form. The process causes the body to produce enough white blood cells to protect itself against the pathogens, while not getting diseased.
Antibiotics are effective against bacteria, but not against viruses. Some strains of bacteria are resistant to antibiotics.
Pathogens - bacteria
Pathogens are microorganisms that cause infectious disease. Bacteria and viruses are the main pathogens.
Bacteria
Bacteria are microscopic organisms. They come in many shapes and sizes, but even the largest are only 10 micrometres long - 10 millionths of a metre.
Bacteria are living cells and, in favourable conditions, can multiply rapidly. Once inside the body, they release poisons or toxins that make us feel ill. Diseases caused by bacteria include:
- food poisoning
- cholera
- typhoid
- whooping cough
- gonorrhoea - a sexually transmitted disease
Thursday, 26 May 2016
9L1 and 9M1 Homework
Draw a diagram showing the following.
The Heart and its chambers
Valves
Major blood vessels
Systemic and Pulmonary circulation
Body and lungs
Oxygenated and de-oxygenated blood.
Note. This is not a DRAWING its a diagram.
Due after half term.
The Heart and its chambers
Valves
Major blood vessels
Systemic and Pulmonary circulation
Body and lungs
Oxygenated and de-oxygenated blood.
Note. This is not a DRAWING its a diagram.
Due after half term.
10L2 Homework
Draw typical animal and plant cells with full labeling.
Produce a table that shows which components are common to both animal and plant cells and which are unique to each type.
1 week deadline (after half term).
Produce a table that shows which components are common to both animal and plant cells and which are unique to each type.
1 week deadline (after half term).
Wednesday, 25 May 2016
8L2, 8M2 and 8L3 Science Homework
Research and write about these pathogens.
Polio
Whooping cough
Meningitis
Diptheria
Mumps.
Present results as a poster or mind map.
Polio
Whooping cough
Meningitis
Diptheria
Mumps.
Present results as a poster or mind map.
Tuesday, 23 September 2014
Fossil fuels
Making crude oil useful
Crude oil is a mixture of hydrocarbons. These are separated into useful products, such as fuels, using a process called fractional distillation.
The demand for short hydrocarbon molecules is greater than their supply in crude oil, so a reaction called cracking is used. Cracking converts long alkane molecules into shorter alkanes and alkenes, which are more useful. The exploitation of oil can damage the environment - for example, through oil spills.
Fossil fuels
Crude oil, coal and gas are fossil fuels. They were formed over millions of years, from the remains of dead organisms,
- coal was formed from dead plant material
- crude oil and gas were formed from dead marine organisms.
Fossil fuels are non-renewable. They took a very long time to form and we are using them up faster than they can be renewed. Fossil fuels are also finite resources. They are no longer being made or are being made extremely slowly. Once they have all been used up, they cannot be replaced.
How crude oil was formed (background information only)
Crude oil is found trapped in some of the sedimentary rocks of the Earth's crust.
Millions of years ago, huge numbers of microscopic animals and plants - plankton - died and fell to the bottom of the sea. Their remains were covered by mud.
As the mud sediment was buried by more sediment, it started to change into rock as the temperature and pressure increased. The plant and animal remains were ‘cooked’ by this process, and slowly changed into crude oil.
Oil is less dense than the water in the rocks and will rise as a result of pressure from below (as can be seen in the animation above). often the oil will escape altogether if the rocks are permeable (liquids can pass through them).
If some of the rocks above the oil are impermeable the oil cannot rise through them, so it gets trapped underneath.
Problems of exploiting oil
Geologists can often tell where oil is trapped by looking at the structure of the rocks. Oil tends to be trapped where rocks are domed upwards, or where permeable rocks are in contact with impermeable rocks at a fault line.
Drilling for oil
Oil companies can drill down through the impermeable rocks to get it out. They are then able to turn the oil into products that we can use.
Crude oil takes millions of years to form, and we are using it up more quickly than it is created. Present estimates suggest world supplies of crude oil will run out in about 30 years, unless we use it more efficiently. There are additional reserves of oil in rocks called oil shale. However, it is expensive to extract oil from oil shale because it needs to be heated to release it.
Environmental problems
Oil is carried from oil fields to refineries using ocean-going tankers. If it is spilled, it causes considerable damage to the environment:
- oil slicks travel across the sea, far from the original spill
- beaches and wildlife are harmed when they are coated with oil.
The oil damages feathers and birds may die. Detergents are often used to help clean up oil slicks, but these in turn may harm wildlife.
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Distillation
Distillation is a process that can be used to separate a pure liquid from a mixture of liquids. It works when the liquids have different boiling points. Distillation is commonly used to separate ethanol (the alcohol in alcoholic drinks) from water.
The mixture is heated in a flask. Ethanol has a lower boiling point than water so it evaporates first. The ethanol vapour is then cooled and condensed inside the condenser to form a pure liquid.
The thermometer shows the boiling point of the pure ethanol liquid. When all the ethanol has evaporated from the solution, the temperature rises and the water evaporates.
This is the sequence of events in distillation:
heating → evaporating → cooling → condensing
Fractional distillation
Hydrocarbons have different boiling points. They can be solid, liquid or gas at room temperature,
- small hydrocarbons with only a few carbon atoms have low boiling points and are gases
- hydrocarbons with between five and 12 carbon atoms are usually liquids
- large hydrocarbons with many carbon atoms have high boiling points and are solids.
Because they have different boiling points, the substances in crude oil can be separated using fractional distillation.
The fractionating column
Fractional distillation is different from distillation in that it separates a mixture into a number of different parts, called fractions. A tall column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top.
The crude oil is evaporated and its vapours condense at different temperatures in the fractionating column. Each fraction contains hydrocarbon molecules with a similar number of carbon atoms.
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