Biology Unit 10: Energy Flows in Ecosystems

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Unit 10 Energy Flows in Ecosystems

1. State that the Sun is the principal source of energy input to biological systems.

2. Define the terms: 

• food chain as a chart showing the flow of energy (food) from one organism to the next beginning with a producer (e.g. mahogany tree → caterpillar → song bird → hawk), 

• food web as a network of interconnected food chains showing the energy flow through part of an ecosystem, 

• producer as an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis, 

• consumer as an organism that gets its energy by feeding on other organisms, 

• herbivore as an animal that gets its energy by eating plants, 

• carnivore as an animal that gets its energy by eating other animals.

3. Describe energy losses between trophic levels.

As you go up a trophic level, energy is lost. For example, we have this chain:

mahogany tree → caterpillar → song bird → hawk

The mahogany tree gets the biggest amount of energy from the Sun. When the chain reaches the hawk, the hawk gets a very small amount of energy from the song bird. This is because energy is lost throughout the chain due to heat loss. Only about 10% of energy gets passed on to the next species in the chain. 

4. Define the terms: 

• decomposer as an organism that gets its energy from dead or waste organic matter, 

• ecosystem as a unit containing all of the organisms and their environment, interacting together, in a given area, e.g. decomposing log or a lake, 

• trophic level as the position of an organism in a food chain or food web.

5. Explain why food chains usually have fewer than five trophic levels.

As said above, only 10% of energy gets passed on from each species in the chain. If the chain were to continue, eventually there would be no energy to pass on. This is why food chains have a limit of around five trophic levels.

6. Describe the carbon cycle.

The carbon cycle is the cycle of which carbon travels around the Earth's atmosphere.

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7. Discuss the effects of the combustion of fossil fuels and the cutting down of forests on the oxygen and carbon dioxide concentrations in the atmosphere.

Combustion of fuels results in carbon dioxide and nitrous oxides being released into the atmosphere. These contribute to overall global warming. Deforestation increases the amount of carbon dioxide in the atmosphere; this is because there are no more trees to use carbon dioxide for photosynthesis. 

Biology Unit 11: Human Influences on the Ecosystem

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Unit 11 Human Influences on the Ecosystem

1. List the undesirable effects of deforestation (to include extinction, loss of soil, flooding, carbon dioxide build up).

• Trees serve has habitats for animals; if they are cut down animals lose their homes and become more vulnerable to predators. The species will die out because they don't have a place to live

• Without trees, land is vulnerable to weather conditions that cause erosion

• Flooding will become easier because the land has no barriers that stop the water

• Trees use carbon dioxide in photosynthesis, and without trees the carbon dioxide levels in the atmosphere will rise

2. Describe the undesirable effects of overuse of fertilisers (to include eutrophication of lakes and rivers).

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3. Describe the undesirable effects of pollution to include: 

• water pollution by sewage and chemical waste, 

• air pollution by greenhouse gases (carbon dioxide and methane) contributing to global warming.

If chemical waste and rubbish flow into our seas, this basically makes the water unclean and makes it difficult for aquatic life to survive.

Carbon dioxide and methane are both greenhouse gases; greenhouse gases are the gases that absorb heat and reflect it back into the atmosphere, causing the world temperature to increase. This is bad for the environment as heat will cause ice at the Poles to melt, raising average sea levels.

4. Discuss the causes and effects on the environment of acid rain, and the measures that might be taken to reduce its incidence.

When sulphur dioxide and nitrogen oxides are released into the atmosphere, they mix with oxygen, water, and other chemicals. This causes acid rain. 

To reduce buildup that leads to acid rain, the burning of fossil fuels should be reduced. This is because combusting fossil fuels release both sulphur dioxide and nitric oxides. 

5. Explain how increases in greenhouse gases (carbon dioxide and methane) are thought to cause global warming.

This is similar to second point of point 3.

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6. Describe the need for conservation of: 

• species and their habitats, 

• natural resources (limited to water and non-renewable materials including fossil fuels).

Species need to me conserved because all specie are part of the food chain. If the food chain is disrupted, all species of the food chain will be affected, including humans. Their habitats must also be conserved to ensure they are able to survive.

Natural resources must be conserved because the Earth has only a limited amount. If all resources were to be used up, there would be none left for future generations. While fossil fuels can be produced again, it would take millions of years, and humanity doesn't have that much time to wait!

Chemistry Unit 1: The Particle Nature of Matter

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Unit 1 The Particle Nature of Matter

1. Demonstrate understanding of the terms atom and molecule.

An atom is a particle that makes up an element. It consists of a nucleus - containing protons and neutrons - and electrons.

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A molecule is also a particle that makes up an element. Atoms make up molecules, so their definitions are similar. 

For example, this water molecule consists of two hydrogen atoms and one oxygen atoms. 

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Biology Unit 4.1: Nutrients

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Unit 4.1 Nutrients

1. List the chemical elements that make up:
• carbohydrates,
• fats,
• proteins.

Carbohydrates: starch, glucose
Fats: glycerol and fatty acids
Proteins: long chains of amino acids

2. Define nutrition as taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them.

3. Describe the structure of large molecules made from smaller basic units, i.e.
• simple sugars to starch and glycogen,
• amino acids to proteins,
• fatty acids and glycerol to fats and oils.

This is basically point 1, but it goes into a bit more detail on structure.

4. Describe tests for:
• starch (iodine solution),
• reducing sugars (Benedict’s solution),
• protein (biuret test),
• fats (ethanol).

Iodine: tests for starch, blue-black if present, brown if not
Benedict's solution: tests for glucose, brick red if present, blue if not
Biuret test: tests for protein, purple if present, blue if not
Ethanol: tests for fats, will emulsify if present, won't if not

5. List the principal sources of, and describe the importance of:
• carbohydrates,
• fats,
• proteins,
• vitamins (C and D only),
• mineral salts (calcium and iron only),
• fibre (roughage),
• water.

Carbohydrates provide our bodies with energy. They can be found in food products such as rice, noodles, bread and potatoes. Fats also provide our bodies with energy, and they help our bodies absorb a multitude of vitamins. They can be found in plants and fish, such as lentil beans and salmon. Proteins come from meat, fish and eggs; they help our bodies with processes of growth and repair.

Vitamin C can be found in citrus fruits and is used for maintaining healthy skin and absorbing iron. A vitamin C deficiency is called scurvy. Vitamin D comes from oily fish, and it helps to absorb calcium and maintain strong bones. A deficiency in vitamin D is rickets.

Calcium comes from milk, and it helps maintain the strength and health of bones. A person would have weak bones without the intake of calcium. Iron can be found in red meats, and is used to produce haemoglobin. Anaemia is a vitamin D deficiency.

Fibre is used to prevent constipation, by adding bulk to faeces. It can be found in wholegrain foods, fruits and vegetables, and nuts.

Water makes up 70% of the human body. It has many important roles, such as transporting nutrients around the body and regulating body temperature. If a person doesn't intake enough water, they will become dehydrated.

6. Describe the use of microorganisms in the manufacture of yoghurt.

1. Milk is heated to be pasteurised
2. After the milk has cooled, bacteria called Lactobacillus bacteria is added. This breaks down lactose in milk to form lactic acid.
Lactic acid lowers the pH of the yoghurt so it doesn't go off, and denatures milk proteins, which gives yoghurt its sharp taste.

7. Describe the deficiency symptoms for:
• vitamins (C and D only),
• mineral salts (calcium and iron only).

Refer to point 5!

Chemistry Unit 11: Air and Water

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Unit 11 Air and Water

1. Describe a chemical test for water.

There are two ways in which you can go about. The first is using anhydrous copper sulphate; in the presence of water, the anhydrous copper sulphate turns from white to blue. Alternatively, you could use anhydrous cobalt chloride; in the presence of water, the anhydrous cobalt chloride turns from blue to pink. 

2. Describe and explain, in outline, the purification of the water supply by filtration and chlorination.

Filtration is used to separate insoluble substances from the water. Afterwards, the water is chlorinated to get rid of bacteria that couldn't be removed through filtration.

3. State some of the uses of water in industry and in the home.

Home: cooking, cleaning, washing

Industry: cooling, planting in agriculture

4. Describe the separation of oxygen and nitrogen from liquid air by fractional distillation.

Like crude oil, liquid air can be separated in a fractionating column. Liquid air is pumped into the bottom of the column and it is heated. Nitrogen gas evaporates from the air and is collected at the top of the column, while liquid oxygen is collected from the bottom. 

5. Describe the composition of clean air as being a mixture of 78% nitrogen, 21% oxygen and small quantities of noble gases, water vapour and carbon dioxide. 

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6. State the common air pollutants as carbon monoxide, sulphur dioxide and oxides of nitrogen, and describe their sources.

Carbon monoxide, sulphur dioxide and nitrogen oxides are what make air dirty. Carbon monoxide comes from the incomplete burning of fuels, so any machinery that burns a fuel could release carbon monoxide. Additionally, burning cigarettes also produce carbon monoxide. Sulphur dioxide and nitrogen oxides both come from burning fossil fuels.

7. Explain the presence of oxides of nitrogen in car exhausts and their catalytic removal.

Oxides of nitrogen are formed in car engines due to heat and pressure. They are poisonous and harmful to humans, so catalytic converters are put into engines. Nitrogen oxide is reduced, meaning that it loses oxygen, so it breaks down into separate nitrogen and oxygen gases. In addition, carbon monoxide is oxidised, meaning it gains oxygen, so it becomes carbon dioxide. 

8. Explain why the proportion of carbon dioxide in the atmosphere is increasing, and why this is important.

Carbon dioxide levels are rising due to excessive human activity, such as factory production and deforestation. This is important because CO2 is one of the gases that contribute to the greenhouse effect, therefore resulting in global warming. Global warming is the general increase of temperature, and this has a great effect on our environment. 

9. State the adverse effect of common air pollutants on buildings and on health.

Air pollutants affect the materials used to build buildings; they cause the materials to become discoloured, brittle, and prone to deterioration. Pollutants also have negative effects on health, including eye, throat and nose irritation, breathing problems, and cancer. 

10. Describe the formation of carbon dioxide: 

• as a product of complete combustion of carbon-containing substances, 

• as a product of respiration, 

• as a product of the reaction between an acid and a carbonate, 

• as a product of thermal decomposition.

When anything containing carbon burns, the carbon reacts with oxygen, gets oxidised, and becomes carbon dioxide. Carbon dioxide is a product of respiration, from the equation glucose + oxygen --> carbon dioxide and water. Similarly, when an acid and carbonate react together, a product of the reaction is carbon dioxide (the other is water). Carbon dioxide is also produced from thermal decomposition. Take the decomposition of calcium carbonate for instance: when calcium carbonate is heated, it breaks down into calcium oxide and carbon dioxide. 

11. Describe the essential conditions for the manufacture of ammonia by the Haber process including the sources of the hydrogen and nitrogen, i.e. hydrocarbons or steam and air.

The Haber process is a process that manufacture ammonia. Nitrogen from the atmosphere and hydrogen, formed through the reacted of methane and steam, are reacted together to form ammonia; this is a reversible reaction.

nitrogen + hydrogen <--> ammonia

N + 3H <--> NH3

The amount of ammonia produced at a time is quite low - about 15%. To produce a higher yield, the following conditions are needed:

• low temperature

• high pressure

• catalyst of iron to speed up the reaction 

This is an important process because ammonia is used in the manufacture of fertilisers used in agriculture. Fertilisers speed up the growth of plants and gives them additional nutrients, so that they grow quickly and healthily. 

12. Describe the rusting of iron in terms of a reaction involving air and water, and simple methods of rust prevention, including paint and other coatings to exclude oxygen.

Iron rusts when it comes into contact with both air and water. Water reacts with the iron over time and the oxygen in the air oxidises the iron. Combined, this forms a layer of rust. 

There are several ways to prevent rust from forming. One would be to simply use a coat of paint; this acts as a barrier to prevent contact with water and air. Another way would be to galvanise the iron, which is to coat the iron in zinc. Similar to paint, the zinc acts as a barrier. Lastly, sacrificial protection can be used. A block of zinc is placed next to the iron, so that any water and air present reacts with the zinc, rather than the iron. 

13. Describe the need for nitrogen-, phosphorus- and potassium-containing fertilisers.

Plants need nitrogen, phosphorus and potassium to grow healthily. Nitrogen helps with the production of proteins, which is a plant's food. Phosphorus helps balance out the pH of the soil, and potassium helps with the production of chloroplasts, which help the plant photosynthesise. 

14. Describe the displacement of ammonia from its salts by warming with an alkali.

When an ammonium salt is warmed with an alkali, the ammonia in the salt is displaced by ammonia gas.

Physics Unit 2.1: Mass and Weight

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Unit 2.1 Mass and Weight

1. Be able to distinguish between the mass and weight of an object.

Mass = the amount of substance in an object; measured in g/kg

Weight = a force due to gravity; measured in Newtons N

2. Demonstrate understanding that mass is a property that ‘resists’ change in motion.

If a force is applied to an object, it does not immediately reach a high speed as it takes time for it to accelerate. If the force is constant, there won't be constant acceleration. If the force is not constant, there will be a moment of acceleration, allowing the object to accelerate. 

For example, you hit a ball. You are the force that moves the ball, and it takes time for the ball to accelerate in the air. If you keep contact with the ball, it stays at a constant speed and will not move faster. If you hit it and lose contact, the ball will fly up into the air and accelerate. 

3. Know that the Earth is the source of a gravitational field. 

Anything with a mass will be pulled down to Earth by the force of weight. If the object has a big mass, a bigger force will be applied to it.

4. Describe, and use the concept of, weight as the effect of a gravitational field on a mass.

In comes the equation for weight:

weight = mass x gravity

N = g x m/s^2

Chemistry Unit 7.1: Speed of Reaction

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Unit 7.1 Speed of Reaction

1. Describe the effect of concentration, particle size, catalysis and temperature on the speeds of reactions.

Here are some factors that speed up the rate of a reaction:

• surface area: the larger the surface area, the faster the rate; this is because this increases the chance of particles colliding with each other
• concentration: a higher concentration means there are more particles in each cm^3 of space, so there are more collisions
• catalysis: a catalyst speeds up the rate of a reaction; it lowers the amount of energy needed for the reaction to take place, so it occurs more easily
• temperature: a higher temperature provides energy for articles to move more quickly, so they collide more often

2. Describe a practical method for investigating the speed of a reaction involving gas evolution.

An example to investigate this is using magnesium and hydrochloric acid to test the rate of reaction. The equation goes as follows:

magnesium + hydrochloric acid --> magnesium chloride + hydrogen

Equipment:

• conical flask

• gas syringe

• stopwatch

• hydrochloric acid

• magnesium

Using this apparatus, we can design an experiment that, for example, measures how long it takes for 20cm^3 of gas, using the volume of magnesium as our independent variable (the one you change). 

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The diagram above uses magnesium ribbons instead of powder, but that's completely fine.

3. Devise a suitable method for investigating the effect of a given variable on the speed of a reaction.

For the experiment above, time was the variable that we changed. The experiment could also be designed around other variables:

• the concentration of acid

• temperature conditions

• surface area of magnesium (chips? ribbon? powder?)

• the reaction with a catalyst and without

4. Interpret data obtained from experiments concerned with speed of reaction.

Once you have carried out the experiment and obtained data, you'll be able to come to a conclusion on what you were investigating.

5. Describe the application of the above factors to the danger of explosive combustion with fine powders (e.g. flour mills) and gases (e.g. mines).

So you know that variables affecting the rate of a reaction are temperature, concentration, and surface area. These are applicable to real life situations.

In a flour mill, flour is produced. Flour particles are very small, so they have a large surface area. If there is a lot of flour in the air, a small spark can cause an explosion between flour and oxygen.

In a coal mine, the air is filled with flammable gases. If the gases reach a certain concentration they can form an explosion with air. 

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6. Describe and explain the effects of temperature and concentration in terms of collisions between reacting particles (concept of activation energy will not be examined).

As mentioned above, a higher temperature will give particles more energy to move and collide, and a higher concentration means there are more particles in the space that will collide. 

As a reaction occurs and the reactants get used up, the concentration of the substance decreases; this is why reactions slow down as they happen over a span of time.

7. Define catalyst as an agent which increases rate but which remains unchanged.

A catalyst is a substance thats speeds up a reaction, but the catalyst itself will not be used up.

Biology Unit 5.2: Transport In Humans

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Unit 5.2 Transport In Humans

1. Describe the circulatory system as a system of tubes with a pump and valves to ensure one-way flow of blood.

The circulatory system is the system in charge of blood in the human body. Blood travels through veins, capillaries and arteries and valves are put into place to ensure the blood flows one way.

2. Describe double circulation in terms of a low pressure circulation to the lungs and a high pressure circulation to the body tissues and relate these differences to the different functions of the two circuits.

Double circulation is comprised of two circuits: a circuit that links the heart and the lungs, and a circuit that links the heart and the rest of the body. Blood is pumped at a low pressure to the lungs because it only flows in one direction to one place (the lungs). Blood is pumped at a high pressure to the rest of the body because there are many different organs the blood must reach, and blood being pumped at high pressure will allow it to travel to those organs. 

3. Describe the structure of the heart including the muscular wall and septum, atria, ventricles, valves and associated blood vessels.

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The heart is split into two sides: the right and left. Blood always enters through the top half of the heart first. These are called atria (single = atrium). Deoxygenated blood from the body enters the heart through the right atrium and exits through the right ventricle. That blood travels to the lungs to pick up oxygen, entering the heart again through the left atrium. It exits out of the left ventricle and is pumped to reach organs in the body. The valves set in place are there to ensure the blood maintains its one-way flow.

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4. Describe coronary heart disease in terms of the blockage of coronary arteries and state the possible causes (diet, stress and smoking) and preventive measures. 

Coronary heart disease is the blockage of arteries by fatty deposits. This blocks blood flow, so organs, like the heart, can't get oxygen. All organs need oxygen to survive, so if the heart isn't getting oxygen it won't work properly. Causes of coronary heart disease include poor diet, smoking and stress.

To prevent this disease, you can change your diet to a healthier one, exercise regularly, and not smoke. 

5. Describe the function of the heart in terms of muscular contraction and the working of the valves.

Atria and ventricles have muscular walls that allow them to pump blood when the walls contract. The walls contract, squeezing the chambers and pushing the blood out of it; this is the mechanism of blood being pumped. The valves open and close to control where blood flows to. 

6. Investigate the effect of physical activity on pulse rate

When you do more physical activity, your heart beats faster. This is because your muscles need more oxygen to function, so the red blood cells in your blood must obtain more oxygen and supply it to the muscles. During this, arteries that supply blood to the muscles dilate. Blood flow increases, increasing the flow of glucose and oxygen; the rate of removal of carbon dioxide also increases.

7. Investigate, state and explain the effect of physical activity on pulse rate.

8. Name the main blood vessels to and from the heart, lungs, liver and kidney.

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The body contains arteries and vessels. Arteries have thick walls and thick layers of muscle and elastic fibres; this allows blood to be pumped at a higher pressure. Arteries pump blood away from the body and to the different organs.

Vessels have thinner walls and thinner layers of muscle and elastic fibres. The blood being pumped through vessels is at a lesser pressure. Vessels pump blood towards the lungs. 

Organ	To	From
Heart	Vena cava	Aorta
Lungs	Pulmonary artery	Pulmonary vein
Liver	Hepatic artery	Hepatic vein
Kidney	Renal artery	Renal vein

9. Describe the structure and functions of arteries, veins and capillaries.

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I've mentioned arteries and veins, but what are capillaries? Capillaries are branches of the artery. Their walls are one cell thick, they're extremely narrow, and they reach body cells. Oxygen and glucose easily diffuse through the capillaries to cells, and carbon dioxide and other waste easily diffuse in to the capillaries. Arteries split into capillaries, and they join back up into veins. 

From the diagram you can see what makes up arteries, veins, and capillaries. The artery is noticeably less wide than the vein, as the narrowness allows the blood to be pumped at a high pressure.

10. Explain how structure and function are related in arteries, veins and capillaries.

Arteries are more elastic because when the ventricle contracts, blood flows through the arteries and is pumped at a high pressure to reach organs. They are deeper in the flesh than veins and the pulse from them is detectable. 

Veins are less elastic because the blood flowing in them doesn't need to be at a high pressure. They are near the surface of the skin because they can get rid of heat if the body becomes too hot (you'll learn more about this in the homeostasis unit). The pulse from veins is not detectable because blood is not pumped at a high pressure. 

Capillaries are thin, as mentioned above, so substances can easily diffuse in and out of them.

11. Identify red and white blood cells as seen under the light microscope on prepared slides, and in diagrams and photomicrographs.

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Blood is made up of these three things: red blood cells, white blood cells, and platelets.

Red blood cells transport oxygen and carbon dioxide around the body. They are red because of a pigment called haemoglobin. Oxygen binds to haemoglobin after it is picked up from the lungs. Red blood cells are disk-like. They contain no nuclei to maximise the storage of oxygen.

White blood cells protect the body against diseases and viruses. There are two types of white blood cells: lymphocytes and phagocytes. When a pathogen (virus) enters the body, lymphocytes produce chemicals that make them stick together, dissolve, or destroy the toxins pathogens produce, called antibodies. Phagocytes then engulf the pathogens; they are digested and then killed. 

Platelets are fragments of red blood cells that help blood clot. They are made in bone marrow, along with other blood cells. When you get a cut, platelets come in contact with air, turning a protein called fibrinogen into threads of fibrin. These threads make a net over the cut. Red blood cells get caught in the net, creating a blood clot. The clot dries to form a scab, and new skin grows underneath the scab. Without platelets, it would be easier for pathogens to get into the body.

12. List the components of blood as red blood cells, white blood cells, platelets and plasma.

Along with the cells, plasma makes up blood. Plasma is a liquid that carries dissolved substances around the body, such as nutrients, hormones, and waste materials. 

13. State the functions of blood: 

• red blood cells – haemoglobin and oxygen transport, 

• white blood cells – phagocytosis and antibody formation, 

• platelets – causing clotting (no details), 

• plasma – transport of blood cells, ions, soluble nutrients, hormones and carbon dioxide.

14. Describe the immune system in terms of antibody production, tissue rejection and phagocytosis.

Antibodies are produced by lymphocytes to help the body get rid of pathogens. 

Tissue rejection is when the body recognises that a foreign organ donor is not originally part of the body. The body then rejects the organ. 

Phagocytosis is the name for when phagocytes engulf pathogens, destroying them to keep the body healthy. 

Chemistry Unit 9: The Periodic Table

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As reference, here is a Periodic Table; you can refer to this as you go along the syllabus statements. If you didn't know already, you will be provided with a Periodic Table when you take you exams!

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1. Describe the way the Periodic Table classifies elements in order of proton number.

Elements are ordered in numerical order according to the number of protons it contains. Hydrogen has one proton so it is first, followed by helium, lithium, etc.

2. Use the Periodic Table to predict properties of elements by means of groups and periods.

On the Periodic Table there are groups. The important ones that the syllabus covers are alkali metals (group 1), transition metals (group 3), halogens (group 7) and noble gases (group 0/8).




Unit 9.1 Periodic Trends

1. Describe the change from metallic to non-metallic character across a period.

As you run across the Periodic Table horizontally, the character of the element goes from metallic to non-metallic.

2. Describe the relationship between Group number, number of outer-shell (valency) electrons and metallic /non-metallic character.

The valency of the outer shell depends on what group the element is in. Here's a little advice: once you get your Periodic Table in the exam, start from Group 1 and label +1, +2, +3, +4, -3, -2, -1, full, ending on Group 8. This determines the valency of the element, helping you to balance equations.




Unit 9.2 Group Properties

1. Describe lithium, sodium and potassium in Group I as a collection of relatively soft metals showing a trend in melting point and reaction with water.

Metal	Hardness	Reactivity	Melting point	Reaction with water
Lithium	Soft	Reactive	180.5°c	Fizzes on water, releases hydrogen
Sodium	Softer	More reactive	97.7°c	Fizzes on water, burns with a yellow flame, release hydrogen
Potassium	Softest	Most reactive	63.4°c	Fizzes on water, burns with a lilac flame, release hydrogen

From my experience, exam boards like to throw in a question worth 6-9 marks about lithium, sodium and potassium comparisons, so it's worth remembering these points.

2. Predict the properties of other elements in Group I, given data where appropriate.

Properties of alkali metals
• relatively soft metals
• low boiling and melting points --> decrease as you go down the group
• reacts with water to form metal hydroxide + hydrogen
• reacts with oxygen to form metal oxide
• reactivity increases as you go down the group
• densities increase as you go down the group

3. Describe the trends in properties of chlorine, bromine and iodine in Group VII including colour, physical state and reactions with other halide ions.

Halogen	State at room temperature	Colour	Reaction with halide ions
Chlorine	Gas	Yellow-green	Oxidises bromine and below
Bromine	Liquid	Red-brown	Oxidises iodine and below
Iodine	Solid	Purple	Oxidises astatate and below

4. Predict the properties of other elements in Group VII, given data where appropriate.

Properties of halogens

• melting and boiling points increase as you go down the group

• reactivity decreases as you go down the group

• kills bacteria

• react with metals to form metal halides

Unit 9.3 Transition Elements

1. Describe the transition elements as a collection of metals having high densities, high melting points and forming coloured compounds, and which, as elements and compounds, often act as catalysts.

Properties of transition metals

• high densities

• high melting points

• forms coloured compounds

• can act as catalysts

Unit 9.4 Noble Gases

1. Describe the noble gases as being unreactive.

Noble gases are unreactive because their outer shells are full. This means that they are stable without having to gain or lose electrons. They are also described as inert. 

2. Describe the uses of the noble gases in providing an inert atmosphere, i.e. argon in lamps, helium for filling balloons.

Under normal conditions, noble gases are odourless, colourless and nonflammable. 

• argon is used in lightbulbs

• helium is used to inflate tires and balloons

• neon is used in neon lights because it glows when electricity is passed through it

• xenon is used in photocopying 

Biology Unit 4.3 Animal Nutrition

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Unit 4.3 Animal Nutrition

1. State what is meant by the term balanced diet and describe a balanced diet related to age, sex and activity of an individual.

A balanced diet is a diet that includes all the necessary nutrients needed for an individual to maintain their health. A balanced diet should include carbohydrates, fats, proteins, vitamins, minerals, fibre and water.

Typically, older individuals need more food than the young; males need more food than females; more active individuals need more food than less active individuals. Of course, this doesn't factor in lifestyles, activity and such, so this is not all set in stone. It depends on the individual.

2. Describe the effects of malnutrition in relation to starvation, coronary heart disease, constipation and obesity.

Malnutrition can mean the lack of food, resulting in starvation. It can also refer to the lack of important nutrients. If your diet contains too much fat, coronary heart disease and obesity could be a result. The lack of fibre will result in constipation, as the role of fibre is to help bowel movement.

3. Define ingestion as taking substances (e.g. food, drink) into the body through the mouth.

4. Define egestion as passing out of food that has not been digested, as faeces, through the anus.

5. Identify the main regions of the alimentary canal and associated organs including mouth, salivary glands, oesophagus, stomach, small intestine: duodenum and ileum, pancreas, liver, gall bladder, large intestine: colon and rectum, anus.

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6. Describe the functions of the regions of the alimentary canal listed above, in relation to ingestion, digestion, absorption, assimilation and egestion of food.

Mouth: where food enters the alimentary canal

Salivary glands: produce saliva containing amylase to help break down the food 

Oesophagus: a muscular tube where ingested food is led down to the stomach

Liver: produces bile to emulsify fats

Stomach: where part of digestion occurs; the muscles in the stomach break down the food

Gall bladder: where bile is stored

Pancreas: produces digestive enzymes to break down food

Small intestine (duodenum): where food is mixed with digestive enzymes and bile

Small intestine (ileum): where digested food is absorbed by the blood (assimilation)

Large intestine (colon): where water is absorbed

Large intestine (rectum): where faeces is stored

Anus: egested substances (i.e. faeces) are removed

7. Define digestion as the break-down of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes.

8. Identify the types of human teeth and describe their structure and functions.

Tooth type	Quantity	Role
Incisor	8	Biting and cutting
Canine	4	Piercing and cutting
Premolar	8	Crushing and chewing
Molar	12	Crushing and chewing

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9. State the causes of dental decay and describe the proper care of teeth.

Dental decay occurs when the hard enamel of the tooth is damaged. This happens when bacteria enters the mouth and converts sugars into acid. The acid essentially eats its way through the enamel and can enter the soft dentine inside the tooth.

To avoid dental decay, cut down on food and drink high in sugar content, consistently and properly brush your teeth, and use toothpaste with fluorine in it so plaque can be removed. 

10. State the significance of chemical digestion in the alimentary canal in producing small, soluble molecules that can be absorbed. 

Our bodies can't absorb food molecules if they are too big; they won't be able to pass through the walls of the villi. This is why the body produces bile and enzymes to chemically digest food, so the particles are small enough to be dissolved and assimilated. 

11. Outline the role of bile in emulsifying fats, to increase the surface area for the action of enzymes.

Lipase is the enzyme that breaks down fats, but it can't do so unless the fat is broken down into smaller portions. The role of bile is to break down fats, called emulsifying, so that it gives the lipase a bigger surface area to work on. 

12. State where, in the alimentary canal, amylase, protease and lipase enzymes are secreted.

Amylase: pancreas and salivary glands

Protease: stomach and pancreas

Lipase: pancreas

13. State the functions of a typical amylase, a protease and a lipase, listing the substrate and end-products. 

Enzyme	Substrate (what the enzyme works on)	End product(s)
Amylase	Starch	Glucose
Protease	Proteins	Long chains of amino acids
Lipase	Lipids (fats)	Glycerol and fatty acids

14. Define absorption as movement of digested food molecules through the wall of the intestine into the blood.

15. Describe the significance of villi in increasing the internal surface area of the small intestine.

If you consider the shape of villi, you will see that they are like small, skinny mountains. This increases the internal surface area of the small intestine, maximising assimilation of food molecules. 

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16. Identify the small intestine as the region for the absorption of digested food.

As briefly mentioned above, the small intestine is split into two: the duodenum and the ileum. The ileum (second half of the small intestine) is where digested food is absorbed.

17. Describe the structure of a villus, including the role of capillaries and lacteals. 

The walls of the villi are very thin so that molecules can be absorbed easily. Villi contain blood capillaries in them so that when the molecules diffuse through the walls, they go into the bloodstream. The concentration of food is lower in the blood so diffusion happens quickly. 

The lacteal is in between the blood capillaries. Its function is to transport glycerol and fatty acids away form the small intestine. 

18. Describe the role of the liver in the metabolism of glucose (glucose → glycogen).

This process is called glucoregulation. You will come across this again in the hormones unit, but here is what it is: when glucose levels in the body are too high, the pancreas secretes insulin, a hormone that regulates your body's glucose levels, into the bloodstream. This allows the liver to convert the glucose into glycogen, which is stored. When the glucose levels are too low, insulin will not be secreted, allowing the stored glycogen to break down into glucose that is then used by the body. 

19. Describe the role of fat as an energy storage substance.

Lipids are broken down into glycerol and fatty acids. The liver can convert glycerol into glucose for the body to use as energy.