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GCSE Biology Revision 2006-2007.

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Presentation on theme: "GCSE Biology Revision 2006-2007."— Presentation transcript:

1 GCSE Biology Revision

2 Life Processes Movement Respiration Sensitivity Growth Reproduction
Excretion Nutrition Mrs Gren – or –many naughty rabbits eat green rhubarb stems

3 Plant and Animal Cells (cellulose) mitochondria

4 Cell specialisation

5 Cell organisation system organism

6 Transport In and Out of Cells
Diffusion – from a high to a low concentration until they are evenly spread Osmosis – from a region of high water concentration to a region of low (weak to a strong solution) through a semi permeable membrane Active transport – from a low to a high concentration across a cell membrane

7 Digestion

8 Balanced Diets Carbohydrates Protein Lipids / Fats Vitamins Minerals
Fibre Water

9 The Duodenum Amylase Starch Maltose Protease Proteins and polypeptides
Amino acids Lipase Fats Fatty acids and Glycerol

10 The Ileum Maltase Maltose Glucose Sucrase Sucrose Glucose and Fructose
Lactase Lactose Glucose and Galactose Peptidase Polypeptides Amino acids Lipase Fat Fatty acids and Glycerol

11 Absorption and Assimilation
Glucose and amino acids are absorbed into the blood Fatty acids and glycerol are absorbed into the lacteal

12 Assimilation All digested glucose and amino acids pass into the liver in the Hepatic Portal Vein. Fats enter the lymphatic system which enters the blood and returns them to the liver. The food is used for growth, repair, respiration. Excess food is mostly stored as fat.

13 Food Testing Starch – add iodine – turns black
Glucose or reducing sugar – add Benedict's solution and boil – turns brick red Protein – Biuret test – add NaOH or KOH and then 1% copper sulphate – a violet colouration

14 Aerobic Respiration With oxygen C6H12O6 + 6O H2O + 6CO2 + energy

15 Anaerobic Respiration
Animals Glucose Lactic acid Plants Glucose Ethanol and carbon dioxide Oxygen debt – the amount of oxygen needed to breakdown the lactic acid accumulated

16 Structure of Thorax

17 The Thorax

18 Breathing in Is controlled by the intercostal muscles and the diaphragm. When we breathe in the intercostal muscles contract and the ribs move up and out. The diaphragm contracts and moves down. This increases the space inside the chest and air rushes into the lungs.

19 Breathing out The intercostal muscles and the diaphragm relax.
The ribcage drops down and the diaphragm moves upwards. This reduces the space inside the chest and pushes air out of the lungs.

20 Breathing Rate and Depth
Rate - how many breaths per minute Depth – how much air is being taken in, normally ½ litre per breath Measured with a spirometer

21 % of different gases in inhaled and exhaled air
Inhaled air (%) Exhaled air (%) Oxygen 20 16 Carbon dioxide 0.04 4 Nitrogen 79 Water vapour Variable level 100% saturated

22 Gaseous exchange

23 What makes the lung good at gaseous exchange?
Large surface area – greater volume of gases exchanged Good blood supply – O2 and CO2 exchanged more quickly Thin membranes – allows diffusion Moist lining – for the gases to dissolve

24 Keeping the Lungs Clean
Dust, bacteria and other particles stick to the mucus secreted by cells lining the airways Cilia attached to these cells waft the mucus and dirt out of the lungs and it is swallowed. Acid in the stomach kills the bacteria

25 Effects of Smoking Tar causes cancer Nicotine is addictive
Smoking removes the hairs that keep the lungs clean


27 light carbon dioxide+water glucose+oxygen chlorophyll
Photosynthesis light carbon dioxide+water glucose+oxygen chlorophyll 6H2O + 6CO C6H12O6 + 6O2

28 Leaf Structure

29 The leaf has a waxy cuticle to stop it losing water.
The epidermis is a protective layer of cells and contains no chloroplasts. The palisade layer contains the most chloroplasts as it is near the top of the leaf. The chloroplasts contain the pigment chlorophyll. It is here that photosynthesis takes place. The palisade cells are arranged upright. This means the light has to pass through the cell lengthways and so increases the amount of light absorbed.

30 Stomata Guard cells stoma
Water moves into the guard cells by osmosis and the stoma opens

31 Day During the daytime the rate of photosynthesis is greater than the rate of respiration

32 Night During both the day and night respiration occurs in plants.

33 Limiting Factors Photosynthesis is a chemical reaction, its rate depends upon temperature, how much CO2 is available, light intensity, amount of chlorophyll or water. Without enough light a plant cannot photosynthesise very fast, even if there is plenty of water and carbon dioxide. Increasing the light intensity will make photosynthesis faster.

34 Sometimes photosynthesis is limited by the level of carbon dioxide
Sometimes photosynthesis is limited by the level of carbon dioxide. Even if there is plenty of light a plant cannot photosynthesise if it has run out of carbon dioxide. Temperature can be a limiting factor too. If it gets too cold the rate of photosynthesis will slow right down; equally, plants cease to be able to photosynthesise if it gets too hot.

35 If you plot the rate of photosynthesis against the levels of these three limiting factors you get graphs like the ones below.

36 Maximising growth Understanding the factors that limit photosynthesis enables greenhouse farmers to maximise the conditions for plant growth. They often use paraffin lamps inside the greenhouse because burning paraffin produces carbon dioxide as well as heat, and so makes photosynthesis proceed faster. They may also use artificial light to enable photosynthesis to continue beyond daylight hours.

37 Uses of Glucose Turned into starch for storage
Converted into lipid/fat for storage – energy rich Nitrogen can be added and turned into protein Stored in fruit Used in respiration

38 Mineral Requirements Magnesium for chlorophyll Nitrogen for growth
Phosphorus for cell membranes and DNA Remember how to test leaves for starch

39 The Heart

40 The Heart Pumps blood around the body Pumps blood to the lungs
To pick up oxygen Remove carbon dioxide

41 Double Circulation Heart Lungs Body Greater pressure,
better oxygenation, faster flow

42 Arteries Veins and Capillaries
Thin walls, deoxygenated blood, to the heart, valves Thick walls, oxygenated blood, away from heart Link arteries to veins, site of exchange of metabolites and waste

43 Blood Red blood cells, transport oxygen, biconcave, no nucleus,
White blood cells, defence, engulf bacteria, produce antibodies

44 Platelets Used in the clotting of blood
Damage cause them to clump and they begin the conversion of soluble fibrinogen (blood protein) into insoluble fibrin which meshes over the wound and traps red cells. They dry and form a scab

45 Blood Cells

46 Tissue exchange Glucose Waste PLASMA

47 The lymphatic system Transports excess fluid from the tissues
Transports digested fat Contains white blood cells that fight infection

48 William Harvey 1578-1657 Observed blood flow around the body
Noticed existence of valves in veins Concluded blood pumped via veins round body Major medical breakthrough!

49 Galen Lived 1,000 years before Harvey
Did not use the scientific method Observation and experimentation Thought blood went from side to side Did not realise transport existed round body through capillaries

50 Transport in Plants

51 The Plant Transport System
A plant's transport system is made up of two types of tubes - strong, thick pipes called xylem vessels, and thinner tubes called phloem vessels. The cells of these vessels are modified to make them suited to performing their special functions                                                        Together xylem and phloem form the vascular tissue, often also referred to as the vascular bundle.

52 Xylem consists of dead cells with no end walls, which contain lignin to form stiff tubes. They are impermeable.

53 Phloem consists of living cells lined with cytoplasm, with walls made of cellulose and perforated end walls. They are permeable, and are surrounded by companion cells.

54                                                                    Water is taken up the plant from the roots to the leaves (for photosynthesis and transpiration) - in xylem vessels . Minerals dissolved in the water are taken up the plant to the shoots and leaves - in xylem vessels. Food (the product of photosynthesis) is taken from the leaves and moved up and down the plant to any part which needs it (for growth or for storage) - in phloem vessels.

55 Transpiration Temperature Humidity Air movement Light

56 Ecology – Competition and Adaptation
Keeping cool Keeping warm

57 Plant adaptations Not being eaten Reducing water loss

58 Predators, Prey and Co-operation
Snowshoe hare Arctic fox

59 Food Chains

60 Woodland Food Web

61 Pyramid of Numbers Remember not always pyramid shape

62 Pyramid of biomass fox rabbit grass
Biomass is dry weight – water has been removed

63 Decomposition Decomposers are bacteria and fungi
Organic matter- ammonium compounds-nitrite-nitrate

64 Plants and animals die and decay
The Carbon Cycle Plants and animals die and decay

65 Nitrogen Cycle

66 Food Production and farming methods
Monoculture Hedgerow removal Biological pest control Pesticides and herbicides and insecticides

67 Energy and Waste Burning fossil fuels such as coal, oil or gas
Greenhouse effect Sulphur dioxide and nitrous oxides are formed which dissolve in water to form acid rain Reduce the demand for energy so it reaches a sustainable level- will not use up the resources or pollute the planet

68 Global Warming and Acid Rain

69 Conservation To prevent habitats and organisms from disappearing
Limit or ban hunting. Gene banks of frozen eggs, sperm or embryos. Zoos and captive breeding programmes. Preserve habitats

70 The Nervous System Stimulus Response Receptor Effector Sensory Neuron
Motor neuron Central nervous system

71 Motor neuron

72 The Eye

73 Accommodation Long distance – lens long and thin, ciliary muscle relaxed, suspensory ligaments taut Near – lens short and fat ciliary muscle contacted, suspensory ligaments loose

74 Nerves Synapses and Drugs
Some drugs stimulate synapses like a neurotransmitter, LSD and nicotine Others block the enzyme that normally breaks down the neurotransmitter Alcohol depresses synaptic activity in the brain and acts as a depressant. So do solvents

75 The CNS and Reflex Actions

76 Hormones Proteins that are chemical messengers in the body
Carried in the blood to target cells Response is slower May last for hours Can stimulate more than one target

77 Controlling glucose, After eating a lot of carbohydrate blood sugar level rises. Islets of Langerhans in the pancreas release insulin, the glucose is stored as glycogen in the liver. The blood sugar level drops . When blood sugar levels are low the insulin production stops. Glucagon is produced by the pancreas allowing glucose release from the liver and muscles.

78 Uses of Hormones Controlling fertility – the contraceptive pill, may contain oestrogen and progesterone and controls the release of pituitary hormones and ovulation Mini pill, progesterone allows ovulation but makes the vagina and uterus unsuitable for sperm Anabolic steroids build muscle – reduce the production of testosterone

79 Uses of plant hormones Auxins allow plants to respond to the environment – tropic responses Auxin (IAA) causes - They stimulate shoots to grow rapidly Stops side shoots growing Stimulates growth of roots from the base of stems or leaves Auxin from seeds cause fruit to swell

80 Plant responses and Auxins
Hormone rooting powder causes roots to grow from cut stems Seedless fruits –grapes, cucumbers, bananas. (parthenocarpy) Selective weedkillers 2-4-D causes weeds to grow too fast and results in death, grass doesn’t take it up well Q 3,4,5 page 102 for Wednesday

81 Homeostasis Temperature Control Water Control Salt Balance
Sugar control Carbon Dioxide Control Urea

82 Temperature Control Thermoregulation keeps the body at constant temperature (37oC). Enzymes work best. Temperature is regulated by the hypothalamus.

83 Temperature Control Heat is made in most cells but in particular muscle and liver. Heat is lost by convection, conduction and radiation. Evaporation of water from a surface removes heat.

84 Keeping Cool Vasodilation, more blood flows nearer the skin and heat is lost. Sweating, evaporation causes heat loss. Hairs lie flat allowing more heat out.

85 Keeping Warm Vasoconstriction - less blood flows to the skin’s surface, keeping heat in. You may look pale!! Decrease in sweat. Shivering generates heat (respiration). Hairs stand up and trap insulating air.

86 Carbon dioxide Excess carbon dioxide results in a drop in the body’s pH (acidic). Breathing out removes this excess. The rate and depth of breathing will alter to suit the amount of CO2.

87 The Kidney

88 Urea Urea is produced when proteins and amino acids are broken down in the liver. It is poisonous. The kidneys remove it but so does sweating !!

89 The kidney

90 The kidneys have four functions:
Regulation of blood water levels Reabsorption of useful substances into the blood Adjustment of the levels of salts and ions in the blood Excretion of urea and other metabolic wastes

91 Kidneys: how they work

92 Kidney transplant This is when the diseased kidney is surgically removed and replaced by a fully functioning kidney from a deceased or a live donor. It is only possible after a satisfactory tissue-match. Even after a successful tissue-match the recipient's immune system has to be drugged or suppressed to stop it from rejecting the new kidney.

93 Kidney failure In the event of kidney failure due to infection or disease, the kidney can no longer remove metabolic waste products from the body. Excretion of metabolic waste is a vital function and their accumulation will result in eventual death. There are two solutions to the problem of kidney malfunction or failure: Kidney transplant Kidney dialysis


95 Kidney dialysis In the absence of a suitable donor kidney, the alternative solution is for the patient to be hooked-up to a dialysis machine every days. A dialysis machine mimics the functioning of the kidney. Blood from an artery in the patient's arm is pumped into the kidney machine which removes urea and excess salts from it. The blood is checked for air bubbles before being returned to a vein in the arm.

96 Osmoregulation Is keeping the water and salt levels constant in the blood. They are regulated by the hypothalamus. Water moves into the cells by osmosis and could cause them to burst.

97 Blood concentration too high
The hypothalamus senses too little water in the blood. A message is sent to the pituitary gland to release anti-diuretic hormone. This stops the kidneys removing water and going to the loo!!

98 Blood concentration too low.
Too much water in the blood stops the hypothalamus signalling the pituitary. Water is removed by the kidneys. Large amounts of dilute urine produced.

99 Cell Division - Mitosis


101 DNA DNA structure discovered by Crick and Watson

102 Genetic and Environmental causes of Variation
Variation is inherited Genetic – skin colour Environmental – hair length Both – height, weight, intelligence

103 Asexual reproduction Produces identical copies called clones – onions, strawberries, potatoes, greenfly This type of cell division is mitosis Cuttings and grafting in plants Micropropogation used by growers

104 Mutations Change in the DNA of an organism caused by an error when it is copied Radiation and certain chemicals such as cigarette smoke can cause mutations Most are harmful and leads to illness or death Useful ones are rare but have a dramatic impact on a species and its evolution

105 Harmful mutations Down’s syndrome – an extra chromosome number 21
Cystic fibrosis is caused by a mutation in the DNA. It is a recessive allele which affects 1 in 2000 children. It causes sticky mucus which blocks the lungs and pancreas

106 Genetic Engineering Is the ability to alter DNA
A gene from one organism can be transferred into the DNA of a completely different organism In some cases the all the DNA is removed from a cell and replaced with the DNA from another organism Dolly the sheep was the first example of genetic cloning

107 Selective Breeding In animals – dogs, cows, sheep, cats and so on. To produce certain traits In plants for taste, texture, shelf life Is done by choosing parents with the required traits. These are then bred to produce offspring. Sexual reproduction will ensure variation

108 Mendel Studied peas and concluded that characteristics were passed on from one generation to another. Law of segregation – the 2 alleles separate when gametes are formed, one allele into one gamete and the other into another Law of independent assortment – any gamete of the father can fertilise any gamete of the mother

109 Genetic Crosses


111 Evolution Most organisms overproduce
Population numbers remain constant Sexual reproduction ensures that all offspring exhibit variation These variations are inherited from the parents From these Darwin produced his theory of evolution

112 Darwin Evidence for evolution Fossils
Homologous structures –bat’s wing, forearm, horse’s leg.

113 New Species – Survival of the Fittest
The peppered moth Pale ones no longer camouflaged during the Industrial Revolution – were no longer camouflaged Darker ones survived to reproduce and some of their offspring were even darker This is survival of the fittest

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