Biology
Edexcel International GCSE in Biology (4BI0)
First examination June 2013
1
The nature and variety of living
organisms
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Characteristics of living organisms
Variety of living organisms
2
Characteristics of living organisms
1.1 Understand that living organisms share the following characteristics:
– Respiration
– Reproduction
– Growth
– Response to stimuli
– Maintaining internal environment
– Movement
– Excretion
– Nutrition
3
Variety of living organisms
1.2 describe the common features shared by organisms within the following main groups:
plants, animals, fungi, bacteria, protoctists and viruses, and for each group describe
examples and their features as follows (details of life cycle and economic importance are
not required)
– Plants
– Multicellular
– Contain chloroplasts to carry out photosynthesis.
– Make water and carbon dioxide into organic compounds such as cellulose, which
plants use for walls and starch.
– Animals
– Vertebrates: Mammals, birds, reptiles, amphibians and fish.
– Invertebrates: Crustaceans, insects, starfish, mollusks, sponges and worms.
– Unable to carry out photosynthesis. Gain energy by feeding on other animals or
plants.
4
Variety of living organisms
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Fungi
– Multicellular: Mushrooms, toadstools, molds etc.
– Unicellular: Yeasts
– Do not contain chloroplasts, cannot photosynthesize.
– Have cell walls, made of chitin, not cellulose.
– The mushroom is the reproductive structure of the fungi, called a fruiting body.
– Under the soil the mushroom has many thread-like filaments called hyphae.
– A mold is a mushroom without the fruiting body. The network of hyphae is called
mycelium.
– Molds feed by absorbing nutrients from dead material.
– Many nuclei within one cell in some molds such as Mucor.
5
Variety of living organisms
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Protoctists
– Most protoctists are microscopic single-celled organisms.
– Protozoa look like animal cells, such as Amoeba, which lives in pond water.
– Algae have chloroplasts and carry out photosynthesis therefore more like plants.
– Most algae are unicellular but some species such as seaweeds are multicellular.
– Malaria is caused by the protoctist Plasmodium.
6
Variety of living organisms
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Bacteria
– Bacteria are small single-celled organisms. A much simpler structure.
– Three basic shapes of bacteria: spheres, rods and spirals.
– Spheres come in singles, pairs, chains or groups.
– Rods come in singles or chains, with or without flagella.
– Surrounded by a cell wall, protects the bacterium. Made of polysaccharides and
proteins.
– Some species have another layer outside the wall called a capsule or slime
layer. Both give the bacterium extra protection.
– Has no nucleus, instead its DNA is in a single chromosome, loose in the
cytoplasm.
– Some bacteria can swim using movements from structures called flagella.
– Plasmids also contain some of the bacterium’s DNA.
– Some bacteria contain a form of chlorophyll, and can carry out photosynthesis.
– Most bacteria feed off living or dead organisms.
– Important decomposers, other species are pathogens which cause disease.
7
Variety of living organisms
1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria, protoctists
or viruses
– A pathogen is a agent that can cause disease and harm, it may be a fungi, bacteria,
protoctist or virus.
8
Structures and functions in living
organisms
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–
–
–
–
–
–
–
–
–
Levels of organization
Cell structure
Biological molecules
Movement of substances into and out of cells
Nutrition
Respiration
Gas exchange
Transport
Excretion
Coordination and response
9
Levels of organization
2.1 describe the levels of organization within organisms: organelles, cells, tissues, organs
and systems
– Organelles  Cells  Tissue  Organ  System
– Organelle: Mitochondria
– Cell: Sperm Cell
– Tissue: Muscle
– Organ: Heart
– System: Pulmonary System
10
Cell structures
2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall,
chloroplast and vacuole
11
Cell structures
2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast
and vacuole
– Nucleus: The nucleus controls the cell, also contains DNA which is important for cell
reproduction.
– Cytoplasm: Where chemical reactions take place, the mitochondria in the cytoplasm
facilitates respiration. It also contains enzymes.
– Cell membrane: It controls what goes in and out of the cell.
– Cell wall: Made of cellulose, it gives the shape and structure of the cell to provide
support. It becomes turgid when it is full of water.
– Chloroplast: Contain the green chlorophyll substance that allows it to absorb light
energy and convert it to chemical energy in photosynthesis.
– Vacuole: Contains cell sap, the storage of the cell and maintains the cell structure.
12
Cell structure
2.4 compare the structures of plant and animal cells.
Feature
Animal Cells
Plant Cells
Nucleus
Yes
Yes
Cell membrane
Yes
Yes
Mitochondria
Yes
Yes
Cytoplasm
Yes
Yes
Cell wall
No
Yes
Chloroplasts
No
Yes
Permanent vacuole
No
Yes
Structure
Variable
Square
13
Biological molecules
2.5 identify the chemical elements present in carbohydrates, proteins and lipids (fats and
oils)
– Carbohydrates and lipids:
– Carbon, hydrogen, oxygen
– Protein:
– Carbon, hydrogen, oxygen, sulfur, phosphorous, nitrogen
2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made
up from smaller basic units: starch and glycogen from simple sugar; protein from amino
acids; lipid from fatty acids and glycerol
– Glucose, maltose  starch, glycogen
– Amino acids  protein
– Fatty acids, glycerol  lipids, fats
14
Biological molecules
2.7 describe the tests for glucose and starch
– Glucose:
– To test for glucose, dissolve the sample in water and add drops of Benedict’s
reagent until the solution is colored blue. When the solution is heated, it will turn
orange-red if glucose is present.
– Starch:
– To test for starch, add a drop of iodine solution to the sample. The solution will
turn blue-black color if starch is present.
2.8 understand the role of enzymes as biological catalysts in metabolic reactions
– Enzymes are biological catalysts; they speed up reactions inside cells.
– They are proteins.
15
Biological molecules
2.9 understand how the functioning of enzymes can be affected by changes in
temperature, including changes due to change in active site
– High temperatures denature enzyme by changing the shape of the active site so it is
no longer compatible with the substrate.
– Low temperatures lower the rate of reaction of the enzyme.
2.10 understand how the functioning of enzymes can be affected by changes in
active site caused by changes in pH
– A change in pH, whether more acidic or basic, will change the shape of the active site
and denature the enzyme.
2.11 describe experiments to investigate how enzyme activity can be affected by changes
in temperature.
– Refer to experiment section
16
Movement of substances into and
out of cells
2.12 understand definitions of diffusion, osmosis and active transport
– Diffusion is:
– Movement of particles
– High concentration  low concentration
– Passive: does not use energy
– Osmosis is:
– Movement of water
– Semi-permeable membrane
– High concentration  low concentration
– Passive: does not use energy
– Active transport is:
– Movement of particles
– Low concentration  high concentration
– Across a selectively permeable membrane
– Active: uses energy produced by cellular respiration
17
Movement of substances into and
out of cells
2.13 understand that movement of substances into and out of cells can be by diffusion,
osmosis and active transport
– Cell membranes are partially permeable, so osmosis takes place across cell
membranes.
2.14 understand the importance in plants of turgid cells as a means of support
– The turgor of plant cells is important for to support the plant.
– If the plant loses water through osmosis, the cell contents decrease in volume and
the cytoplasm no longer pushes against the cell wall.
– The cell is flaccid.
– The cell cannot support the plant tissues and the plant wilts.
– Wilting helps protect the plant from further water loss.
18
Movement of substances into and
out of cells
2.15 understand the factors that affect the rate of movement of substances into and out
of cells, to include the effects of surface area to volume ratio, temperature and
concentration gradient
– Surface area: the higher the surface area, the faster the rate of movement.
– This is because there is more area of contact for diffusion to occur.
– Temperature: the higher the temperature, the faster the rate of movement.
– This is because the temperature increases the kinetic energy of the particles.
– Concentration gradient: The steeper the con. gradient, the faster the rate of
movement.
2.16 describe experiments to investigate diffusion and osmosis using living and non-living
systems.
– Refer to experiment section
19
Nutrition
2.17 describe the process of photosynthesis and understand its importance in the
conversion of light energy to chemical energy
– The leaves of plants make glucose from carbon dioxide and water using the light
energy of the sun. The waste product is oxygen.
– The light energy of the sun is captured by chlorophyll in chloroplasts in the leaves and
converted to chemical energy in glucose.
– Glucose is converted into sucrose to be transported around the plant and into starch
to be stored.
– The glucose from photosynthesis is used to make cellulose for cell walls, proteins and
DNA, chlorophyll, lipids as an energy store for seeds
2.18 write the word equation and the balanced chemical symbol equation for
photosynthesis
– Carbon dioxide + water  glucose + oxygen
– 6CO2 + 6H2O  C6H12O6 + 6O2
20
Nutrition
2.19 understand how varying carbon dioxide concentration, light intensity and
temperature affect the rate of photosynthesis
– The higher each of the factors are, the faster the rate of photosynthesis.
– However, the rate of photosynthesis will only increase as long as the limiting factor
is increasing. The limiting factor is the component of the reaction that is not in
excessive supply and limits the rate at which the reaction can take place.
2.20 describe the structure of the leaf and explain how it is adapted for photosynthesis
– They are thin and flat so the surface area to absorb light is as large as possible and
the distances that gases need to diffuse are short.
21
Nutrition
22
Nutrition
2.21 understand that plants require mineral ions for growth and that magnesium ions are
needed for chlorophyll and nitrate ions are needed for amino acids
– Plants need mineral ions, which they take from the soil to survive and grow.
– Nitrates ions are used to make amino acids.
– Magnesium ions are used to make chlorophyll.
2.22 describe experiments to investigate photosynthesis, showing the evolution of
oxygen from a water plant, the production of starch and the requirements of light, carbon
dioxide and chlorophyll
– Refer to experiment section
2.23 understand that a balanced diet should include appropriate proportions of
carbohydrate, protein, lipid, vitamins, minerals, water and dietary fiber
– A balanced diet should include carbohydrate, protein, fats / lipids, vitamins, minerals,
water and dietary fiber.
23
Nutrition
2.24 identify sources and describe functions of carbohydrate, protein, lipid (fats and oils),
vitamins A, C and D, and the mineral ions calcium and iron, water and dietary fiber as
components of the diet
– Carbohydrates are the main fuel of the body.
– Cell release energy from glucose.
– Most of the carbohydrate that forms our diet is from starch.
– Plant cells are made of cellulose that is made from carbohydrates, it is used as fiber
or roughage because we cant digest it.
– Simple sugar is glucose, fructose, sucrose, etc.
– Complex carbohydrates such as starch, glycogen, cellulose, etc. are made of simple
sugar joined together.
– Carbohydrates are found in bread, pasta and rice.
24
Nutrition
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Proteins are used for growth and repair of tissues.
They are made up long chains of amino acids.
They contain carbon, hydrogen and oxygen, but have nitrogen and sulfur as well.
Proteins are found in meat, fish and cheese.
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–
Lipids (fats and oils) are made of glycerol and fatty acids.
They are made up of the same elements as carbohydrates – oxygen, carbon,
hydrogen, but there is much less carbon.
They contain a lot of energy and are used as energy stores.
It is used as insulation, also to protect organs.
Lipids are found in butter, corn oil and eggs.
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–
–
25
Nutrition
–
Vitamins
Vitamin
A
B
C
D
Use in body
Chemical in retina
Helps with respiration
Strengthens immune
system, sticks together
cell linings.
Helps bones absorb
calcium
Effect of Deficiency
Night blindness
Weak muscles, dry skin
Scurvy
Example of foods
Carrots, liver oils
Cereals, eggs, fish
Fresh fruit and
vegetables
Rickets, poor teeth
Fish liver oils; made
in skin in sunlight
26
Nutrition
–
Minerals
Mineral
Calcium
Phosphorus
Sodium
Chlorine
Magnesium
Iron
Location or role in body
Make teeth and bones
Make teeth and bones
In body fluids e.g. blood
In body fluids e.g. blood
Making bones; found in cells
Makes haemoglobin
Example of foods
Dairy products
Most foods
Common salt, most foods
Common salt, most foods
Green Vegetables
Red meat, eggs, spinach
27
Nutrition
–
Water is important in the body as a solvent for breaking up large molecules by
hydrolysis.
–
Fiber is important in the body as a bulk for the muscles of the gut to move. It assists
peristalsis.
2.25 understand that energy requirements vary with activity levels, age and
pregnancy
– People need more energy in the early – mid sections of their life due to higher activity
levels and energy is used for growth.
– A pregnant woman not only has to supply energy for herself, but also for her baby.
28
Nutrition
2.26 describe the structures of the human alimentary canal and describe the functions of
the mouth, esophagus, stomach, small intestine, large intestine and pancreas
– The alimentary canal is the muscular tube that runs from the mouth to the anus.
– Mouth: Physically breaks down the food to make it easier to digest. Saliva lubricates
the food and also contains the enzyme amylase.
– Esophagus: The pipe by which food enters the stomach from the mouth.
– Stomach: Acidic conditions kills bacteria in the food and provides the optimum pH for
enzyme pepsin. Muscular contractions in the stomach mix the food up with gastric
juices. The mixture is now called chyme.
– Small intestine: At the duodenum, the acidic chyme is made alkaline with bile from the
gall bladder. It also emulsifies fats. In the small intestine, absorption takes place.
– Large intestine: This is where the water is reabsorbed leaving behind feces.
– Pancreas: Produces enzymes and pancreatic juice which digests lipids.
29
Nutrition
30
Nutrition
2.27 understand the processes of ingestion, digestion, absorption, assimilation and
egestion
– Ingestion is the intake of food via the mouth (eating).
– Digestion is the breakdown of macromolecules into smaller, soluble molecules.
– Absorption is the products of digestion being absorbed into the bloodstream.
– Assimilation is the distribution of digested food products into the cells .
– Egestion: The removal of water from the matter coming out of the small intestine.
After the removal of water, it is passed out through the anus as feces.
2.28 explain how and why food is moved through the gut by peristalsis
– Peristalsis is the way in which the bulk of food is moved through the alimentary
canal.
– The muscles before the bulk of food contracts, pushing the food forward.
– The muscles after the bulk of food relaxes, letting the food through.
– Fibers help with peristalsis, they give more bulk so it is easier to push it forward as it
fills up the entire channel.
31
Nutrition
2.29 understand the role of digestive enzymes, to include the digestion of starch to
glucose by amylase and maltase, the digestion of proteins to amino acids by proteases
and the digestion of lipids to fatty acids and glycerol by lipases
Class
Examples Action
Carbohydras Amylase
Starch  Maltose
e
Maltase
Maltose  Glucose
Proteases
Lipases
Pepsin
Proteins  Peptides
Peptidase Peptides  Amino Acids
s
Lipase
Lipids  Glycerol and Fatty
Acids
Source
Pancreas
Where
Mouth
Small Int.
Small Int.
Pancreas
Stomach
Small Int.
Small Int.
Pancreas
Small Int.
32
Nutrition
2.30 understand that bile is produced by the liver and stored in the gall bladder, and
understand the role of bile in neutralizing stomach acid and emulsifying lipids
– Bile is produced in the liver, stored in the gall bladder.
– It neutralizes stomach acid and emulsifies fats, making them easier for lipase to
digest.
2.31 describe the structure of a villus and explain how this helps absorption of the
products of digestion in the small intestine
– Shape gives a large surface area
– A good blood supply to maintain high concentration gradient
– Microvilli extensions to further increase surface area
– Lacteal allows absorption of fats
– Capillaries only one cell thick to facilitate fast diffusion
33
Nutrition
2.32 describe an experiment to investigate the energy content in a food sample.
– Refer to experiment section
34
Respiration
2.33 understand that the process of respiration releases energy in living organisms
– Respiration is used to produce energy for muscle contraction, active transport,
building up large molecules and cell division.
2.34 describe the differences between aerobic and anaerobic respiration
– Aerobic respiration requires oxygen, anaerobic respiration does not.
2.35 write the word equation and the balanced chemical symbol equation for aerobic
respiration in living organisms
– Carbon dioxide + water  glucose + oxygen
– C6H12O6 + 6O2  6CO2 + H2O
2.36 write the word equation for anaerobic respiration in plants and in animals
– Glucose  lactic acid (+ some energy)
35
Respiration
2.37 describe experiments to investigate the evolution of carbon dioxide and heat
from respiring seeds or other suitable living organisms.
Refer to experiment section
36
Gas exchange
2.38 understand the role of diffusion in gas exchange
– In humans, gas exchange depends on the efficient diffusion of gases.
2.39 understand gas exchange (of carbon dioxide and oxygen) in relation to respiration
and photosynthesis
– Plants respire all the time, using oxygen and producing carbon dioxide.
– The rate of photosynthesis is not constant, which uses carbon dioxide and produces
oxygen.
2.40 understand that respiration continues during the day and night, but that the
net exchange of carbon dioxide and oxygen depends on the intensity of light
– Respiration occurs constantly, but photosynthesis is dependent on light levels.
– Therefore, the volume of carbon dioxide used up and the volume of oxygen produced
is variable throughout a 24 hour period.
37
Gas exchange
2.41 explain how the structure of the leaf is adapted for gas exchange
– Spongy mesophyll cells have air space for gas diffusion.
– Palisade mesophyll cells are tightly packed with chloroplasts.
– Lower epidermis has more stoma and guard cells.
2.42 describe the role of stomata in gas exchange
– The stoma is a pore that controls gas exchange.
– The light intensity stimulate the stoma to open and close.
2.43 describe experiments to investigate the effect of light on net gas exchange
from a leaf, using hydrogen-carbonate indicator
– Refer to experiment section
38
Gas exchange
2.44 describe the structure of the thorax, including the ribs, intercostal muscles,
diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes
– The lungs are enclosed in the cheat by the ribcage or thorax and a muscular sheet of
tissue called the diaphragm. Joining each rib to the next are two sets of muscles
called intercostal muscles.
– The bronchial tree is the air passages of the lungs. Enters our nose or mouth and
passes down the trachea. This then splits into two tubes called the bronchi, one
leading to each lung. Each bronchus divides into smaller tubes called bronchioles,
eventually ending at microscopic air sacs celled alveoli. Here is where gas exchange
takes place.
– The walls of the trachea and bronchi contain rings of cartilage to support the airways
and keep them open when we breathe in. The inside of the thorax are separated from
the lungs by two thin membranes called the pleural membrane. They make an
envelope around the lungs, forming an airtight seal.
39
Gas exchange
40
Gas exchange
2.45 understand the role of the intercostal muscles and the diaphragm in ventilation
– Inhalation:
– External intercostal muscles contract pulling ribs up and out.
– Muscles in the diaphragm contract pulling the diaphragm down.
– Increase in volume in the thorax  Lower concentration of air  Air enters.
– Exhalation:
– Internal intercostal muscles contract pulling ribs down and in.
– Muscles in the diaphragm relax to let diaphragm return to a dome shape.
– Decrease in volume in the thorax  Higher concentration of air  Air exits.
41
Gas exchange
2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the
lungs and blood in capillaries
– Alveoli are wrapped in capillaries; to keep a constant fresh blood flow.
– The steep concentration gradient facilitates maximum diffusion.
– Alveoli are ball shaped; to create maximum surface area.
– The larger surface area allows it to absorb more oxygen at any given time.
– Capillaries are only 1 cell thick; short diffusion distances between air and blood.
– This means they have to travel a less, allowing a faster diffusion rate.
42
Gas exchange
2.47 understand the biological consequences of smoking in relation to the lungs and the
circulatory system, including coronary heart disease
– Carbon monoxide binds to hemoglobin and takes the place of oxygen. This will lower
oxygen levels in the blood.
– Cilia is destroyed so dirt, bacteria and mucus is not swept away. This clogs the air
passages.
– Irritates the cell linings, causing them to produce more mucus. Can lead to
bronchitis.
– The walls of the alveoli are damaged and break down to form large irregular air
spaces, this makes less surface area and gas exchange is made less effective. This
is called emphysema.
– Tar and other chemicals cause cells to mutate and form cancers in the lungs and
throat.
2.48 describe experiments to investigate the effect of exercise on breathing in humans.
– Refer to experiment section
43
Transport
2.49 understand why simple, unicellular organisms can rely on diffusion for movement of
substances in and out of the cell
– Unicellular organisms such as fungi can rely on diffusion because they have high
surface area to volume ratio and are small, thus diffusion occurs quickly.
2.50 understand the need for a transport system in multicellular organisms
– Multicellular organisms such as animals cannot rely on diffusion, and need a
transport system because they have a small surface area to volume ratio and are
large, thus diffusion occurs slowly.
– Therefore, transport systems such as ventilation and circulatory systems are
developed to speed up diffusion to support themselves.
44
Transport
2.51 describe the role of phloem in transporting sucrose and amino acids between
the leaves and other parts of the plant
– Phloem tissue is made of living cells.
– It transports sugars for energy and amino acids for cell building all around the plant.
– It travels upwards and downwards
2.52 describe the role of xylem in transporting water and mineral salts from the roots to
other parts of the plant
– Xylem tissue is made of cell walls of dead cells.
– It transports water and mineral ions up from the roots to the rest of the plant.
– It is waterproofed with lignen.
– It only travels upwards.
45
Transport
46
Transport
2.53 explain how water is absorbed by root hair cells
– In the uptake of water:
– The root hair cells greatly increase the surface area for the uptake of water.
– Water enters the root cells through osmosis, it moves across root cells to the
xylem along a concentration gradient.
– In the uptake of minerals:
– Mineral ions are at a very low concentration in the soil water.
– They are moved into root hair cells against a concentration gradient.
– This is done using active transport.
2.54 understand that transpiration is the evaporation of water from the surface of a plant
– Transpiration is the evaporation and removal of water from the surface of the plant,
namely the leaf.
– Transpiration is a process of pulling the water up from the xylem and out of the stoma
through the plant. This is called the transpiration stream and runs by osmosis.
47
Transport
2.55 explain how the rate of transpiration is affected by changes in humidity, wind speed,
temperature and light intensity
– Light intensity stimulates the stoma to open and close.
– Temperature affects the rate of evaporation.
– Humidity affects how long it takes for the water vapor to diffuse.
– Wind blows the wind vapor away and replaces it with drier air.
2.56 describe experiments to investigate the role of environmental factors in determining
the rate of transpiration from a leafy shoot
– Refer to the experiment section
48
Transport
2.57 describe the composition of the blood: red blood cells, white blood cells, platelets
and plasma
– Blood is made of:
– Red blood cells
– White blood cells
– Phagocytes
– Lymphocytes
– Platelets
– Plasma
2.58 understand the role of plasma in the transport of carbon dioxide, digested food,
urea, hormones and heat energy
– Plasma is the yellow liquid which transports, dissolved food molecules, carbon
dioxide, urea, hormones, and heat.
– It is mainly made of water.
49
Transport
2.59 explain how adaptations of red blood cells, including shape, structure and the
presence of hemoglobin, make them suitable for the transport of oxygen
– Biconcave, disc-shape maximizes surface area.
– It is flexible and elastic, so it fits into thin capillaries.
– Presence of hemoglobin allows it to carry oxygen.
– Thin cell membrane allows for a quicker exchange of oxygen.
– Containing no nucleus means there is more space for hemoglobin.
2.60 describe how the immune system responds to disease using white blood cells,
illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies
specific to the pathogen
– Lymphocyte has a large spherical nucleus and it produces antibodies to destroy
organisms. Lymphocytes form memory cells that if the pathogen infects the body
again it can be dealt with quickly before the body experiences symptoms.
– Phagocyte is a large cell with a lobed nucleus and engulfs the bacteria and other
organisms that are tagged by antibodies.
50
Transport
2.61 understand that vaccination results in the manufacture of memory cells,
which enable future antibody production to the pathogen to occur sooner, faster
and in greater quantity
– Vaccination produces artificial immunity.
– The patient is given a weakened or dead strain of the pathogen.
– The lymphocytes produce antibodies to the antigens of the pathogen.
– They also create memory cells ready for a secondary immune response.
2.62 understand that platelets are involved in blood clotting, which prevents blood
loss and the entry of micro-organisms
– Platelets release a chemical thrombin when exposed to air.
– Thrombin turns soluble fibrinogen into insoluble fibrin.
– The fibrin forms a insoluble protein threads which forms a clot, then a scab.
– Blood clotting prevents blood loss and the entry of micro-organisms.
51
Transport
2.63 describe the structure of the heart and how it functions
– Cardiac Cycle
– Blood enters the atrium; it cannot pass into the ventricles because the tricuspid
and bicuspid valves are closed.
– Pressure builds, the walls of the atria contract, the pressure forces open the
bicuspid and tricuspid valves into the ventricles.
– When the ventricles are full, they contract. The pressure closes the tricuspid and
bicuspid valves. Blood cannot return to the atrium.
– The ventricles continue to contract and the pressure forces open the semi-lunar
valves at the base of the aorta and the pulmonary artery.
– Vena Cava: Deoxygenated blood enters the right atrium.
– Pulmonary Artery: Deoxygenated blood exits the right ventricle.
– Pulmonary Vein: Oxygenated blood enters the left atrium.
– Aorta: Oxygenated blood exits the left ventricle.
– Systole: When a chamber of the heart is contracting. Diastole: When a chamber of
the heart is relaxing.
52
Transport
53
Transport
2.64 explain how the heart rate changes during exercise and under the influence of
adrenaline
– During exercise, oxygen is in a higher demand, thus the heart rate increases to
compensate.
– Adrenaline makes the heart speed up because it anticipates a extra need in oxygen
and energy.
2.65 describe the structure of arteries, veins and capillaries and understand their roles
– Arteries take blood away from the heart.
– High pressure, thick muscle wall and small lumen.
– Veins take blood to the heart.
– Low pressure, thin muscle wall and large lumen.
– Valves to prevent backflow.
– Capillaries carry blood through organs, bring blood close to every cell.
– The walls are about one cell thick.
54
Transport
2.66 understand the general structure of the circulation system to include the blood
vessels to and from the heart, the lungs, the liver and the kidneys.
55
Excretion
2.67 understand the origin of carbon dioxide and oxygen as waste products of
metabolism and their loss from the stomata of a leaf
– Oxygen is a waste product of photosynthesis.
– Carbon dioxide is a waste product of respiration.
2.68 recall that the lungs, kidneys and skin are organs of excretion
– Lungs, kidneys and skin are organs of excretion.
– Excretion is the removal of the waste products of metabolism.
2.69 understand how the kidney carries out its roles of excretion and osmoregulation
– The kidneys balance the amount of water left in the blood, hence osmoregulation. It
also filter substances out of the blood.
– The kidney filters the blood from the renal artery and the clean blood exits in t he
renal vein.
56
Excretion
2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder
and urethra
– The urine passes out of the kidney through the ureters and is stored in the bladders
until the sphincters are relaxed to release the urine out through the urethra.
2.71 describe the structure of a nephron, to include Bowman’s capsule and glomerulus,
convoluted tubules, loop of Henlé and collecting duct
57
Excretion
2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the
glomerular filtrate
– The process of ultrafiltration occurs in the Bowman’s capsule.
58
Excretion
–
–
Ultrafiltration is the filtration of blood under high pressure.
The filter filters by size, therefore, the resultant mixture called the glomerular filtrate is
made of:
– Water
– Glucose
– Salts
– Urea
– Protein
2.73 understand that water is reabsorbed into the blood from the collecting duct
– Water is reabsorbed at the collecting duct.
– The amount depends on the condition of the body, and thus the level of ADH
hormone.
59
Excretion
2.74 understand that selective reabsorption of glucose occurs at the proximal convoluted
tubule
– The process of selective reabsorption reabsorbs the glucose and protein.
– This includes both diffusion and active transport.
– Glucose is reabsorbed at the proximal convoluted tubule.
– Ions are reabsorbed at the distal convoluted tubule.
2.75 describe the role of ADH in regulating the water content of the blood
– ADH (antidiuretic hormone) changes the permeability of the collecting ducts.
– Water concentration in blood low  detected in hypothalamus  pituitary gland
releases more ADH  ADH travels to kidney through blood  more water
reabsorbed  less water in the urine  Water concentration in blood restored 
ADH production returns to normal.
60
Excretion
2.76 understand that urine contains water, urea and salts.
– Urine contains water, urea and salts. It is the remainder of what has not been
reabsorbed in the nephron.
61
Coordination
2.77 understand that organisms are able to respond to changes in their environment
– Organisms respond to changes in their environment through nervous and hormonal
coordination and control systems.
2.78 understand that homeostasis is the maintenance of a constant internal environment
and that body water content and body temperature are both examples of homeostasis
– Homeostasis is the maintenance of a constant internal environment, this is done
through negative feedback.
– Negative feedback is when the body senses a change, it will produce a negative
change to maintain a constant internal environment.
– Body getting hot  Body cools itself down
– Body temperature:
– When the body is cold: hairs stick up to trap air to insulate the body; blood
vessels near the skin constrict (vasoconstriction); shivering to generate heat from
muscles.
– When the body is hot: hairs flatten; blood vessels near the skin dilate
(vasodilation); the rate of breathing increases; sweating; panting loses heat.
62
Coordination
–
Body water content:
– When there is high water content in blood: less ADH is produced  less water
reabsorbed by the body  large amount of dilute urine formed
– When there is low water content in blood: more ADH is produced  more water
reabsorbed by the body  low amount of dilute urine formed
2.79 understand that a coordinated response requires a stimulus, a receptor and an
effector
– e.g. Stimulus: Fire  Receptor: Hand  Effector: Muscle pulling hand back
2.80 understand that plants respond to stimuli
– Plants respond very slowly due to the lack of a nervous system. Plant’s responses to
stimuli are known as tropisms.
63
Coordination
2.81 describe the geotropic responses of roots and stems
– Roots have a positive geotropic response.
– They grow towards the direction of gravity.
– Stems have a negative geotropic response.
– They grow away from the direction of gravity.
2.82 describe positive phototropism of stems
– Stems have a positive phototropic response.
– They grow towards the source of light.
64
Coordination
2.83 describe how responses can be controlled by nervous or by hormonal
communication and understand the differences between the two systems
– Responses can be controlled by nervous or hormone system.
Hormones
Slow but long lasting.
Can affect multiple organs.
Through blood stream.
Nerves
Instant effect, but short.
Affects individual organs.
Through nerves.
2.84 understand that the central nervous system consists of the brain and spinal cord
and is linked to sense organs by nerves
– The central nervous system (CNS) consists of the brain and spinal cord and is linked
to sense organs by nerves.
65
Coordination
2.85 understand that stimulation of receptors in the sense organs sends electrical
impulses along nerves into and out of the central nervous system, resulting in rapid
responses
– The messages are sent through electrical impulses.
– The gaps between each neurone is called a synapse.
– Electrical impulses travel very quickly, leading to rapid responses.
2.86 describe the structure and functioning of a simple reflex arc illustrated by the
withdrawal of a finger from a hot object
– Stimulus (fire)  Receptor (skin)  CNS  Effector (arm muscle)  Response
(withdrawal of hand)
– Sensory cell in the skin sends a electrical response along the sensory neurone.
– At the CNS, a relay neurone links with a motor neurone, and the impulse is
passed.
– The impulse reaches the effector muscle, which contracts.
66
Coordination
2.87 describe the structure and function of the eye as a receptor
– Schlera: Tough coat surrounding eye.
– Chloroid: Prevents light reflecting.
– Cornea: Refracts light in, protects eye.
– Pupil: Transparent window.
– Iris: Controls size of the pupil.
– Lens: Focuses eye by refraction.
– Retina: Light rays transformed into
nerve impulses (rods and cones)
– Fovea: Center of the retina (many rods and cones)
– Optic nerve: Passes impulses to the brain.
67
Coordination
2.88 understand the function of the eye in focusing near and distant objects, and in
responding to changes in light intensity
– Bright Light: Circular muscles contract, radial muscles relax, pupil constricts.
– Focusing on Distant Object: Ciliary muscles relax, suspensory ligament pulled tight,
lens flat.
– Focusing on nearby object: Ciliary muscles contract, suspensory ligament slack, lens
convex.
2.89 describe the role of the skin in temperature regulation, with reference to
sweating, vasoconstriction and vasodilation
– Hot: hairs flat, sweating, vasodilation
– Cold: hairs erect, vasoconstriction
68
Coordination
2.90 understand the sources, roles and effects of the following hormones: ADH,
adrenaline, insulin, testosterone, progesterone and oestrogen.
– The endocrine system is the system that produces hormones that affect other parts
of the body.
Hormone
Oestrogen
Progesterone
Anti-Diuretic
Adrenalin
Insulin
Where it is produced
Ovaries
Ovaries (corpus luteum)
Pituitary Gland
Adrenal Gland
Islets in Pancreas
Testosterone
Testes
Effect
Build uterus wall, prompts ovulation.
Maintains and repairs uterus wall.
Stimulates kidney to reabsorb water.
Increases heart rate; fight or flight.
Stimulates liver to store glucose as
glycogen.
Secondary sex characteristics in
males.
69
Reproduction and inheritance
–
–
Reproduction
Inheritance
70
Reproduction
3.1 understand the differences between sexual and asexual reproduction
– Asexual reproduction involves only one parent. The offspring are identical to the
parent.
– Sexual reproduction involves joining two sex cells (gametes). The offspring are not
identical to the parent.
Feature
Sexual Reproduction
Asexual Reproduction
Sex Cells Produced
Fertilization
Variation in Offspring
Has survival value in:
Yes
Yes
Yes
Changing environment
No
No
No
Stable environment
3.2 understand that fertilization involves the fusion of a male and female gamete to
produce a zygote that undergoes cell division and develops into an embryo
– The fusion of the male and female gamete is known as fertilization.
– This forms a zygote, which after cell division, develops into a embryo.
– Gametes are sex cells, in humans it is the sperm and the egg.
71
Reproduction
3.3 describe the structures of an insect-pollinated and a wind-pollinated flower and
explain how each is adapted for pollination
–
–
–
Flowers are the sexual organs of the plants. The pollen grains are the male gametes,
and the ovules are the female gametes.
Pollen is formed in the anthers of the stamens. Ovules are formed in the ovaries.
Pollen grains are transferred from the anthers of a flower to the stigma.
72
Reproduction
–
–
–
There are two methods of pollination: insect pollination and wind pollination.
When a plant is wind pollinated:
– Stamens exposed so the wind can easily blow pollen away.
– Stigma is positioned to catch pollen in the wind.
– Stigma is feathery to catch grains.
– Petals are small as there is no need to attract insects.
– Pollen grains designed to be carried by the wind.
When a plant is insect pollinated:
– Stamens are enclosed inside the flower so the insect must make contact.
– Stigma is enclosed inside the flower so the insect must make contact.
– Stigma is sticky so pollen grains attach from insects.
– Petals are large to attract insects.
– Petals are brightly colored to attract insects.
– Nectar as a reward to insects.
– Pollen grains are larger and sticky.
73
Reproduction
3.4 understand that the growth of the pollen tube followed by fertilization leads to seed
and fruit formation
– After pollination, the nucleus of the pollen grain grows a pollen tube down the style
into the ovary to allow it to fertilize with the ovule.
– Once fertilization occurs, a zygote is formed which develops into a seed.
74
Reproduction
–
–
Each seed contains the embryo plant, which has a root (radicle) and a shoot
(plumule), the seed leaves which acts as a food store for the plant while the seed
germinates and the seed coat (testa).
The ovary wall becomes the fruit coat. There are many types of fruit which are
adapted to disperse the seeds as far as possible by water, animals or wind.
Dispersal is important because it avoids competition for resources.
3.5 understand the conditions needed for seed germination
– Warmth for maximum enzyme efficiency
– Water to soften the testa and for chemical reactions in the seed to take place
– Oxygen for respiration to provide energy
3.6 understand how germinating seeds utilize food reserves until the seedling can
carry out photosynthesis
– Food reserves are in the seed leaves (cotyledons) to sustain the seed until it can
carry out photosynthesis.
75
Reproduction
76
Reproduction
3.7 understand that plants can reproduce asexually by natural methods (illustrated by
runners) and by artificial methods (illustrated by cuttings)
– Runners: e.g. strawberries- a second stem extends, when it reaches the ground
cells specialize into root cells and a new plant develops.
– Cuttings: a clipping is put in to plant hormones, encouraging the ends to become
roots, when placed in soil it will then create another plant.
3.8 describe the structure and explain the function of the male and female reproductive
systems
– Sperm: Testis  Seminal Vesicle  Sperm Tubule  Urethra
– Egg: Ovary  Fallopian Tube
– Fertilization occurs in this process:
– Testis  Seminal Vesicle  Sperm Tubule  Urethra  Vagina  Cervix 
Uterus  Fallopian Tube  Meets egg  Fertilizes  Implants in wall of womb
77
Reproduction
78
Reproduction
3.9 understand the roles of estrogen and progesterone in the menstrual cycle
– Estrogen builds the uterus wall and prompts ovulation.
– Progesterone maintains and repairs the uterus wall.
79
Reproduction
–
–
–
–
Occurs every 28 days. Ovulation (discharge of ripe egg from the ovary) occurs at day
15.
Estrogen is released from day 0-7 causing the wall to thicken. The fall in levels of
estrogen prompts ovulation.
Progesterone levels start to rise after ovulation, peaking at day 21. Maintains uterus
wall. Lasts for several days to allow fertilization.
Menstruation occurs when progesterone levels fall. Uterus lining sheds.
3.10 describe the role of the placenta in the nutrition of the developing embryo
– The placenta is a special organ that passes food and oxygen from the mother to the
developing fetus.
– It also takes urea and carbon dioxide from the fetus and passes them into the
mother’s blood, and secretes the hormone progesterone.
– The placenta is connected to the fetus by a umbilical cord.
80
Reproduction
3.11 understand how the developing embryo is protected by amniotic fluid
– Amniotic fluid is the liquid that cushions and protects the fetus as it develops.
3.12 understand the roles of estrogen and testosterone in the development of secondary
sexual characteristics.
– Testosterone develops male secondary sexual characteristics:
– Facial / body hair
– Muscle development
– Deepening of voice
– Estrogen develops female secondary sexual characteristics:
– Body hair
– Breasts
– Beginning of the menstrual cycle
81
Inheritance
3.13 understand that the nucleus of a cell contains chromosomes on which genes are
located
– Chromosomes are contained in the nucleus of the cell. They are made up of DNA,
which is the molecule that carries inherited information.
3.14 understand that a gene is a section of a molecule of DNA and that a gene codes for
a specific protein
– A gene is a section of the molecule DNA.
– A gene controls the development of certain specific characteristics.
3.15 describe a DNA molecule as two strands coiled to form a double helix, the strands
being linked by a series of paired bases: adenine (A) with thymine (T), and cytosine (C)
with guanine (G)
– Adenine links with Thymine
– Cytosine links with Guanine
82
Inheritance
3.16 understand that genes exist in alternative forms called alleles which give rise to
differences in inherited characteristics
– Alleles are different forms of genes that give different characteristics.
– e.g. Blue eye allele / brown eye allele
3.17 understand the meaning of the terms: dominant, recessive, homozygous,
heterozygous, phenotype, genotype and codominance
– Dominant: The characteristic of a dominant allele will show up in offspring even if only
one of the alleles is inherited. (brown / blue allele shows brown eye)
– Recessive: The characteristic of a recessive allele will show up in offspring only if
both alleles are inherited. (blue / blue alleles shows blue eye)
– Homozygous: Both the alleles are the same in the genotype. (blue / blue alleles)
– Heterozygous Two different alleles in the genotype. (brown / blue alleles)
– Phenotype: The physical characteristics of an organism.
– Genotype: The alleles that a organism has.
83
Inheritance
–
Codominance: When both or neither allele is dominant, and both contribute to the
appearance of the offspring. (snapdragon flowers: red / white allele shows pink
flower)
3.18 describe patterns of monohybrid inheritance using a genetic diagram
– White fur allele is recessive (b)
– Brown fur allele is dominant (B)
– Parents: BB (homozygous dominant: brown) and bb (homozygous recessive: white)
–
B
B
b
Bb (Brown)
Bb (Brown)
b
Bb (Brown)
Bb (Brown)
This is called a Punnett square, it shows the results of monohybrid inheritance.
84
Inheritance
85
Inheritance
3.19 understand how to interpret family pedigrees
–
–
–
The normal offspring 4 and 6 must have come from 1 and 2, thus 1 and 2 must have
normal alleles.
1 and 2 show polydactyly, but have normal alleles as well. This means the polydactyly
allele is dominant.
This means that all the offspring with normal number digits must be homozygous
recessive.
86
Inheritance
3.20 predict probabilities of outcomes from monohybrid crosses
– Using the punnett square, we can deduce the probabilities of outcomes from
monohybrid crosses.
– Using the same example of bunnies from before:
– White fur allele is recessive (b)
– Brown fur allele is dominant (B)
– Parents: Both are heterozygous (Bb: brown)
B
b
B
BB (Brown)
Bb (Brown)
b
Bb (Brown)
bb (White)
– The genotype probabilities is written as 1 (BB) : 2 (Bb) : 1 (bb)
– The phenotype probabilities is written as 3 (Brown) : 1 (White)
87
Inheritance
3.21 understand that the sex of a person is controlled by one pair of chromosomes, XX in
a female and XY in a male
– The alleles XX is female. The alleles XY is male.
3.22 describe the determination of the sex of offspring at fertilization, using a genetic
diagram
– The parents are XX and XY.
–
–
–
X
X
X
XX (Female)
XX (Female)
Y
XY (Male)
XY (Male)
1 (XX) : 1 (XY)
1 (Female) : 1 (Male)
50% each
88
Inheritance
3.23 understand that division of a diploid cell by mitosis produces two cells which contain
identical sets of chromosomes
– Two homologous pairs of chromosomes in the parent cell.
– Each chromosome duplicates itself. Now there are four homologous pairs of
chromosomes.
– The cell divides in two; each new cell has a copy of the original two chromosomes.
– Mitosis produces a two new diploid cells.
– Note: the number of pairs in the parent cell may not be only two.
3.24 understand that mitosis occurs during growth, repair, cloning and asexual
reproduction
– Mitosis occurs during:
– Growth
– Repair (replacement of skin cells, gut cells, etc.)
– Cloning
– Asexual reproduction
89
Inheritance
3.25 understand that division of a cell by meiosis produces four cells, each with half the
number of chromosomes, and that this results in the formation of genetically different
haploid gametes
– Two homologous pairs of chromosomes in the parent cell.
– Each chromosome duplicates itself creating 8 chromatids, which are formed in pairs
as chromosomes. Now there are four chromosomes, each containing 2 chromatids
as opposed to the 1 before.
– One chromosome from each homologous goes into the 2 daughter cells.
– Now there are 4 chromatids arranged in 2 chromosomes in each of the 2 daughter
cells.
– The chromatids are separated and one chromatid from each chromosome end up in
a daughter cell, this is random and crossing will occur.
– This creates 4 cells with half the number of chromosomes, known as haploids.
– The crossing creates genetic variation.
90
Inheritance
3.26 understand that random fertilization produces genetic variation of offspring
– The separation of the two strands of chromatids creates genetic variation.
Additionally, when two gametes (haploids) come together to form the zygote (diploid),
there is genetic variety.
3.27 know that in human cells the diploid number of chromosomes is 46 and the haploid
number is 23
– In humans diploid number of chromosomes is 46 and the haploid number is 23.
– Almost all human cells are diploid.
– Except for sex cells which are haploid as they come together to make a zygote.
91
Inheritance
3.28 understand that variation within a species can be genetic, environmental, or a
combination of both
– Genetic Variation:
– Gender
– Hair color
– Eye color
– Environmental and Genetic:
– Skin tone
– Height
– Intelligence
– Personality
92
Inheritance
3.29 understand that mutation is a rare, random change in genetic material that can be
inherited
– Mutation are random changes in the genetic material that can be passed from one
variation to the next.
3.30 describe the process of evolution by means of natural selection
– Natural selection occurs because the best species mutated to adapt the changing
environment will survive the most. The more they survive, the more likely they will
breed, and the more number of the species with exist.
– Those who do not adapt to the changing environment will die out because they will
not live long enough to breed.
– Evolution occurs by this concept, and the species change to conform and adapt to
changing environments.
93
Inheritance
3.31 understand that many mutations are harmful but some are neutral and a few are
beneficial
– Some mutations are harmful, some are neutral and some are beneficial and give the
organisms an advantage.
3.32 understand that resistance to antibiotics can increase in bacterial populations, and
appreciate how such an increase can lead to infections being difficult to control
– Bacteria can mutate and cause an increase in resistance towards antibiotics. These
populations multiply quickly and can be hard to control because of their immunity
towards antibiotics.
94
Inheritance
3.33 understand that the incidence of mutations can be increased by exposure to
ionizing radiation (for example gamma rays, X-rays and ultraviolet rays) and some
chemical mutagens (for example chemicals in tobacco).
– Mutation can be increased by exposure to:
– Ionizing radiation: gamma rays, x-rays, ultraviolet rays
– Chemical mutagens: tobacco
– Cell mutations such as cancer can develop.
95
Ecology and the environment
–
–
–
–
The organism in the environment
Feeding relationships
Cycles within ecosystems
Human influences on the environment
96
The organism in the environment
4.1 understand the terms population, community, habitat and ecosystem
– Population is all of the organisms of a particular species living in an ecosystem at a
particular time.
– Community is all of the populations of living organisms living in an ecosystem at a
particular time.
– Habitat is the place where specific live – their home.
– Ecosystem is a distinct, self-supporting system of organisms interacting with each
other and with their physical environment.
4.2 explain how quadrats can be used to estimate the population size of an organism in
two different areas
– Refer to experiment section
4.3 explain how quadrats can be used to sample the distribution of organisms in their
habitats.
– Refer to experiment section
97
Feeding relationships
4.4 explain the names given to different trophic levels to include producers, primary,
secondary and tertiary consumers and decomposers
– Producers produce food by photosynthesis.
– Consumers consume plants or other animals to get energy.
– Decomposers are organisms that break down and decompose dead material to
recycle nutrients.
4.5 understand the concepts of food chains, food webs, pyramids of number, pyramids of
biomass and pyramids of energy transfer
– Food chains
– Grass  grasshopper  lizard
– Always starts with the producer, then those who feeds on them and so on.
– Pyramids of numbers represent the numbers of organisms at each trophic level.
– Pyramids of biomass represent the total biomass of organisms at each trophic level.
98
Feeding relationships
–
Pyramid of numbers and biomass for food chain:
– Oak tree  aphids  ladybirds  birds
– From bottom to top, oak tree to birds.
4.6 understand the transfer of substances and of energy along a food chain
– Energy that is used for growth of the organism is transferred onto the next trophic
level.
4.7 explain why only about 10% of energy is transferred from one trophic level to the
next.
– Most of the energy is used for processes such as movement, reproduction.
99
Cycles within ecosystems
4.8 describe the stages in the water cycle, including evaporation, transpiration,
condensation and precipitation
– Evaporation from bodies of water (lakes, oceans).
– Transpiration from water absorbed by plants.
– Precipitation (rain) occurs after water vapor condenses.
100
Cycles within ecosystems
4.9 describe the stages in the carbon cycle, including respiration, photosynthesis,
decomposition and combustion
– Photosynthesis creates plants from carbon dioxide in the atmosphere and oceans.
The plants respire which return carbon dioxide into the atmosphere.
– After these plants die, decomposers turn it back into carbon dioxide in the
atmosphere and oceans.
– Animals can consume these plants and respire it back into the atmosphere, or they
can die and decomposers turn it back into carbon dioxide in the atmosphere and
oceans.
– Animals and plants can also be fossilized after million of years, turning them into
fossil fuels and through combustion being turned back into carbon dioxide.
101
Cycles within ecosystems
4.10 describe the stages in the nitrogen cycle, including the roles of nitrogen fixing
bacteria, decomposers, nitrifying bacteria and denitrifying bacteria (specific names
of bacteria are not required)
– Nitrogen fixation using nitrogen fixing bacteria:
– Nitrogen  Ammonia
– Nitrogen fixing bacteria are found in root nodules of leguminous plants.
– Denitrification using denitrifying bacteria:
– Nitrate  Nitrogen
– Decay using decomposers:
– Nitrogen Compounds (Urea, DNA, Protein)  Ammonia
– Nitrification using nitrifying bacteria:
– Ammonia  Nitrite  Nitrate
102
Cycles within ecosystems
103
Human influences on the
environment
4.11 understand the biological consequences of pollution of air by sulfur dioxide and by
carbon monoxide
– Sulfur dioxide is produced when fossil fuels are combusted.
– Sulfur dioxide + water  sulfuric acid (acid rain)
– The effects of this are:
– Damaged, sickly plants with stunted growth.
– Damaged buildings.
– Makes aqueous environments too acidic to be habitable.
– Carbon monoxide gas is formed in the incomplete combustion of fuels.
– It combines with hemoglobin in blood and takes the space of oxygen.
– The respiratory system is impaired if oxygen is not carried properly.
104
Human influences on the
environment
4.12 understand that water vapor, carbon dioxide, nitrous oxide, methane and CFCs are
greenhouse gases
– Greenhouse gases are: Water vapor, carbon dioxide, nitrous oxide, methane and
CFCs.
– These gases trap heat around the surface of the earth and are needed to keep the
planet warm for life.
4.13 understand how human activities contribute to greenhouse gases
– Carbon dioxide is made through combustion of fossil fuels.
– Refrigeration / solvents are the sources of CFC.
– CFCs break down the ozone layer.
– Farming cows causes a significant source of methane.
105
Human influences on the
environment
4.14 understand how an increase in greenhouse gases results in an enhanced
greenhouse effect and that this may lead to global warming and its consequences
– An enhanced greenhouse effect may lead to global warming.
– Global warming causes various consequences:
– Sea levels rising
– Changes in weather
– Changes in rainfall patterns
– Destruction of habitat
106
Human influences on the
environment
4.15 understand the biological consequences of pollution of water by sewage,
including increases in the number of micro-organisms causing depletion of
oxygen
– Sewage pollution results in many more microorganisms that decompose the sewage.
This uses up the oxygen in the water so that animals cannot survive it.
4.16 understand that eutrophication can result from leached minerals from fertilizer
– An excess of nutrients run off into a body of water.
– Growth of plants such as algae and duckweed are fueled by the nitrates.
– The plants flourish, blocking the sunlight, preventing the photosynthesis of subsurface plants. (Lower oxygen production)
– Algae and other plants begin to decay, further lowering the oxygen level. (Using up
oxygen)
– The pond is now inhabitable due to the low level of oxygen, all life forms diminish.
107
Human influences on the
environment
108
Human influences on the
environment
4.17 understand the effects of deforestation, including leaching, soil erosion, disturbance
of the water cycle and of the balance in atmospheric oxygen and carbon dioxide
– The soil is exposed to the sun, which leaches it of minerals
– The soil erodes because it is exposed to rain and wind.
– The lack of trees disturb the water cycle because transpiration stops occurring.
– Less oxygen and more carbon dioxide because photosynthesis is not occurring.
– The combustion of trees also contributes to rising carbon dioxide levels.
109
Use of biological resources
–
–
–
–
Food production
Selective breeding
Genetic modification (genetic engineering)
Cloning
110
Food production
5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of
certain crops
– The glass or polythene material in glasshouses and polythene tunnels gives a
greenhouse effect.
– It warms up the growing area so that photosynthesis can take place as fast as
possible.
– Carbon dioxide levels can also be controlled to speed up the rate of photosynthesis.
5.2 understand the effects on crop yield of increased carbon dioxide and increased
temperature in glasshouses
– Increase temperature  Increase yield
– Increase carbon dioxide levels  Increase yield
5.3 understand the use of fertilizer to increase crop yield
– Fertilizer places an excess of nitrates and minerals in the soil to make sure plants
have all the nutrients they need to grow as quickly as possible.
111
Food production
5.4 understand the reasons for pest control and the advantages and disadvantages of
using pesticides and biological control with crop plants
– Advantages:
– Very effective
– Disadvantages:
– May kill other organisms
– Pests can become resistant
– Pesticides cause environmental damage
– Very expensive
– Only reduces pests to an amount where they don’t cause significant damage.
112
Food production
5.5 understand the role of yeast in the production of beer
– When yeast respires anaerobically it produces ethanol, the chemical which acts as a
drug in alcoholic drinks.
5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in
different conditions
– Refer to experiment section
5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt
– The bacteria lactobacillus converts the lactose in the milk to lactic acid. This makes
the milk acidic and sour, which causes the protein to coagulate and making a low
viscosity mixture.
113
Food production
5.8 interpret and label a diagram of an industrial fermenter and explain the need to
provide suitable conditions in the fermenter, including aseptic precautions,
nutrients, optimum temperature and pH, oxygenation and agitation, for the growth
of micro-organisms
– Aseptic conditions are needed so that only the microorganisms that are wanted grow
in the culture.
– Nutrients, optimum temperature, pH are controlled to make sure the microorganisms
can grow and respire without being limited and work at an optimum environment.
– Oxygen and carbon dioxide levels are controlled because some organisms respire
aerobically.
114
Food production
115
Food production
5.9 explain the methods which are used to farm large numbers of fish to provide a source
of protein, including maintenance of water quality, control of intraspecific and interspecific
predation, control of disease, removal of waste products, quality and frequency of feeding
and the use of selective breeding.
– Fish are kept in large enclosures so the water quality can be controlled.
– Other types of fish are kept out of the enclosures to avoid interspecific competition.
– The numbers of fish are carefully controlled to avoid intraspecific competition.
– The quality of the food and the frequency of the feeding are controlled to maximize
speed of growth.
– Selective breeding is also used for this purpose.
– There are problems:
– Disease can spread quickly
– Waste from the fish can cause water pollution, including eutrophication.
– Wild fish stocks are being depleted.
116
Selective breeding
5.10 understand that plants with desired characteristics can be developed by selective
breeding
– Desired characteristics:
– Resistance to disease
– Heavy cropping
– Survival in difficult conditions
– Selective breeding is used to breed these plants together so they can pass on
desirable characteristics (alleles) to their offspring.
5.11 understand that animals with desired characteristics can be developed by selective
breeding.
– Desired characteristics:
– Heavier yields of milk, meat or eggs
– Producing more offspring
– Resistance to disease and parasites
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Genetic modification
5.12 describe the use of restriction enzymes to cut DNA at specific sites and ligase
enzymes to join pieces of DNA together
– To produce a recombinant DNA:
– Enzymes known as restriction enzymes cut out the gene from the donor
chromosome. They also cut the space for the new DNA to fit in.
– Enzymes known as ligase enzymes stick the gene into the DNA of another
organism.
5.13 describe how plasmids and viruses can act as vectors, which take up pieces of
DNA, then insert this recombinant DNA into other cells
– This new DNA sample is normally in plasmids or viruses.
– The recombinant DNA is inserted into other cells to make a transgenic organism.
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Genetic modification
119
Genetic modification
5.14 understand that large amounts of human insulin can be manufactured from
genetically modified bacteria that are grown in a fermenter
– Transgenic bacteria that have had a human insulin added to their DNA can make
human insulin, which is used to treat people with diabetes.
5.15 evaluate the potential for using genetically modified plants to improve food
production (illustrated by plants with improved resistance to pests)
– Advantages:
– Resistance to weed killers, frost, pests, disease
– Contain more vitamins or other nutrients
– Produce human antibodies or antigens
– To tolerate harsh environments
– Problems:
– Nutritionally enriched crops are expensive
– Genetically modified organisms interbreeding with wild organisms
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Genetic modification
5.16 understand that the term ‘transgenic’ means the transfer of genetic material
from one species to a different species.
– A transgenic organism is one that has had genetic material transferred into it from
another species.
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Cloning
5.17 describe the process of micropropagation (tissue culture) in which small pieces of
plants (explants) are grown in vitro using nutrient media
– Micropropagation involves taking tiny amounts of tissue from a plant (explants) that
are grown in special nutrient media.
– The plant tissue is supplied with hormones and minerals it needs to produce large
numbers of shoots.
– These are transferred to a different medium with hormones that cause the growth of
roots.
– The tiny plants are then transferred to compost in a greenhouse until they become
established plants.
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Cloning
5.18 understand how micropropagation can be used to produce commercial quantities of
identical plants (clones) with desirable characteristics
– Large numbers of genetically identical plants can be produced rapidly.
– Species that are hard to grow can be propagated.
– Plants can be produced at any time of the year.
– Tiny plants can be stored.
– Easy to produce genetically modified plants.
– However, there are certain disadvantages:
– All plants are genetically identical so they could all be vulnerable to the same
disease or change in conditions.
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Cloning
5.19 describe the stages in the production of cloned mammals involving the introduction
of a diploid nucleus from a mature cell into an enucleated egg cell, illustrated by Dolly the
sheep
– Taking the diploid nucleus of the udder cell of a mature sheep and placing it in the
egg cell of another sheep from which the nucleus has been removed.
– A tiny electric shock initiates the cell development and division.
– The cell develops into an early embryo and then is transferred into the uterus of a
foster mother where the embryo grew and developed into a sheep.
– The sheep is identical to the one from which the nucleus was taken from.
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Cloning
125
Cloning
5.20 evaluate the potential for using cloned transgenic animals, for example to
produce commercial quantities of human antibodies or organs for transplantation.
– Genetically modified animals can:
– Secrete desired protein in their milk
– Used to develop organs that could be used in human transplants
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Experiments
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2.11 describe experiments to investigate how enzyme activity can be affected by
changes in temperature.
2.16 describe experiments to investigate diffusion and osmosis using living and nonliving systems.
2.22 describe experiments to investigate photosynthesis, showing the evolution of
oxygen from a water plant, the production of starch and the requirements of light,
carbon dioxide and chlorophyll
2.32 describe an experiment to investigate the energy content in a food sample.
2.37 describe experiments to investigate the evolution of carbon dioxide and heat
from respiring seeds or other suitable living organisms.
2.43 describe experiments to investigate the effect of light on net gas exchange from
a leaf, using hydrogen-carbonate indicator
2.48 describe experiments to investigate the effect of exercise on breathing in
humans
2.56 describe experiments to investigate the role of environmental factors in
determining the rate of transpiration from a leafy shoot
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Experiments
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4.2 explain how quadrats can be used to estimate the population size of an organism
in two different areas
4.3 explain how quadrats can be used to sample the distribution of organisms in their
habitats.
5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in
different conditions
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Criteria
Examiners are looking for:
– Control experiment
– Organism name
– Repetition
– Measurement
– Standard
Make sure to specify units.
– Independent Variable
– Range (5)
– Control Experiment
– Organism
– Repeats (5)
– Dependent Variable
– Control Variable (3)
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Enzymes
2.11 describe experiments to investigate how enzyme activity can be affected by changes
in temperature.
Investigate the effect of temperature on the enzyme amylase using starch and
iodine.
1.
2.
3.
4.
5.
6.
7.
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Spots of iodine are placed in depressions in a spotting tile.
Starch is placed in one boiling tube in a beaker filled with room temperature water.
Amylase is placed in another boiling tube in a beaker fill with room temperature water.
Pour the amylase solution into the starch.
Use a pipette to remove a dose every thirty seconds from the mixture and drop onto the iodine
solution.
The lighter the color of iodine, the more starch has been used up. Record the color of the iodine.
Repeat experiment with different temperatures.
Independent Variable: Temperature (25, 35, 45, 55, 65 0C)
Control Variables: Amount of starch (5 ml), Amount of amylase (5 ml), Time between each sample
taken (30s), Amount of each sample taken.
Dependent Variable: Color of the iodine.
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Diffusion & Osmosis
2.16 describe experiments to investigate diffusion and osmosis using living and non-living
systems.
Demonstrate diffusion using agar blocks dyed with potassium permanganate.
1.
2.
3.
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Prepare 3 cubes of agar blocks dyed with potassium permanganate of side lengths 2 cm, 1 cm,
0.5 cm.
Drop the 3 cubes into a beaker of dilute hydrochloric acid.
Take the time for when each of the blocks turn colorless.
Independent Variable: Volume of agar blocks (2, 1, 0.5 cm)
Control Variables: Temperature, Concentration of acid, Amount of potassium permanganate in
each block, Density of each block, Volume of acid
Dependent Variable: Time it takes for block to turn colorless (s).
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Diffusion & Osmosis
Demonstrate osmosis using living cells such as potato tissue.
1.
2.
3.
4.
5.
6.
7.
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Cut 6 identical 4 cm length cores of potato with the cork borer.
Measure the mass of the potato cores in grams.
Dissolve 1 / 2 / 3 / 4 grams of sugar in 25 ml of water to prepare the four solutions in the test
tubes.
Prepare a test tube of pure distilled water.
Prepare an empty test tube.
Place the potato cores into the 6 test tubes.
Start the timer and run the experiment for 24 hours.
Independent Variable: Sugar content in the solution.
Control Variable: Surface area of the potato chip before osmosis, Volume of acid, Temperature of
solution, Time exposed to solution.
Dependent Variable: Percentage mass change of potato core.
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Photosynthesis
2.22 describe experiments to investigate photosynthesis, showing the evolution of
oxygen from a water plant, the production of starch and the requirements of light, carbon
dioxide and chlorophyll
Investigate the effect of factors on the rate of photosynthesis using aquatic plants
such as pondweed and the evolution of oxygen.
1.
2.
3.
4.
Place pondweed in a boiling tube.
Place a lamp 2 cm from the boiling tube.
Count the number of bubbles evolved from the pondweed in 1 minute.
Repeat experiment with the lamp 4 / 6 / 8 / 10 cm away from the pondweed.
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Independent Variable: Distance of lamp from the pondweed.
Control Variable: Strength of lamp, Temperature, Amount of light in the environment, Amount of
carbon dioxide in the room.
Dependent Variable: Number of bubbles per minute.
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Photosynthesis
Demonstrate the requirement of light, carbon dioxide or chlorophyll using the
presence of starch in the leaf.
1.
2.
3.
4.
5.
6.
7.
Begin with a de-starched leaf, which has not been exposed to light in 24 hours.
Eliminate one of the requirements.
– To show that light is needed, cover part of a leaf so that it is not exposed to light.
– To show that chlorophyll is needed, use a variegated (green and white) leaf.
– To show that carbon dioxide is needed, remove carbon dioxide from the air surround the
plant using soda lime.
Kill the leaf by placing it in hot water for 30 seconds.
Remove the color (chlorophyll) by placing it in boiling ethanol for a few minutes.
Wash the leaf with cold water to clean and soften it, then lay it onto a tile.
Cover the leaf with a few drops of iodine.
The sections of the leaf where starch is present will turn dark blue / black.
No variables in a demonstration.
134
Energy content in food
2.32 describe an experiment to investigate the energy content in a food sample.
Measure the energy content in a food sample.
1.
2.
3.
4.
5.
6.
7.
Weigh the food using a scale.
Place 20 cm3 of water in a test tube and mount it on a stand. Measure the temperature.
Spear the food with a needle and place it on top of a Bunsen burner.
Allow the food to catch fire and when the food is alight, place it under the water.
Keep the food there and relight it if necessary until the food will no longer burn.
Measure the final temperature of the water.
Find the energy content using this calculation:
– Energy = change in temperature X 20 X 4.2 / mas of food
No variables in a measurement.
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Respiration
2.37 describe experiments to investigate the evolution of carbon dioxide and heat from
respiring seeds or other suitable living organisms.
Demonstrate the evolution of carbon dioxide from living organisms with hydrogencarbonate indicator.
1.
2.
3.
4.
Fill a boiling tube with hydrogen-carbonate indicator.
Place small organisms such as woodlice or maggots on a gauze platform above the indicator.
Insert a bung to prevent the loss of gases.
Hydrogen-carbonate indicator turns from orange to yellow when carbon dioxide is present, look for
the yellow color to show that carbon dioxide is there.
No variables in a demonstration.
136
Respiration
Demonstrate the evolution of heat from respiring seeds with a vacuum flask.
1.
2.
3.
4.
5.
6.
Soak peas in water for 24 hours to initiate germination.
A second batch of peas are boiled to kill them.
Place each batch of peas in a inverted vacuum flask with a thermometer and cotton wool holding
in.
The apparatus is left for a couple of days.
Measure the temperature in both the flasks.
The live batch should be hotter as respiration evolves heat.
No variables in a demonstration.
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Gas exchange
2.43 describe experiments to investigate the effect of light on net gas exchange from a
leaf, using hydrogen-carbonate indicator
Investigate the effect of light on net gas exchange from a leaf, using hydrogencarbonate indicator.
1.
2.
3.
4.
5.
6.
7.
8.
10 cm3 of hydrogen carbonate indicator is placed in the bottom of 3 test tubes.
Place a leaf in each test tube and seal it off with a bung.
Place one tube in bright light.
Place one tube in dim light.
Place one tube in darkness.
Leave the experiment for a few hours.
Record the color of the indicators.
Neutral amount of carbon dioxide is red, less than average is purple, more than average is yellow
/ orange.
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–
Independent Variable: Intensity of light.
Control Variables: Temperature, Size of leaf, Amount of chlorophyll in leaf, Amount of carbon
dioxide.
Dependent Variable: Color of indicator.
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138
Ventilation
2.48 describe experiments to investigate the effect of exercise on breathing in humans
Investigate the effect of exercise on breathing rate in humans.
1.
2.
3.
4.
Measure initial breaths per minute at rest.
Run 100 m at 10 km/h on the treadmill.
Measure breaths per minute.
Repeat experiment with 200 / 300 / 400 / 500 m runs.
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Independent Variable: Length of run.
Control Variables: Temperature, Incline of run, Clothing worn, Same person, Same environmental
conditions (wind speed).
Dependent Variable: Breaths per minute.
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139
Transpiration
2.56 describe experiments to investigate the role of environmental factors in determining
the rate of transpiration from a leafy shoot
Investigate the effects of environmental factors on the rate of transpiration from a
leafy shoot using a potometer.
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Set up a potometer by inserting the end of a shoot into a capillary tube and inserting the capillary
tube into water. Remember to place the entire apparatus in the water first to remove all the air
bubbles.
Expose the apparatus to different temperatures OR light intensities.
Measure how fast bubbles move up the capillary tube.
Independent Variable: Temperature OR Light intensity.
Control Variable: Temperature OR Light intensity, Wind speed, Humidity, Size of plant, Species of
plant.
Dependent Variable: Speed of flow of water.
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Population
4.2 explain how quadrats can be used to estimate the population size of an organism in
two different areas
1.
2.
3.
4.
5.
6.
In area A, place a quadrat on the floor randomly.
Count the numbers of each plant species present within the quadrat.
Repeat steps 1 – 2 for 10 times in area A.
Add up the numbers of each plant species within the entire area.
Repeat steps 1 – 3 for area B.
Compare the two areas in a bar chart.
No variables in explanation.
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Distribution
4.3 explain how quadrats can be used to sample the distribution of organisms in their
habitats.
1.
2.
3.
4.
5.
Place a quadrat randomly on the ground.
Count how many of the species there is within the quadrat.
Repeat 10 times.
Find the average out of the 10 times of the species within the quadrat.
Use the average to calculate how many there is in the entire area.
No variables in explanation.
142
Yeast
5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in
different conditions
Demonstrate the production of carbon dioxide by yeast.
1.
2.
3.
4.
5.
6.
Boil water in a boiling tube to drive off oxygen in the water.
Add a small amount of sugar and yeast to the water and stir it.
Add a thin layer of paraffin onto the top of the water to ensure no oxygen goes into the mixture.
Seal the boiling tube with a bung which has a hole in it and connect the hole to a test tube with
limewater.
Leave the apparatus for a few hours.
If carbon dioxide has been evolved, the limewater should have turned milky, cloudy white color.
No variables in demonstration.
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