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0610 IGCSE® Biology Ultimate Revision Notes

Ch1 Classification
Ch2 Cells
Ch3 Movement in and out of the cell
Ch4 The chemicals of life
Ch5 Enzymes
Ch6 Plant nutrition
Ch7 Animal nutrition
Ch8 Transport in plants
Ch9 Transport in animals
Ch10 Pathogens and immunity
Ch11 Respiration
Ch12 Excretion
Ch13 Coordination and Response
Ch14 Homeostasis
Ch15 Drugs
Ch16 Reproduction in plants
Ch17 Reproduction in human
Ch18 Inheritance
Ch19 Variation and natural selection
Ch20 Ecology

Ch21 Biotechnology
Ch22 Humans and the environment
Questions type
Practicals

Ch1 Classification
Characteristics of living things
Movement
An action by an organism or part of it
A change in position or place
Respiration
Chemical reactions in cells
Break down nutrient molecules e
...
glucose
To release energy for metabolism
Sensitivity
The ability to detect or sense stimuli, both internal and external
To make appropriate responses
Growth
Permanent increase
Size and dry mass
By increase in cell number / or & size
Reproduction
Make more of the same kind of organism
Excretion
Removal from organisms
Metabolic wastes
Toxic materials
Substances in excess of requirements
Nutrition
Taking in of materials
For energy, growth and development
Classification techniques
Morphology: overall shape and form of their bodies
Anatomy: detailed body structure
DNA base sequence / amino acid sequence in proteins similarities compared with other species
The classification system
Kingdom --> phylum --> class --> order --> family --> genus --> species
Species
A group of organisms
Can reproduce
Produce fertile offspring
Binomial naming system
Genus (G
...
g
...
now() < optimum_temperature:
while temperature_increase == True:
kinetic_energy += n

speed_of_particle += n

frequency_of_collision += n
energy_of_bumping += n

enzyme_activity = rate_of_reaction += n

elif temperature
...
g
...

Energy need factors
Age
Sex
Job
Pregnancy
Disease
Body mass
Extra energy -->fat
Fibre
Harder, less digestible to make muscle work harder
Stronger peristalsis
Contraction & relaxation of muscles to make food move along
Back of food, circular muscles contract and longitudinal muscles relax
Prevent constipation
In plant foods
Rich in outer husk of cereal grains
Fat and heart diseases
Saturated fat and cholesterol deposits inside arteries
Making them stiffer and narrower, atherosclerosis
Not enough blood can get through coronary arteries
Not enough oxygen supplied to heart muscle cells
Cardiac muscles have insufficient oxygen to respire to obtain energy for contraction
Cause heart attack
CHD induced
May cause blood clots, heart attack
Obesity
Being very fat
Increase risk of heart disease, strokes and diabetes, as well as joint problems
Treatment
Weight control
Balanced diet

Regular exercise
Vitamin
C
From citrus fruits (oranges, lime) and raw vegetables
To make collagen
Keep tissues in good repair
Deficiency diseases
Scurvy
Joint pain, muscle pain
Gum bleeding
D
From butter, egg yolk, made by skin using sunlight
Help to absorb Ca2+ for making bones and teeth
Deficiency diseases
Rickets
Soft and deformed bones
Minerals
Ca2+
From milk and other dairy products, bread
For bones and teeth
For blood clotting
Deficiency diseases
Brittle bones and teeth
Poor blood clotting
Fe

2/3+

From liver, red meat, egg yolk, dark green vegetables
To make Hb
Deficiency diseases
Anaemia
Not enough erythrocytes
Malnutrition
Unbalanced diet
Kwashiorkor
Lack of protein
Swollen abdomen
Marasmus
Severe shortage of energy due to lack of carbohydrate, fat and protein
Looks emaciated
Vomiting
Susceptible to diseases
Shared symptoms

Diarrhoea
Low body mass / weight loss
Poor growth
Irritability / tiredness
Wastage of muscles
Dry skin / brittle nails
Brittle hair / change of hair colour
Mechanical digestion
Breakdown of food
Into smaller pieces
Without chemical change to food molecules
Using teeth / muscle
E
...
mastication, churning motion & emulsification
To increase SA for chemical digestion
Making swallowing easier
Chemical digestion
Breakdown of large insoluble food molecules
Into small soluble ones
Enzymes involved
Easier to be absorbed
Ingestion
Taking of substances into the body through mouth
Gives bolus to oesophagus
Mastication
Biting off pieces of food
Chop, crush or grind into smaller pieces
To give larger SA
Easier for enzymes to work on
Dissolve soluble parts
Tooth
Crown
Enamel
Hardest
Most outer layer
Dentine
Inside the enamel
Quite hard
Living
Pulp cavity

Contains nerves and blood vessels
Supply dentine with food and oxygen
Root
Covered with cement
Has fibres growing out to attach jawbone
Teeth
Incisors
Sharp-edged, chisel-shaped
At the front of mouth
Biting off food
Canines
Pointed
Tear food
Premolars & molars
Have wide surface and cusps
Chew / grind food
Dental decay
Gum diseases
A biofilm of bacteria forming plaque
If not removed, form hard tartar
Bacteria infect gums
Gums swell, bleed
Bacteria work down around the roots
Tooth loosened
Tooth decay
Sugar remains on teeth
Bacteria in plaque produce acid when respire on food molecules
Acid dissolves enamel
Into dentine
Infection
Decay reaches nerve endings in pulp cavity causing pain
Prevention
Control sugar intake
Fluoride toothpaste
Regular tooth brushing
Regularly visit dentists
Alimentary canal
Long tube from mouth to anus
Mouth
Tongue
Mix food with saliva

Food to bolus
Saliva
Water to dissolve food substances
Mucus helps the chewed food to bind and form bolus
And lubricates
Amylase to digest starch to maltose
Oesophagus
Epiglottis shuts it
Oesophagal sphincter stops bolus into stomach
Stomach
Muscular wall to churn bolus to mix it with gastric juice
Goblet cells to secrete mucus
Prevent damage from pepsin & HCl(aq)
Reduce physical damage
Reduce chance of infection by pathogens
Chief cells to secrete pepsinogen waiting to be activated by HCl(aq)
Parietal cells to secrete HCl(aq)
To activate pepsin
Provide optimal pH for pepsin
Denature food proteins
Kill microorganisms in food by denaturing their proteins
Bolus to chyme
Pyloric sphincter stops chyme into duodenum
In young mammals
Rennin to coagulate milk
Stay longer in stomach
Digest more complete
Small intestine
Duodenum --> jejunum --> ileum
About 5m to give time for complete digestion
Duodenum
Have pancreatic juice
Secreted by pancreas
Flow in through pancreatic duct
Amylase, trypsin, lipase
HCO3- to neutralise chyme
Have bile
Secreted by liver
Stored in gall bladder
Flow in through bile duct
Yellow-green colour caused by bile pigments, old Hb about to be removed
Being alkaline to neutralise chyme
Bile salts to emulsify fats
Breaking large fat globules into smaller ones

To increase SA
For lipase
Speeds up fat digestion
Villi
Projections in small intestine to increase SA
Cells have microvilli to increase SA
Make enzymes
Maltase, sucrase, lactase, peptidase and lipase
Good blood supply to absorb food molecules towards hepatic portal vein to liver
Absorbed via diffusion & active transport
Lacteal to absorb fat towards lymphatic vessels
One-cell thick epithelium for easy transport
Epithelial cells have carrier proteins and mitochondria for active transport
Absorption
Movement of food molecules and ions
Through wall of small intestine
Into the blood
Assimilation
Movement of digested food molecules into body cells
Used and becoming part of the cells
Cholera
Caused by Vibrio cholerae
Transmitted by contaminated food & water
Attach to epithelium of small intestine
Secrete toxin choleragen
Stimulate cells lining the intestine to secrete ClDecrease ψ in lumen of small intestine
Water moves out the blood
Loss of water and salts in watery faeces
Treated by oral rehydration therapy
Dilute salt and sugar solution to replace lost water and nutrients
And antibiotics

Ch8 Transport in plants
Xylem
No cytoplasm, hollow to reduce resistance to water flow
Elongated and no end walls to allow water transport in a continuous column
Thickening of cell walls by waterproof lignin in cell walls to support the plant, prevent collapsing,
prevent leakage of water or breaking of the continuous column
Pits to allow water to move into surrounding cells laterally
To transport water and minerals
Phloem
Have sieve plates from end walls
Have companion cells
To transport organic nutrients e
...
sucrose & amino acids
Transpiration pathway
Active transport of ions create ψ gradient
Water enter root hair cells by osmosis creates root pressure
Soil solution --> cortex of roosts --> xylem in centre of roots
Stem --> leaf -->air
Cohesion / adhesion in continuous column of water
Up xylem in stem --> leaf
Evaporation of water from cell walls to air space
Diffusion of water vapour out of leaves to air through stomata
Loss of water creates transpiration pull, negative tension
Transpiration rate factors
Humidity
High humidity
Less steeper [] gradient of H2O(g)
Diffusion rate decreases
Evaporation rate decreases
Smaller transpiration pull
Temperature
High temperature KE of H2O molecules increases
Move quickly
Faster diffusion & evaporation
Larger transpiration pull
Wind speed
High wind
More steeper [] of H2O(g)
H2O diffuses and evaporates faster
Larger transpiration pull

Light intensity
Bright light
Open more stomata to allow CO2 to enter for more effective photosynthesis
Faster rate of diffusion of water

...

Translocation
The movement of organic nutrients including sucrose and amino acid
In phloem
Can in both directions
From source (regions of production / storage)
Photosynthetic leaves
Roots (tubers) of dormant plants
To sink (regions of utilisation in respiration or growth)
Roots (tubers) for storage
Flowers (nectaries)
New shoots

Ch9 Transport in animals
Double circulatory system
Blood passes through the heart twice
In one complete circuit
Pulmonary system + systemic system
Adv
Raise pressure / flow rate of oxygenated blood before sending it off to the rest of the body
Allows different pressure in different loops
Prevents mixing of oxygenated and deoxygenated blood
Higher metabolic rate
Allows animals to be large
Dis
High energy cost
Reasons for difference in thickness of walls
Ventricles vs atria
Ventricles need to pump blood out of the heart
Atria only need to receive blood
Thicker walls in ventricles
Left vs right ventricle
Right ventricle only pumps blood to the lungs, close to the heart
Left ventricle pumps blood all around the body
Require high pressure to overcome resistance
Thicker walls in left ventricle to contain more cardiac muscle
Factors of CHD
Smoking cigarettes: cigarette contains nicotine
Diet: high in salt, saturated fat, cholesterol
Obesity
Stress
Genes
Treatment of CHD
Statin to reduce cholesterol levels in blood
Aspirin to reduce the risk of blood clots forming inside blood vessels
Coronary bypass operation: damaged coronary artery replaced with a length of blood vessel from
another part of the body
Stent, a mesh tube to keep it open
Angioplasty: tiny balloon inflated by water to push artery open
Heart transplant: risk of rejection
Heart beat rate

Controlled by atrioventricular node in right atrium
In exercise
Demand for energy increases for muscle contraction
Respiration rate in muscle cells increases
D for O2 increases
[CO2] increases
Blood pH decreases
Chemoreceptors in medulla of brain senses decrease in pH of cerebrospinal fluid
Brains sends impulses to pacemaker and thoracic cavity
Adrenaline released also
Heart beat faster, breathing rate increases
So more oxygen and glucose transported to muscles and more CO2 to lungs
One heart beat
Atrial systole
Atria contract
Blood flows from atria to ventricles through AV valves
Valves in veins shut to prevent backflow to veins
Semilunar valves remain shut
Ventricular systole
Ventricles contract and pressurise blood
Blood flows from ventricles to pulmonary artery and aorta through semilunar valves
AV valves shut and pulled by tendons to prevent going up too far
Ventricular diastole
Atria and ventricles relax
Volume of atria and ventricles increase
Blood flows from veins to atria and veins through valve in veins and AV valves
Semilunar valves are pushed shut
Arteries
Thick and strong walls to withstand the high pressure
Elastic fibres to stretch and recoil with the force of blood to make blood flow smoother
Smooth muscles to allow vasodilation and vasoconstriction
Collagen fibres to prevent bursting
Small lumen to maintain blood pressure
No valves needed as force of heart beat keep blood flowing forwards
Veins
Thin walls as no need to withstand pressure, blood pressure lost
Large lumen to reduce resistance to blood flow
Valves to prevent backward of blood flow
Capillaries
One-cell thick wall

to allow efficient (short distance) exchange of materials through pores in the wall
no need to withstand blood pressure, pressure lost
Narrow lumen to bring blood contents closer to body tissues
Pores in wall
In large number
Large SA for diffusion
Naming body parts
Cranial: skull
Jugular: neck
Pulmonary: lung
Hepatic: liver
Mesenteric: intestine
Renal: kidney
Gastric: stomach
Blood plasma
As liquid medium in which cells and platelets can floats
Water
Nutrients e
...
glucose, amino acids and mineral ions
Hormones
CO2
Urea
Heat
Proteins e
...
antibodies, fibrinogen
Lipids
Erythrocytes (RBC)
Made in bone marrow
Contains Hb with Fe to carry oxygen
Lack nucleus to give more space for Hb
Biconcave shapes to increase SA:V to increase rate of O2 diffusion
Small size to squeeze through capillaries
Blood clotting
Platelets bump into rough edges of the cut
Soluble fibrinogen to insoluble fibrin, catalysed by thrombin
Form mesh, scab / harden
Trap blood contents / prevent bleeding
Prevent infection
Tissue fluid
Forms by substance leaking from blood, excluding erythrocytes and proteins
Surrounds all body cells

Supplies them with all their required nutrients including O2
Carries away waste products including CO2
Main site of homeostasis
Lymph
Contains leaked plasma contents from blood
Returned from lymphatic capillaries to larger lymphatic vessels to subclavian veins
Have valves to make sure one direction flow
Run by contraction of muscles
Lymph nodes
New leukocytes form
Can destroy bacteria and toxins

Ch10 Pathogens and immunity
Pathogens
Microorganism
Cause disease
May damage cells by living in them
Using up their resources
Producing toxins
Transmissible disease
The pathogen can be passed from one host to another
Direct contact (contagious diseases)
Infection
Entry of pathogen into the body
Host
The organism which pathogen lives and breeds
Transfusion of blood
Fungal disease e
...
athlete’s foot
Indirect transmission
Contaminated surfaces
Through the respiratory passage
Air droplets from the host
Food / water-borne
By a vector
Organism that carries a pathogen from one host to another
Mechanical barriers in body
Nasal hairs in nostrils to trap dusts carrying pathogens
Dead, cornified layer in skin containing keratin, difficult to penetrate
Blood clotting prevents entry of pathogens
Cilia sweep mucus to throat to be swallowed into stomach to kill pathogens by stomach acid
(mucus)
Ear wax
Chemical barriers in body
Mucus produced by goblet cells to trap pathogens
HCl(aq) secreted in stomach kills bacteria in food
Immune system in body
Phagocytes digest pathogens by phagocytosis
Lymphocytes produce antibodies in an immune response to fight against pathogens

Food hygiene
Keep own pathogens away from food
Wash hands before eating
Wear uniforms
Never cough or sneeze over food
Keep animals away from food
Covering food to separate food from flies, mice
Do not keep foods at rt for too long
Most bacteria grow fastest
Keep in fridge
Cook at high temperature
Keep raw meat away other foods
Personal hygiene
Washing skin regularly
Brushing teeth twice a day
Antibodies
Complementary shape to specific antigens
As antitoxins to prevent damage of toxins to body cells
Attach to flagella making bacteria less active, easier for phagocytes to engulf
Agglutination: clumping many bacteria reducing chance of spreading
Direct destruction: punch holes in bacterial walls, undergo ‘lysis’
Label on antigens, making it easier for phagocytes to recognise and engulf them
Vaccination (active immunity)
Injects harmless (dead / inactive / weakened) form of pathogens
Pathogens have specific antigens to be recognised as foreign by lymphocytes
Immune response stimulated
B-lymphocytes divide to form a clone of plasma cells by mitosis
Plasma cells produce antibodies
Memory cells also formed to give active / long-term immunity
By producing a large amount of antibodies in a short period of time after the real infection
Kill pathogens before any symptoms occur
Gives herd immunity
Time lag in immune response
Time for recognition
Time to produce a enough clone to make enough antibody
Active immunity
Antigens enter
An immune response occurs

Antibodies and memory cells produced
Long-term
Control of pandemic
Improvement in food hygiene
Intake boiled food and water
Sewage treatment
Monitor, identify and isolate infected individuals

Ch11 Respiration
Requirement of energy
Muscle contraction for movement
Anabolic reaction e
...
protein synthesis
Cell division to repair and grow
Active transport
Transmit nerve impulses
Sensitivity
Generate heat for thermal homeostasis
(transport in phloem)
Anaerobic respiration
Yeast and plants
C6H12O6 ----> 2C2H5OH + 2CO2
Animals
C6H12O6 ----> 2C3H6O3
Aerobic respiration

Anaerobic respiration

Uses O2

Does not use O2

No alcohol / lactic acid

Alcohol in yeasts & plants, lactic acid in muscles

Large amount of energy released

Much less amount of energy released

CO2 made

CO2 made only in yeasts and plants

Adaptation of nose to breathing
Nasal cavity is separated from oral cavity by palate to allow breathing during eating
Nasal hairs in nostrils trap dust particles in the air
On surface of turbinal bones
Goblet cells secrete mucus containing water and mucus to moisten and warm air
Cilia move mucus to the back of the throat
Adaptation of trachea to breathing
Supported by C-shaped cartilages
To prevent collapsing
To keep it open to allow free flow of air
To give it flexibility
Goblet cells and ciliated cells also present
At top
Epiglottis closes trachea when bolus touches palates and is about to be swallowed
Larynx containing vocal cords make sounds
Adaptation of alveoli to gas exchange
Thin walls to allow fast diffusion of O2 molecules to blood

Good blood supply from pulmonary artery and to pulmonary vein
Maintain [] gradient of O2 and CO2
Keep diffusion fast
Large SA due to large numbers to allow faster diffusion
Good supply of O2 by breathing movements
Steep [O2] gradient
Surfactant to reduce surface tension
Elastic fibres to stretch and recoil during breathing
Inspiration / Expiration
External & intercostal muscle
Diaphragm
Rib cage & sternum
Volume of thoracic cavity & pressure
Suck / squeeze air in / out
Oxygen debt
Lots of energy in short time
Increased heart beat and breathing rate still doesn’t meet high demand for energy
Insufficient oxygen facing higher demand for oxygen by high demand for aerobic respiration
Anaerobic respiration
Lactic acid production —> muscle fatigue
How oxygen debt is paid
Continued fast heart beat & breathing rate
Enough oxygen provided assisted by increased breathing rate
Lactic acid diffuses from muscle cells to the blood
Lactic acid to liver transported in blood assisted by increased blood flow
Oxidised / respired aerobically
To carbon dioxide and water

Ch12 Excretion
e
...
s of excretion
CO2 produced during respiration excreted by breathing
Excess water and salts removed by kidneys
Old Hb broken down into bile pigments and excreted from liver to faeces
Urea from deamination excreted by kidneys in urine
Metabolism of amino acid in liver
From hepatic portal vein
Make plasma proteins e
...
fibrinogen
Deamination
Removal of amine group
Nitrogen-containing part forms urea (or ammonia / uric acid)
Rest of carbon-containing part is turned into carbohydrate and respired for energy / stored
Functions of liver
Deamination
Synthesis of plasma proteins
Regulation of blood glucose in response to glucagon & insulin
Store glycogen
Production of bile
Breaking down of old RBC, store Fe and excrete remains of Hb as bile pigments
Breaking down of harmful substances e
...
alcohol
Stores vitamin A, B, D, E & K, K+
Production of cholesterol
Ultrafiltration
Renal artery --> afferent arteriole --> glomerulus --> efferent arteriole --> renal vein
Afferent arteriole is wider than efferent ~, high blood pressure squeeze blood in glomerulus (ball
of capillaries) against capillary walls
Small molecules can go through, large ones e
...
proteins are too big to go through the small holes
Reabsorption
Proximal convoluted tubule
Na+ is actively transported from tubule cells to blood, it then diffuses from the tubule lumen
to tubule cells
This creates energy for the co-transporter to reabsorb glucose, amino acids, vitamins and ClLoop of Henle
Descending limb has wall permeable to H2O, reabsorb it by osmosis
Ascending limb has wall impermeable to H2O
In lower part of ascending limb, Na+ & Cl- reabsorbed by diffusion due to great water loss
In higher part of ascending, Na+ & Cl- reabsorbed by active transport

Distal convoluted tubule
Na+ & Cl- actively pumped out of tubule and K+ & H+ in
Drugs and toxins enter tubule
Collecting duct
Water reabsorbed by osmosis
Osmoregulation
Volume of sweat / water loss
Intake of water
Ref
...
g
...
dilation)
Circular muscles contract
Radial muscles relax
They work antagonistically
Pupil gets smaller
Is unconscious
To prevent damage to the retina that could be caused by high light intensity
Lens
Focus light onto retina
Accommodation

E
...
closer object
Ciliary muscle contracts
Suspensory ligaments are loosened (r

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