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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
...
g
...
g
...
g
...
g
...
g
...
g
...
k
...
fertilisation to form a zygote
Seeds
Zygote --> embryo
Integuments of ovule --> testa, it is hard to stop damage and entry of pathogens
Placenta (join to the ovary) --> hilum
Radicle to grow into a root
Plummule to grow into a shoot
Cotyledons contain starch and protein
Water drawn out to be dormant to survive harsh conditions e
...
cold & drought
Germination
Water enters, seed swells, bursts the testa
Amylase and protease started working

Ch17 Reproduction in human
Male reproductive system
Testes: make sperm(atozoa)
Scrotum: surrounds testes outside the body, lower temperature for sperm production
Sperm duct / vas deferens: carry sperm from the testes to urethra
Prostate gland: at where sperm ducts join the urethra, to make a fluid which sperm swim in
Sperm cell
Acrosome: a vesicle containing enzymes to digest the jelly coat surrounding the egg cell
Nucleus: contains the haploid nucleus
Mitochondria: carry out aerobic respiration to release energy for swimming
Flagellum: produce swimming movements
Human fertilisation and embryo development
Ovulation
The released egg is caught in the funnel-shaped opening of the oviduct (Fallopian tube)
The funnel has cilia which waft the egg into oviduct
Peristalsis to move the egg in the oviduct
Sperm reaches the egg
Ejaculation: sperm are pushed out of penis into the vagina in semen
Sperm travel up through the cervix through the uterus and into the oviduct
One sperm has its head enters the egg after acrosome digest the jelly coat, leaving tail outside
Fertilisation: nuclei fuse to form zygote
The egg membrane becomes impermeable / hardens, other sperm die
Implantation
Fertilised zygote divides by mitosis to from an embryo, a ball of cells
The embryo reach the uterus and sinks into the endometrium
Cell specialisation to increase complexity
After 11 weeks of fertilisation, all organs are developed, embryo --> fetus
Later development to increase size
Uterus
Placenta
Connects the embryo to the uterus wall
Exchange substances between mother’s and embryo’s blood by diffusion
Wastes to mother’s blood
Nutrients to fetus’s blood
Wall of it separates fetus’s blood and mother’s blood
Umbilical cord
Joins the fetus to the placenta
Amniotic fluid surrounded by amniotic sac
Protects the embryo from mechanical damage by lubricating

Supports it
Maintains temperature
Provides sterile environment
Allows movement
Swallow of certain nutrients in fluid
Ante-natal care
Ca2+ in diet: to form the growing fetus’s bones
Fe2 / 3+ in diet: produce a lot of extra Hb
Extra carbohydrate: extra energy to move around heavier
Extra protein: to form growing fetus’s new cells
No smoking
Nicotine & CO can enter the baby’s blood
Increase risk of miscarriage
Cause the baby to grow more slowly
Lower birth weight
Fetus brain damage
Increased risk of lung infection in infants
Infants develop addiction
No alcohol
Vaccinated with rubella virus in puberty
Rubella can cross the placenta
Cause the baby to born with deaf or other disabilities
Birth
Labour
Strong muscles in the uterus wall start to contract
Cervix dilates
Vaginal wall stretch
Amniotic sac breaks
Amniotic fluid releases
Afterbirth
Placenta falls away from the uterus wall and passes out through the vagina
The umbilical cord is tied, cut and clamped and forms the baby’s navel
Adv of breast feeding
Contains antibody, passive immunity
Creates bonding with mother
No pathogens, less risk of infection
Cheap
Nutrient change with children development
No preparation / convenient
Easy to digest
Less risk of allergic effect

In body temperature
Adv of bottle feeding
Make life easier for mother
Help father to bond with the baby
No restriction on mother’s diet
Can add extra vitamins and minerals
Puberty
Boys
Brought by testosterone
Growth of facial and pubic hair
Breaking of the voice
Muscular development
Girls
Brought by oestrogen
Growth of pubic hair
Development of breast
Broadening of pelvic girdle

The menstrual cycle
1-5 days menstruation
Unfertilised egg is dead when it reaches the uterus
The endometrium disintegrates and is lost through the vagina
Lasts around 5 days
FSH released to develop follicle which releases oestrogen
5-14 days egg growth
Oestrogen inhibits FSH secretion
LH released
14 day ovulation
LH peaks causing ovulation
Too high concentration of oestrogen stimulates surge in FSH release
14-21 days corpus luteum
Progesterone secreted by corpus luteum to maintain endometrium
LH production is inhibited
21-28 days prepare for menstruation
Progesterone level falls
Corpus luteum degenerates
Corpus luteum
Forms from follicle
Secretes progesterone
If not fertilised

It doesn’t degenerate so quickly
Continues to secrete progesterone
Natural methods of birth control
Abstinence: mentally ineffective
Rhythm control
Predict menstrual cycle and avoid intercourse around ovulation, not reliable
Using body temperature monitoring & cervical mucus
Chemical methods
Spermicide
Not always reliable
Easy to use
Need to be used in combination with barriers
Sex hormones
Contains progesterone and oestrogen
Very effective
May forget to take it everyday
Side effects
IUD (intrauterine device)
Coil in uterus prevents implantation
No protection against STI
IUS (intrauterine system)
Slowly releases hormone to prevent implantation
Mechanical methods
Condom
Thin rubber covering over penis to prevent sperm entering the vagina
Safe & easy
Prevent STI
Femidom
Thin sheath lines the vagina to prevent entry of sperm
Diaphragm / cap
Circular slightly domed piece of rubber inserted into the vagina and covers the cervix
To stop sperm enter
Surgical methods
In man (vasectomy)
Sperm ducts are cut / tied
Stopping sperm from travelling from the testes to the penis
In woman (female sterilisation)
Oviducts are cut / tied
Stopping eggs from travelling down the oviducts
Effective

Irreversible
AI (artificial insemination)
Donor semen injected into vagina
In vitro fertilisation
Use of fertility drugs
FSH / LH in early stage of menstrual cycle
To stimulate follicle development / ovulation
Collect eggs & sperms (from donors)
Fertilisation in Petri dish
Embryo development in dish
Screening and selection of embryo
Insert into uterus
Give mother progesterone to maintain endometrium
HIV
Infects T-helper lymphocytes
B cells can’t be stimulated to divide to form a clone of plasma cells and produce antibodies
Less cytokines secreted to stimulate macrophages to carry out phagocytosis
Infected cells not killed by the immune system
Weaker immune response and immune system
Body more susceptible to infectious diseases e
...
tuberculosis, and cancer
Leading to AIDS / opportunistic infection
Causing weight loss / reduced life span

Ch18 Inheritance
Inheritance
Transmission of genetic information from generation to generation
Chromosome
Thread-like structure of DNA
Carrying genetic information in the form of genes
Mitosis
After exact duplication of chromosomes
Nuclear division giving rise to genetically identical cells
Repair damaged parts of the body by producing new cells
Replacement of cells
Growth
Asexual reproduction
Cell differentiation
As the embryo develops
Stem cells divide by mitosis
Only a particular set of genes is switched on and expressed
That cell specialised
Meiosis
Reduction division: only one set chromosomes passed on
Produce haploid gametes from diploid cells
Maintain chromosome number in the next generation, doesn’t double, still correct
Allow sexual reproduction
Produce genetic variation by crossing over and independent assortment
Crossing over
Two chromatids between homologous chromosomes
Break and rejoins so one part of a chromatid swaps places with the the part of the other
chromatid on the same locus
Homozygous
Having two identical alleles for a gene
Two identical homozygous individuals will pure-breed
Genotype
The genetic makeup of an organism
In terms of the alleles present
Phenotype

Observable features of an organism
Due to genotype
Dominant allele
Expressed if it is present
Recessive allele
Only expressed when no dominant allele
Codominance
Both alleles in a heterozygous individual are expressed together in the phenotype
Incomplete dominance
The phenotype of a heterozygous individual is the mixture of two alleles
Test cross
Find out the genotype of an individual with the dominant phenotype for a gene
By crossing it with one homozygous recessive individual
Heterozygous if recessive phenotype offspring can be produced
Pure breeding
Always homozygous
F1 population: always heterozygous of two different pure breeding strains
Sex-linked characteristics
A characteristic in which the locus of the gene is on a sex chromosome
More common in one sex than the other
Protein synthesis
The gene codes amino acid sequence in protein
DNA is transcribed to mRNA and remains in nucleus
mRNA carries instruction, moves out of nucleus through nuclear pores to ribosomes in cytoplasm
mRNA attaches and passes through ribosomes and translation occurs
tRNA uses its triplet to pair with complementary mRNA codon
A chain of amino acids produced, the order of amino acids depends on base sequence of mRNA
Modified in RER to protein
Transported from Golgi body

Ch19 Variation and natural selection
Discontinuous variation
Phenotypes put into distinct categories
No continuous range, no intermediates
Caused solely be genes / not affected by the environment
Often qualitative
Continuous variation
No definite categories
Phenotype varies and can take any intermediate value between two extreme
Often affected by both genes and the environment
Often quantitative
Adaptive feature
An inherited feature that helps an organism to survive and reproduce in its environment
The inherited functional features of an organism that increases its fitness
Fitness
Probability of an organism
Surviving and reproducing in the environment
Adaptive features of xerophytes: survive in places e
...
desert with short water supply
Sunken stomata
Closing stomata sometimes to prevent high water loss
Hairs to trap moist air next to the leaf
Succulent leaves
Thick cuticle
Small SA to reduce transpiration
Rolled leaves
Deep, branching and spreading roots to obtain more water
Adaptive features of hydrophytes: live in wet places / water
Hollow stalks and stems to help them to float on water to obtain more light
Stomata on both surfaces to absorb more CO2
Opening stomata
Large flat leaves
Thinner cuticle
Reduction in roots as H2O can directly diffuse to cells
Natural selection
Variation produces adaptive features due to new alleles & e
...
, caused by mutations, sexual
reproduction (meiosis, fertilisation)

Overproduction: more will be produced than the number of survivor in adulthood
Competition, struggle for existence: individuals with adaptive features are better competitors
Survival of the fittest, identify selection pressure: those are more likely to survive
Reproduction: advantageous alleles passed on to offspring as they will survive and reproduce
successfully
Generations ----> gradual change
Evolution: change in adaptive features of a population over time as the result of natural selection
Selection type
Stabilising selection
Stable environment
Extreme individuals are selected against
Reduce evolution
Directional selection
Environment changes overtime
Selective pressure let organisms to adapt to new conditions
Optimum feature shifts
Diversifying selection
Distinct environment changes
Extreme individuals are selected for
Leads to speciation
Sickle cell anaemia
CTT --> CAT
Glutamic acid --> Valine in β chain of Hb
Faulty Hb produced
Fibres of RBC forms which get stuck in capillaries
Reduce blood flow to certain parts of the body
Reduced oxygen capacity
Fatigue and short of breath due to reduced respiration
People with HBAHBS have selective advantage due to malaria
In regions where malaria is present, heterozygous people are more likely to survive
More of them reproduce so homozygous recessive children still produced
Selective breeding / artificial selection
Choose organisms with desired features
By measuring / observing
Cross / breed organisms by pollination / artificial insemination
(Collect seeds)
Allow reproduction and check features in the offspring
Cross individuals with intended variety
Keep crossing and selecting for many generations
Problems
Features human desire are not always adaptive to the environment

Ch20 Ecology
Ecology
The study of the interaction
Between living organisms
And their environment
Population
A group of organisms
Of one species
Living in the same area at the same time
Ecosystem
All of the organisms
And their environment
Interacting together in a given area
Community
All of the organisms
Of different species
In an ecosystem
Niche
The role of an organism in an ecosystem
Producers
Autotrophs
Make own organic nutrients
Carry out photosynthesis using energy from Sun
/ carry out chemosynthesis using energy from oxidation of chemicals
Consumers
Heterotrophs
Get its energy / nutrients by feeding on other organisms
Herbivore
Get energy from plants
1˚ consumer
Carnivore
Get energy from other animals
Higher level consumers
Omnivore
Get energy from both plants & animals

Energy lost
Initial inefficient capture of sun energy
Only certain wavelength of sun radiation captured by photosynthetic producers
A large proportion loss as heat or reflected
Not all eaten / digested
Lost in respiration as heat for e
...
maintaining body temperature in endotherms
Lost in faeces / urine due to incomplete digestion and absorption
Transported to decomposers
Less energy to next trophic level (only about 10%)
Not too many trophic levels as not enough energy to support a large population
Trophic levels
Position of an organism
In a food chain / web, pyramid of biomass / numbers
Reason for different shape between pyramids of numbers & biomass
Pyramid of biomass is pyramid-shaped
Producer has large individual biomass
One producer supports food for many consumers
Decomposers
Heterotrophs
Consume remains of other organisms / waste organic matter
Help to release substances from dead organisms to be reused e
...
CO2 for photosynthesis
N cycle
Nitrogen fixation
N2 + 3H2 ----> 2NH3
By lightning
By Haber process
By nitrogen-fixing bacteria in root nodules on e
...
peas, beans and clover
Nitrification
Ammonium to nitrates & nitrites which are available to plants and absorbed by them
Ammonium from nitrogen fixation or decomposition of proteins in plants & animals
Denitrification
Nitrates & ammonium to nitrogen in air
Making proteins in plants
Plants absorb ammonium & nitrates to make amino acids to make proteins
Animals feed on plants and nitrogen flow though food chain
Population growth
Limiting factors
Diseases
Limitation of food resources and space

Toxins / waste build up / pollution / pH change
Predators hunting
Habitat loss
Lag phase
Low growth rate, BR > DR
No limiting factors
Small number of breeding individuals
Exponential phase
High growth rate, BR >> DR
No limiting factors
Large number of breeding individuals
Stationary phase
0 growth rate, BR = DR
Environment reaches carrying capacity
High DR due to limiting factors stabilising population
Death phase
-ve growth rate, BR < DR
Limiting factors become overwhelming
Reasons for human population increase
Reduction of disease
Improvements in hygiene e
...
water and food supply and sewage treatment
Immunisation against diseases
Discovery of antibiotics
Increase in food supply
More land used for agriculture
More efficient food production

Ch21 Biotechnology
Biotechnology
Using living organisms to carry out processes
Make substances that we want
Reasons of using microorganisms
Small, easy to grow, do not take up a lot of space
Fast reproduction
No ethical issues
Share the same genetic material with human
Contain plasmid to transfer genes
Making biofuels
Treat maize with amylase
Allow yeast to respire anaerobically
Adv
Uses renewable resources
Growing crops help to absorb CO2, carbon neutral, reduced global warming
Less pollutants causing acid rain
Can use waste of plants
Dis
Land required (o
...
)
Slow
Yeast stops working at low level of ethanol
Glucose used up
Enzymes denatured by higher temperature due to the exothermic reaction
High [ethanol] kills yeasts
Low purity: requires fractional distillation
May drive up food price, causing famine
Making bread
Mix flour with water and yeast to make dough
Anaerobic respiration of yeast makes dough to rise due to stretchy gluten in flour
Baking to kill the yeast and break down alcohol
Biological washing powders
Protease to break down protein based pigments e
...
Hb
Lipase to break down greasy stains
Pectinase
Break down pectin to assist extract of juice
Adv

Extract more juice
Pectin is converted to sugar, sweeter
Juice will be clearer
Production by micro-organisms in a fermenter
Grow in sterilised fermenter
Provide them nutrients + e
...

To allow them to grow, reproduce and produce desired products
Provide sterilised (prevent contamination) oxygen to allow respiration
Control an optimum temperature, a suitable pH using probes to monitor
Stir to mix nutrients with them
For even distribution of nutrients
Ensure most bacteria have access to nutrients by dissolving oxygen and other nutrients so
they can absorb nutrients more easily
Prevent bacteria clumping which limit growth / roll fungus into pellets for easier separation
To maintain even temperature
Water jacket to control temperature
Production of products
Extraction from culture
Purification
Genetic engineering
Transfer of a gene between organisms artificially
Bacterial production of human proteins
Identify and cut target human gene by restriction endonuclease enzyme forming sticky ends
Isolate it from human cell
Plasmid removed from bacterial cell
Cut the plasmid with the same restriction enzyme to form complementary sticky ends
Ligase joining plasmid and human gene forming recombinant plasmid
Plasmid inserted into bacteria as a vector
Bacteria reproduce in the fermenter
Start to produce human proteins
Uses
Make insulin for Type 1 diabetes patients
GM crops resistant to herbicides / pests
Golden rice with extra vitamin A (deficiency causes night blindness)
Adv
Increase agricultural yield, reduce food price and famine, increase income
Healthier food produced
Increase biodiversity
Evolving pesticide resistance
Reduce demand for pesticides
Develop resistance against extreme conditions e
...
salinity, drought, frost
Concerns

Creating superweed
Prevention
Grow in glasshouse
Only grow female / sterile them by removing stamens / cover flowers
Isolate using a large gap / wall

Ch22 Humans and the environment
Dis of monoculture
Low biodiversity (species & genetic)
Increase pest population which reduce yield
Easy spread of plant disease e
...
viral
Insecticides may lead to resistance
Overuse of pesticides kill non-target species
May deplete nutrients in soil which causes farmers to rely on more fertilisers
Fertilisers cause eutrophication
Habitat destruction, extinction of endangered species
Dis of intensive livestock production
Welfare issues for the livestock: crowded conditions in which they are kept
Expensive feeding
Energy inefficient
Easy spread of disease
Antibiotics may lead to resistance
Waste produced pollute land and waterways nearby
Use pesticides, loss of biodiversity
Providing food requires monoculture
Use of hormone affects wild animals
Reasons of habitat destruction
To make land available for crops, livestock, buildings and roads
To mine underground resources
Pollution kills plants
Effects of deforestation
Trees are cut
Expose soil
Washed away by rain to river causing flooding / be blown away
Soil erosion
Land become desert
Agricultural land loss
Habitat loss
...
g
...
g
...
g
...
g
...
g
...
g
...
to homeostasis / negative feedback
Action (hormone secretion, nerve impulse pathway)
Effect
Result
Keeping the factor in a set range
Involuntary / voluntary
Explain genotype
State possible genotype
State type of inheritance e
...
sex-linked, codominance
Using genotype to explain phenotype e
...
has a gene of
...

Use pedigree to explain existence of another gene
Discuss the possibility of that gene from the other partner

Describing data
Overall trend
Change in gradient e
...
increases slower
Specify any turning points
Fully use of comparative data
Comparing data
Compare overall size / percentage
Compare rate of change
Compare position of turning points
Fully use of comparative data
Describe transport process
Size of particle
Where produced
Type of transport
Concentration / water potential gradient explain and identification
Direction
Medium / cell membrane
Transporters
Volume / pressure change, what gains / lost
Potential effects (swell, burst, shrink / shrivel up, turgid, flaccid, plasmolysis)

Practicals
Checklist of table
All variable in
Unit
Correct reading
Checklist of graph
Labelled axes
All points correct
Smooth line
No extrapolation (unless value will from origin)
Checklist of drawing
As large as possible
Details of outline (e
...
zig-zag)
Details of inner structure
Proportion
Experiment conclusion
How independent variable affects dependent variable
Source of error
Difficulties in controlling controlled variable & independent variable
Volume (different volume each drop) —> graduated pipette
Reuse measuring apparatus (contamination)
Temperature (change as reaction occurs) —> thermostatically controlled water bath
Time / distance intervals --> use smaller ones
Difficulties in measuring dependent variable
repeat —> calculate mean
colour —> colorimeter / white background
Small sample size --> not representative
Experiment design
Suitable use of apparatus
use of control
ways to change independent variable (range, interval)
ways to measure dependent variable
controlled variable
Time of reaction / methods - stopwatch
Temperature - thermostatically controlled water bath, equilibration
pH - buffer, measure by pH meter
Concentration, amount and type of reagent used

Type and size of sample
repeat with same AND different independent variables
Checklist of experiment design
A set of independent variables (> 5)
Dependent variables clearly identified
> 3 controlled variables
Control
Methodology for measuring & controlling of variables
Replication
Safety precautions
Reason for using percentage
different start variable
for fair comparison
Reason for using a large sample
To obtain a representative data set
To identify anomalous results
Reason to repeat
To identify anomalous results
To increase reliability
Reason of a control used
With absence of independent variable
To compare and show it is the independent variable which causes changes in dependent variable
As reference of dependent variable
Precautions
Goggles
Gloves
Environment for exercise
Use forceps to handle things
Food test
Test for reducing sugar
Crush or grind food
Add water and 5 - 10 drops of Benedict’s solution
Heat to about 80˚C
If from blue --> green / --> yellow / --> orange --> / brick-red, then +
Test for starch
Put food on a white tile
Drop 1 - 2 drops of iodine solution

Put on a white tile
If from red-brown --> blue-black, then +
Test for lipids
Crush food
Add ethanol
Shake thoroughly
Add to some distilled water in another test tube
If clear --> milky / opaque, indicating fats emulsified, then +
Test for proteins
Put food into a test tube and add water
Add biuret reagent
Shake
If blue --> purple, then +
Test for vitamin C
Measure 2cm3 of DCPIP into a test tube
Use a dropper to add liquid / dissolved food
Count how many drops required to decolourise DCPIP
Exercise experiment
Controlled variable
Gender
Fitness
Age
Speed of running
Environment
Resting
Safety precautions
Suitable environment



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