BIOLOGY IGCSE FAQ

Dhruv
DEFINITION QUESTIONS 1-2 MARKS
GOLDEN QUESTIONS 3-6 MARKS
GENERAL NOTES
Paper 6

I know that you guys are studying at the last minute. As of writing this, I am sitting for May/June 2024. Best of luck guys!!

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DEFINITION QUESTIONS 1-2 MARKS

Diffusion

Movement of particles from high to low concentration down the concentration gradient as a
result of random motion.

Osmosis
Movement of water from high to low water potential down the water potential gradient
through a semipermeable membrane

Active Transport

Movement of substances from low to high concentration through a semipermeable

membrane against a concentration gradient using energy from aerobic respiration

Translocation

Movement of sucrose and amino acids in the phloem from source to sink via active
transport.

Enzyme

Biological catalysts made out of proteins that increases rate of reaction while remaining
unchanged at the end of reaction.

Transmissible Disease

Disease where pathogens can be transferred from one host to another

Species

A group of organisms that can reproduce to make fertile offspring

Pathogen

Microorganisms that cause diseases

Excretion

Removal of waste products and excess material produced by metabolic processes from the
body through excretory organs

Sensitivity

Ability to detect and respond to changes in the internal or external environment

Drugs

Any chemical substance consumed that alters/modifies chemical reactions in the body

Hormone

A chemical substance produced by a gland and carried by the blood, which alters the activity
of one or more specific target organs

Sexual reproduction
Process where the nuclei of two gametes fuse to form a zygote (and the production of
offspring that are genetically different)

Fertilisation

Fusing of nuclei from a male and female gamete

Variation

Difference between different individuals of a species

Genetic Mutation

Random change in base sequence of DNA

Gene

Length of DNA that codes for a protein

Allele

Alternate form of gene

Organ

A structure made up of groups of different tissues, working together to perform a specific

function

Sense organ

A group of receptor cells that work together to detect and respond to specific stimuli

Pollination

Transfer of pollen grain from one plant to another from anther to stigma

Deamination

Removal of the nitrogen-containing part of amino acid to form urea

Homeostasis

Maintenance of constant internal environment

Codominance

When both alleles for a gene equally contribute to the phenotype.

Genotype

Genetic makeup of an organism in terms of alleles

 Phenotype

Observable features of an organismSpecies

Group of organisms that have similar genetic coding with minimal variations and can
reproduce to produce fertile offspring

Population

Group of organisms of the same species living together in the same area at the same time.

Community

Population of all the different species living in the same ecosystem

Assimilation

Absorption of nutrients for cell usage

Limiting factor

An environmental factor that limits life processes due to its shortage in the environment

Transpiration

Loss of water vapour via evaporation on the surface mesophyll cells followed by diffusion of
water vapour through the stomata.

Meiosis

The nuclear division of cells to produce daughter cells with half the number of chromosomes,
so haploid cells. The daughter cells are genetically different and are gametes.

Mitosis

The nuclear division of cells that produces two genetically identical daughter cells with equal
and diploid number of chromosomes.

Ecosystem

A unit containing all the communities of different organisms and their environments
interacting with each other.

Trophic levels

The position of an organism on a food chain, food web, or an ecological pyramid.

Sustainable Resource

A resource that is produced/replenished at the same rate that it is used up such that it does
not run out nor harm the environment.
GOLDEN QUESTIONS 3-6+ MARKS
How neurotransmitter/nerve impulse is passed

Vesicles containing neurotransmitters move to the cell membrane of the presynaptic

membrane and fuse their membrane with it. Impulse stimulates vesicles to release
neurotransmitter molecules into synaptic cleft. Vesicles release neurotransmitters.
Neurotransmitters diffuse across the synaptic cleft/gap and bind with the complementary
shaped protein receptors that are on the cell membrane of postsynaptic membrane, passing
electrical impulse.

How does wilting occur

1.​ Wilting occurs bc the plant has higher water potential than the soil, water is lost from
cells via osmosis which moves from plant to soil
2.​ Water transpires from leaf to atmosphere
3.​ Plant loses water faster than it can gain
4.​ Turgor pressure caused by water pushing against cell wall decreases
5.​ Plant loses turgidity and becomes flaccid
6.​ if not treated cells become plasmolyzed

How to remove oxygen debt

When oxygen debt occurs, lactic acid is produced. Heart rate remains high to transport lactic
acid in the muscles to the liver. Breathing rate and depth of breathing increases to supply
oxygen. Lactic acid is broken down in the liver via aerobic respiration.

Role of liver in excretion

The liver removes the nitrogen-containing part of amino acids via deamination to form urea
and amino acids which are then assimilated into proteins

How do vaccines work

Vaccines contain inactive (dead or weakened) pathogens. After the vaccine, the pathogen
enters the body and triggers the immune response.

Lymphocytes produce memory cells to store information about the pathogen and produce
antibodies that are complementary to the shape of the antigen that are on the cell membrane
of the pathogen.

The antibodies bind to the antigen and form an antibody-antigen complex. The antibodies
neutralise the toxins produced by the pathogens or get clumped together and are marked for
phagocytosis.
 How cholera causes diarrhoea

Cholera bacteria stick to the lining of the small intestines that release toxins that cause
release of chloride ions that lower the water potential of the small intestine. Cells around the
small intestine have higher water potential and release water via osmosis into the small
intestine. This causes watery faeces.

How proteins are made by a cell

1.​ Genes are transcribed into mRNA (DNA stays in the nucleus)
2.​ mRNA leaves nucleus and moves to cytoplasm and passes through ribosome
3.​ Ribosome translates mRNA into a protein by assembling amino acids
4.​ Order of amino acids is determined by base sequence of DNA/gene

Bright Light Dim Light

●​ Circular muscles contract ●​ Circular muscles relax

●​ Radial muscles relax ●​ Radial muscles contract
●​ Pupil constrict (pupil size decrease) ●​ Pupil dilate (pupil size increase)

Near Object Far Object

●​ Ciliary muscle contract ●​ Ciliary muscle relax

●​ Suspensory ligament relax/slacken ●​ Suspensory ligament
●​ Lens becomes more convex/thicker contract/tighten
●​ Light is refracted more ●​ Lens becomes less convex/thinner
●​ Light is refracted less

Explain how bacteria become resistant to antibiotics

1.​ Antibiotics cause non-resistant bacteria to die leaving resistant bacteria. Resistant
bacteria survive due to genetic mutations.
2.​ Surviving bacteria reproduce and pass on their advantageous allele/genes that give
the resistance trait to their offspring.
3.​ Number of resistant bacteria increases.
4.​ Natural selection makes bacteria become better adapted to antibiotics. Thus making
them resistant.

Pathway of the heart

1.​ (Starts as deoxygenated blood) Vena Cava

2.​ Right Atrium
3.​ Tricuspid (Atrioventricular) valve
4.​ Right ventricle
 5.​ Semilunar valve
6.​ Pulmonary artery
7.​ Lungs (becomes oxygenated blood)
8.​ Pulmonary vein
9.​ Left atrium
10.​Bicuspid (Atrioventricular) valve
11.​Left ventricle
12.​Semilunar valve
13.​Aorta
14.​To body (as oxygenated blood then becomes deoxygenated as body uses oxygen

How water uptake occurs

When transpiration occurs, evaporation of water vapour causes a negative pressure that
creates a suction pull, drawing up water, also due to osmosis. Water molecules are attracted
to each by cohesive forces and adhesive forces between the walls of the xylem creating
continuous columns of water.

Vasodilation (Temperature increase) Vasoconstriction (Temperature decrease)

●​ Thermoreceptor detect temperature ●​ Thermoreceptor detect temperature

increase and sends impulse to the decrease and sends impulse to the
brain brain
●​ Arterioles dilate, allowing more ●​ Arterioles constrict, allowing less
blood flow to skin surface to blood flow under skin to decrease
increase heat loss to surroundings heat loss to surroundings
●​ Sweat glands produce sweat, which ●​ Sweat glands do not produce
evaporates to cool down body sweat/produce less sweat
●​ Erector muscles relax, lowering hair ●​ Erector muscles contract, raising
so that it does not trap air particles hair to trap air particles for insulation
●​ Skeletal muscles cause shivering
which helps body gain heat energy
due to respiration

Inhalation Exhalation

●​ Internal intercostal muscles relax ●​ Internal intercostal muscles contract

●​ External intercostal muscles ●​ External intercostal muscles relax
contract ●​ Volume of thorax decrease
●​ Volume of thorax increase ●​ Pressure of thorax increase
●​ Pressure of thorax decrease ●​ Diaphragm relax
●​ Diaphragm contracts ●​ Rib cage goes inward and
●​ Rib cage goes upward and outward downwards (back to original
●​ Air goes in position)
●​ Air goes out
 Glucose level increases Glucose level decreases

●​ Insulin is produced in the pancreas ●​ Glucagon is stored in the pancreas

●​ Converts glucose to glycogen ●​ Converts glycogen to glucose
(stored in liver) ●​ Increase glucose levels
●​ Decrease glucose levels

Biological washing powders (why are they only effective in [insert] temperature?)

●​ Contain protease and lipase to remove protein stains and fat/oil

●​ Break down large insoluble molecules into smaller soluble molecules that can be
washed away
●​ Only effect in [insert] temperature as it is optimum as more enzyme substrate
complexes can be formed. Any temperature higher than optimum will cause enzymes
in washing powder to denature.

Active Immunity Passive Immunity

●​ Longer process (Long term) ●​ Short process (Short term)

●​ Produces memory cell ●​ Does not produce memory cell
●​ Natural: Exposure to pathogens ●​ From another source: Breastmilk,
●​ Artificial: vaccines direct injection of antibodies

Describe the stages in the reproduction of a flowering plant from self pollination to
fertilisation (0610/43/O/N/23)

●​ Self pollination is the transfer of pollen grain from anther to stigma of the same flower
or different flower of the same plant
●​ Pollen grain germinate to form pollen tube
●​ Pollen tube carries male gamete and travels down the style to get to ovary
●​ Pollen tube grows down penetrates the ovule via micropyle
●​ Pollen tube bursts and releases male gamete to fuse with ovule to form diploid
zygote

Reflex arc

1.​ Receptor detects stimulus

2.​ Sensory neuron creates and transmits an impulse to spinal cord
3.​ Relay neuron passes the impulse to motor neuron
4.​ The motor neuron carries the response to effector
5.​ Effector carries out about the response, muscle contraction for example
 Why do food chains usually have less than 5 trophic levels?

Across each trophic level, energy is lost. 90% percent of energy is lost as growth, excretion
and movement (any other use of energy is also acceptable except growth and protein
synthesis). Only 10% of energy is transferred to each trophic level. There is not enough
energy to sustain 5 trophic levels.

How are the proteins in the cattle manure converted to the type of ions plants can absorb?

1.​ Proteins are broken down/decomposed into amino acids via decomposers (nitrogen
fixing bacteria) OR Proteases break down proteins into amino acids
2.​ Deamination by decomposers converts amino acids into ammonium ions
3.​ Ammonium ions are converted into nitrite ions to nitrate ions via nitrifying
bacteria/nitrification

Explain how bacteria are genetically engineered to make human insulin

1.​ Human genes are cut using restriction enzyme to form sticky ends
2.​ Plasmid is cut using the same restriction enzyme to form complementary sticky ends
3.​ Human gene is combined with the plasmid using DNA ligase enzyme
4.​ To form a recombinant plasmid
5.​ Recombinant plasmid is re-inserted into the bacterium
6.​ Bacteria are grown in fermenters and allowed to reproduce

How is the growth of a plant shoot controlled?

(Phototropism)

Auxin is a growth hormone. Auxin will diffuse to the shaded side causing plant cells to
elongate and move towards sunlight

OR

(Gravitropism)

Auxin is a growth hormone. Auxin will diffuse down the plant. It collects on the lower side of
the plant causing plant cells to elongate. The plant bends upwards.

Urine formation

●​ Blood enters the kidney through the renal artery

 ●​ Blood flow branches out to blood capillaries in the nephron
●​ Blood enter the glomerulus through the afferent arteriole in high pressure
●​ Ultrafiltration: large molecules such as fat, blood cells, platelets, protein will remain in
the glomerulus, and exit through the efferent arteriole
●​ Small molecules such as amino acids, water, urea, mineral salts, glucose pass
through a partially permeable membrane into the bowman’s capsule.
●​ They pass through the proximal convoluted tubule, and all glucose, amino acids, and
most mineral salts and water is selectively reabsorbed
●​ They move into the loop of henle and the distal convoluted tubule, where some water
is also reabsorbed
●​ Excess water, urea, mineral salts pass out the collecting duct and into the renal
pelvis as urine

Describe how starch is broken down in the human digestive system so that it can be
absorbed in the blood
(0610/42/M/J/24)

●​ Starch is broken down via mechanical digestion using teeth and the churning
movement in the stomach
●​ Mechanical digestion increases surface area for faster enzyme activity
●​ Chemical digestion breaks down large insoluble substances into small soluble
substances
●​ Salivary glands in the mouth produce amylase which breaks down starch to maltose.
●​ Maltose is broken down into glucose via the maltase found in the epithelium of the
small intestine

GENERAL NOTES
●​ Features of organisms
●​ Tests, Digestion system, Enzymes
●​ Plants
●​ The Body, Reproduction
●​ Environment

Features of organisms
 Kingdoms Characteristics Examples

Animal ●​ No cell walls ●​ Tigers

●​ Multicellular ●​ Fish
●​ Coral

Plant ●​ Have cell walls made of cellulose ●​ Moss

●​ Undergo photosynthesis ●​ Ferns
●​ Have chloroplasts ●​ Mango
tree

Fungi ●​ Have strands of hyphae ●​ Toadstool

●​ No chloroplasts s

Protista ●​ Multicellular & unicellular ●​ Algae

●​ Has a nucleus ●​ Amoeba
●​ Some undergo photosynthesis or feed on ●​ Euglena
organic substances

Prokaryotes ●​ Mostly unicellular ●​ Virus

●​ No nucleus ●​ Bacteria
●​ No mitochondria
●​ Free loop of DNA in cytoplasm
●​ Have flagellum to aid in movement
●​ Viruses have a protein coat, Bacteria have a
cell wall

●​ features of insects
○​ three pairs of jointed legs , two pairs of wings , three body segments &
antennae,compound eyes
●​ features of arachnids
○​ four pairs of jointed legs , two body parts , simple eyes
●​ features of crustaceans
○​ more than four pairs of legs , two body parts and compound eyes
●​ features of myriapods
○​ many body segments , one or two pairs of legs in each segment , antennae
○​ centipede ⇒ one pair ll millipede ⇒ two pairs
●​ features of monocots
○​ narrow shaped leaves , parallel veins , one cotyledon in a seed , petals in
multiple of three
●​ features of dicots
○​ broad leaves , network veins on leaves , petals in multiple of 4 & 5 , two
cotyledons
●​ features of bacteria
○​ no nucleus , no membrane-bounded organelles & unicellular
○​ has cell membrane and cell wall , has DNA strand and plasmid
●​ features of viruses
○​ protein coat and genetic material , and NO cell walls ( so antibiotics doesn't
affect viruses )
 credit: @darumdarimda_ on discord

Tests, Digestion system, Enzymes

Edit: Chemical digestion is the breakdown of large insoluble molecules into smaller soluble
molecules via enzymes/chemical substances to be absorbed.
Plants
 Plant cell adaptations

Part Adaptations

Waxy cuticle Make leaf water proof, transparent to allow sunlight in

Upper epidermis Transparent to allow sunlight in

Palisade mesophyll Lots of chloroplasts to convert sunlight to chemical energy via

photosynthesis

Spongy mesophyll Has a lot of air spaces to allow gases to diffuse into the plant easily

Vascular bundle Xylem

●​ Has lignin cell walls to ensure that it stays open and does not
collapse for support
●​ Hollow with no organelles to let water in without resistance
●​ Narrow to ensure that the column of water does not break

Stomata ●​ Has guard cells to open and close the stomata

(Limiting factors) Explain the rate of transpiration when:

Temperature increases Humidity increases Light intensity increases

●​ Transpiration ●​ Transpiration ●​ Rate of

increases decreases photosynthesis
●​ Kinetic energy of ●​ Concentration of increases
water vapour water vapour in ●​ Transpiration
increases atmosphere increases
●​ Diffuse faster into around plant is ●​ Stomata opens more
stomata high in the light as it
●​ Stomata opens more ●​ Lower remains open to allow
concentration gases (carbon
gradient dioxide) in as a
●​ Lower rate of reactant for
diffusion photosynthesis whilst
●​ Stomata opens allowing water to
less escape as a product
of photosynthesis
 Function

Sepal Protects flower when in bud

Petal Attract pollinators

Ovary Site of fertilisation, contains ovule

Anther Produces pollen grains (male gametes)

Filament Supports anther

Stigma Receives pollen grains during pollination

Carpel Female part of the flower

Wind pollinated Insect pollinated

No petal/dull petals Big and bright petals

Feathery stigma Stigma is sticky

Pollen grains are small light and abundant Pollen grains have spikes/hooks and is
produced in small amount

Anther is outside flower Anther is inside flower

Filament is long and sticky Small filament

No smell and nectar Sweet scent, has nectar

 Stigma outside of flower Stigma is inside flower

Self pollination Cross pollination

Transfer of pollen grain from one Definition Transfer of pollen grain from one
anther of a flower to the stigma of anther of a flower to stigma of a
the same flower or a different different flower of the same
flower from the same type of plant species

●​ No pollinator needed Advantages ●​ Increased biodiversity and

●​ Fast process variation
●​ High success rate ●​ Resistance to disease
●​ Isolated species can ●​ Ability to adapt to change
reproduce in environment
●​ Less energy needed

●​ Lack of dispersal can Disadvantages ●​ Long process

cause competition ●​ Require pollinator
●​ No variation ●​ Wasting of gametes
●​ No adaptation to change in ●​ Lower chance of success
environment
●​ Offspring can become
homozygous overtime and
result in loss of gene pool

Xenophytes Hydrophytes

●​ Thick waxy cuticle ●​ Contains large air spaces

Reduce water loss More buoyant
●​ Spiky leaves ●​ No/little stomata in the lower
Reduce water loss epidermis
●​ Small number of stomata ●​ Roots are poorly developed and
Reduce water loss also has air spaces
●​ Deep and long roots ●​ Stems are weak as they don't need
Able to access water sources deeper to support the plant
underground, larger surface area of
absorption of water

Source and sink

Sink: part of plant that is using or storing glucose and amino acids ​
Source: part of plant that is producing (leaf when photosynthesizing esp. during summer) or
releasing (roots during spring) sucrose and amino acids
Plant adaptations

Xerophyte (plants adapted to living in very dry, arid conditions)

Stem Leaf Roots

Swollen stem Needle-like to reduce Shallow spreading roots to

surface area catch rainwater

Hairs in the lower epidermis Deep to find water source in

to catch water vapour soil

Waxy cuticle

Hydrophytes (plants adapted to living in very moist, wet conditions)

Stem Leaf Roots

Large air spaces to float Small and shallow since

they can extract water
through their tissues

Stomata found in upper No root hairs

epidermis and usually open
all the time

The Body, Reproduction

Adaptations

Septum To separate oxygenated and deoxygenated blood

Valves Prevents backflow of blood

Arteries ●​ Takes blood out of heart

●​ Small lumen, thick walls to carry high pressure
oxygenated blood

Veins ●​ Takes blood into heart

●​ Large lumen
●​ Has valves
 Adaptations

Sperm ●​ Acrosome: Contain packet of enzyme which breaks down the jelly coat of
the egg cell
●​ Many mitochondria: More energy for swimming
●​ Flagellum: Aid in movement (for swimming)

Egg ●​ Jelly coat: Hardens to prevent sperm from entering after fertilisation
●​ Energy/Nutrient stores: For development of embryo

Adaptations

Gas exchange ●​ Large surface area to increase rate of diffusion

surface (Alveoli) ●​ Good blood supply to maintain steep concentration gradient
●​ One cell thick to reduce diffusion distance and increase rate of
diffusion
●​ Moist so that gases can be dissolved and absorbed easily

Villi ●​ Microvilli to increase surface area

●​ One cell thick to reduce diffusion distance and increase rate of
diffusion
●​ Lacteal for absorption of lipids
●​ Good blood supply to maintain steep concentration gradient,
quick access to bloodstream

Red blood cell ●​ Biconcave shape to increase surface area for more oxygen
absorption
●​ No nucleus so that it can hold more oxygen
●​ Haemoglobin to bind onto oxygen

Trachea ●​ Cartilage to prevent airway collapse and protect trachea

Neurons ●​ Long/Have axon to carry impulses for long distances

●​ Has many mitochondria that provide energy via aerobic
respiration for transmission of impulses
●​ Has vesicles which hold neurotransmitter
●​ Receptor molecules to pass and receive impulses
●​ Branches to connect to other neurons

Hormonal communication Nervous communication

●​ Long term ●​ Short term

●​ Multiple target organs ●​ One target
●​ By glands ●​ Conducted by CNS
●​ Carried by blood ●​ Carried by neurons

Advantages of double circulatory system

 ●​ Maintain high blood pressure in systemic circulation and low pressure in pulmonary
●​ Separates oxygenated and deoxygenated blood
●​ Faster and efficient supply of blood and nutrients to body cells
●​ Allows efficient filtration in kidneys
●​ Maintains high metabolic rate in the body
●​ Provide more time for gas exchange

Evidence of double circulatory system

●​ Blood flows through twice in one circuit

●​ Two separated blood circuits (pulmonary and systematic)
●​ 4 chambers with a septum

Shit to remember: Renal vein, renal artery, hepatic vein, hepatic artery, hepatic portal vein
(transports deoxygenated blood, glucagon & amino acids from the gut to the liver)

Selective reabsorption

Substances Amount absorbed How it is reabsorbed

Glucose Everything Active transport

Water Some Osmosis

Urea & Toxins None -

Mineral salts Some Active transport

Amino acids Everything Diffusion

Function

Iris Controls amount of light that enters pupil

Retina Contains light receptor cells (rod and cone cells)

Fovea Region of retina with highest density of cones. Light is

concentrated at this point.

Lens Transparent disc that helps to focus light on fovea by

changing shape

Optic nerve Sensory neuron that transmits impulses to brain

Part of eye Number of cone cells Number of rod cells

Blind spot None None

Fovea Many Few

Retina Few Many

Asexual Reproduction Sexual Reproduction

Definition
Process resulting in Process where the nuclei of two gametes
production of genetically fuse to form a zygote (and the production
identical offspring from one of offspring that are genetically different)
parent

●​ Good traits are Advantages ●​ Genetic variation

passed down to ●​ Increased biodiversity
offspring ●​ Ability to adapt to change in
●​ Faster than sexual environment
reproduction ●​ Resistance to disease
●​ Can rapidly grow in ●​ Seed dispersal can reduce
correct environment competition between parents and
●​ Uses less energy offspring
●​ No gamete needed

●​ No adaptation to Disadvantages ●​ Difficult to reproduce when

change in isolated
environment ●​ Requires pollinators
●​ Offspring can ●​ Takes longer
become ●​ Requires two parents
homozygous
overtime and result
in loss of gene pool
●​ Lack of dispersal can
cause competition
●​ Offspring can inherit
bad traits

Hormone Where it is Target What it does Inhibits Stimulates

secreted Organ

FSH Pituitary gland Ovary Stimulates follicle - Oestrogen

growth

LH Pituitary gland Ovary Causes ovulation - Progesterone

Progesterone Ovary/Placent Uterus Maintain pregnancy LH -
a ●​ Thicken
uterus wall
●​ No
fertilisation?
Causes
menstrual
cycle

Oestrogen Ovary Uterus Repairs uterus FSH LH

lining

Environment
 Continuous variation Discontinuous variation

●​ Range of extreme values with ●​ Range of values with no

intermediates intermediates
●​ Affected by environment and genes ●​ Affected by genes only and is
●​ Ex: Height, Weight, Muscle mass, inherited
Hair colour ●​ Example: Blood group, Gender, Ear
●​ Displayed via bell graph lobes, Ability to roll tongue
●​ Bar chart

Genetically modifying crop plants

Advantages Disadvantages

-​ Disease resistance -​ Reduced natural biodiversity

-​ Higher yield -​ GM seeds are expensive
-​ Herbicide resistance -​ Ethical concerns (because you change
-​ More desirable product therefore more nature or smth)
income -​ Could cross pollinate into wild
-​ Adaptation to extreme conditions population
-​ could cause pesticide resistant
weeds

Eutrophication Monoculture Intensive Livestock

farming
The process in which Planting one species of crop Raising large numbers of
excessive growth of algae in an agricultural area at a livestock in confined
occurs in a water body due to large scale spaces to maximise
excessive minerals and production
nutrients from sources such
as fertilisers

●​ Loss in biodiversity ●​ Spread disease

●​ Fertilisers seep into ●​ Increase in pest ●​ Water pollution
bodies of water number ●​ Reduced
●​ This causes growth of ●​ Increased greenhouse biodiversity
producers such as algae. gases ●​ Increased
Results in algae bloom ●​ Global warming, greenhouse
●​ This prevents oxygen climate change gases
from penetrating through ●​ Habitat loss
the water and dissolving ●​ Disruption in food
in the water. chain
●​ Sunlight cannot pass
through, photosynthetic
plants die
●​ When the producers start
to die, the decomposers
start to decompose the
producers
●​ The decomposers
respire aerobically which
uses all the oxygen in
the water, reducing the
oxygen concentration in
the water.
●​ All organisms die due to
lack of oxygen

Consequences Prevention

Deforestation ●​ Flood ●​ Replanting trees

●​ Erosion ●​ Reserve forests/Conservation
●​ Loss in habitat areas
●​ Decrease in oxygen in ●​ Laws to limit tree cutting
atmosphere ●​ Education
●​ Loss in biodiversity ●​ Stricter requirements in order to
●​ Extinction gain licence to cut
●​ Increase punishments for illegal
deforestation
 Cause Consequences

Habitat destruction ●​ Extraction of natural ●​ Loss in biodiversity

resources, land for housing, ●​ Extinction
farming activity ●​ Habitat loss
●​ Pollution
●​ Oil spills
●​ Eutrophication

AI (Artificial insemination) IVF (Vitro fertilisation)

- Used when animal is reluctant to mate in - Females are given fertility drugs
captivity - Their ovaries releases multiple mature
- Sperm samples are collected from the ova, collected by laparoscopy
males - Ova are mixed with the male seminal fluid,
- These samples are then artificially allowing some sperm to fuse with the
introduced into the female reproductive - Fertilisation takes place in petri dishes
system - The dividing zygotes are introduced into
- These samples can also be frozen and the female’s uterus by inserting a tube into
stored for later use. the cervix

Paper 6

Chapters to focus on:

Cellular movement (Osmosis, Diffusion & Active transport)
Biological Molecules (Food tests & Enzymes)
Factors affecting photosynthesis & transpiration
Gas exchange

Safety Precautions:
●​ Keep away from flame
●​ Tie up long hair
●​ Wear a lab coat
●​ Wear goggles
●​ Wear gloves
●​ Keep a first aid kit
●​ Avoid splashing
●​ Handle equipment properly to ensure it does not drop on anyone

Possible errors & fixes

Error / Issue Fix / Equipment

Deciding colour changes by eye Use colorimeter

Parallax Error Ensure to read measurements at eye

level

Not using a thermostatically

controlled water bath to keep
temperature constant

Stirring manually and not mixing Use stirrer

the solution entirely

- Repeating experiment

- Take more values to calculate an average

Leakage of air Close bung quickly

pH was not controlled Use buffer solution

Cross contamination Use different apparatus

Heat from lamp not constant Use heat filter

Water evaporation Cover with lid or bung

Food Tests

Test name For what? Result

Biuret Reagent Protein Blue > Purple

Ethanol Emulsion Fat/Lipid & Oils Colourless > Milky

Add ethanol & water to food

sample, and with a mortar

Iodine Starch Brown > Blue

Benedict’s Solution Reducing Sugar Blue > Brick-red

(REMEMBER TO HEAT IN
WATER BATH AT 80°C)

DCPIP Vitamin C Blue > Colourless

Hydrogencarbonate Carbon dioxide Yellow (Acidic, most CO2)

indicator Red (Some CO2)
Purple (Alkali, no CO2)
 Drawing (4 marks)

1 mark: line, must be clear with no sudden cross sections and no shading

1 mark: scale, draw it BIGGGGG

2 marks: two smaller details on the drawing

Graph

1 mark: Axis (WITH UNITS)

2 marks: Values (CORRECT UNITS
1 mark: Line (A CLEAR LINE)

Experiment (6 marks)

Independent variable (What is changing? What is the experiment based on?)

Dependent variable (What do you need to calculate to get your results)
Controlled variable (What stays the same so the experiment is fair?)

Method:
1.
2.
3.

Safety: (Gloves, googles, etc)

remember to mention specific values and units (ex: 40°C, 5 cm^3)

SAMPLE IGCSE EXPERIMENT

0610/63/o/n/23

Humans can use the energy realised during respiration to exercise. Plan an
investigation to determine the effect of the exercising at different intensities on
breathing rate.

Independent variable: Intensity of exercise (Least to Most intense: Walking, Jogging, Jump
rope, Jumping jacks and Running)
Dependent variable: Pulse rate of participants
Controlled variable: Time duration of the exercise, gender and fitness level of participants

Method:

1. Have 5 participants of the same gender and fitness level

2. 5 participants do different exercises of the different intensities
3. Use a stopwatch and set it to 5 minutes, have the participants begin the exercise at the
same time
4. After 5 minutes, measure the pulse rate of the participants for 1 minute

Repeat experiment to obtain average results

Safety: Stretch beforehand to reduce risk of injury, and do exercises carefully.