Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

TOPIC 1: Key Concepts in Biology
➢ CELLS & MICROSCOPY:
 Cells either can be eukaryotic (complex & multicellular, e
...
animal/ plant cells) or prokaryotic
(simple & single-celled, e
...
bacteria)
...

 ANIMAL CELLS: nucleus (genetic material in chromosomes & controls activity), cytoplasm (gellike substance where chemical reactions occur using enzymes), cell membrane (hold cell together &
controls what enters/ leaves), mitochondria (where aerobic respiration occurs to fix energy) &
ribosomes (involved in protein synthesis)
...

 Most cells in an organism are specialised, thus their structure helps them carry out a specific
function
...

 HOW CELLS HAVE SPECIALISED/ DIFFERENTIATED:
1
...

2
...

3
...

4
...

5
...

6
...

7
...

8
...

 Gametes (sex cells) have haploid nuclei – this means they have half the number of chromosomes in
normal body cell
...

 Microscopes can either use light or electrons; they are used to view individual cells or subcellular
structure that cannot be seen with the naked eye
...

 LIGHT MICROSCOPES (est
...
g
...

 ELECTRON MICROSCOPES (est
...
g
...
2nm
...
Add a drop of water to a clean slide for securing the specimen
...
Cut an onion, separate into layers & use tweezers to remove epidermal tissue from the bottom
...
Using tweezers, place epidermal tissue on water on slide
...
Add a drop of iodine solution as a stain (e
...
methylene blue for DNA or eosin for cytoplasm)
...
Place a cover slip over the upright next to the water, then carefully lower using a mounted
needle (avoid air bubbles)
...

OBSERVING A SPECIMEN:
1
...

2
...

3
...

4
...

5
...

6
...

CALCULATING MAGNIFICATION:
total magnification = eyepiece lens magnification x objective lens magnification
magnification = image size / real size

➢ BIOLOGICAL MOLECULES & TRANSPORT

IN CELLS:
 Living things produce enzymes to act as a biological catalyst for the reactions inside a human body;
they reduce the need for high temperatures & only speed up useful reactions
...

 Catalysts are substances that increases the rate of reaction, without being changed or used up
...

 Enzymes are said to have high specificity for their substrate, as shown by the ‘lock & key model’
...

 Enzymes need the right (optimum) conditions to work best, including: temperature (if it gets too
hot, the enzyme’s bonds break, it denatures & the active site changes shape; however, if it’s too low,
not enough heat energy is convert to kinetic energy for the enzyme & substrate to collide), substrate
concentration (rate of reaction increases to point until it flattens because the active sites are full & it
become saturated), pH (if too high or low, the bonds between the amino acids is broken down &
the enzyme is denatured) & inhibitor molecules (block the active site & change its shape)
...

 HOW TO INVESTIGATE THE EFFECT OF pH ON AMYLASE: this enzyme catalyses the
breakdown of starch in maltose
...

1
...

2
...

3
...
Wait 5 minutes
...
Using a different syringe, add 3cm3 of starch solution
...
Immediately mix contents & start stop clock
...
Use continuous sampling to record how long it takes to break down the starch by dropping
some in the spotting tile every 30 seconds with a pipette, until no changes of colour
...
Repeat with buffer solutions at different pHs
...
Remember to control variables to make it a fair test
...
g
...

Enzymes are also used in synthesis reactions (opposite of breakdown reactions)
...

HOW TO TEST FOR REDUCING SUGARS (e
...
glucose):
1
...

2
...

3
...

4
...

5
...
The further the
colour change, the higher the concentration of reducing sugar (blue to green to yellow to red)
...
Transfer 5cm3 of food sample to a test tube
...
Add a few drops of iodine solution (iodine dissolved in potassium iodide) & gently shake
...
If starch is present, colour will change from brown orange to blue-black
...
Transfer 2cm3 of food sample to a test tube
...
Add 2cm3 of potassium hydroxide solution to make it alkaline
3
...

4
...

HOW TO TEST FROM LIPIDS (emulsion test):
1
...

2
...

3
...

4
...
If lipids are present, they will precipitate out of the liquid as a milky emulsion (more lipids, more
noticeable)
...

Calorimetry can be used to see how much energy is contain in food by burning it & measuring heat
energy transferred
...

HOW TO DO CALORIMETRY:
1
...

2
...

3
...
Set food on fire with Bunsen burner
...
Immediately hold under water & keep relighting until the food will not catch fire again
...
Measure temperature of water again & record temperature change
...
2

 Diffusion is the spreading out of particles from an area of high concentration to low concentration
– it is passive (does not require energy), for gases & liquids, & along the concentration gradient
...

 Osmosis is the net movement of water molecules from an area of high concentration of water to
low concentration of water across a partially permeable membrane (i
...
low concentration of solute
to high) – it is also passive
...
It can either be isotonic (equal concentration), hypertonic (when one
solution is more concentrated/ stronger) or hypotonic (when one solution is more dilute/ weaker)
...

 Active transport is the movement of particles from an area of low concentration to high
concentration (against the concentration gradient) using energy transferred by respiration
...

 HOW TO INVESTIGATE OSMOSIS IN PLANT CELLS:
1
...

2
...

3
...

4
...

5
...

6
...

7
...

 Dependent variable (measured): cylinder mass & independent variable (changed): sucrose
concentration
...
When it gained
mass, the solution was hypotonic; when mass did not change, the solution was isotonic; & when it
lost mass, the solution was hypertonic
...

 CALCULATING PERCENTAGE CHANGE IN MASS:
percentage change in mass: ((final mass – initial mass)/ initial mass) x 100

TOPIC 2: Cells & Control
➢ CELL DIVISION & STEM CELLS:
 Nuclei store genetic material in the form of chromosomes
...

 Gametes have haploid cells with one copy of each chromosome (half the number of chromosomes)
...

 Body cells in multicellular organisms divide to produce new cells by the cell cycle
...

 Cell cycle begins with a stage of cell growth & DNA replication (interphase) & is followed by a stage
of cell division
...

 HOW THE CELL CYCLE WORKS:
 INTERPHASE: cell grows, increases number of organelles & duplicates DNA to form x-shape
connected by the centromere (chromosomes are counted by the centromeres)
...
PROPHASE (mitosis begins): chromosomes condense (shorten & fatten) & nuclear membrane
breaks down so chromosomes lie free in the cytoplasm
...
METAPHASE: chromosomes line up in the middle of the cells & attach to spindle fibres by
their centromeres
...
ANAPHASE: spindle fibres coil & shorten, splitting centromeres & pulling chromosomes to
opposite sides of the cell
...
TELOPHASE (mitosis ends): nuclear membranes form around each set of chromosomes to
become two nuclei
...
CYTOKINESIS: before telophase ends, cytoplasm & cell membrane divide to form two
separate cells
...

 Mitosis has many uses, including: growth, replacing damaged cells & asexual reproduction
...
Plant & animals grow & develop due
to cell division (by mitosis) or cell differentiation (when a cell becomes specialised so it can work
more efficiently)
...

 Animals tend to grow while they are young, until they reach full growth & stop; cell division occurs
at its fastest rate while they are young & most cell division is use for repair when they grow up
...

 Plant’s growth in height is mainly due to cell elongation
...
Plants grow continuously & continue to differentiate
...

 The tumour can invade & destroy surrounding tissue
...

 Problems occur when there is a change in the genes that controls cell division (mutation)
...
g
...

 Measurements are taken after birth, including head circumference, height, & mass (then plotted)
...
g
...

 Stem cells are undifferentiated cells; hence they divide to produce more undifferentiated cells –
which can be given instructions to develop into different types of cells
...

 Adult stem cells (found in certain places, like bone marrow) are less versatile (known as multi/
pluripotent) as they as used for repair & replacement
...

Embryonic stem cells can be stimulated into differentiation & are easier to grow in culture
...

 However, the embryos are normally excess from fertility clinics (otherwise destroyed)
...


➢ NERVOUS CONTROL:
 Multicellular organisms respond to stimuli (changes in the environment) to survive by
communication through the endocrine & nervous system so you can react & coordinate your
behaviour
...
g
...

 The central nervous system is where all the information from receptors is sent & reflexes are
coordinated
...

 In mammals, the CNS transmits information by electrical impulses via the sensory & motor
neurones very quickly
...

 Effectors are muscles or glands that respond to nervous/ electrical impulses from the neurones &
coordinate a response; the muscles contracts & the glands secrete hormones
...

 Sensory neurones carry electrical impulses from the sensory receptors to the CNS
...
The impulse is then sent along one short axon from the cell body to the CNS
...
They have many short dendrites to carry the impulse from the sensory neurone to its cell
body & an axon to carry the impulse from cell body to motor neurones
...
They have many short
dendrites to carry impulses from the CNS to the cell body & a long axon to carry the impulse to the
effector cells
...

 Synapses are the gaps between neurones
...

 These synapses slow down transmission because the neurotransmitters must diffuse across the gap
...
They are
quick because they bypass your brain (only use spinal cord or unconscious part of brain)
...

 HOW RELFEX ARCS WORK:
1
...

2
...

3
...

4
...

5
...

 Brain is part of the CNS – it is made up to billions of interconnected neurones
...

 The brain is made of different regions, including: cerebrum (largest part, separated into two cerebral
hemisphere – where right side controls left muscles & vice versa), cerebellum (found at the back of
the brain) & the medulla oblongata (found at base of brain/ top of spinal cord)
...
g
...

 Investigating the function of the brain involves surgery or scanners
...
However, if the
scan shows the damaged brain structure, the loss of function can be explained
...
Before the scan, the patient is injected
with a tracer (radioactive chemical) – which moves around the body & collect in certain areas
...

 Treating problems in the CNS is difficult & comes with its own set of problems, including:
neurones do not repair themselves; some areas are not easily accessible, & treatment could lead to
permanent damage (e
...
paralysis)
...
If the neck of the
spinal cord is damaged, you risk becoming a quadriplegic (arms & legs paralysed)
...

 HOW TO LABEL THE EYE:
1
...

2
...

3
...

4
...

5
...

6
...

7
...

 Retina contains two types of photoreceptors (cones & rods)
...
Rods are sensitive to light
intensity (black & white), work best in dim light & is found at edge of retina
...

 The lens is connected to the suspensory ligament – which is connected to the ciliary muscle
...

 Accommodation is a reflex action to look at near & distant objects by changing shape of lens (closer
the object, more refraction needed)
...
Ciliary muscles contracts – which slackens the suspensory ligament
...
Lens becomes more rounded
...
Amount of light it refracts is increased
...
Ciliary muscles relax – which pulls the suspensory ligament tight
...
Lens becomes less rounded
...
Amount of light it refracts is decreased
...

 Long-sightedness is when you cannot focus on near objects
...
This
can be corrected with convex/converging lens
...
Either eyeball is too long, or lens is
too curved; this causes the image to focus in front of the retina (too much refraction)
...

 Cataracts form when protein builds up on lens & it becomes cloudy so lens cannot enter normally
...
It can be
replaced surgically with an artificial one
...
It is inherited & sex-linked
...


TOPIC 3: Genetics
➢ REPRODUCTION, DNA & PROTEIN
SYNTHESIS:
 Sexual reproduction is where genetic information from a mother & a father organism is combined
to produce an offspring that is genetically different to the parents
...
In animals, they are egg & sperm
cells, & in plants, its pollen, & ovules
...

 At fertilisation, the male & female gamete fuse to produce a fertilised egg – known as a zygote
...
Next, the
zygote undergoes mitosis & develops into an embryo
...
The mixture of
chromosomes produces variation in the offspring
...
Unlike mitosis, it does not produce identical cells, there are
two cell divisions & it produces haploid cells
...

 HOW CELLS DIVIDE BY MEIOSIS:
1
...

2
...
Pairs are pulled apart, so each new cell only has one copy of each chromosome – now haploid
cells (some father & some mother chromosome in each new cell as its mixed up)
...
SECOND DIVISION (PMAT): chromosomes line up in the centre of the cell again (only one
copy)
...
Arms of chromosomes are pulled apart
...
At the end, you get four haploid daughter cells (the gametes) with a single set of chromosomes
...

 Asexual reproduction involves one parent, so the offspring is genetically identical
...
Sexual reproduction involves two
parents
...

 Asexual reproduction has advantages, including: only one parent required (no mate) & faster
reproductive cycle
...

 Sexual reproduction has advantages, including: genetic variation in offspring & allows for natural
selection (& leads to evolution when they breed)
...

 DNA (deoxyribonucleic acid) is the chemical that all genetic material is made from, so it determined
your inherited characteristics
...


 DNA is coiled up to form the ‘arms’ of chromosomes (found in the nucleus of eukaryotic cells)
...

 Genes are small section of DNA – which codes for a sequence of amino acids (protein)
...

 DNA is a polymer made up of two strands twisted together – known as a double helix
...
Each nucleotide is made up of a sugar molecule, phosphate
molecule & one of four bases
...
The base always
attached to the sugar – which is always attached to a phosphate
...

Each base in the DNA strands links to a base on the opposite helix – C with G & A with T
...
The base pairs are held together by weak hydrogen bonds
...
Mash the soft fruit & put in beaker with detergent & salt (detergent breaks down cell membrane
& salt stick DNA together)
...
Heat gently (50o) to denature enzymes that could destroy DNA
...
Filter mixture to get rid of insoluble bits of cell
...
Using a pipette, add ice-cold alcohol (ethanol); DNA is not soluble in alcohol, so it precipitates
...
Remove string white precipitate with glass rod
...

 DNA controls protein synthesis in cells
...
The amino acids fold up to give each protein
different, specific shape, thus different functions (e
...
enzymes)
...
Each amino acid is coded for by a sequence
of three bases – known as a base triplet
...

 Many regions of the DNA are non-coding, so they do not code for amino acids
...

 Mutations are rare & random changes to an organism’s DNA base sequence – it can be inherited
...
It can also occur in the non-coding region
...
This would change the amino acids sequence, &,
potentially, the shape of the final protein (& its function)
...

 Proteins are made two stages
...

 DNA is stored in the cell nucleus & to make a protein, information in the DNA must be taken to
the ribosome in the cytoplasm; however, it is too big
...

 mRNA is also a polymer of nucleotide, but it is shorter than DNA & only a single strand
...

 mRNA is made by copying the DNA base sequence of a gene; the RNA nucleotides are joined by
the enzyme RNA polymerase – this is the process of transcription
...
RNA polymerase binds to a region of non-coding DNA in front of a gene
...
Two DNA strands unzip, & the RNA polymerase moves along one str& & uses the coding
DNA in the gene as a template to make mRNA (base pairing between DNA & RNA ensure
mRNA is complementary to gene)
...
Once made, the mRNA molecule moves out of the nucleus & joins the ribosome in the
cytoplasm
...

HOW TRANSLATION WORKS:
1
...

2
...

3
...

4
...
Once the amino acid is
deposited, the empty tRNA molecule moves away again
...
This is because, before transcription, the RNA
polymerase binds to a non-coding region
...

This could affect how much mRNA is transcribed, & therefore how much protein is produced
...


➢ GENETIC DIAGRAMS & INHERITANCE:
 Your genes control the characteristics you develop; most characteristics are controlled by multiple
genes interacting (different genes control different characteristics)
...

 You receive one allele from each parent
...

 If the allele is heterozygous, only one determines the characteristic
...
Hence, the dominant allele is expressed when the allele is heterozygous or
homozygous, but the recessive is only shown when homozygous
...
g
...
g
...

 Monohybrid inheritance is single gene inheritance (only one gene determines your characteristic)
...

 Genetic diagrams are used to predict as ratios & explain outcomes of monohybrid crosses; it can be
used to work out the probability of have offspring with certain characteristics
...

 HOW TO CONSTRUCT A PUNNETT SQUARE:
1
...

2
...

3
...





























4
...

HOW TO CONSTRUCT A GENETIC DIAGRAM:
1
...

2
...

3
...

4
...

Family pedigrees show how characteristics (or disorders) are inherited in related group of people
...
Carriers are
organisms with the allele who do not show the symptoms (heterozygous)
...

Gregor Mendel noted how characteristics in his plants were passed on between generations on his
garden plot in the monastery & it was later published in 1866 (foundation of modern genetics)
...
All the offspring were tall, so they held the
hereditary unit for dwarf plants (TT x tt = Tt)
...
Then, he knew the
hereditary unit/ allele for tall plants was dominant
...
At the time, he received no credit as no one knew about DNA, genes or chromosomes
(no microscopes)
...

Gametes are haploid, so they only contain one sex chromosome
...

Whether you are male or female, depends on whether a sperm that fertilises the egg had a X or Y
chromosome – this is known as sex determination
...

A characteristic is sex-linked if the allele that codes from it is found on the X or Y chromosome
...
Since men
only have one X chromosome, often they one carry one allele for a sex-linked gene
...

Disorder caused by faulty sex chromosome alleles are known as sex-linked genetic disorders
...
g
...
The alleles are written
as XNXN or XnY – where the allele is written in superscript
...
These alleles can be codominant with each other so both alleles of the gene are
expressed in the phenotype
...
The gene for blood type has three
different alleles (IO, IA & IB)
...

The alleles, IA & IB, are codominant with each other
...
However, the allele IO, is recessive &
only expressed if you have the homozygous genotype
...

Most characteristics are determined by a mixture (e
...
height, intelligence & health)
...
As genes code for sequence of amino acids to make protein, gene mutations
can lead to a change in the protein coded for
...

The Human Genome Project was an international collaborative research project to find every
human gene
...
It has helped to identify 1800 gene-related diseases
...
g
...
Doctors could
provide those susceptible with tailored advice on dieting & lifestyle choices to avoid
...

Testing & treatment: gene therapy is when a working copy of a gene is introduced into cells to treat
a genetic disease
...
It may be possible to develop better treatment
...
This knowledge can be used to create medicine personalised to the person & their
combination of alleles
...

Genetic analysis raises ethical issues, including: increased stress level if you know you are
susceptible, pressure to not have children if you know you are a carrier, & discriminate against those
with genetic likelihood from employers & life insurers
...
The theory of natural selection was created by
Charles Darwin to explain how evolution works
...
Individuals in a population show genetic variation by different alleles (from mutations)
...
Selection pressures (e
...
predation, competition for resources & disease) affect organisms’
chance for surviving & reproducing
...
Individuals with the characteristics best adapted to the selection pressures have a better chance
of surviving – & thus, breed successfully
...
Useful alleles are passed on to next generations
...
Individuals that are worse adapted to selection pressures are less likely to survive (& breed)
...
Beneficial characteristics become more common in the population over time
...
Antibiotics are used to kill bacteria or prevent
reproduction (selection pressure)
...
This advantageous characteristic gives a high
chance of survival in a host
...
The allele can either by passed on by reproduction by mitosis
or bacterial conjugation – where alleles are passed on by transferring plasmids
...
g
...

 Fossils are also evidence for evolution
...
They are commonly found in rocks (the deeper the rocks, the older the fossil)
...
It shows how species have changed &
developed over billions of years
...
On his boat the HMS beagle, he spent 5 years on a voyage around the world
studying animals & plants
...
Also, he noticed these characteristics
could be passed on to offspring
...

 Alfred Russell Wallace was working at the same time as Darwin & came up with the idea of natural
selection independently
...
Wallace’s observations
provided evidence (e
...
warning colours to deter predators)
...
We now understand that all
life changes by evolution & it suggests that we all descend from a common ancestor
...
Classification: classify based on how closely related (come from a common ancestor)
...
Antibiotic resistance: understanding that bacteria can evolve to being resistant, so we finish
antibiotic courses & develop new ones
...
Conservation: understanding the importance of genetic diversity & how it helps populations
adapt to changing environments
...
When hominid skulls are
arranged in chronological order, they become larger, less ape-like & increase in cranial capacity
(space taken up by brain in skull)
...
“Ardi” was an Ardipithecus ramidus found in Ethiopia 4
...
2m)
...
“Lucy” was an Australopithecus afarensis found in Ethiopia 3
...

3
...
“Turkana Boy” was a human-like
homo erectus from 1
...

 To conclude, the Australopithecus & Ardipithecus are more ape-like, while the homo species are
more human-like
...
g
...
g
...
g
...

 As Homo species evolved, their brains got larger, so their tools got more complex
...

 HOW TOOLS HAVE DEVELOPED:
1
...
5-1
...
They could be used to break bones or scrape the meat off
...
Homo erectus (lived 2-0
...

They could be used to hunt, dig, chop & scrape meat off the bone
...
Homo neanderthalensis (lived 300,000-25,000 years ago): tools included flint tools with sharp &
pointy edges & wooden spears
...
Homo sapiens (modern humans – first appearing 200,000 years ago): other than flint tools, they
made pointed tools, like arrowheads, fishhooks, & needles around 50,000 years ago
...
They also use
stratigraphy (study of rock layers) – where the deeper layers are older with older fossils
...
Carbon-14 dating is also used –
it is based on the idea that all carbon-based material contains a small amount of radioactive C-14
...

 Other issues include that organism with soft material decay completely & fossil can be damaged by
geological activity
...
Every pentadactyl limb has similar bone structure, but different function (e
...
flying,
swimming, digging, walking or dexterity)
...
Starts with the humerus in the arms & femur in the legs
...
Next is the radius & ulna in the arms & tibia & fibula in the legs
...
Then, the carpals in the hand & tarsals in the feet
...
The metacarpals in the hands & metatarsals in the feet with phalanges at the end of both
...

Traditionally, organisms were classified by observable similarities & differences
...

Organism were separated by kingdoms, then phylum, then class, then order, then family, then
genus, then species (each subdivision was smaller & more specific)
...

Over time, technology has developed further & our understanding of things like biochemical
processes & genetics has improved
...

This led to a proposal of the three-domain system of classification by Carl Woese
...
He proposed it be split into Archaea (look similar with different genes) & Bacteria (true
bacteria)
...

Then it is subdivided into smaller groups using the five-kingdom classification
...
These characteristics
are useful or attractive (e
...
animals with more meat/ milk, crops with disease resistance, dogs with
gentle temperament or plants that produce bigger fruit)
...

 HOW SELECTIVE BREEDING WORKS WITH ANIMALS:
1
...

2
...

3
...

4
...

 HOW SELECTIVE BREEDING WORKS WITH PLANTS:
1
...

2
...

3
...

4
...

 A problem is the reducing of the gene pool (the number of different alleles in a population)
...
Inbreeding
can cause health problems as there is more chance of inheriting harmful genetic defects (e
...

difficulty breathing for certain species of dog)
...

 Also, if a new disease appears, most will die
...

 A tissue culture is when cells are grown in/ on an artificial growth medium (e
...
agar jelly or liquid
broth) – which contains nutrients & growth hormones
...
However, it can only produce cells or tissues from animal cells
...
The plants produced are clones (genetically identical) so they have the same beneficial
features
...
Choose a plant based on its characteristics
...
Remove several small pieces of tissue – this is known as the explant (best results from fastgrowing roots or shoot tips)
...
Grow tissue on growth medium in aseptic condition (prevent growth of microorganisms)
...
As roots & shoots grow, it can be transferred to a potting compost to continue growing
...
It
allows you to view the effects of a certain substance or environment on the cells of a single tissue
(without complications of other bodily processes)
...

 HOW ANIMAL TISSUE CULTURES WORK:
1
...

2
...

3
...

4
...

5
...

 Genetic engineering is the transferral of a useful gene from one organism’s genome to another to
introduce a desirable characteristic
...

 Genetic engineering has many uses, including: producing human insulin for diabetics, improving
size or quality of crops, making crops resistant to insects, herbicides or diseases, & sheep & cows
have been used to produce useful human protein in their milk (antibodies can be used in treat
arthritis, some cancers & multiple sclerosis)
...
Gene is cut out using restriction enzymes – which recognise specific sequences of DNA & cut at
that point
...

2
...
g
...

3
...
They are mixed with ligase
enzymes which join them together to produce recombinant DNA
...
The recombinant DNA in inserted into other cells (e
...
bacteria)
...
Cells can use inserted gene to produce the protein the gene codes for
...
g
...
g
...

 However, it also has risks, including: how hard it is to predict the effects (e
...
killing embryos or
later health problems), adversely affecting food chain (human health) or transplanted gene getting
out into environment (e
...
herbicide-resistant gene getting picked up by weed)
...
GM
crops may be a way to increase that
...
g
...
Others have concerns, including: poverty
should be first priority, countries may become dependent on companies selling GM seeds, poor soil

will not even allow the GM crops to grow, & unknown long-term effects on human &
environmental health
...
Genes of Bt
toxin can be insert into crops & produced in stem & leaves
...
It would also reduce the need for chemical fertilisers
...

 There are also other methods of increasing food production, such as fertiliser
...
g
...
They replenish nutrients
after previous crop growth
...

 Biological control is another agricultural method
...
g
...
This has a long-lasting effect & is less harmful to the
environment
...


TOPIC 5: Health, Disease & The
Development of Medicine
➢ HEALTH & DISEASE:
 Disease is a condition where part of an organism does not function properly
...
World Health Organisation
(WHO) defines health as the state of complete physical, mental, & social well-being, & not merely
the absence of disease or infirmity
...
Otherwise, they are non-communicable & cannot spread
...

 When you are affected by another disease, you can be more susceptible to other diseases
...

 Pathogens (bacteria, viruses, fungi, or parasites are also known as microorganisms or microbes) are
organisms that cause diseases in plants & animals
...
They grow exponentially by reproducing rapidly
...
Examples of bacterial include
Tuberculosis by Mycobacterium tuberculosis (this causes coughing & lung damage & is an airborne
disease, so patients must isolate themselves); Cholera by Vibrio cholerae (this causes diarrhoea &
severe dehydration & is spread by contaminated water, so you must provide access to clean water);
& stomach ulcers by Helicobacter pylori (this causes stomach pain, nausea & vomiting as the
stomach lining becomes inflamed & damaged so the stomach acid penetrates it to form an ulcer
...

 Viruses are not cells – they live inside your cells & replicate using the cells’ machinery
...
Ebola is a viral disease that causes
haemorrhagic fever (bleed internally or from eye, ear or mouth) – & it is spread by coming in
contact with infected bodily fluid
...

 Protists are mostly single-celled eukaryotes, such as parasites
...
Malaria is a disease caused by
the malarial protist – which has part of its life cycle inside a mosquito
...
It can cause,
damage to RBCs, liver, & fever
...

 Fungi is the final pathogen – they are either single-celled or have a body made of hyphae (threadlike structure)
...
An example is Chalara Ash Dieback where ash trees
are infected, & they lose their leaves & get bark lesions; the fungi is airborne
...

 HOW PATHOGENS CAN SPREAD:
1
...
g
...
Airborne/ carried in the air (e
...
tuberculosis or Chalara ash dieback)
3
...
g
...
Infected bodily fluids including blood, vomit, saliva, or faeces (e
...
Ebola)






















5
...
g
...
Common ones include
Chlamydia & HIV/AIDs (protected by condoms or abstinence)
...
It can cause discharge, itchiness, or
bleeding (sometimes infertility) – & in some cases, it can be passed on through childbirth
...
You get a screening for early detection &
treatment to prevent unknowingly spreading it
...
It can be controlled by antiretroviral drugs to prevent replication inside cells
...
They become vulnerable to
opportunistic infections they could otherwise fight off
...
Screening & treatment
are important as medicine can reduce risk of spreading by sex or during pregnancy
...
To reproduce, they must infect a
host cell – this is the start of their life cycle
...

HOW VIRUSES REPLICATE THROUGH THE LYTIC CYCLE:
1
...

2
...

3
...

4
...

HOW VIRUSES REPLICATE THROUGH THE LYSOGENIC CYCLE:
1
...

2
...

3
...

4
...
g
...

Plants have chemical (some can be used as drugs) & physical defences against pathogens & pest
...
Antiseptics: kill bacteria & fungal pathogens
...
Poisons: deter pests from feeding on leaves
...
Odours: deter pests
...
Waxy cuticle: stops pathogens entering, water collecting & pests damaging
...
Cellulose cell: wall acts as a barrier
...

HOW PLANT DISEASE IS DETECTED IN THE LAB:
1
...

2
...

3
...

4
...

5
...

6
...

HOW PLANT DISEASE IS DETECTED IN THE FIELD:
1
...


2
...

3
...
g
...


➢ FIGHTING DISEASE:
 The body’s first line of defence is non-specific & are known as ‘barriers’; they are either chemical or
physical – like plant defences
...
Hydrochloric acid in the stomach kills pathogens
...
Enzymes called lysozymes kill pathogens (found in tears, saliva, & lungs)
...
Skin: acts as a barrier & uses blood clots to quickly seal cuts & keep out pathogens
...
Mucus: (from goblet cells) is sticky & traps pathogens
...
Hairs: (in nose & ears) also trap pathogens
...
Cilia: (microscopic hair-like structures) moves mucus containing pathogens
...
The most important part is
the white blood cells – which travel through the blood stream patrolling for pathogens
...

 Some white blood cells engulf foreign cells & digest them – this is known as phagocytosis (nonspecific response)
...
Whereas B-lymphocytes are
involved in specific immune response – where they produce proteins called antibodies rapidly that
bind to the antigens on pathogens
...

 When a pathogen first enters the body, the immune response is slow, since there are not many Blymphocytes that can make the antibodies needed to bind to the new antigen
...
While producing antibodies, they also produce memory lymphocytes that ‘remember’
specific antigens & stay in the body for a long time
...
The secondary immune response is faster &
stronger, so the body gets rid of the pathogen before you show symptoms; this is shown on a graph
(concentration of right antibodies in blood by time) by a steeper line
...
The pathogens are antigenic, so it stimulates your white blood cells to produce
antibodies specific to the vaccine
...

 If the pathogen is too potent, they would inject the antibodies instead
...
However, it also has disadvantages, including: not
working, having a bad reaction, & fear of needles
...
Mouse is vaccinated with desired antigens on pathogens
...
Spleen cell/ B-lymphocytes produces antibodies
...
Antibodies are fused with myeloma/tumour cells to form hybridoma cells
...
These are grown in labs
...
When they divide, they produce clones of a single B-lymphocyte –
which produce monoclonal antibodies that are (mono) specific to that antigen
...

 Monoclonal antibodies have many uses, such as pregnancy tests (detects hormone HCG found in
pregnant women’ urine), diagnosing & treating cancer (detects cancer cells antigens/ tumour
markers), & finding blood clots
...
Test stick: section where you wee on has monoclonal antibodies with blue beads attached; the
test strip has more monoclonal antibodies stuck down (cannot move)
...
Positive result: hormone binds to monoclonal antibodies & urine moves up the stick (carrying
hormone & blue beads); hormone binds to monoclonal antibodies on test strip
...

3
...

4
...
This causes it to turn blue
...
Monoclonal antibodies are labelled with a radioactive element
...
Labelled antibodies are given through drip & travel around through bloodstream
...
When they encounter cancer cells, they bind to tumour markers
...
Picture is taken with a special camera that detect radioactivity (seen as bright spot); this shows
the doctor where it is, the size & how it is spreading
...
g
...
This is good because it does not harm normal body cells
...

 To find blood clot, the monoclonal antibodies are developed to bind to the proteins in blood that
join to form a solid mesh
...
This is useful to easily find &
get rid of blood clot before it harms patient
...

 The preclinical testing involves tests on human cells & tissue, then on live animals
...
It is
tested on animals to assess efficacy (whether it works), toxicity (how harmful it is) & optimal dose
(how much & how often); however sometimes their physiology is different
 Next, in clinical testing, the drug is tested on healthy volunteers to check to any harmful side effects
when the body is work normally
...
If the results are good, they test on patients with the illness
...
Placebos are substances that look like the drug but do nothing (e
...
sugar pill)
...
To prevent false claims, results of drug testing & trials undergo peer review first
...


 It is really important to test drug for safety (example is thalidomide which was originally tested for
sleeping pills, but later proved effective in relieving morning sickness – but it caused abnormal limb
development as it could get through the placenta)
...
Antibiotics have
no effect on viruses as they are not cells (instead, you need antiviral drugs)
...

 Microorganisms can be grown/ cultured in a growth medium (containing carbohydrates, minerals,
proteins, & vitamins needed to growth) – which is either solid agar jelly or nutrient broth solution
...

 To make an agar plate, hot agar jelly is poured into a shallow, round plastic petri dish
...

 While antibiotics kill bacteria inside the body, antiseptics kill those outside the body
...
After making an agar plate & adding bacterial solution (like above)
...
Place soaked paper discs in agar jelly (use sterile water as control)
...
As substance diffuses into the agar jelly, resistant bacteria will control to grow, but non-resistant
strains will die & leave a clear zone – known as the inhibition zone
...
Leave plate for 48 hours at 25oC (incubation)
...
More effective the substance is against bacteria, larger the inhibition zone
...
This is can be avoided by using aseptic techniques
...
Petri dish & growth medium must be sterilised using an autoclave – which uses high pressure &
temperature to kill unwanted microorganisms
...
Inoculating loop must be sterilised by passing through a hot flame (it must cool down first
before picking up bacteria or it could kill it)
...
Liquid bacterial cultures must be kept in culture vials with lids (only remove lids briefly)
...
Petri dish should be sealed to block microbes from air entering
...
Petri dish should be stored upside down to stop condensation falling onto agar surface
...
You can do it by eye or using the equation for area of a circle (through the transparent lid);
same equation is used for bacterial colonies
...

 Risk factors are linked to an increase in the likelihood that a person will develop a certain disease in
their lifetime
...
g
...
g
...
g
...

 Smoking is a major risk factor for cardiovascular disease (related to heart & blood vessels)
...
Nicotine increases heart rate, & thus blood pressure
...
Smoking also increases the risk of blood clots forming in the arteries – which also
blocks blood flow & increases the risk of heart attack/ stroke
...
This is because
the chemicals called carcinogens (found in tar) cause mutations in the genes that control cell
division – which leads to cancer (uncontrolled cell growth)
...
The enzyme in the liver break down alcohol, but the by-products
destroy the liver cells
...

Excessive alcohol is also a risk factor for cardiovascular disease
...
On the other hand, a diet that is high in fat & sugar can lead to being overweight & obese
(which is a risk factor for type 2 diabetes)
...
It is important to
maintaining a healthy weight or you could become overweight
...

HOW LIFESTYLE FACTORS HAVE AN IMPACT:
1
...

2
...

3
...

Obesity means being very overweight or having too much body fat; weight is affected by your
height & muscle mass (& more)
...

CALCULATING BODY MASS INDEX:
body mass index = mass (kg)/ (height (m))2
HOW TO ASSESS WEIGHT WITH BODY MASS INDEX:
1
...
5
2
...
5-24
...
Overweight: 25-29
...
Moderately obese: 30-39
...
Severely obese: 40+
If you eat a high fat & sugar diet & don’t exercise, you are likely to take in more energy than you
use
...
However, BMI
isn’t always a reliable measure if obesity since muscle has a higher mass than fat
...

CALCULATING WAIST-TO-HIP RATIO:
waist-to-hip ratio = waist circumference/ hip circumference
Higher ratio means you carry more weight around your middle – this is known as abdominal obesity
(when ratio is above 1
...
85 for women)
...
g
...

Cardiovascular diseases affect the heart or blood vessels; generally, it is associated with narrowing &
blockage of the arteries – which carry blood away from the heart
...
The fatty deposit can also
trigger blood clots – which completely block the flow of blood
...

In some cases, you can change your lifestyle to lower the risk (or as part of your treatment),
including: eating a healthy, balanced diet (which is low in saturated fat), exercising regularly, losing
weight or stopping smoking
...

HOW MEDICINE HELPS TREAT CVDs:
1
...
Also, the effect is not instant
...
Antihypertensives: reduce blood pressure to prevent damage of blood vessels, & thus, fatty
deposit build-up (e
...
Diuretics to flush out excess water, ACE inhibitors to relax blood vessels
or Beta blockers to cause heart to beat slower & less forcefully); however, its side effects include
headaches & dizziness
...
Anticoagulants: makes blood clots less likely to form so blood flow isn’t blocked; however,
patients are more prone to heavy bleeding (as blood clots are necessary for preventing excessive
bleeding), it increases risk of internal bleeding, &, if the injury is severe, significant blood loss
...

Another solution is heart surgery – which comes with the risk of bleeding, clots & infection
...

HOW SURGERY HELPS TREAT CVDs:
4
...
g
...

They are effective for a long time & recovery time is quick; however, the stent irritates the artery
& causes scar tissue to grow so the artery narrows again, & there’s the risk of blood clotting
...
Coronary bypass surgery (when many vessels are blocked): piece of healthy vessel is taken from
elsewhere & used to bypass blocked arteries
...

6
...
This is a life-saving surgery with some cons
like further treatment require to help blood circulation, long wait on donor list, & rejection
(when immune system recognises donor heart as foreign & attacks it)
...


TOPIC 6: Plant Structure & their
Function
 Photosynthesis is the process where green plants & algae produce ‘food’ in the form of glucose (a
sugar)
...

 HOW GLUCOSE IS USED IN PLANTS:
1
...
g
...

2
...

3
...

4
...

 The energy stored in the plant’s biomass is transferred through the food chain as animal eat them &
each other – this makes plants the main producers of all life on Earth
...
This is an endothermic process; this
means that energy is transferred from the surroundings to the process
...

 Limiting factors are factors that stop photosynthesis from happening faster, including: light
intensity, CO2 concentration & temperature
...

 HOW LIMITING FACTORS AFFECT RATE OF PHOTOSYNTHESIS:
1
...

2
...

3
...
This is because the reaction is catalysed by enzymes (which
work slowly at low temperatures, have an optimum temperature, & denature when it’s too hot)
...
g
...
You must add sodium hydrogen carbonate to release
carbon dioxide into the water (so it isn’t the limiting factor)
...

 HOW TO INVESTIGATE RATE OF PHOTOSYNTHESIS
1
...

2
...

3
...

4
...


 CALCULATING RATE OF PHOTOSYNTHESIS:
rate of photosynthesis (cm3/ min) = volume of oxygen produce/ time taken
 Rate of photosynthesis is directly proportional to light intensity (increase & decrease at same time &
rate)
...
However, really the light intensity is inversely proportional to the distance from the
light source – this is known as the inverse square law
...
It can be used a measure of light intensity
...
These
‘tubes’ go to every part of the plant (there are separated by the cambium)
...
They are made of elongated living cells & cellulose with small pores in the end
walls (known as a sieve tube element) to allow cell sap to flow through
...
g
...

 Xylem tube are involved in transpiration
...
They are
strengthened & waterproofed with lignin
...

 The transpiration is the loss of water from a plant’s surface by evaporation & diffusion (used to cool
plant down); whilst the transpiration stream is the movement of water & dissolved mineral ions
through the plant (from root to leaf)
...
Water from inside leaf evaporate & diffuses out (mostly through stomata)
...
This creates a tiny shortage/ pressure difference of water, so more water is drawn up through
the xylem to replace it by capillary action
...
This cause water to be drawn up from the roots – creating a constant transpiration stream
...

 Root hair cells are cells on the surface of the plant roots that grow into microscopic ‘hairs’ – which
stick out into soil
...
There is
normally a high concentration of mineral ions in the soil, so they are absorbed by active transport;
there is normally a high concentration of water in the soil, so it is absorbed by osmosis
...
Light intensity (brighter): stomata close as it gets darker, photosynthesis requires light so closing
prevents water escaping
...
Temperature (warmer): water particles have more energy to collide, so they evaporate & diffuse
out of the stomata
...
Air flow (windier): low air flow means the water vapour surrounds the leaf & doesn’t move –
this means there’s a high concentration inside & outside leaf so diffusion can’t occur (whereas
high flow creates a lower concentration outside)
...
Each stoma is
surrounded by two kidney-shaped cells called guard cells (the shape allows them to open & close the
stomata)
...

 Guard cells have adapted to have thin outer walls & thickened inner wall to make the closing/
opening mechanism work
...

 You can estimate rate of transpiration by measuring the uptake of water by a plant using a
potometer; this assumes that the water uptake is directly proportional to the water loss by leaves
(transpiration)
...

 HOW TO INVESTIGATE RATE OF TRANSPIRATION USING A POTOMETER:
1
...

2
...

3
...

4
...

 CALCULATING RATE OF TRANSPIRATION:
rate of transpiration (mm/ min) = distance moved by bubble/ time taken
 Another method to investigate rate of transpiration is using a plant shoot in a measuring cylinder
filled with water & a layer of oil (to prevent evaporation of water)
...

 The leaf is an organ made of several types of tissue
...
Waxy cuticle: first layer prevents water loss by evaporation & acts as protection
...
Upper epidermis: transparent to allow light through
...
Palisade mesophyll: contains chloroplasts (close to surface to get most light for photosynthesis)
...
Vascular bundle (xylem & phloem): support structure & deliver water & nutrients & remove
glucose
...
Spongy mesophyll: air spaces increase rate of diffusion for gas exchange
...
Lower epidermis: contains stomata (diffuses gases – carbon dioxide in & oxygen out) & guard
cells – which respond to environmental conditions
...
Also, the leaves are broad to increase surface area exposes to sunlight
...
They also flat to reduce diffusion distance
...
g
...
Adaptations affect a range of sections, including: size & shape of leaves, cuticle, & number
& position of stomata
...
Small leaves or spines to reduce surface area for water loss by evaporation
...
Spines to stop animals eating plant
...
Curled leaves or hairy leaves to reduce air flow by trapping water vapour – this reduce diffusion
...
Thick waxy cuticle to reduce water loss by evaporation
...
Few stomata or stomata that only open at night to prevent water escaping
...
Stomata sunken in pits to reduce air flow &, thus, diffusion of water
...
Widespread or deep roots to obtain more water
...
Plants need to light make food
through photosynthesis; they grow towards it to maximise the amount of light they receive – this is
known as phototropism
...
Growth in the roots & shoots (knowns as the meristems) is controlled by the plant
hormone called auxin (moves through plant in solution)
...

HOW PLANTS RESPOND TO PHOTOTROPISM (when exposed to light):
1
...
This
causes the shaded cells to elongate & bend towards the light
...
Negatively phototropic response in the roots as more auxin accumulates on the shaded side
...

Shoots that grow in the dark are tall & spindly as auxin in the tips make all sides elongate quickly –
taller plants have a better chance of finding light
...
Negatively gravitropic response in the shoots as more auxin accumulates on the lower side due
to gravity
...

2
...
This causes the lower side’s cells elongation to be inhibited & bend downwards
...

You can investigate the effect of gravitropism of plant growth using a clinostat – which rotates to
avoid the effect of gravity (unable to know which way is which)
...

Plant hormones can be extracted & used commercially in agriculture (farming) or horticulture
(gardening); artificial/ synthetic versions can also be made
...

While auxin & gibberellin are plant growth hormones, ethene is a ripening hormone produced by
aging parts of a plant
...
AUXINS as selective weed killers: weeds in crop fields are broad-leaved (unlike grass & cereal)
so selective weed killer can be developed using auxin; this is done by disrupting normal growth
pattern & killing them
...
AUXINS as rooting powder: cutting (part of another plant) normally don’t grow when put in
soil but adding rooting powder allows it to produce roots rapidly & grow as a new plant; this
allows clones to be produced quickly
...
GIBBERELLINS to control flower/ fruit formation: use to make plants flower earlier or under
conditions they normally wouldn’t or to reduce flower formation (can improve fruit quality)
...
GIBBERELLINS to control seed germination: makes seed germinate at any time of the year
(normally need to go through certain conditions first) or all at the same time
...
GIBBERELLINS to produce seedless fruit: fruits with seeds in the middle normally only grow
on flowering plants that have been pollinated by insects (otherwise fruits & seeds don’t grow);
adding gibberellins can allow unpollinated flower to grow fruit, but the seeds don’t
...
ETHENE to speed up fruit ripening (either on plant or on transport to shops): ethene gas can
be added later to unripen fruit (firmer & less easily damaged) or ripening can be delayed in
storage by blocking ethene’s effect or reduce amount of ethene produced with chemicals
...
The endocrine
system is made up of (endocrine) glands that produce & secrete hormones in response to stimuli
...
Pituitary gland (master gland located in brain): produces many hormones to regulate body
conditions – including hormones that direct other glands to release hormones
...
Thyroid gland (located in neck): produces thyroxine – which is involved in regulating rate of
metabolism, heart rate & temperature
...
Pancreas (located in centre of abdomen): produces insulin & glucagon – which is used to
regulate blood glucose levels
...
Adrenal gland (located above the kidneys): produces adrenaline – which is used to prepare the
body for the ‘fight or flight’ response
...
Ovaries (females only): produce oestrogen– which are involved in the menstrual cycle
...
Testes (males only): produce testosterone – which controls puberty & sperm production
...

 Adrenaline is released by the adrenal glands in response to stressful or scary situations
...

The fight or flight response is a result of increasing the supply of oxygen or glucose to cells
...
Heart: adrenaline binds to specific receptors causing the heart contracts more forcefully &
frequently, so the heart rate & pressure increases; this causes the blood flow to muscles to
increase & they receive more oxygen & glucose for increased respiration – which fixes extra
energy
...
Liver: adrenaline binds to specific receptors causing liver to break down its glycogen stores to
release glucose; this causes the blood glucose levels to increase, so more glucose is transported
to cells through blood & used to fuel muscular contraction
...

 Thyroxine is released by the thyroid gland to regulate the basal metabolic rate – which is the overall
rate at which chemical reactions occur in the body when it is at rest
...

 HOW THYROXINE REGULATES BY NEGATIVE FEEDBACK:
1
...

2
...


 Underactive thyroids can cause weight gain as less thyroxine is produced so the basal metabolic rate
decreases
...

 The menstrual cycle is a monthly sequence of events where the female body releases an egg/ ovum
& prepares the uterus/ womb in case the egg is fertilised
...

 HOW THE MENSTRUAL CYCLE WORKS:
1
...

2
...

3
...

4
...

 There are four hormones that interact with each other & inhibit the release of other hormones,
including: oestrogen (which stimulates growth of endometrium), progesterone (which maintains the
endometrium), FSH (follicle stimulating hormone causes follicle – which is the egg & surrounding
cells – to mature in ovaries), & LH (luteinising hormone stimulates ovulation)
...
FSH is produced by the pituitary gland causing the follicle to mature in one of the ovaries; it also
stimulates the ovary to produce oestrogen
...
Oestrogen is produced by the ovaries causing the endometrium to thicken & grow; this
stimulates a LH surge (& inhibits FSH)
...
LH is produced by the pituitary gland causing the follicle to rupture & be released (ovulation);
this stimulates remains of follicle to develop in a corpus luteum
...
Progesterone is released by the corpus luteum after ovulation causing the endometrium to be
maintained for the second half of the cycle; it inhibits the release of FSH & LH
...
When progesterone levels fall (& oestrogen levels are low), the endometrium breaks down again;
low levels of progesterone allow FSH to increase so the cycle restarts
...
If a person is infertile, they can’t
reproduce naturally (e
...
low FSH levels prevent eggs from maturing)
...
Clomifene therapy: women who don’t ovulate or don’t ovulate regularly can take the drug
clomifene; this works by causing more FSH or LH to be released to stimulate eggs maturation &
ovulation
...

2
...
FSH & LH are
given before egg collection to stimulate egg production (so more than one can be collected)
...
The excess egg & sperm cells can be
frozen in liquid nitrogen (avoids water crystals)
...
Using oestrogen: used to prevent egg release as keeping the oestrogen levels high inhibits FSH
production (& egg maturation) so egg can’t be released
...
Using progesterone: inhibit egg maturation & release by inhibiting release of FSH & LH
...
Using progesterone: stimulates production of thick cervical mucus to prevent sperm getting
through entrance of uterus (cervix)
...
Men can use a condom – which is
worn over the penis during intercourse to prevent sperm entering vagina (only form that protects
against STD)
...

 Hormonal methods are more effective & don’t need insertion every time, but they come with
unpleasant side effects (e
...
headaches, acne, & mood swings)
...


➢ HOMEOSTASIS:
 Homeostasis is the regulation of the conditions inside your body (& cells) to maintain a constant
internal environment in response to stimuli in both internal & external conditions; this is necessary
for the right conditions in order to function properly (e
...
enzyme action)
...
Blood glucose regulation: making sure the amount of glucose in your blood doesn’t get too high
or too low
...
Thermoregulation (body temperature): ability to reduce body temperature when too hot &
increase it when you get too cold
...
Osmoregulation (water content): balance between water you gain (from drinks, food, &
respiration) & the water you lose (by urination, sweat & breathing out)
...

 Glucose is a type of sugar
...
These levels are monitored by the pancreas – which produces hormones to control to it
by negative feedback
...

 HOW BLOOD GLUCOSE LEVELS ARE REGULATED BY NEGATIVE FEEDBACK:
1
...
The
glucagon causes the liver & muscles to convert glycogen stores back to glucose – which enter
the blood, so the blood glucose levels rise
...
When the levels are too high, the pancreas produces insulin & it is secreted into the blood
...

 Type 1 diabetes is a hereditary condition where the pancreas little or no insulin – this means the
person’s blood glucose levels can rise to a level that is fatal
...
g
...

 Although there are many ways to control type 1 diabetes, taking a pill is not one of them
...


 HOW TO CONTROL TYPE 1 DIABETES:
1
...

2
...

3
...
This makes sure glucose is removed quickly once the food has been digested
(so it never gets too high)
...
The amount of insulin injected is dependent on
their diet & how active they are as they affect their blood glucose levels (too much injected insulin
could lead to dangerously low insulin levels)
...
Obesity is a major risk factor for type 2 diabetes
...

 The correlation between type 2 diabetes & obesity (increased risk); obesity is when you have a BMI
over 30
...
The amount of fat stored can be indicated by the waist-to-hip ratio (above 1 for men or
0
...

 The changes in blood glucose level over time can be shown in a graph
...

 Core body temperature must be maintained at around 37oC as it is the optimum temperature for
enzyme activity (below would be too slow & above causes them to denature)
...

 This can’t be done by cold-blooded creatures, only homeotherms
...

 The skin is a sense organ containing effectors – which are muscles or glands that contract or secrete
hormones in response to stimuli
...

 HOW THE BODY RESPONDS TO DECREASED BODY TEMPERATURE (too low):
1
...

2
...

3
...

4
...

 HOW THE BODY RESPONDS TO INCREASED BODY TEMPERATURE (too high):
1
...




















2
...

3
...

Osmoregulation allows the water content of the blood to be controlled so the cells can function
normally
...
If water content is too low, water moves out by osmosis &
into blood – this causes the cell to shrink
...

Kidneys are part of the urinary system & they help to regulate water content by controlling the
amount of water reabsorbed or lost in urine – which is made from taking waste & unwanted
products out of the bloodstream (e
...
urea, excess ions & water)
...

HOW THE URINARY SYSTEM IS MADE UP:
1
...

2
...

3
...

4
...

5
...

6
...

7
...

The kidney has many different parts, including: the cortex (dark red outside with loads of
capillaries), the medulla (segments containing the loop of Henle), & the pelvis (central chamber
where urine arrives from collecting duct)
...
Useful substances are then absorbed back into the blood
(e
...
glucose, some ions, & some water) – this is known as selective reabsorption
...

HOW THE NEPHRONS PRODUCE URINE:
1
...
The liquid part of the blood (containing water, urea, ions, & glucose) is force out of the
glomerulus & into the Bowman’s capsule at high pressure - this process is known as
ultrafiltration (bigger molecules, like proteins, can’t pass through membranes due to thin walls &
tiny pores)
...
Filtered liquid leaves Bowman’s capsule & passes through proximal convoluted tubule, loop of
Henle & the distal convoluted tubule; as it flows, the useful substances are selectively reabsorbed
by active transport – this is known selective reabsorption
...
Whatever is left continues through the nephron via the collecting duct; then it passes into the
ureter down into the bladder; & released through the urethra as urine
...
Animals that live in drought conditions, have longer loops of Henle, so
more water can be reabsorbed
...

Anti-diuretic hormone (ADH) controls blood water content by controlling the permeability of the
collecting duct (more ADH, more permeable, more water reabsorbed) – this prevents dehydration
...


 HOW BLOOD WATER CONTENT IS REGULATED BY NEGATIVE FEEDBACK:
1
...

2
...

3
...

 HOW BLOOD WATER CONTENT IS REGULATED BY NEGATIVE FEEDBACK:
1
...

2
...

3
...

 Kidney failure causes waste substances to build up in your blood & you lose the ability to control
the level of ions & water in your body; this can cause problems with your heart, bones, nervous
system, stomach, mouth & more
...
For treatment, either they get dialysis
treatment (machines act as kidney) or kidney transplant (only cure)
...
In the machine, the blood flows alongside a partially permeable
membrane, surrounded by dialysis fluid
...
The dialysis
fluid has the same concentration of useful dissolved ions & glucose, so they won’t be taken
...

 The main problem with kidney transplant is the chance of rejection by the recipient’s immune
system; this happens when the antigens on the donor kidney are seen as foreign
...

 HOW TO PREVENT REJECTION OF A KIDNEY:
1
...

2
...


TOPIC 8: Exchange & Transport in
Animals
 All organisms must take in substances for life processes & remove the waste products produced
from them
...
Oxygen for aerobic respiration; carbon dioxide as the waste product (exchanged by diffusion) –
this is known as gas exchange
...
Water is taken up by osmosis; dissolved food molecules diffuse with it (or by active transport)
...
Urea diffuses from cells to plasma for removal from body by kidney
...

 CALCULATING SURFACE AREA & VOLUME:
surface area = length x width
volume = length x width x height
 In unicellular organisms, the gases & dissolved substances can diffuse directly in/ out across the cell
membrane, since they have a large surface area: volume; this means enough substances can be
exchanged across the membrane to supply the volume of the cells
...

 HOW FACTORS AFFECT RATE OF DIFFUSION:
1
...

2
...

3
...
g
...

 The relationship of proportionality between diffusion & its factor are shown in Fick’s Law
...

 The alveoli are surrounded by a network of tiny blood vessels called capillaries
...

 The concentration of oxygen inhaled from the air is higher than in the blood, so the oxygen diffuses
from the alveoli into the bloodstream; however, the carbon dioxide diffuses the opposite direction
(blood to alveoli) as the concentration is higher in the blood – then it is exhaled
...
Enormous surface area (75m2 in humans)
...
Moist lining to dissolve gases become they diffuse through alveolar walls
...
Very thin walls (one cell-thick for short diffusion distance)
...
Good blood supply to maintain concentration gradients
...
It includes the blood, blood vessels & heart
...

HOW BLOOD IS MADE UP:
1
...

2
...

3
...

4
...

Erythrocytes have a biconcave disc shape for increase surface area for absorbing oxygen (for
respiration) & have no nucleus to increase space; they also contain the red pigment haemoglobin –
which contains irons
...

Arteries are blood vessels that carry oxygenated blood away from the heart, towards organs
...
The walls are thick compared to the lumen
...
They
are microscopic as they have one cell thick walls to decrease diffusion distance; these walls are
permeable to allow diffusion
...
The speed & pressure of the blood
is low to allow for material exchange
...
The blood is at a
much lower pressure, so the walls don’t need to be thick (like arterial walls); they have a large lumen
to help blood flow, despite the low pressure – & the contraction of muscles
...

HOW DIFFERENT TYPES OF CIRCULATORY SYSTEM:
1
...
g
...

2
...
g
...
Second, the heart
pumps the oxygenated blood around the body, then deoxygenated blood returns to heart
...

Hearts in single circulatory system only have two chambers (ventricle & atrium)
...
The major blood vessels leading to & from the chambers are the aorta, vena cava &
pulmonary vein & artery
...
Like the vein, the heart has valves to prevent backflow
...


 HOW DEOXYGENATED BLOOD FLOWS THROUGH (THE RIGHT-SIDE OF THE)
HEART (from body to lungs):
1
...

2
...

3
...

4
...

 HOW OXYGENATED BLOOD FLOWS THROUGH (THE LEFT-SIDE OF) THE HEART
(from lungs to body):
1
...

2
...

3
...

4
...

 The blood flows in through vein into the atria – which contracts to push it into the ventricles; the
ventricles then contract – which pushes the blood out the heart through the arteries (this is known
as a double pump)
...

 Cardiac output is the total volume of blood pumped by the ventricles every minute
...

 CALCULATING CARDIAC OUTPUT:
cardiac output (cm3/min) = heart rate (bpm) x stroke volume (cm3)
 Cellular respiration is an exothermic reaction – which releases energy for metabolic process &
occurs continuously in every cell of every living organism
...

 HOW ENERGY FROM RESPIRATION IS USED:
1
...

2
...

3
...
g
...

 Aerobic respiration is respiration using oxygen; it is the most efficient way to transfer energy from
glucose
...

glucose + oxygen –> carbon dioxide + water
C6H12O6 + 6O2 –> 6CO2 + 6H2O
 Anaerobic respiration doesn’t use oxygen
...

glucose –> lactic acid
C6H12O6 –> 2C3H6O3
 The glucose is incompletely broken down, so it produces lactic acid; this is also less efficient as it
doesn’t transfer as much energy – which is why it is only used in emergencies
...

 Anaerobic respiration can also occur in plants (& fungi), but they produce ethanol & carbon
dioxide, not lactic acid
...
g
...

By measuring the amount of oxygen consumed by organisms in a given time, you can calculate their
rate of respiration
...

Respirometers can have two test tubes (one with living organism & one control tube of glass beads)
suspended in a water bath
...
One test tube has a syringe to set the manometer in
its bung, while the other has a closed tap
...
Take two test tubes with soda lime granules & cotton wool
2
...

3
...

4
...

5
...

6
...

7
...

8
...

9
...

10
...

CALCULATING RATE OF RESPIRATION:
rate of respiration (cm3/ min) = volume of oxygen taken up/ time taken
CALCULATING OXYGEN TAKEN UP:
oxygen taken up = distance moved by manometer x 𝛑r2
The soda lime/potassium hydroxide (KOH) absorbs the carbon dioxide produced from respiration
...

There are ethical issues in using live organisms, including: chance of woodlice running out of
oxygen & dying, temperature getting too hot, or woodlice touching corrosive soda lime (use gauze)
...
Habitat: where an organism lives
...
Population: all the organisms of one species living in a habitat
...
Community: all the organisms of different species living in a habitat
...
Ecosystem: a community of organisms along with the abiotic factors of their environment
...
Abiotic factors: non-living factors of the environment
...
Biotic factors: living factors of the environment
...
The first & smallest level is an individual
organism; together they make up the population; several of these make a community; & the final &
biggest level is the ecosystem
...

Changes in a population of one species can have a knock-on effect for other species in a
community; this is can be shown by the removal of a species in a food web
...
g
...
g
...

 Mutualism & parasitism are example of interdependence
...
Plants require
light, space & nutrients, while animals need space, nutrients & mates
...
Temperature
...
Light intensity
...
Amount of water
...
Levels of pollutants
...
Competition: organisms compete with each other for the same resources
...
Predation: animals that hunt & kill are predators; animals that are eaten are prey
...
Disease
...
You can measure it use random sampling with
quadrat by comparing two or more areas or by systematic/ continuous sampling using a (belt)
transect of quadrats to show by the distribution changes
...

 HOW TO INVESTIGATE USING QUADRATS (randomly):
1
...

2
...

3
...

4
...

5
...

6
...


 CALCULATING AN ESTIMATED POPULATION SIZE:
estimated population size = mean number of organisms per quadrat x total area of habitat
 Transects are can be used to find how organisms are distributed along an environmental gradient –
which is when abiotic factors gradually change across a habitat; belt transects are when quadrats are
specifically laid out along a line
...
Mark out belt transect with tape measure
...
Collect data along line using quadrats by counting organisms or estimating percentage cover (if
quadrat is divided into smaller squares)
...
You could also record abiotic factors in each quadrat (e
...
light intensity)
...
Repeat the steps above; work out average for the number of organisms & the abiotic factors
...

 Food chains show what’s being eaten by what in an ecosystem
...
Next is the primary,
secondary & tertiary consumers; each of these stages are called trophic levels
...
When the primary consumer eats the
producer, it uses some energy, gains nutrients, & stores the rest as biomass – this is process is
continued
...

 HOW ENERGY IS LOST FROM FOOD CHAINS:
1
...

2
...

3
...

4
...

5
...

6
...
g
...

 Since so much energy is lost, food chains can only have a limited number of trophic levels
...
Each time you go up a tropic level, the mass of organisms decreases; this
is because most of the energy is lost, so it can’t be stored as biomass in the next level
...

 CALCULATING EFFICIENCY OF ENERGY TRANSFER BETWEEN TROPHIC LEVELS:
efficiency = (energy transferred to next level/ energy available at previous level) x 100
 Biodiversity is the variety of living organisms in an ecosystem (more biodiverse is better)
...

 HOW HUMANS INCREASE/ MAINTAIN BIODIVERSITY:
1
...

2
...

3
...


 Maintaining biodiversity has many benefits, including: protecting human food supply, ensuring
minimal damage to food chains, providing future medicines, cultural aspects, ecotourism, &
providing new jobs
...

 HOW EUTROPHICATION WORKS:
1
...

2
...

3
...

4
...

5
...
g
...

 Fish farming is done is large nets or tanks in the sea
...

 HOW FISH FARMING REDUCES BIODIVERSITY:
1
...

2
...

3
...

 Using tanks is better as only one species is trapped, predators are kept away, & microbes are killed
...
They can be introduced
intentionally (e
...
food, hunting, or biological pest control) or accidentally (e
...
on international
cargo)
...

 The human population is increasing rapidly; this means the global food production needs to
increase as well, so everyone has access to enough safe food with the right balance of nutrition –
this is known as food security
...

 HOW BIOLOGICAL FACTORS AFFECT FOOD SECURITY:
1
...
As they is
less energy & biomass as you more up the food chain, in a given area of land, growing crops is
more efficient than grazing animals; the livestock would also eat food otherwise given to human
...
Environmental changes caused by human activity: burning fossil fuels releases a lot of carbon
dioxide (a greenhouse gas); increasing levels of greenhouse gases cause increased greenhouse
effect – this leads to global warming (a type of climate change)
...

3
...

4
...


➢ MATERIAL CYCLES
 Materials are constantly recycled through the biotic and abiotic components of an ecosystem
...
g
...
Elements are passed along the food chains
...

 The carbon cycle is very important because all living things contain carbon; however, there is only a
fixed amount of carbon in the world
...

 HOW THE CARBON CYCLE WORKS:
1
...

2
...

3
...

 The carbon obtained from photosynthesis is converted to glucose and can be turned in the complex
compounds that makes up the bodies of the green plants and algae
...

 HOW THE WATER CYCLE WORKS:
1
...

2
...

3
...

4
...

5
...

6
...

7
...

 Water that is suitable for drinking is called potable water; it must be clean and not too salty
...

 HOW TO DESALINATE WATER:
1
...
The
steam then travels through a pipe and is condensed back to pure water
...
Reverse osmosis (movement of water molecules from a high concentration of water to a low
concentration of water through a partially permeable membrane): saltwater is fed in vessel with a
partially permeable membrane at high pressure; the pressure causes the water molecules to move
in the opposite direction of osmosis (from low concentration to high concentration of water)
...

 Before entering the vessel, the saltwater is treated to remove solids
...
It is needed to make proteins for growth
...

 HOW THE NITROGEN CYCLE WORKS:
1
...

2
...

3
...

The nitrogen-fixing bacteria and plants have a mutualistic relationship since the plants get nitrogen
to produce protein and the bacteria get food in the form of sugars
...

Crops take up nitrates from the soil; however, as crops are harvested, they don’t decompose and
return the nitrogen to the soil by nitrifying bacteria
...

Farmers have developed ways of increasing the soil nitrate content, including: crop rotation (where
different crops are grown each year with nitrogen-fixing crop/ leguminous plants to replenish the
nitrates), and fertiliser (organic fertilisers like manure or compost to recycle nutrients through
decomposition of plant/ animal waste (but it smells bad); also, artificial/ inorganic fertiliser which
contains nitrates and other useful minerals (but it is expensive and leads to eutrophication)
...

HOW TO ASSESS USING INDICATOR SPECIES:
1
...

2
...

3
...

There are a few methods of using indicator species, including: survey of whether they are present or
absent, or counting how much are present to compare the numerical value to another area
...
g
...
It is best to use non-living indicators,
like a dissolved oxygen meter or electronic meter
...

HOW FACTORS AFFECT THE RATE OF DECOMPOSITION:
1
...

2
...

3
...

To calculate the rate of decay, you can work out, percentage loss or change in mass in a given time;
the graph created has a curve with an increasing gradient
...
It is best if the
food waste is finely shred to increase the surface area (more area to act on)
...

To preserve food, we use methods that slow decomposition, including: storing foods in the fridge
or freezer (colder), drying food (less water), vacuum packing (removes air – including oxygen) or
storing in an airtight container and sterilising (kills and prevents microorganism entering)

---