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Title: ib Biology SL Unit 6 notes
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 6 from the new syllabus (first examination in 2016)
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 6 from the new syllabus (first examination in 2016)
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6
...
S1
Production of an
annotated diagram of the
digestive system
...
1 The contraction of
...
Peristalsis
the involuntary constriction and relaxation of the circular and
longitudinal muscles of the intestine, creating wavelike movements
which push the contents of the canal forward and churn it
...
Consists of
relatively short
cellWhen food returns
to mouth while
vomitingabdominal
muscles work not C
and L
In the small intestine
peristalsis also mixes
food with enzymes
Therefore in the
intestines the food is
moved very slowly to
allow time for
digestion
...
1 The pancreas secretes
...
Small part secrete
insulin
and glucagon
the rest digestive enzymes
...
[Students should know
that amylase, lipase and
an endopeptidase are
secreted by the
pancreas
...
]
The enzymes are synthesized on ribosomes in gland cells in rER →
processed in Golgi apparatus → exit by exocytosis
Pancreatic juice containing the enzymes (amylase, lipase, protease,
endopeptidase) is released into the upper region of the small intestine
(duodenum) via the pancreatic duct
6
...
U3 macromolecules in food
into monomers in the
small intestine
...
]
Larger molecules
are usually insoluble, too large for diffusion across
membranes into the blood
Products of digestion
are usually soluble, small enough for absorption
into the blood and later assimilation into the tissues
6
...
U4 area of epithelium over
which absorption is
carried out
...
+enzymes break down the
above
Review 2
...
e
...
g
...
g
...
27
...
They have microvilli to
increase SA
6
...
U5 formed by digestion as
well as mineral ions and
vitamins
...
1 Different methods of
...
gdjdt
6
...
A1
Processes occurring in
the small intestine that
result in the digestion of
starch and transport of
the products of digestion
to the liver
...
1
...
Starch consists of amylose (by 1,4 bonds) and amylopectin (by 1,4 bonds
and occasional by 1,6 bonds)
Amylase breaks 1,4 bonds in chains of four or more monomers producing
maltose
Maltase digests maltose into glucose monomers
Dextrinase breaks the 1,6 bonds that amylase cannot deal with forming
glucose monomers, which is then absorbed and transported
1
...
2
...
3
...
4
...
5
...
Dialysis (visking) tubing
used to model absorption
Initially contains a mixture of starch and glucose
The tubing is semipermeable and contains pores
typically ranging 1 – 10 nm in diameter
● Tie 1 end with a knot
● Add glucose and starch (artificial gut)
● Rinse and the dry the bag (dialysis tubing) to get
rid off traces of starch and glucose
●
●
●
●
●
●
●
●
Find the mass of the bag using an electronic balance
Place tube in pure water in test tube
Test water around tube at suitable time intervals (e
...
1,2,4,8,16
mins)
Start a stopclock
...
Put one drop on the dimple tile, and the rest in a
test tube
...
Test the drops of liquid in the dimple tile by adding one drop of
iodine solution from the dropper bottle
...
Test the liquids in the test tubes by adding an equal volume of
Benedict’s reagent and then place the test tubes in a beaker of
boiling water for 2 to 3 minutes
...
After 15 minutes, sample the liquids inside and outside the tubing
again
...
6
...
S2
Identification of tissue
layers in transverse
sections of the small
intestine viewed with a
microscope or in a
micrograph
...
]
The small intestine contains four distinct tissue layers from the lumen
Mucosa
– inner lining, includes villi
Submucosa
– connective tissue (between the mucosa and muscle)
Muscular layer
– inner circular and outer longitudinal muscle perform
peristalsis
Serosa
– protective outer layer
6
General intro
6
...
U1 high pressure from the
ventricles to the tissues
of the body
...
2 Arteries have muscle
...
6
...
U3 fibres assist in
maintaining blood
pressure between pump
cycles
...
)
white blood cells ( phagocytes
eat up pathogens and dead cells,
lymphocytes
(B cells, Tcells) for the
immune response),
platelets
(clotting of blood flowing damage to cells or
erythrocytes)
Arteries
carry high pressure blood away from the heart to tissues that
need it
Kidney is supplied by renal artery, liver by hepatic artery
Structure:
Relatively (to the wall) small lumen maintains high blood pressure
...
This causes an
increase blood pressure
Elastic fibres stretch to increase the lumen with each pulse of blood
...
After the pulse of blood passes the fibres
recoil decreasing the lumen size to maintain a high blood pressure
...
increases blood pressure in arteries
Vasodilation
opposite process
6
...
U4 tissues in capillaries
...
Capillaries
are very small (< 10 μm diameter) and therefore can
penetrate virtually every tissue in the body
...
● Capillaries also allow substances to enter and leave the
organism, e
...
gas exchange of oxygen and carbon dioxide in the
lungs
...
● The walls and membrane can contain pores to further aid the
diffusion of substances
● The permeability differs per tissue
● Blood
travels slowly
under low
pressure allowing
more opportunity
for exchange
...
2
...
2
...
Valves in veins and the
heart ensure circulation
of blood by preventing
backflow
...
● The large lumen (compared to arteries and the thickness of the
wall) means that the blood is under low pressure
...
They also contain less
muscle than the arteries
...
● When blood flows towards the heart, it pushes the flaps to the
sides of the vein
...
6
...
A1
William Harvey’s (English
physician, in 1628)
discovery of the
circulation of the blood
with the heart acting as
the pump
...
He made this experiment:
Push your two fingers onto the vein at the hand end
...
This should squash the blood out of the vein
...
This experiment showed that this could not be the case, it showed that
blood is flowing from your hand towards your body, the opposite direction
to what Galen thought → blood moves from your heart out to your body
along arteries and then returns along the veins
...
2 There is a separate
...
double circulation – blood passes through the hard twice on one circuit of
the body
2 circulations:
the pulmonary circulation, the systematic circulation
6
...
S2
Recognition of the
chambers and valves of
the heart and the blood
vessels connected to it in
dissected hearts or in
diagrams of heart
structure
...
2
...
2
...
2
...
The sinoatrial node acts
as a pacemaker
...
Action potentials originates in the SAN and travels across the wall of the
atrium from the SAN to the AVN
...
The AV bundle divides into right and left bundle
branches an action potential to send rapidly only to the apex of each
ventricle along the bundle branches
...
The
rapid conduction from the AV bundle to the ends of the Purkinje fibers
allows the ventricular muscle cells to contract in unison providing a strong
contraction
...
2
...
2
...
Epinephrine increases
the heart rate to prepare
for vigorous physical
activity
...
2
...
Sl valves semilunar valves
6
...
A3
6
...
A1
Causes and
consequences of
occlusion of the coronary
arteries
...
6
...
S1
Identification of blood
vessels as arteries,
capillaries or veins from
the structure of their
walls
...
3 general
Pathogen
disease causing organism, e
...
bacteria (Can cause: food
poisoning, Ear and eye infections, Cholera, diarrhea, e
...
E
...
3 The skin and mucous
...
[Diagrams of skin are not
required
...
3
...
3
...
3
...
Clotting factors are
released from platelets
...
●
Wounds such as cuts to the skin causes opening through which
pathogens can potentially enter the body
● Platelets (small cell fragments) along with damaged tissue
release clotting factors in response to a wound
...
● The fibrin fibres capture red blood cells and platelets forming a
clot
...
Clotting example of a metabolic pathway (series of steps found in
biochemical reactions that help convert molecules or substrates, such as
sugar, into different, more readily usable materials
...
3
...
6
...
U5 by phagocytic white
blood cells gives
nonspecific immunity to
diseases
...
2
...
The fluid nature of the plasma membrane
allows this to happen
...
This is a vesicle that contains the pathogen
...
The digestive enzymes break down the pathogen and the waste products
are expelled from the cell by exocytosis
...
If the response is not enough and
infection becomes widespread then lymphocytes, which control the
specific immune response, are called into action
Pus white liquid when many white blood cells come to an area
6
...
U6 by lymphocytes in
response to particular
pathogens gives specific
immunity
...
]
6
...
U7
6
...
U8
Antibiotics
drugs used in the treatment and prevention of prokaryotic
bacteria
Antibiotics are designed to disrupt structures or metabolic pathways in
bacteria and fungi:
•cell walls and membranes
•Protein synthesis (translation)
•DNA/RNA synthesis
•Other metabolic processes (e
...
enzyme function)
These do not exist, or are very different, in viruses so antibiotics have no
effect upon them
...
Viruses lack a
metabolism and cannot
therefore be treated with
antibiotics
...
●
●
Viruses use the (eukaryotic) host cell metabolism, which protects
them
Viruses have a very different structure to prokaryote, just a
protein capsid and genetic material no cell wall or membrane to
attack
Indiscriminate use of antibiotics is leading to antibiotic resistance in
bacteria
•An example of evolution by natural selection
•Bacteria mutate and resistance to an antibiotic naturally arises
•Bacteria divide rapidly therefore a resistant strain of bacteria can quickly
spread
•Over time strains of bacteria can become resistant to multiple antibiotics
Antibiotic resistance can be avoided if:
● Antibiotics are prescribed only in serious cases
● Patients complete antibiotic course completely
● Hospital staff maintaining high hygiene standards to prevents
infection
● Farmers not using antibiotics in animal feeds to stimulate growth
● Pharmaceutical companies developing new types of antibiotics
+revise 5
...
A2
6
...
A2
Florey and Chain’s
experiments (1945) to
test penicillin on bacterial
infections in mice
...
It killed bacteria on agar plates → tested it on mice (deliberately infected
by Streptococcus bacteria that cause death from pneumonia) → 4 without
antibiotic died, 4 with survived → tested on a man, helped him but he
died when supply of the drug finished → tested successfully on more
people
...
3
...
[The effects of HIV on
the immune system
should be limited to a
reduction in the number
of active lymphocytes
and a loss of the ability to
produce antibodies,
leading to the
development of AIDS
...
AIDS is a syndrome
caused by HIV
...
This is the last
stage of HIV where the body can no longer defend itself and may develop
various diseases and if left untreated, death
...
However, with the right treatment and
support, people can live long and healthy lives
...
4 Ventilation maintains
...
The ventilation system maintains a large
concentration gradient between the alveoli and
the blood
...
Breathing out keeps the CO
concentration
2
in the alveoli low, so it diffuses out of the blood
...
6
...
U4 in the trachea and
bronchi and then to the
alveoli in bronchioles
...
]
6
...
A3
External and internal
intercostal muscles, and
diaphragm and
abdominal muscles as
examples of antagonistic
muscle action
...
Bronchuses also have
cartilage on walls
...
4
...
6
...
U6 required for inspiration
and expiration because
muscles only do work
when they contract
...
4
...
4
...
Type II pneumocytes
secrete a solution
containing surfactant that
creates a moist surface
inside the alveoli to
prevent the sides of the
alveolus adhering to
each other by reducing
surface tension
...
4
...
The external and internal intercostal muscles
work together
antagonistically
...
Antagonist muscles oppose a specific
movement to help to control a motion
...
This is needed as relaxation is a passive process, relaxing of a muscle
group is aided by the contraction of the other
...
emphysema can also be caused by air pollution
...
●
Protease is released by leukocytes (white blood cells) and
inflamed lung tissue
...
This results in the
destruction of small airways and alveoli
...
● Consequently large air pockets have a much lower surface area
to volume ratio than the alveoli which causes insufficient
ventilation
...
Symptoms include:
•Difficulty breathing
•Cough
•Loss of appetite
•Weight loss
Emphysema is not curable, but there are treatments that can help you
manage the disease
6
...
A2
Causes and
consequences of lung
cancer
...
6 +
Lung cancer is cancer that starts in the windpipe (trachea), the main
airway (bronchus) or the lung tissue
...
It causes more than 8
out of 10 cases, including passive smoking
...
Like most cancers lung cancer, if untreated, will end with death
...
6
...
S1
Monitoring of ventilation
in humans at rest and
after mild and vigorous
exercise
...
Ventilation rate and tidal
volume should be
measured, but the terms
vital capacity and
residual volume are not
Independent variable: the intensity of exercise
Control: What type of exercise? For how long? How will you make sure
that individuals exercise similarly?E
...
Lying, sitting, running on treadmill
(with different speeds)
Dependent variable: ventilation parameter
...
]
6
...
U1 electrical impulses
...
]
Neurons
cells that carry rapid electrical impulses, about 85 billion
Nerve
a group of neurons bundled together
Axons stretch from spinal cord to muscle that will contract
6
...
U5 action potentials
propagated along the
axons of neurons
...
Propagation because of ion movements depolarizing 1 part of
membrane and triggering depolarization in the neighbouring part of
neuron
...
6
...
U3 and potassium ions
across their membranes
to generate a resting
potential
...
5 An action potential
...
NaK pumps transfer Na and K ions across the membrane
...
When 3 Na ions pumped out, 2 K ions pumped in → conc
...
Action potential
rapid change in membrane potential, consisting of 2
phases: depolarization (a change from negative to positive) and
repolarization (a change back from positive to negative)
1) The Na+/K+ pump maintains the electrochemical gradient of the
resting potential
...
2) Opening of voltagegated Na channels in the membrane
→depolarization: Na ions diffuse into the neuron down the
concentration gradient → reversed charge imbalance across
membrane → inside is positive relative to outside → membrane
potential raised to +30mV
...
gradient
→ inside of cell
relatively negative
again
...
This enforced rest (refractory period) ensures impulses
can only travel in a single direction
...
5 The myelination of nerve
...
Myelin sheaths
insulate axon to help the conduction of the AP
Myelin many layers of phospholipid bilayer
Schwann cells grow and grow around the nerve fibre by depositing
myelin each time each time phospholipid bilayer
Myelinated axons only
allow action potentials to occur at the unmyelinated nodes of Ranvier>
the the action potential to jump (actually just the very rapid conduction
inside the myelinated portion of the axon) from node to node (saltatory
conduction)> the impulse travels much more quickly (up to 200 m/s)
along myelinated axons compared to unmyelinated axons (2 m/s),
saltatory conduction from node to node also reduces degradation of the
impulse and hence allows the impulse to travel longer distances than
impulses in unmyelinated axons, the myelin sheath also reduces energy
expenditure over the axon as the quantity of Na and k ions that need to
be pumped to restore resting potential is less than that of a
unmyelintated axon
6
...
U6 impulses is the result of
local currents that cause
each successive part of
the axon to reach the
threshold potential
...
On the
depolarized part of the axon → Na ions diffuse along to the neighbouring
polarized region
...
gradient is in the opposite
direction so Na ions diffuse from the polarized part back to the part that
has just depolarized
...
5 Synapses are junctions
...
[Only chemical synapses
are required, not
electrical, and they can
simply be referred to as
synapses
...
There are junctions between each cell called synapses across which
impulses cannot travel
...
Muscles+glands effectors
6
...
U8
6
...
U9
When presynaptic
neurons are depolarized
they release a
neurotransmitter into the
synapse
...
8)
Ca ions get removed from presynaptic neuron by active transport
following synaptic transmission
An action potential is only initiated if the threshold potential is reached
(coz only at this potential Na voltagegated channels start opening)
...
6
...
A1
Secretion and
reabsorption of
acetylcholine by neurons
at synapses
...
5
...
Neonicotinoids are synthetic compounds similar to nicotine
...
Acetylcholinesterase doesn’t break down
neonicotinoids → binding is irreversible
...
g
...
5
...
Membrane potentials in neurons can be measured by placing electrodes
on each side of the membrane
...
Xaxis time , yaxis membrane potential
...
Action potential → narrow spike (depolarization rising phase, threshold
potential, repolarization falling phase)
6
...
Hormones are secreted directly into the blood
...
The action of the hormone changes the condition of the tissue
...
Most hormonal change results in negative feedback
6
...
U1 secreted by β and α cells
Glucoregulation negative feedback
of the pancreas
respectively to control
blood glucose
concentration
...
6
...
There are small regions of
endocrine tissue (islets of Langerhans) in pancreas that secrete
hormones directly into the bloodstream
...
This stimulates the
breakdown of
glycogen into glucose
in liver cells and is
release into the blood, increasing concentration
● Beta cells synthesize
insulin
and secrete when the blood
glucose concentration rises above the set point
...
Insulin is then broken down by the cells it acts upon
so it's secretion must be on going
...
Causes and treatment of
Type I and Type II
diabetes
...
→ damage tissues, especially their proteins, impairs
(vnasel) water reabsorption from urine while it is forming in the kidney →
increased urine volume, dehydration
...
Injections usually done
before eating to prevent a peek of blood glucose as food is digested and
absorbed
...
Type 2 (adult onset) diabetes treated by adjusting diet to reduce the
peaks and troughs of blood glucose
...
Small amounts of food frequently, avoiding sugary foods
including high fiber foods strenuous exercise and weight loss
...
6 Thyroxin is secreted by
...
Targets: most body cells
Structure: 4 atoms of iodine
Effects:
•increases etabolic rate
m
/ rate of protein synthesis
•increases heat production (e
...
increased respiration)
Cooling → increased thyroxin secretion → stimulates heat production →
body temperature rises
6
...
U3 cells in adipose tissue
and acts on the
hypothalamus of the
brain to inhibit appetite
...
of leptin in blood is controlled by amount of food intake and
number of adipose cells
Targets:
appetite control
centre of the hypothalamus (in brain)
Leptin binds to receptors in the membrane of these cells
...
Effects:
An increase in adipose tissue increases leptin secretions into the blood,
causing appetite inhibition and hence reduced food intake
...
6
...
1949 Scientists discovered the ob/ob or obese mouse
...
It was found that obese mice possess two recessive alleles and
consequently do not produce any
leptin
...
6
...
6
...
Causes of jet lag and use
of melatonin to alleviate
it
...
They set a daily rhythm
...
Melatonin
secretion increases in the evening, drops to a low level at dawn
...
High
melatonin levels promote sleepiness
...
Jet lag is caused by the pineal gland continuing to set a circadian rhythm
for the point of origin rather than the current time zone
...
Ganglion cell in retina of eye detects light of wavelength 460480nm,
passes impulses to cells in SCN,
6
...
U5 chromosome causes
embryonic gonads to
develop as testes and
secrete testosterone
...
X carries many genes in the nonhomologous region which are not
present on Y
...
In embryos the first appearance of the gonads (organs that produce
gametes, i
...
testes or ovary) is essentially the same in the two sexes
...
If present the SRY gene encodes for a protein known as testis
determining factor (TDF)
...
In the presence of TDF the gonads become testis
...
6
...
U6 prenatal development of
male genitalia and both
sperm production and
development of male
secondary sexual
characteristics during
puberty
...
The testes secrete
testosterone which causes the male genitalia to develop
...
6 Estrogen and
...
Absence of fetal testosterone (gene SRY) + presence of maternal
estrogen and progesterone, female reproductive organs develop (ovaries
develop from embryonic gonads) due to:
•estrg
...
(1st secreted by mother’s ovaries then placenta)
•No testosterone
At first estrogen and progesterone are secreted by the mother’s ovaries
and later by her placenta
...
6
...
6
...
U8 controlled by negative
and positive feedback
mechanisms involving
ovarian and pituitary
hormones
...
]
Menopause when women stop menstruating permanently
First half of menstrual cycle –
follicular phase
, a group of follicles is
developing in the ovary
...
The
lining of the uterus is repaired it starts to thicken
...
The other follicles
degenerate
...
Continuous development of the
endometrium prepare it for the implementation of an embryo
...
The thickening of the
endometrium in the uterus also breaks down and is shed during
menstruation
...
Estrogen, progesterone ovarian hormones, produced by the wall of the
follicle and corpus luteum, absorbed by many cells in female body, where
they influence gene expression and therefore development
...
FSH also
stimulates secretion
of estrogen
by the follicle wall
...
Stimulates the repair and thickening of endometrium
after
menstruation
and an increase in FSH receptors
that make the
follicles more receptive to FSH, boosting estrogen production
(positive feedback)
...
●
●
LH
rises to a sudden and sharp peak towards the end of the
follicular phase
...
LH also
promotes the development of the wall
of the follicle after ovulation into the corpus luteum
which
secretes estrogen (positive feedback) and progesterone
...
Progesterone
promotes the thickening and
maintenance of the endometrium
...
Above progesterone, FSH, LH mass per millilitre measured in nanograms
(ng)
Estrogen measured in picograms (pg)
6
...
A4
The use in IVF of drugs
to suspend the normal
secretion of hormones,
followed by the use of
artificial doses of
hormones to induce
superovulation and
establish a pregnancy
...
Downregulation is the first step in IVF is the shutting down of the
menstrual cycle, by stopping secretion of the pituitary and
ovarian hormones
...
3
...
5
...
6
...
[William Harvey failed to
solve the mystery of
sexual reproduction
because effective
microscopes were not
available when he was
working, so fusion of
gametes and subsequent
embryo development
remained undiscovered
...
Downregulation is done
with a drug, commonly in the form of a nasal spray
...
High
doses of FSH are injected over approximately a ten day period to
stimulate the development of multiple follicles (the developing
egg and their surrounding cells)
...
Approximately 36 hours later, under a general
anesthetic, follicles (typically 8 – 12) are collected from the
ovaries
...
Successfully fertilised eggs are then
incubated before implantation
...
This treatment is
continued until pregnancy test, and if positive, until 12 weeks of
gestation
...
As a consequence the chances of IVF treatment leading to
multiple pregnancies are high
...
He
dissected female deer after mating to observe changes in the sexual
organs and found none
...
Harvey concluded that sexual reproduction doesn’t result from activities
during intercourse also false
Title: ib Biology SL Unit 6 notes
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 6 from the new syllabus (first examination in 2016)
Description: Detailed revision notes (covering everything you need to know for the syllabus) for SL IB Biology students for Unit 6 from the new syllabus (first examination in 2016)