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

---

Biology Notes
Life Processes
•

there are 8 life processes which are common to most living things:
o Movement (either with muscles or by slow growth)
o Reproduce (produce offspring)
o Sensitivity (sense and respond to stimuli)
o Control (manage their internal conditions)
o Nutrition (make or get food)
o Excretion (get rid of toxic waste products)
o Respiration (get energy from food)
o Growth (increase in size and mass using materials from food)

•

MRS C
...
g
...
This is
called oxygen debt
o releases a small amount of energy, happens in the absence of oxygen,
produces toxic products
o indicators:

o heat
o decrease in glucose
o increase in lactic acid/ ethanol
•

Uses of energy
o contraction of muscles
o active transport
o cell division
o building polymers
o keeping us warm

•

Experiments
o Evolution of heat from germinating seeds demonstrating respiration
o take two batches of peas
o boil one batch to kill them
o soak both batches in water for 24 hours to encourage the live seeds
to germinate
o wash peas in 1% bleach solution to kill any bacteria
o rinse twice in distilled water to remove bleach
o place the two batches of peas in separate thermos flasks
o place a thermometer in each and seal of around it with cotton wool
o wait for a couple of days and then measure results

o NB
...
03%) the indicator remains red
(either nothing is happening (as in the control) or respiration is being
balanced by photosynthesis)

▪

above normal carbon dioxide levels (>0
...
03%) the indicator turns
purple (less carbon dioxide forming carbonic acid and so more
carbon dioxide is being used up in photosynthesis

o Investigating carbon dioxide production by yeast in solutions of different
glucose concentration
o boil water in boiling tubes to remove oxygen and add glucose as
required to get a selection of different glucose concentrations
o add the same amount of yeast to each tube
o put a bung and delivery tube on each boiling tube and collect the
carbon dioxide produced over water
o measure the volume collected every minute for 20 minutes
(discarding the first 10 minutes of data as the yeast have to become
hydrated and active)
o use a 0% glucose solution as a control

Gas Exchange in Humans
•

Structure of the gas exchange system/respiratory system
o Thorax (the chest)
o Ribcage (protective arrangement of ribs around the lungs and aids in
ventilation)
o

Diaphragm (muscle that separates the thorax from the abdomen and aids in
ventilation)

o Intercostal muscles (join the ribs (or ‘costals’) together and aid in
ventilation)
o Bronchial tree (the highly branching network of air passages in the lungs)
o Nasal cavity (takes in air and warms it up)
o Epiglottis (flap of cartilage that covers up the larynx when eating to prevent
food entering the airways)
o Larynx (the voice box, produces sound allowing us to speak)
o Trachea (wind pipe, connects larynx to lungs)
o Bronchi (two tubes that the trachea splits into leading to each lung)
o Bronchioles (smaller tubes that the bronchi divide into)
o Alveoli (small air sacks at the end of bronchioles where gas exchange
occurs)
o Lung (an organ of excretion as they get rid of a product of respiration, N
...

the left lung is on the right as we look at it but on the owners left)
o Pleural membranes (two thin, moist membranes that form a continuous, airtight envelope around the lungs)
o Pleural cavity (space between the two membranes containing the pleural
fluid)
o Pleural fluid (lubricates the two pleural membranes)

!
o Cartilage rings in airways (keep the trachea and bronchi open during
inhalation, C-shaped in trachea to allow bulges of food to pass down the
oesophagus)
o Mucus (layer of sticky liquid that traps dust particles and bacteria)
o Goblet cell (a specialised cell that produces mucus)

o Ciliated cell (a specialised cell found in the major airways covered in tiny
hairs called cilia which beat backwards and forwards, pushing mucus up
towards the mouth where it can be swallowed and digested)

!
•

Ventilation
o Inhalation/Inspiration
o diaphragm contracts
o external intercostals contract raising ribs up and out
o internal intercostals relax
o thorax volume increase
o pressure decreases in the thorax
o air enters the lungs to equalise pressure with atmosphere
o Exhalation/expiration
o diaphragm relaxes

o internal intercostals contract pulling ribs down and in (only in deep
breathing)
o weight of the ribs and the natural elasticity of lungs force the lungs
to return to its natural shape (especially in shallow breathing)
o external intercostals relax
o chest cavity expand
o pressure decreases int the chest cavity
o air enters the lungs to equalise pressure
o thorax volume decreases
o pressure increases in the thorax
o air exits the lungs to equalise pressure with atmosphere
o Ventilation relies on the elasticity and airtightness of the lungs

!
•

Alveolus
o the site of gas exchange via diffusion
o oxygen passes from the air into the blood stream
o carbon dioxide passes from the blood stream into the air
o Alveoli are specialised for diffusion in the following ways:
o their shape ensures that there is large surface area covered in
capillaries where diffusion can take place
o thin walls allowing rapid diffusion
o moist surface allowing gases to dissolve increasing rate of diffusion

o excellent blood supply maintaining diffusion gradient
o gas exchange
o deoxygenated blood with a higher carbon dioxide concentration but
a lower oxygen concentration than the air flows past the alveolus
...
5cm
o drop the blocks into a beaker of dilute hydrochloric acid
o time how long it takes each block to go clear

•

Experiment investigating the effect of exercise on breathing in humans
o get your experimental subject to sit still for 5 minutes
o then count how many breaths they take in a minute
o wait a for a minute and then again count how many breaths they take in a
minute
o ensure you establish a steady resting rate, repeating until you get a
consistent number of breaths per minute
o then get your subject to run on a treadmill for 3 minutes
o after this exercise sit them down and count how many breaths they take
each minute until they have reached their resting rate

•

biological consequences of smoking
o bronchitis
o chemicals in the cigarette smoke destroy cilia in the bronchi
o mucus produced can't be move up to the mouth
o smoke irritates the bronchi lining causing them to produce even
more mucus causing the ‘smoker’s cough’
o this irritation along with infections caused by bacteria that aren’t
removed cause bronchitis
o it blocks normal air flow meaning sufferers have difficulty breathing

o emphysema
o smoke damages the alveoli walls causing them to break down and
then fuses together
o

this greatly reduces the surface area available for gas exchange
causing it to become less efficient

o thus less oxygen gets into the blood, less respiration can occur, less
energy is produce and so the person can do less exercise
o lung cancer
o chemicals that cause cancer (carcinogens) are contained in the tar
that collects in a smokers lungs
o these can cause cells to mutate and start to divide uncontrollably
forming a tumour
o tumours in lungs usually cause no pain so usually by the time they
are detected the cancer has spread or it may be inoperable and the
person dies
o carbon monoxide poisoning
o carbon monoxide is found in cigarette smoke
o it enters the blood stream through diffusion and binds strongly to the
haemoglobin in red blood cells forming carboxyhemoglobin and
preventing them from carrying oxygen
o thus less oxygen is carried in the blood stream
o this can means less oxygen gets to parts of the body that need it
causing heart disease, stunt foetus growth and diminish ability to
exercise
o nicotine
o highly addictive drug found in cigarettes that keeps people smoking
o causes excess adrenaline to be released, stimulating the heart to
beat faster
...
Example fish)
double circulatory system (blood is pumped from the heart to gas exchange
organ, then back to the heart and then the rest of the body
...
Example human)

the human circulatory system consists of:
o
o

blood vessels

o
•

the heart

blood

heart:
o

the pump that pumps your blood round your body
...
The wall of the left
ventricle is therefore thicker to produce more pressure

▪

the semilunar and atrioventricular valves (the Tricuspid and Bicuspid
valves) ensure that blood only flows one way

▪

the walls of the atria are thin and so can stretch to receive large
quantities of blood but contract with enough pressure to push the
blood into the ventricles

▪

the walls of the heart are made of cardiac muscle which can relax
and contract continuously without becoming fatigued

▪

▪

!
!
!

the heart is supplied by the coronary blood circulation with coronary
arteries supplying capillaries with blood for the heart which is then
enters coronary veins
...
B
...
g angry or afraid)
...
Adrenaline also triggers the following
things which help in ‘fight or flight’ situations:
•

breathing rate increases and breaths become deeper meaning
more oxygen is taken into the body

•

blood is diverted away from the intestine to the muscles

•

in the liver glycogen is converted into glucose and released
into the blood stream for muscles to absorb

•

pupils dilate increasing visual sensitivity to movement

•

mental awareness is heightened making reactions faster

•

hair stands on end (making some animals look bigger)

▪

in sleep our organs are less active and so need less blood, meaning
heart rate decreases

▪

heart rate is adjusted through the following negative feed back
system:
•

as we begin to exercise our muscles produce more carbon
dioxide in aerobic respiration

•

•

these send nerve signals to the medulla (part of the brain)

•

the medulla responds by sending impulses along the
accelerator nerve which causes the heart to beat faster and
stronger

•

when carbon dioxide levels return to normal fewer impulses
are sent to a precise region of the medulla called the Cardiac
Centre

•

the medulla responds by sending impulses along the
decelerator nerve which causes the heart to beat slower and
less strongly

•
•

this enters the blood stream and the excess amount of carbon
dioxide present is detected by sensors in the aorta and the
carotid artery

these controls are both example of reflex actions

Blood vessels
o

Arteries
▪
▪

generally carry oxygenated blood apart from the pulmonary artery
and the umbilical artery of a baby

▪

must be able to allow their walls to stretch under the high pressures
but the to recoil and push the blood forward

▪

o

carry blood away from the heart under high pressure (arterial blood)

this means they have a thick wall containing elastic fibres and
muscles so they can return to their normal shape
...
They also have a
large lumen and an endothelium lining

Capillaries
▪

carry blood through organs bringing it close to every cell

▪

various chemicals must be able to diffuse between individual cells
and the capillary

▪

this means their walls are one cell thick so they can fit in between
cells and allow chemicals to diffuse

•

Diagram of the Human circulatory system

•

blood:
o red blood cells
o biconcave, disc-like cells with no nucleus which transport oxygen red
in colour that are in circulation for 100 days
o they are specialised for this function by:
▪

containing haemoglobin (a protein containing iron that, in high
concentrations of oxygen in the lungs, binds with oxygen forming
oxyhaemoglobin (loading oxygen) and, in low oxygen concentrations
in active tissues, oxyhaemoglobin breaks back down into
haemoglobin releasing the oxygen (unloading oxygen))

▪

not containing a nucleus (meaning more room for haemoglobin)

▪

having a high surface to volume ratio due to its biconcave structure
(meaning more area for diffusion and a faster rate of diffusion to all
parts of the cell)

▪

having thin surface membranes (giving the oxygen a short diffusion
distance)

o white blood cells
o phagocytes (70%) protect the body against pathogens (disease
causing microorganism can be bacteria (e
...
pneumonia), viruses
(e
...
AIDS), protoctists or viruses) through ingesting pathogenic
microorganism like bacteria by phagocytosis
...


▪

some of the new lymphocytes produce antibodies to combat the
infection (as previously explained) and then die

▪

others become memory cells which are not directly involved in the
killing of pathogens but instead:

▪

they stay in our bodies for many years

▪

next time we are infected by the same
pathogen the memory cells can recognise it
quickly

▪

there are more of them so new lymphocytes
can be produced more quickly and in greater
volume resulting anti bodies being produced
sooner, faster and in greater quantity and so
the infection dealt with more quickly than the
first time

▪

after the second infection more memory cells
remain meaning that are next response will be
even quicker

▪

these memory cells make us immune to
specific infections

o Vaccination
▪

a person can be artificially made immune through vaccination
•

an ‘agent’ carrying the same antigens as a specific diseasecarrying pathogen

•

lymphocytes recognise the antigens and multiply, producing
memory cells

•

these memory cells make the person immune

•

agents can be
o

a weakened strain of the actual microorganism

o

dead microorganisms

o

modified toxins of the bacteria

o

just the antigens

o

harmless bacteria genetically modified to carry the
antigens of a specific pathogen

o blood plasma
o consists of water which acts as a solvent for many substances and
holds the other structures that make up the blood in suspension
allowing the blood to flow
...
01-0
...
Nonessential
amino acids can be synthesised in the human body

o

!

There are 20 different kinds of amino acids each one is determined by the R
group made from nitrates and sulphates
...

▪

Eg
...
Plants store oil in seeds
...
Three fatty acids connected by
Glycerol
...


o

Lipids also make up cell membranes
...

Phosphates point outwards in cell membrane, and fatty acids point inwards
...
Glucose) – Benedict’s solution, when heated
with reducing sugar, will turn from green to brown to red
...


▪

NB: Doesn’t work with Sucrose, which has to be reduced first
...

This breaks the peptide bonds
...
Positive test =
the solution will turn from blue to purple
...


o

Test for Lipids 2 = Add Ethanol to an oil
...
Positive test =
Liquid turns white and opaque
...
Found in cells/alimentary
canal
...
Eg
...

Anabolic = Builds up
...
DNA Polymerase turns nucleotides to DNA
...


o

This active site provides surface for reaction

o

Enzyme + Substrate ⬄Enzyme-Substrate Complex ⬄Enzyme + Product

•

Denaturation = Loss of 3D Shape of an enzyme, and therefore loss of active site
shape

•

Effect of Temp
...

At this point it won’t work any more, because no more active site shape
...
)
Once they leave this range, they will stop working permanently, due to
denaturation
...

▪

Eg
...
Do a starch test on samples (taken with
pipettes ) every 30 seconds, and see how long until there is no
starch left
...


!
!
!
!
!
Photosynthesis
•

Process split into two stages
1
...
[Extra: Happens in Grana in Chlorophyll – stacks of
membranes
...
Dark stage: stage in which ATP is used to provide chemical energy to reduce
CO2 into a carbohydrate i
...
glucose
...

LIGHT
6CO2
6H2O ---------------> C6H12O6 + 6O2
+
Limiting factors for photosynthesis
o Light – Intensity and Wavelength – Greater intensity/non-green = faster
...
(Limit when plants are damaged)
o Carbon Dioxide concentration – More = faster
...

o Stomata allow for CO2 to enter into the leaf
...
Gas spaces in spongy mesophyll area
...

o Guard cells can open/close to allow more/less water to escape
...

CO2 not needed
...

o Contains chlorophyll
...
Remove leaf and place in near-boiling water
...
Leaf now permeable to iodine)
2
...

3
...
Chlorophyll dissolves out and leaf becomes pale
...
Replace leaf in water, because water will also dissolve out
...
Place leaf flat in petri-dish
...
Starch test
...
Necessity of CO2:
▪ Destarch
...
) Illuminate for 12 hours
...
If starch is present, photosynthesis is
happening
...
Necessity of Chlorophyll:
▪ Destarch variegated plant
...
Test
the leaf for starch
...
Short
time period to prevent movement of sugars
...
Necessity of light:
▪ Destarch
...
Illuminate for 12 hours
...
If starch is present, photosynthesis is happening
...
Light intensity compared to rate of photosynthesis:
▪ Place Kabomba (pond weed) in flask and measure production of
oxygen, as a lamp is moved towards or away from the plant
...
The
greater the light intensity, the greater the rate of photosynthesis
...


!
!
!
!

Plant Transport
•

Uses of substances within plants
...

Starch – Long term storage of carbohydrates – compact and insoluble
...

Protein – Growth, building of cellular structures, repair
Lipids – Production of cell membranes and long term energy store in seeds
and nuts
...
diffusion (the net movement of molecules down a concentration gradient)
2
...
active transport (moving molecules against a concentration gradient using
protein pumps and ATP)

•

Osmosis experiment:

!

!

1
...
Place one in pure water, one in
water with a high sugar concentration and one in a solution of similar
concentration tho that of the potato
2
...
The one in the water with a high sugar concentration will shrink and lose
mass due to water passing from the high water potential of the water with
a high sugar concentration to the comparatively low water potential of the
potato core via osmosis
4
...
transports sucrose and amino acids from the leaves (sources) to the rest of
the plant (sinks) especially growing areas/storage areas/fruits and seeds
2
...
works on a pressure flow system (and so can move substances up and down
the plant)
4
...
this causes water potential of the leaf sieve tube to decrease
6
...
this increases the turgor pressure which then forces the dissolved sucrose
and amino acids along the phloem to the sinks
8
...
this increases the water potential of the root sieve cells
10
...
this lowers the tutor pressure
12
...
Minerals pumped into roots via active transport decreasing water potential
inside the roots
2
...
Water moves via osmosis though the cortex into the Xylem
4
...
Water is lost from the top of the leaf through transpiration
6
...
This pulls up a chain of water molecules (transpirational stream) moving
water up the plant
8
...
The whole process of moving water can be referred to as the cohesiontension theory

!

•

Xylem = Microscopic tubes that transport water and dissolved minerals
...
Their cell walls are thick
and strengthened/waterproofed with lignin
o

Transpiration affected by:
1
...
Air Movement/Wind - Humidity shells are blown away = Higher
concentration gradient = Higher rate of transpiration
3
...
Light intensity – Higher light intensity = more stomata open = more
holes for water to escape through = Higher rate of transpirationa

o

Potometer measures the uptake of water by a leafy shoot; uptake roughly
equals rate of transpiration but some water is used in photosynthesis;
potometer can be used in various experiments to see how factors effect
transpiration

o

Experiment:

- Set up apparatus below, and blow wind on the leaf
...


- Measure how long it takes for the air bubble to move 1cm with and without wind
...

- Measure vol H20 taken up / minute / cm2 of leaf, with and without wind
...


o

When this experiment is being set up, the leafy shoot end must be always
kept in water – during breaking and attaching, so air bubbles don’t clog up
the xylem

• Another way of measuring transpiration
- Weigh a plant and place all the subterranean parts of the plant (which are in a
watered pot of soil) in a plastic bag so the water can’t evaporate so can measure the
weight of the plant again after a specific length of time to learn the water lost
through transpiration
...
If the cells go flaccid (having not enough water in the cells) then
the plant will wilt and may die

Crops and Plant Growth
•

Salts and minerals are important in the growth of plants
...
Mg2+ is absorbed by the roots in solution and is an important compound in
chlorophyll
2
...
You can therefore make proteins which are
needed for growth

•

Fertilisers are used to boost crop yields:
1
...
Brown manure is made of animal faeces
...
It is
used to restore minerals
3
...
The pods are
removed and the rest of the plant is ploughed into the sol this is because
they have root nodules which have N-fusing bacteria which can make
nitrogen in the air into nitrates
...
Farmers use a rotation of crops on a field
...
Artificial fertilisers are used for intense non-organic farming
...
g
...
g
...
Grow exotic varieties
2
...
Increased growing rate

•

You can control:
1
...

2
...
Pests can be controlled with fungicides (for funguses), insecticides (for
insects), herbicides (for plants), molluscicides (for slugs and snails) or
biological control in the enclosed environment ensuring efficient use
4
...
Pollinating insects can be released
6
...
g
...
Computer systems can monitor and control conditions
8
...
Systemic pesticides are very effective on plant
...

They reach all parts in particular the roots and kill the plant
•

Pesticides: used to kill organisms that would eat crops decreasing yield (without
pesticides cereal crop production would fall by 45% in 2 years)

•

Disadvantages of pesticides:
1
...
They are poisons and so can create human health problems
3
...
Application efficiency can be low due to wind drift and run-off
5
...
If the pesticide isn't biodegradable (doesn’t break down), bioaccumulation/
biomagnification can occur with each predator eating multiple individuals
who have consumed small amounts of pesticide increasing the amount of
pesticide in animals the higher up the food chain one gets even reaching
humans
...
g
...
Over use of a pesticide can result in super resistant pests
▪
▪

as more pesticide is applied the population becomes more and more
made up of resistant pests

▪

the pesticide no longer works as the entire population is now
resistant

▪

ban and develop non-specific/ non-biodegradable pesticides

▪

•

pesticide is applied most pests are killed but some survive (of which
most will have a resistance to the pesticide)

use biological control

Solutions:

Biological Control

Chemical Pesticides

Specifity

Very high as long as it is
managed properly

Can be low but new technology
is changing this

Accumulation

None

Can happen

Permanence

Good but some pests must be
tolerated in a predator pray
balance

Bad, requires regular
application

Development of resistance

Very rare

Common

Cost

Initially high but then very low

Generally high restricting use to
wealthy nations

Diet and Digestion
Diet:
•

Diet: The food that we eat

•

Balanced Diet: All the necessary foods in their right properties for a healthy life
...
Carbohydrates
2
...
Protein
4
...
Minerals
6
...
Water
8
...
Fitness
2
...
Age
4
...
Pregnancy
6
...
Allergies

Vitamins
Vitamin

Why

Deficiency

Storage

C-Ascorbic Acid

Helps prevent fluid
leaking and makes
fibres that ‘glue’
tissues together

Scurvy-tissue leakage, Water solublebleeding, hair loss,
Can’t be stored
internal bleeding
...
It
allows low light and
colour vision

Night Blindness

Fat soluble

B-Various

Almost all
concerned in
respiration or cell
metabolism

Beri-Beri, poor growth Water Soluble

!
!
Mineral

Why

Calcium-Ca

Needed for bones, cell metabolism and
respiration in large quantities

Phosphorous-PO

Needed in bones, teeth, DNA and ATP

Sodium-Na

Maintains osmotic balance and as electrical
impulse in nerve cells

Chlorine-Cl

Osmotic balance with sodium
...
2 kJ

•

A calorie is the energy needed to raise water by 1oC

•

Measuring energy content of food method:
1
...
Record starting temp
...
Record mass of food sample
4
...
Measure maximum temperature of water
6
...
Calculate energy using :
Energy produced = Vol
...
rise x 4
...
With this method a biscuit has 3500 kJ/g
9
...
Both of these are less than ¼ of actual energy thanks to heat loss
...


•

When food enters the mouth both physical and chemical digestion occurs
1
...
Chemical digestion occurs as saliva (water, mucus and enzymes) containing
salivary amylase breaks down starch to maltose
...
Swallowing is
controlled by circular and longitudinal muscles in the oesophagus
...


•

Peristalsis moves food into the stomach where it is trapped by a pair of sphincters
...
They contain water HCl
and enzymes (pH 1
...
It helps the digestions of
proteins as it unravels amino acid strings
...


•

Peristalsis helps physically digest as the wave of contractions churns the food
liquefying it
...


•

The food hitting the duodenum walls stimulates 2 things
...
Bile containing sodium hydrogen carbonate is alkaline and neutralises
stomach acid as well as emulsifying fats increasing their surface area
...
8 the optimum for most other enzymes
...

2
...
This contains most enzymes
...
Maltase breaks maltose into glucose
...
Lactase breaks lactose into galactose and glucose and proteases
break down proteins into peptides and amino acids
...


•

All enzymes hydrolyse their substrates
...
Anabolic
enzymes however build up substrates by releasing water
...


$

!
•

The food then passes through the large intestine

•

The large intestine comprises of the caecum, appendix, colon and rectum

•

The caecum is the start of the large intestine and in humans is small and
insignificant
...
Some small herbivores perform refection
...


•

The appendix too is small in humans and is a dead end
...


•

Appendicitis occurs when faeces get trapped in the appendix
...
This causes and excess of white blood cells in the appendix !
appendix swells! appendix bursts ! internal bleeding
...
It absorbs water
...


•

The anus controls the release of faeces with a sphincter
...


•

Praticcles move eacuse they have kinetic energy
...

In hiugh concentrations they collide more often scattering them more
...
Asexual

•

Sexual: includes fertilisation ! fusion of nuclear material

•

Asexual: no fertilisation

•

Off spring: an organism independent of its parent

•

Asexual:

1
...
It is cell mitosis
3
...
Example are: Potato tuber, strawberry runners
5
...
Advantages: Quick and easy
...
Disadvantages: small genetic pool ! slow evolution and can’t adapt
...

•

Sexual reproduction:
1
...
Meiosis
...


There is only a single parent cell
...


No fertilisation occurs in the process
...


The offspring is genetically identical to its
parents and is known as a clone
...


It involves mitosis which is the duplicating
of a cell
...


There is mixing of hereditary material
...


Gametes are involved
...


Sexual reproduction is time consuming
taking months for the zygote to grow into
and embryo then a live organism
...


Meiosis: The cell increases its chromatid
number by replicating its DNA
...

Hen by reduction division it splits into 2
cells with 46 chromatids then 4 with 23
chromosomes

Mitosis: Cells replicate their DNA which
fuses to form 46 chromosomes but 92
chromatids it splits by mitosis to form 2
daughter cells which are genetically
identical to the parent cell and have 46
chromosomes each
...
Chromatin condenses to form chromosomes
...
e
...


2
...
This is prophase
...


$
3
...
Meiosis creates gonads which need half the number of chromosomes
...

2
...

3
...
The lasts stage is similar to mitosis where the 2 cells split and the
chromatids separate creating 4 haploid cells with 23 chromosomes in each
...
During this crossing over occurs here non-sister chromatids cross over break
and rejoin ! infinite genetic variation
...


•

The zygote divides into a hollow ball of cells called a blastosyst which embed itself
in the endometrium using enzymes
...
Placenta for oxygen and food to enter and Carbon Dioxide and waste to
leave
...
The placenta secrets progesterone to keep the placenta attached
3
...


Sex
•

Primary sexual characteristics are determined by genes XY-Male and XX-female
...


Female

Male

Menstruation

Sperm production

Ovulation

Hair growth

Breast growth

Muscles grow

Genitalia growth

Voice deepens

Hair growth

Genitalia grow

Hips widen
Hormones
•

FSH is follicle stimulating hormone and is secreted by the pituitary gland
...


•

Men: Stimulates growth of testes, sperm production, stimulates secretion of
testosterone
...
Acts on ovaries causing them to mature
2
...
The growth of a follicle secretes oestrogen
4
...
The follicle become a corpus luteum secreting progesterone maintaining
endometrium
6
...
L
...


!
!
!
!
!
!
!
!
!

!
!
!
!
!
!
!

!

Plant Reproduction
•

Pollination: the movement of pollen from anther to stigma

•

Cross pollination: 2 plants

•

Self-Pollination: one plant

•

Plants have mechanisms to stop self-pollination as they want to cross-pollinate for
larger genetic variation i
...

1
...
Carpel and stamen are at different heights
3
...
Nutritious to
attract insects
...

Inflated grains so they are
light
...


•

After pollination fertilisation occurs
...
The tube digests its way down to the ovaries using enzymes
...
Once it reaches the
ovule it fertilises the ovule
...


•

Zygote!embryo plant
...


•

The testa is a coat protecting the seed
...
His is to slow metabolism so it uses up its food
stores very slowly (( can last for over a year)

•

The seeds are then transported far from the parent by wind, water, animal to
lower competition ! more survivors
...
Absorption of water hydrating enzymes and rehydrating cells so that life
processes begin
2
...
The root then emerges
4
...


•

Conditions needed:
1
...
Suitable temperature
3
...


•

Ecosystem-a generally self-supporting group of habitats and a community
...
e soil, climate etc
...
e disease, predation
...
Create their own food by the conversion of sunlight energy into organic
molecules through photosynthesis
...
Consumers are the animals in he feeding relationship
...
Primary consumers eat the producers
3
...


•

Saprotrophs:
1
...


•

A food chain is a simple illustration of a feeding relationship showing a single prey
of a predator
...
This produces a web which is more stable

•

Trophic Level: A stage in a feeding relationship such as a food web or chain it shows
whether the organism is a producer or a consumer

!
!
!
!
!
!
!
Pyramids

$
•

Numbers :
1
...
The limitation of them is that they assume all animals are equal
...
Pyramids of biomass are almost always pyramid shaped giving us much more
of a pattern
2
...
They
equate a kilogram of wood to a kilogram of flies
•

Energy:
1
...
They are the best kind ass
they show energy flow
...


•

Why is there are 90% loss?
1
...
Respiration/ heat loss is the biggest culprit
3
...


•

Sampling you must ensure the chosen sample is representative and to avoid bias
the sample has to be random
...


•

You also must take sufficient samples to get a significant result

Study:
1
...
Results
Trampled

Not trampled

Our ave:18
...
28

!
3
...
Evaporation
2
...
Transpiration
4
...
Photosynthesis
6
...
Condensation

•

Carbon Main Processes:
1
...
Respiration
3
...
Combustion
5
...
Fossil fuels

•

Nitrogen Cycle:
1
...
Nitrifying bacteria (aerobic): covert ammonia!nitrites!nitrates
3
...
Nitrogen fixing bacteria: convert nitrogen gas ! ammonia and are found in
root nodules of leguminous plants
...


•

Since farmers want many nitrifying bacteria in the soil they must plough the land
to make it aerobic

Fertilisers

•

Natural Fertilisers:
1
...
Brown manure is faecal matter sometimes mixed with straw
...
They need to be monitored carefully
...


•

All of this ends up in waterways which are enriched by extra minerals ! algal
bloom and eutrophication

•

The algal bloom covers the surface so any water plants can’t photosynthesise and
die

•

The algal bloom uses all the minerals and dies

•

Large plan materials decompose and the bacteria uses oxygen ! oxygen levels
drop and the water becomes anoxic -water becomes anaerobic and aerobic life dies

•

Lakes ponds and still water will be severely affected and any life may die out

•

Rivers can recover

•

Oceans aren’t exempt from being affected
...


•

NO2 dissolves to form acid rain
1
...
reeks hazard in habitats
3
...
The acidic rain changes the soil pH destroying local vegetation
...
In forests it removes Ca2+ and Mg2+ and destroys palisade layers

•

CO-Carbon monoxide is a colourless, odourless gas produced by cars and gas boilers
1
...
Once bound haemoglobin can’t release the CO so organisms end up oxygen
starved
•

Greenhouse Gases:
1
...
CO2
3
...
CH4
5
...


•

Aerosol propellants have CFCs which are 105 times worse than carbon dioxide as a
GHG
...


!
•

Deforestation

•

Deforestation is the removal or destruction of woodland faster than it can grow
back

•

Between 1880 and 1980 about 40% of all tropical rainforest was destroyed

•

Why?
1
...
Cattle Ranching
3
...
Wood products

•

Effects:
1
...

2
...

This can lead to islands of woodland resulting in local and eventually total
extinction
...
Soil erosion as there are no leaves to protect soil
...
Deciduous trees are cut down an removed taking away 90% of the nutrients
in a forest ! reduction in soil fertility
5
...
The atmosphere may become drier and the soil wetter as evaporation from
soil is slower than transpiration
7
...


!
•

Ozone

•

The Ozone layer was the key factor allowing life to develop as t protects us from
UV(-C 240-290nm) radiation which would have killed any life as it destroys DNA
...
Sun burn
2
...
Cataracts

•

CFCs used in refrigerator coolants, aerosols and expanded plastics cause Cl to
remove an oxygen atom from ozone depleting the ozone
...


!
!
•

River pollution:

•

Waste! rapid multiplication of aerobic bacteria!depletes oxygen levels!High
BOD

•

Indicator species:
1
...
e
...
Heavily Polluted: fish are absent
...
Slightly polluted: slower fish i
...
pike and species with moderate demand
for oxygen

•

Since there is a constant supply of fresh water in rivers the waste is usually
dispersed downstream allowing the river to recover
...
Intraspecific predation: group fish by age and size and feed them
adequately
2
...
Make sure
animals from the external environment aren’t predators or can’t get into
farms
3
...

4
...

5
...
Find the goldilocks zone
for feeding; too little! malnutrition; too much ! wastes
6
...


!
DNA and Cell Division
DNA
•

In the nucleus of the cell long rod-like structures called chromosomes are found
...
e
...


•

Structure of DNA:
1
...
The phosphate and bases are connected by a deoxyribose sugar
3
...
The DNA molecule is in the shape of a double helix completing a full spiral
every 10
...
A always bonds with T with 2 H-bonds and C to G with 3

$
•

There are two types of strands in the DNA molecule but one is the sense strand and
the other the anti-sense strand
...
e
...


•

The cells come to rest at the equator of the cell and then are pulled apart by
spindle fibres to the poles of the cell

•

The cell then divides into two identical cells which are diploid and are genetically
identical to the parent
...
e
...
e
...
e
...
e
...


•

Some genes have more than one form and these are cakes alleles
...


•

Dominant: the allele which determines the characteristic (phenotype) even in the
presence of an alternate allele

•

Recessive: the allele which doesn’t influence the characteristic of an organism
unless it is present with an identical allele

•

In a heterozygous organism the dominant allele will express its phentoype

•

Homozygous: an individual with 2 identical alleles at a given locus

•

Heterozygous: an individual where the 2 alleles at a given locus are different

•

Genotype: the genetic constitution of an organism with respect to the alleles in
consideration

•

Phenotype: the measurable characteristic or appearance of an organism resulting
from the interaction between an organism and its environment

•

Codominance: RW would result in some cells being Red and others expressing a
white phenotype
...
e
...

•

Monohybrid inheritance:

Gamete genotypes: Aa

x

Aa

Offspring genotypes: AA Aa Aa aa
Phenotypes: 3:1
•

For family pedigrees, apply this to genetic diseases
...
These are translated into phenotypes and
then phenotype ratios or probabilities
...

It may happen to only one gene or an entire chromosome

•

One way in which they can occur is during replication ! an alteration in the
sequence ! the wrong amino acid is produced
1
...
As a result the
entire sequence after this point is effected ! an entirely different protein
! greater chance of a mutation
2
...
Substitution: the wrong nucleotide is used
...
The protein molecule may be different (as
amino acids have multiple base codings)
...
Inversion: As bases are read in triplets it is possible that on the new strand
they may be reversed ! only one triplet is affected
...
Some can be neutral not
in fact changing the amino acid produced
...
e
...
e
...
New species continually
arise from species that exist and others become extinct

•

Natural Selection: the mechanism by which new species arise
...
! Forms become increasingly different
...


•

Variation within species is called intraspecific

•

Variation between different species is interspecific

•

Variation arises from the random assortment of chromosomes caused by meiosis

•

New genes and variations can only arise from mutations

•

Evidence for natural selection:
1
...
Changing conditions in the environment (selection pressure) which favours
one particular form of species (selective advantage)
3
...
Changes are not due to any other factor

•

Natural variation or mutations means that some organism within a species may
develop features which are beneficial i
...
a giraffe may develop an even longer
neck
...


•

In comparison more of the organisms without this feature will die out

•

Over many generations as more organisms with this feature are surviving the
percentage of this trait increases within the population

•

When penicillin, the first antibiotic, was discovered by Fleming in 1929 it was
extensively used
...


•

As bacteria divide once every 20 minutes the population of the resistant bacteria
will increase rapidly ! ineffective antibiotic

Feature of Natural Selection

Effect

Selection Pressure

Repeated use of antibiotic

Natural Variation

Some bacteria resistant due to chance
mutation and others aren’t

Type with selective advantage

Resistant type survive

Type selected for

Resistant type

Type selected against

Non-resistant

Result of natural selection over many
generations

Percentage of resistant type increases in
the population

•

Observation: Organisms vary intra-species

•

That variation is heritable

•

Conclusion: In the struggle for survival the organism with the most favourable
variation survive and reproduces so its offspring gain its variation

•

Observation: Organisms produce more offspring than they need to replicate
themselves

•

But population remains constant

•

Conclusion: Struggle for survival ! over generation population adapt to their
environment

Selective Breeding
•

Traditionally farmers cross-bred strains of wheat with desirable characteristics with
the hope of developing them i
...
increased yield; shorter, stronger stems:
1
...
Disease resistance
3
...
Hardier and grow-able in more seasons
5
...
e
...
Produce more meat, milk or eggs
2
...
Produce more offspring
4
...
Most parts if the plant can be
used as the cells are totipotent and therefore have the ability to become any
specialised cell
1
...
These are the explants
2
...
5-1mm
3
...
More explants can be taken from the new shoots and this can be repeated
until there are enough to supply the demand
5
...
When the explants have grown riots the are composted and transferred to a
greenhouse and are gradually acclimatised to normal growing condition
7
...
Species that are difficult to grow from seed can be easily grown in this way
2
...
Storage of large numbers of plants is easily
4
...
Thousands of clones with desirable qualities can be produced

!
•

Mammals similarly can be cloned
...


•

The egg cell must have its nucleus removed first

•

Dolly the sheep was the most famous example of this

!
!
!
!
!
!
!
•Dolly was
produced
by persuading one of her mother’s ova to develop into a new individual without
being fertilised by a sperm
•

Dolly was only one of many unsuccessful attempts
...
e
...


•

The concerns are that some animals carry viruses which could be transmitted to
humans

•

Ethical concerns also arise

Genetic Engineering
•

Species which include genes from another species are known as transgenic

•

Cutting out genes and recombining them into the DNA of another species usually
fungi or bacteria is the essence of genetic engineering

•

Enzymes known as restriction enzymes are used to cut DNA at specific DNA
sequences usually leaving staggered complementary sticky ends

•

They are ‘sticky’ as they are likely to recombine

•

Viruses or bacteria plasmids are then used to introduce the desired gene into the
DNA
...
Improved yield
2
...
Increased salt resistance
4
...
Resistant in general
6
...
i
...
insulin can be produced by growing
bacteria or fungi in a fermenter

•

A fermenter is a vessel used to grow microorganisms

•

They are used to produce useful substances i
...
alcohol, insulin, vinegar, penicillin
and other antibiotics along with washing up enzymes

•

They enable environmental conditions i
...
oxygen, carbon dioxide, temperature,
pH and nutrient supply to be controlled
...
Better than bleach as it may kill
microorganisms that you want

•

If the wrong bacteria contaminates the vessel they could produce toxins or be
pathogenic

•

The fermenter is filled with a suitable medium including:
1
...
The nutrients must be pure (steam sterilised and of good quality)
3
...
An extra nutrient will be fed in through here
during it
...
The
air is filtered to avoid contamination

•

Stirring paddles: mix up the contents to keep the organisms in suspension and
spread them out evenly so they get more exposure to nutrients
...
Some
fermenters use air jets in

Making Beer
•

soak barley seeds in water and lay them out on a flat surface in a malthouse

•

the seeds geminate and produce the enzyme amylase which breaks down the starch
into maltose

•

the seeds are heated, killing them but not denaturing the amylase, producing a
dried product called malt

•

the malt is ground up and mixed with hot water in a mash turn where the amylase
breaks down the starch into maltose

•

the malt is boiled (killing the enzyme) and filtered

•

hops are added for taste and yeast to ferment the sugars producing ethanol
...
‘steady state’ is the maintenance of a relatively constant internal
environment e
...
body temperature and body water content

•

the tissue fluid surrounding cells must continually contain the right balance of
chemicals so that the cells have the right raw materials for processes

•

excretory organs like the kidneys, skin and lungs all play important roles in
homeostasis

•

kidneys:
o

the main organ responsible for osmoregulation (keeping the salt and water
content of the body constant)

o

urine consists mostly of water however salts (e
...
sodium chloride) and
nitrogenous waste (e
...
urea and ammonia) are also excreted

o

urea:
▪

It is made in the body through the conversion of proteins (which
can’t be stored) into carbohydrates in the liver for storage
...


▪
▪

in the kidneys it is filtered out during the formation of urine

▪
o

the urea passes into the blood

as urea is a product of metabolism the kidneys are excretory organs

the urinary system

▪
▪

the kidneys filter the blood

▪

the ‘clean’ blood passes back into the blood stream through the
renal vein

▪

the urine passes through the ureters to the bladder

▪

two sphincters (rings of muscle: one voluntary, one involuntary)
prevent the urine flowing out of the bladder

▪

when the bladder is full the involuntary sphincter relaxes and when
the person decides to wee the voluntary sphincter relaxes

▪
o

the kidney is supplied by blood through the recall artery

the urine then flows out through the urethra

the kidneys

▪
▪

!
!
!
!
!
!
!
!

the medulla - made up of pyramids; the nephrons join together and
lead to the tip of a pyramids

▪

o

the cortex - contains many capillaries and nephrons (kidney tubules)

the pelvis - empty space in the middle of the kidney where the urine
that flows out of the nephrons collects before getting taken to the
bladder by the ureter

a nephron

▪

▪

the basement membrane - a membrane that filters out the red blood
cells and proteins but allows through water, ions and smaller
particles
...
It receives the glomerular fluid (i
...
the fluid that
passes through the basement membrane)
...
This
means that all the glucose, 99% of the water (leaving 1
...

Most of the urea is not reabsorbed and so it is concentrated in the
urine whilst ammonia is secreted into the urine as it passes along the
tubules
...
A arteriole bringing blood in is larger than the
arteriole taking the blood away
...
In cold conditions it contracts,
raising the hair upright and trapping an insulating layer of air
next to the body

•

the capillary loops in the dermis radiate more heat to the
outside world through radiation
...
This is
called vasodilation
...
This is
vasoconstriction

•

small muscles all over the body contract and relax rapidly
causing us to shiver
...


•

our metabolism also speeds up generating more heat
(adrenaline increases metabolism)

Sensitivity in Humans
•

things respond to their environment through a stimulus being picked up by a
receptor which is linked by a coordinator to an effector which produces a response
o

a stimulus is any change in the environment

o

a receptor is what detects the stimulus
...
This
changing of energy is called transduction

o

a coordinator links the receptor to the right effectors
...
g
...
There are three main types:
▪

▪

motor neurones (carry impulses from the CNS to the effector organ,
have their nucleus in a cell body in the central nervous system)

▪
o

sensory neurones (carry impulses from the receptor to the CNS, have
their nucleus in a cell body partway down the neurone which tend to
be in the same place on a nerve forming a ganglion)

connector neurones (relay impulses from one neurone to another in
the CNS, can join sensory neurones to motor neurones)

Diagram of motor neurone

▪

Dendrite - the finer branches of cytoplasmic extensions called
dendrons and they forms junctions with other neurones called
synapses

▪
▪

Myelin sheath - insulating layer of fat that is layer down by the
Schwann cells which prevents short circuits and speeds up impulses

▪
o

Axon- - the longest dendron that carries impulses to the effector
organ

Nerve-muscle junctions - special synapses found on motor end plate
that cause the muscle to contract

reflex actions

▪

reflex arc
•

stimulus is detected by receptors

•

this generates electrical impulses in the sensory neurone

•

the sensory nerve enters the CNS through the dorsal root

•

in the grey matter of the spinal cord it connects to a relay
neurone by a synapse

•

the relay neurone carries the impulse to the motor neurone
where the impulse goes across another synapse

•

the motor neurone elves the CNS through the ventral root

•

the impulse is carried to the effector organ where it is
transmitted across the nerve-muscle junctions

•

the muscle contracts

▪
▪

o

reflex actions are very quick because the impulses can travel
through the reflex arc in fractions of a second
the brain doesn’t need to start any impulses but it is made aware of
what is happening through synapses that the reflex arc neurones
make with neurones leading to the brain

Voluntary actions
▪

o

consciously contracting muscles using nerve pathways starting in our
brain

Spinal cord
▪
▪

o

grey matter - centre of the cord, contains mainly nerve cell bodies
giving it a grey colour
white matter - outer regions of the cord, contains mainly axons with
their myelin sheaths giving it a white colour

Synapses

▪

the synapse is actually the gap between nerve cells which isn’t
crossed by electrical impulses

▪

instead the message is chemically transmitted:
•

impulses arrive down the presynaptic neurone

•

neurotransmitter is then secreted from the axon (the more
impulses the more neurotransmitter)

•

it diffuses across the synapse and attaches to the membrane
of the postsynaptic neurone’s dendrite

•

this stimulates electrical impulses in the postsynaptic
neurone

•

the neurotransmitter is then broken down by enzymes

!
o

the eye
▪

structure:

•

sclera - tough outer coating of the eye which is white in
colour, protects the eye from damage

•

cornea - see-through window in the sclera, lets light in and is
responsible for some refraction

•

iris - coloured ring of tissue behind the cornea

•

pupil - hole in the iris letting light through to the inner eye

•

aqueous humour - transparent jelly/fluid found in the eye

•

choroid - dark layer containing blood vessels and pigment
cells, stops light being reflected around inside the eye

•

retina - inner most layer at the back of the eye, light
sensitive layer where light energy is transducer into
electrical, on the retina are found:
o

rod cells - work well in dim light, can’t distinguish
between colours so produces a black and white image
but good at picking up movement, found all over the
retina

o

cone cells - only work in bright light, three types
which respond to: red, green and blue light, found all
over the retina but are particularly concentrated at
the centre of the retina called the fovea

•
•
▪

lens -responsible for focusing the light onto the fovea through
refraction
blind spot - point where the optic nerve and blood vessels
enter the eye, there are no cones or rods here so no image

controlling the amount of light entering the eye

•

the iris can control the amount of light entering the eye by
changing the size of the pupil

•

in bright light the the pupil constricts
o
o

•

radial muscles relax
circular muscles contract

in dim light the pupil dilates
o

radial muscles contract

o

circular muscles relax

•
•
▪

our pupil constricts and dilates naturally in order to ensure
our eye receives enough light but not damaging amount
it is an example of a reflex action

accommodation

•

this is the process that allows us to focus on objects at
different distances

•

when an objects is far away the light comes in at a gentle
angle and so needs to be refracted less
...


•

when an object is close the light comes in at a sharp angle
and so needs to be refracted more
...
g
...


▪

diabetes sufferers have increased amounts of glucose in their urine
and tend to be very thirsty as this is the pituitary glands response to
the increased glucose concentration

▪

diabetes can be treated through insulin infections and managing the
sufferers diet

Nervous system

Endocrine system

works through electrical nerve impulses
through nerve cells

works through hormones transmitted in the blood
stream

nerve signal travel fast and have an ‘instant’
effect

hormones travel slowly and take longer to act

response is usually short lived

response is longer-lasting

impulses act on individual cells so have a
localised effect

hormones have a widespreadd effect on different
organs

Tropism
•

a growth response to directional stimulus

•

plants respond to these stimuli by adjusting the growth in their root tips

•

growth in the direction of the stimulus is positive tropism

•

growth in the opposite direction to the stimulus is negative tropism

•

there are three main types:

o
o

hydrotropism (growth in response to water)

o
•

geotropism (growth in response to gravity)

phototropism (growth in response to light)

geotropism
o
o

•

roots grow in the direction of gravity (positive geotropism), this makes them
more likely to find water, minerals and obtain anchorage
shoots grow away from the direction of gravity (in the absence of light or in
uniform light this makes it grow straight up) (negative geotropism), this
ensures they grow up through the earth to the light

hydrotropism
o

•

roots in some plants grow towards water (positive hydrotropism), this
ensures they have a good water supply

phototropism
o

shoots grow towards the direction of light (positive phototropism), this
ensure they have a good light source for photosynthesis

o

most roots show no phototropism but a few grow away from the light
(negative phototropism), as this is more likely to lead to the earth

o

coleoptiles (protective sheaths of cereal seedlings) are used to demonstrate
the system of phototropism

▪

an intact coleoptile will grow toward the light

▪

a coleoptile with the tip removed won’t grow at all

▪

a coleoptile with a covered tip will grow straight up

▪

a coleoptile with an impermeable layer (e
...
mica) placed through
one side will grow in uniform light towards the side with the
impermeable layer

▪

a coleoptile with tip replaced on gelatine will grow towards the
stimulus

▪

a coleoptile with a tip place half on half off will grow away from the
side in contact with the tip in uniform light

▪

a coleoptile with an agar block that has had a coleoptile tip placed
on it fro some time will cause the coleoptile to grow away from the
side in contact with it when placed on half and half in uniform light

o

these experiments suggest that water soluble chemicals produced in the tip
is stimulating the growth of the plant and during

o

this chemical is called auxin (or IAA) and it is a type of plant hormone (also
known as plant growth substances)
▪

in uniform sun light the auxin molecules diffuse evenly down the
stem causing the stem to grow straight up

▪

when there is a light source the auxin diffuses more to the darker
side causing it to grow more on the dark side curving the stem
towards the light

▪

auxin is also involved in geotropism along with other plant growth
substances

!

•

Clinostat
•a piece of apparatus consisting of an
electric motor turning a cork disc onto
which germinating seeds can be
attached
•the motor turns the disc very slowly
eliminating any geotropism as gravity
relative to the seeps is always
changing
•the clinostat can rotate through 90˚
meaning it can rotate both vertically
and horizontally



---