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Title: Last minute IGCSE biology revision
Description: Really useful notes to get around your head during those last minute revision periods. Aimed for the (I) GCSE levels. Also includes triple award materials.
Description: Really useful notes to get around your head during those last minute revision periods. Aimed for the (I) GCSE levels. Also includes triple award materials.
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Best notes ever from the 2016 Hundred batch
Genetic Engineering
The DNA you want to insert is cut using a restriction enzyme and the vector DNA is cut open
using the same restriction enzyme
...
This is then inserted into other cells like bacteria
...
Micropropagation
A plant with desirable characteristics is selected to be cloned and explants are taken from
the plant
...
Then the explants are
grown in agar jelly containing nutrients and hormones needed for growth
...
The small plant is then taken out of the medium
and planted in a compost to grow into an genetically identical adult plant
...
Then, a
diploid nucleus from the body cell of a sheep you want to clone is inserted into the egg cell
...
The
dividing cell becomes an embryo which is implanted into the uterus of another sheep, the
surrogate mother, to develop until it is ready to be born
...
Temperature
2
...
Carbon dioxide
4
...
Minerals ( e
...
Magnesium, Nitrates,
Phosphorus, Potassium )
Main minerals needed by plants:
1
...
Nitrate ions
> Making amino acids and proteins
> Needed for cell growth
> Lack of nitrate : Stunted stem and yellow leaves
3
...
Potassium
> Help enzymes needed for photosynthesis and respiration
> Lack of potassium : Poor flower and fruit growth and discoloured leaves
Structure of the leaf
> axy cuticle
W
is transparent to allow light to diffuse in
> Also acts as a barrier to discourage evaporation of water from the leaf
> Contains the
palisade mesophyll
which has chloroplasts
> The chloroplasts contains chlorophyll which absorbs sunlight needed for
Photosynthesis
> Denselypacked
>
Spongy mesophyll
> Has air spaces
> For efficient gas exchange / diffusion of gasses
> Contains the xylem and phloem
>
Xylem
: Transports and inerals
water m
up the stem (unidirectional)
>
Phloem
: Transports
sucrose amino acids
and
from the stem to the leaves
and the other way round (bidirectional)
>
Lower epidermis
> Has stomata surrounded by guard cells which regulates the opening and closing
of the stomata
> Stomata controls what goes in and out of the cells
> Open during the day to let CO2 in and O2 out of the leaves
> Closes during the night to prevent water loss
Adaptations of the structure of a leaf:
> Large surface area for diffusion
> Chloroplasts
> Stomata, allowing gas exchange
> Plant cells are thin and flat so as much light can be absorbed as possible
Requirements for growth:
> Mineral ions (move up the xylem through active transport)
> Nitrates needed for amino acids (proteins) to make magnesium
> Magnesium then needed to make chlorophyll
Respiration
Aerobic respiration
[ with oxygen ]
Glucose + Oxygen
→ Carbon dioxide + Water
C6 H12 O6 + 6O2
→ 6CO2 + 6H2O
> All of the energy released by glucose is fully broken down
...
Anaerobic respiration
[ without oxygen ]
YeastGlucose > Ethanol + Carbon dioxide (+ ENERGY)
:
: C6 H12 O6
→ 2 C2 H5 OH + 2 CO2
AnimalsGlucose > Lactic Acid (+ ENERGY)
:
: C6 H12 O6
→ 2 C3 H6 O3
> Takes place when the
heart and lungs cannot work fast enough provide the oxygen
to
needed for respiration
...
g
...
>
Lactic acid accumulates in muscles making them sore
...
> Helps break down lactic acid into CO2 and H2O
>
Recovery periodTime
: taken for
lactic acid to be removed
and for the
breathing and
heart rate to return to normal
...
> Heat the mixture
...
> Polysaccharides are used for
storage in a duration of a longer time
...
Uses of fats
1
...
Protection of organs
3
...
> Therefore, the
active site no longer fits with the substrate
it is meant to be
breaking down
...
Hormones
2
...
Nutrients such as water, glucose, amino acids, minerals and vitamins
4
...
> White blood cells
> Takes care of your immune system Keeps you free from diseases and attacks by
microbes
...
Help phagocytes recognize them better
2
...
Causes bacterial cells to burst open
4
...
)
> Phagocytes
> They engulf and digest the pathogens
> Recognize the pathogens by the antibodies on the antigens (on the pathogen’s
surface) that the lymphocytes had produced in the first place
...
Injury
...
Arrival of platelets
...
Platelets break open
...
If calcium ions are present, thrombin is formed
...
Thrombin acts on fibrinogen to turn it into fibrin
...
Fibrin forms mass of insoluble protein threads which forms clot
...
Scab as red blood cells become trapped in it
...
Eye
> Sclera is white
> Acts as a tough protection from injury
> Cornea is transparent to allow light to pass through it
> Is attached to the sclera
> In dim light, circular muscles relaxes and
radial muscles contracts
...
Nitrogen cycle
Nitrogen Cycle
> The atmosphere contains
78% nitrogen gas
> Very unreactive so can’t be used directly by plants and animals
...
Nitrogen fixation : Turning N2 in the air to nitrogen compounds in the soil by :
> LIGHTNING : A lot of energy in a bolt of lightning that it is enough to make
nitrogen react with O2 in the air to form nitrates
> Nitrogen Fixing Bacteria in roots and soil
Four types of bacteria in the nitrogen cycle:
1
...
NITRIFYING BACTERIA
> Turn ammonia in decaying matter into nitrates
3
...
DENITRIFYING BACTERIA
> Turn nitrates back into N2 gas
> Utterly useless for living organisms
Example questions :
1
...
Find a gene responsible for the desired trade/ characteristics
2
...
Use the same restriction enzyme to cut out plasmids
4
...
To form a recombinant DNA
6
...
Bacteria acts as a vector
Similarly genetic modification
1
...
Use the same restriction enzyme to cut out the plasmids from a bacterium, generating
complementary sticky ends
3
...
A recombinant plasmid is produced
5
...
Red Blood Cells Adapted:
1
...
Enucleate no nuclues (O2 space)
3
...
Biconcave (Large surface area, decreased diffusion distance pass through capillaries
easily, increase SA
...
Describe the process of cloning
1
...
Extract the
nucleus from an udder cell of a donor sheep
3
...
the nucleus and egg cell together
Fuse
using electricity
5
...
Once the
embryo has developed
7
...
Explain why smoking is bad for the body [56 marks]
1
...
Causes emphysema
> Walls of the alveoli are damaged and breaks down to form large irregular air spaces
> Inefficient gas exchange
3
...
4
...
Affects the circulatory system
> Higher chances of getting a stroke or heart attacks
6
...
State the differences between meiosis and mitosis [6 marks]
Mitosis
1
...
Genetically identical cells are produced
3
...
Two daughter cells
5
...
Occurs in the formation of body cells
7
...
For growth and repair of body tissues
Meiosis
1
...
Genetically nonidentical cells
3
...
Four daughter cells / gametes
5
...
Half the number of chromosomes
7
...
For sexual reproduction
6
...
Pathogens have antigens
on their cell surfaces
2
...
Phagocytes engulf the pathogens
4
...
Natural selection [46 marks]
1
...
g
...
The pesticide, which is the selection pressure, selects for the pests resistant to it, and
selects against the pests not resistant to it
...
The pests that are resistant to it survive, and reproduce/ mate to pass on the allele
8
...
Rise in global temperature
>
Ice caps would melt
> Causes flooding and a
rise in sea level
2
...
Explain how the structure a root hair cell is adapted to absorb water
...
Large surface area to volume ratio due to elongation
...
Therefore, more osmosis takes place
...
Describe the structural differences between arteries and veins
1
...
Arteries are under higher pressure compared to veins
> Therefore, arteries have thicker walls and stronger muscles to pump blood to the
rest of the body
> Veins have thin wall which eases diffusion
3
...
Give three ways in which villi are adapted to absorb small food molecules
1
...
Walls are one cell thick
> Shorter diffusion distances
3
...
Permeable
5
...
Describe and explain how the small intestine is adapted for absorbing digested
foods
1
...
Has villi which contains microvilli
> Increased surface area
3
...
diffusion / active transport / osmosis
5
...
(blood flow) maintains concentration gradient /
maintains diffusion gradient
7
...
Describe how selective breeding can used to breed cattle with high yield of milk
...
Select a cow which produces high yield of milk and
breed it with another cow which
produces a high yield of milk
...
Offspring produced is likely to produce a high milk yield
...
Repeat
the process over many generations
...
14
...
Lack of water is detected by the
hypothalamus in the brain
...
Triggers the
pituitary gland to release ADH
...
The ADH travels to the
kidneys where it
increases the permeability of the walls of the
collecting duct
...
Therefore, ore water is reabsorbed
m
back to the blood
...
Urine becomes more concentrated
...
If there is more water, collecting duct becomes less permeable to allow more water to be
released
...
Explain how the structure of the root hair cell is adapted to absorb water from
the soil
...
Large surface area
2
...
Osmosis / Diffusion
16
...
Obesity / increase in weight
2
...
High blood pressure / stroke / heart disease / raised cholesterol
4
...
Joint damage / arthritis
6
...
Exercise helps a person to lose weight
...
1
...
Exercise requires energy for respiration
3
...
Explain how the rate of transpiration is affected by changes in the
environment
...
High
humidity
decreases rate of transpiration
> Reduced concentration gradient
> Diffusion of water vapour out of the leaf slows down because the air is already
moist / filled with water vapour
...
High increases rate of transpiration
wind
> Increased concentration gradient
> Water vapour is removed quickly by air movement
> Speeds up diffusion of water vapour out of the leaf
3
...
High increases rate of transpiration
light
> Stomata open wider
> Allows more CO2 into the leaf for photosynthesis
19
...
1
...
2
...
3
...
4
...
5
...
20
...
)
1
...
> Chlorophyll absorbs sunlight needed for photosynthesis
...
> Hence, plants are known as producers
...
If maggots feed on the palisade mesophyll, there will be
lower chlorophyll
...
As a result, there will be
lower photosynthesis
...
Therefore, there will be
lesser production of food / fruit
by plants
...
Equation for photosynthesis :
6CO2 + 6H2O
→ 6O2 + C6 H12 O6
> Given that equation, if there is less photosynthesis, there will be
less oxygen and
glucose
produced by the plant
...
Describe how the process of micropropagation (tissue culture) can be used to
produce plants with desirable characteristics
1
...
In containing
agar
nutrients, minerals and hormones
...
This stimulates growth in the roots even when the plants do not have roots when it is put
in
...
The minerals and nutrients also helps the plants to develop and grow
...
It is important to
provide sunlight to the plants during the growing process and place it in a
sterile
environment
...
It is also important to
control the other factors affecting growth such as
humidity and
temperature
...
Give two advantages of using micropropagation rather than using seeds to
produce plants with desirable characteristics (selective breeding)
...
Quick
2
...
3
...
4
...
23
...
1
...
> Time consuming and uses a lot of energy
2
...
3
...
3
...
24
...
1
...
2
...
3
...
25
...
Too small, literally on the mark scheme
...
Vaccination
1
...
2
...
3
...
>
Not at risk of a disease
...
Why does biomass / energy decrease as you go up the pyramid?
Biomass: mass of living things
Biomass:
1
...
Not digested (ex
...
Therefore some biomass is lost through egestion
Energy:
1
...
Movement
3
...
28
...
C
: A range of light intensity
> dark light, [ aluminium foil wrapped test tube ] , bright light etc
O
: Same mass of leaves, same species of leaves, same size of leaves
R
: Repeat the experiment at least 3 times and find the average
M : Observe the change of hydrogen carbonate indicator after a given period of time ( 2 days
e
...
)
S
: Same concentration of hydrogen carbonate indicator
: Same volume of hydrogen carbonate indicator
Conclusion
:
1
...
The tube where the hydrogen indicator remained
ORANGE
:
>
CO2 levels is the same
3
...
Explain the difference in meaning between cell, organelle, organism, tissue and
organ
...
Understand the structure and function of the following organelles: cell membrane,
plant cell wall, nucleus, chloroplast, mitochondrion, sap vacuole, ribosome and also
the function of the cytoplasm
...
Give advantages of using biological control rather than using pesticide
Title: Last minute IGCSE biology revision
Description: Really useful notes to get around your head during those last minute revision periods. Aimed for the (I) GCSE levels. Also includes triple award materials.
Description: Really useful notes to get around your head during those last minute revision periods. Aimed for the (I) GCSE levels. Also includes triple award materials.