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Howlers - Summer 2019

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How Succession occurs

Producers begin to eat the plant ...

When larger plants occupy the land, they can block wind

Eventually a final species will begin to inhabit the environment

Species populations stop growing at the carrying capacity

The pioneer species is usually the largest/strongest species, e.g. trees

The pioneer species tends to be very specific

When a climax community is reached it can support an ecosystem

This will let the next primary species develop

When the environment can't support any more life it is known as the climax community

How a single base substitution causes a change in the structure of a polypeptide

This would change the polypeptide like a chain reaction

Haemopoietic stem cell transplantation

This means they can replicate this new normal shaped haemoglobin

This is effective because stem cells take a long time to die

Stem cells have no specific use

This means their immune system will last longer

Gene therapy for sickle cell disease

This method does not require a doner

This will result in the stem cells differentiating into healthy haemoglobin

Child can produce its own stem cells from beta polypeptide gene

The body, once genetically modified stem cells are injected back into the child, will recognise the functional from the faulty, disregarding the faulty

Effects of indole acetic acid IAA on growth of oat seedlings

Plants use IAA to bend

In the roots there would be more growth as roots try to find nutrients

IAA molecules in shoots grow against gravity

Why the shoot tip was removed from the seedling

This allows the end of the shoot to be exposed in order for IAA to be taken up by the plant

The shoot would be able to grow from both ends

Each shoot is different and could grow in different directions

The shoot tips respire aerobically but without them they would have to respire anaerobically

The student removed the shoot tip to remove the opening and closing of stomata to avoid this extraneous variable

The shoot has the best enzyme acceptors that could be needed to collect nutrients and water

The shoot tip contains stem cells

Reason why glucose added

To allow same conditions for growth, for level playing fields

Plants require glucose for photosynthesis

Comparison of effects of IAA on shoot, and results difference if lengths of root were used

The root tip has the greatest concentration of chloroplasts full of chlorophyll

Roots would have grown more as they do not need light for IAA to work as they are constantly in the dark

The shoot could not photosynthesise for long in the dark

Roots require different auxins as they grow downwards rather than up

There would have been more downwards growth from the roots

If the root tip was longer it would have a greater force of gravity acting on it

Roots don't respond to IAA but they do to gravity

If different lengths of root had been used it would suggest that the longest root would grow the least as IAA would have further to travel up the root

If roots are used then ends of roots must be removed

If it differed in length then results wouldn't be fair

This would make them want to grow downwards but they were blocked by the petri dish

As roots are naturally in the dark all the results would increase

The results would be the opposite as roots grow against the projection of light

Evaluation of conclusion

We have no significant different bars

Effect of inorganic phosphate on release of calcium ions within muscle

The calcium ions synthesise ATP

Calcium ions cause myotropism wrapped around actin to move

The calcium ions bind to tropomyosin to move it out of actin so myosin can go in

This means less actinomyosin brides are formed

This causes trypsin to move and expose the binding sites

The only factor affecting the force of muscle contraction was not only the pH difference but also the temperature

Calcium ions also cause the myosin head to be released from tropysomin

A decrease in calcium ions means that depolarisation of the myosin head can occur

There will be a shorter frequency of calcium ions sent to the SAN

Less bone density . . . Less area for muscles to attach to and less room for them to contract

Why converting pyruvate to lactate allows continued production of ATP

Lactation involves the release of CO2 and causes the release of ATP

This means fewer myoglobin heads will attach and detatch, causing a lower force

The role of glucagon in gluconeogenesis

Glucagon is secreted when bodily glucose levels drop

How increasing cell's sensitivity to insulin will lower the blood glucose concentration

Increasing the sensitivity would mean less glucose is released from the pancreas

The hormone insulin heightens the blood glucose levels over a certain threshold

This will make the cells in the pancreas think there is the right volume of insulin in the body therefore will produce less glucose

This causes more glucose to be broken down in the blood

Insulin will be released more accurately when blood glucose gets high

Liver cells will convert more glucose into glycogen. Then the glycogen can be released into the blood and lower the glucose concentration.

If the cell is sensitive to insulin it will enable insulin to break down blood glucose

Slight changes in glucose will trigger a positive/negative feedback response

This will make the cell break down glucose into glycogen more quickly

Liver cells will allow glucose to be converted into glycerol

How inhibiting adenylate cyclase may help to lower the blood glucose concentration

It may inhibit it after insulin has done its duty

If you inhibit adenylate cyclase the cell membrane cannot bind to receptors inside the cell to activate it

So there will be little or no chains of reactions after this

Adrenaline has a complementary shape to liver cells

This enzyme is used in the reaction to change large polymers into glucose

Inhibiting this enzyme means that insulin would be free to go about its functions as normal

Explanation that the gene for body colour is not on the X chromosome.

There is no imbalance of colour between genders

Calculation of % heterozygotes

p2 hetero dominant 2pq homo q2 hetero recessive


This causes the H2O to split into 2 electrons

Photons hit chlorophyll in the thylakoids

The higher energy level forces electrons out of the cell

The ray of light causes the electron to gain energy and become more positive

Electrons become ionised

The electrons fall down the energy transport chain

The light energy bleaches the photosynthetic pigments

Light is absorbed by electrons which excites them

This photoionises the electrons

Light excites the chloroplast

This is the process of molecules gaining erections and becoming excited

This causes the hydrogen to break down into oxygen, hydrogen and electrons which are used for the proton pump

This excites the chlorophyll and electrons causing electrons to move out into the intermembrane space

Light is absorbed by chlorophyll from the sun

The electrons gain positive charge and move around the membrane

Electrons gain charge from light

This light energy is passed on to electrons and excites them

This leaves the chlorophyll with a positive charge (election vacancy)

Two e- leave the chloroplast, making it more positive

Light is used to split the ions

Sunlight hits the ions in the plant and excites them

Light is detected by pigments in the chlorophyll

This causes the electron to move out of the chloroplast

The plant absorbs light and turns it into energy to produce photosynthesis

Oxygen passes through the electron transport chain

Water is split by light. This produces H+, electrons and carbon dioxide.

The light energy excites electrons causing a Cl- ion to form

Light hits the chlorophyll which is loaded with electrons

Electrons get energy and jump down the ETC

The electrons are ionised by light

During the LDR, the NADP binds with the Pi which then becomes reduced. The NADP had picked up the light, and the Pi ionised it.

Electrons in the ETC become excited by light energy

Use of pencil line in chromatography

Pencil would not be separated into pigments

The ink is soluable and would travel up the paper as well, where as lead isn't so it won't move

Ink contains some coloured dye which will also evaporate when placed in a tank containing solvent, and will give false positives

Chromatographic separation of photosynthetc pigments

Gently dipping the bottom of the pigment in solvent

This can be done via the use of osmosis on the chromatography paper

The solution is now heated

The solvent will move up the paper separating the pigments depending on their colour

Fill a tube to a shallow point full with solvent

Place paper in solvent so origin is just submerged

Fold the top of the paper over a pencil and balance it over beaker containing solvent

Mark each pigment differently

Put acid in the beaker and attach the paper to the edge of the beaker with a paperclip

The paper would be covered in solvents such as ethanol

Place a solvent on the origin line which will travel up the chromatogram

Advantage of different coloured pigments in leaves

Different pigments in leaves attract insects for pollination

So photosynthesis can take place at different times of the day

Green would show it is chlorophyll whilst other colours would show other uses

So the plant can dissolve different colours of light

Different light waves can be absorbed

Allows for adaptation and camouflage

Able to pick up different waves of light

The green pigment is reflected

So some plants absorb more chlorophyll than others

So bees can distinguish which plants need to be pollinated more easily

This could be a courtship behavious which attracts some species and able to reproduce seccessfully

Could allow for a certain amount of camouflage as a way of protecting itself from being eaten

Able to absorb different wavelengths of light so can still photosynthesise in low light intensity conditions

It maximises the efficiency by which it is converted into glucose

Different concentrations of light can be absorbed

Each pigment requires a different wavelength to be broken down

Different wavelengths of light will pass through them, producing different chromatogram points

Discourages predators as warning colours

More light can be absorbed in different parts of the leaf

A DNA probe

It is similar stranded

How DNA is broken down into smaller fragments

Enzyme restricted endonuclease

Reverse endonuclease

Why DNA is separated into single strands

They will move faster if lighter

How the size of different viral fragments was determined

An electric shock is used to move the DNA fragments to the positive cathode

How to measure population of sundew plants

Mark release recapture

Carry out a statistical test to ensure results are not due to chance

Gather the size of one population and then generalise it to the whole population

Measure the biomass of the small marsh then calculate the biomass of sundew alone

Times each number by the total area

Repeat the process until the mean population size starts to stabilise

Carry out a statistical test (t-test) to ensure these results are not due to chance

Use a generator to get various co-ordinates

Times this figure by the area of the population

You could use a Punnet square over the area

How damage to myelin sheath of neurones can cause muscular paralysis

Impulses travel along the myelin sheath of neurons

The myelin sheath acts as a conductor around the neuron

Neurones require the myelin sheath to protect the auxin which is what connects the myelinated neurone together

The body will not know when to open the Na+ gates

Nerve impulse wouldn't be produced do to damage

This can block the impulse from passing from axon to axon so the neurone doesn't reach the synapse

The myelin sheath aids the transmission of neurons along an axon

Explanation of heart rate irregularities

The autonomic nervous system consists of muscles

If a person is exposed to direct sunlight there may be more epigenetic tags in their DNA.

As muscles are affected the stronger beat of the left side of the heart is reduced

The myelin sheaths send impulses to the heart

Signals to the valves within the heart may be prevented if the myelin sheath is damaged

The contractions may be out of sink

The neurone synapse causes a stimulus and then the receptors are informed

The impulse generated in the SAN travels too quickly, without a delay through non-conducting tissue

The various chambers of the heart need to beat in a specific order

This means impulses are not always getting to the brain

Impulses are sent to the medulla oblong-gata

The SAN transmits impulses to the carotid arteries

The regulation of systole, systole and diastole is interrupted

They may not be able to squeeze the muscles round the atria

The sun will not receive an electrical impulse

The nerve system no longer recognises when it is meant to trigger the heart to beat

Neurones that are inflicted may affect the sinoatrial mode

The impulses are sometimes stopped or at least compromised

How a drug could cause a reduction in the concentration of the protein huntingtin

This causes the protein to die

As a result non-functional amino acids will be produced

Advantages of DNA drug injection over taking a pill

DNA is a protein and it would be digested by protease enzymes

Taking a pill may not always go to the brain

A pill is very time-consuming

Reasons why drug should not be considered a cure

It is caused by a dominant allele which is hereditary so any offspring will still be affected

It could be in someone's genetics from birth


If an ancestor started getting symptoms then changed their lifestyle, it may have loosened the DNA around the histone allowing it to be copied

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