AQA GCSE Biology - B5
How are gibberellins used commercially? - ANS-Controlling dormancy - Seeds can be
treated with gibberellins to alter dormancy and make seeds germinate at times of the year
they wouldn't normally. It also helps to make sure that all seeds in a batch germinate at the
same time.
Inducing flowering - There are some plants that require certain conditions to flower. If these
are treated with gibberellins, they will flower regardless. Gibberellin can also be used to grow
bigger flowers.
Growing larger fruit - Gibberellin can be used to make seedless varieties of fruit grow larger
than they normally would
\How can hormones be used to increase fertility? - ANS-FSH and LH can be given to women
in a fertility drug to stimulate ovulation. However, it doesn't always work and can be quite
expensive, and too many eggs could be stimulated, resulting unexpected multiple
pregnancies
\How can vision defects be treated? - ANS-Glasses, contact lenses, laser eye surgery,
replacement lens surgery
\How can you investigate plant growth responses? - ANS-Grow cress seeds in petri dishes
under a light
\How do barriers reduce fertility? - ANS-They stop sperm reaching the egg.
Condoms and female condoms are worn during intercourse to prevent sperm entering the
vagina. They are the only form of contraception that will prevent against sexually transmitted
diseases.
Diaphragm is a shallow plastic cup that fits over the cervix to form a barrier. It has to be used
with spermicide.
Spermicide can be used alone as a form of contraception, but is only 70-80% effective
\How do scientists study the brain? - ANS-Studying patients with brain damage, electrically
stimulating the brain and MRI scans
\How does a reflex arc work? - ANS-Stimulus is detected by receptors, causing impulses to
be sent along a sensory neurone to a relay neurone in the CNS. Impulses reach a synapse
between sensory neurone and relay neurone, causing neurotransmitters to be released,
which diffuse across the gap and cause an impulse to be sent down the relay neurone. The
same thing happens when the impulses reach a synapse between the relay neurone and the
motor neurone. The impulses travel down the motor neurone to the effector, which produces
a response
\How does gravitropism work? - ANS-When a shoot is growing sideways, gravity produces
an unequal distribution of auxin in the tip, with more auxin on the lower side. This causes the
shoot to bend upwards. A root growing sideways will also have more auxin on its lower side.
But in a root auxin inhibits growth, meaning cells at the top elongate faster and the root
bends downwards
\How does negative feedback work? - ANS-Receptor detects a stimulus - level is too high or
low. Coordination centre receives and processes the information, then organises a response.
Effector produces a response and restores the optimum level.
, The effectors will continue to produce this response for as long as they are being stimulated
by a coordination centre. This sometimes leads to the opposite problem occuring, in which
case the negative feedback process starts again
\How does phototropism work? - ANS-When a shoot tip is exposed to light, more auxin
accumulates on the side that's in the shade, making the shoot grow faster on the shaded
side and bend towards the light
\How does the body detect extreme temperature and react to it? - ANS-Temperature
receptors in the skin and in the thermoregulatory centre detect that the core body
temperature is too high or low. The thermoregulatory centre acts as a coordination centre - it
receives information from temperature receptors and triggers effectors automatically.
Effectors produce a response to counteract the change
\How does the eye focus on distant objects? - ANS-The ciliary muscles relax, allowing the
suspensory ligaments to pull tight, making the lens thinner and less curved, decreasing the
amount by which it refracts light
\How does the eye focus on near objects? - ANS-The ciliary muscles contract, which
slackens the suspensory ligaments, making the lens fatter and more curved, increasing the
amount by which it refracts light
\How does the eye respond to light intensity? - ANS-In bright light, reflex is triggered that
causes the circular muscles in the iris to contract and the radial muscles to relax, making the
pupil smaller.
The opposite happens in low light
\How has IVF developed? - ANS-Advances in microscope techniques, developments of
micro-tools and the development of time-lapse imaging in incubators have meant that IVF
has become more successful
\How has research into the brain helped people? - ANS-Developed treatment of disorders of
the nervous system. For example, electrical stimulation can reduce muscle tremors caused
by Parkinson's
\How is auxin used commercially? - ANS-Killing weeds - Selective weedkillers have been
developed using auxins that disrupt growth patterns in broad-leaved plants, which most
weeds are in contrast to most grasses and grains, and kills them.
Growing from cuttings with rooting powder - If you add auxins to cuttings of plants and plant
them, they will rapidly produce roots and become a new plant. This enables clones to be
produced very quickly.
Growing cells in tissue culture - Hormones such as auxins need to be added to a growth
medium to stimulate plants cells in it to divide to produce a clone
\How is concentration of urine changed to control water content in the body? - ANS-A
receptor in the brain detects that the water content is too high or low. The coordination
centre in the brain receives the information and coordinates a response. The pituitary gland
releases more or less ADH, so more or less water is reabsorbed from the kidney tubules
\How is ethene used commercially? - ANS-It is used to speed up the ripening of fruits by
controlling cell division and stimulating enzymes that cause the fruit to ripen. This means that
fruit can be picked when it is unripe, and therefore less easily damaged, and made to ripen
just as they go on sale.
Alternatively, chemicals can be added to fruits in storage that block ethene's ripening effect
or reduce the amount of ethene that a fruit can produce. There are also some chemicals that
react with ethene to remove it from the air
\How would you investigate reaction times? - ANS-Ruler drop test or computer test
\In which solution does crenation occur? - ANS-Hypertonic
How are gibberellins used commercially? - ANS-Controlling dormancy - Seeds can be
treated with gibberellins to alter dormancy and make seeds germinate at times of the year
they wouldn't normally. It also helps to make sure that all seeds in a batch germinate at the
same time.
Inducing flowering - There are some plants that require certain conditions to flower. If these
are treated with gibberellins, they will flower regardless. Gibberellin can also be used to grow
bigger flowers.
Growing larger fruit - Gibberellin can be used to make seedless varieties of fruit grow larger
than they normally would
\How can hormones be used to increase fertility? - ANS-FSH and LH can be given to women
in a fertility drug to stimulate ovulation. However, it doesn't always work and can be quite
expensive, and too many eggs could be stimulated, resulting unexpected multiple
pregnancies
\How can vision defects be treated? - ANS-Glasses, contact lenses, laser eye surgery,
replacement lens surgery
\How can you investigate plant growth responses? - ANS-Grow cress seeds in petri dishes
under a light
\How do barriers reduce fertility? - ANS-They stop sperm reaching the egg.
Condoms and female condoms are worn during intercourse to prevent sperm entering the
vagina. They are the only form of contraception that will prevent against sexually transmitted
diseases.
Diaphragm is a shallow plastic cup that fits over the cervix to form a barrier. It has to be used
with spermicide.
Spermicide can be used alone as a form of contraception, but is only 70-80% effective
\How do scientists study the brain? - ANS-Studying patients with brain damage, electrically
stimulating the brain and MRI scans
\How does a reflex arc work? - ANS-Stimulus is detected by receptors, causing impulses to
be sent along a sensory neurone to a relay neurone in the CNS. Impulses reach a synapse
between sensory neurone and relay neurone, causing neurotransmitters to be released,
which diffuse across the gap and cause an impulse to be sent down the relay neurone. The
same thing happens when the impulses reach a synapse between the relay neurone and the
motor neurone. The impulses travel down the motor neurone to the effector, which produces
a response
\How does gravitropism work? - ANS-When a shoot is growing sideways, gravity produces
an unequal distribution of auxin in the tip, with more auxin on the lower side. This causes the
shoot to bend upwards. A root growing sideways will also have more auxin on its lower side.
But in a root auxin inhibits growth, meaning cells at the top elongate faster and the root
bends downwards
\How does negative feedback work? - ANS-Receptor detects a stimulus - level is too high or
low. Coordination centre receives and processes the information, then organises a response.
Effector produces a response and restores the optimum level.
, The effectors will continue to produce this response for as long as they are being stimulated
by a coordination centre. This sometimes leads to the opposite problem occuring, in which
case the negative feedback process starts again
\How does phototropism work? - ANS-When a shoot tip is exposed to light, more auxin
accumulates on the side that's in the shade, making the shoot grow faster on the shaded
side and bend towards the light
\How does the body detect extreme temperature and react to it? - ANS-Temperature
receptors in the skin and in the thermoregulatory centre detect that the core body
temperature is too high or low. The thermoregulatory centre acts as a coordination centre - it
receives information from temperature receptors and triggers effectors automatically.
Effectors produce a response to counteract the change
\How does the eye focus on distant objects? - ANS-The ciliary muscles relax, allowing the
suspensory ligaments to pull tight, making the lens thinner and less curved, decreasing the
amount by which it refracts light
\How does the eye focus on near objects? - ANS-The ciliary muscles contract, which
slackens the suspensory ligaments, making the lens fatter and more curved, increasing the
amount by which it refracts light
\How does the eye respond to light intensity? - ANS-In bright light, reflex is triggered that
causes the circular muscles in the iris to contract and the radial muscles to relax, making the
pupil smaller.
The opposite happens in low light
\How has IVF developed? - ANS-Advances in microscope techniques, developments of
micro-tools and the development of time-lapse imaging in incubators have meant that IVF
has become more successful
\How has research into the brain helped people? - ANS-Developed treatment of disorders of
the nervous system. For example, electrical stimulation can reduce muscle tremors caused
by Parkinson's
\How is auxin used commercially? - ANS-Killing weeds - Selective weedkillers have been
developed using auxins that disrupt growth patterns in broad-leaved plants, which most
weeds are in contrast to most grasses and grains, and kills them.
Growing from cuttings with rooting powder - If you add auxins to cuttings of plants and plant
them, they will rapidly produce roots and become a new plant. This enables clones to be
produced very quickly.
Growing cells in tissue culture - Hormones such as auxins need to be added to a growth
medium to stimulate plants cells in it to divide to produce a clone
\How is concentration of urine changed to control water content in the body? - ANS-A
receptor in the brain detects that the water content is too high or low. The coordination
centre in the brain receives the information and coordinates a response. The pituitary gland
releases more or less ADH, so more or less water is reabsorbed from the kidney tubules
\How is ethene used commercially? - ANS-It is used to speed up the ripening of fruits by
controlling cell division and stimulating enzymes that cause the fruit to ripen. This means that
fruit can be picked when it is unripe, and therefore less easily damaged, and made to ripen
just as they go on sale.
Alternatively, chemicals can be added to fruits in storage that block ethene's ripening effect
or reduce the amount of ethene that a fruit can produce. There are also some chemicals that
react with ethene to remove it from the air
\How would you investigate reaction times? - ANS-Ruler drop test or computer test
\In which solution does crenation occur? - ANS-Hypertonic
