Topic 5 - homeostasis and response Flashcards
1
Q
what is homeostasis
A
the regulation of conditions inside your body and cells to maintain a stable internal environment in response to changes in both internal and external conditions .
to maintain optimum conditions for biological functions
2
Q
what three things need to be regulated in your body
A
body temperature
blood glucose level
water content
3
Q
what are the two automatic control systems
A
nervous system
hormonal /chemical system
4
Q
what three parts make the automatic control systems
A
receptors
coordination centres
effectors
5
Q
what is negative feedback
A
automatic control systems keep your internal environment stable using a mechanism called negative feedback .
when the level of something gets too high or low your body uses negative feedback to bring it back to normal
6
Q
exaplin how the auromatic control system works when a stimulus level is too high or low
A
high :
receptor cells detect a stimulus level is too high
the coordination centre revieves and processes the infornmation then organises a response
effector produces a response which counteracts the change and restores optimum level
the level decreases
low:
receptor detects a stimulus level is too low
the coordination centre recieves and processes the infornmation then organises a response
effector produces a response which counteracts the change and restores the optimum level - the level increases
7
Q
In vertebrates, what does the Central nervous system consist of
A
brain and spinal cord
8
Q
what are sensory neurones
A
neurons that carry infornmation as electrical impulses from the receptors to the Central nervous system
9
Q
what are motor neurones
A
the neurones that carry electrical impulses from the CNS to the effectors
10
Q
what are effectors
A
all your muscles and glands that respond to nervous impulses
11
Q
what are receptors
A
the cells that detect stimuli
there are many different types such as tast receptors on tongue and sound receptors on ear
12
Q
how do the two effectors respond in different ways
A
muscles co tract
glands secrete hormones
13
Q
what is the CNS and explain how it works when a small bird is eating some seed and a cat approaches it
A
The CNS is a coordination centre - it recieves infornmations from the receptors and then coordinates a response. the respons is carried out by the efectors .
example .
a small bird is eating some seeds
it spots a cat (this is the stimulus )
the receptors in the birds eye are stimulated. sensory neurones carry the infornmation from the receptors to the CNS .
The CNS decides what to do about it .
the CNS sends infornmation to the muscles in the bird’s wings (effectors ) along the motor neurones . the muscles contract and the bird flies away to safety.
14
Q
what are synapses and how do they work
A
the connection between two neurones is called a synapse .
the nerve signal is transferred by chemicals which diffuse across the gap.
these chemicals then set off a new electrical signal in the next neurone.
15
Q
what are reflexes
A
rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain.
16
Q
give examples of how reflexes can prevent you from getting injured
A
if someone shone a bright light at your eyes, your pupils automatically get smaller so less light enters your eyes.
if you get a shock. your body releases adrenaline hormone auromatically.
17
Q
what is the passage of infornmation in a reflex called
A
reflex arc
18
Q
describe what happens in terms of reflexes when a bee stings someone.
A
- when a stimuluse (the bee sting) is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS (spinal cord)
- when the impulses reach a synapse between the sensory neurone and relay neurone, they trigger chemicals to be released .these chemicals cause impulses to be sent along the relay neurone.
- when the impulses reacg a synapse between the relay neurone and a motor neurone , the smae thing happens/ chemicals are released and cause impulses to be sent along the motor neurone.
- the impulses then travel along the motor neurone to the effector (muscle in this case )
- the muscle then contracts and moves your hand away from the bee.
19
Q
describe how you would carry out an investigation to measure reaction time
A
- person 1 sits on a stool with good upright posture , they then place the forearm of their dominant arm on a table with their hand over the edge.
- person 2 holds a ruler vertically with the 0 mark between persone 1’s thumb and forefinger
- person two drops the ruler at a random time
- person one has to catch it as quickly as possible
- record the measurement on the ruler that is equal to the top of person 1’s thumb
- repeat and calculate the mean
- test with different people
independant variable - people measured
dependant variable -reaction time
control - starting distance between thumb and forefinger, measurement, conditions in room
repeat with different inddependant variables
e.g. non dominant hand , caffeine intake ( give set volume of caffeine e.g. coke and wait half an hour then start experiment - compare with no caffeine )
20
Q
how can reaction time be measured using a computer and what are the benefits of this ?
A
simple computer tests can also be used .
e.g. person has to click the mouse as soon as they see a stimulus on the screen
computers give a more precise rection time becasue they remove the posibility of human error.
as they can record in milliseconds it can give a more accurate result.
using computers removes the possibility that the person can predict when to respond
21
Q
what is the cerebral cortex
A
the outer wrinklybit
responsible for things like consciousness . intelligence , memory and language
22
Q
what does the hypothalamus do
A
regulates body temperature
sends signals to the pituitary gland
23
Q
what does the medulla do
A
controls unconscious activities
breathing
heartbeat
24
Q
what does the cerebellum do
A
responsible for muscle contraction
25
what different methods do scientists use to study the brain
study patients with brain cancer
if a small part of the brain has been damaged , the effect this has on the patient can tell you a lot about what the damaged part of the brain does.
electrically stimulating the brain
the brain can be electrically stimulated by pushing a tiny electrode into the tissue and giving it a small zap of electricity. By observing what stimulating different parts of the brain does , it is possible to get an idea of what those parts do .
MRI scans
a magnetic resonance imaging scanner is a bag tube like machine that can produce a very detailed picture of the brains structure .
scientists use it to find out what areas of the brain are active when people are doing things like listening to music or trying to recall a memory .
26
what are the advantages and disadvantages of studying the brain
knowledge of how the brain works has led to the development of treatments for disorders of the nervous system . for example , electrical stimulation of the brain can help to reduce muscle tremors caused by nervous system disorderss such as parkinson's disease
the investifation of brain function and any treatment of thje brain dammage or disease is difficult.
also carries risks such as physical dammage to brain or increased problems with brain function e.g. difficulty with speech
27
what are each of these parts of the eye
sclera
cornea
iris
lens
retina
ciliary muscles
suspensory ligaments
optic nerve
sclera - tough , rupporting wall of the eye
cornea - transparent outer layer found at the front of the eye it refracts (bends ) light into the eye.
iris - contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eyes
lens - focuses the light onto the retina
retina - contains receptor cells sensitive to light intensity and colour
ciliary muscles and suspensory ligaments - controll the shape of the lens
optic nerve - carries impulses from the receptors on the retina to the brain
28
what happends when light receptors in the eye detect a very bright light .
a reflex is triggered that makes the pupil smaller .
the circular muscles in the iris contract and the radial muscles relax .
this reduces the amount of light that can enter the eye.
29
what happens when light receptors in the eye detect dim light
the radial muscles contract and the circular muscles relax which makes the pupil wider
30
what is accomodation
Accommodation is the process of changing the shape of the lens to focus on near or distant objects.
31
how does the eye accomodate when looking at close objects
the ciliary muscles contract, which slackens (loosens) the suspensory ligaments
the lens becomes fat
this increases the amount by which it refracts light
32
how does the eye accomodate when looking at distant objects
the ciliary muscles relax, which allows the suspensory ligaments to pull tight.
this makes the lens go thin
so it refracts light by a smaller amount
33
how does long sightedness occur , how can you correct it and what is the medical term for it
long sighted people are unable to focus on near objects
this occurs when the lens is the wrong shape and does't refract the lightenough or the eyeball is too short .
the images of near objects are brought into focus behind the retina
you can use glasses with a convex lens ( a lens which curves outwards ) to correct it , the lens refracts the light rays so they focus on the retina
the medical term is hyperopia
34
how does short sightedness occur , how can you correct it and what is the medical term for it
short sighted people are unable to focus on distant objects
this occurs when the lens is the wrong shape and refracts the light too much or the eyeball is too long.
the images of distant objects are brought into focus in front of the retina
you can use glasses with a concave lens (a lens which curves inwards) to correct it so that the light focuses on the retina .
the medical term is myopia
35
what are alternative treatments to wearing glasses and what are their disadvantages
contact lenses - contact lenses are thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing. they are popular because they are lightweight and almost invisible. they are also more convenient than glasses for activities like sports. the two main types of contact lenses are hard lenses and soft lenses . soft lenses are generally comfortable, but carry a higher risk of eye infections than hard lenses .
laser eye surgery - bad eyesight can sometimes be corrected with laser eye surgery . a laser can be used to vaporise tissue , changing the shape of the cornea ( and so how strongly it refracts light into the eye ) . slimming it down makes it less powerfull and can improve short sight . changing the shape so that it is more powerfull will improve long sight. the surgeon can precisely control howmuch tissue the laser takes off, completely correcting vision. however, there is a risk of complications suchas infection or the eye reacting in a way that makes vision worse than before.
replacement lens surgery - sometimes long sightedness may be more effectively treated by replacing the lens of the eye .
in replacement lens surgery , the natural lens of the eye is removed and an artificial lens, made of clear plastic is inserted in its place . as it involves work inside the eye, replacing a lens carries higher risks than laser eye surgey , including possible damage to the retina . which could lead to loss of sight
36
what is the optimum temperature for enzymes in the body
37 degrees celcius
37
what moniters and controls body temperature and how
Body temperature is monitored and controlled by the thermoregulatory centre in the brain. The thermoregulatory centre contains receptors sensitive to the temperature of the blood. The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre.
38
explain how body temperatures are kept constant
temperature receptors detect that core body temperature istoo high / low
the thermoregulatory centre acts as a coordination centre - it recieves infornmation from the temperature receptors and triggers the effectors automatically.
effectors e.g. sweat glands produce a response and counteract the change
39
what allows the body to have a more sensitive response to body temperature changes
some effectors work antagonistically - e.g. one effector heats and another cools - they work at the same time to achieve a very precise temperature
40
what response is produced by effectors when it is too hot.
sweat is produced by sweat glands and evaporates from the skin . this transfers energy to the environment.
the blood vessels supplying the skin dilate so more blood flows close to the surface of the skin . this is called vasodilation. this helps transfer energy from tbe skin to the environment.
41
what response is produced by effectors when its too cold
hairs stand up to trap an insulating layer of air.
no sweat i produced
blood vessels supplying skin capillaries constrict to close off the skins blood supplu .
this is called vasoconstruction
when your cold you shivertoo (your muscles contract automatically ) . this needs respiration which transfers some energy to warm the body
42
what are hormones and what do they do
chemical molecules released directly into the blood.
they are carried in the blood to other parts of the body , but only affect particular cells in particular organs calles target organs.
Control things in organs and cells that need constant adjustment
43
what is the endocrine system composed of
endocrine glands which are various glands that produce and secrete hormones
44
do hormones have long lasting or short lasting effects
relatively long lasting effects
45
what is the pituitary gland
produces many hormones that regulate body conditions.
it is sometimes refered to as the master gland as these hormones act on other glands ,directing them to release hormones that bring about change
located in the brain
46
what do ovaries do
produce oestrogen which is involved in the menstrual cycle
47
what do the testes do
produce testosterone which controls puberty and sperm production in males
48
what is the thyroid gland
located in the neck
produces thyroxine which is involved in regulatinf things like the rate of metabolism, heart rate and temperature
49
what is the adrenal gland
a gland that produces adrenaline which is used to prepare the body for a fight or flight response
located near the pancreas
50
what is the pancreas
a gland which produces insulin which is used to regulate the blood glucose level
51
compare nervous and hormonal responses
nervous :
very fast action
act for a short amount of time
act on a very precise area
hormones :
slower action
act for a long time
act in a ore general way
52
what types of food put glucose into the blood from the gut
carbohydrates
53
what removes glucose
normal metabolism of cells
vigorous exercise
54
what is done with excess glucose in the body
stored as glycogen in the liver and muscles
55
what oniters the level of glucose
the pancreas
56
explain what happens when blood glucose concentration is too high
1.blood with too much glucose
2. insulin is secreted by the pancreas
3. insuling and glucose move from blood into liver and muscle cells.
4. insulin makes liver turn glucose into glycogen
57
explain what happens when blood glucose concentration is too low
1. blood with too little glucose
2. glucagon secreted by pancreas
3. glucagon enters liver where it makes the liver turn glycogen into glucose
4. glucose is released into the blood by the liver
58
what is diabetes
a condition that affects your ability to control your blood sugar level
59
what is type 1 diabetes and what needs to be done to treat it
where the pancreas produces little or no insulin.
this means a persons blood glucose level can rise to a level that can kill them .
people with type one diabetes need insulin therapy
this involves inkections of insulin throughout the day mostly at mealtimes.
this meakes sure that glucose is removed from the blood quickly once the food has been digested.
it is a very effective treatment.
they also need to limit their carbohydrate intake and regularly exercise
60
what is type 2 diabetes ,what are the risk factors and how can it be controlled
where a person becomes resistant to their own insulin .
this can also cause a persons blood sugar levels to rise too high.
obesity is a major risk factor
can be controlled by eating a carbohydrate controlled diet and regularly exercising
61
what do the kidneys do
make urine by taking waste products out of your blood
substances are filtered out of the blood as it passes through the kidneys. this process is called filtration
62
what is selective reabsorption
when usefull substances like glucose ,some ions and the right amount of water are absorbed back into the blood from the kidneys .
63
what are three substances that are removed from the body in urine
urea
ions
water
64
what is urea /how is it formed
proteins cant be stored by the body - so any excess amino acids are converted into fats and carbohydrates, which can be stored.
this occurs in the liver and involve a process called deamination
ammonia is produced as a waste product from this process.
ammonia is toxic so its converted to urea in the liver. urea is then transported to the kidneys where it is filtered out of the blood and excreted from the body in urine
a small amount is lost from the skin in sweat
65
what is the issue with having too much ions and what is done about it
ions such as sodium are taken in the body in food then reabsorbed in the blood.
if the ion content is wrong, this could upset the balance between ions and water meaning too much or too little water is drawn into cells by osmosis. having wrong amount of water can fammage cells
some are lost in sweat
balance is maintained by kidneys .
the right amount is reabsorbed in the blood after filtration and the rest removed in urine
66
how do we loose water and how is it balanced
we lose water from the skin in sweat and from the lungs when breathing out.
we cant control how much we lose in these ways , so the amount of water is balanced by the amount we consume and the amount removed by the kidneys in urine .
67
what hormone controlls the concentration of urine and where is it released
anti diuretic hormone
ADH
released by the pituitary gland into the bloodstream
68
what controlls water content regulation
negative feedback
69
what is the brains role in water content regulation
moniters the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed
70
explain what happens when water content is too high or low
a receptor in the brain detects that the water content is too high/low
the coordination centre in the brain receives the infornmation and coordinates a response
the pituitary gland releases less/more ADH so more/less water is reabsorbed from the kidney tubules
71
what would happen if your kidneys didnt work properly
waste substances would build up in the blood an you lose your ability to control the levels of ions and water in your body. eventually, this results in death .
72
what two ways can people with kidney failure be kept alive
dialysis treatment
kidney transplant
73
how does dialysis treatment work
what are the advantages and disadvantages
has to be done regularly to keep concentrations of dissolved substances in blood at normal levels and remove waste substances.
in a dialysis machine, the persons blood flows between partially permeable membranes surrounded by dialysis fluid. it is permeable to ions and waste substances not others like proteins. the dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood .
this means that usefull dissolved ions and glucose wont be lost from blood.
only waste and ions and water diffuse across the barrier.
many patients have to have dialysis three times a week. each session takes 3-4 hours
may cause blood clots or infections
expensive for NHS
can buy a patient time until a donor organ is found
74
what are the conditions for a kidney transplant and what are the advantages and disadvantages
usually transplantedd from people who have dies suddenly
the person who died has to be on the organ donor register or carry a donor card.
kidneys can be transplanted from people who are still alive but there is a small risk to the person donating the kidney .
there is also a risk that the donor kidney can be rejected bu the patients immune system . the patient is treated with drugs to prevent this but it can still happen .
transplants are cheaper than dialysis and they can put an end to the hours patients have to spend on dialysis.
there are long waiting lists for kidneys.
75
what do sex hormones do during puberty
trigger secondary sexual characteristics such as development of facial hair, breasts, wider hips, broad shoulders
and cause eggs to mature in women
76
describe all the stages in the menstrual cycle
stage 1
day 1 - mentruation starts. the uterus lining break down for about four days.
stage 2
the uterus lining nuilds up again . from day 4 to day 14 into a thick spongy layer full of blood vessels. ready to receive a fertilised egg.
stage 3
an egg develops and is released from the ovary at day 14 - this is called ovulation
stage 4
the wall is then maintained for about 14 days until day 28 . if no fertilised egg has landed on the uterus wal by day 28 , the spongy lining starts to break down and the whole cycle starts again .
77
describe all the hormones involved in mentruation and what they do
FSH (follicle stimulating hormone )
produced in the pituitary gland
causes an egg to mature in one of the ovaries , in a structure called a follicle.
stimulates the ovaries to produce oestrogen
Oestrogen
produced in the ovaries
causes the lining of the uterus to grow
stimulated the release of LH which causes the release of an egg and inhibits release of FSH
LH luteinising hormone
produced by the pituitary gland.
stimulates the release of an egg at day 14 (ovulation )
progesterone
produced in the ovaries by the remains of the follicle after ovulation.
maintains the lining of the uterus during the second half of the cycle. when the level of progesterone falls, the lining breaks down .
inhibits the release of LH and FSH
78
how can oestrogen prevent the release of an egg
if oestrogen is taken every day to keep the leel of it permanently high. it inhibits the production of FSH and after a while, egg development and production stop and stay stopped.
79
how can progesterone reduce fertility
stimultes the production of thick mucus which prevents any sperm getting through and reaching an egg
80
what is the contraceptive pill and progesterone only pill
contraceptive pill
oral contraceptive containing oestrogen and progesterone .
it is over 99% effective at preventing pregnancy.
can cause side effects like headaches and nausea and it doesnt prevent against sexually transmitted diseases.
orogesterone only pill
has fewer side effects and is just as effective
81
describe all forms of contraception involving hormones
contraceptive patch -
contains oestrogen and progesterone . it is a small patch that is stuck to the skin. lasts one week
contraceptive implant 0
inserted under the skin of the arm . releases a continuous amount of progesterone which stops the ovaries releasing eggs. makes it hard for sperm to swim to the egg and stops any fertilised egg implanting in the uterus . an implant can last for three years.
the contraceptive injection -
also contains progesterone. each dose lasts 2 -3 months
intrauterine device IUD -
t shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertilised egg. there are two main types - plastic IUDs that release progesteron and copper IUDs that prevent the sperm surviving in the uterus .
82
what are the different barrier methods of controlling fertility
condoms -
prevent sexually transmitted disease
diaphragm
shalllow plastic cup that fits over the cervix to form a barrier.
has to be used with spermicide
spermicide
can be used alone but not as effective ( only about 70 -80% )
83
what are three other methods of avoiding pregnancy that are not hormonal or barrier methods
sterilisation
involves vutting or tying the fallopian tubes or the sperm duct .
this is a permanent procedure .
very small chance that the tubes can rejoin
natural methods -
finding out when mentrual cycle in woman is most fertile and avoid sexual intercourse on those days.
not effective
abstinence
not having intercourse
84
how can hormones increase fertility and what are the pros and cons
some women have levels of FSH that are too low to causetheir eggs to mature
the hormones FSH and LH can be given to women in a fertility drug to stimulate ovulation
pros
helps women get pregnant
cons
doesnt always work
expensive
too many eggs could be stimulated resulted in multiple pregnancies (twins, triplets etc ...)
85
what is IVF and what are its pros and cons
involves collecting eggs from the womans ovaries and fertilising them in a lab using the mans sperm .
IVF treatment can also involve a technique called Intra cytoplasmic sperm injectin ICSI , where the sperm is injected directly into the egg. it is usefull if the man has low sperm count
the fertilised eggs are then grown into embryos in a laboratory incubator.
once the embryos are tiny balls of calls. one or two of them are transferred to he womans uterus to iprove change of pregnancy.
FSH and LH are given before egg collection to stimulate several eggs to mature .
pros -
give an infertile couple a child
cons -
multiple births can happen if more than one embryo gows into a baby . risky for mother and babies.
the succes rate is low - average succes rate in the uk is around 26% / this makes the process stressful and upsetting.
some woman have strong reactions to the hormones - abdominal pain, vomiting , dehydration .
86
how have the techniques of IVF been improved
advances in microscope techniques.
specialised micro tools have been developed to use on the eggs and sperm under the microscope.
also used to remove single cells from the mbryo for genetic testing.
more recentrly, the development of the time lapse imaging means that the growth of the embryos can be continuosly monitered to help identify those that are more likely to result in a successful pregnancy .
87
why are some people against IVF
often results in unused embryos being destroyed.
people think it is unethical as it was a potential life.
the genetic testing of embryos before implantation raises ethical issues as some people thing it could lead to the selection of preffered characteristics
88
how does adrenaline prepare the body for fight or flight
by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles .
e.g. increase heart rate
89
what does thyroxine do and how is it controlled by negative feedback
plays an important role in the basal metabolic rate - the speed of chemical reactions when the body is at rest.
important for stimulatinf protein synthesis for growth and development
released in response to TSH hormone
a negative feedback system controls levels of thyroxine
when it is higher . the secretion of TSH from the pituitary gland is inhibited.
this reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal
90
what is auxin
a plant hormone that controls growth near the tips of shoots and roots
it controls the growth of a plant in respons to light (phototrophism ) and gracvity ( gravitropism or geotropism )
91
where is auxin produced and how does its distribution affect the plant
produced in the tips and moves backwards to stimulate the cell elongation process which occurs in the cells just behind the tips.
if the tip of a shoot is removed. no auxin is available and the shoot may stop growing.
extra auxin promotes growth in the shoot but inhibits growth in the roots
92
how do shoots grow towards light
when a shoot tip is exposed to light , more auxin accumulates on the side that is in the shade than the side that is in the light .
this makes cells grow faster on the shaded side so the shoots bend towards the light
93
hy do shoots grow away from gravity and roots grow towards gravity
when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tim , with more auxin on the lower side.
this causes the lower side to grow faster , bending the shoot upwards.
a root growing sideways will also have more auxin on its lower side .
but in a root, the extra auxin inhibits growth . this means the cells on top elongate daster and the root bends downwards
94
describe a practical whhere you would investigate plant growth responses
1. place cotton wool in 3 petri dishes and soak them with equal volumes of water
2. place ten crest seeds (or mustard seeds ) in each dish
3. leav the dishes in a warm place and allow to germinate
4. water every day with same volume of water.
5. make sure each dish has equal amount of germinated seed (seedlings )
6. measure the height of each seedling
7. place one dish in full sunlight , one in partial light , one in complete darkness
8. measure the height of each seedling every day for at least five days
9, calculate mean seedling height per day
10. dark ones are the longest, trying to grow rapidly to reach light , yellow leaves as they cant photosynthesise.
can also investigate effect of gravity
place a dish of seedlings on its side in the dark
the shoots should groq upwards
control variable s
number of seeds
type of seed
temperature
water
independant
light intensity
dependant
height of seedlings.
95
what are the uses of auxin
killing weeds -
most weeds growing in fields of crop are broad leaved
seletive weedkillers have been developed using auxins ,which only affect the broad leaved plants . they totally disrupt their normal growth patterns which soon kills them whilst leaving grass and crops untouched .
growing from cuttings with rooting powder - a cutting is part of a plant tht has been cut off it .like the end of a branch with a few leaves on it. normally if you stick cuttings in the soil they wont grow. if you add rooting powder which contains auxins, they will produce roots rapidly and start growing new plants. enable growers to produce clones of a really good plant very quickly .
growing cells in tissue culture -
tissue culture can be used to grow clones of a plant from a few of its cells. to do this. hormones such as auxins need to be added to the growth medium to stimulate the cells to divide to form both roots and shoots
96
what is gibberellin
a plant growth hormone
stimulates seed germination ,stem growth and flowering
97
what are the uses of gibberellin
controlling dormancy -
lots of seeds wont germinate untill they have been through certain conditions . this is cold dormancy. seeds can be treated with gibberellin to alter dormancy and make them germinate at times of year that they wouldnt normally . it also helps to make sure all the seeds in a batch germinate at the same time.
inducing flowering 0
some plants require certain conditions to flower such as longer days or low temperatures .if these plants are treated with gibberellin , they will flower without any change in their environment. gibberellin can also be used to grow bigger flowers.
growing larger fruit -
seedless varieties of fruit often do not grow as large as seeded fruit. however, if gibberellin is added, they will grow much larger than normnal types .
98
how is ethene produced and what does it do in plants
produced by aging parts of a plant .
it influences the growth of the plant by controlling cell division . it also stimulates enzymes that cause fruit to ripen .
99
how can ethene be used commercially
to speed up the ripening of fruits .
while on the plant or during transport
this means that fruit can be picked while it is still unripe and less easily damaged.
the gas is then added to the fruit on the way to the supermarket so that it will be perfect as it reaches the shelves.
100
how can ripening of fruit be delayed while it is in storage
by adding chemicals that block ethenes effect on the fruit or reduce the amount of ethene that the fruit can produce.
soe chemicals can be used that react with ethene to remove it from the air
