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GCSE Biology > Homeostasis and Response > Flashcards

Homeostasis and Response Flashcards

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1
Q

what is the basic principle of homeostasis?

A

the regulation of the conditions inside your body and cells to maintain a stable internal environment in response to changes in bother internal and external conditions

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2
Q

what are automatic control systems?

A

systems that regulate the internal environment, including both nervous and hormonal communication systems

there are systems which control your blood glucose levels, water levels and body temperature

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3
Q

what 3 main components work together on all automatic control systems?

A

receptors, coordination centers, effectors

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4
Q

what is negative feedback?

A

a mechanism used by automatic control systems used to keep your internal environment stable:
the mechanism works so that when the level of something gets too high or too low your body uses negative feedback to bring it back to normal

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5
Q

describe the process of negative feedback

A
  1. receptor detects a stimulus
  2. coordination center receives and processes the information, then organizes a response
  3. effector produces a response that counteracts the change and restores the optimum level
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6
Q

negative feedback is constantly happening, how so?

A

the effectors keep producing the response for as long as they are stimulated by the coordination center, this may cause the opposite problem, so the receptor will detect if the level becomes too different and negative feedback starts again

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7
Q

when talking technically what do we call changes in the environment?

A

stimuli

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8
Q

what is the CNS?

A

the central nervous system

in vertebrates ( animals with backbones)this consists of the brain and spinal cord only, in mammals the CNS is connected to the body by sensory neurones and motor neurones

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9
Q

what are sensory neurones?

A

neurones that carry information as electrical impulses from the receptors to the CNS

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10
Q

what are motor neurones?

A

the neurones that carry electrical impulses from the CNS to effectors

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11
Q

what are effectors?

A

all muscles and glands, that response to nervous impulses

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12
Q

what are receptors?

give 2 examples

A

cells that detect the stimuli, there are many different types of receptors such as taste receptros on the tounge and sound receptors in the ears

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13
Q

give an example of when the receptors form larger more complex organs?

A

the retina of the eye covered in light receptor cells

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14
Q

how do muscles respond as effectors?

A

they contract

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15
Q

how do glands respond as effectors?

A

they secrete hormones

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16
Q

describe the coordianted response for when a bird sees a cat it wants to run away from :D

A
  • the receptors in the birds eyes are stimulated
  • sensory neurones carry the information from the receptors from the receptors to the CNS
  • CNS decides the response
  • CNS sends info to the muscles in the birds wings (effectors) via the motor neurones
  • muscles contract and bird flies to safety
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17
Q

what is the 7 step pathway for a nervous behaviour response?

A

1) stimulus
2) receptor
3) sensory neurone
4) CNS
5) motor neurone
6) effectors
7) response

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18
Q

what is a synapse?

A

the connection betwween 2 neurones

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19
Q

how is the nerve signal transferred across a synapse?

A

chemicals diffuse across the gap, and then set off a new electrical signal to the next neurone

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20
Q

what are reflexes?

A

rapid, automtic responses to certain stimuli that don’t ivolve the conscious part of the brain - they can reduce the chances of being injuredg

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21
Q

give to examples of reflexes

A
  • if somone shines a bright light in your eyes your pupils automatically get smaller so that less light gets into the eye - stopping it from getting damaged
  • if you get a shock your body releases the hormone adrenaline automatically - it doesn’t wait for you to decide that your’e shocked
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22
Q

what is the passage of information in a reflex (from receptor to effector) known as?

A

a reflex arc

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23
Q

neurones in reflex arcs go through where?

A

spinal cord or unconscious part of the brain

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24
Q

what neurone carries the impulses from the receptors

A

sensory

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25
Q

what neurones are in the CNS?

A

relay

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26
Q

what are relay neurones?

A

neurones that connect the snsory neurones to the motor neurones

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27
Q

descrbe the relfex arc for when a bee stings your fingure

A
  • bee stings fingure causing stimulation of pain receptor, so an impluse travels along the sensory enurone, the impulse them is passed along a relay neurone (in CNS) via a synapse, impulses then travel along a motor neurone via a synapse and finally the impulses reach the muscle, it contracts
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28
Q

what is our brain made up out of?

A

billions of interconnected neurones

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29
Q

define the function of our brain

A

it controls and coordianted everything tahat we do, even the most complex of behavious

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30
Q

what is the purpose of our cerebal cortex?

A
  • outer wrinkly part

- responsible for things like consciousness, intelligence, memory and language

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31
Q

what is the purpose of the medulla?

A
  • controls unconsciousness activities such as breathing and heartbeat
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32
Q

what is our cerebellum responsible for?

A

muscle coordination

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33
Q

how does studying patients with brain damage improve our scientific understanding of the brain?

A

if a small part of the brain has been damaged the effect this has on the patient can tell you lots about what the damaged part of the brain does

(eg if a person went blind with a stroke and the back parto of their bain was damaged that means the back part has something to do with vision)

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34
Q

describe the electrical stimulation of the brain

A

the brain can be electrically stimulated by pushing a tiny electrode into the tissue and giving it a small zap of electricity, by observing hwat stimulating different parts of the brain does, its possible to get an idea of what it does

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35
Q

What are MRI scans?

A

a magnetic resonance imaging scanner is a tube like machiene that can produce a very detailed picture of the brains structures.

scientitss 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

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36
Q

what are the positives of studying the brain ?

A
  • ## the research has led to the development of treatments for disorders of the nervous system, for example electrical stimulation can help reduce muscle tremors caused by nervous system disorders such as parkinsons disease
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37
Q

what are the negatives of the studying the brain?

A

it is incredibly complex and delicate - the investigationof brain function or development of treatments is very difficult.

it also carries risk of physical brain damage or increased problems with brain function

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38
Q

what is the scelerea?

A

the tough, supporting wall of the eye

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39
Q

what is the cornea?

A

the transparent outer layer found at the front of the eye

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40
Q

what is the iris?

A

the part of the eye that contains muscles whoch allow it to control the diameter of the pupil ( hole in the middle) and therfore how much light enters the eye

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41
Q

what is the lens?

A

the lens focuses the light onto the retina ( ehich contins receptor cells sensitive to light intensity and colour)

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42
Q

what is the shape of the lens controlled by?

A

the cicilary muscless and suspensory ligaments

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43
Q

what is the iris reflex for?

A

adjusting for bright light which can damage your eyes

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44
Q

what happens in the eye when light receptors detect a very bright light?

A

a reflex is triggered that makes the pupil smaller:
- circular muscles in the iris contract
- radial muscles relax
reducing the amount of light that can enter the eye

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45
Q

what happens when the light receptors in your eye detect dim light?

A

reflex is triggered that makes pupil wider:

  • circular muscles relax
  • radial muscles contract
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46
Q

what is accomodation?

A

when the eye focusses light on the retina by changing the shape of the lens

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47
Q

what happens so that your eye can look at near objects?

A

1) the cicilary muscles contract, which slakens (relaxes) the suspensory ligaments
2) the lens becomes fat (more curved)
this increases the amount by which it refracts light

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48
Q

what happens in your eye so that you can look at distant objects?

A

1) ciliary muscles relax allowing the suspensory ligaments to pull tight
2) this makes the lens go thin (less curved)
so it refracts light by a smaller amount

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49
Q

what does it mean if somone is long sighted?

A

they are unable to focus on near objects

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50
Q

why are ppl long sighted?

A

because their lens is the wrong shapee so dosent refract the light enough, or the eyeball is to short
so the images are brought into focus behind the retina

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51
Q

what treatment is used for long sighted ppl?

A

convex lenses - a lense which surved outwards, and refracts the light rays so they focus on the retina

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52
Q

what is the medical term for someone who is long sighted?

A

hyperopia

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53
Q

what does it mean if somone is short sighted?

A

they are unable to focus on distant objects

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54
Q

why are people short sighted?

A

because their lens is the wromg shape, and so refracts the light too much, or their eyeball is too long
the images of distant objets are brought into focus in dront of the retina

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55
Q

what treatment is avaliable for somoen who is short-sighted?

A

concave lenses - lenses which curve inwards, so that the light rays focus on the retina

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56
Q

what is the medical term for short sightedness?

A

myopia

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57
Q

what are contact lenses?

A

thin lenses that sit on the surface of the eue and are shaped to compensate for the fault in focusing

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58
Q

why are contact lenses popular?

A

lightweight, almost invisible, and more convenient for activites like sports

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59
Q

what are the 2 main types of contact lenses?

A

hard lenses and soft lenses

soft lenses more cofortable but carry a higher risk of infection

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60
Q

describe laser eye surgery

A

a laser can be used to vapourise tissue, changing the shape of the cornea, and so changing how strongly it refracts light into the eye
slimming it down - makes it less powerful so can improve short sight
changing shape so more powerful - can improve long sight
surgeon can precisely control how much tissue the laser takes off, completely correctingt the vision

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61
Q

negatives of laser eye surgery?

A

risk of complications like infections or the ye reacting in a way that makes your vision worse than before

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62
Q

what is replacement lens surgery?

A

sometimes short sightedness is treated better through replacing the lens of the eye rather than altering the shape of the cornea through laser surgery

in replacement lens surgery the natural lens of the eye is removed and an arifical elns made from clear oalstic is inserted into its place

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63
Q

what and why are the risk of replacemnt lens surgery?

A

invasive procedure, so its higher risk - possible damage to retina, could possibly lead to loss of sight

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64
Q

what has the body to balance to keep the body core tempereature constant?

A

energy gained and energy lost

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65
Q

what is the thermoregulatory centre?

A

the part of the brain which contains recpetors that are sensitive to the temperaure of blood flowing through the brain, also it recieves impulses from temperaure recptors in the skins giving info about skin temperature

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66
Q

what happens if your body temp is too high/too low ?

A
  • temperature receptors detect that core body temperaure is too high/too low
  • thermoregulatory centre acts as a coordination centre - recieves infor from the temp receptors and triggers the effectors automatically
  • effectors (eg sweat glands) produce a response and counteract the change
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67
Q

what does it mean if efffectors work anatgonistically?

A

eg one effector heats and one effectors cools - they work at the same time to achieve a very precise temperature, allowing a more sensitive response

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68
Q

what responses are produced by your effectors if you are too hot?

A
  • sweat produced by sweat glands and evapourates from skin, this transfers energy to the environment
  • vasodilation: blood vessels supplying the skin dialte so more blood flows close to the surface of the skin, so energy can be trasferred to the environment
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69
Q

what responses are produced by your effectors if you are too cold?

A
  • hairs stand up to trap an insulating layer of air
  • no sweat is produced
  • vascoconstriction: blood vessels supplying skin cappillaries constrict to close fo the skins blood supply
  • when your are cold you shiver, this needs respiration which transfers some energy to warm your body
70
Q

what are hormones?

A

chemical molecules released direcctly into the blood, carried by the blood, but only effect particular cells in particular organs (target organs)

hormoenes control things that eed constant adjutsment

71
Q

hormones ar made and secreted from glands.. which make up……

A

the endocrine systme

72
Q

endocrine sytem:

the pituatry gland

A
  • produces many hormones to regulate body conditions
73
Q

endocrine sytem:

thyroid

A
  • produces thyroxine which is invlovedin metabolic rate, heart pressure, heart rate etc
74
Q

endocrine sytem: the pancreas

A
  • produces insulin which is used to regulate blood glucose level
75
Q

endocrine sytem: ovaries (f only)

A

produces oestrogen which is invloved in the menstrual cycle

76
Q

endocrine sytem: testes

A
  • produceed progesterone condrols pubery and future potential reproduction.
77
Q

nerves v hormone

A
  • nerves are faster, act for a very short time on a very precise area
  • hormones are slower to take action, but act for a longer time and act in a more general way
78
Q

endocrine system: adrenal gland

A
  • produces adrenaline, used to prepare body for ‘fight or flight’ response
79
Q

why are really quick responses probably a nervous response?

A

because some information needs to be passed to the effectors really quickly ( eg pain signals) so it’s no good using hormones to carry the mesage - they are too slow

80
Q

what does eating foods carbohydrates do?

A

it puts glucose into the blood from the gut

81
Q

what process removes glucose from the blood?

A

normal metabolism

82
Q

what does vigorous exercise to in terms of blood glucose?

A

removes much more glucose from the blood

83
Q

how is excess is glucose stored?

A

as glycogen in the liver and in the muscles

84
Q

the level of glucose in the blood must be kept steady, how are changes monitored and controlled?

A

it’s monitored by the pancreas using the hormones insulin and glucagon in a negative feedback cycle

85
Q

describe the negative feedback cycle for if the blood glucose level is too high :)

A

So if there is blood with too much glucose, insulin is secreted by the pancreas, so now there is still too much glucose but there is also insulin in the bood. The insluin allows the glucose move into the liver and muscle cells, and therfore reduces the blood glucose levels.

86
Q

describe the the negative feedback cycle for is the blood glucose level is too low ;)

A

So if ther is blood with not enough glucose, glucagon is secreted by the pancreas, so while there is still not enough glucose ther is now glucagon.
The glucagon allows the glucose to be released into the blood by the liver - causing the blood glucose level to increase.

87
Q

what is type 1 diabetes?

A

where the pancreas produces little, or no insculin meaning a persons blood glucose can rise to a level that could kill them.

88
Q

what kind of treatment do people with type 1 diabetes need? what may this involve?

A

insulin therapy - this usually involves several injections of insulin throughout the day, most likely at mealtimes making sure that the glucose is removed from the blood quickly once the food has been digested, stopping the level getting too high

89
Q

how effective is inslulin therapy?

A

very effective

90
Q

the amount of insluin injected during inslulin therapy depends on what?

A

the persons diet, and how active they are

91
Q

how do people with type 1 diabetes need to adapt their lifestyle?

A
  • they should limit their intake of food rich in simple carbohydrates ( eg sugars) bwcause they can cause the blood sugars to rise rapidly
  • they should regularly exercise to help remove excess glucose from the blood
92
Q

what is type 2 diabetes?

A

when a person becomes resistant to their own insulin, so they still produce insulin but their body’s cells don’t respond properly to the hormone - this can cause their blood sugar to rise to dangerously high levels

93
Q

what puts you at higher risk for developing type 2 diabetes?

A

being overweight

obesity is a major risk factor in the development of disease

94
Q

how is type 2 diabetes controlled?

A

through eating a carbohydrat-controlled diet and getting regular exercise

95
Q

how do the kidneys make urine?

A

by filtering waste products and other unwanted substances out of your blood

96
Q

what is selective reabsorption?

A

the process that happens after filtration ( the filtering of substances out of the blood) - its when useful substances are absorbede back into the blood

97
Q

what substances are reabsorped back into the blood in selective reabsorption?

A

glucose, some ions and the right amount of water

98
Q

what substances are removed from the body in the urine?

A

urea, ions, and water

99
Q

what is the process of demination?

A

the conversion of proteins ( and the amino acids they are broken down into) into fats and carbohydrates, for storage

100
Q

where does deamination happen?

A

the liver

101
Q

why does deamination need to happen?

A

because proteins cannot be stored by the body

102
Q

what is produced during deamination? what happens with this product?

A

ammonia is produced - it’s toxic, so it’s converted to urea in the liver, and then the urea is transported to the kidneys where its filtered out of the blood and excreted form the body

103
Q

what could happen if the ion (or water) content of the body is wrong?

A

it could upset the balance between ions and water, meaning too much water or too little water is drawn into cells by osmosis - having the wrong amount of water can damage cells or mean they don’t work as well as normal

104
Q

how can we lose water?

A

from the skin in sweat or from the lungs when breathing out

105
Q

with which hormone is the concentration of urine controlled? from where is in released? into what?

A

through the anti-diuretic hormone (ADH) which is released into the bloodstream via th pituitary gland

106
Q

what is the brains involvement in controlling the concentration of urine?

A

it monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed

107
Q

the process of water concentration regulation is controlled by what kind of system?

A

negative feedback - so if the water content gets too high or too low a mechanism will be triggered that brings it back to normal

108
Q

what happens if the kidneys do not wok properly?

A

waste substances build up in the blood and you loose your ability to control the levels of ions and water in your body, which eventually results in death.

109
Q

how can people with kidney failure be kept alive?

A

through kidney dialysis treatment or through having a kidney transplant

110
Q

why does kidney dialysis have to be done regularly?

A

to keep the concentrations of dissolved substances in the blood at normal levels, and to remove waste substances

111
Q

what happens in a kidney dialysis machine?

A

the persons blood flows between partially permeable membranes surrounded by dialysis fluid , its permeable to things like ions and waste substances, but not big molecules like proteins just like the membranes in the kidneys

112
Q

what is the dialysis fluid like?

A

it has the same conc of dissolved ions and glucose as healthy blood, meaning that useful dissolved ions and glucose won’t be lost from the blood during dialysis, only waste substances ( such as urea) and excess ions and water diffuse across the barrier

113
Q

how often do people with kidney failure have to undergo dialysis? ( frequency & duration )

A

3x a week for 3-4 hours

114
Q

where do the healthy kidneys used in transplants come from?

A

either:

  • someone who has died suddenly, and is on the donor register or carries a donor card
    or
  • from someone who is still alive ( we have 2 kidneys)
115
Q

what are the risks of kidney transplants?

A
  • the new kidney may be rejected by the patients immune system, even through patients are treated with drugs against this, it cans till happen.
  • there is a risk to the person donating the kidney
  • very long waiting lists
116
Q

what is the advantages of a kidney transplant over constant dialysis?

A

transplants are cheaper in the long run, and can give the patient better quality of life

117
Q

what is the main reproductive hormone in men? where is it produced? what does it do?

A
  • testosterone
  • the testes
  • stimulates sperm production
118
Q

what is the main reproductive hormone in women? where is it produced? what does it do?

A
  • oestrogen
  • the ovaries
  • brings physical changes and is involved in the menstrual cycle
119
Q

what are the 4 stages of the menstrual cycle?

A
  1. day 1: menstruation the uterus lining breaks down for about four days
  2. the uterus lining builds up again, from, day 4 to 14, into a thick spongy layer full of blood vessels ready to receive a fertilised egg
  3. an egg is released from the ovary at day 14 - this is called ovulation
  4. the wall is them maintained for about 14 days until day 28. If no fertilised egg has landed on the uterus wall by day 28 the spongy lining starts to break down and the whole cycle starts again
120
Q

what is FSH?

A

the 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

121
Q

what is oestrogen?

A

a hormone produced in the ovaries
causes the lining of the uterus to grow

simulates the release of LH
inhibits the release of FSH

122
Q

what is LH?

A

the luteinising hormone
produced by the pituitary gland
stimulates the release of an egg at day 14

123
Q

what is progesterone?

A

a hormone produced in the ovaries by the remains of a follicle after ovulation
maintains the lining of the uterus during the second half of the cycle, so when progesterone falls the lining breaks down
inhibits the release of LH and FSH

124
Q

how can oestrogen be used as a method of contraception?

A

if oestrogen is taken every day to keep the level of it permanently high it inhibits the production of FSH, and after a while egg development and production stop and stay stopped

125
Q

how can be progesterone be used in contraception?

A

progesterone reduces fertility by stimulating the production of thick mucus which prevents any sperm getting through and reaching the egg

126
Q

what is the pill? how effective? any side effects?

A

it’s an oral contraceptive containing oestrogen and progesterone
over 99% effective at preventing pregnancy
can cause side effects such as headaches and nausea
doesn’t protect against STDs

127
Q

what kind of pill has the least amount of side effects?

A

the progesterone only pill

128
Q

what is a contraceptive patch?

A

a patch that contains oestrogen and progesterone, its small that is stuck to the skin and lasts for one week

129
Q

what is the contraceptive implant?

A

its inserted under the skin releasing a continuous amount of progesterone which stops the ovaries releasing eggs, making it harder for the sperm to swim to the egg and stops any fertilised egg implanting in the uterus, an implant can last for 3 months

130
Q

what is a contraceptive injection?

A

an injection that contains progesterone, each dose lasting 2 to 3 months

131
Q

what is a intrauterine device? (IUD)

A

a t-shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertilised egg.

132
Q

what are the 2 types of IUDs?

A

plastic IUDs - releases progesterone

copper - prevents the sperm surviving in the uterus

133
Q

what are some non-hormonal forms of contraception?

A
  • condoms (stops the sperm entering )

- diaphragm (fits over the cervix as a barrier, must be used with a spermicide)

134
Q

what is sterilisation?

A

a permanent procedure that involves cutting or tying the fallopian tubes, which connect the ovaries to the uterus)in a female, or the sperm duct in a male

135
Q

how may pregnancy be avoided naturally?

A

through finding out when the women is most fertile and avoiding sexual intercourse those days

136
Q

why may a women be infertile?

A

her levels of FSH may be too low to cause her eggs to mature, meaning that no eggs are released and therfore the women cannot get pregnant

137
Q

what can a women be given who is infertile?

A

a fertility drug that contains FSH and LH to stimulate ovulation

138
Q

what are the pros and cons of a fertility drug?

A

pros - it helps women become pregnant, when they previously couldn’t
cons - doesn’t always work, some women may have to use it many times which could be expensive, too many eggs could be stimulated resulting in unexpected multiple pregnancies

139
Q

what does IVF involve?

A

collecting eggs from the womans ovaries and fertilisng them in a lab using the mans sperm

140
Q

what is the technique use in IVF where the sperm is injected directly in the egg? why is this a good technique?

A

Intra-cytoplasmic Sperm Injection (ICSI)

141
Q

describe the steps of IVF…

A
  1. collection of eggs and sperm
  2. ICSI
  3. fertilised eggs grown into embryos in a labratory incubator
  4. once the embryos are tiny balls of cells one or two are then transferred to the womans uterus to improve chance of pregnancy
    ( FSH and LH are given before egg collection to stimulate several eggs to mature so more than one egg can be collected )
142
Q

what are the cons of ivf?

A
  • multiple births can happen if more than one embryo grows into a baby, increasing the risk of miscarriage, stillbirth etc
  • very low success rate (26%), so the process can be stressful and often upsetting, especially if it ends in multiple failures
  • can be physically stressful for the women, they may have strong reaction to the hormones
143
Q

what physical symptoms may a woman have in reaction to the hormones perscribed for IVF?

A

abdominal pain, vomiting, dehydration

144
Q

how have advances in microscopic techniques improved the success rate of IVF?

A
  • special micro-tools have been developed to use on the eggs and sperm under the microscope, and can also be used to remove single cells from the embryo for genetic testing
  • time lapsing imaging (using a microscope and camera built into the incubator) means embryos can be continuously monitored to help identify those that are more likely to result in a successful
145
Q

why are some people against IVF?

A
  • it often results in unused embryos that are eventually destroyed, and some people think it is unethical because each embryo has the potential for rhuman life
  • genetic testing before implantation raises ethical issues as it could lead to the selection of preferred characteristics
146
Q

where is adrenaline released from?

A

the adrenal glands just above the kidneys

147
Q

why is adrenaline released?

A

it’s released in response to stressful or scary situations - your brain detects fear or stress and sends nervous impulses to the adrenal glands, which respond by secreting adrenaline

148
Q

what mechanism does our bodies use to control the levels of hormones in our blood?

A

negative feedback

149
Q

where is thyroxine released from?

A

the thyroid gland in the neck

150
Q

what is the role of thyroxine?

A

it regulates the basal metabolic rate, which is the speed at which chemical reactions in the body occur while the body is it at rest, its used to stimulate protein synthesis, growth and development

151
Q

thyroxine is released in response to what hormone? where is this hormone released from?

A

thyroid stimulating hormone - pituitary gland

152
Q

describe how a negative feedback system helps keep the amount of thyroxine in the blood at the right level?

A

when the level of thyroxine in the blood is higher than normal, 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

153
Q

what is auxin?

A

a plant hormone that controls growth near the tips and shoots and roots

154
Q

what does phototropism and geotropism? give an example of a plant hormones that works with these 2 principles?

A

eg auxin
phototropism - controls growth of plant in response to light
geotropism ( or gravitropism) - controls growth of plant in response to gravity

155
Q

explain: how is auxin produced?

A

in the tips and moved backwards to stimulate the cell elongation process which occurs in the cells just behind the tips

156
Q

why may a shoot stop growing if the tip is removed?

A

no auxin is avaliable

157
Q

how does extra auxin effect a plant?

A

promotes growth in the shoot, but inhibits growth in the root

158
Q

why do shoots grow towards light?

A

because when a shoot tip is exposed to ligh 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 shade side, so the shoots bend towards the light

159
Q

why does a shoot grow away from gravity?

A

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 lower side to grow faster, bending the shoot upwards

160
Q

why does a root grow towards gravity?

A

a root growing sideways will have more auxin on it’s lower side, due to gravity, in a root the extra auxin inhibits growth - this means the cells on top elongates faster and the root bends downwards

161
Q

how can auxins be used to control plant growtg?

A

killing weeds, growing from cuttings with rooting powder or growing cells in tissue culture

162
Q

how can be auxins used for weed killers?

A

most weeds in crops, fields or lawns are broad-leaved, where as the grasses and crops have very narrow leaves

selective weedkillers have been developed using auxins, which only effect broad-leaved plant, through disrupting their normal growth patterns

the crops and grasses are left untouched

163
Q

how can auxin rooting powder be used to produce lots of clones of a very god part of the plant very quickly?

A

through mixing the rooting powder with the cutting of the plant

164
Q

how can cells be grown in tissue cultures?

A

hormones such as auxins need to be added to the growth medium along with nutrients to stimulate the cells to divide to form both roots and shoots

165
Q

what is gibberellin?

A

another type of plant growth hormone that stiimulates seed germination, stem growth and flowering

166
Q

how can gibberellin be used to control dormancy?

what is dormacy ?

A

dormacy - the certain conditions in which seeds woll germinate

seeds can be treated with gibberellin to alter dormacy and make them all germinate at times of year that they wouldn’t normally ( so all seeds in the batch can germinate at the same time )

167
Q

what hormone can be used to induce flowering, despite the normal required conditions not be present?

A

gibberellin

168
Q

what hormone can be used to make seedless fruit grow as big as seeded fruit?

A

Gibberellin

169
Q

what is ethene?

A

A gas produced by aging parts of a plant that influences the growth of the plant by controlling cell division and stimulating the enzymes which cause fruit to ripen

170
Q

how can ethene be used comercially?

A

to speed up the ripening offruits, so that the fruit can be picked while its still unripe ( firmer and less easily damaged) the gas is then added to the fruit on the way to the shops so it will be perfect by the time it’s put pnto the shelves

171
Q

how can ripening be delayed when fruit is in storage?

A

by the addition of chemicals that block ethenes effect on the fruit or reduce the amount of ethene that the fruit produce, or some chemicals cane be used that react with ethene to remove it from the air :D

GCSE Biology (8 decks)

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