homeostasis and response (T5) Flashcards
1
Q
define homeostasis
A
the regulation of the internal conditions of a cell or organism to maintain the optimum conditions for function, in response to internal and external changes
2
Q
why do we need to control internal conditions
A
enzymes:
- enzymes only work at their best in specific conditions (opt. temp and pH)
- enzymes control all the functions of a cell
- the functioning of a cell is vital for the tissues, organisms and organs to work
3
Q
what internal conditions need to be controlled?
A
- body temp
- water content
- blood glucose conc
4
Q
how are the internal conditions controlled
A
detecting changes and responding to them involves automatic control systems including the nervous system and the hormonal system (endocrine system)
5
Q
what detects changes (stimuli)
A
receptor cells
6
Q
what decides what needs to be done (processes information)
A
coordination centre - brain/spinal cord
7
Q
what makes the response happen
A
effectors - muscles/organs
8
Q
where are receptor cells found
A
in sense organ
9
Q
what are the senses and sense organs
A
- touch - skin
- smell - nose
- sight - eyes
- taste - tongue
- sound - ears
10
Q
what are the two communication systems + diff in response?
A
- nervous system - produces fast, short-lasting response
- hormonal system - produces slow long-lasting response
11
Q
what is the nervous system responsible for
A
coordinating responses to changes in the environment
12
Q
what are the two diff parts of the nervous system
A
- central nervous system (CNS)
brain and spinal cord - peripheral nervous system (PNS)
nerves taking info to and from CNS
13
Q
how do we respond to stimuli
A
- stimuli
- receptors in sense organs
- sensory neurones (nerves)
- CNS - coordinator - spinal cord and brain
- motor neurones (nerves)
- effectors (muscles)
- response
14
Q
how are nerve cells adapted to their function
A
nucleus:
- controls cell activities
nerve fibre/axon:
- long thin extension of cytoplasm that carries the nerve impulse
branched endings:
- parts that connect with the effector or other neurones
insulating sheath (myelin):
- layer to insulate the neurone and increase the speed of the impulses
15
Q
what is a reflex action/arc
A
automatic and rapid response to a stimulus - does not involve conscious part of brain
e.g. constricting/dilating pupil based on light levels
16
Q
how does a reflex work
A
- stimulus detected by a receptor cell
- nerve impulses carried along a sensory neurone
- then passed and carried through a relay neurone in the spinal cord
- impulse sent along a motor neurone to an effector
- effector carries out response
17
Q
what are synapses
A
gaps in between neurones
18
Q
how do synapses works
A
when impulse reaches end of one neurone it causes a chemical called a neurotransmitter to be released. this neurotransmitter diffuses across the gap and binds to receptor sites on the next neurone which generates a new electrical impulse in the next neurone
19
Q
what is the brain
A
organ that controls complex behaviour, made of billions of inter connected neurones, diff regions carry out diff functions
20
Q
what is the function of the cerebal cortex
A
concerned w/ consciousness, intelligence, memory and language
21
Q
what is the function of the cerebellum
A
coordinating muscular activity and balance
22
Q
what is the function of the medulla
A
concerned w/ unconscious activities e.g. breathing, control of the heartbeat, movement of the gut
23
Q
how have scientists been able to map out different regions of the brain
A
by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques
24
Q
why is treating brain injuries very difficult
A
the brain is a very complex and delicate organ so it is easy to cause extra damge.
25
what is the eye
a sense organ containing receptors sensitive to light intensity and colour
26
what is the function of the ciliary muscle
changes the shape of the lens for focusing
27
what is the function of the lens
changes shape slightly to adjust the focusing of light onto the retina
28
what is the function of the pupil
light enters your eye through this hole
29
what is the function of the iris
controls the amount of light entering your eye
30
what is the function of the cornea
transparent part at the front of your eye, does most of the bending of the light rays
31
what is the function of the sclera
tough, white protective layer
32
what is the function of the optic nerve
carries nerve impulses to brain
33
what is the function of the suspensory ligaments
holds the lens in place and helps w focusing
34
what is the function of the retina
inner light-sensitive layer, contains rod cells that work in dim light and cone cells that detect colour and detail
35
what is the blind spot
the point where the optic nerve leaves the eye has no retina so there are no rod or cone cells there. this causes a blind spot, however you are unaware of this as the brain fills the gap.
36
what is accommodation
process of changing the shape of the lens to
focus on near or distant objects.
37
how does the lens change shape to focus on distant objects
* the ciliary muscles relax
* the suspensory ligaments are pulled tight
* the lens is made less convex (flatter and thinner) and only slightly refracts light rays.
38
how does the lens change shape to focus on nearby objects
* the ciliary muscles contract
* the suspensory ligaments loosen
* the lens is made more convex (rounder and thicker) and refracts light rays strongly.
39
how does the pupil change in dim light
- radial muscles contract
- causes your pupil to dilate (expand) which lets more light into your eye
40
how does the pupil change in bright light
- circular muscles contract
- causes your pupil to constrict (get smaller) which lets less light into your eye
41
what are the two common eye defects
- myopia (short-sightedness)
- hyperopia (long-sightedness
42
what ab the image on the retina
formed upside down but our brains interpret the image as the right way up
43
how does myopia affect sight
- can clearly see objects when they are near but objects further away appear blurred
- eyeball is too long or lens is too curved so light rays focus just in front of the retina
44
common treatments for myopia
- glasses w/ a concave lens
- spreads out the light from distant objects before it reaches the eye. this means the thicker lens can bring the rays into perfect focus on the retina
45
how does hyperopia affect sight
- can focus clearly on distant objects but close objects appear blurred
- eyeball is too short or lens is too flat so light rays focus just behind the retina
46
common treatments for hyperopia
- glasses w/ a convex lens
- bring light rays from closer objects closer together before it reaches the eye. this means the thinner lens can bring the rays into perfect focus on the retina
47
what defect can contact lenses treat
myopia and hyperopia
48
how do contact lenses work
- lens placed on the surface of the eye that refracts light to focus it on the retina
49
what are the advantages of contact lenses
- cannot be seen
- makes life easier for playing sports + general activities
- soft lenses are comfortable to wear
50
what are the disadvantages of contact lenses
- have to be removed overnight
- risk of eye infection
- soft lenses do not last long
51
what defects can laser eye surgery treat
myopia and hyperopia
52
how does laser eye surgery work
lasers are used to reduce (myopia) or increase (hyperopia) the thickness of the lens to focus light onto the retina
53
what are the advantages of laser eye surgery
- permanent change
54
what are the disadvantages of laser eye surgery
- only available once eyes have stopped growing so not accessible for everyone
- can be expensive
55
what defects can replacement lenses treat
myopia and hyperopia
56
how do replacement lenses work
add another lens inside the eye itself to correct the visual defect permanently
- two techniques: natural lens left in place or the faulty lens is replaced
57
what are the advantages of replacement lenses
- permanent change
58
what are the disadvantages of replacement lenses
- risk of cataracts
- risk of infections
- can be expensive
59
where is body temp monitored and controlled
the thermoregulatory centre in the brain
60
how are changes in body temp detected
- thermoregulatory centre contains receptors sensitive to temp of blood
- skin has temp receptors that send nerve impulses to the thermoregulatory centre
61
what happens if body temp is too high
- blood vessels dilate (vasodilation)
- sweat produced
- both these mechanisms cause a transfer of energy from the skin to the environment
62
what happens if body temp is too low
- shivering > muscles contract - more respiration - exothermic - increases temp
- blood vessels constrict (vasoconstriction)
- sweating stops
- going pale - less blood closer to surface so heat can't escape
63
what are hormones
- chemicals in our body that control responses or changes that are longer-lasting
- blood carries the hormone from where they're made to the target organ
64
what is the endocrine system
system composed of glands which secrete hormones directly into the bloodstream
65
what does adrenaline do
speeds up the heartbeat and breathing rate
66
where is adrenaline made
adrenal glands (on top of kidneys)
67
what does insulin do
controls blood glucose conc
68
where is insulin made
pancreas
69
what do growth hormones do
control chemical reactions in body and effects growth
70
where are growth hormones made
thyroid
71
what does progesterone do
causes the body changes in puberty in females and menstrual cycle
72
where is progesterone made
ovaries
73
what does testosterone do
causes the body changes at puberty in males
74
where is testosterone made
testes
75
what is the role of the pituitary gland
makes hormones that control the other glands
76
what is negative feedback
A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback.
77
what is thyroxine
- hormone produced by thyroid gland in neck
- controls basal metabolic rate of body
- important role in growth and development
- stimulates synthesis of proteins
- normal levels important in developing babies for brain development
78
describe the negative feedback mechanism for regulating thyroxine production
- hypothalamus detects low thyroxine levels
- hypothalamus releases TRH
- pituitary gland releases TSH
- thyroid gland releases more thyroxine
- thyroxine levels return to normal
- hypothalamus detects normal thyroxine levels
- normal thyroxine levels inhibits TRH release by hypothalamus
- inhibition of TRH means pituitary gland stops producing TSH
79
what is adrenaline
- hormone produced by adrenal glands when stressed, angry, excited or frightened so body ready for action
80
what does adrenaline cause and how does it help
* heart rate and breathing rate to increase
- glucose and oxygen in blood moves faster so more respiration takes place and more energy is released
* stored glycogen in liver to be converted to glucose for respiration
- more available for respiration so more energy released
* pupils of your eyes to dilate to let in more light
- can see better
* mental awareness increases
- reflexes more accurate and can think more clearly
* boosts delivery of glucose and oxygen to brain and muscles to prepare body for fight or flight
- more available for respiration
81
why do we need to control blood glucose conc
glucose is needed for respiration
82
what will effect blood glucose levels
- after meals blood sugar will be high, before meals + after exercise blood sugar is likely to be low
83
what happens if blood glucose conc is too low
- not enough for respiration so cells can shut down
84
what happens if blood glucose conc is too high
- affects osmosis so cells lose too much water which can lead to a coma
85
what hormones control blood sugar and where are they produced
- insulin and glucagon produced in the pranceas
86
how does insulin control blood sugar
reduces blood sugar if its too high
87
how does glucagon control blood sugar
increases it if blood sugar is too low
88
what is the regulation of blood sugar an example of
a negative feedback mechanism
89
describe the negative feedback mechanism for controlling blood glucose levels
IF BLOOD GLUCOSE IS TOO HIGH:
- pancreas releases insulin
- insulin increases the amount of glucose taken in by cells
- it also converts glucose into glycogen in the liver
- blood glucose falls
- blood glucose returns to a normal level
IF BLOOD GLUCOSE IS TOO LOW:
- glucagon is released
- glucagon breaks down glycogen into glucose
- it also breaks down amino acids/fats (into glucose)
- blood glucose rises
- blood glucose returns to a normal level
90
what is type 1 diabetes
a disorder in which the pancreas fails to produce sufficient insulin
91
what are the causes/risk factors for type 1 diabetes
- could be a genetic link
- damaged pancreas
92
what are the short term symptoms of type 1 diabetes
- producing lots of urine
- tired
- thirsty
93
what are the long term effects of type 1 diabetes
(if untreated):
- severe weight loss
- wasting away
- eventually death
94
current treatments for type 1 diabetes
- insulin injections
- pancreas transplant
95
what is type 2 diabetes
the body cells no longer respond to insulin produced by the pancreas (or not making enough)
96
what are the causes/risk factors for type 2 diabetes
- genetics
- obesity
- lack of exercise
97
what are the short term symptoms of type 2 diabetes
- increased thirst
- weight loss
- tired
(MILDER SYMPTOMS)
98
what are the long term effects of type 2 diabetes
- increased risk of heart attacks and strokes
- possible blindness
- possible risk of amputation
99
current treatments for type 2 diabetes
- increased exercise
- drugs/medicine
100
how is insulin provided for diabetics today
- diabetics used to have to take insulin from pigs
- bacteria can now be genetically modified to produce human insulin
101
what is the problem w/ pancreas transplants
it is a difficult and risky operation and there are not nearly enough pancreas donors for all type one sufferers
102
what are some treatments being researched/experimented with so far to use instead of pancreas transplants
- in 2005 scientists produced insulin secreting cells from stem cells and used them to cure diabetes in mice
- in 2008 they turned mice pancreas cells that normally made enzymes into insulin producing cells
103
what treatments to cure diabetes scientists hope to develop in the future
- scientists hope that in the future they will be able to genetically engineer faulty human pancreatic cells so that they work properly
- or use stem cells from humans embryos to produce new insulin-secreting pancreas cells
104
what happens if water balance is low
blood becomes more concentrated than cell solution so water moves out of the cell by osmosis through a partially permeable membrane - shrivels up
105
what happens if water balance is too high
blood becomes more dilute than cell solution so water into out of the cell by osmosis through a partially permeable membrane - swells until it bursts
106
what organ plays an important role in maintaining the water balance in our bodies
kidneys
107
what are the inputs of water in our bodies
- water content in food
- water content in drinks
- water made in respiration
108
what are the outputs of water in our bodies
- urine
- sweat
- exhalation (lost as water vapour)
- in faeces
109
how do kidneys work
- your kidneys filter your blood
- glucose, mineral ions, urea and water are all squeezed out of the blood into the nephron
- red blood cells and proteins are too large to leave the blood during the filtering process
- all the glucose is reabsorbed back into the blood as it passes through the nephron by diffusion and active transport
- none of the urea is reabsorbed so that it all goes into the urine formed and is excreted
- the amount of water and mineral ions reabsorbed into the blood varies - selective absorption in order to maintain the conc. in the body
110
describe the negative feedback mechanism for controlling water balance
TOO MUCH SALT/SWEATING:
- water content detected by hypothalamus
- water content of the blood decreases
- pituitary gland produces more ADH
- high vol. of water reabsorbed by kidney
- urine output is low (small vol. of concentrated urine)
-water content of the blood returns to normal
TOO MUCH WATER DRUNK:
- water content detected by hypothalamus
- water content of the blood increases
- pituitary gland produces less ADH
- low vol. of water reabsorbed by kidney
- urine output is high (large vol. of dilute urine)
-water content of the blood returns to normal
111
how are excess amino acids removed from body
- the digestion of proteins from the diet results in excess amino acids which need to be excreted safely
-in the liver these amino acids are deaminated to form ammonia
- ammonia is toxic and so it is immediately converted to urea for safe excretion.
112
what are the consequence of kidney damage or disease
- damage from accidents or disease can lead to a build-up of poisonous wastes in the body
- humans can survive with one kidney, but for people who suffer from total kidney failure this would be fatal if not treated.
113
what is dialysis
acts as an artificial kidney to remove most of the urea and restore/maintain the water and ion balance of the blood
114
how does a dialysis work
- inside the machine the blood and dialysis fluid are separated by a partially permeable membrane – the blood flows in the opposite direction to dialysis fluid, allowing exchange to occur between the two where a conc gradient exists
-the dialysis fluid has no urea in it, there is a large conc gradient - meaning that urea moves across the partially permeable membrane, from the blood to the dialysis fluid, by diffusion. this is very important as it is essential that urea is removed from the patients' blood.
- as the dialysis fluid contains a glucose conc equal to a normal blood sugar level, this prevents the net movement of glucose across the membrane as no conc gradient exists. this is very important as the patients' need to retain glucose for respiration.
- as the dialysis fluid contains an ion conc similar to the ideal blood plasma conc, movement of ions across the membrane only occurs where there is an imbalance.
- if the patient's blood is too low in ions, they will diffuse from the dialysis fluid into the blood, restoring the ideal level in the blood.
- if the patient's blood is too high in ions, the excess ions will diffuse from the blood to the dialysis fluid.
115
advantages of dialysis
- greatly reduced levels of urea – it is 'cleaned blood'
- no overall change in blood glucose levels
- the correct water and ion balance maintained or restored (with only excess ions removed)
116
disadvantages of dialysis
- they are expensive
- the patient must have his or her blood connected to the machine for several hours every week
- patients must follow a very rigid diet to avoid complications
- they only work for a limited time for a patient
117
what is a kidney transplant
involves implanting a kidney from an organ donor into the patient’s body to replace the damaged kidney
118
advantages of a kidney transplant
- patients can lead a more normal life without having to watch what they eat and drink
- cheaper for the NHS overall.
119
disadvantages of a kidney transplant
- must take immune-suppressant drugs which increase the risk of infection
- shortage of organ donors
- kidney only lasts 8-9 years on average
- any operation carries risks
120
what is the main reproductive hormone in males
testosterone - produced by testes
121
what does rising levels of testosterone do
trigger development of the secondary sex characteristics
- stimulates sperm production
122
what are the secondary sex characteristics in males
* increased growth of testes and penis
* deepening voice
* growth of facial and underarm hair
* growth of pubic hair
* growth spurt
* increased muscle mass
123
what is the main reproductive hormone in females
oestrogen - produced in ovaries
124
what does oestrogen trigger the development of
secondary sex characteristics
125
what are the secondary sex characteristics in females
* growth spurt
* growth of underarm and pubic hair
* breasts develop
* fat is deposited on hips and thighs
* mature ova (eggs) develop every month
* menstruation begins
126
describe the menstrual cycle
* days 1-5: uterus lining breaks down and menstruation occurs
* day 6-10: uterus lining begins to thicken again
* days 11-18: ovulation occurs (an egg is released from the ovary)
* days 19-28: uterus lining continues to thicken in preparation to recieve the egg
127
how do hormones control the menstrual cycle
1) pituitary gland in the brain produces FSH
2) FSH causes an egg in the ovary to mature
2a) FSH stimulates the ovaries to produce oestrogen
-> i) oestrogen causes the pituitary gland to releases LH - triggers the release of the egg from the ovary
-> ii) oestrogen prevents more FSH being secreted so no more eggs mature
-> iii) oestrogen also stimulates the ovary to make progesterone which maintains the uterus lining
IF EGG ISN'T FERTILISED:
- progesterone levels drop and the uterus lining breaks down and passes out of the body as the period
IF THE EGG IS FERTILISED:
- progesterone levels remain high and the uterus lining remains so that the baby can develop
128
what does FSH do (follicle stimulating hormone)
causes the egg to mature in the ovary
129
what does LH do (luteinising hormone)
causes the egg to be released from the ovary
130
what does oestrogen and progesterone do
involved in maintaining the uterus lining
131
how is fertility controlled
by a variety of hormonal and non-hormonal methods of contraception
132
what are some hormone based contraceptive methods
- contraceptive pill
- contraceptive injections
- contraceptive implant
- contraceptive patch
133
how do hormone based contraceptive methods work
- release hormones (oestrogen and/or progesterone) to stop FSH being produces
- stops eggs maturing and uterus lining developing
134
what are the advantages of hormone based contraceptive methods
- easy to use
- mostly effective
- very reliable
135
what are the disadvantages of hormone based contraceptive methods
- raised blood pressure
- thrombosis
- breast cancer
- not always effective
- may have to take at specific time of day
136
what are some barrier methods of contraception
- condom
- diaphragm
137
how do barrier methods of contraception work
- prevent sperm reaching egg to prevent fertilisation
138
what are the advantages of barrier methods of contraception
- no side effects
- does not need medical advice
- easy to get a hold of
- offers some protection against STDs
139
what are the disadvantages of barrier methods of contraception
- can get damaged and let sperm through - less reliable
- diaphragm must be fitted by a doctor - if not fitted correctly it will not work
140
what are some examples of IUDs (intrauterine devices)
- coils
can contain hormones
141
how do IUDs work
- small structures inserted into the uterus by a doctor
- prevents the implantation of an embryo in the uterus lining
142
what are the advantages of IUDs
- can be removed if you want to get pregnant
- very effective
- lasts 3-5 years
143
what are the disadvantages of IUDs
- can cause period problems/infections
- has to be inserted by a medical professional
144
what is abstinence
not having sex
145
how does abstinence work
- not having sex= can't get pregnant
- abstaining from sex during/around ovulation means sperm can't fertilise egg
146
what are the advantages of abstinence
- no side effects
- no costs
147
what are the disadvantages of abstinence
- if not 100% abstinence it is a very unreliable method
148
what are some examples of surgical methods of contraception
- vasectomy
149
how do surgical methods of contraception work
- people can be surgically sterilised
- males: sperm ducts cut and tied
- females: oviducts cut/ties
150
what are the advantages of surgical methods of contraception
- effective permanent contraception
151
what are the disadvantages of surgical methods of contraception
- permanent method
- women need general anaesthetic
152
what can be used to treat infertility in women
- giving FSH and LH in a ‘fertility drug’ to a woman -can become pregnant the normal way
- IVF - in vitro fertilisation
153
describe the IVF process
1) mother is given FSH and LH to cause her ovaries to mature and release several eggs
2) ova (eggs) are removed form the mother in a small op.
3) eggs are fertilised by sperm in the lab and allowed to develop into embryos
4) one or two healthy embryos are implanted in the mother's uterus lining
154
benefits of IVF
- couples who are infertile can have the chance to have children
- embryos can be checked for genetic disorders before being implanted
- IVF can increase the chance of having multiple pregnancies
155
problems with iVF
- mature eggs may be stored until later for use which may raise ethical problems if the relationship breaks up
- the use of fertility drugs can have health risks for the mother
- IVF is expensive and not always successful
- excess fertilised eggs may be destroyed which come people think is unethical
- IVF can increase the chance of having multiple pregnancies (can be risk for baby and mother)
156
why do plants produce hormones
control aspects of their growth and development such as;
- growth of roots and shoots
- flowering
- ripening of fruits
157
what is a tropism
a plant response to a stimulus (by growing in diff. directions)
158
what is the stimuli for phototropism
light
159
how do the shoots and roots respond to phototropism
shoots = towards
roots = away
160
what is the stimuli for geotropism
gravity
161
how do the shoots and roots respond to geotropism
shoots = against
roots = towards
162
what is the stimuli for hydrotropism
water
163
how do the shoots and roots respond to hydrotropism
shoots = no response
roots = towards
164
which plant growth substance (hormone) is involved in phototropism
auxin
165
where is auxin produced
tip of the shoot
166
where does auxin have an effect
- growing region - just below the tip
167
how do plants grow when light is coming from all around the plant
1) when plants are exposed to sunlight they produce auxins in the tip of the shoot
2) auxin moves from the tip to the growing region below. when sunlight comes from all around, the conc. of auxin is equal on both sides of the stem
3) auxin causes the stem to grow. if the conc. of auxin is equal on both sides, both sided of the stem will grow at the same rate
4) if a plant continues to receive light from all around the stem will grow straight
168
how does a plant grow when light comes from only one side
1) when plants are exposed to sunlight they produce auxins in the tip of the shoot
2) auxin moves from the tip to the growing region below. when sunlight comes from one side, there will be a higher conc. of auxin moving down the shaded part of the stem
3) auxin causes the stem to grow. if the conc. of auxin is higher on the shaded side, it will cause the shaded side of the stem to grow more than the light side
4) this causes the stem to bend
5) if a plant continues to receive light from one side the stem will grow/bend towards that side
169
what plant growth substance (hormone) controls geotropism
auxin
170
what effect does auxin have on shoot and root cells
shoot = stimulates growth
roots = inhibits growth
171
describe geotropism in plants
1) auxin is produces by the seed and gravity causes it to collect at the base of the shoot and the root
2) in the shoot auxin stimulates growth so the base of the shoot (where the auxin is) will grow more than the other side so it will grow/bend upwards
3) in the root auxin inhibits growth so the top of the root (where there isn't any auxin) will grow more than the base of the root (where the auxin is) causing it to grow/bend downwards
172
what hormone can be used to control seed dormancy
gibberellins
173
how do gibberellins control seed dormancy
used to stop seeds staying dormant and so promote germination
174
why is controlling seed dormancy useful
- seed dormancy must be broken for seeds so be able to germinate so it promotes plant growth
- hormones can be used to remove dormancy so it can germinate at all times of the year
175
what hormone is responsible for fruit ripening
ethene
176
why is fruit ripening useful
- used in the food industry to ripen fruits e.g. bananas
- fruits picked unripe to prevent over-ripening during journey - ripened during storage
177
what hormone is used to make seedless fruits
auxins and gibberrellins
178
why are seedless fruits useful
- hormones stimulate the growth of fruit w/o need for pollination
- some ppl prefer eating fruits w/o seeds
- easier to grow fruit
179
what hormones can be used as weedkillers
auxin
180
how does auxin work as a weedkiller
makes broad leaf plants such as dandelions grow too fast and die but does not affect narrow leaf plants such as grass
181
uses of auxin as a specific weedkiller
- useful for getting rid of dandelions in a lawn w/o killing the grass
- can get rid of weeds that compete w/ crops like wheat
182
what plant hormones can be used t control plant growth (as root powders)
auxin
183
how is auxin used as a rooting powder
plant cuttings can be dipped into hormones to encourage new roots to grow
184
why are rooting powders/cuttings useful
used by gardeners to help cuttings taken from plants to grow into new plants
