Biological Responses Flashcards
(242 cards)
1
Q
What is homeostasis?
A
Maintaining a stable internal environment.
2
Q
Why is it important that your cells need the right conditions?
A
In order to function properly, including the right conditions for enzyme action.
3
Q
Complete the sentence : Homeostasis is about the _______________ of the conditions inside your body to maintain a stable ___________ environment.
A
Regulation, internal.
4
Q
What systems in your body regulate your internal environment?
A
automatic control systems
5
Q
What are two types of communication systems in the body?
A
Nervous and hormonal.
6
Q
Give 3 examples of what the control systems maintain.
A
Body temperature, blood glucose level and water content.
7
Q
What are the three main components that make up your automatic control systems?
A
Receptors, Coordination centres and effectors.
8
Q
What mechanism is used by your automatic control system to maintain a stable internal environment?
A
Negative feedback.
9
Q
Describe (simply) negative feedback when a level decreases.
A
- Receptor detects a stimulus (level is too low).
- The coordination centre recieves and processes information, then organises a response.
- Effector produces a response which counteracts the change and restores the optimum level (the level increases).
10
Q
Describe (simply) negative feedback when a level increases.
A
- Receptor detects a stimulus (level is too high).
- The coordination centre recieves and processes the information, then organises a response.
- Effector produces a response which counteracts the change and restores the optimum level (the level decreases).
11
Q
What does the nervous system do?
A
Detects and reacts to stimuli using electrical impulses.
12
Q
What system means that humans can react to their surroundings and coordinate their behaviour?
A
Nervous system.
13
Q
What are the four main parts of the nervous system?
A
- Central nervous system
- Sensory neurones
- Motor neurones
- Effectors
14
Q
What does CNS stand for?
A
Central Nervous System.
15
Q
In vertebrates, what is the CNS only made up of?
A
The brain and the spinal cord.
16
Q
In mammals, how is the CNS connected?
A
By sensory neurones and motor neurones.
17
Q
What are sensory neurones?
A
The neurones that carry information as electrical impulses from the receptors to the CNS.
18
Q
What are motor neurones?
A
The neurones that carry electrical impulses from the CNS to effectors.
19
Q
What are effectors?
A
All your muscles and glands, which respond to nervous impulses.
20
Q
What can receptors and effectors from part of?
A
A complex organ.
21
Q
What are receptors?
A
The cells that detect stimuli.
22
Q
Give 2 examples of receptors.
A
Taste receptors (on tongue), sound receptors (in ears).
23
Q
What do effectors do?
A
Respond to nervous impulses and bring about a change.
24
Q
What do muscles do in response to a nervous impulse?
A
Contract.
25
What do glands do in response to a nervous impulse?
Secrete hormones.
26
What is a synapse?
A connection between two neurones.
27
How do electrical impulses travel between two neurones?
The nerve signal is transferred by chemicals which diffuse across the synapse. These chemicals trigger a new electrical signal in the next neurone.
28
True or false. Neurones transmit information to the brain faster than a reflex.
False.
29
What do reflexes do?
Help prevent injury.
30
What are reflexes?
Rapid, automatic responses to a certain stimuli that dont involve the conscious part of the brain - they reduce the chances of being injured.
31
Give 2 examples of a reflex.
1. When your eyes are exposed to a bright light, your pupils automatically get smaller so less light gets into the eye, reducing damage.
2. If you get a shock, your body releases the hormone adrenaline automatically.
32
What is a reflex arc?
The passage of information in a reflex - from a receptor to an effector.
33
Name the 8 stages of the reflex arc.
Stimulus
Receptor
Sensory neurone
CNS
Relay neurone
Motor neurone
Effector
Response
34
What do neurones in a reflex arc go through?
The spinal cord or unconscious part of the brain (Medulla).
35
Why are reflexes faster than regular neurones?
They are unconscious responses.
36
What is the practical investigating the time it takes to respond to a stimulus?
The ruler drop test - reaction time.
37
Name the IV in the ruler drop test.
Caffeine or amount of sleep - changing anything that would affect reaction time.
38
Name the DV in the ruler drop test.
Reaction time/ time taken to catch the ruler after being released.
39
Name some CV in the ruler drop test.
- Same person to catch the ruler each time
- Person uses the same hand to catch the ruler
- Ruler dropped from the same height
- The person has not had anything that could affect their reaction time before the experiment.
40
Give the method for the ruler drop practical.
1. The person being tested should sit with their arm resting on the edge of a table.
2. Hold a ruler vertically between their thumb and forefinger. Make sure the zero end is level with their finger.
3. Let go of the ruler with no warning.
4. Reaction time is measured by the number on the ruler where it is caught - the higher the number the longer the reaction time.
5. Repeat several times and calculate a mean.
6. The person being tested should then have caffeine and after 10 minutes, repeat steps 1-5.
41
How can reaction time be measured?
Using a computer
42
What is the advantage of using a computer to measure reaction time?
- More precise as they remove the possibility of human error
- Can record in milliseconds, giving a more accurate measurement
- Can remove the possibility of the person predicting when to respond
43
What is one factor that affects human reaction time?
age, gender, drugs
44
What is the brain responsible for?
Complex behaviours
45
What is the central nervous system made up of?
The spinal cord and the brain
46
What is the CNS made up of?
interconnected neurones
47
What is the function of the Cerebral Cortex?
It is responsible for consciousness, intelligence, memory and language
48
What is the function of the Medulla?
Controls unconscious activities e.g. breathing
49
What is the function of the Cerebellum?
Responsible for muscle coordination
50
What part of the brain is responsible for consciousness, intelligence, memory and language?
Cerebral Cortex
51
What part of the brain controls unconscious activities?
Medulla
52
What part of the brain is responsible for muscle coordination?
Cerebellum
53
What are scientists that study the brain called?
neuroscientists
54
How do scientists study the brain?
Electrically stimulating the brain by removing the top of the scull and inserting a tiny electrode into the tissue. Because the brain has no sensory nerve endings, this can be done on conscious patients so that they can investigate the effects of stimulating different parts of the brain.
55
What does MRI stand for?
Magnetic Resonance Imaging
56
What do MRI scanners do?
Take images to show exactly where the brain is affected.
This can be used to find what areas of the brain are active when the patient is doing particular things.
57
Why is electrical stimulation of the brain done on conscious patients?
There are no sensory nerve endings in the brain
58
Why is electrical stimulation of the brain done on conscious patients?
There are no sensory nerve endings in the brain
59
What can electrical stimulation on the brain help reduce?
muscle tremors caused by nervous system disorders (e.g. Parkinson’s disease)
60
What are the risks of investigating the brain?
Could cause physical damage to the brain or increased problems with brain function
61
Why is it difficult to investigate and treat brain disorders?
- Synapses of the brain can be easily damaged
- Drugs do not always reach the brain through the membranes that surround it
- Surgery can be dangerous as it is not fully understood
62
What is the eye?
A sense organ
63
What is the Sclera?
the tough, supporting wall of the eye
64
What is the Cornea?
the transparent outer layer found at the front of the eye, it refracts light into the eye
65
What is the Iris?
it contains muscles that allow it to control the diameter of the pupil and how much light enters the eye
66
What is the Pupil?
The hole in the middle of the eye that lets light through
67
What is the Lens?
it focuses the light onto the retina
68
What is the Retina?
it contains receptor cells sensitive to light intensity and colour
69
What is the shape of the lens controlled by?
Ciliary muscles and suspensory ligaments
70
What is the function of ciliary muscles and suspensory ligaments?
controls the shape of the lens
71
What is the optic nerve?
the nerve that carries electrical impulses from the receptors on the retina to the brain
72
Describe the Iris reflex in bright light.
The light receptors on the retina detect very bright light. They trigger the circular muscles in the iris to contract and the radial muscles to relax. This makes the pupil smaller and reduces the amount of light that can enter the eye.
73
Describe the Iris reflex in dim light.
The light receptors on the retina detect dim light. They trigger the circular muscles in the iris to relax and the radial muscles to contract. This makes the pupil larger and allows a larger amount of light to enter the eye.
74
Describe the reflex when looking at near objects.
The ciliary muscles contract, which slackens the suspensory ligaments.
The lens becomes more curved.
This increases the amount by which it refracts.
75
Describe the reflex when looking at distant objects.
The ciliary muscles relax causing the suspensory ligaments to pull tight.
This makes the lens thinner and less curved.
So it refracts the light by a smaller amount.
76
What is the medical term for long-sightedness?
hyperopia
77
What are long-sighted people unable to focus on?
near objects
78
What is hyperopia?
Long-sightedness:
When the lens is the wrong shape or the eyeball is too short, images of near objects are brought into focus behind the retina.
79
Where are images of near objects brought into focus if a person has hyperopia?
behind the retina
80
What type of lens can be used to treat hyperopia?
Convex lens
81
What is a convex lens?
A lens which curves outwards and increases refraction.
82
What is the medical term for short-sightedness?
myopia
83
What are short-sighted people unable to focus on?
distant objects
84
What is myopia?
Short-sightedness:
When the lens is the wrong shape and refracts light too much or the eyeball is too long.
The image of distant objects are focused in front of the retina.
85
Where is the image of distant objects brought into focus of a person with myopia?
in front of the retina
86
What type of lens can be used to correct short-sightedness?
Concave lens
87
What is a concave lens?
A lens that curves inwards and reduces refraction
88
Glasses are used to treat vision defects. What are 3 other ways of treating this?
Contact lenses
Laser eye surgery
Replacement lens surgery
89
What are contact lenses?
Thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing.
90
What are the advantages of contact lenses?
Lightweight
Almost invisible
More convenient for sport
91
What are the two types of contact lenses?
Hard lenses and soft lenses
92
True or false: Soft contact lenses are more comfortable than hard lenses.
True
93
True or false: Soft contact lenses are more comfortable than hard lenses.
True
94
What are the disadvantages of contact lenses?
Risk of eye infection
Have to be replaced daily
95
What is laser eye surgery?
A laser is used to vaporise tissue, changing the shape of the cornea (so how strongly it refracts light into the eye).
96
How is laser eye surgery used to correct short-sightedness?
Slimming the cornea down makes it refract less.
97
How is laser eye surgery used to correct long-sightedness?
Changing the shape of the cornea can make it more powerful and refract light more.
98
What are the advantages of laser eye surgery?
- The surgeon can precisely control how much tissue is removed
- It is permanent
99
What is the disadvantage of laser eye surgery?
Risk of complications such as infection or making the vision worse
100
What is replacement lens surgery?
Replacing the lens of the eye with an artificial lens made of clear plastic
101
What type of vision defect is often treated by replacement lens surgery?
hyperopia
102
What is the disadvantage of replacement lens surgery?
- It involves work inside the eye so carries higher risks
- Could damage retina resulting is loss of sight
103
What is the body’s optimum temperature?
37°C
104
What increases body temperature?
respiration
105
Where is the thermoregulatory centre located?
Brain
106
What does the thermoregulatory centre contain?
receptors that are sensitive to the temperature of the blood flowing through the brain
107
Describe the reflex for an increased body temperature.
1. Temperature receptors detect that the core body temperature is too high
2. Thermoregulatory centre recieves information and triggers the effectors
3. Sweat glands produce sweat that evaporates from the skin, transferring energy to the surroundings
4. Hairs lie flat
5. Blood vessels dilate so more blood flows closer to the surface of the skin (Vasodilation)
108
Describe the reflex for a decrease in body temperature.
1. Temperature receptors detect that the core body temperature is too low
2. Thermoregulatory centre recieves information and triggers the effectors
3. Hairs stand up to trap an insulating layer
4. No sweat is produced
5. Blood vessels constrict to close off the skins blood supply (vasoconstriction)
6. You shiver to cause muscles to contract and respire
109
What are hormones?
Chemical messengers sent in the blood
110
What are hormones carried in?
the bloodstream
111
What do hormones do?
Control things in organs and cells that need constant adjustment.
112
Where are hormones produced/secreted?
endocrine glands
113
What do endocrine glands make up?
the endocrine system
114
True or false: Hormones do not have long lasting effects.
False
115
What are the 6 endocrine glands?
Pituitary Gland
Thyroid
Adrenal Gland
Pancreas
Ovaries (female)
Testes (male)
116
What is the pituitary gland also known as?
the ‘master’ gland
117
What hormones does the pituitary gland release in females?
FSH and LH
118
What does the thyroid produce?
Thyroxine
119
What does the hormone thyroxine do?
regulates the rate of metabolism, heart rate and temperature
120
What does the adrenal gland produce?
Adrenaline
121
What does the hormone adrenaline do?
prepares the body for ‘fight or flight’
triggers mechanisms to increase the supply of oxygen and glucose to cells in the brain and muscles
122
What does the pancreas produce?
insulin
123
What does the hormone insulin do?
regulates blood glucose levels by triggering the liver to store excess glucose as glycogen
124
What do the ovaries produce?
oestrogen and progesterone
125
What are oestrogen and progesterone involved in?
the menstrual cycle
126
What do the testes produce?
testosterone
127
What does the hormone testosterone do?
controls puberty and sperm production in males
128
What does the hormone testosterone do?
controls puberty and sperm production in males
129
What are the three differences between nerves and hormones?
1. Nerves are fast action, hormones are slow action.
2. Nerves act for a very short time, hormones act for a long time.
3. Nerves act on a specific area, hormones act in a more general way
130
Describe the reflex when blood sugar levels are too high.
1. Receptors detect blood with too much glucose.
2. Pancreas releases insulin.
3. Insulin travels through blood and causes liver to store glucose as glycogen.
4. Blood glucose is reduced
131
Describe the reflex when blood sugar levels are too low.
1. Receptors detect blood with too little glucose.
2. Pancreas releases glucagon.
3. Glucagon travels through bloodstream and causes liver to turn glycogen into glucose.
4. Blood glucose levels increase
132
What hormone causes blood glucose levels to rise?
Glucagon
133
What hormone causes blood glucose levels to fall?
insulin
134
What is diabetes?
When the body cannot control its blood sugar levels
135
What is type 1 diabetes?
When little or no insulin is made
136
How is type 1 diabetes treated?
Insulin therapy
Limit intake of carbohydrates
Exercise regularly
137
What is type 2 diabetes?
Insulin resistance
138
What are the risk factors of type 2 diabetes?
Obesity
139
How can type 2 diabetes be treated?
Regular exercise
Eating a carbohydrate controlled diet
140
What is the role of the kidneys?
They make urine by taking out waste products from the blood
141
What substances are reabsorbed after being filtered by the kidneys?
glucose, some ions and some water
142
What is selective reabsorption?
Useful substances being reabsorbed into the bloodstream after being filtered by the kidneys
143
What are three substances removed from the body in urine?
Urea
Ions
Water
144
What is urea made from?
1. excess amino acids converted into fats and carbohydrates
2. ammonia
145
What is deamination?
amino acids being broken down into fats and carbohydrates in the liver
146
Why does ion concentration need to be maintained by the kidneys?
Ions draw water out of cells by osmosis.
Having the wrong amount of water can damage cells or their function.
147
What is the concentration of urine controlled by?
the hormone:
anti-diuretic hormone (ADH)
148
What is ADH produced by?
the pituitary gland
149
What monitors the water content of the blood?
receptors in the brain
150
Describe the reflex for too high water content in the body.
1. Receptors in brain detect too high water content
2. The coordination centre in the brain receives information and coordinates a response
3. The pituitary gland releases less ADH so less water is reabsorbed from the kidney tubules
151
What does the hormone ADH do?
triggers the kidneys to reabsorb more water
152
Describe the reflex for too low water content in the body.
1. Receptors in the brain detect too low water content
2. The coordination centre receives the information and coordinates a response
3. The pituitary gland releases more ADH so more water is reabsorbed from the kidney tubules
153
What will happen if the kidneys do not work properly?
Waste substances build up in the blood and you lose your ability to control levels of ions and water eventually resulting in death
154
What are the two ways kidney failure can be treated?
Dialysis treatment or kidney transplant
155
What does a dialysis machine do?
filter the blood
156
How does a dialysis machine work?
1. The person’s blood flows between partially permeable membranes, surrounded by dialysis fluid.
2. The membranes are permeable to ions and waste substances but not large molecules like proteins.
3. Waste substances and excess ions and water diffuse across the barrier out of the blood and into the dialysis fluid
157
What concentration of dissolved ions and glucose does dialysis fluid have in comparison to healthy blood?
the same
158
Why does dialysis fluid have the same concentration of dissolved ions and glucose as healthy blood?
So that useful dissolved ions and glucose wont be lost during dialysis.
159
How often do patients with kidney failure have a dialysis session?
three times a week
160
How long do dialysis sessions take?
3-4 hours
161
What are the disadvantages of dialysis?
- patients have frequent sessions of 3-4 hours
- can cause blood clots or infections
- is not pleasant experience
- expensive for the NHS
162
What is the only cure for kidney failure?
kidney transplants
163
Where do kidney transplants come from?
- people who have died suddenly
- a healthy donor (people have two kidneys)
164
What is a kidney transplant?
Replacing a damaged or failed kidney with a healthy one from a different person
165
What are the advantages of kidney transplants?
- they are a cure
- they are cheaper than dialysis
- they are a permanent solution
166
What are the disadvantages of kidney transplants?
- they could be rejected by the patient’s immune system
- there are long waiting lists for them
167
What can be done to reduce the risk of rejection during a kidney transplant?
the patient is treated with drugs before hand
168
What is the main reproductive hormone in men?
testosterone
169
What is the main reproductive hormone in women?
oestrogen
170
What is one change that a women experiences during puberty?
- breasts develop
- eggs mature
- periods start
171
What is one change that men experience during puberty?
facial hair
172
How many stages does the menstrual cycle have?
four
173
What happens in stage 1 of the menstrual cycle?
Day 1- 4
Menstruation starts
The uterus lining breaks down
174
Approximately how long is stage 1 of the menstrual cycle?
4 days
175
What happens in stage 2 of the menstrual cycle?
Day 4 - 14
The uterus lining builds up again into a thick spongy layer full of blood vessels ready to receive a fertilised egg
176
Approximately how long is stage 2 of the menstrual cycle?
10 days
177
What happens in stage 3 of the menstrual cycle?
Day 14
An egg develops and is released from the ovary (Ovulation)
178
Approximately how long is stage 3 of the menstrual cycle?
1 day
179
What happens in stage 4 of the menstrual cycle?
Day 14 - 28
The wall is maintained.
If no fertilised egg has landed on the uterus wall by day 28 then the lining begins to break down
180
What hormones are involved in the menstrual cycle?
FSH
Oestrogen
LH
Progesterone
181
What does FSH stand for?
Follicle-Stimulating Hormone
182
What does LH stand for?
Luteinising Hormone
183
What does FSH do and where is it produced?
- Produced in the pituitary gland
- Causes egg to mature in a structure called a follicle
- Stimulates the ovaries to produce oestrogen
184
What does oestrogen do and where is it produced?
- Produced in the ovaries
- Causes the lining of the uterus to grow
- Stimulates the release of LH
- Inhibits the release of FSH
185
What does LH do and where is it produced?
- Produced in the pituitary gland
- Stimulates the release of an egg at day 14 (ovulation)
186
What does progesterone do and where is it produced?
- Produced in the ovaries
- Maintains the lining of the uterus
- Inhibits the release of LH and FSH
187
Which hormones can be used to reduce fertility?
Oestrogen and progesterone
188
How can oestrogen be used to reduce fertility?
It prevents the release of an egg if taken everyday as it inhibits the production of FSH so egg development and production stop
189
How can progesterone be used to reduce fertility?
It stimulates the production of thick mucus which prevents sperm from getting through and reaching the egg
190
What hormones does the pill contain?
Oestrogen and Progesterone
191
What is the advantage of the contraceptive pill?
over 99% effective
192
What are the two types of contraceptive pill?
combined oral contraceptive pill
or
progesterone-only pill
193
What are the disadvantages of the contraceptive pill?
can cause side effects
doesn’t protect against STDs
has to be taken every day (easily forgotten)
194
What is the contraceptive patch?
A patch that contains oestrogen and progesterone that is stuck to the skin
195
What are the disadvantages of the contraceptive patch?
Only lasts a week
Doesn’t protect against STDs
196
What is the contraceptive implant?
a device inserted under the skin that produces a continuous amount of progesterone which stops the ovaries from releasing eggs
197
How long can the contraceptive implant last?
three years
198
What is the contraceptive injection?
An injection of progesterone to stop the ovaries from releasing eggs
199
How long does the contraceptive injection last?
2-3 months
200
What does IUD stand for?
IntraUterine Device
201
What shape is an IUD?
T-shaped
202
What is an IUD?
A device inserted into the uterus to kill sperm and prevent implantation of a fertilised egg, also can release progesterone
203
What are the two main types of IUD?
Plastic- releases progesterone
Copper- prevents sperm surviving in the uterus
204
What is the only form of contraception that protects against STDs?
Condoms
205
What are barrier methods?
Methods to stop the sperm reaching the egg
206
What is sterilisation?
cutting or tying
the fallopian tubes in a female
or
the sperm duct in a male
(often permanent)
207
What are ‘natural methods’ of contraception?
avoiding sexual intercourse when a woman is most fertile
208
What is abstinence?
not having intercourse
209
What hormones can be given to increase fertility?
FSH and LH
210
What is the advantage of using hormones to increase fertility?
Can help women to get pregnant when they couldn’t before
211
What are the disadvantages of using hormones to increase fertility?
- doesn’t always work, costs can be expensive
- too many eggs could be stimulated resulting in unexpected multiple pregnancies (twins, triplets…)
212
What is an IVF?
‘in vitro fertilisation’
213
How does an IVF work?
1. Collecting eggs from the woman’s ovaries and fertilising them in a lab with the man’s sperm
2. The fertilised eggs then grow into embryos in an incubator
3. Once embryos have formed, one or two are transferred into the woman’s uterus to improve the chance of pregnancy
214
What is the advantage of an IVF?
Can give an infertile couple a child of their own
215
What are the disadvantages of IVF?
- could result in multiple births
- high risk of miscarriage or still birth
- low success rate (26% in UK)
- emotionally stressful
- physically stressful for the woman
216
What advances in technology have improved IVF?
1. Advances in microscope techniques
2. Specialised micro-tools
3. Time-lapse imaging means they can be continuously monitored
217
Why are some people against IVF treatment?
- unused embryos are eventually destroyed, can be seen as unethical as each embryo is a potential human life
- genetic testing of embryos as some people believe it could lead to a selection of preferred characteristics (gender/eye colour)
218
Where are the adrenal glands located?
just above the kidneys
219
What is one thing that adrenaline does to the body?
increases heart rate
220
Where is the thyroid gland located?
back of the neck
221
What is basal metabolic rate?
the speed at which chemical reactions in the body occur whilst the body is at rest
222
What processes are thyroxine important for?
protein synthesis, growth, development, metabolism
223
What is thyroxine released in response to?
thyroid stimulating hormone (TSH) from pituitary gland
224
What happens when the level of thyroxine in the blood is too high?
the secretion of TSH is inhibited
225
What is auxin?
A plant growth hormone
226
What does the hormone auxin do?
controls growth near the tips of shoots and roots in response to light of gravity
227
How does auxin cause growth?
It moves backwards to stimulate the cell elongation process which occurs just behind the tips
228
Where is auxin produced?
the tips of shoots and roots
229
What will happen to a plant if the tip of a shoot is removed?
No auxin is available so the shoot may stop growing
230
What does extra auxin promote and inhibit?
promotes growth in the shoot
and inhibits growth in the root
231
What is the term for plants growing towards light?
phototropism
232
What is the term for plants growing towards the centre of the earth?
gravitropism
233
Describe how a shoot grows towards light.
1. More auxin accumulates on the side that is in the shade than the side that is in the light.
2. This causes the cells on the shaded side to grow faster causing the shoot to bend towards the light.
234
Describe how a shoot grows away from gravity.
1. When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side.
2. This causes the lower side to grow faster, resulting in the shoot bending upwards.
235
Describe how a root grows towards gravity.
1. A root growing sideways has more auxin on its lower side.
2. But in a root, extra auxin inhibits growth so the cells on top elongate faster and the root bends downwards.
236
How can you investigate plant growth in response to light?
1. Put 10 cress seeds into three different petri dishes, each lined with damp cotton wool. Label each dish A, B & C
2. Place one of the dishes in bright light, one in natural light and one in a dark cupboard.
3. Record the growth of each seed in each dish every two days for a week with a ruler.
4. Observe the responses to light.
237
What control variables are required for investigating plant growth in response to light?
- same number of seeds in each dish
- type of seed
- temperature
- volume of water in each dish
- light intensity (if not IV)
238
What are the three uses of auxin?
1. Killing weeds (disrupts normal growth and kills them)
2. Growing from cuttings with root powder
3. Growing cells in tissue culture
239
What is gibberellin?
a plant growth hormone that stimulates seed germination, stem growth and flowering
240
What are the three used of gibberellin?
1. Controlling dormancy
2. Inducing flowering
3. Growing larger fruit
241
What is ethene?
A gas produced by aging parts of a plant, it influences the growth of plants and stimulates enzymes to cause fruit to ripen
242
What are the uses of ethene?
speeds up the ripening of fruit
so that they can be picked unripe
