B5 - Homeostasis - Paper 2 Flashcards
What is body temperature controlled by (in the brain)?
Thermoregulatory centre - hypothalamus
Give the two ways we detect temperature of the body
Thermoregulatory centre in the brain detects blood temp
Skin detects skin temp and sends these signals to the thermoregulatory centre
Why is it important to maintain optimum body temperature?
To Maintain optimum enzyme activity
What is the main mechanism for control of homeostasis (general)
Negative feedback
Give one way body temp can be decreased once it reaches an above optimum temperature (not to do with blood vessels)
Sweat
How does sweat cool us down
Layer of liquid perspiration which evaporates taking heat energy away from the skin
How does shivering warm us up
Body movement = respiration = release of thermal energy
How does hair standing on end (goosebumps) help to warm up?
Traps body heat as a layer of air insulation
What controls the response of blood vessels to heat or cold
The hypothalamus
Give 2 things which happen if body is detected as too hot
Vasodilation of blood vessels close to the skin
Shunt vessels further from the skin constrict
What are shunt vessels?
Vessels below the skin (further from the surface than others)
Why does vasodilation of blood vessels close to the surface of the skin help to reduce body temperature
More blood is travelling through them
Heat is lost through radiation through the skin
What happens to blood vessels when too cold?
Vasoconstriction of blood vessels close to the skin
Shunt vessels further from the skin become dilated
How does vasoconstriction work to maintain body temperature
Diverting blood away from the skin means less heat is lost through radiation
Describe the reflex arc of stimulus to response on a hot day
Hot day->skin receptor->sensory neurone -> relay neurone (in spine) ->motor neurone -> gland effector (sweat)
What is the optimum temperature of the human body?
37 degrees
When talking about homeostasis in an exam always describe what?
Negative feedback loops
Why is it important to maintain blood glucose concentration?
Regulation of cellular respiration
High levels of blood glucose are poisonous
What organ is blood glucose concentration controlled by?
The pancreas
What is the name for the store of glucose?
Glycogen
How do you remember what glycogen is?
It has an e on it and glucose does as well but glucagon doesn’t have an e
Where is glycogen found?
Liver and muscles
What is insulin?
A hormone that increases the amount of glucose stored as glycogen
How do you remember what insulin goes to glucose?
Insulin ‘insulates’ the glucose as glycogen
What hormone breaks glycogen back into glucose?
Glucagon
How do you remember that glucagon breaks down glycogen to glucose?
GlucAgon Attacks the glycogen to make glucose
Explain a negative feedback loop for blood sugar levels (increase in glucose back to optimum)
Increase in blood sugar due to eating
Detected by pancreas
Increases insulin secretion (hence glucose stored as glycogen in muscle and liver)
Blood glucose levels decrease back to normal
Describe the negative feedback loop after a decrease in blood sugar levels (the going back to optimum)
Decrease in blood sugar due to exercise
Detected by pancreas cells
Increase in glucagon secretion (breaking down glycogen in liver/muscles back to glucose and glucose released into blood
Glucose increases back to normal
What is diabetes
When blood glucose levels can’t be regulated
True or false: type 1 diabetes is genetic
True
Give 5 issues with too much blood glucose
Toxic
Decreases blood vessel elasticity
Glucose left as deposits (atherosclerosis)
Miscarriage risk
Dehydration
What 2 negative effects can result from narrowing of blood vessels due to excessively high blood glucose concentrations
Impeding blood flow to the eyes
Could lead to nerves stopping sending signals
True or false: blood vessels also have to supply nerves with glucose and oxygen
Trye
What is another word for the process of glucose being left as deposits?
Atherosclerosis
What can atherosclerosis lead to?
CHD
Why can there be a miscarriage risk if blood glucose too high (2 details)
Less supply of oxygen for the baby
Excess amniotic fluid puts pressure on organs
Why does high blood glucose concentration lead to dehydration?(4 steps)
Kidneys usually take required amount of glucose out of urine to be retained
Can’t keep up with very high glucose concentrations
Excess glucose has to be expelled in high volumes of urine
Leading to dehydration
Type 1 diabetes is when ___cant produce any/enough ____ due to the destruction of ____ producing cells
The pancreas
Insulin
Insulin
Give 5 things type 1 diabetes could lead to
Kidney damage
Heart problems
Blindness
Nerve damage
Damage to circulation
Give 4 symptoms of type 1 diabetes
Tiredness
Losing weight
Passing lots of urine
Feeling very thirsty
Give 3 treatments for type 1 diabetes
Insulin injection/insulin pump (which monitors blood glucose levels and adjusts insulin to fit)
Healthy diet
Regular exercise
What is an insulin pump?
Monitors blood glucose levels and adjusts insulin injection to fit the requirement
What is type 2 diabetes?
Pancreas produces insulin but cells aren’t sensitive/don’t respond to it
Glucose uptake (into glycogen) doesn’t happen so blood glucose concentration stays high
True or false: symptoms and potential after effects of type 1 and type 2 diabetes are different
False - they are the same
Give 3 treatments for type 2 diabetes
Healthy diet
Exercise regimes
Oral medications to control blood glucose concentrations
Give 2 risk factors for type 2 diabetes
Obesity
Poor diet + minimal exercise
Digestion of proteins results in excess ____ ____ (which contain ____) which need to be excreted _____
Amino acids
Nitrogen
Safely
What is deamination?
The removal of an amino group from an amino acid
What is the main product after the deamination of an amino acid?
Ammonia
True or false: ammonia is highly toxic for the body
True
What is ammonia converted into following deamination?
Urea
How is urea excreted?
In urine
What is water potential?
The likelihood of water molecules to move by osmosis into or out of a solution
Give 3 ways water can be lost by the body
Breathing OUT (can’t just say breathing)
Sweat
Urine
During exhalation what leaves the body via the lungs
Water vapour
Give 3 things lost through the skin via sweat
Water, ions, urea
What 3 things are removed via kidneys through urine
Excess water, ions and urea
Give 2 things which the kidney does to regulate water, glucose, ion concentrations in the body
Filtration and selective reabsorption
Describe what happens when the kidney filters blood
All small molecules (water, glucose, urea, ions) filtered from blood by kidney
What is selective reabsorption?
Right amount of water and ions and glucose re absorbed back into the blood depending on the body’s needs
What are the kidney tubules?
The part of the kidney where filtration and selective reabsorption occurs
What is ADH?
Controls the amount of water re absorbed back into blood
What is ADH produced by?
Pituitary gland
More ADH = more/less permeable
More permeable
More permeable kidney tubules = more/less water reabsorbed into the blood and more/less water lost via urine
More
Less
What is water concentration in the blood detected by
The hypothalamus
Blood water concincreases = more/less ADH
Less ADH - less permeable tubules - more dilute urine
What is a dialysis machine?
Removes waste products and excess fluid from the blood
What is dialysis used for?
Kidney failure
What would happen if your kidneys failed and why?
Damage to several organs and organ systems/ eventually death because
- waste substances would build up
- water content uncontrolled
- ion levels uncontrolled
Give 2 necessary dietary changes while on dialysis
Avoid salty foods (prevent ion build up between dialysis sessions)
Limit fluid content (prevent water content being too high, diluting blood and increasing blood pressure)
Give the 5 stages of a dialysis machine
Arterial Blood leaves arm
Anticoagulants (blood thinners) administered to prevent clotting
Blood runs through dialysis machine
Clean blood runs through bubble trap to get rid of bubbles
Clean blood returns to the arm
Dialysis fluid has the ____ concentration of glucose and mineral ions as healthy blood but is _____ in ____ and ____
Same
Low
Salt
Urea
Excess salt and urea moves out of the blood into the dialysis fluid through a partially permeable membrane in a dialysis machine by _____
Diffusion (along a concentration gradient)
True or false: there is a net movement of glucose and mineral ions in a dialysis machine
False
What is the function of a dialysis machine?
Filter blood and maintain safe ion concentration in the blood by removing excess ions and waste substances such as urea
Give 2 disadvantages of dialysis
Requires 3 sessions per week per patient
Costs around £300 per session
Give 1 advantage of dialysis
Readily available
Give 1 advantage of kidney transplants
Long term solution to kidney damage + a one time operation
Give a disadvantage of kidney transplants
Take a long time to be found
As an exact tissue match has to be found
What is thyroxine
A hormone released by the thyroid gland
What is thyroxine released by
The thyroid gland
What does thyroxine control
Basal metabolic rate (rate of energy transfers/chemical reactions in cells)
What is TSH?
Thyroid stimulating hormone
What is TSH released by
The pituitary gland
What does TSH do?
Controls how much thyroxine the thyroid gland produces
Give the negative feedback loop of thyroxine and TSH
Thyroxine levels too high - TSH secretion stops to reduce thyroxine back to optimum
Thyroxine levels too low - TSH secretion increases to increase thyroxine back to optimum
What recognises that thyroxine levels are too high?
Hypothalamus
What is adrenaline released by?
The adrenal gland
Why is adrenaline released?
In response to stressful situations
What does adrenaline do?
Gets body ready for fight or flight
Give the reflex arc for the release of adrenaline and it’s physical effects
Brain detects fear/stress
Sends nervous impulse to the adrenal glands
Adrenal glands release adrenaline
This increases heart rate to increase supply of oxygen and glucose to brain and muscles
What does adrenaline do physically?
Increase heart rate to increase supply of oxygen and glucose to the brain and muscles
What is oestrogen secreted by?
Ovaries
Where is oestrogen secreted to?
The uterus
And pituitary gland
What is testosterone secreted by
The testes
Where is testosterone secreted to?
Sex organs
What does oestrogen control the development of?
Female secondary sexual characteristics
Give 3 examples of female secondary sexual characteristics
Menstruation every 28 days
Development of breasts
Widening of hips
(Puberty basically)
Give 3 examples of make secondary sexual characteristics
Muscle development
Hair growth
voice breaking
Sperm production
(Puberty basically)
How long is the menstrual cycle?
28 days
Days 1-7 of the cycle what happens?
Uterus lining shed through the vagina
Days 8-13 what happens?
Uterus lining rebuilds
What happens on day 14
Egg released from ovaries = ovulation
What happens days 15-28
Uterus lining stays thick
If the egg is fertilised then uterus lining stays __ and there is __- period
Thick
No
If it is not fertilised the egg ____ via the ____
Leaves
Period
What does FSH do?
Causes the egg to mature in the ovary
What is FSH produced by?
The pituitary gland
What does FSH stimulate?
Release of oestrogen from ovaries
What does oestrogen do?
Repairs and thickens uterus lining
What is oestrogen produced by?
The ovaries
What does oestrogen stop being produced?
FSH
Why does oestrogen stop the release of FSH?
So only one egg matures
What does oestrogen stimulate?
Stimulates the pituitary gland to release LH
What is LH triggered by?
Oestrogen
What is LH released by?
The pituitary gland
What does progesterone do?
Maintains uterus lining
What is progesterone produced by?
By the follicle (which releases the egg - its a yellow body)
It is then released by the ovaries
At the start of the cycle ___ is high as an egg is maturing in the ovaries?
FSH
After FSH is high at the start then ____ peaks, stopping ___ production so the egg matures and ____ the uterus lining
Oestrogen
FSH
Develops
After oestrogen peaks ___ peaks and the ___ is released
LH
Egg
After the egg is released then ___ peaks to maintain the ___ uterus lining
Progesterone
Thick
What type of contraceptive method is the combined pill?
Hormonal
Give 3 ways in which the combined pill works as a contraceptive
Leaves thick cervical music to stop sperm entering
Consistent high levels of oestrogen to stop FSH
Progesterone stops LH production
Oestrogen presence inhibits what?
FSH
Progesterone stops ___ production
LH
Give 4 advantages of the combined pill
Free on the NHS
99% effective
Reduces risks of some cancers
Makes bleeds light and regular
Give 5 disadvantages of the combined pill
Not effective if vomiting
Not 100% effective
Side effects
No STD Protectiom
Can increase risk of blood clots and some cancers
Give 3 possible side effects of the combined pill
Nausea
Headaches
mood swings
The progesterone only pill is a ___ method of contraception
Hormonal
Give 2 ways the progesterone only pill works as a contraceptive
Ensures thick cervical mucus
Prevents ovulation by limiting LH production
Give 4 advantages of the progesterone only pill
At least 99% effective
Fewer side effects than the combined pill
Free on the NHS
Suitable if you have high blood pressure/a history of blood clots
Give 3 disadvantages of the progesterone only pill
Disadvantages
Just take it same time each day
No STD protection
Some medications make it less effective
How do surgical methods of contraception work?
Cutting or tying fallopian tubes or sperm duct
Give 2 advantages of the surgical method
Permanent
100% effective
Give 2 disadvantages of the surgical method
Permanent
Risks of surgery
Is spermicide a hormonal or non hormonal method
Non hormonal
How does spermicide work?
Kills or disables sperm
Give 2 advantages of spermicides
Non invasive
Short term
Give 2 disadvantages of spermicide
Only 70-80% effective
No STI protection
What is abstinence
Avoiding sex during most fertile periods
Give 1 advantage of abstinence
Popular with those that consider hormonal/barrier methods unnatural
Give 2 disadvantages of abstinence as a contraceptive technique
Not very effective
No protection from STIs
How does a condom work?
Prevents sperm entering vagina (worn over penis)
Female condoms also available
Give 3 advantages of condoms
Advantages
Only contraceptive that effective against STDs
98% effective
No side effects
Give 3 disadvantages of condoms
Disadvantages
Costs money (if not at sexual health clinic)
Can tear
Some have allergies to latex
What is a diaphragm?
Shallow plastic cup over cervix (entrance of uterus)+combines with a spermicide (substance disabling/killing sperm)
What % effective is a diaphragm?
92-96% effective
Give 2 advantages of a diaphragm
92-96% effective
No side effects
Give 2 disadvantages of a diaphragm
Limited protection against STDs
Limited effectiveness
Is the contraceptive patch a hormonal method?
Yes
How does the contraceptive patch work?
Contains oestrogen and progesterone - small patch stuck on skin for a week
Progesterone stops egg release
High levels of oestrogen prevent egg maturing so not released
Give 5 advantages of the contraceptive patch
Easy to use
Still effective if vomiting
Over 99% effective
Lighter and regular periods
Free on the NHS
Give 4 side effects of the contraceptive patch
Nausea
Headaches
Mood swings
Increased risk of breast cancer
Visible skin irritation
Give 1 disadvantage of the contraceptive patch.
No STD protection
Give 3 ways the contraceptive implant works
Continuous progesterone
Makes uterus lining thin
Thickens mucus at cervix to prevent sperm entering uterus
What is fertility?
The ability to conceive a child
What is a contraceptive
Method for preventing pregnancy
How do hormonal methods work?
Prevent fertilised egg implanting in uterus lining
How do barrier methods work
Stop sperm meeting egg
How can fertility be increased?
Hormones can be injected
Give 2 hormonal fertility drugs for women
FSH and LH
What does IVF stand for
In vitro fertilisation
True or false:IVF can happen in a lab without any beforehand treatment
False - hormone treatment with LH/FSH must be used
During IVF the best _____ embryos are selected using _____
1 or 2
Genetic screening (checking for genetic disorders)
How much can a single cycle of IVF cost?
£10 000 - 30 000
What is the success rate for IVF?
26%
Give the 6 stages of IVF
- Injection of hormones to stimulate egg maturation and release (FSH/LH)
- Eggs removed from ovary using fluid filled needle (ultrasound used to guide needle)
- Sperm from donor injected
- Fertilisation occurs
- Embryos develop
- Best embryo planted
What are extra embryos from IVF used for?
Embryonic stem cells
What is the human endocrine system?
Group of glands that secrete hormones directly into the blood
What is a gland?
And organ that secretes a hormone
What is a hormone
A chemical messenger that travels in the blood to target organs to bring about an effect
True or false: hormones are large proteins
True
What is the pituitary gland also called?
Master gland
Where is the pituitary gland situated
At the base of the brain
Where are the adrenal glands?
Above the kidneys
What does the ovaries produce
Oestrogen
What do the testes produce?
Testosterone
What do the adrenal glands produce?
Adrenaline
What does the pancreas produce?
Insulin
What does the thyroid gland produce?
Thyroxine
Where is the thyroid gland?
In the neck
Where is the pancreas
Above the kidneys
What else does the pancreas produce?
Glucagon
Give 3 things the thyroid gland controls
Metabolism
Weight
Energy
Give two parts of the CNS
Brain and spinal chord
What does the brain do
Controls complex behaviour
True or false: the brain has regions which carry out different functions
True
What is the brain made of?
Billions of interconnected neurones
What does the cerebral cortex do?
Controls consciousness
Memory
Language
Intelligence
Where is the cerebral cortex
The outer layer of the cerebrum
What does the cerebellum do?
Controls muscle coordination
How do you remember what the cerebellum does?
Llum sounds like run
What does the medulla do
Controls unconscious activities
How do you remember what the medulla does?
‘Me’ = unconscious me
Give 3 unconscious activities that the medulla controls
Breathing, heartbeat, blood pressure, sneezing, coughing
Give 3 methods of investigating the brain
Studying patients with brain damage
Electrical stimulation of parts of the brain
Using MRI scanning
How does studying patients with brain damage help to learn about the brain
Working out the area damaged and then linking this area to symptoms experienced by the patient
Hence working out what the area controls
How does stimulating the brain with electricity help to investigate the brain
Observing patients response to certain patterns of stimulation
How does MRI scanning help us learn about the brain?
Observing what areas of brain are active when talking, eating, recalling memories etc
What does MRi stand for
Magnetic resonance imaging
Give 3 advantages of investigating the brain
Successful treatments can be discovered and implemented
Symptoms reductions can be found following some procedures
Less need of other medications to manage systems following these procedures
Improvements to quality of life
Give 3 issues with investigating the brain
Side effects - risk of damage to patients
Many are invasive procedures which require the patient to be awake
Financial implications
Both for the patient and the NHS
Give a scientific issue with investigating the brain
Highly complex and delicate
Very small scale
What is the sclera?
Tough and strong outer layer to protect the eye and ensure it isn’t easily damaged
What colour is the sclera?
White
What is the cornea
Clear outer layer at the front of the eye
True or false: the cornea helps to focus light on the retina by refracting it slightly
True
What is the pupil?
A hole (made bigger or smaller by this iris)
What is the iris?
A muscle
What does the iris do?
Controls pupil size
How does iris control pupil size?
By contracting and relaxing (changing the amount of light allowed into the retina)
What is the retina?
Light sensitive receptor cells (stimulated by light/colour)
Area where the light is supposed to hit
What is the optic nerve?
Sends nervous impulses to the brain
Which then interprets these as a visual image
What is the lens and what does it do?
Fine tunes the focussing of light rays onto the retina
Lens held in place by ciliary muscles and suspensory ligaments
What is lens held in place by
Ciliary muscles and suspensory ligaments
Why does the iris reflex exist?
To prevent bright light damaging the retina
What are the two muscles of the iris?
Radial and circular
Describe the reflex arc of bright light to the reflex response
Light receptors in retina detect bright light
Circular muscles contract + radial muscles relax
Makes pupil smaller
Less light enters retina
Radial muscles contract or relax for bright light
Relax - go inwards to cover more
What happens to circular muscles when bright light?
Contract and cover more
What happens to circular muscles in dim light?
Relax - cover less
What happens when dim light?
Radial muscles contract - more light let in
When light hits retina _____ turn light into _____ signals
Photoreceptors
Electrical
Electrical signals are transmitted to the brain by the ____ nerve
Optic
What is accommodation
Changing the shape of the lens to focus on near or distant objects
Give the 2 ways the lens can be adjusted for accommodation
Ciliary muscles contract or relax and
Suspending ligaments slacken or stretch to adjust lens
What happens to ciliary muscles to focus on near objects?
Contract - move closer to the lens
What happens to suspensory ligaments to focus on near objects
Loosen to become longer and make lens thicker
Refraction increases or decreases for accommodation for near objects?
Increases - as lens thicker
To focus on distant objects ciliary muscles contract or relax?
Relax - moving further back from the lens
What happens to suspensory ligaments when focussing on distant objects
Tense - pulled tight
What happens to lens shape to focus on distant objects
Pulled tighter and thinner
Refraction is more or less for distant?
Less
How do you remember more refraction for closer and less refraction for further?
More refraction = less distance
Less refraction = more distance
(Opposite)
What does ciliary muscles relaxing and suspensory ligaments tensing do to the lens?
Ciliary muscles relaxing = pulls away from the lens
Suspenseful tensing = pulls the lens apart
When ciliary muscles contract suspensory ligaments do what?
Slacken
What is myopia?
Short sightedness
Does light focus before or after the retina in myopia
Before
Give 2 reasons for myopia
Lens is too thick
Eyeball is too long
What type of lens is used to correct myopia?
Concave lenses
Do concave lenses refract light less or more?
Less
Less refraction in concave lenses means light rays focus further forward or backwards?
Backwards
What is hyperopia
Long sightedness
With hyperopia you can’t focus on near/far objects
Near
Where does light focus (before or after retina) with hyperopia?
Focuses behind retina
Give 2 reasons for hyperopia
Eyeball too short
Lens too thin
What type of lens corrects for hyperopia
Convex lens
Convex lens increases or decrease refraction?
Increases
Increasing refraction with convex lens means light focuses further back or further forward
Forward
What is homeostasis?
Regulation of internal conditions of a cell or organism to maintain optimum conditions
(In response to internal and external changes)
Give 5 things the body regulates
Temperature
Water
Salts
Waste
Glucose
What is the optimum temp of human body
37.5 degrees
What is an example of a water product?
CO2
Where is glucose moved to and from
Blood to cells
What is the CNS?
Central nervous system
What is the CNS made up of?
Brain and spinal chord
What is the PNS?
Peripheral nervous system
What is the peripheral nervous system physically?
Nerves coming out of spinal chord
What is a stimulus?
Change in environment
What is a receptor?
Thing that detects a stimulus
What are the 5 sensory organs?
Skin
Nose
Eyes
Tongue
Ears
What does skin detect
Pressure, temperature, pain
What does the tongue detect?
Chemicals in food/drink
What does the nose detect
Chemicals
What do control centres do?
Receive and process information from receptors
What are effectors?
Muscles or glands which bring about a response to restore optimum conditions/levels of
What can effectors do?
Contract, release chemicals, secrete hormones
Give 3 adaptions of the nerve cell
Dendrites
Axon
Myelin sheath
Describe how dendrites are useful for the nerve cell
Create branched connections which increase surface area (forming a network)
What is the advantage of the axon for the nerve cell
Long body to cover more distance
How does the myelin sheath help the nerve cell
Insulation which lines the axon and speeds up electrical impulses
What is a synapse
Gap between neurones (all neurones have the synapse between)
How are electrical impulses transferred across neurones
Neurotransmitters diffuse across the gap (synapse)
What are the 3 stages of a reflex arc in terms of neurones
Sensory neurones
Relay neurones
Motor neurones
What are the stages of a reflex arc
Stimulus
Receptor
Sensory neurone
Relay neurone
Motor neurone
Effector
Response
Describe the reflex arc for eating food
Food
Sensory receptors in mouth
Sensory neurone
Relay neurone (pancreas)
Motor neurone
Salivary gland effector (releasing amylase)
Give 5 reflexes
Pupil dilation
Moving away from a source of pain
Knee jerk
Secretion of adrenaline in shock
What do reflexes help us to do
Respond quickly in dangerous situations
What is reaction time?
Time taken for an individual to respond to a stimulus
What is reaction time measured in
Milliseconds
Give 3 control variables for an investigation into reaction time
Caffeine intake
Alcohol/drug consumption
Amount of sleep/tiredness
Describe a method for a required practical about reaction time
Student A sits with elbow on a table edge - non dominant hand
Student B golds a ruler at 0cm, level with the thumb of student A
Student B drops it without warning
Student A catches it and records the distance in cm it has moved down
Repeats steps 1-4 and calculate mean
Compare mean to a conversion chart for redaction time
Why is non dominant hand used?
Less trained/more challenged (slower time, more likely to be accurate)
Why is ruler dropped without warning
Ensure not prepared
Why don’t we use a stopwatch of reaction time?
Time period too short
Adds another person’s reaction time to the results
Give another method of measuring reaction time
Computer program
Why is a computer program used
Higher resolution/more precise technique
What is an example of a computer program which can be used to measure reaction time
Pressing shapes when seen on a screen
How could you create an extra independent variable in this practical
Check caffeine/water/sugar intake and the difference it makes to reaction time
What effect is caffeine likely to have on reaction time
Increase reaction time
What is a tropism
Growth in a plant in response to a stimulus
Why do tropisms happen
To help a plant survive (like a human reflex)
What is an auxin?
Plant hormone that controls growth near tips of shoots and roots in response to stimuli
What is plant response to light called
Phototropism
Why do plants grow towards light
Maximise light absorption for photosynthesis
What does gravitropism do?
Ensure roots grow downwards
What is gravitropism?
Plant growth into response to gravity
What do tropisms happen as a response to?
The plant hormone auxin
Phototropisms happen due to ______ auxin distributions
Unequal
Auxins cluster on the ____side of the shoot
Shaded
Auxins cause the shoot to elongate/inhibits growth in shoots
Elongates
How do phototropism’s work?
Makes cells on shaded side longer
Pushes shoot towards sunny bit
Bends towards the light
In gravitropism, where do auxins go? (Upper or lower side of the root)
Lower side
Auxins have the ____ effect in the root compared to the ____ and ____ growth
Opposite
Shoot
Inhibit
How does gravitropism work?
Auxins accumulate on lower side of root
Top cells elongate more quickly
So root bends down towards gravity
What is negative gravitropism?
Root grows upward
Why might root grow upwards
To get more water
In negative gravitropism, auxins cluster on the upper/lower side of the root
Upper
How do negative gravitropisms work?
Auxins cluster on upper side
Inhibit growth on upper side
Lower side has more growth and so root curves upwards
What do gibberellins do?
Initiate seed germination, stem growth and flowering
What is ethene?
Gas produced by parts of the plant which are ageing
Give 2 things ethane controls?
Controls cell division
Controls ripening of fruits by stimulating enzymes
Give 3 ways auxins are used in agriculture/horticulture
Weed killers
Rooting powders
Promoting growth in a tissue
Give 3 ways gibberellins used
Ending seed dormancy
Promoting flowering
Increasing fruit size
How is ethene used in the food industry
Controls ripening of fruit during storage and transport
Give 4 commercial uses of plant hormones
Synchronised fruiting
Weed killing
Seedless fruit production
Cuttings
How do plant hormones help synchronised fruiting
Spraying hormones onto fruits makes them develop at the same rate
How does synchronised fruiting help the food industry
Efficient crop picking by machines
True or false: weed killing can be used to clear vegetation
True - this is how agent orange worked
How do plant hormones kill weeds?
Spraying with high concentrations of hormone upsets normal growth patterns
How can plant hormones allow for selective weed killing
As auxins affect different plant species differently
How do plant hormones help seedless fruit production
Hormone spray can make fruits develop without fertilisation (without fertilisation no seeds are formed)
True or false: plant hormones can reduce the plants dependence on pollinating insects
True
How are plant hormones used for cuttings and plant clonings
They can be stimulated to grow roots (hormone rooting powder)
What is the enquiry question of the tropisms required practical?
How does the light/direction of light affect plant growth
Give the independent variable in the tropisms required practical
Direction of light
Give the dependent variable in the tropisms required practical
Direction of plant growth/growth of plant
Give the 3 control variables in the tropisms required practical
Intensity of light
Type of plant
CO2 concentration
Give a method for the tropisms required practical
- Several seedlings in each batch and measure initial heights of shoots (with a piece of string or pull them straight and measure with a ruler)
- Leave some in a dark box with a small opening of light through a hole from the right side, one on the left, one with complete light from all sides, and one in the dark
- Ensure they are at the same temperature, given the same water and have the same soil type
- After 48 hours record the appearance of the seedlings (the direction they are facing by using a protractor to estimate the angle of bending
- Remeasure the shoot heights
Calculate the mean height increase for each group (by measuring 5 and taking an average)
Compare groups and the direction/amount by which they have grown
