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In what three ways may plants respond to changes in daylight hours ?
breaking the dormancy of the lateral leaf buds , so they open up and grow new leaves timing the flowering in a plant preparation of tuber formation leaf abscission , causing leaves to fall
How do plants respond to a decrease in temperature ?
Producing sugars , polysaccharides and proteins which act as antifreeze . Supressing or activating different genes at sustained low temperatures .
How do plants respond to a lack of water ?
They close their stomata to prevent water loss by transpiration .
What is herbivory ?
When plants are eaten by a herbivore .
What are the three chemical defences to herbivory ?
Tannins , alkaloids , pheromones .
What are tannins ?
Chemicals that have a bitter taste which puts animals off eating the leaves they are toxic to insects as they inactivate their digestive enzymes .
What are alkaloids ?
Bitter tasting nitrogenous compounds that affect the metabolism of animals ( often protein synthesis is inhibited ) .
What are pheromones ?
Chemicals that affect the behaviour and physiology of another organism .
Which plant folds in respond to touch ?
Mimosa pudica
What is the name for movement in response to touch ?
Thigmonastic movement
How does the mimosa plant bring about the response to touch ?
By movement of potassium ions into / out of specific cells and then movement of water by osmosis into / out of cells , causing a change of shape of the cells .
What is a tropism ?
The directional growth of part of a plant in response to an external stimulus .
What is the name for a tropism in response to light ?
Phototropism
What is the name for a tropism in response to gravity ?
Geotropism
Which two types of tropisms would shoots perform ?
Positive phototropism Negative geotropism
What is apical dominance ?
When the growth of the main central stem ( the apex of the plant ) inhibits the growth of the lateral shoots / branches .
Which hormone causes apical dominance ?
Auxin
Give one example of experimental evidence that shows that auxin causes apical dominance .
If the apical bud / apex is pruned , the lateral shoots / branches begin to grow .
Which hormone causes stem elongation ?
Gibberellins
How is stem elongation caused ?
The individual cells elongate and cell division means there are also more cells .
Give one example of experimental evidence that shows that gibberellins cause stem elongation .
When gibberellins are applied artificially to dwarf plants , they can stimulate stem elongation , even in genetically determined dwarfism .
Which hormones causes seed germination ?
Gibberellins
How do hormones cause seed germination ?
Gibberellins stimulate the production of amylase and protease that break down the food stores found in the seed . The embryo plant uses these food stores to produce ATP for building materials so it can grow and break out of the seed coat .
Give one example of experimental evidence that shows that gibberellins cause seed germination .
Mutant varieties of seeds which do not have the gene to allow the production of gibberellins , do not germinate . However if gibberellins are applied to these seeds externally , they will germinate normally .
Which hormone causes stomatal closure ?
Abscisic acid ( ABA )
How stomatal closure caused ?
The abscisic acid activates changes in the ionic concentration of the guard cells , increasing the water potential , so water moves out of the cells and they become flaccid . This causes the guard cells to close .
Which hormone causes leaf abscission ?
Ethene
How is leaf abscission caused ?
Ethene increases the production of cellulase , which hydrolyses cellulose at the abscission zone and separates the leaf from the stem .
Which hormone is used to control fruit ripening ?
Ethene
How are hormones used in fruit ripening ?
1. Fruit are picked unripe , transported and then exposed to ethene to ripen them ready to be sold . 2. Fruit it exposed to ethene on the plant to ensure they all ripen at the same time .
Which hormone can be used to prevent fruit from dropping ?
Auxin ( or gibberellin for citrus fruit )
Which hormones can be used to encourage fruit to drop ?
Ethene
Which hormone can be used as a rooting powder ?
Auxin
What does a rooting powder and when is it used ?
It encourages the growth of roots and is used during artificially cloning e.g. when taking cuttings .
What is a herbicide ?
A substance that kills plants .
Which hormone can be used as a weed killer ?
Auxin ( synthetic )
Which hormone is used to encourage flowering plants to grow multiple lateral shoots and therefore produce more flowers ?
Ethene
Which hormone used to encourage fruit growth ?
Gibberellins
What are the two main branches of the nervous system ?
Central nervous system Peripheral nervous system
What are the two parts of the central nervous system ?
Brain and spinal cord
Which type of neurone is found in the central nervous system ?
Intermediate / relay neurones
Which types of neurone are found in the peripheral nervous system ?
Sensory and motor neurones
What are the two branches of the peripheral nervous system ?
Somatic and autonomic
What does the somatic nervous system control ?
Conscious activities
What does the autonomic nervous system control ?
Unconscious activities
What are the two branches of the autonomic nervous system ?
Sympathetic and parasympathetic
Which specific branch of the nervous system is involved in fight or flight ' responses ?
Sympathetic
Which specific branch of the nervous system is involved in ' rest or digest ' responses ?
Parasympathetic
Which neurotransmitter is used in the sympathetic nervous system ?
Noradrenaline
Which neurotransmitter is used in the parasympathetic nervous system ?
Acetylcholine
List 5 physiological reactions that are under sympathetic control .
Heart rate increases Pupils dilate Bronchi dilate Digestive activity is inhibited Glycogen converted to glucose in the liver Adrenaline released Peristalsis inhibited
List 5 physiological reactions that are under parasympathetic control .
Heart rate decreases Pupils constrict Bronchi constrict Digestive activity is stimulated Glucose is converted to glycogen in the liver Adrenaline release inhibited Peristalsis stimulated
What is a reflex action ?
Where the body responds to a ( often dangerous or threatening ) stimulus without making a conscious decision .
What are 3 key features of reflex actions ?
1. Automatic 2. Rapid 3. Innate ( not learnt )
Why are reflex actions quicker than other actions ?
They only involve 3 neurones , other actions travel through more neurones . They travel to the closest part of the CNS and back again - this is either the spinal cord or the unconscious part of the brain .
What is the function of reflex actions ?
To prevent injury / damage to the body .
List , in order , the 7 stages to a reflex arc pathway .
Stimulus ->Receptor → Sensory neurone → Intermediate / relay neurone → Motor neurone → Effector -> Response
In the blink reflex , what is the stimulus ?
An object moving towards / touching the eye or wind blow into the eye .
the blink reflex , where are the receptors ?
In the cornea of the eye
In the blink reflex , where are the intermediate neurones located ?
In the pons of the brain , in the central nervous system .
In the blink reflex , what response is caused ?
Muscles connected to the eyelids contract to close the eyelids .
In the knee jerk reflex , what is the stimulus ?
The quadriceps muscle is stretched due to an object hitting the muscle .
In the knee jerk reflex , where are the receptors ?
In the quadriceps muscle .
In the knee jerk reflex , where are the intermediate neurones located ?
The spinal cord
In the knee jerk reflex , what response is caused ?
The quadriceps muscle contracts and the lower leg moves forwards .
Name the six main parts of the brain .
- Cerebrum / cerebral cortex - Cerebellum - Corpus callosum - Medulla oblongata - Pituitary gland - Hypothalamus
Which part of the brain coordinates the autonomic control of heart rate ?
Medulla oblongata
Which part of the brain coordinates clapping of the hands ?
Cerebrum
Which part of the brain coordinates osmoregulation by the kidney ?
Hypothalamus
Which part of the brain coordinates balance when riding a bike ?
Cerebellum
Which part of the brain coordinates the muscles involved in an adult walking ?
Cerebrum
Which part of the brain coordinates the reflex of vomiting ?
Medulla oblongata
Which part of the brain coordinates the muscles required to deliberately bend the elbow ?
Cerebrum
Which part of the brain coordinates speech ?
Cerebrum
Which part of the brain coordinates thermoregulation ?
Hypothalamus
Which part of the brain coordinates posture ?
Cerebellum
Which part of the brain releases hormones ?
Pituitary gland
What is fight or flight ?
An instinct that all mammals possess . It is intended to help mammals to survive by preparing the body to either run / escape or fight for their life .
Which two organ systems coordinate the fight or flight responses ?
The endocrine and nervous systems
Which part of the brain receives information about the threat in the environment ?
The cerebrum
Which part of the brain is stimulated by the cerebrum to then coordinate the response ?
The hypothalamus
Which branch of the nervous system is stimulated by the hypothalamus ?
The sympathetic nervous system
What affect does the sympathetic nervous system have on the adrenal glands ?
Causes it to release adrenaline ( a hormone ) and noradrenaline ( a neurotransmitter ) form the adrenal medulla .
Which hormone is released as a result of corticotropin - releasing hormone ( CRH ) and adrenocorticotropic hormone ( ACTH ) being released from the brain ?
Cortisol
Which hormone is released as a result of thyrotropin- releasing hormone ( TRH ) and thyroid - stimulating hormone ( TSH ) being released for the brain ?
Thyroxine
What is the role of cortisol ?
It leads to the breakdown of glycogen to glucose so there is more glucose for respiration .
What is the role of thyroxine ?
It increases cell metabolism and increases the cells ' sensitivity to adrenaline .
Which fight or flight responses are linked to cardiac muscle ?
Heart beats faster Heart beats more forcefully
Which fight or flight responses are linked to voluntary ( skeletal ) muscle ?
. Breathing is faster . Greater blood flow to the skeletal muscles . Muscles are primed for action e.g. leg muscles to run away
Which fight or flight responses are linked to involuntary ( smooth ) muscle ?
. Increased blood pressure . Less blood flow to the gut and skin . Skin becomes pale Peristalsis slows down . Airways widen . Pupils dilate
The heart is myogenic , what does this mean ?
It has electrical impulses that originate in the muscle .
Which part of the heart is known as the pacemaker ?
The SAN ( sino - atrial node )
Which two organ systems affect the heart rate ?
Endocrine and nervous systems
Which specific part of the brain affects the heart rate ?
The cardiovascular centre in the medulla oblongata .
Where are the receptors that detect changes in the blood and from which information is to the brain ?
The aorta and carotid artery
What do baroreceptors / stretch receptors detect ?
Changes in blood pressure
What do chemoreceptors detect ?
Changes in pH in the blood ( concentration of carbon . dioxide )
Which nerve is used to send an impulse from the medulla oblongata to the SAN to decrease the heart rate ?
The vagus / parasympathetic nerve
Which nerve is used to send an impulse from the medulla oblongata to the SAN to increase the heart rate ?
The accelerator / sympathetic nerve
What 3 effects does adrenaline have on the functioning of the heart ?
. Increased heart rate • Increased stroke volume . • Increased cardiac output
