Plant and Animal Responses

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How does a plant prevent freezing?
They produce more sugars, polysaccharides and proteins which act as antifreeze.
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What three substances are produced as chemical defenses in response to herbivory?
Tannins, alkaloids and pheremones
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Define the term 'thigmonastic'
The movement or growth of an organism in a particular direction in response to contact with a solid object.
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Describe the mechanism of the thigmonastic response produced by mimosa pudica?
The movement of potassium ions into/out of specific cells causes water to follow by osmosis causing the leaves to collapse and fold down
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What is a tropism?
The directional growth of part of a plant in response to an external stimulus
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In an experiment to assess the effect of geotropism how is the force of gravity removed for the control plant?
The plant is spun very slowly in a machine called a climostat to ensure that gravity is applied equally
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Describe how ethene stimulated leaf abscission.
Ethene increases the production of cellulase which hydrolyses cellulose at the abscission zone and separates the leaf from the stem.
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What are the key limitations of plants?
They aren't mobile as they're rooted. They don't have a rapidly respnding nervous system so their responses are slower.
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How do hormones travel throughout the plant?
They can travel by active transport, difusion or by mass flow in the xylem or phloem
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What does gibberellin stimulate?
seed germination, stem elongation, side-shoot formation, flowering
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How do auxins stimulate growth in plants?
They stimulate cell elongation. cell walls become loose and stretchy so the cells can get longer
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What pigment is responsible for a plants sensitivity to day length?
Phytochrome
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During leaf abscission, why is fatty material deposited in the cells on the stem side of the separation layer?
To form a protective scar, when the leaf falls to prevent the entry of pathogens
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What is the sypathetic nervous system?
The division of the autonomic nervous system involved in 'fight or flight' responses. it prepares the body for action with the neurotransmitter noradrenaline
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Which neurotransmitter does the parasympathetic nervous system use?
acetylcholine
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Where does a reflex pathway travel to?
The spinal cord or the unconscious part of the brain
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What is the function of the cerebellum?
controlling muscle coordination, posture and coordination of balance
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What is the function of the medulla oblongata?
automatically controls breathing rate and heart rate
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What is the function of the cerebrum?
Involved in higher brain functions namely, conscious thought, consciuous actions, emotional responses, intelligence, reasoning, jugement, desicion making, factual memory
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Describe the 'fight or flight' response.
1)threat perceived by cerebrum, which stimulates hypothalamus 2)hypothalmus stimulates sympathetic nervous system 3)SNS stimulates organs inc. adrenal glands 4)adrenaline+noradrenaline secreted by adrenal medulla into blood+bind to receptors
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What happens when the hypothalamus releases Corticotropin-releasing hormone (CRH)?
Adrenocorticotropic hormone (ACTH) is released. This stimulates hormones such as cortisol to be released cortisol regulates the metabolism of carbs (glycogen to glucose)
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Why are endorphins released as part of the 'fight or flight' response?
They act as natural painkillers, so if the organism is injured this wont prevent further action
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Why do the number of white blood cells increase as part of the fight or flight response?
They would be used to destroy pathogens in the event that you were injured
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What is the range for an average resting heart beat?
Between 60 and 80 bpm
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What is another name for the sinoatrial node?
The pace maker of the heart
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What does the parasympathetic nerve do?
Decrease the heart rate
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What does sypathetic nerve do?
Increase the heart rate
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What is another name for the parasympathetic nerve?
the vagus nerve
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What is another name for the sympathetic nerve?
The accelerator nerve
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Which part of the brain controls heart rate by neuronal control?
The cardiovascular centre in the medulla oblongata
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Where is the carotid artery?
In the neck
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What effect does adrenaline have on the heart?
1) inc heart rate 2) inc stroke volume 3) inc cardiac output
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What does it mean to say that cardiac muscle is myogenic?
It contracts without the need for nervous stimulation
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What are the 3 main features of smooth muscle?
Cells are irregularly arranged, can contract in different directions/ contraction speed is slow, remain contracted for a long time/ muscles are non-striated
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Describe skeletal muscle fibres
tubular and multinucleated
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How are skeletal muscles attached to the tendons?
by tendons
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What happens to a muscle fibre during development?
The cells fuse to form a very long strong multinucleated cell that can withstand very high tension
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What is a sarcomere?
The smallest contractile units in a muscle. They are arranged end-to-end for the entire length of each myofibril
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What type of protein in actin made from?
Globular proteins
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What type of protein is myosin made from?
fibrous proteins
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Which band in a myofibril always the same length no matter if the muscle is contracting or relaxing?
The A band
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What is creatine phosphate?
A chemical that phosphorylates ADP to ATP, maintaining the muscles supply of ATP during vigorous exercise.
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What two other proteins are attached to actin fibres and what are their structures?
Tropomyosin is wound around the actin. Tropanin molecules are bound to the tropomyosin
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which neurotransmitter are receptors on the sarcolemma specific to?
Acetylcholine
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Where does the wave of depolarisation travel after it passes along the sarcolemma?
Down T-tubules
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What does the wave of depolarisation at a neuromuscular junction trigger?
The release of calcium ions (Ca2+) from the sarcoplasmic reticulum. This initiates muscle contraction.
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Why can't myosin heads bind to actin in a relaxed muscle?
Because tropomyosin blocks the binding sites on the actin filament
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How are the actin binding sites exposed?
A high concentration of calcium ions causes the tropomyosin to chnage shape exposing them.
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What happens once the myosin head binds with the actin?
Once binded the myosin head changes shape causing the entire myosin filament to be pulled along the actin. ADP can now be released by the myosin head
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Why is ATP required for muscle contraction?
To enable the myosin head to release the actin and return to its original state
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How does tropomyosin return to its original shape?
Calcium is actively removed from the sarcoplam when the muscle is no longer stimulated by a nerve, causing tropomyosin to return to its original shape
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How are bridges between actin and myosin pulled apart?
By antagonistic muscle action.
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Other cards in this set

Card 2

Front

What three substances are produced as chemical defenses in response to herbivory?

Back

Tannins, alkaloids and pheremones

Card 3

Front

Define the term 'thigmonastic'

Back

Preview of the front of card 3

Card 4

Front

Describe the mechanism of the thigmonastic response produced by mimosa pudica?

Back

Preview of the front of card 4

Card 5

Front

What is a tropism?

Back

Preview of the front of card 5
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