Aqa a level Biology - Topic 6 - survival and response questions and solutions

Aqa a level Biology - Topic 6 - survival and response
questions and solutions

What is a stimulus? - answersA change in the environment of an organism
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What is a tactic response? - answersDirectional movement in response to a stimulus
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What is a kinetic response? - answersNon directional random movement in response to a stimulus
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What is a positive and negative taxis? - answersPositive taxis- organism moves towards stimulus
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Negative taxis - organism moves away from stimulus wu wu wu wu wu wu wu




What Are receptors? - answersDetect stimuli- can be cells or proteins on cell surface membrane , loads of
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different types
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What are effectors? - answersCells that bring about a response to a stimulus to provide an effect ( muscle cells,
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glands)
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Receptors communicate with effectors via the ....... - answersNervous or hormonal system or both
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What are the 3 types of neurones? - answersSensory neurones
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Motor neurones wu wu




Relay neurones wu




What do sensory neurons do? - answersThey carry impulses from receptors to the CNS.
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What do motor neurones do? - answersTransmit electrical impulses from the central nervous system to the
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effectors
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What do relay neurones do? - answersTransmit electrical impulses between sensory neurones and motor
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neurones
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What is the order of nervous communication including neurones - answersStimulus > receptors > sensory
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neurones> CNS > motor neurone > effectors > response
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Outline nervous communication - answers- Stimulus detected by receptor cells and electrical impulse sent along
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sensory neurone
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- Electrical impulse reaches end of neurone ,neurotransmitters take info across synapse to the next neurone
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where another impulse is generated
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- the central nervous system processs info and sends impulses along motor neurones to effector
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Explain what neurotransmitters do - answersThey're chemical messengers secreted onto target cells creating a
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localised response which is rapid and short lived as they're quickly removed after they've done their job
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,What is a simple reflex? - answersRapid involuntary response to a stimulus, goes through spinal cord but not
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conscious part of the brain - they're protective a fast
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What is the reflex arc? - answersPathway of neurones linking receptors to effectors
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What is a tropism? - answersResponse of a plant to a directional stimulus
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What is a positive tropism? - answersGrowth towards the stimulus
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What is a negative tropism? - answersGrowth away from stimulus
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What is a phototropism? - answersGrowth of a plant in response to light
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Shoots are .................. phototropic and grow .................. light - answersPositively
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Towards

Roots are ............... phototropic and grow .................. from the light - answersNegatively
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Away

What is gravitropism? ( aka geotropism) - answersGrowth of a plant in response to gravity
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Shoots are ..................... gravitropic and grow ................ roots are ............... gravitropic and grow .............. -
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answersNegatively
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Upwards
Positively wu




Downwards

What are growth factors? And where are they produced? - answersHormone like chemicals in plants that speed
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up or slow down plant growth
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Produced in Growing regions of plant and move to where needed wu wu wu wu wu wu wu wu wu wu




What are auxins? - answersplant hormones - growth factors
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How do auxins work? - answersProduced in tips of shoots and diffuse backwards to stimulate the cell just behind
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the tips to elongate
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What is indoleacetic acid ( IAA) ? - answersAn auxin that is produced in the tips of shoots and roots
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Explain the movement and affects of indoleacetic acid in plants - answersMoves around to control tropism- moves
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by diffusion and active transport over short distances and via the phloem in long distances.
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This results in different concentrations leading to uneven growth,
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Root growth is ..................... by high concentrations of IAA . Shoot growth is ................ by high concentrations of
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IAA - answersInhibited
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Promoted

What is the resting potential? - answersThe potential difference ( or voltage) when a cell is at rest
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, When a nervous system receptor is in its testing state, the inside is .................. charged compared to the outside -
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answersNegatively
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What is a generator potential? - answersThe change in potential difference due to a stimulus
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A bigger stimulus excites the membrane more causing a bigger movement in ............ and a bigger change in
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............... ................. so a bigger .................. ....................... is produced - answersIons
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Potential difference wu wu




Generator potential wu




What is an action potential? - answersAn electrical impulse along a neurone triggered if the generator potential is
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big enough
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An action potential is only triggered if the generator potential reaches a certain level called............ -
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answersThreshold level
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Action potentials are all one size so the strength of the stimulus is measured by what? - answersThe frequency of
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action potentials
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What are pacinian corpuscles? - answersMechanoreceptors-detect mechanical stimuli such as pressure and
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vibrations
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What is a sensory nerve ending? - answersEnd of a sensory neurone and is wrapped in loads of connective tissue
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called lamellae
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Explain what happens when a pacinian corpuscle is stimulated - answersLamellae are deformed and press on
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sensory nerve ending, this causes s the neurones cell membrane to stretch which deforms the stretch mediated
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ion channels, channels open and sodium ions diffuse into cell creating generator potential
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What are photoreceptors? - answersReceptors in your eye that detect light
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Light enters the eye through the ................... - answersPupil
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The amount of light that enters the eye is controlled by the muscles of the ............. - answersIris
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Light rays are focused by the ............... onto the .................. which lines the inside of the eye - answersLens
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Retina

Photoreceptor cells are found in the ...... - answersRetina wu wu wu wu wu wu wu wu




The ................ is an area of the retina where there are lots of photoreceptors - answersFovea
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Nerve impulses from the photoreceptor cells are carried from the retina to the brain by the .................. -
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answersOptical nerve
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Where the optic nerve nerve leaves the eye is called the .................. there are no photoreceptors here -
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answersBlind spot
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