survival and response Flashcards
what is a tropism
directional growth response to stimulus in plants
what is phototropism
directional response to sunlight
shoot grows towards light (positive) and roots grow away from light (negative)
what is gravitropism
directional response to gravity
shoots grow away from gravity (negative) and roots grow towards gravity (positive)
what are growth factors
enable plants to respond their environment
where are growth factors found
parts of the plant that are actively dividing and diffuse to other parts of the plant when needed
what is indoleacetic acid (IAA)?
a type of auxin which allows plants to respond to light and gravity
what is the mechanism of IAA
enters the nucleus of plant cells
binds to promoter region of DNA, acting as transcription factor
activates / inhibits transcription genes that code for proteins involved in cell elongation and growth
how does IAA move around the plant
in the phloem
moves shorter distances by diffusion and active transport
how does phototropism occur in the shoots
IAA accumulates on the shaded part of shoot
activates genes involved in cell elongation
transcribed into proteins which make the cell walls looser
how does phototropism occur in roots
IAA accumulates on the shaded side
inhibits the growth of cells
cells produced on non-shaded side of root
root bends away from the sun
how does gravitropism work in roots
IAA accumulates on the lower side due to gravity
high IAA inhibits elongation in roots
upper side to grow faster, making the root bend downwards
what are taxis and kineses
behavioural responses in simple organisms that improve survival
what are taxis
directional movement
what are positive taxis
movement stimulus
what are negative taxis
movement away from stimulus
what are kineses
non directional movement
describe kineses
changing kinetic rate and speed dependent on intensity of stimulus
faster movement, less turning in unfavourable conditions (leave)
/
slower movement, more turning in favourable conditions (stay)
what are the parts of the nervous system
CNS - central nervous system
PNS - peripheral nervous system
what are the types of neuron
sensory
relay
motor
how do neurones stimulate target cells
they pass electrical impulses along their length and secrete chemical neurotransmitters directly onto them
how would you describe reflexes
rapid, short-lived, localised response
describe the points of the reflex arc
stimulus → receptor → sensory neurone → relay neurone (CNS) → motor neurone → effector → response
