Suvival And Response Flashcards
What is a tropism
Growth movement of a part of a plant in response to directional stimulus
What does IAA stand for
Indoleacetic acid
What is IAA
a plant growth factor which controls cell elongation
Elongates cells in shoots
Inhibits elongation in roots
Phototropism
Response to light
Shoots positively phtototropic
Roots negatively phototropic
What is gravitropism
Growth response of a plant to gravity
Shoots negatively gravitropic so more likely to grow up where there is more sunlight
Roots positively gravitropic so grow down into ground to get mineral ions and water
What is thigmotropism
Climbing plants have a sense of touch, so will curl around objects they are touching
Allows plants to climb up and receive more light for photosynthesis
Tendrils are positively thigmatropic
Why does IAA have opposing effects in different cell types
Specialised cells express different genes so produce different proteins than each other
IAA interacts with different proteins differently
So has different effect based on the cell it’s in
what is a taxis
a simple response who’s direction is determined by the direction of the stimulus
what is a kinesis
a non-directional response to a stimulus which brings about increased random movements
what is a stimulus
a change in external or internal environment of an organism
what is the prefix for light
photo-
what is the prefix meaning gravity
geo-
what is the prefix meaning chemical
chemo-
what is the prefix meaning movement
Rheo-
what is orthokinesis
when a stimulus affects the speed of movement of an organism
what is klinokinesis
when stimulus affects how often an organism turns
why do organisms need to respond to external stimuli?
so they can increase their chance of survival by avoiding predation and abiotic stress, or increasing access to essential resources
why do organisms need to respond to internal stimuli?
to maintain stable internal conditions which are optimised for them to carry out chemical reactions (homeostasis)
