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Receptors
Photoreceptors-detecting lights + e
...

Response: behaviour of a living organism due
to a stimulus that increases chance of survival
...
It
controls the
specific stimuli
and receptor to
use
...
They can be positive(towards a stimulus)
or negative(away from the stimulus) and respond to
a variety of stimuli
...
Cells in the tip produce IAA, and it is transported
down the shoot due to gravity
...
IAA is transported equally throughout the shoot
3
...
IAA builds up in the shaded side which causes
elongation of the cells in the shaded side
5
...


Gravitropism in flowering plants

1
...
Bacteria move away from waste material they produce: negative
chemotaxis

 photosynthesis
4
...


TOWARDS
Favourable stimuli
POSITIVE TAXIS

AWAY FROM
unfavourable stimuli
NEGATIVE TAXIS

Examples of taxes:



3
...
Bacteria move toward glucose: positive chemotaxis
respiratory substrate

 get

Sensory
neurone

Schwann
cell

A chemical substance(the receptor to light) had
diffused from the shoot tip into the agar, and that
this substance stimulated growth further down the
shoot
...
Also he
concluded that the greater amount of auxin, the
greater the bending
...
Cells on the tip of root produce IAA, and is
transported along the root
...
Gravity causes IAA to move from upper to lower
side of the root
...
More IAA is produced on the lower side of the
root
...
IAA inhibits the elongation of cells on the lower
side, so more elongation occurs on the upper side
5
...


Lamellae

Often the rate of movement is indicative of the
stimulus intensity
...

Where the speed of movement is altered it is
orthokinesis
Where the rate of turning is altered is is klinokinesis
Woodlice in light, warm, dry environment may move
faster and in straighter lines (turn less) thus covering
a greater distance and are more likely to leave the
less favourable environment
...
They
detect a change in pressure and vibrations
...
This allows sodium to
diffuse into the axon, which causes an action potential
...

The detection of light is carried out by photoreceptor cells
in the retina
...
They form sy

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