t6 response

Question 1

tropism definition

Answer 1

growth of a part of a plant in response to a directional stimulus - can be positive or negative causing the plant to grow towards or away from the stimulus

Question 2

what is indoleacetic acid (IAA)

Answer 2

-type of auxin synthesised at the tips of roots
-controls the elongation at the meristem (causing one side of a plant to grow faster and so bend towards light)

Question 3

taxis definition

Answer 3

directional response to a stimulus by an organism

Question 4

kinesis definition

Answer 4

non-directional response to a stimulus by an organism
-rate of movement is affected by intensity of stimulus
-movement is in random directions to increase the change the organism will enter more favourable conditions faster

Question 5

reflex arc pathway

Answer 5

1. stimulus
2. receptor
3. sensory neurone
4. relay neurone
5. motor neurone
6. effector
7. response

Question 6

pacinian corpuscle - function

Answer 6

-type of receptor found deep in the skin that responds to changes in pressure
-found in the skin of the fingers, soles of the feet

Question 7

pacinian corpuscle - structure

Answer 7

-found at the end of sensory neurone axons
-made of many layers of membrane separated by a gel which contains many positively charged sodium ions
-the section of axon surrounded by layers of membrane contains stretch-mediated sodium ion channels which open when sufficient pressure is applied

Question 8

type of pigment rod cells contian

Answer 8

rhodopsin
-breaks down in dim light

Question 9

type of pigment cone cells contain

Answer 9

iodopsin
-breaks down in bright light only

Question 10

features of rod cells

Answer 10

-very sensitive to low light intensity
-poor visual acuity (multiple rod cells synapse with a single bipolar cell)
-concentrated at the periphery of the retina, absent at the fovea
-only one type
-contain rhodopsin
-many more than cone cells (roughly 125 million/eye)