chapter 14 exam questions Flashcards
figure 1 shows an investigation into growth factors in plants.
use your knowledge of IAA to explain the growth of curvature shown in figure 1 (3)
-IAA produced in tip of shoots
-IAA diffuses
-more elongation on one side than another
give one similarity and one difference between a taxis and a tropism (2)
similarity- both are a directional response to a stimulus
difference- in taxis, the whole organism moves
tropism is a growth response
exercise causes an increase in heart rate. describe the role of receptors and the nervous system in this process. (4)
-chemoreceptors detect rise in CO2
-impulses sent to medulla
-more impulses to SAN
-by parasympathetic
When the heart beats, both ventricles contract at the same time.
Explain how this is coordinated in the heart after initiation of the heartbeat
by the SAN (2)
-wave of electrical activity only passes through bundle of his
-wave of electrical activity passes through both ventricles at the same time.
The fovea of the eye of an eagle has a high density of cones. An eagle
focuses the image of its prey onto the fovea.
Explain how the fovea enables an eagle to see its prey in detail.
Do not refer to colour vision in your answer. (3)
-one cone cell is connected to a single bipolar cell
-high visual acuity
-sends separate impulses to the brain.
The retina of an owl has a high density of rod cells.
Explain how this enables an owl to hunt its prey at night.
Do not refer to rhodopsin in your answer. (3)
-retinal convergence
-several rods connected to single neurone/bipolar cell
-enough neurotransmitter to overcome threshold.
) Explain how the resting potential of –70 mV is maintained in the sensory
neurone when no pressure is applied. (2)
membrane is more permeable to potassium ions and less permeable to sodium ions
sodium ions actively transported out and potassium ions in.
Explain how applying pressure to the Pacinian corpuscle produces the
changes in membrane potential recorded by microelectrode P. (3)
-membrane becomes deformed/stretched
-sodium ion cahnnels open and sodium ions move in
-greater pressure- more channels open
The membrane potential at Q was the same whether medium or heavy
pressure was applied to the finger tip. Explain why (2)
all or nothing principle
if threshold reached- maximal response
Multiple sclerosis is a disease in which parts of the myelin sheaths
surrounding neurones are destroyed. Explain how this results in slower
responses to stimuli (2)
no saltatory conduction
-impulses can’t jump from node to node
-more depolarisation over length.
Figure 1 shows an investigation into growth factors in plants.
Figure 1
(a) Use your knowledge of indoleacetic acid (IAA) to explain the growth
curvature shown in Figure 1 (3)
-tip produces IAA
-IAA diffuses
-more elongation on one side than another.
Using the procedure in Figure 2 and the calibration curve in Figure 3,
describe how you could compare the IAA concentration in shoot tips from
two different plant species.
In your answer you should refer to all the variables that should be
controlled to produce a valid comparison. (5)
-size of agar blocks
-time shoots are left in the dark for
-temperature
-repeat and calculate an average
-read degree of curvature to find IAA concentration.
Read the following passage.
Complete achromatopsia is a form of complete colour blindness. It is caused
by having only rods and no functional cone cells. People with complete
achromatopsia have difficulty in seeing detail. Complete achromatopsia is
caused by an autosomal recessive allele and is usually very rare in
populations with only one in 40 000 being affected. However on the Pacific 5
island of Pingelap ten percent of the population are affected.
One form of red-green colour blindness is caused by a sex-linked recessive
allele which affects more men than women. People with this red-green
colour blindness are unable to distinguish between red and green, and also
between other colours. They have green-sensitive cones but the 10
photoreceptive pigment they contain does not function.
Scientists investigated the use of gene therapy to correct red-green colour
blindness in monkeys. They injected viruses containing the gene for the
green-sensitive pigment directly into the eyes of the monkeys. Although the
monkeys maintained two years of colour vision, there is debate on whether 15
this form of gene therapy is worthwhile. No clinical trials of this procedure
have been carried out on humans. Current research into the treatment of
red-green colour blindness involves the use of induced pluripotent stem cells
(iPS cells). The use of iPS cells could have advantages over the use of gene
therapy. 20
Use the information in the passage and your own knowledge to answer the following questions.
(a) People with complete achromatopsia have difficulty in seeing detail (lines 2–3).
Explain why.
(3)
-no cone cells
-one cone cell connected to a single bipolar cell
-sends separate impulses to the brain
Red-green colour blindness affects more men than women (lines 7–8). (2)
-on the X chromosome
women need two alleles
) People with red-green colour blindness are unable to distinguish between red and green, and also between other colours (lines 8–10).
Explain why
(3)
-green sensitive cones not functional
3 different types of cones
different colours seen due to stimulation of more than one cone
