Download Chap 6 Review - Emmanuel Biology 12

22 a
b
A tropism is a plant growth response to a specific stimulus such as light, touch or gravity.
Phototropism is a positive tropism, because plants respond towards the light source. Geotropism is a
negative tropism in shoots, because shoots move away from the force of gravity.
23 Auxin is produced by cells in the tip of a shoot. It promotes cell growth by softening the cell walls and
allowing turgor pressure to increase the size of the cell.
Light causes auxin to concentrate on the darker side of the shoot. Cells on the darker side of the shoot elongate
more than cells on the lighter side. This causes the shoot to grow unevenly, with the darker side growing faster
than the lighter side. The shoot bends towards the light.
24 Positive phototropism in the stem of a plant means that the stem grows upwards towards a light source.
25 a
Day length influences flowering in some plants. Short-day plants flower after they have experienced long
periods of darkness. Long-day plants flower after they have experienced short periods of darkness.
b
Long-day plants are more accurately described as short-night plants since it is the period of uninterrupted
darkness that controls flowering.
26 Geotropism is the response of a plant to gravity.
a
Roots are positively geotropic and move in the same direction as gravity.
b
Shoots are negatively geotropic and move away from the direction of gravity.
27 A vine coils around a trunk and grows up a tree under the influence of two stimuli. Thigmotropism is the
positive response of the plant to touch so that cells on the opposite side of the stem to the tree elongate and
move the stem around the tree. Phototropism is the positive response of the plant to light so that the plant
grows up towards the light source.
Chapter review questions
1
Activity of organism
Factor to which organism is
responding
Type of receptor
Male emperor gum moth detecting
presence of female moth
sex attractant molecules produced by
female moth
chemoreceptor
Pigeon navigating in overcast weather
changes in magnetic field of the Earth
magnetic
receptor
Platypus detecting yabbie prey
change in electric charge when the
yabbie flips its tail
electroreceptor
Increased breathing rate in a human
after strenuous exercise
carbon dioxide level of blood increases
chemoreceptor
Volvox moving towards light source
change in light intensity
photoreceptor
Pit viper detecting warm body of
mouse in its vicinity
change in infrared radiation in the
environment
thermoreceptor
Bat detecting location of insect by
echolocation
movement of insect
mechanoreceptor
2
Both are correct. The hormone system involves communication by chemical transmitters. The nervous system
involves the conduct of electrical signals as well as chemical transmitters across synapses.
3
Example: Multiple sclerosis
Multiple sclerosis is a disease of the nervous system that is characterised by inflammation of the myelin
sheath that surrounds neurons. This causes damage to the neurons, impairing their function so that
transmission of nerve impulses is interrupted or ceases altogether in some instances.
Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd)
35
Management strategies include:
Treatment with steroids and physiotherapy.
Diet modification, which may include avoidance of gluten and caffeine. Supplements of linoleic
acid (in sunflower oil) and primrose oil are sometimes given.
Regular but not too strenuous exercise is recommended to avoid muscle atrophy.
Avoid stressful situations.
Current research includes the development of pre-filled super-fine syringes for easier administration of
drugs and the development of immune-modulating drugs.
In severe cases patients may become wheelchair bound.
4
Hyperventilation causes a decrease in carbon dioxide concentration in the blood but no increase in oxygen
concentration, as the haemoglobin in red blood cells is usually saturated with oxygen. Breathing rate is
controlled by the detection of blood carbon dioxide concentration, so lowered blood carbon dioxide will
reduce breathing rate and the diver could run out of oxygen before experiencing the desire to breathe.
5
The pituitary gland is often called the master gland because of its role in regulating and coordinating other
endocrine glands.
6
Set up several coleoptiles, half with foil caps over their tips and half with no caps. Expose to a light source for
several hours. Observe coleoptiles after light exposure. Coleoptiles whose tips are exposed to light are
expected to show a growth response to the light source, while those with foil caps are not expected to show a
growth response to the light source.
Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd)
36
7
8
a
The natural conditions for tulips are simulated by placing the bulbs in cold storage for a period of time,
usually a couple of months, before planting. This simulates the extreme cold experienced in their native
European winter before spring growth and flowering.
b
Tulips are short-day plants—they require a period of exposure to long nights (short days) to initiate the
flowering response.
Substance X is produced or stored in amyloplasts in roots. It moves away from the direction of gravity, where
it promotes the growth of cells. These cells grow longer and the root turns towards gravity.
or
Auxins in the root promote the growth of root cells. Substance X moves in the direction of gravity and inhibits
cell growth so that cells grow downwards.
9
Fruits and vegetables that are transported long distances to reach our local supermarkets and marketplaces are
harvested before they are ripe. They are stored and transported in controlled atmospheric conditions in which
they are exposed to ethylene, the plant hormone responsible for ripening. When the levels of ethylene are
controlled over a period of time, the ripening process can be regulated so that produce arrives at its destination
in ripe, saleable condition.
Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd)
37