Chap 1.8 and 9
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Transcript of Chap 1.8 and 9
Topic 1.7Limitation of sight
Limitations of sight
There are basically 2 types of limitations of sighta) Blind spotb)Optical illusion
Blind spota) Occurs when image falls on the blind
spot of the eye
Pg 29 – blind spot test
Optical illusion
a) Occurs when our brain can’t interpret what we see accurately
Monocular and Stereoscopic Vision
Monocular Visiona)Vision involving one eye onlyb)Animals of prey usually have such vision
to detect the presence of predator easilyc)Has wider vision
Stereoscopic Vision
a)Vision involving two eyesb)Animals of predator usually have such
vision to enable them to estimate distance accurately
c)Can view objects in 3 dimension too
Distance finger test
Devices to overcome limitation of sight
Microscope
Magnifying glass
Binoculars
Telescope
PeriscopeUltrasound
X-ray
Topic 1.9Responses and
Stimuli in Plants
Why do shoot grows upwards and towards the sun while roots grow downward and towards water in soil?
shoot
root
stem
Why do climbing plants coil their tendrils around nearby objects?
tendrils
Tropic responses
Tropic responses are responses by plants towards stimulus and is dependent on the direction of stimulus.
4 types of tropic responses:a) Phototropism (light)b)Geotropism (gravity)c) Hydrptropism (water)d)Thigmotropism (touch)
Phototropism (light)
a) It is plants’ response towards lightb)Shoot shows positive phototropism
(move towards light)c) Root shows negative phototropism
(move away from light)d) It is to allow shoot to get more sunlight
for photosynthesis
Geotropism (gravity)
a) It is plants’ response towards gravityb)Shoot shows negative geotropism (move
upwards)c) Root shows positive geotropism (move
downwards)d) It is to allow root to get water and for
support
Hydrotropism (water)
a) It is plants’ response towards waterb)Shoot shows negative hydrotropism
(move away from water)c) Root shows positive hydrotropism (move
towards water)d) It is to allow root to get water
water in soil
Thigmotropism (touch)
a) It is plants’ response towards touch when in contact with objects
b)Take place in tendrils of plant when wrapping around the object
c) Stems and tendrils exhibit positive thigmotropism
d)Function is to reach a higher position to obtain sunlight. It also serves as support to plants
e) Usually in climbing plants
Nastic movements
Nastic movements are responses by plants towards stimulus and is not dependent on the direction of stimulus.
There are many stimuli that can cause nastic movements such as light (photonasty), touch (thigmonasty), temperature (thermonasty) etc.
Venus flytrap
Oxalis nastic movement
http://www.youtube.com/watch?v=ymnLpQNyI6g
http://www.youtube.com/watch?v=0V7_YT_RDh0
Stimuli and Responses in PlantsResponse Stimulus Root response Shoot response Function
Phototropism Light Negative Positive Obtain light
Geotropism Gravity Positive Negative Obtain water and mineral salts
Hydrotropism Water Positive Negative Obtain water and mineral salts
Thigmotropism Touch - - Obtain protection, support & light
Nastic movement does not depend on the direction of stimulus. Examples of plant with nastic movement are mimosa pudica and Venus flytrap.