FORM 2 CHAPTER 1

Sensory organs:

Skin:

·                     sense of touch

·                     Stimuli : hot, cold, pain, pressure, touch

Nose:

·                     sense of smell

·                     Stimuli : Chemical substance in the air

Tongue:

·                     Sense of taste

·                     Stimuli:Chemical substance in the food

Ear:

·                     sense of hearing

·                     Stimuli: sound

Eye:

·                     sense of sight

·                     Stimuli: light

Properties of light:

·                     light can be reflected and refracted

Defects of vision:

1.             long sighted

·                     Can see far objects clearly

·                     Image formed behind retina

·                     Causes:

-                      eyeball too small/short

-                      lens too thin

·                     correction – Use convex lens

1.             short sighted

·                     can see near objects clearly

·                     image formed in front of retina

·                     causes:

-                      eye ball too big/long

-                      Lens too thick

·                     correction – use concave lens

Properties of sound:

·                     is a form of energy

·                     produced by vibrating objects

·                     travels in the form of waves

·                     can be reflected (echo)

·                     can be absorbed

·                     can only travel through medium

·                     cannot travel through vacuum

Stimuli and responses in plants:

Phototropism:

·                     Stimuli – Light

·                     Response to obtain sunlight

Geotropism:

·                     Stimuli – gravity

·                     Response to root itself firmly in the soil/to obtain mineral salts and water

Hydrotropism:

·                     stimuli – water

·                     Response to obtain water and mineral salts

Thigmotropism:

·                     Stimuli – touch

Response to obtain support and light