Monocular vision

2. Monocular vision • Both eyes at the side of the head • The visual fields have little or no overlapping • Have wide field of vision • Usually among the prey (mangsa) • Helps to detect their enemies from a wide range of direction

3. Sound and hearing • Sounds are produced by vibrations • Sounds needs a medium to travel • Sounds can travel through solids, liquids and gases • Sounds cannot travel through a vacuum • Sounds can be reflected or absorbed • Hard and smooth surfaces are good reflectors of sounds • Soft and rough surfaces are good absorbers of sounds • Reflected sound is called echo

4. Defects of hearing • Involves the outer and middle ear - causes : wax blockage, punctured eardrum, birth defects, ear infections - the damage often temporary - can be treated medically or surgically • Involves the inner ear - causes : process of aging, bacterial infections, severe blow, exposure to loud sounds, tumour - receptors in cochlea are permenantly damaged - cannot be treated medically but can be corrected by using hearing aids

5. Stimuli and responses in plants • The plants response by growing in certain direction • Tropisms = growth responses • 3 main kinds of stimuli in plants: 1. water 2. gravity 3. light • Other stimuli : touch, temperature, chemicals

6. Common tropisms • Hydrotropism (water) - growth movement response to water - roots grow towards water (positive hydrotropism) • Geotropism (gravity) - growth movement response to gravity - roots always grow downwards (positive geotropism) - shoots grow upwards (negative geotropism)

7. Phototropism (light) - growth movement response to light - shoots are positively phototropic - roots are negatively phototropic • Thigmotropism (touch) - response to contact with a solid structure - climbing plants rely on the other objects to keep upright - cucumber & bitter gourd use tendrils to wrap around

8. Nastic movements (touch) - response to stimuli come from any direction - do not depend on the direction of stimuli - example : Mimosa pudicaand venus fly