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Movement
Mechanisms and Roles
Movement in Plants and Animals Syllabus Objectives
Use examples to distinguish between growth movement in plants and movements in animals
Discuss the importance of locomotion in animals
Movement in Plants and Animals Movement is a characteristic of all living
organisms It is a reaction to external or environmental
stimuli It involves either part of the organism or the
entire organism (as in most animals) The direction of the stimuli determines the
direction of the response
Movement in Plants and Animals cont’d Locomotion is the movement of the entire
organism from one place to another
QUESTION Based on the definition of locomotion, do plants and
animals exhibit locomotion?
Movement in Plants and Animals cont’d Part movement in plants is a result of growth
as a response to various stimuli.
QUESTION Can you think of what stimuli plants respond to?
Growth responses in plants are usually slow and are irreversible
Movement in Plants and Animals cont’d Movement in animals is usually faster than
growth in plants. Movement in animals takes place in
response to a stimulus (much like growth movement in plants)
These movements are however reversible The organism or its part can return to its original
position when the stimulus is removed
Movement in Plants and Animals cont’d Movement is important for the survival of all
organisms
QUESTION List the reasons why movement is important to animals
Finding food, finding a mate, escaping from predators, finding a more favourable environment
These responses ensure that animals survive long enough to produce new offspring
External Factors and Plant Movement Syllabus Objective
Perform simple investigations to show how external factors affect plant movement
External Factors and Plant Movement Growing plants respond to stimuli such as
light and gravity. Movement towards a stimulus is a positive
response Movement away from a stimulus is a negative
response If a stimulus is applied from one direction, the
response is usually in one direction away from or toward the direction of the stimulus
External Factors and Plant Movement cont’d The stimulus is received by the tip of the
shoot or root The growth response takes place just behind
the tip E.g. plant shoots will grow toward a light source.
External Factors and Plant Movement cont’d Plant hormones called auxins are made at
the tips of roots and shoots Auxins diffuse downwards and away from the
light source Cells in the region where auxins accumulate
grow faster than other cells causing bending in that region
External Factors and Plant Movement cont’d Different parts of the same plant may
respond differently to the same stimulus Shoots respond positively to light Roots respond negatively to light
QUESTION Why would shoots respond to light positively? Why would roots respond to light negatively?
External Factors and Plant Movement cont’d For Shoots
Light is essential for photosynthesis Light is important for chlorophyll formation
For Roots Light is not essential to root development or
growth
External Factors and Plant Movement cont’d Gravity
Shoots respond negatively to gravity Roots respond positively to gravity
This response ensures that the root becomes firmly anchored in the soil and is able to obtain water and nutrients
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