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