Support And Movement
In this chapter you will learn:
- Importance of support, movement and locomotion.
- Identification, description and microscopic examination of supporting tissue of young and woody dicotyledonous stem.
- Definitions of tactic, nastic, tropic movements; three types of tropism (geotropism, phototropism and h
ydrotropism) in plants.
- Importance of tropic response and explanation of geotropism in root and phototropism in shoot in terms of auxins.
- Locomotion in plants (Euglena and Volvox and in animals (amoeba and paramecium).
- Two types of skeleton (axial and appendicular). And their function in support and movement.
- Role of muscles in the support of skeleton: their movements (action of flexors and extensors) and functions of tendons and ligaments in relation to movements.
- Defects of skeletal system; joints (ball and socket and hinge) their function and dislocation.
14.1 Support, Movement and locomotion
The need for support became greater as animals and plants increased in size through process of evolution. This was particularly true for organisms which left the water and colonized land. Support in different organisms may be provided by:
- Skeleton as in man and other animals.
- Mechanical tissues in woody parts of plants
- Turgidity of parenchymatous tissues in non-woody parts of plant which remain firm and erect because of the pressure within these cells.
During period of water shortage, the tissues of such plants lose water and it results in wilting. Similarly bodies of animals would collapse and fail to maintain shape and posture, if they are not supported properly.
Movement is a response shown by a living organism towards or away from the stimulus. It is more clearly visible in most of the animals than in plants. It can occur at:
- Cellular level e. g., cytoplasmic streaming and motility of gametes.
- Organ level, e.g., heartbeat, movement of a limb, shoot, root etc.
Stimulus (plural: stimuli) is any influence or change in external and internal environment.
Response is a change in the activity of reaction of the organism to the stimulus.
Locomotion is the movement of whole organism from one place to another under the influence of a stimulus. Most of the animals have the power of locomotion except a few e.g. corals and sponges. They are fixed to one place but they can move parts of their bodies. Some microscopic water protests e.g.
Euglena, chlamydomonas are able to move freely from one place to another, they resemble animals in this respect.
Locomotion is used for:
- Finding food by living organisms.
- Avoiding capture by the enemies.
- Dispersal of seeds and fruits.
- Finding new and favorable environment.
- Bringing together individuals for reproduction.