The Regulators of Life – Maharashtra Board Class 10 Solutions for Science and Technology (English Medium)
- The loss of water from the plants is known as transpiration.
- Nervous system is absent in plants and unicellular organisms.
- Response to the stimulus of touch is called seismonastic movement whereas response to the stimulus of chemicals is called as chemotropic movement/chemotropism.
- Brain is the main coordinating centre of the body.
- The root system of plants always grows downwards in response to the stimulus of gravity and water.
- This ensures that the roots find soil and water.
- Hence, the roots of plants grow away from sunlight.
- Endocrine glands are ductless glands. They do not have ducts to carry the hormones secreted by them.
- The hormones are directly released into the bloodstream and reach the concerned parts of the body through blood circulation.
- Hence, the hormones secreted by the endocrine glands are present everywhere in the body.
- The hormone insulin is secreted by the cells of the pancreas.
- The rise in the sugar level of the blood is detected by these cells. As a response, these cells produce more insulin. As the sugar level of blood falls down, the secretion of insulin is reduced.
- By such a feedback mechanism, insulin regulates the sugar level of the blood.
- In this way, insulin plays an important role in controlling the sugar level of blood.
- Hydrotropic movement: Hydrotropic movement is a growth-responding movement to the stimulus of water. Roots of plants show positive hydrotropic movements as they grow towards the source of water. Plant shoots grow away from the source of water, so they show negative hydrotropic movements.
- Chemical control in animals: Chemical control in animals is brought about by hormones. Hormones are chemical substances secreted by the endocrine glands. Hormones are directly released into the bloodstream as endocrine glands are ductless glands. Hence, the hormones reach everywhere in the body through blood circulation. The endocrine system and the nervous system work in cooperation to bring control and coordination in various body activities.
Differences between voluntary and involuntary movements:
1. Reflex action:
- Reflex action is the sudden action in response to changes in the environment.
- The response in reflex action is quick and immediate. No thinking is involved in it.
- Reflex action takes place through the reflex arc which consists of sensory neuron, relay neuron and motor neuron.
- Reflex arc has the receptor organ which is a sense organ and the effector organ which is a muscle or a gland.
- Reflex arcs are formed in the spinal cord; hence, the action is spontaneous.
- In lower animals, a complex neuronal network is absent. In such cases, reflex actions help by quick responses.
2. Co-ordination in plants:
- Plants do not have a well-developed nervous or muscular system. Movements shown by the plants are in response to the stimulus.
- Movements are of two types, growth-dependent movements and growth-independent movements.
- Growth-dependent movements are called tropic movements, e.g. phototropic movements in response to light, gravitropic movements in response to gravity, hydrotropic movements in response to water and chemotropic movements in response to chemical stimuli.
- Growth-independent movements of plants occur in response to changes in the surroundings.
- The cells can either swell or shrink by changing their shapes and by altering their water content, e.g. opening and closing of the lotus, movements of insectivorous plants and seismonastic movements shown by Mimosa plant in response to touch.