Answer the following.
a. Explain chemical co-ordination in humans and give the names and functions of some hormones.
b. Explain the difference between the excretory system of humans and plants.
c. Explain co-ordination in plants with the help of suitable examples.
a. Explain chemical co-ordination in humans and give the names and functions of some hormones.
a. Coordination in humans occurs in two levels i.e. nervous coordination and chemical coordination. The coordination which occurs with the help of hormones is called chemical coordination. Hormones are the organic chemicals produced by the body, which are released into the blood. The key feature of the hormones is that they are secreted by the ductless glands. The glands that secrete hormones do not have ducts. Hormones are released directly into the bloodstream and reach the target organ. The endocrine system works in association with nervous system to control and coordinate our bodies.
Characteristics of Hormones
- Hormones are the organic chemicals that are secreted in response to environmental changes in or outside the body.
- Hormones are secreted by ductless glands and transported along with the blood stream to the site of their action. The site of their production and the organ of their influence are different.
- They can be amino-acid derivatives, proteins, or steroids.
- Being low molecular weight substances, they can easily diffuse through the cell membrane.
- They are produced in small quantities and are effective in extremely lower concentrations.
- Abnormal production of hormones (be it less or more) affects the body in a negative manner.
i. Some of the hormones produced by pituitary are:
- Prolactin- Growth of mammary glands and formation of milk in them.
- TSH- Synthesis and release of thyroid hormones.
- Adrenocorticotrophic hormone (ACTH)- Stimulates synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex.
- Vasopressin- Stimulates reabsorption of water from the distal tubules, and hence, prevents loss of water through urine (diuresis); therefore, also called anti-diuretic hormone (ADH).
ii. Thyroxine hormone is produced by thyroid gland and its functions are:
- Control of BMR (Basal metabolism rate)
- Control of working of kidney and urine formation
- Regulation of physical, mental, and sexual growth
- Regulation of growth of CNS and bones
- Regulation of carbohydrate and fat metabolism
b.
Excretion in plants
Excretion in animals
1. Plants do not have specialised structures for excretion.
1. Animals have specialised structures like nephrons for excretion.
2. Process of excretion occurs through stomata and lenticels.
2. Process of excretion occurs through kidney, skin, lungs etc.
3. Waste is produced in the form of CO2 and O2.
3. Waste is produced in the form of nitrogenous waste like urea, uric acid and ammonia.
c. Since plants do not have nervous and muscular system like animals, coordination in plants occurs in response to particular stimuli. Tropism/tropic movement is the term used for the movement or growth of any plant part in response to an external stimulus.
These tropic movements can be of various types like:
Phototropism: The growth movement in plants in response to light stimulus is known as phototropism. For example, the flower head of a sunflower is positively phototropic as it moves from East to West, along with the movement of the Sun.
Geotropism: The growth movement in plants in response to the force of gravity is known as geotropism. In geotropism, the roots of the plant always grow downwards, while the shoots always grow upwards, away from the earth.
Chemotropism: The growth movement in plants in response to chemical stimuli is known as chemotropism. For example, the growth of pollen tube towards the ovule in the ovary (through the stigma and style) is an example of positive chemotropism.
Hydrotropism: The growth movement in plants in response to water is known as hydrotropism. For example, the roots of some plants grow towards the water source, even when the water source is not present directly below it.
Thigmotropism: The growth movement in plants in response to a touch stimulus or contact with a solid object is known as thigmotropism. For example, in some plants, the coiling of tendrils occurs when they come in contact with objects for support.
a. Coordination in humans occurs in two levels i.e. nervous coordination and chemical coordination. The coordination which occurs with the help of hormones is called chemical coordination. Hormones are the organic chemicals produced by the body, which are released into the blood. The key feature of the hormones is that they are secreted by the ductless glands. The glands that secrete hormones do not have ducts. Hormones are released directly into the bloodstream and reach the target organ. The endocrine system works in association with nervous system to control and coordinate our bodies.
Characteristics of Hormones
- Hormones are the organic chemicals that are secreted in response to environmental changes in or outside the body.
- Hormones are secreted by ductless glands and transported along with the blood stream to the site of their action. The site of their production and the organ of their influence are different.
- They can be amino-acid derivatives, proteins, or steroids.
- Being low molecular weight substances, they can easily diffuse through the cell membrane.
- They are produced in small quantities and are effective in extremely lower concentrations.
- Abnormal production of hormones (be it less or more) affects the body in a negative manner.
- Prolactin- Growth of mammary glands and formation of milk in them.
- TSH- Synthesis and release of thyroid hormones.
- Adrenocorticotrophic hormone (ACTH)- Stimulates synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex.
- Vasopressin- Stimulates reabsorption of water from the distal tubules, and hence, prevents loss of water through urine (diuresis); therefore, also called anti-diuretic hormone (ADH).
- Control of BMR (Basal metabolism rate)
- Control of working of kidney and urine formation
- Regulation of physical, mental, and sexual growth
- Regulation of growth of CNS and bones
- Regulation of carbohydrate and fat metabolism
b.
Excretion in plants |
Excretion in animals |
1. Plants do not have specialised structures for excretion. |
1. Animals have specialised structures like nephrons for excretion. |
2. Process of excretion occurs through stomata and lenticels. |
2. Process of excretion occurs through kidney, skin, lungs etc. |
3. Waste is produced in the form of CO2 and O2. |
3. Waste is produced in the form of nitrogenous waste like urea, uric acid and ammonia. |
c. Since plants do not have nervous and muscular system like animals, coordination in plants occurs in response to particular stimuli. Tropism/tropic movement is the term used for the movement or growth of any plant part in response to an external stimulus.
These tropic movements can be of various types like:
Phototropism: The growth movement in plants in response to light stimulus is known as phototropism. For example, the flower head of a sunflower is positively phototropic as it moves from East to West, along with the movement of the Sun.
Geotropism: The growth movement in plants in response to the force of gravity is known as geotropism. In geotropism, the roots of the plant always grow downwards, while the shoots always grow upwards, away from the earth.
Chemotropism: The growth movement in plants in response to chemical stimuli is known as chemotropism. For example, the growth of pollen tube towards the ovule in the ovary (through the stigma and style) is an example of positive chemotropism.
Hydrotropism: The growth movement in plants in response to water is known as hydrotropism. For example, the roots of some plants grow towards the water source, even when the water source is not present directly below it.
Thigmotropism: The growth movement in plants in response to a touch stimulus or contact with a solid object is known as thigmotropism. For example, in some plants, the coiling of tendrils occurs when they come in contact with objects for support.
