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. Human body is chemically coordinated by the complex chemical compounds called hormones. They are secreted by endocrine glands, examples thyroid, pituitary, adrenal glands. Hormones are released directly into blood circulation and transport to the target organ for chemical co-ordination.

Some of the hormones are:

i. Growth hormone: It regulate height and growth of human body.

ii. Thyroxine: Stimulate tissue metabolism and maintains basic metabolic rate.

iii. Adrenaline: It is stress hormone, it controls behaviour during emergency and emotional situations.

B.

•Removal of waste products from the body is called excretion. The function of excretion done by the excretory system.

•The primary components of the excretory system are the kidneys, the ureter, the urinary bladder, and the urethra.

•When blood reaches the kidneys, useful substances are absorbed back into blood, while the waste materials are dissolved in water and removed from the body in the form of urine.

•Plants remove waste materials by various processes as they do not have any excretory system.

•Oxygen, a by-product of photosynthesis is removed through stomata.

•Most of the waste substances of plants are stored in vacuoles of leaf-cells and in flowers, fruits and the bark of the stem.

•Some waste materials are stored in xylem the form of resin and gum. Some waste materials excreted through roots into the surrounding soil.

C.

Nervous system and muscular system brings movement in animals. These systems are absent in plants. It doesn't mean that plant do not show movement. Plants also show movements, called growth movements. The plant hormones or growth regulators bring about coordination in plants.

Examples:

•Auxin: it promotes growth in the stem and root.

•Gibberelin: it promotes seed germination.

•Cytokinin: it promotes cell division.

•Abscisic acid: it prevents seed germination.