Online NCERT Notes on Chapter=7 (Control and Coordination) Part 2

This is Online NCERT Notes on Chapter=7 (Control and Coordination)  Part 2 for preparation of CBSE BOARD Examination, NTSE etc.

COORDINATION IN PLANTS:

Movements in plants :

(i) Independent of growth

(ii) Dependent on growth

(i) Independent of growth : Immediate response to stimulus.

• Plants use electrical-chemical means to convey information from cell to cell.

• For movement to happen, cells change their shape by changing the amount of water in them, resulting in swelling or shrinking of cells.

E.g., Drooping of leaves of ‘Touch-me-not’ plant on touching it.

(ii) Dependent on growth : These movements are tropic movements i.e., directional movements in response to stimulus.

• Tendrils : The part of tendril away from the object grows more rapidly as compared to the part near the object. This causes circulating of tendril around the object.

• Phototropism : Movement towards light.

• Geotropism : Movement towards/away from gravity.

• Chemotropism : Growth of pollen tube towards ovule.

• Hydrotropism : Movement towards water.

Plant Hormones : Are chemical compounds which help to coordinate growth, development and responses to the environment.

Main plant hormones are :

(a) Auxin :

• Synthesized at shoot tip

• Helps the cells to grow longer

• Involved in phototropism

(b) Gibberellin :

• Helps in the growth of the stem

(c) Cytokinins :

• Promotes cell division

• Present in greater concentration in fruits and seeds

(d) Abscisic Acid : 

• Inhibits growth

• Cause wilting of leaves

• Stress hormone

Hormones in Animals :

Hormones : Hormones are the chemical substances which coordinate the activities of living organisms and also their growth.

Endocrine glands : These glands secrete their product (hormone) into the blood. Endocrine Gland, Hormones and their Functions

Endocrine Gland, Hormones and their Functions

Iodised salt is necessary because iodine mineral is essential part of thyroxine hormone secreted by thyroid gland.

Thyroxine regulates metabolism of carbohydrates, fats and proteins.

So, we must consume iodised salt which is necessary for proper working of thyroid gland. It’s deficiency causes a disease called goiter (Swollen neck).

Diabetes:

Disease in which blood sugar level increase.

Cause : Due to the deficiency of insulin hormone secreted by pancreas that is responsible to control blood sugar levels.

Treatment : Injections of insulin hormone.

Feedback Mechanism:

The excess or deficiency of hormones has a harmful effect on our body.
Feedback mechanism makes sure that hormones should be secreted in precise quantity and at right time.

E.g., Feedback mechanism to control the sugar level in blood is as follows :

Sugar level in the blood rises.

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