January 5, 2014

10th Biology 4 Marks Important Questions - English Medium

Q: Plant growth substances act together or against each other. Give suitable examples in support of the statement.

A: There are five major types of plant growth substances namely Auxins, Gibberellins,
Cytokinins, Abscisic Acid and Ethylene. Auxins and Gibberellins promote growth and elongation of stems and roots. Ethylene and ABA inhibits it.

Gibberellin promotes internodal elongation and is also used to obtain seedless fruits.
Cytokinins are capable of stimulating cell division and cell elongation.

Abscisic acid inhibits plant growth. It induces dormancy in buds, tubers and seeds, where as gibberellins break seed dormancy. Ethylene is the gaseous substance involved in the ripening of fruits. Cytokinins delay the process of aging leaves but ABA induces leaf shedding.

Q: Write a brief account on Adrenal glands.

A: Adrenal glands are endocrine glands.
There are two adrenal glands.
They are on the top of each kidney like a cap.
It has two parts - the outer cortex and the inner medulla.
Adrenal cortex secretes two hormones cortisol and aldosterone.
Cortisol regulates the metabolism of carbohydrates, proteins and fats.
Aldosterone increases the reabsorption of water and sodium.
Adrenal medulla secretes adrenaline.
Adrenaline helps the body to face during anger, fear or grief.
Hence Adrenaline is called fight or flight hormone.

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