CBSE Questions for Class 8 Biology Reaching The Age Of Adolescence Quiz 2 - MCQExams.com

• Metamorphosis is a profound change of form during development from larva to adult animals. 
• The process of metamorphosis is essentially under hormonal control. Hormones from the hypothalamus (e.g. TSH or thyroid-stimulating hormone) and the thyroid gland regulate the process of metamorphosis. 
• Thyroxine hormone secreted by the thyroid gland affects the tissues directly, causing the degeneration and necrosis of some cells and stimulating the growth and differentiation of others. 
• Thus, thyroid glands play a key role in the metamorphosis of a frog.

$$\textbf{Correct option:D}$$ 

$$\textbf{Solution:}$$

$$\textbf{Option (A)}$$

$$\bullet$$ The endocrine part of the pancreas gland is an aggregation of cells known as islets of Langerhans which consists of four types of cells: alpha cells secretes glucagon, beta cells secretes insulin that regulates sugar metabolism ,delta cells produce somatostatin and f cells secretes pancreatic polypeptide that inhibits growth of tissue, secretion of pancreatic and gastric juice.

$$\textbf{Option (B)}$$

$$\bullet$$ Adrenal gland is divided into two sections; adrenal cortex secretes aldosterone that helps in salt metabolism, cortisol that regulates sugar homeostasis and sex corticoids such as androgens and estrogens. Adrenal medulla secretes epinephrine and nor epinephrine that is secreted at the time of emergency.

$$\textbf{Option (C)}$$

$$\bullet$$ Thyroid glands secrete thyroxine and triiodothyronine which increases metabolic rate of the body, prenatal brain development and regulates temperature in the body, another hormone thyrocalcitonin helps with the regulation of calcium metabolism.

$$\textbf{Option (D)}$$

$$\bullet$$ There are three pairs of salivary glands parotid, sublingual and submandibular which secrete ptyalin (amylase enzyme that helps in initial carbohydrate breakdown .

$$\textbf{Hence, the correct option is (D)}$$

• The larynx is also called the voice box. It is located between the pharynx and the trachea. It has a framework of cartilage that protrudes in the front of the neck and sometimes is referred to as Adam's apple. 
• The larynx is considerably larger in the male than in the female; hence, Adam's apple is much more prominent in the male. At the upper end of the larynx are the vocal cords, which serve in the production of speech. 
• They are set into vibration by the flow of air from the lungs. A difference in the size of the larynx is what accounts for the difference between the male and female voices; because a man's larynx is larger than a woman's, his voice is lower in pitch. 
• So, the correct answer is option D.

• Secondary sexual characters are features that appear during puberty in humans and sexual maturity in other animals. They distinguish the two sexes of a species but are not directly part of the reproductive system.
•  Secondary sexual characters common in males and females: Growth of hairs under armpits and around the pubic area, increased activity of sweat and sebaceous glands, oily skin and appearance of pimples, darkening in skin colour of the genital area. 
• Secondary sexual characters in male: Widening of shoulders, deepening of the voice, appearance of beard and mustaches. The growth of sex organs (testes and penis).
• Secondary sexual characters in females: Widening of pelvis and hips, high pitch voice, initiation of the menstrual cycle, the growth of mammary glands (breasts), maturation of secondary sex organs like fallopian tubes, uterus.
  

• A balanced diet means that the meals include proteins, carbohydrates, fats, and vitamins in requisite proportions. The right meal of roti/rice, dal (pulses), and vegetables is a balanced meal that constitutes all those needed for nourishment required in adolescents.
• Chips and packed or tinned snacks, though very tasty should never replace regular meals as they do not have adequate nutritional value.
  

• Morphologic changes in size, shape, composition and functioning of the body.
• Development of secondary sex characteristics.
• Development of sex organs.
• Development of pubic hair.

• The process of transformation from an immature form to an adult form in two or more distinct stages is known as metamorphosis. 
• For the metamorphosis of tadpoles, thyroid hormone along with the essential constituent iodine is necessary.
• Hence the correct option is D.

• Adolescence is the period of life when the body undergoes changes, leading to reproductive maturity.  The period following the onset of puberty during which a young person develops from a child into an adult is called adolescence. 
• It is marked by accelerated physical growth, development of reproductive organs, and changes in the functioning of the neuroendocrine system.