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Adolescence: A Stage of Growth and Change - Growing With Age: The Teenage Years

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Adolescence is the period of life between childhood and adulthood, typically from age 1111 to 1919. These individuals are often called 'teenagers'.

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Puberty is the period during which the human body undergoes physical changes to reach reproductive maturity.

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A significant change during puberty is the sudden increase in height, which can be estimated using the ratio of current height to the expected percentage of growth for a specific age.

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The larynx, or voice box, grows larger during puberty. In boys, it develops into a visible protrusion called the Adam's apple.

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Secondary sexual characters, such as facial hair in boys and breast development in girls, are controlled by hormones like testosterone (male) and estrogen (female).

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Hormones are chemical substances secreted by endocrine glands (ductless glands) directly into the bloodstream.

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The sex of a child is determined by sex chromosomes: females have two XX chromosomes (XXXX), and males have one XX and one YY chromosome (XYXY).

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The start of the menstrual cycle is called menarche, and its permanent stoppage (usually between ages 4545 and 5050) is called menopause.

📐Formulae

Calculation for full height (cm)=Present height (cm)% of full height at this age×100\text{Calculation for full height (cm)} = \frac{\text{Present height (cm)}}{\% \text{ of full height at this age}} \times 100

Total Chromosomes in Human Cell=23 pairs=46\text{Total Chromosomes in Human Cell} = 23 \text{ pairs} = 46

Female Genotype=XX\text{Female Genotype} = XX

Male Genotype=XY\text{Male Genotype} = XY

💡Examples

Problem 1:

A boy is 1212 years old and is 150 cm150\text{ cm} tall. If he has reached 75%75\% of his full height at this age, what will be his estimated height at the end of his growth period?

Solution:

Estimated full height=15075×100=200 cm\text{Estimated full height} = \frac{150}{75} \times 100 = 200\text{ cm}

Explanation:

By dividing the current height (150 cm150\text{ cm}) by the percentage of full height achieved (75%=0.7575\% = 0.75) and multiplying by 100100, we find the projected adult height.

Problem 2:

Calculate the difference in height between two friends if Friend A is 165 cm165\text{ cm} and Friend B is 152 cm152\text{ cm}.

Solution:

165−15213\begin{array}{r} 165 \\ - 152 \\ \hline 13 \end{array}

Explanation:

The difference in their heights is 13 cm13\text{ cm}.

Problem 3:

What is the probability of a child being a boy or a girl based on chromosome inheritance?

Solution:

The egg always provides an XX. If the sperm provides XX, the result is XXXX (Girl). If the sperm provides YY, the result is XYXY (Boy). This leads to a 50%50\% or 12\frac{1}{2} probability for each.

Explanation:

Since the father produces 50%50\% XX-carrying sperm and 50%50\% YY-carrying sperm, the sex determination depends entirely on which type of sperm fertilizes the egg.