Explain testosterone in secondary sexual development
Testes → blood-borne testosterone → responsive tissues. Voice, facial hair and muscle changes are typical secondary-characteristic examples.
Exam scope and assessment notes
Core and Extended · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall endocrine glands, blood-borne hormones, ovaries, testes, uterine lining, ovulation and implantation.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which organ is the principal source used in this testosterone pathway?
What you will learn
- Link the testes with testosterone secretion
- Explain typical testosterone-associated puberty changes
Original teaching model.
| Feature | Meaning |
|---|---|
| Source | Testes |
| Signal | Testosterone in blood |
| Examples | Voice deepening; facial hair; muscle development |
| Separate product | Sperm cells |
Link the testes with testosterone secretion
Testosterone is secreted by the testes and carried in the blood to responsive tissues. Its increasing action during typical male puberty contributes to the development and regulation of secondary sexual characteristics. Naming the testes as a source is different from naming sperm as a product: sperm are cells, whereas testosterone is a hormone. The same organ has both reproductive and endocrine functions.
Examples of testosterone-associated changes include deeper voice, facial hair development and increased muscle development. In a causal answer, connect the hormone with a responding tissue and the resulting characteristic. Do not describe the hormone as pushing air into the larynx or carrying new muscles through the sperm duct. A blood-borne signal can act at tissues distant from its source.
Explain typical testosterone-associated puberty changes
The pathway diagram uses testes, blood-borne testosterone and secondary characteristics as separate boxes. This makes a source-to-response explanation possible without memorising a list alone. The endocrine source is not the target, and a sperm duct is not the main hormone-transport route. Testosterone also has reproductive roles, but a question about secondary characteristics needs a body-feature example.
These are typical biological associations used for curriculum explanations. Testosterone is not a substance found only in one sex, and the listed changes need not occur at identical ages or to identical degrees in every individual. A classroom model supplies no diagnostic threshold. Describe the stated hormone role without making personal predictions from appearance.
Pause and explain
Which answer describes a secondary characteristic?
Worked example
Explain typical voice deepening at puberty using a source and signal.
Show the worked solution
- Name testosterone secreted by testes.
- Link action on responsive tissue with voice change.
Answer Testes secrete testosterone into blood; its action on responsive tissues contributes to development of a deeper voice during puberty.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Give the testosterone source, transport route and two secondary-characteristic examples.
Give me a hint
Use organ, blood and body features.
Compare my reasoning
- Name testes and blood-borne transport.
- Choose two valid typical puberty changes.
Testes secrete testosterone; blood carries it to responsive tissues. Examples include voice deepening and facial hair development.
Look for these in your work
- Include source and route
- Give two features
Correct “testes send sperm hormones down sperm ducts to form facial hair”.
Give me a hint
Separate two testis products and their routes.
Compare my reasoning
- Distinguish sperm cells from testosterone.
- Identify blood as the endocrine transport route.
Testes produce sperm and secrete testosterone. Sperm ducts transport sperm; testosterone travels in blood and contributes to facial hair development through target-tissue responses.
Look for these in your work
- Separate products
- Correct the route
A diagram labels testes as a target and facial hair as the hormone source. Repair both labels.
Give me a hint
Follow source → signal → response.
Compare my reasoning
- Place secretion at testes.
- Place the body feature at the response end.
Testes are the testosterone source; responsive skin structures develop facial hair as a secondary characteristic. Testosterone is the blood-borne signal between source and response.
Look for these in your work
- Repair both labels
- Include the signal
Common mistakes
- Sperm and testosterone are not the same product.
- A sperm duct is not the hormone transport route.
What can you explain now?
Which answer describes a secondary characteristic?
Compare with the explanation
Testosterone contributes to voice deepening
It links hormone action with a body feature.
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Make it stick
Explain link the testes with testosterone secretion and explain typical testosterone-associated puberty changes. Follow the event arrows or graph labels before opening the solutions.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.