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Tamil Nadu (TNBSE)Class 10 Science★ 4-7 marks in the TN SSLC Class 10 Science public exam through MCQs and short answers

Plant and Animal Hormones

Samacheer Kalvi (TN State Board) Class 10 Science — Biology Chapter 16, Plant and Animal Hormones. Chemical coordination through plant hormones (auxins, gibberellins, cytokinins, abscisic acid, ethylene) and animal hormones from endocrine glands (pituitary, thyroid, pancreas, adrenal). Notes with functions, common mistakes, practice and quick revision.

⏱ 18 min readEasy difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1List plant hormones and their functions
2Name endocrine glands and their hormones
3Explain the role of the pituitary as the master gland
4Link thyroxine to iodine and insulin to blood sugar
5Describe adrenaline as the emergency hormone

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Why this chapter matters

Hormones coordinate growth and body functions in plants and animals. The hormone–gland–function tables are easy, high-yield recall questions in the TN SSLC exam and explain conditions like diabetes and goitre.

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Chapter 15 — Nervous System

Coordination in the body.

Plant and Animal Hormones — Class 10 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 10 Science, Biology — Chapter 16. Chemical messengers that coordinate growth and body functions.

1. About this chapter

This chapter explains chemical coordination — how plant hormones control growth and how animal hormones from endocrine glands regulate body functions.

2. Plant hormones (phytohormones)

Hormone	Main function
Auxins	promote cell elongation; apical dominance, phototropism
Gibberellins	stem elongation, seed germination
Cytokinins	promote cell division; delay ageing
Abscisic acid (ABA)	growth inhibitor; closes stomata; promotes dormancy
Ethylene	ripening of fruits

3. Animal hormones and endocrine glands

Gland	Hormone	Function
Pituitary	growth hormone (and others)	"master gland"; controls other glands and growth
Thyroid	thyroxine (needs iodine)	regulates metabolism; deficiency → goitre
Pancreas	insulin / glucagon	controls blood sugar; lack of insulin → diabetes
Adrenal	adrenaline	"fight or flight" emergency hormone
Gonads	sex hormones	control reproduction and secondary sexual characters

4. Common mistakes

Mistake: Saying ethylene causes cell division. Fix: Ethylene ripens fruit; cytokinins promote cell division.
Mistake: Confusing insulin and adrenaline. Fix: Insulin (pancreas) lowers blood sugar; adrenaline (adrenal) is the emergency hormone.
Mistake: Forgetting iodine's link to thyroid. Fix: Thyroxine needs iodine; its deficiency causes goitre.

5. Practice (book-back style)

Name the plant hormone that ripens fruits.
Which hormone promotes cell elongation in plants?
Why is the pituitary called the master gland?
What happens when the body lacks insulin?
Name the hormone secreted during emergencies.

6. Answer key

Ethylene.
Auxin.
It controls the secretion of other endocrine glands and regulates growth.
Blood sugar rises, causing diabetes mellitus.
Adrenaline (from the adrenal gland).

7. Quick revision

Biology Ch 16 · plant and animal hormones (chemical coordination).
Plant: auxin (elongation), gibberellin (stem/germination), cytokinin (division), ABA (inhibitor, stomata), ethylene (ripening).
Pituitary = master gland; thyroid → thyroxine (iodine); pancreas → insulin (diabetes if lacking).
Adrenal → adrenaline (fight or flight).
Hormones coordinate growth and body functions chemically.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Plant hormones

auxin, gibberellin, cytokinin, ABA, ethylene

Growth and ripening control.

Master gland

pituitary

Controls other endocrine glands.

Thyroid / pancreas

thyroxine (iodine); insulin (blood sugar)

Deficiency → goitre / diabetes.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Saying ethylene causes cell division

✓ Ethylene ripens fruit; cytokinins promote cell division.

WATCH OUT

✗ Confusing insulin and adrenaline

✓ Insulin (pancreas) lowers blood sugar; adrenaline (adrenal) is the emergency hormone.

WATCH OUT

✗ Forgetting iodine's link to the thyroid

✓ Thyroxine needs iodine; its deficiency causes goitre.

NCERT exercises (with solutions)

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Multiple choice questions

MCQs on plant and animal hormones.

Questions

Short answer questions

Hormone functions, glands and deficiencies.

Questions

Match the following

Match hormones with their glands/functions.

Questions

Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· Recall

Name the plant hormone that ripens fruits.

▶ Show solution

Ethylene.

Q2EASY· Recall

Which hormone promotes cell elongation in plants?

▶ Show solution

Auxin.

Q3MEDIUM· Concept

Why is the pituitary called the master gland?

▶ Show solution

Because it controls the secretions of the other endocrine glands and regulates overall growth.

Q4MEDIUM· Application

What happens when the body lacks insulin?

▶ Show solution

Blood sugar rises, leading to diabetes mellitus.

Q5EASY· Recall

Name the hormone secreted during emergencies.

▶ Show solution

Adrenaline (from the adrenal gland).

Q6MEDIUM· Application

Which mineral is needed for thyroxine, and what does its deficiency cause?

▶ Show solution

Iodine; its deficiency causes goitre.

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•Biology Chapter 16 of Samacheer Kalvi Class 10 Science.
•Plant: auxin (elongation), gibberellin (stem/germination), cytokinin (division), ABA (inhibitor), ethylene (ripening).
•Pituitary = master gland.
•Thyroid → thyroxine (needs iodine; goitre if deficient).
•Pancreas → insulin (lack → diabetes).
•Adrenal → adrenaline (fight or flight).

Tamil Nadu (TNBSE) marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 4-7 marks across MCQ, short answer and match questions

Question type	Marks each	Typical count	What it tests
MCQ	1	1-2	Hormones and glands
Short Answer	2-3	1-2	Functions and deficiencies
Match	1-2	0-1	Hormone–gland matching

Prep strategy

Memorise the plant hormone table
Learn gland–hormone–function for animals
Link deficiencies (goitre, diabetes)
Remember pituitary as the master gland

Where this shows up in the real world

This chapter isn't just an exam topic — it lives in the world around you.

Agriculture

Plant hormones are used to ripen fruit and promote rooting.

Medicine

Insulin and thyroid treatments manage diabetes and goitre.

Nutrition

Iodised salt prevents thyroid disorders.

Exam strategy

Battle-tested tips from teachers and toppers for this chapter.

Use tables for hormone functions
Link each deficiency to its disorder
Keep plant and animal hormones separate
State the gland for each animal hormone

Going beyond the textbook

For olympiad aspirants and curious learners — topics that build on this chapter.

Explain feedback control of blood sugar by insulin and glucagon.
Describe an experiment showing phototropism due to auxin.

Where else this chapter is tested

CBSE board isn't the only one — other exams test this chapter too.

TN SSLC Class 10 Public ExamHigh

Foundation / NTSE BiologyMedium

School unit testsHigh

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Questions students ask

The real ones — pulled from the Q&A community and tutor sessions.

Nerves give fast, short-lived electrical responses; hormones are chemical messengers carried by blood that act more slowly but have longer-lasting effects.

Iodine is needed to make thyroxine; iodised salt prevents iodine deficiency and the resulting goitre.

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