Q BankQuestion BankDocsDocuments

C2.1.3 (HL)—Functional categories in animals

Animal signalling includes hormones and nervous communication, with chemical messengers acting through target cells, receptors and feedback mechanisms, linking signal detection to a specific target-cell response.

Syllabus
First assessment 2025
Objective
C2.1.3
Level
HL

Exam analysis

Chance of appearing5%of analysed past papers
Latest appearanceNovember 2024
Most common paperPaper2
Typical marks1–7

Common command terms

  • State
  • Explain
  • Compare
  • Contrast
  • Outline

Recent exam appearances

November 2024Paper2 ["HL"] · TZ02(e)[ 1 ]C2.1.3 (HL)—Functional categories in animals
May 2021Paper2 ["HL"] · TZ16(c)[ 7 ]C2.1.3 (HL)—Functional categories in animals
November 2019Paper1 ["HL"] · TZ025[ 1 ]C2.1.3 (HL)—Functional categories in animals
May 2019Paper2 ["HL"] · TZ26(c)[ 8 ]C2.1.3 (HL)—Functional categories in animals
May 2018Paper1 ["HL"] · TZ125[ 1 ]C2.1.3 (HL)—Functional categories in animals
Practice this objective

Coverage 2012–2024 · Updated 15 Jul 2026

Concept essentials

  • Hormones are chemical messengers secreted by endocrine cells or glands.
  • Leptin is secreted by adipose tissue and acts on the hypothalamus to inhibit appetite.
  • Hormonal communication is usually blood-borne, while nervous communication is neuron-based and faster.
  • Feedback mechanisms help regulate hormone-controlled physiological variables.
ConceptIB Biology HL