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Topic 4

EDEXCEL IAL BIOLOGY

Specification 2025 - 2026

Unit 2

Biology Checklist – Topic 4: Plant Structure and Function, Biodiversity and Conservation

Topic 4 – Plant Structure and Function, Biodiversity and Conservation

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4.1 Structure and Ultrastructure of Plant Cells

(i) Know the structure and ultrastructure of plant cells including cell wall , chloroplast , amyloplast , vacuole , tonoplast , plasmodesmata , pits and middle lamella and be able to compare it with animal cells .

(ii) Understand the function of the structures listed in (i).

4.2 Recognising Organelles

Be able to recognise the organelles in 4.1 from electron microscope (EM) images.

4.3 Structure and Function of Polysaccharides

Understand the structure and function of the polysaccharides starch and cellulose , including the role of hydrogen bonds between the β-glucose molecules in forming cellulose microfibrils .

4.4 Cellulose Microfibrils and Secondary Thickening

Understand how the arrangement of cellulose microfibrils and secondary thickening in plant cell walls contributes to the physical properties of xylem vessels and sclerenchyma fibres in plant fibres that can be exploited by humans.

4.5 Plant Structures and Functions

Know the similarities and differences between the structures of, the position in the stem, and the function of sclerenchyma fibres (support), xylem vessels (support and transport of water and mineral ions ) and phloem (translocation of organic solutes ).

AS Biology Notes

Check the IAL Biology ebook

4.6 CORE PRACTICAL 7

Use a light microscope to: (i) Make observations, draw and label plan diagrams of transverse sections of roots , stems and leaves . (ii) Make observations, draw and label cells of plant tissues . (iii) Identify sclerenchyma fibres , phloem , sieve tubes and xylem vessels and their location.

4.7 Sustainability

Understand how the uses of plant fibres and starch may contribute to sustainability , including plant-based products to replace oil-based plastics.

4.8 Importance of Water and Inorganic Ions

Understand the importance of water and inorganic ions ( nitrate , calcium ions and magnesium ions ) to plants .

Recommended Additional Practical: Investigate plant mineral deficiencies .

4.9 CORE PRACTICAL 8

Determine the tensile strength of plant fibres .

4.10 Conditions for Bacterial Growth

Understand the conditions required for bacterial growth .

4.11 Antimicrobial and Therapeutic Properties of Plants

Know that substances derived from plants can have antimicrobial and other therapeutic properties .

4.12 CORE PRACTICAL 9

Investigate the antimicrobial properties of plants , including aseptic techniques for safe handling of bacteria.

4.13 Drug Testing

Understand development of drug testing from historic to contemporary protocols, including William Withering’s digitalis soup , double blind trials , placebo and three-phased testing.

4.14 Classification

(i) Understand that classification organises the variety of life using differences/similarities in phenotypes and genotypes , based on the species concept .

(ii) Understand critical evaluation of new data leading to new taxonomic groupings based on molecular evidence , including the three-domain system ( Archaea , Bacteria , Eukarya ).

4.15 Threats to Biodiversity

Know that, over time, the variety of life has become extensive but is now threatened by human activity.

4.16 Biodiversity and Endemism

Understand what is meant by biodiversity and endemism .

4.17 Measuring Biodiversity

Know how biodiversity can be measured within a habitat using species richness and within a species using genetic diversity by calculating the heterozygosity index : H = number of heterozygotes / number of individuals in the population.

4.18 Comparing Biodiversity

Understand how biodiversity can be compared in habitats using an index of diversity (D) : D = N(N − 1) / Σn(n − 1).

4.19 Concept of Niche and Adaptations

Understand the concept of niche and discuss examples of adaptations of organisms to their environment ( behavioural , anatomical and physiological ).

4.20 Hardy-Weinberg Equation

(i) Understand how the Hardy-Weinberg equation can be used to see whether a change in allele frequency occurs over time.

(ii) Understand that changes in allele frequency can result from mutation and natural selection .

(iii) Understand that reproductive isolation can lead to accumulation of different genetic information in populations, leading to new species.

4.21 Conservation Methods

Evaluate methods used by zoos and seed banks in conservation of endangered species and their genetic diversity , including research, captive breeding, reintroduction, and education.

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IAL Biology 2025 - 2026

Complete Course (Units 1 + 2 + 3)

✅ All Components of units 1 and 2

✅ Unit 3 Practicals 🔬

✅ Two Years Access

🎁 22 Revision Classes

Topic 1
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Topic 4
Unit 3
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Topic 7
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