BIOLOGY — COMPLETE HIGH SCHOOL
STUDY NOTES
2025/2026 Academic Year • Comprehensive Revision & Exam Preparation
This original study guide is designed for secondary/high-school Biology students. It combines core concepts,
definitions, comparisons, worked examples, practical skills, exam-style questions, model answers, and
revision checklists.
Contents
1. 1. Biology and Scientific Skills
2. 2. Cell Biology
3. 3. Biological Molecules
4. 4. Enzymes
5. 5. Membranes and Transport
6. 6. Cell Division and Genetics
7. 7. DNA and Protein Synthesis
8. 8. Variation and Evolution
9. 9. Classification
10. 10. Plant Structure and Transport
11. 11. Photosynthesis
12. 12. Human Nutrition and Digestion
13. 13. Respiration and Gas Exchange
14. 14. Circulation and Transport in Humans
15. 15. Excretion and Homeostasis
16. 16. Nervous and Endocrine Coordination
17. 17. Immunity and Disease
18. 18. Reproduction
19. 19. Ecology and Ecosystems
20. 20. Practical Biology and Microscopy
21. 21. Exam Skills
22. 22. Key Definitions
23. 23. Practice Questions
24. 24. Model Answer Points
25. 25. Final Revision Checklist
1. Biology and Scientific Skills
What is Biology?
Biology is the scientific study of living organisms and the processes that allow them to survive, grow,
reproduce and interact with their environment.
Characteristics of Living Organisms
Living organisms show features including cellular organization, nutrition, respiration, growth, response to
stimuli, excretion and reproduction.
, Scientific Method
A scientific investigation normally involves a question, hypothesis, planning, controlled variables, data
collection, analysis and a conclusion. Repeated observations and appropriate controls improve reliability.
Variables
The independent variable is deliberately changed. The dependent variable is measured. Controlled variables
are kept as constant as practical.
Accuracy, Precision and Reliability
Accuracy describes closeness to the true value. Precision describes how close repeated measurements are
to each other. Reliability is improved by repeats and consistent methods.
2. Cell Biology
Cell Theory
All living organisms are made of cells; the cell is the basic unit of life; and new cells arise from existing cells.
Prokaryotic Cells
Prokaryotes are generally small cells without a membrane-bound nucleus. Their DNA is located in a nucleoid
region. Bacteria are common examples.
Eukaryotic Cells
Eukaryotic cells contain a nucleus and membrane-bound organelles. Animals, plants, fungi and many protists
are eukaryotes.
Cell Membrane
The cell membrane is selectively permeable and regulates movement of substances. It also contains proteins
involved in transport and communication.
Nucleus
The nucleus contains chromosomes made of DNA and helps control cellular activities by regulating gene
expression.
Mitochondria
Mitochondria are sites of aerobic respiration and ATP production. Cells with high energy demands often
contain many mitochondria.
Ribosomes
Ribosomes assemble amino acids into proteins according to information carried by messenger RNA.
Endoplasmic Reticulum
Rough ER is associated with protein production and transport. Smooth ER is involved in lipid synthesis and
other metabolic processes.
Golgi Apparatus
The Golgi apparatus modifies, sorts and packages proteins and lipids for delivery to different destinations.
STUDY NOTES
2025/2026 Academic Year • Comprehensive Revision & Exam Preparation
This original study guide is designed for secondary/high-school Biology students. It combines core concepts,
definitions, comparisons, worked examples, practical skills, exam-style questions, model answers, and
revision checklists.
Contents
1. 1. Biology and Scientific Skills
2. 2. Cell Biology
3. 3. Biological Molecules
4. 4. Enzymes
5. 5. Membranes and Transport
6. 6. Cell Division and Genetics
7. 7. DNA and Protein Synthesis
8. 8. Variation and Evolution
9. 9. Classification
10. 10. Plant Structure and Transport
11. 11. Photosynthesis
12. 12. Human Nutrition and Digestion
13. 13. Respiration and Gas Exchange
14. 14. Circulation and Transport in Humans
15. 15. Excretion and Homeostasis
16. 16. Nervous and Endocrine Coordination
17. 17. Immunity and Disease
18. 18. Reproduction
19. 19. Ecology and Ecosystems
20. 20. Practical Biology and Microscopy
21. 21. Exam Skills
22. 22. Key Definitions
23. 23. Practice Questions
24. 24. Model Answer Points
25. 25. Final Revision Checklist
1. Biology and Scientific Skills
What is Biology?
Biology is the scientific study of living organisms and the processes that allow them to survive, grow,
reproduce and interact with their environment.
Characteristics of Living Organisms
Living organisms show features including cellular organization, nutrition, respiration, growth, response to
stimuli, excretion and reproduction.
, Scientific Method
A scientific investigation normally involves a question, hypothesis, planning, controlled variables, data
collection, analysis and a conclusion. Repeated observations and appropriate controls improve reliability.
Variables
The independent variable is deliberately changed. The dependent variable is measured. Controlled variables
are kept as constant as practical.
Accuracy, Precision and Reliability
Accuracy describes closeness to the true value. Precision describes how close repeated measurements are
to each other. Reliability is improved by repeats and consistent methods.
2. Cell Biology
Cell Theory
All living organisms are made of cells; the cell is the basic unit of life; and new cells arise from existing cells.
Prokaryotic Cells
Prokaryotes are generally small cells without a membrane-bound nucleus. Their DNA is located in a nucleoid
region. Bacteria are common examples.
Eukaryotic Cells
Eukaryotic cells contain a nucleus and membrane-bound organelles. Animals, plants, fungi and many protists
are eukaryotes.
Cell Membrane
The cell membrane is selectively permeable and regulates movement of substances. It also contains proteins
involved in transport and communication.
Nucleus
The nucleus contains chromosomes made of DNA and helps control cellular activities by regulating gene
expression.
Mitochondria
Mitochondria are sites of aerobic respiration and ATP production. Cells with high energy demands often
contain many mitochondria.
Ribosomes
Ribosomes assemble amino acids into proteins according to information carried by messenger RNA.
Endoplasmic Reticulum
Rough ER is associated with protein production and transport. Smooth ER is involved in lipid synthesis and
other metabolic processes.
Golgi Apparatus
The Golgi apparatus modifies, sorts and packages proteins and lipids for delivery to different destinations.
