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The Best IB Biology Study Guide and Notes for SL/HL


IB Biology is challenging, college-level biology, so sometimes you will need a little more study help than your class notes provide. In this article, I've compiled the best FREE online IB Biology study guides (including IB Biology Notes and IB Biology Revision) into one resource and provided you with some IB Biology practice questions.



2022 IB Exam Changes Due to COVID-19

Because of the ongoing COVID-19 (coronavirus) pandemic, the IB has decided to extend the adaptations which were put in place for 2021 to 2022. May 2022 IB assessments will have two routes, exam and non-exam, depending on which your school chooses. Stay up to date with the latest information on what this means for IB diplomas, course credit for IB classes, and more with our our IB COVID-19 FAQ article.


How to Use This IB Biology Study Guide

This IB Biology Study Guide is ordered using the IB Biology Syllabus. If there is a single topic you are interested in learning more about, use the Command + F function on your computer to search the article for that term. For example, if you want to learn more about Cell Theory, use Command + F to bring up the search function. Type in "Cell Theory" and it will bring up all of the study materials for Cell Theory.

If you are looking for general quiz material for the whole IB Biology Exam, you can skip to the end of the article to the Overall Reviews section for great overall study resources.

First, I will delve into resources by IB Biology Topic. I will separate the resources into:

  • Quick Reference: These guides primarily come from the site IB Guides. They're short summaries of the information that often include definitions and diagrams. NOTE: These guides haven't been updated since before the 2016 syllabus changes, so be sure to keep your syllabus handy as you go through them so you don't go crazy trying to memorize info you don't need to know.
  • Longer Notes: These longer notes come from the site BioNinja. They're a more in-depth look at the material, and you can focus on the specific topic you're interested in by clicking on the topics listed on the left side of the page.
  • Overview: The IBWorld site has all the notes for each topic on one webpage. It's especially a good resource for people who want to be able to just read through a lot of notes without clicking through different pages to get to different topics.
  • Slideshow: These are powerpoint-type presentations on the material.
  • Video: Demonstration videos on how to solve problems related to the material. They come from two different sources since neither one covers all the IB Biology topics.


How Should You Use This Guide Throughout the Year?

You should use this guide throughout the year as a refresher before tests and quizzes or for additional support if you did not entirely understand a specific lesson in your IB Biology class. If you still need more assistance, check out our article on the Best IB Biology Books. You should be studying throughout the year and not waiting to cram before the IB Biology exam.

You should also be integrating real practice questions with each subject. You can find past IB Biology HL and IB Biology SL papers for sale online from the Follett IB store. Also, if you are struggling to understand the material, you should be studying the corresponding chapter in a review book as you learn that chapter in class.





Common Mistakes Students Make When Studying for IB Biology

Many students have a hard time with IB Biology. There is a lot of material to cover and you need to be learning it throughout the year(s) in order to master the IB Biology exam. Some common mistakes students make when studying are:

  • Ignoring subjects you don't understand in class: If you do not understand it in class, you need to seek more help whether through IB Biology study guides, IB Biology books, or through tutoring.
  • Only worrying about studying right before the IB Biology exam: There is way too much material to cover to learn it all in a few days or weeks (there is a reason it is spread over one to two years). Learn the material as you cover it in class. Use this study guide for help understanding the concepts you cover in class.


Study Guide for the IB Biology SL/HL Core

Below are all the best notes for IB Biology SL and HL. IB Biology SL consists of a minimum of 150 prescribed hours, and IB Biology HL consists of a minimum of 240 prescribed hours. Both levels cover topics 1-6, and HL additionally consists of topics 7-11. For both levels, you'll also cover one of the four options (A through D), at either the SL or HL level.



Command Terms

  • Slideshow: Excellent interactive slideshow that gives you tips and tricks.
  • Knowing the command terms is the most crucial part of the IB Biology Exam. If you do not understand the difference in command terms (such as Draw, Annotate, Outline, Analyze, etc.), you will not be able to answer the questions correctly.




Topic #1: Cell Biology

Topic 1 Overview Notes

1.1 Introduction to cells

1.2 Ultrastructure of cells

1.3 Membrane structure

1.4 Membrane transport

1.5 The origin of cells

1.6 Cell division


Topic #2: Molecular Biology

Topic 2 Overview Notes

2.1 Molecules to metabolism

2.2 Water

2.3 Carbohydrates and lipids

2.4 Proteins

2.5 Enzymes

2.6 Structure of DNA and RNA

2.7 DNA replication, transcription and translation

2.8 Cell respiration

2.9 Photosynthesis




Topic #3: Genetics

Topic 3 Overview Notes

3.1 Genes

3.2 Chromosomes

3.3 Meiosis

3.4 Inheritance

3.5 Genetic modification and biotechnology


Topic #4: Ecology

Topic 4 Overview Notes

4.1 Species, communities and ecosystems

4.2 Energy flow

4.3 Carbon cycling

4.4 Climate change




Topic #5: Evolution and Biodiversity

Topic 5 Overview Notes

5.1 Evidence for evolution

5.2 Natural selection

5.3 Classification of biodiversity

5.4 Cladistics


Topic #6: Human Physiology

Topic 6 Overview Notes

6.1 Digestion and absorption

6.2 The blood system

6.3 Defense against infectious disease

6.4 Gas exchange

6.5 Neurons and synapses

6.6 Hormones, homeostasis and reproduction


Additional Higher Level Topics

You'll only cover these topics if you are taking IB Biology HL.


Topic #7: Nucleic Acids

Topic 7 Overview Notes

7.1 DNA structure and replication

7.2 Transcription and gene expression

7.3 Translation




Topic #8: Metabolism, Cell Respiration and Photosynthesis

Topic 8 Overview Notes

8.1 Metabolism

8.2 Cell respiration

8.3 Photosynthesis


Topic #9: Plant Biology

Topic 9 Overview Notes

9.1 Transport in the xylem of plants

9.2 Transport in the phloem of plants

9.3 Growth in plants

9.4 Reproduction in plants


Topic #10: Genetics and Evolution

Topic 10 Overview Notes

10.1 Meiosis

10.2 Inheritance

10.3 Gene pools and speciation




Topic #11: Animal Physiology

Topic 11 Overview Notes

11.1 Antibody production and vaccination

11.2 Movement

11.3 The kidney and osmoregulation

11.4 Sexual reproduction




In addition to the above topics, you'll also cover one of the options below (typically your teacher decides which option is covered). Whichever option you study, you'll cover three or four topics (15 hours total) for SL and an additional two or three topics (25 hours total) for HL.


Overall Notes

Options Overview Notes


A. Neurobiology and Behavior: Core

Additional Higher Level Topics




B. Biotechnology and Bioinformatics: Core

Additional Higher Level Topics




C. Ecology and Conservation: Core

Additional Higher Level Topics


D. Human Physiology: Core

Additional Higher Level Topics


Overall IB Biology Reviews

These four resources are general review resources IB Biology students can use to help them prepare for the final exam.

  • Mistakes to Avoid on the IB Biology Exam: Short video in which an IB Biology teacher explains the mistakes students typically make "from mistakes [she's] personally seen students make and from reading the examiner's reports for the 2011 and 2012 IB Biology exams."





What's Next?

Want a more in-depth look at what IB Biology covers? Read our guide to the Complete IB Biology Syllabus SL/HL.

A review book can be your best study tool for IB. To make sure you get a good one, check out our guide on the best IB Biology books. You can also supplement your studying with our articles on enzymes, functions of the cell membrane and endoplasmic reticulum, cell theory, the photosynthesis equation, and homologous vs. analogous structures.

Not sure whether you should take IB or AP classes? Read our guide: What's Better for You: IB or AP? to learn which you should take!



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Dora Seigel
About the Author

As an SAT/ACT tutor, Dora has guided many students to test prep success. She loves watching students succeed and is committed to helping you get there. Dora received a full-tuition merit based scholarship to University of Southern California. She graduated magna cum laude and scored in the 99th percentile on the ACT. She is also passionate about acting, writing, and photography.

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