Guest Hollow’s High School Biology Online Textbook

Welcome to Guest Hollow’s Free Biology Textbook!

Get ready to learn about science and the natural world in this absolutely FREE book! Why do are we offering a free book? Have a look at our About Us page, and you’ll get a sense of who we are and why we care about homeschoolers like we do. Having said that, please consider using Guest Hollow as your source for other curriculums and materials. Despite being a tiny mom-and-pop, our company has a lot to offer, and it’s growing all the time. Please explore our site as well as our social media presence and let us know what you think!

This FREE book is designed to be used with Guest Hollow’s Free High School Biology Curriculum, but anyone is free to use it. 🙂

Guest Hollow's Homeschool Biology Curriculum Textbook

We’ve taken the well-known and rigorous CK-12 biology textbook and edited it  (thanks to a Creative Commons license) to fit a Christian creationist perspective.

Choose a chapter or section and dive right in!

Question: What edits were made to the CK-12 text?

We’ve taken the rigorous CK-12 biology textbook and edited it  (thanks to a Creative Commons license) to fit a Christian creationist perspective. Edits are as follows:

  • References to evolution were taken out.
  • New videos were added. Students can watch them right from the online text!
  • Christian material was added.
  • Definitions were placed with vocabulary words in the beginning of each chapter.
  • New pictures and illustrations were added.
  • Custom illustrations were created to better communicate concepts.
  • Additional concepts and material were added.
  • Some humor was added and/or sections were rewritten to be more clear and understandable.
  • Latin and Greek root word “alerts” were created and inserted in the text – a fun way to learn vocabulary using science!
  • The human anatomy portion was taken out. We don’t believe several weeks study is adequate for a rich understanding of the human body. Check out our high school anatomy curriculum that fills this need.
  • We edited the workbook to make it more visual with added humor and edits that reflect the changes in the Guest Hollow version of the textbook.

We also added in a schedule that ties in a variety of lab options, activities, videos, workbook assignments, games, free printables, additional books, and more to make a rich learning experience that goes beyond the text!

Question: Where are the answers to the end-of-chapter questions?

We don’t provide those answers, but you can get them from the original Ck-12 Biology Teacher’s Guide. Some of the questions and answers may not match up with the edited Guest Hollow book.

Do you offer a physical copy of this book or a PDF?

No, we don’t offer one. You can print sections of the book out for your student from the online web pages via a home printer, or you can save the sections as a PDF file and take that to your favorite printing company.

Some of our customers use The Homeschool Printing Company or Family Nest Printing. We don’t endorse any specific printing company. They are shared for informational purposes only.

How can I access the free biology workbook?

You can get the free biology workbook by clicking here:
You’ll need to add it to your cart and checkout to get the download. Once you’ve downloaded it, you can print it out as needed or all at once!

If you are using the FREE version of our biology curriculum, please consider donating to help support our efforts. We are so appreciative of your support! If you can’t donate, please spread the word about us!

Click here for more ways to say thanks!

Chapter 1
What is Biology?

This chapter provides an introduction to scientific investigations, methods, observations, and communication.

1.1 Science and the Natural World

1.2 Biology: The Study of Life

Chapter 2
The Chemistry of Life

This chapter covers matter, the significance of carbon, lipids, proteins, nucleic acids, amino acids, biochemical, and chemical properties and reactions.

Chapter 3

Cellular Structure and Function

This chapter introduces cell structure and function, features of prokaryotic, eukaryotic, plant, and animal cells. General structures and functions of DNA, RNA, protein, cell transport, and homeostasis.

3.1 Introduction to Cells

3.2 Cell Structures

3.3 Cell Transport and Homeostasis

Chapter 4

Photosynthesis and Cellular Respiration

This chapter introduces energy, glucose and ATP’s role, stages of photosynthesis, light reactions, the Calvin cycle, cellular respiration, glycolysis, the Krebs cycle, the electron transport chain, anaerobic and aerobic respiration, and fermentation.

4.1 Energy for Life

4.2 Photosynthesis: Sugar as Food

4.3 Powering the Cell: Cellular Respiration

4.4 Anaerobic Respiration

Chapter 5

The Cell Cycle, Mitosis, and Meiosis

This chapter covers cell division, the process of producing new cells, and sexual and asexual reproduction.

5.1 Cell Division and the Cell Cycle

5.2 Chromosomes and Mitosis

5.3 Reproduction and Meiosis

Chapter 6

Gregor Mendel and Genetics

This chapter covers Mendelian genetics, inheritance, probability, dominant, recessive, and sex-linked traits.

6.1 Mendel’s Investigations

6.2 Mendelian Inheritance

Chapter 7

Molecular Genetics: From DNA to Proteins

This chapter covers DNA, RNA, protein synthesis, mutation, and regulation of gene expression.

7.1 DNA and RNA

7.2 Protein Synthesis

7.3 Mutation

7.4 Regulation of Gene Expression

Chapter 8

Human Genetics and Biotechnology

This chapter covers the human genome and genetic diseases/disorders, including autosomal vs. sex-linked inheritance patterns, DNA technology, The Human Genome Project, and gene cloning.

8.1 Human Chromosomes and Genes

8.2 Human Inheritance

8.3 Biotechnology

Chapter 9


This chapter introduces Linnaean classification.

9.1 Classification

Chapter 10

Creationism vs. the Theory of Evolution

This chapter gives you a foundation to understand creationism vs. evolution.

10.1 Exposing the Flaws in Evolution

Chapter 11

The Principles of Ecology

This chapter covers ecology and its relationship to energy, ecosystems, and the water, carbon, and nitrogen cycles.

11.1 The Science of Ecology

11.2 Recycling Matter

11.3 Biomes

Chapter 12

Communities and Populations

This chapter covers communities as part of biotic ecosystems, populations: size, density, dispersion, and growth, biodiversity, natural resources, and climate change.

12.1 Community Interactions

12.2 Characteristics of Populations

Chapter 13

Microorganisms: Prokaryotes and Viruses

This chapter serves as an introduction to the specifics of prokaryotes and viruses, as well as the interactions between bacteria and other organisms.

13.1 Prokaryotes

13.2 Viruses

Chapter 14

Eukaryotes: Protists and Fungi

This chapter serves as an introduction to the Kingdom Protista, the three types of protists: animal-like, plant-like, and fungus-like protists, and the classification and ecology of fungi.

14.1 Introduction to Protists

14.2 Types of Protists

14.3 Introduction to Fungi

14.4 Ecology of Fungi

14.5 Protists, Fungi, and Human Disease

Chapter 15

Plant Classification

This chapter is an introduction to the plant kingdom and covers the four categories of plants: nonvascular plants, vascular plants, seed plants, and flowering plants.

15.1 Introduction to the Plant Kingdom

15.2 Four Types of Plants

Chapter 16

Plant Biology

This chapter discusses plant tissues, including roots, stems, leaves, and plant growth.

16.1 Plant Tissues and Growth

16.2 Plant Organs, Roots, Stems, and Leaves

16.3 Variation in Plant Life Cycles

16.4 Plant Features and Responses

Chapter 17

Introduction to Animals

This chapter gives an overview of animals, including invertebrates, discussing characteristics and classification.

17.1 Overview of Animals

17.2 Overview of Invertebrates

Chapter 18

From Sponges to Invertebrate Chordates

This chapter provides an overview of sponges, cnidarians, flatworms, and roundworms, discussing structure, function, reproduction, and ecology.

18.1 Sponges, Cnidarians, Flatworms, and Roundworms

18.2 Mollusks and Annelids

18.3 Arthropods and Insects

18.4 Echinoderms and Invertebrate Chordates

Chapter 19

From Fish to Birds

This chapter is an overview of vertebrates from fishes to birds covering their characteristics and classification.

19.1 Overview of Vertebrates

19.2 Fish

19.3 Amphibians

19.4 Reptiles

19.5 Birds

Chapter 20

Mammals and Animal Behavior

This chapter provides an overview of mammals covering mammalian traits, reproduction, and classification. Animal behavior is also discussed, including learning and communication, as well as migration, aggression, courtship, and mating.

20.1 Mammalian Traits

20.2 Reproduction in Mammals

20.3 Classification of Mammals

20.4 Overview of Animal Behavior


© CK-12 Foundation
Licensed under CK-12 Foundation is licensed under Creative Commons
Attribution Non Commercial 3.0 Unported (CC BY-NC 3.0)
• Terms of Use • Attribution
Changes/edits were made to the original ck12 biology text by Guest Hollow.
Changes are not endorsed by CK-12 in any way.