Welcome ………. Topic Index >

Virtual Biology Textbook

See About Our Virtual Textbooks for disclaimer and explanation. Use cK-12 Biology flexbook (pdf format) as an additional reference source. Explore NGSS Life Science Phenomenon.


Biology 10 Student Expectations

Students are expected to follow course guidelines and actively participate in assigned work. Appropriate classroom decorum, reasonably focused effort, and combinations of individual-work and team-collaborations are important aspects of this curriculum. (topic)

The Big Picture

Biology 11 What is Biology?

Biology is a natural science. Biology is the scientific study of living things – one of several of the Life Sciences. Biology is a natural science involving the study of life and living organisms. (topic)

Biology 12 Scientific Method and Safety

The scientific method has been used in natural science since the 17th century. It consists of systematic observation, measurement, and experiment, testing, and modification of hypotheses. High school students are expected to be familiar with the scientific method and its applications. (topic)

Biology 13 Connections Across Content

There are overlapping concepts between biology, chemistry, physics, mathematics and other subjects. Throughout this curriculum, students are encouraged to identify connections of concepts to things they already know … as well as connections to things-learned in previous science classes or other subject areas. (topic)

Cell Biology

Biology 14 Cell Organization

Cells are the basic unit of life. In biology, the cell is the basic structure of organisms. All cells are made by the division of other cells. (topic)

Biology 15 Plant Cells

Plant cells share similarities with animal cells but also have distinct features such as a cell wall. Like all organisms, plants have cells. Plant cells have a nucleus with chromosomes and DNA, and they have mitochondria. Those are common to all eukaryote cells. But in some ways, plant cells are different from animal cells and the cells of other eukaryotes. (topic)

Biology 16 Prokaryotic and Eukaryotic Cells

Prokaryotes are unicellular organisms that lack organelles or other internal membrane-bound structures. Prokaryotic cells preceded eukaryotic cells on the evolutionary timeline. Eukaryotes are organisms whose cells have a nucleus enclosed within membranes. (topic)

Cell Cycle

Biology 17 Mitosis and Cytokinesis

Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth. Cytokinesis is the cytoplasmic division of a cell at the end of mitosis, bringing about the separation into two daughter cells. (topic)

Biology 18 DNA and Heredity

DNA stands for  deoxyribonucleic acid. DNA is a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information. Heredity is the passing on of physical or mental characteristics genetically from one generation to another. (topic)

Biology 19 Genes Genetics and Chromosomes

Genetics is the study of heredity and the variation of inherited characteristics. Chromosomes are a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. (topic)


Biology 21 Organization of Living Things I

There are many different animal classes and every animal in the world belongs to one of them. The five most well known classes of vertebrates (animals with backbones) are mammals, birds, fish, reptiles,amphibians. (topic)

Biology 22 Organization of Living Things II

The highest level of organization for living things is the biosphere; it encompasses all other levels. The biological levels of organization of living things arranged from the simplest to most complex are: organelle, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystem, and biosphere. This topic focuses on “population” – (a group of organisms of one species that interbreed and live in the same place at the same time). Variation and distribution of expressed traits in a population can be described through statistics and probability. (topic)

Biology 23 Interdependence of Living Things

In biology, students discover there is a great deal of interdependence between plants and animals. Inter- means “between,” so interdependence is dependence between things. Scientists often use interdependence to describe complex systems. (topic)

Evolution and Natural Selection

Biology 24 Theory of Evolution

The theory of evolution by natural selection, first formulated in Darwin’s book “On the Origin of Species” in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits. (topic)

Biology 25 Protist Evolution

Protists evolved from prokaryotes, eventually giving rise to the entire line of eukaryotes that exists today. The first protists originated around 1.7 billion years ago from simple societies of prokaryotic cells. (topic)

Biology 26 Adaptations and Natural Selection

An adaptation is a trait or behavior that helps an organism survive and reproduce. Traits are genetic differences that occur in a species. Traits are developed as a species adapts to its environment. (topic)

Biology 27 Populations and Genetics

Population genetics seeks to understand how and why the frequencies of alleles and genotypes change over time within and between populations. It is the branch of biology that provides the deepest and clearest understanding of how evolutionary change occurs. Population genetics is particularly relevant today in the expanding quest to understand the basis for genetic variation in susceptibility to complex diseases. (topic)

Biology 28 Use of a Light Microscope Lab

A light microscope (LM) is an instrument that uses visible light and magnifying lenses to examine small objects not visible to the naked eye, or in finer detail than the naked eye allows. Light microscopes date at least to 1595, when Zacharias Jansen (1580–1638) of Holland invented a compound light microscope, one that used two lenses, with the second lens further magnifying the image produced by the first. (topic)

Evolution and Animals

Biology 31 Darwin, Evolution and Fossils

Fossils are the preserved remains or traces of animals, plants, and other organisms from the past. Fossils range in age from 10,000 to 3.48 billion years old. The observation that certain fossils were associated with certain rock strata led 19th century geologists to recognize a geological timescale. Though the fossil record does not include every plant and animal that ever lived, it provides substantial evidence for the common descent of life via evolution. The fossil record is a remarkable gift for the study of nature. (topic)

Biology 32 Animal Characteristics

Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, reproduce sexually, and grow from a hollow sphere of cells (the blastula) during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres (110 ft) and have complex interactions with each other and their environments, forming intricate food webs. The study of animals is called zoology. (topic)

Biology 33 Animal Behaviors

The term instinct is commonly thought of as describing behavior that is pre-programmed and requires no thought. An instinctive response happens automatically and is the same across all individuals of a species. While this seems like a clearly defined category, not all behavior is so cut and dry. Many behaviors have both genetically pre-programmed and learned aspects. The degree to which certain behaviors, especially in humans, are pre-determined is often a subject of intense debate. Whether the behavioral response to a given stimulus is learned, genetic, or both is the subject of study in the field of behavioral genetics. (topic)

Using Science Models

Biology 34 Science Observation and Measure

The scientific method is reliant on unbiased observation and accurate and repeatable measurement of those observations. In everyday life, observing ,may be simply sitting still to watch and listen. In contrast, observing can be very active in science. Scientists and science students must continually make decisions how best to examine an object or situation. For example, decisions might include whether to touch or smell something in an experiment. Observation alone is not sufficient to evaluate a given experiment. Measuring those observations is also important. A measurement is quantitative because it includes a number. However, a number alone is not a measurement. A measurement must also include a unit. For example, temperature can be measured using several scales. (topic)

Biology 35 Science Models

In science, a model is a representation of an idea, an object, a process or a system. Models describe and explain phenomena that cannot be directly experienced. There are three main types of science models: physical, mathematical, and conceptual. Physical models are often the easiest to understand (the world globe is an example of a physical model). Mathematical models are also common in science (models predicting the weather, or the next solar eclipses are examples of math models). Conceptual models are often presented in the form of a diagram which shows a set of relationships (a diagram illustrating cell-division is an example of a conceptual model). Scientific knowledge is examined and communicated through the use of models. Models help scientists define, examine, revise, and improve their hypotheses, theories, and laws. (topic)

Biology 36 Interpretation and Communication

The last step of most scientific investigations is reporting the results. When scientists communicate their findings, they add to the body of scientific knowledge, and that’s how science advances. When scientists communicate about their research, they may also get useful feedback from other scientists. For example, comments from other scientists might help them improve their research design or interpret their findings in a different way. Other scientists can also repeat the research to see if they get the same results. A typical scientific sequence is to measure and observe, create a model of the information, then interpret and communicate the results. (topic)

Lab Dissection

Biology 37 Dissection Preparation

One reason frogs are often chosen to be dissected is that their bodies provide a good overview of the organ systems of a complex living thing. The organs present in a frog, and the way they are laid out in the body, are similar enough to humans to provide insight for students about how their bodies work. Frogs and humans each possess a circulatory system. A difference though is that frogs have a three-chambered heart, with two atria and one ventricle compared to the human’s two atria and two ventricles. Other similarities between frogs and humans are the digestive and respiratory systems. (topic)

Biology 38 Dissection in Lab

Dissecting a frog is a common and important experience in introductory biology or anatomy. Although students may feel intimidated at the thought of dissecting an animal, the learning experience is often profound. Most frog dissection labs involve a basic identification procedure. Students are required to open the frog, identify the basic organs and systems of the frog, explore the anatomy of the animal, and fill out a short lab report to accompany the project. For the most part, dissection specimens are sterilized and safe, but it’s still very important to keep hands, eyes, and mouth free of the formaldehyde used to preserve the frogs for dissection. (topic)

Sub-Discipline Connections

Biology 41 Fields in the Life Sciences

The life sciences are helpful in improving the quality and standard of life. They have applications in health, agriculture, medicine, and the pharmaceutical and food science industries. There is considerable overlap between many of the topics of study in the life sciences. Anatomy studies form and function, in plants, animals, and other organisms, or specifically in humans. Botany is the study of plants. Ethology is the study of animal behavior. And microbiology is the study of microscopic organisms (microorganisms) and their interactions with other living organisms. These are just a few out of several dozen major branches of biology. (topic)

Biology 42 Physiology and the Human Body

Physiology is a sub-discipline with the life sciences. It is the study of the functioning of living organisms and the organs and parts of living organisms. Physiology is the scientific study of normal mechanisms, and their interactions, which work within a living system. As a sub-discipline of biology, its focus is in how organisms, organ systems, organs, cells, and biomolecules carry out the chemical or physical functions that exist in a living system. (topic)

Biology 43 Ecology and Sustainable Development

Ecology is study of the interactions of living organisms with one another and with the non-living elements of their environment. Objects of study include interactions of organisms with each other and with abiotic components (physical rather than biological; not derived from living organisms) of their environment. Topics of interest include the biodiversity, distribution, biomass, and populations of organisms, as well as cooperation and competition within and between species. An important focus for ecologists is to improve the understanding of how biodiversity affects ecological function. (topic)

Deeper Look

Biology 44 Deep Dive – the Cell

Cell biology is the study of the cell as a complete unit, and the molecular and chemical interactions that occur within a living cell. Also known as cytology. Cell biology is concerned with the physiological properties, metabolic processes, signaling pathways, life cycle, chemical composition and interactions of the cell with their environment. It is essential for research in bio-medical fields such as cancer, and other diseases. Research in cell biology is closely related to genetics, biochemistry, molecular biology, immunology, and developmental biology. (topic)

Biology 45 Deep Dive – Heredity

Genetics is the study of genes and heredity. The discoverer of genetics is Gregor Mendel, a late 19th-century scientist and Augustinian friar. Mendel studied “trait inheritance”, patterns in the way traits are handed down from parents to offspring. He observed that organisms (pea plants) inherit traits by way of discrete “units of inheritance”. This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene. (topic)

Biology 46 Deep Dive – Biological Diversity

Biodiversity generally refers to the variety and variability of life on Earth. Biodiversity typically measures variation at the genetic, the species, and the ecosystem level. Terrestrial (land) biodiversity tends to be greater near the equator, which seems to be the result of the warm climate. Biodiversity is not distributed evenly on Earth, and is richest in the tropics. Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity. (topic)

Year End Review

Biology 47 Scientific Inquiry

Scientific inquiry and the scientific method are similar concepts – but not the same thing. The National Science Education Standards defines scientific inquiry as “the diverse ways in which scientists study the natural world and propose explanations based on the evidence derived from their work. Scientific inquiry also refers to the activities through which students develop knowledge and understanding of scientific ideas, as well as an understanding of how scientists study the natural world.” One way to describe the relationship is that the scientific method is the backbone of all rigorous scientific inquiry. NSTA (National Science Teacher’s Association) advocates use of scientific inquiry as part of the Next Generation Science Standards (NSTA 2016). These ideas include (1) using STEM practices to actively engage students in science learning (2) integrating these practices with core ideas, and (3) motivating students through their intrinsic interests to explain natural phenomena and design solutions to problems. (topic)

Biology 48 Organisms and Living Systems

The definition of life is controversial. The current definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve. Viruses are an example of a borderline case. For many years, science considered viruses as sort of non-living poison. Life is a characteristic that distinguishes physical entities that do have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate. Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. The criteria can at times be ambiguous and may or may not define viruses, viroids, or potential synthetic life as “living”. (topic)

Biology 49 Year-End Capstone

Biology has always been the study of life, but our knowledge of living things and our use of technology to study them is always changing. Earth is home to an incredible diversity of life – where all organisms share certain characteristics. Our biology topics introduce and emphasize the unifying themes of biology: (1) All levels of life have systems of related parts. (2) Structure and function are related in biology. (3) Organisms must maintain homeostasis to survive in diverse environments. (4) Evolution explains the unity and diversity of life. Our first topic summarize the big picture of biology and its relationships to other natural sciences. Important concepts such as the cell cycle, classifications of living things, and an introduction to the theory of evolution and natural selection are covered. Remaining topics provide deeper coverage of evolution and animals, the use and application of scientific models, lab dissection, and a cursory look at specialized fields of biology such as ecology, physiology, and cytology. All topics are presented within the context of 21st Century skills and concepts of general scientific inquiry. (topic)

This web site provides free-to-use science curriculum for high school teachers, students, and parent-guardians. Quickly scan available topics for biology, chemistry, earth science, physical science. Discover more about John Honeycutt, creator of Honeycutt Science.

About us ……… Terms of use