Table of Contents
What This Course Is About
Biology is the science that studies living organisms and their interactions with each other and with their environment. In this course, “living organisms” includes everything from bacteria and fungi to plants, animals, and humans.
This opening chapter has three main goals:
- To clarify what it means to call biology a science.
- To outline what kinds of questions biology asks about living things.
- To show briefly how biological knowledge affects everyday life and society.
Details about the history of biology, subdisciplines, cells, evolution, and so on will each be treated in their own chapters later.
Biology as a Natural Science
Biology belongs to the natural sciences, alongside physics, chemistry, and earth sciences. All natural sciences share some common features:
- They investigate phenomena in the natural world.
- They build explanations based on observations, experiments, and logical reasoning.
- Their knowledge is always open to testing, revision, and improvement.
What is specific to biology is its focus on life. It asks questions such as:
- What distinguishes living beings from non-living matter?
- How do living organisms obtain and use energy?
- How do traits pass from one generation to the next?
- How do populations change over long periods of time?
- How do organisms interact within ecosystems?
Biology uses methods shared with other sciences—such as measurement, modeling, and experimentation—but often applies them to complex, variable, and historically shaped systems (organisms and ecosystems), which makes many biological questions probabilistic rather than strictly deterministic.
Levels at Which Biology Studies Life
Living organisms can be studied at many levels of organization. Later chapters will treat these levels in detail; here, we only sketch how they relate to each other and to the scope of biology as a science:
- Molecular level – atoms, small molecules, DNA, proteins
- Cellular level – cell structure and function
- Tissue and organ levels – groups of cells with shared tasks
- Organism level – the entire individual living being
- Population level – groups of individuals of the same species
- Community and ecosystem levels – many species interacting, plus the physical environment
- Biosphere level – the sum of all ecosystems on Earth
Different biological subdisciplines concentrate on different levels, but they are interconnected: processes at the molecular level influence whole organisms and even ecosystems, and ecological conditions feed back on organisms and their genes over evolutionary time.
What Makes Biology Scientific?
Several features make biology a systematic, scientific way of understanding life:
Empirical Foundation
Biology relies on empirical evidence—data gained through observation and experiment:
- Observational studies: watching animal behavior, recording plant growth, documenting disease spread.
- Experimental studies: changing one condition (for example, nutrient supply or temperature) and measuring the effect on living systems.
Raw observations alone are not yet science; biology turns them into science by organizing them, looking for patterns, and testing explanations.
Use of Hypotheses and Theories
Biologists:
- Formulate hypotheses – clear, testable statements about how something in living systems works.
- Design ways to test these hypotheses (experiments, field studies, models).
- Evaluate whether the data support, contradict, or refine the hypotheses.
When many related hypotheses are repeatedly supported and knit together into a coherent explanation, they form a scientific theory (for example, the theory of evolution by natural selection). In biology, a “theory” is not a guess but a well-tested framework that explains diverse observations.
Quantification and Modeling
Where possible, biology uses quantitative measurements and mathematical models:
- Counting individuals in a population
- Measuring rates (growth rates, heart rates, metabolic rates)
- Using equations to model population dynamics or energy flow
However, biology also makes careful use of qualitative descriptions when phenomena are not easily expressed in numbers (for example, describing behaviors or structures), and then seeks ways to relate these qualitative aspects to measurable quantities.
Provisional and Self-Correcting Nature
Because living systems are complex and variable, biological explanations are always provisional:
- New methods (for example, DNA sequencing, advanced microscopy) can reveal previously unseen details.
- New data can confirm or challenge existing ideas.
This self-correcting process is a fundamental feature of biology as a science: certainty is always relative to available evidence and methods.
The Scope of Questions in Biology
While later chapters explore specific topics, this course as a whole will address questions that fall into a few broad categories:
Structure and Function
- How are organisms built?
- How do the parts of cells, organs, and organ systems contribute to their function?
Here biology connects closely with chemistry and physics, because understanding structure (for example, of proteins or membranes) often requires understanding the underlying physical and chemical principles.
Regulation and Homeostasis
- How do organisms keep internal conditions within usable limits, despite changing environments?
- How do feedback mechanisms work in cells, organisms, and ecosystems?
This includes coordination by nerves and hormones, regulation of gene activity, and dynamic balances in ecosystems.
Energy and Matter
- How do living organisms obtain energy and materials?
- How do they convert energy and cycle matter?
Biology examines how life uses chemical energy and how matter (such as carbon or nitrogen) circulates through food webs and ecosystems.
Information and Heredity
- How is biological information stored and transmitted?
- How does this information guide development and function?
This includes genes, DNA, RNA, and their roles in inheritance and protein production, as well as larger-scale patterns of inheritance in families and populations.
Development and Reproduction
- How do individual organisms grow and develop from a single cell?
- How do organisms reproduce and give rise to the next generation?
Biology investigates how stable structures emerge from simple beginnings and how reproduction maintains or modifies traits across generations.
Evolution and Diversity
- How did the vast variety of life on Earth arise?
- How are organisms related to each other through common ancestry?
Evolution gives biology its historical dimension, explaining both unity (shared features across all life) and diversity (the enormous range of forms and lifestyles).
Behavior and Interactions
- How do organisms respond to stimuli and interact with each other?
- How do these interactions influence survival and reproduction?
This includes everything from simple reflexes to complex social behaviors in animals, including humans.
Why Biology Matters for Everyday Life
Biology is not only about understanding nature for its own sake; it also has practical and social significance:
- Medicine and health – understanding pathogens, immunity, genetics, and physiology underlies diagnosis, treatment, and prevention of disease.
- Agriculture and food – crop breeding, pest control, soil biology, and animal husbandry depend on biological knowledge.
- Biotechnology – industrial enzymes, genetically modified organisms, and modern pharmaceuticals are based on biological principles and methods.
- Environmental issues – climate change, species extinction, pollution, and sustainable resource use all involve biological systems at large scales.
- Ethical and social questions – topics like genetic testing, reproductive technologies, conservation, and animal welfare all require biological understanding, but also go beyond biology into philosophy, law, and politics.
Understanding biology as a science equips you not only to grasp how living systems work, but also to critically evaluate biological claims in public debates, media, and everyday decisions.
What to Expect Next
In the following chapters under “Biology as the Science of Living Organisms,” you will:
- Examine the role biology plays in modern human life in more detail.
- Learn about the characteristic features that distinguish living things from non-living matter.
- Explore how living systems are organized, from small to large scales.
- See how biology developed historically and how it connects to other fields of knowledge.
Together, these will deepen the initial picture presented here: biology as a systematic, evidence-based, and evolving effort to understand life in all its forms and contexts.