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biology definition

n., [baɪˈɑlədʒi]
Definition: scientific study of life

Biology Definition

Biology is the branch of science that primarily deals with the structure, function, growth, evolution, and distribution of organisms. As a science, it is a methodological study of life and living things. It determines verifiable facts or formulates theories based on experimental findings on living things by applying the scientific method. An expert in this field is called a biologist.

Some of the common objectives of their research include understanding the life processes, determining biological processes and mechanisms, and how these findings can be used in medicine and industry. Thus, biological research settings vary, e.g. inside a laboratory or in the wild.

Biology is a wide-ranging field. It encompasses various fields in science, such as chemistry, physics, mathematics, and medicine. Biochemistry, for instance, is biology and chemistry combined. It deals primarily with the diverse biomolecules (e.g. nucleic acids, proteins, carbohydrates, and lipids), studying biomolecular structures and functions. Biophysics is another interdisciplinary field that applies approaches in physics to understand biological phenomena. Mathematics and biology have also gone hand in hand to come up with theoretical models to elucidate biological processes using mathematical techniques and tools. Medical biology or biomedicine is another major integration where medicine makes use of biological principles in clinical settings. These are just a few of the many biology examples wherein its fundamental tenets are integrated into other scientific fields.


living things
Biology is the study of all living things. From top left to bottom right: archaeon, bacterium, protist, fungus, plant, and animal.
The term biology comes from the Greek βίος (bios), meaning “life” and from the Greek λογία (logia), meaning “study of”. Abbreviation: biol. Synonyms: biological science; life science.

Introduction to Biology

animal cell
A typical cell of an animal. Inside the cell are organelles (e.g. nucleus, mitochondrion, endoplasmic reticulum, and Golgi apparatus) and many other cytoplasmic structures.

A basic biology definition would be is that it is the study of living organisms. It is concerned with all that has life and living. (Ref.1) In contrast to inanimate objects, a living matter is one that demonstrates life. For instance, a living thing would be one that is comprised of a cell or a group of cells. Each of these cells can carry out processes, e.g. anabolic and catabolic reactions, in order to sustain life. These reactions may be energy-requiring. They are also regulated through homeostatic mechanisms. A living matter would also be one that is capable of reacting to stimuli, adapt to its environment, reproduce, and grow. The major groups of living things are animals, plants, fungi, protists, bacteria, and archaea. Biology studies their structure, function, distribution, evolution, and taxonomy.

Recommended: BLASTing through the kingdom of life – a guide for teachers, from Digitalworldbiology.com.

Modern Principles and Concepts of Biology

The fundamental principles of biology that are acceptable to this day include cell theory, gene theory, evolutionary theory, homeostasis, and energy.

Cell theory

Cell theory is a scientific theory proposed by the scientists, Theodor Schwann, Matthias Jakob Schleiden, and Rudolf Virchow. It is formulated to refute the old theory, Spontaneous generation. It suggests the following tenets: (1) All living things are made up of one or more cells, (2) the cell is the structural and functional unit, (3) cells come from a pre-existing process of division, (4) all cells have the same chemical composition, and (5) energy flow occurs within the cell. (Ref.2)

Gene theory

test cross
In Gene theory, the gene is the fundamental unit of heredity. In this chart (called Punnett Square), it shows how a particular phenotype of an offspring depends on the inherited alleles from the parents. In this example, the dominant trait (yellow color) is expressed on offspring inheriting the Y allele. In contrast, the offspring lacking the dominant allele and inherits yy will express the recessive trait (green color).

In Gene theory, the gene is considered as the fundamental, physical, and functional unit of heredity. (Ref.3) It is located on the chromosome and contains DNA. The gene stores the genetic code, i.e. a sequence of nucleotides that determines the structure of a protein or RNA. A gene is a unit of heredity because it is transmitted across generations. It is through which the phenotypic trait of an organism is based upon. Gregor Johann Mendel was one of the main pioneers that established the science of genetics. As such, he is regarded as the father of the said field. He was able to determine the occurrence of unit factors (now referred to as genes) that were passed down from one generation to the next. He described these unit factors as occurring in pairs. One of the pairs will be dominant over the other (recessive). He formulated the Mendelian laws to elucidate how heredity occurs. These laws include Law of Segregation, Law of Independent Assortment, and Law of Dominance. The inheritance pattern that follows these laws is referred to as Mendelian inheritance. Conversely, an inheritance pattern that does not conform to these laws is described as Non-Mendelian.

Evolutionary theory

mutation diagram
This diagram shows how mutation and selection work as key factors in evolution.

Evolution pertains to the genetic changes in a population over successive generations driven by natural selection, mutation, hybridization, or inbreeding. (Ref.4) Charles Darwin is one of the major contributors to the theory of evolution. He is known for his work Origin of Species by Natural Selection after his Beagle voyage. He was able to observe different plant and animal species. Based on his analysis, he postulated that living things have an inherent tendency to produce offspring of the same kind. Thus, the survival of the species becomes dependent on the available food and space. As a result, organisms compete as the carrying capacity of the habitat would not be able to sustain a massive population. (Ref.5) Survival or struggle for existence, thus, becomes an individual feat.


Homeostasis is the tendency of an organism to maintain optimal internal conditions. It entails a system of feedback controls so as to stabilize and keep up with the normal homeostatic range despite the changing external conditions. For instance, it employs homeostatic mechanisms to regulate temperature, pH, and blood pressure. The homeostatic system is comprised of three main components: a receptor, a control center, and an effector. The receptor of the homeostatic system includes the various sensory receptors that can detect external and internal changes. The information is sent to the control center to process it and to produce a signal to incite an appropriate response from the effector. The concept of homeostasis is credited to Claude Bernard in 1865.


In biology, energy is essential to drive various biological processes, especially anabolic reactions. Adenosine triphosphate (ATP) is the main energy carrier of the cell. It is released from carbohydrates through glycolysis, fermentation, and oxidative phosphorylation. Lipids are another group of biomolecules that store energy.



Importance of Biology

Biology is the scientific way to understand life. Knowing the biological processes and functions of life is essential to gain a deeper knowledge and appreciation in life. Furthermore, it opens an avenue of resources for use in medicine and industry. How a biological process proceeds, its regulatory systems, and its components can lead to better awareness. For example, conservation efforts could begin to save a species that has been classified as endangered, i.e. on the verge of extinction.


A specialist or an expert in the field of biology is called a biologist. Biologists look upon the biophysical, biomolecular, cellular, and systemic levels of an organism. They attempt to understand the mechanisms at play in various biological processes that govern life. They are also interested in coming up with innovations to create and improve life. Some of them have advocacies and are concerned with the conservation of species. Depending on the nature and objectives of their research, they may be found conducting research inside a laboratory. Others carry out their scientific pursuits outside, such as in diverse habitats where an organism or a population of organisms thrive.

The biological study can be traced back to early times. Aristotle, for instance, was a Greek philosopher in Athens known for his contributions to philosophy and biology. He was the first person to study biology systematically. Some of his popular works include the History of Animals, Generation of Animals, Movement of Animals, Parts of Animals. Much of his botanical studies, though, were lost. Because of his many pioneering studies, he is regarded by many as the “Father of Biology”.

At present, biologists are now seeking the potential use of biology in other fields, such as medicine, agriculture, and industry. One of the most recent breakthroughs is CRISPR — a gene-hacking tool used by scientists to splice specific DNA targets and then replace them with a DNA that would yield the desired effect. One of its promises is that it can correct physiological anomalies due to mutated or defective gene mutations. (Ref.6)

Authors can now submit preprints to bioRxiv — an online archive and distribution service for preprints in the life sciences. More details here: BioTechniques Welcomes Preprints – BioTechniques (BioTechniques: https://www.biotechniques.com/general-interest/biotechniques-welcomes-preprints/).

Branches of Biology

Biology encompasses various sub-disciplines or branches. Some of the branches of biology are as follows:

  • Anatomy – the study of the animal form, particularly the human body
  • Astrobiology – the branch of biology concerned with the effects of outer space on living organisms and the search for extraterrestrial life
  • Biochemistry – the study of the structure and function of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules, and of their functions and transformations during life processes
  • Bioclimatology – a science concerned with the influence of climates on organisms, for instance, the effects of climate on the development and distribution of plants, animals, and humans
  • Bioengineering – or biological engineering, a broad-based engineering discipline that deals with bio-molecular and molecular processes, product design, sustainability, and analysis of biological systems
  • Biogeography – a science that attempts to describe the changing distributions and geographic patterns of living and fossil species of plants and animals
  • Bioinformatics – information technology as applied to the life sciences, especially the technology used for the collection, storage, and retrieval of genomic data
  • Biomathematicsmathematical biology or biomathematics, an interdisciplinary field of academic study which aims at modeling natural, biological processes using mathematical techniques and tools. It has both practical and theoretical applications in biological research
  • Biophysics – or biological physics, interdisciplinary science that applies the theories and methods of physical sciences to questions of biology
  • Biotechnology – applied science concerned with biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use
  • Botany – the scientific study of plants
  • Cell biology – the study of cells at the microscopic or at the molecular level. It includes studying the cells’ physiological properties, structures, organelles, interactions with their environment, life cycle, cell division, and apoptosis
  • Chronobiology – a science that studies time-related phenomena in living organisms
  • Conservation Biology – concerned with the studies and schemes of habitat preservation and species protection for the purpose of alleviating extinction crisis and conserving biodiversity
  • Cryobiology – the study of the effects of low temperatures on living organisms
  • Developmental Biology – the study of the processes by which an organism develops from a zygote to its full structure
  • Ecology – the scientific study of the relationships between plants, animals, and their environment
  • Ethnobiology – a study of the past and present human interactions with the environment, for instance, the use of diverse flora and fauna by indigenous societies
  • Evolutionary Biology – a subfield concerned with the origin and descent of species, as well as their change over time, i.e. their evolution
  • Freshwater Biology – a science concerned with the life and ecosystems of freshwater habitats
  • Genetics – a science that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms
  • Geobiology – a science that combines geology and biology to study the interactions of organisms with their environment
  • Immunobiology – a study of the structure and function of the immune system, innate and acquired immunity, the bodily distinction of self from non-self, and laboratory techniques involving the interaction of antigens with specific antibodies
  • Marine Biology – the study of ocean plants and animals and their ecological relationships
  • Medicine – the science which relates to the prevention, cure, or alleviation of disease
  • Microbiology – the branch of biology that deals with microorganisms and their effects on other living organisms
  • Molecular Biology – the branch of biology that deals with the formation, structure, and function of macromolecules essential to life, such as nucleic acids and proteins, and especially with their role in cell replication and the transmission of genetic information
  • Mycology – the study of fungi
  • Neurobiology – the branch of biology that deals with the anatomy, physiology, and pathology of the nervous system
  • Paleobiology – the study of the forms of life existing in prehistoric or geologic times, as represented by the fossils of plants, animals, and other organisms
  • Parasitology – the study of parasites and parasitism
  • Pathology – the study of the nature of the disease and its causes, processes, development, and consequences
  • Pharmacology – the study of preparation and use of drugs and synthetic medicines
  • Physiology – the biological study of the functions of living organisms and their parts
  • Protistology – the study of protists
  • Psychobiology – the study of mental functioning and behavior in relation to other biological processes
  • Toxicology – the study of how natural or man-made poisons cause undesirable effects in living organisms
  • Virology – the study of viruses
  • Zoology – The branch of biology that deals with animals and animal life, including the study of the structure, physiology, development, and classification of animals
  • Ethology – the study of animal behavior
  • Entomology – the scientific study of insects
  • Ichthyology – the study of fishes
  • Herpetology – the science of reptiles and amphibians
  • Ornithology – the science of birds
  • Mammalogy – the study of mammals
  • Primatology – the science that deals with primates

Human Biology – Definition

Human biology is the branch of biology that focuses on humans in terms of evolution, genetics, anatomy and physiology, ecology, epidemiology, and anthropology. It can be a subfield of Primatology since humans belong to the group of primates, particularly of the family Hominidae (tribe Hominini). Since human biology is a course that deals mainly with humans, it is a viable option for use as a preparatory course in medicine.

Try to answer the quiz below to check what you have learned so far about biology.


Choose the best answer. 

1. What is biology?
2. It applies approaches in physics so as to understand biological phenomena
3. A principle in biology stating that all living things are made up of a cell or group of cells
4. A concept in biology that is defined as the tendency of an organism to maintain optimal internal conditions
5. A biological energy

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See Also


  1. INTRODUCTION: THE NATURE OF SCIENCE AND BIOLOGY. (2019). Retrieved September 12, 2019, from Estrellamountain.edu website: http://www2.estrellamountain.edu/faculty/farabee/biobk/biobookintro.html
  2. 4.1C: Cell Theory. (2019, September 9). Retrieved from Biology LibreTexts website: https://bio.libretexts.org/Bookshelves/Introductory-and-General-Biology/Book:-General-Biology-(Boundless)/4:-Cell-Structure/4.1:-Studying-Cells/4.1C:-Cell-Theory
  3. Rheinberger, H.-J., Müller-Wille, S., & Meunier, R. (2015). Gene (Stanford Encyclopedia of Philosophy). Retrieved September 12, 2019, from Stanford.edu website: https://plato.stanford.edu/entries/gene/
  4. A brief history of evolution. (2019). Retrieved from OpenLearn website: https://www.open.edu/openlearn/history-the-arts/history/history-science-technology-and-medicine/history-science/brief-history-evolution
  5. 3. Theories of Evolution. (2010). Retrieved from BIOLOGY4ISC website: https://biology4isc.weebly.com/3-theories-of-evolution.html
  6. Gonzaga, M. V. (2019, August 21). CRISPR DIY – biohacking genes at. Retrieved from Biology Blog & Dictionary Online website: https://www.biologyonline.com/crispr-diy-biohacking-genes-at-home/

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