Introduction to biology

Introduction to Biology

Biology is the study of life. As humans are living things, we have a natural sense of curiosity and affection towards life and how has come to be.

The study of biology incorporates everything imaginable related to the life on Earth. It can be very broad and focus on details regarding the entire planet or it may be very specific and study microscopic structures such as bacteria or DNA.

Studying living things, called organisms, takes us all around the world, from the most productive tropical rain forests to the hostile lands of Antarctica or the deepest oceanic basins.

Although our knowledge of the world around us is constantly changing, there are a few basic principles of biology that should hopefully remain useful for many years to come. Most biological study is built on the foundations of five universally recognized truths. These are:

  1. Stick insectCells are the basic unit of life.
  2. Genes are the basic units for passing traits from parent to offspring.
  3. Evolution by natural selection is the process that has led to the great diversity of species on Earth.
  4. Living things maintain the environment within their cells and bodies.
  5. Living things have the ability to acquire and transform energy.

As you can imagine and may very well know, biology is a massive field of study. It is constantly developing as biologists around the world are completing research and taking our understanding of life to new levels.

Everyday new information is published in different fields of biology and it is near on impossible for one person to keep up-to-date with every topic related to biology. However, everyone has to start somewhere and studying biology can enlighten your understanding of the world around you.


Life is a phenomenon existing (as far as we know) only on Earth. ‘Life’ is the title given to separate the things that are able to function by themselves from material objects such as rocks and water.

Sumatran tigerAll of the living things on Earth are collectively known as organisms. There are a range of functions that are essential for something to be considered an organism. These include movement, respiration, sensitivity, growth, reproduction, the release of wastes and the consumption of food.

Life has evolved into an incredible array of shapes and forms. Humans belong to the most advanced group of organisms, the animals. Other higher-level organisms include plants and fungi.

More primitive life forms include microscopic groups such as bacteria and archaea. Viruses are an unusual group because they are unable to reproduce without the use of a host cell. As such, viruses are classed by some biologists to be living and by others to be not.


All living things are built from microscopic structures called cells. One cell has the potential to sustain life and is the simplest structure capable of doing so.

Plant cellsAlthough life evolved into multi-cellular organisms a long time ago, the majority of life on Earth still remains as single-celled organisms. Bacteria, archaea, protists, and many fungi have only one cell and are able to survive and reproduce in a huge array of ways that puts plants and animals to shame.

Cells are typically divided into two main categories: prokaryotic cells and eukaryotic cells. Prokaryotic cells are found only in microscopic organisms such as bacteria and archaea. Eukaryotic cells are found in more advanced organisms such as animals, plants, and fungi.

The main difference between the two types of cells is that eukaryotic cells have a nucleus which contains the cell’s DNA and has specialized structures called organelles. Organelles perform specific functions such as photosynthesis and protein production. In prokaryotic cells, the DNA isn’t encapsulated within a nucleus and organelles are missing.

The cells from one organism to the next always varies but they do often have many similarities. Almost all cells contain DNA, are surrounded by a membrane, and perform similar functions such as respiration and the production of proteins.


GenesGenes are the basic unit for heredity. They contain all the information required to keep an organism alive. When organisms reproduce, the information from genes is passed from parent to offspring. The genes that are passed from parent to offspring then provide the information to cells to keep the new organism alive. Genes are the reason why children look similar to their parents.


The theory of evolution by natural selection gives by far the best explanation for the huge diversity of species on Earth. The process of natural selection has been sculpting life for over 4 billion years and is the cornerstone of modern biology. The natural selection of useful traits from generation to generation drives the evolution of species over long periods of time.

With the help of genetic mutations, evolution has driven the development of life, capable of thriving in almost any environment on Earth. The process of evolution is visible in all aspects of life. Obvious similarities in structure and function of different species are hard to ignore and the collection of evidence supporting the theory of evolution has become undeniable.


Homeostasis is the act of maintaining a relatively constant internal environment within an organism’s cells. Cells function most efficiently in a certain range of conditions and as the environment changes around them, they constantly work to keep their internal environment in an optimal condition. Cells are working to maintain factors such as the concentrations of water, salt and sugar, the temperature within the cell, and oxygen concentrations.

Fields of biology

RobinThere is a huge array of sub-disciplines or branches of biology; all up more than 60. Many have been around for hundreds of years, whilst others are far newer and are often developing very rapidly.

Fields of study such as evolution, ecology, and genetics are themselves very broad topics and contain many specializations within each field. For example, an ecologist, who looks at how organisms interact with each other and the environment, might specialize in marine ecology, population ecology, plant ecology or freshwater ecology.

As biology is such a broad field of study, the work from one biologist to another may be completely different. An agriculturalist for example, who is interested in the production of crops, will focus on very different content to that of an ethologist, who studies the behavior of animals. In order to be a well-rounded biologist, however, it is good to have an understanding of the basics of the broad fields within biology.

Last edited: 21 August 2018

Want to learn more?


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