What is biology?

Biology is everywhere around us. From the smallest cells to the whole of our huge planet — everything is connected. Read on and discover what biology actually is. You can also learn some of the most important words from the fascinating world of biology.

Here is your toolbox – when you really want to understand biology.



All life — also referred to as organisms — is constructed from cells. Either from a single cell or from multiple cells, which adjoin each other. As you know, people have organs. It is the same with larger cells, which have organelles with various functions that ensure the cell can live and carry out its work. In biology, there are some simple cells that have no cell nucleus — we call them prokaryotes — and also the more advanced forms of cells which are known as eukaryotes. We humans and all other animals are built up from billions of eukaryotic cells.

The central dogma

The central dogma is one of the most fundamental theories in biology. DNA is found in our cells, and it codes for and defines all life. The four building blocks on which all life is constructed — nucleotides — are located together in long chains and contain all the information needed for creating life. The DNA in the cell is converted to RNA, which acts as a sort of cook book recipe that determines which proteins the cell will produce. This translation from DNA to RNA to protein takes place constantly in all cells and ensures that life is maintained.

The cell’s building blocks

You know what the cell’s various building blocks are. They are carbohydrates, proteins and fats, which serve as food for cells as well as humans. They are vital for maintaining various functions in the cell.

1) Carbohydrates, such as sugar or starch, can be broken down by the cell and act as an energy source.

2) Proteins are long chains of 22 different amino acids which the cell, according to the central dogma, links together to form enzymes and tissue.

3) Fats also contain a large amount of energy and help to maintain various functions in the cell. Fats are found particularly in the cell membrane.


Enzymes are proteins that enable a huge number of biochemical processes to take place. It is enzymes that break down the food in your stomach. It is also enzymes that copy DNA when the cell divides. And, they produce the hormones which regulate your mood. In short, enzymes are the molecules which ensure that all the organism’s functions are carried out. The fastest enzyme can produce a million molecules of CO2 per second!


An ecosystem is an environment occupied by lots of different organisms — big and small — that live together. It also includes all the non-living elements, such as water, rock and buildings. Examples include rainforest, desert and prairie ecosystems. The majority of ecosystems have a food chain and all the organisms are typically part of this in one way or another.


New life is created by reproduction! One cell becomes two, or parents have offspring. All life on Earth reproduces itself — otherwise life would cease. Bacteria and other unicellular organisms are often created by asexual reproduction, which involves a cell dividing into two cells that have exactly the same genetic material. By contrast, many animals and plants multiply by sexual reproduction, in which case the new individual acquires genetic material from two parents. Reproduction can in some ways be regarded as the raison d’être for all life!


Bacteria are small living unicellular organisms that are found everywhere: in the air, in the soil and in food. Even in the deepest oceans and the driest deserts, and in the hottest of sources, bacteria or other unicellular organisms called archaea have been found. Yes, even our bodies are full of bacteria! In fact, of all the cells in our bodies, only 10% are human cells — the rest are bacteria. Fortunately, by far the majority of these bacteria are harmless or actually good for us, though a few can cause disease. These are termed pathogenic bacteria.


Animals come in all sorts of shapes, colors and sizes. Everything from small insects to huge whales. Animals are multicellular organisms that are built up from eukaryotic cells. We humans are also animals. Through millions of years of evolution, animals have developed and adapted to survive and reproduce in their various niches on the planet. All animals are what we call heterotrophic, which means that they obtain their energy from the food they eat. This is because animals burn this food in the body; all animals therefore need oxygen to survive.


Plants are built up from many eukaryotic cells — just like animals. But in contrast to animals, plants do not obtain their energy by eating food. So we call plants autotrophic. They obtain their energy from the sun’s rays and use the light and carbon dioxide from the atmosphere to produce oxygen and energy in order to grow. This is called photosynthesis. Many plants produce fantastic, beautiful flowers. The flowers act as the plant’s sex organ and mediate the merging of genetic material from two plants, thereby creating a new plant.


Fungi are in many ways a mixture of animals and plants. Although fungi may be more reminiscent of plants because they cannot move, they actually have most in common with animals. They are heterotrophic and therefore obtain their energy by breaking down dead organic matter, just as we eat food. Although you might associate fungi with mushrooms, the largest part of fungi is actually a network of threadlike roots under the ground, referred to as a fungal mycelium. The mushroom can be said to function just like a plant’s flower.


Many cells and enzymes require specific conditions to function optimally. This is why it’s important that organisms maintain an internal equilibrium, so that parameters such as temperature, salt concentrations and pH do not fluctuate too much. This equilibrium is called homeostasis. Fortunately, the body and the cells have developed efficient and complex mechanisms to ensure that they are constantly in homeostasis. For example, blood circulation ensures that all cells constantly have the oxygen and nutrients they require, while at the same time the blood transports waste substances away from the cells.


Although it can be difficult to understand, humans are also just animals, and are a result of biology and millions of years of evolution. Your body consists of circa 30 trillion — that is to say, 30 thousand billion — cells, all of which are performing their specific tasks. This is all controlled by complex systems in which the cells communicate with each other via biochemical processes. These ensure that the body is constantly in balance — that is, in homeostasis — and reacts to all internal and external stimuli. An average computer can cope with about 100 million instructions per second; the brain, on the other hand, deals with the equivalent of 100 million billion billion… Biology is amazing.