Biology

Biology is the scientific study of life and living organisms, spanning everything from molecules inside a single cell to the interactions of whole ecosystems. All living things share certain features: they are made of cells, use energy through metabolism, grow, respond to their surroundings, reproduce and pass on hereditary information. The field is commonly divided into sub-disciplines such as botany, the study of plants; zoology, the study of animals; genetics; and physiology, the study of how living systems function.

At the molecular level, biology examines how the information in DNA is copied and translated into proteins, the molecules that carry out most of a cell's work. Cells reproduce by division: mitosis produces identical body cells, while meiosis produces sex cells with half the usual number of chromosomes, which is the basis of sexual reproduction and the inheritance described by genetics. Enzymes act as catalysts that drive the chemical reactions of metabolism, and in plants photosynthesis captures light energy to build sugars from carbon dioxide and water.

To make sense of life's diversity, biologists classify organisms through taxonomy, arranging them in a nested hierarchy of groups from kingdom down to species. Within multicellular organisms, specialised tissues form organs and organ systems, such as the circulatory, lymphatic, digestive and muscular systems in animals, while flowering plants have their own structures for reproduction, transport and growth regulated by hormones. Maintaining stable internal conditions, known as homeostasis, is a recurring theme across all of these levels.

Frequently asked questions

What is the difference between mitosis and meiosis?

Mitosis produces two genetically identical cells for growth and repair. Meiosis produces sex cells with half the chromosome number, enabling sexual reproduction and genetic variation.

What does taxonomy do?

Taxonomy names and classifies organisms into a ranked hierarchy of groups, from broad kingdoms down to individual species, based on shared characteristics and ancestry.

What is homeostasis?

Homeostasis is the maintenance of stable internal conditions, such as temperature or chemical balance, within an organism despite changes in its environment.