Biology

Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, origin, evolution, and distribution of life. Central to biology are five fundamental themes: the cell as the basic unit of life, genes and heredity as the basis of inheritance, evolution as the driver of biological diversity, energy transformation for sustaining life processes, and the maintenance of internal stability (homeostasis).

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thumb|Mammals excrete urine through the urinary system. Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates, this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell. For example, placental mammals expel urine from the bladder through the urethra, which is part of the excretory system. Unicellular organisms discharge waste products directly through the surface of the cell. Another example would be how mammals release solid waste (f

right|thumb|Francesco Redi, founder of [[biology]]

property of originating or developing from within an organism, tissue, or cell

thumb|right|A 3D cross-section of the Lukina jama–Trojama [[cave system in the Velebit mountains of Croatia. The collection sites (1) of the shells and the single living specimen (2) of the cave-dwelling snail Zospeum tholussum are indicated.]] thumb|The spider Trogloraptor marchingtoni from a cave in [[Oregon.]]

theory; chemical substances (oxytocin) are studied in the context of their roles in producing human experiences and behaviors that are associated with love

factor which makes populations resistant to evolutionary change