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This science is one of the two major branches of natural science, the other being physical science, which is concerned with non-living matter. Biology is the overall natural science that studies life, with the other life sciences as its sub-disciplines. Some life sciences focus on a specific type of organism.
The history of life on Earth traces how organisms have evolved from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and all life on Earth, both living and extinct, descended from a last universal common ancestor that lived about 3.5 billion years ago .
Animal corpses, like this African buffalo, are recycled by the ecosystem, providing energy and nutrients for living organisms. Death is the termination of all vital functions or life processes in an organism or cell. [29] [30] One of the challenges in defining death is in distinguishing it from life.
Intermediate minor rankings are not shown. In biology, a kingdom is the second highest taxonomic rank, just below domain. Kingdoms are divided into smaller groups called phyla (singular phylum). Traditionally, some textbooks from the United States and Canada used a system of six kingdoms ( Animalia, Plantae, Fungi, Protista, Archaea ...
v. t. e. Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. [ 1][ 2] All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and functioning of organisms. [ 3] Cell biology is the study of the structural and ...
Tree of life (biology) The tree of life or universal tree of life is a metaphor, conceptual model, and research tool used to explore the evolution of life and describe the relationships between organisms, both living and extinct, as described in a famous passage in Charles Darwin 's On the Origin of Species (1859). [ 1]
Living systems. Living systems are life forms (or, more colloquially known as living things) treated as a system. They are said to be open self-organizing and said to interact with their environment. These systems are maintained by flows of information, energy and matter. Multiple theories of living systems have been proposed.
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...