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Life cycles can be divided into two major stages: growth and reproduction. These two cannot take place at the same time, so once reproduction has begun, growth usually ends. [9] This shift is important because it can also affect other aspects of an organism's life, such as the organization of its group or its social interactions. [8]
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 ...
According to that theory, embryos pass through successive stages that represent the adult forms of less complex organisms in the course of development, and that ultimately reflects scala naturae (the great chain of being). [2] von Baer believed that such linear development is impossible. He posited that instead of linear progression, embryos ...
Below the level of living systems, he defines space and time, matter and energy, information and entropy, levels of organization, and physical and conceptual factors, and above living systems ecological, planetary and solar systems, galaxies, etc. [3] [4] [5] Miller's central thesis is that the multiple levels of living systems (cells, organs ...
In this course, we examine how the Earth, Universe, life and the elements originated and how different biogeochemical cycles are structured and coupled today. There is a strong emphasis on how humans have altered these cycles through various activities and processes such as climate change, mining, agriculture and changing land uses.
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from matter that does not. It is defined descriptively by the capacity for homeostasis , organisation , metabolism , growth , adaptation , response to stimuli , and reproduction .
The chain of being continued to be part of metaphysics in 19th-century education, and the concept was well known. The geologist Charles Lyell used it as a metaphor in his 1851 Elements of Geology description of the geological column , where he used the term " missing links " about missing parts of the continuum.
The Bradford Hill criteria, otherwise known as Hill's criteria for causation, are a group of nine principles that can be useful in establishing epidemiologic evidence of a causal relationship between a presumed cause and an observed effect and have been widely used in public health research.