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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 ...
The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia.
This is the beginning of the diploid phase of the human life cycle after two genetically unique haploid cells created via meiosis and chromosomal translocation combine their DNA and begin to develop into a multi-cellular organism. The zygote is genetically distinct from each of its parents. The process of fertilization lasts around 24 hours. [13]
Human embryonic development refers to the development and formation of the human embryo. It is characterised by the process of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, human development entails growth from a one-celled zygote to an adult human being.
The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period.
Human evolution is the evolutionary process within the history of primates that led to the emergence of Homo sapiens as a distinct species of the hominid family that includes all the great apes. [1]
Human biology tries to understand and promotes research on humans as living beings as a scientific discipline. It makes use of various scientific methods, such as experiments and observations, to detail the biochemical and biophysical foundations of human life describe and formulate the underlying processes using models. As a basic science, it ...
Adult development encompasses the changes that occur in biological and psychological domains of human life from the end of adolescence until the end of one's life. Changes occur at the cellular level and are partially explained by biological theories of adult development and aging. [1]