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Marine food web. The pelagic food web, showing the central involvement of marine microorganisms in how the ocean imports nutrients from and then exports them back to the atmosphere and ocean floor. A marine food web is a food web of marine life. At the base of the ocean food web are single-celled algae and other plant-like organisms known as ...
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. It includes brief explanations of the various taxonomic ranks in ...
539 Ma – present. The Phanerozoic Eon (Greek: period of well-displayed life) marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, with major mass extinctions at division points.
[79] [83] Complexity in the life sciences (or biocomplexity) is defined by the "properties emerging from the interplay of behavioral, biological, physical, and social interactions that affect, sustain, or are modified by living organisms, including humans". [84]: 1018 Several concepts have emerged from the study of complexity in food webs.
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 nature of interaction between early humans and these sister species has been a long-standing source of controversy, the question being whether humans replaced these earlier species or whether they were in fact similar enough to interbreed, in which case these earlier populations may have contributed genetic material to modern humans.
e. The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid- Triassic, there were many synapsid species that looked like mammals. The lineage leading to today's mammals split up in the Jurassic; synapsids from this ...
Human history. Human history is the record of humankind from prehistory to the present. Modern humans evolved in Africa around 300,000 years ago and initially lived as hunter-gatherers. They migrated out of Africa during the Last Ice Age and had populated most of the Earth by the end of the Ice Age 12,000 years ago.