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"Now, here, you see, it takes all the running you can do, to keep in the same place." — Lewis Carroll [4]. In 1973, Leigh Van Valen proposed the hypothesis as an "explanatory tangent" to explain the "law of extinction" known as "Van Valen's law", [1] which states that the probability of extinction does not depend on the lifetime of the species or higher-rank taxon, instead being constant ...
The timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth.Dates in this article are consensus estimates based on scientific evidence, mainly fossils.
Darwin argued that species evolved through natural selection from variations within population which he termed as 'varieties'. [ 32 ] Later on, through a series of experiments, Turresson studied the effect of the environment on heritable plant variation and came up with the term 'ecotype' to denote differences between groups occupying distinct ...
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 the ideal free distribution, individuals will equalize between habitat A and habitat B so that each individual has the same fitness. According to this example, habitat A will always have more individuals than habitat B. Figure 2. A habitat isodar for one species in two habitats. The species always prefers habitat A over habitat B.
Mass extinctions are characterized by the loss of at least 75% of species within a geologically short period of time (i.e., less than 2 million years). [18] [51] The Holocene extinction is also known as the "sixth extinction", as it is possibly the sixth mass extinction event, after the Ordovician–Silurian extinction events, the Late Devonian extinction, the Permian–Triassic extinction ...
[101] [102] Since the island separated from mainland Africa 66 million years ago, many species and ecosystems have evolved independently. [103] Indonesia 's 17,000 islands cover 735,355 square miles (1,904,560 km 2 ) and contain 10% of the world's flowering plants , 12% of mammals and 17% of reptiles , amphibians and birds —along with nearly ...
The annual life cycle has evolved in over 120 plant families across the entire angiosperm phylogeny. [213] Notably, the prevalence of annual species increases under hot-dry summer conditions in different families including Asteraceae, Brassicaceae, Fabaceae, and Poaceae. [212] Leaves have evolved multiple times - see Evolutionary history of plants.