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Natural selection acts on an organism's phenotype, or physical characteristics. Phenotype is determined by an organism's genetic make-up (genotype) and the environment in which the organism lives. When different organisms in a population possess different versions of a gene for a certain trait, each of these versions is known as an allele .
The geological history of the Earth follows the major geological events in Earth's past based on the geological time scale, a system of chronological measurement based on the study of the planet's rock layers ( stratigraphy ). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left ...
Physiognomy. Lithographic drawing illustrative of the relation between the human physiognomy and that of the brute creation, by Charles Le Brun (1619–1690). Physiognomy (from the Greek φύσις, ' physis ', meaning "nature", and ' gnomon ', meaning "judge" or "interpreter") or face reading is the practice of assessing a person's character ...
Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System. Of the four rocky planets, it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it, taking a year (about 365.25 days) to complete one revolution.
Human physical appearance. Human physical appearance is the outward phenotype or look of human beings. Image of a Caucasian female (left) and an Asian male (right) human body seen from front (upper) and back (lower). Adult human bodies photographed whose naturally-occurring pubic, body, and facial hair have been deliberately removed to show ...
Universal natural resources and physical phenomena that lack clear-cut boundaries, such as air, water, and climate, as well as energy, radiation, electric charge, and magnetism, not originating from civilized human actions. In contrast to the natural environment is the built environment.
The physical factors may include (for example): soil, moisture, range of temperature, and light intensity. Biotic factors include the availability of food and the presence or absence of predators. Every species has particular habitat requirements, with habitat generalist species able to thrive in a wide array of environmental conditions while ...
The last universal common ancestor ( LUCA) is the hypothesized common ancestral cell from which the three domains of life, the Bacteria, the Archaea, and the Eukarya originated. It is suggested to have been a "cellular organism that had a lipid bilayer and used DNA, RNA, and protein". [2] The LUCA has also been defined as "a hypothetical ...