No the earth is extremely dynamic and changes dramatically
The experts calculate that between 0.01 and 0.1% of all species will become extinct each year. If the low estimate of the number of species out there is true - i.e. that there are around 2 million different species on our planet - then that means between 200 and 2,000 extinctions occur every year.
What is extinction?
- Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species.
- The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence.
- More than 99% of all species that ever lived on Earth, amounting to over five billion species, are estimated to have died out.
- It is estimated that there are currently around 8.7 million species of eukaryote globally, and possibly many times more if microorganisms, like bacteria, are included. Notable extinct animal species include non-avian dinosaurs, saber-toothed cats, dodos, mammoths, ground sloths, thylacines, trilobites and golden toads.
- Through evolution, species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche and species become extinct when they are no longer able to survive in changing conditions or against superior competition.
- The relationship between animals and their ecological niches has been firmly established.
- A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive with little to no morphological change for hundreds of millions of years.
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Answer: More than 99 percent of all organisms that have ever lived on Earth are extinct. As new species evolve to fit ever changing ecological niches, older species fade away. But the rate of extinction is far from constant. At least a handful of times in the last 500 million years, 75 to more than 90 percent of all species on Earth have disappeared in a geological blink of an eye in catastrophes we call mass extinctions.
Though mass extinctions are deadly events, they open up the planet for new forms of life to emerge. The most studied mass extinction, which marked the boundary between the Cretaceous and Paleogene periods about 66 million years ago, killed off the nonavian dinosaurs and made room for mammals and birds to rapidly diversify
The answer is; the melanin in darkly pigmented skin protects DNA from UV radiation, and UV radiation can cause skin cancer
In Africa, due to its equatorial latitude location, receives direct sunlight at more or less 90 degrees most of the year. These highly concentrated rays increase the UV radiation exposure that can cause damage to cell DNA. Selection pressure, therefore, favored individuals with high melanin concentrations that protect against UV. Therefore population evolved towards high melanin densities in the skin.
In order to solve this problem we use these formula:
<span>p2 + 2pq + q2 = 1p + q = 1p = % dominant allele in the population
q = % recessive allele in the population
p2 = % homozygous dominant individuals
q2 = % homozygous recessive individuals
2pq = % heterozygous individualsFrom the given, we haveq2 = 21%Simply taking the square root,q = 4.58%</span>
