Answer:
B. It is done by humans to select certain traits useful to us.
Explanation:
There are two main types of selection: natural and artificial. Natural selection is all of the other answers, it is seen over generations and allows the fittest to survive. It also occurs with no human intervention. However, artificial selection is done by humans. It occurs when humans breed animals to best fit their needs. This is best seen in dog breeding.
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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Radiometric dating method. Geologists commonly used radiometric age-dating to determine the numerical age of rock and fossils based on the natural radioactive decay of certain elements, including potassium and carbon.
Since there are no given choices, I would just compare and contrast DNA and RNA. These are the two types of nucleic acids in the human body. The structural unit of nucleic acids are composed of repeating units of monomers called nucleotides. Nucelotides are composed of three functional groups: sugars which are specifically pentoses (5-Carbon sugars), phosphate group and nitrogenous base.
Now, the RNA and DNA differ in the composition of these sugars and the bases. Based on the nitrogenous bases and sugar, the DNA has a deoxyribose as the sugar and its 4 bases are adenine, guanine, cytosine and thymine. For RNA, the sugar is ribose while its 4 bases are <span>adenine, guanine, cytosine, and uracil.
They also differ in their structure. </span>DNA is a double stranded β-helix with a long chain of nucleotides. RNA is composed of a shorter chain with a single strand α-helix structure.
Lastly, they differ in their functions. T<span>he DNA is responsible for storing the genetic information while the RNA is responsible for transporting the genetic information to the ribosomes which synthesize proteins.</span>
