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The evolution of the horse, a mammal of the family Equidae, occurred over a geologic time scale of 50 million years, transforming the small, dog-sized, [1] forest-dwelling Eohippus into the modern horse. Paleozoologists have been able to piece together a more complete outline of the evolutionary lineage of the
Draft horses today are used on a few small farms, but today are seen mainly for pulling and plowing competitions rather than farm work. Heavy harness horses are now used as an outcross with lighter breeds, such as the Thoroughbred, to produce the modern warmblood breeds popular in sport horse disciplines, particularly at the Olympic level.
Others reproduce quickly; but, under normal circumstances, most offspring do not survive to adulthood. For example, a rabbit (mature after 8 months) can produce 10–30 offspring per year, and a fruit fly (mature after 10–14 days) can produce up to 900 offspring per year.
An outline, also called a hierarchical outline, is a list arranged to show hierarchical relationships and is a type of tree structure. An outline is used [1] to present the main points (in sentences) or topics of a given subject. Each item in an outline may be divided into additional sub-items.
Again, however, this is not applicable to all sexual organisms. There are numerous species which are sexual but do not have a genetic-loss problem because they do not produce males or females. Yeast, for example, are isogamous sexual organisms which have two mating types which fuse and recombine their haploid genomes. Both sexes reproduce ...
The height of horses is measured at the highest point of the withers, where the neck meets the back. [23] This point is used because it is a stable point of the anatomy, unlike the head or neck, which move up and down in relation to the body of the horse.
Resource availability is essential for the unimpeded growth of a population. Examples of resources organisms use are food, water, shelter, sunlight, and nutrients.[1][2] Ideally, when resources in the habitat are unlimited, each species can fully realize its innate potential to grow in number, as Charles Darwin observed while developing his theory of natural selection.
Insect species make up more than two-thirds of all extant animal species. Most insect species reproduce sexually, though some species are facultatively parthenogenetic. Many insect species have sexual dimorphism, while in others the sexes look nearly identical. Typically they have two sexes with males producing spermatozoa and females ova.