• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Horse Evolution

Extracts from this document...

Introduction

Horse Evolution The horse family is a classic example of evolution and is supported by extensive fossil evidence. It has been comprehensively studied to form possibly the most complete evolution of any animal after humans. Horses are believed to have first appeared around 55 million years ago in the form of the Hyracotherium, or 'hyrax-like beast' (The World Book Encyclopedia). They originally inhabited North America and Europe, where the oldest fossils of possible ancestors were found (Encyclop�dia Britannica, 2007). The Przewalski's Horse, Equus ferus przewalskii or Equus caballus przewalskii, belongs to the family Equidae in the order Perissodactyla, which means odd-toed ungulates (Wikipedia, 2007). Animals in this order all have hoofed feet with an odd number of toes, mobile upper lips and similar tooth structure. Other animal families in this order are tapirs and rhinoceroses. In the evolution of the horse, the change of the teeth, toes, legs and overall shape of the body are of particular significance. These characteristics evolved as adaptations to changes in their environment and the progress from a smaller minor species to one of the largest species today. The equids diet began to change from foliage to grasses when grasses first began to flourish, causing the equids to have larger and more durable teeth. Equids also became further under threat from predators as new species evolved, leading them to be capable of greater speeds. Equids adapted by lengthening their limbs and shifting the weight of the body to the third toe, the longest of the toes. ...read more.

Middle

They lived in North America and had a long skull with a facial structure similar to that of modern horses (Tufts University, 2007). Its third toe was still the strongest and largest, carrying the weight of the animal. The four premolars resembled the molars, though were relatively small. The incisors had crowns with some having a shallow depression. Approximately 17 million years ago, the Merychippus evolved from the Parahippus. It had wider molars believed to be used for crunching harder grasses (Draper, J. 1999). It grew to around 100 cm tall and was a grass eater, not a leaf eater, as it completed the transition from living in forests to grassy plains. The hind legs were relatively short and the two side toes had very small hooves that probably only touched the ground when running (Florida Museum of Natural History, 2007). The legs became more rigid and more effective at carrying weight as equids evolved into a larger animal. The Merychippus descended into three equids: the Hipparion, Protohippus and Pliohippus. The Pliohippus evolved around 15 million years ago and is believed to be the ancestor of modern horses. It retained the two extra toes on both sides of the hoof, thought to have been barely visible externally. It had a deep facial fossa similar to that of the Mesohippus (Critters-2-Go, 2007). Thirteen million years ago, the Dinohippus evolved from the Merychippus and was the most common horse of its time. ...read more.

Conclusion

The population of Przewalski's Horses dwindled during the early 1900s due to increasing competition from livestock for pastureland. Fifteen horses were bred in captivity in the 1950s at zoos around the world. Western Plains Zoo in Dubbo, New South Wales, has been successfully involved in breeding Przewalski's Horses since 1983 (Taronga and Western Plains Zoo, 2007). In 1995, horses from different zoos were transported to Mongolia and were successfully bred in the wild. There are now between 500 and 1500 currently living in the wild, thought it is still endangered. The release of these horses into the wild will reinforce and improve the likelihood of survival through the genetic viability of the small herd (Taronga and Western Plains Zoo, 2007). The horse family remains a classic example of evolution, with an extensive line of animals dating back 55 million years ago. The Przewalski's Horse has had a long and complicated ancestry and is the closest and only wild relative of the domestic horse alive today. Bibliography Text Draper, J. 1999, The Ultimate Enclyopedia of Horse Breeds & Horse Care, Sebastian Kelly/Anness Publishing, Oxford. 'Horse', 1990, The World Book Encyclopedia, vol. 8, World Book, Inc. Chicago. Internet Critters-2-Go. Prehistoric Horses. [Online] Available http://www.critters-2-go.com/prehistoric/prehistoric_horses.htm 21/08/07 Encyclop�dia Britannica Online School Edition. Evolution of the Horse. [Online] Available http://www.school.eb.com.au/all/comptons/article-202190?query=horse%20evolution&ct=null 21/08/07 Florida Museum of Natural History. Fossil Horse Cybermuseum. [Online] Available http://www.flmnh.ufl.edu/fhc/firstCM.htm 13/08/07 Hunt, K. Horse Evolution. [Online] Available http://www.talkorigins.org/faqs/horses/horse_evol.html 08/08/07 Taronga and Western Plains Zoo. Przewalski Horse. [Online] Available http://www.zoo.nsw.gov.au//imagedata/Prze.pdf 29/08/07 Tufts University. Horse Evolution Over 55 Million Years. [Online] Available http://chem.tufts.edu/science/evolution/HorseEvolution.htm 24/08/07 Wikipedia. Evolution of the Horse. [Online] Available http://en.wikipedia.org/wiki/Evolution_of_the_horse 22/08/07 Wikipedia. Przewalski's Horse. [Online] Available http://en.wikipedia. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Zoology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Zoology essays

  1. The Implications of the UK's Climate Change Policy on Biodiversity

    with government agencies and concentrations, temperature and rainfall in the field NGOs published five implication values designed at to imitate upcoming weather situations (John, 2006). Table 1.Modelling Future Impacts on Biodiversity (PPN 2009) (red = declining species and blue = expanding species)

  2. Captive breeding

    Large populations will usually have a greater diversity of alleles compared to small populations. This diversity indicates a greater potential for evolution of new combinations of genes and a greater capacity for evolutionary adaptation to different habitats. In other words, the population would be fitter.

  1. Invertebrate colonisation of leaf packs of different palatability in an upland river.

    Results The community is dominated by Nemouridae stonefly, along with Black fly (Simuliidae) and Baetidae mayfly they make up almost 80% of the individuals found. The remainder of the community is made up of 18 other taxa. It was shown that the substrate type in the bag significantly affected the total numbers of invertebrates found therein (Table 1)

  2. "Discuss the strengths and weaknesses of Ecologism as a new ethic."

    simply enlarges the boundaries of the community to include soils, waters, plants, and animals, or collectively: the land."7 An ecologist ethic, can be in the final analysis religious or spiritual, resting as it does on the virtues of humility and respect.

  1. Investigating the effect that group size has on the vigilant behaviour of flocks of ...

    Figure 1: The percent of the group looking and being vigilant plotted against the group size in order to determine if they have a linear relationship. The graph could be interpreted as slightly linear but there is far too much variation to be certain.

  2. This report was commissioned by Sunderland City Council to assess the ecological and educational ...

    4.4 Woodland The main area of woodland on site is a semi-natural Ash dominated area to the south of Rock Farm. The woodland was surveyed and the vegetation in the studied quadrates was found to be most similar to W8e (Fraxinus Excelsior-Acer campeste-Mercurialis perrennis-Geranium robertianum woodland).

  1. The grasslands of North American are called as prairies; they cover about 1.4 million ...

    Leaves of the tall grasses turn beautiful shades of yellow, orange, and tan. There are no natural barriers, like trees, so there is a constant wind. Grasses with deep root systems keep the soil from blowing away. Most animals have adapted to the open, treeless prairie by digging burrows.

  2. Tasmanian Devil Facial Tumor Disease

    Figure 1. The area and year of DFTD emergence. Retrieved from McCallum, H. & Tompkins, D.M. (2007) Distribution and Impacts of Tasmanian Devil Facial Tumour Disease. EcoHealth Journal Consortium. Symptoms of the disease Devil facial tumour disease has a six month incubation period and is a rapid killer.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work