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The taxonomies of these 3 animals show relatedness because they allow us to classify them in the same order.  Since the taxonomies show how these organisms are all Artiodactyla, we know they are related since they all have an even number of toes and are ungulates.

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http://www.nhptv.org/wild/artiodactyla.asp

http://artiodactyla.blogspot.com/2011/05/basic-characteristics-of-all-members-of.html

https://www.britannica.com/animal/artiodactyl#toc51673

http://animaldiversity.org/accounts/Artiodactyla/#habitat

http://animals.mom.me/characteristics-doe-female-deer-5349.html

http://www.worldanimalfoundation.net/f/giraffe.pdf

http://www.veganpeace.com/animal_facts/Deer.htm.

http://www.fossilmuseum.net/Fossil_Sites/badlands/Perchoerus/Perchoerus.htm

http://www.nhc.ed.ac.uk/index.php?page=493.170.276

http://www.ucmp.berkeley.edu/mammal/artio/artiofr.html

https://www.pinterest.com/pin/315955730083812095/

https://www.ncbi.nlm.nih.gov/pubmed/16628495

http://www.bv.fapesp.br/en/bolsas/140418/karyotype-characterization-of-a-mazama-gouazoubira-artiodactyla-cervidae-population-from-the-nhec/

https://www.nature.com/nature/journal/v388/n6643/full/388666a0.html

https://www.ncbi.nlm.nih.gov/pubmed/10093226

https://academic.oup.com/jhered/article/105/3/324/769938/Molecular-Phylogeny-and-Chromosomal-Evolution-of#81212726

http://www.whozoo.org/mammals/Hoof/hoofphylo.html

http://necsi.edu/projects/evolution/evidence/embryos/evidence_embryo.html

https://www.britannica.com/animal/artiodactyl#toc51673

http://animals.mom.me/mating-communication-behavior-deer-11172.html

http://www.hippoworlds.com/hippopotamus-reproduction/

http://bioweb.uwlax.edu/bio203/s2007/parr_jaco/taxonomy.htm (and 1)

http://bioweb.uwlax.edu/bio203/s2014/flores_alex/index.htm (and 1)

http://bioweb.uwlax.edu/bio203/s2007/frisch_lisa/phylogenetic_tree.htm (and 1)

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The type of Natural Selection in the Order Artiodactyla is directional, which is that individuals with the most extreme version of a trait have greater fitness than individuals with an average form of the trait.  This means that when an individual has the most extreme variation of a trait, they are more likely to survive than those with the less extreme version.  An example of this in Order Artiodactyla is in giraffes.  A giraffe´s neck can be anything from 5 feet to 2.5 meters.  The most extreme version, around 8 feet, is the version that allows giraffes to have the highest fitness.  This is because when the leaves on trees at the very bottom run out from other individuals eating them, the giraffes with short necks won't be able to reach the higher points of the trees that have leaves.  So, the individuals with short necks will eventually starve while the giraffes with the longer necks will still be able to eat the leaves. Another example of directional selection in the Order Artiodactyla is the size of a deer's antlers or the length of a hippo's tail.

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An example of descent with modification in Artiodactyla is the neck of giraffes.  While ancestors of the giraffe had shorter necks, giraffe's today now have necks that are 8 feet tall due to descent with modification.  Since the giraffes were shorter, they were only able to reach and eat the leaves towards the bottoms of the trees but the leaves in their reach eventually ran out.  So, the majority of the giraffes starved due to not being able to reach the leaves and they would not be able to reproduce and pass on their version of the trait.  But the taller giraffes would live to reproduce and eventually pass on their traits to their offspring and the passing on of the long neck trait would continue on and on, causing giraffes today to have longer necks.  Other examples of descent with modification in the Order Artiodactyla includes where the hippos' facial features like the nose, mouth, and ears are positioned (eventually moved to the top of the head).

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The Order Artiodactyla underwent adaptive radiation about 35 million years ago during the Eocene epoch. Adaptive radiation is an evolutionary pattern in which many species evolve from a single ancestral species. The picture below shows how the suborders of the Order Artiodactyla formed. It illustrates how the original suborder split into two, the 'Neoselenodontia', which later formed the Tylopoda and Ruminantia, and the Suina.

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Geographic isolation is the physical separation of populations due to geographic barriers that prevent interbreeding and it is what caused the Order Artiodactyla to evolve.  An example of an organism in the order that was affected by geographic isolation is deer.  For instance, there are now 47 different species of deer due to isolation, two of which are the red brocket and the red deer.  The red brocket live in tropical rainforests while the red deer live in moorland, but both have the same niche which is the regeneration of seeds.  This shows that the species of deer split into two separate species due to a geographic barrier since they both have the same niche and are very similar but can no longer reproduce together.

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The type of evolution in the Order Artiodactyla is gradualism, which is the model of evolution in which gradual change over a long period of time leads to biological diversity.  This is because all ungulates have many similar qualities, such as being terrestrial, no collar bone, and cranial appendages, and the very first ungulates from millions of years ago had very similar qualities.  One of the few main differences in the different orders of ungulates are the number of toes and where the axis of an animal's weight is, but other than that, the different groups of ungulates are still very similar. In conclusion, the Order Artiodactyla and ungulates in general went through gradualism since the main difference between the different orders of ungulates is one of the few ways the ungulate has evolved and it took millions of years to occur.

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The evolution of the Order Artiodactyla is classified as divergent evolution, which is when two or more related but reproductively isolated populations become more and more dissimilar. This is because, as shown by the two phylogenetic trees, all orders of ungulates have a recent common ancestor. This means that all ungulates came from a single species, which based on the picture below it would have been the "ancestral species", that then split into many different orders like the Order Artiodactyla at "divergence". These different orders then continued to split into different species, "multiple descendant species".  So, the type of evolution the Order Artiodactyla underwent was divergent evolution since the order started from one species that then continued to split to form the species of Artiodactyla that we now know today.

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An anatomical structure in all animals in the Order Artiodactyla is four legs.  Since all Artiodactyla are grazers, having four legs allows them to easily travel in order to find places that have an abundance of plants.  Another function of having four legs are to run from predators.  While Artiodactyla are usually able to avoid predators, like hiding in the water for hippos or between trees with giraffes, they will sometimes be faced with a predator.  In order to get away from the predator, the animal has to run and having four legs allows them to easily run away from them.

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Name of fossil: Stockoceros onusrosagris
Age of fossil: Late Pleistocene

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This karyotype of a male hippo is both similar and different than that of a male human's.  One way that it is different is that while a human has 44 somatic chromosomes, hippos only have 34.  A similarity between the hippo and human karyotypes are the sex chromosomes.  Both species have two sex chromosomes and the males have an X and a Y chromosome.

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Recent studies have shown that although it is commonly thought that other groups of ungulates are more closely related to Artiodactyla than Cetacea (whales), it is actually the other way around. With the use of SINE's (short interspersed elements, basically segments of non-coding DNA), two families were formed based on the presence of SINE's. The family with SINE's consisted of whales, ruminants, and hippos and the family without were pigs and camels.  In addition to the two different families, there were also nine retroposition events of the SINE units, which also helps to understand the phylogenetic relationship of the animals.  This information shows that whales, hippos, and ruminants form a monophyletic group and that Artiodactyla and Cetacea have a recent common ancestor.

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One way how these fossils show evolution is in the anatomical similarities.  The fossils that show teeth are an example of a similarity in the anatomy of all Artiodactyla.  In fossil #4, which is the oldest of all 6 fossils (see the picture below for a geologic timeline), the teeth are very sharp and are larger than the other teeth.  Organisms that eat meat are carnivorous, but Artiodactyla are now herbivores.  This shows that, at one point, Artiodactyla did eat meat but they had to become herbivores due to a lack of meat in their area. So, the teeth of the Artiodactyla show evolution of the order because they show how they had to evolve to the changing availability of food in their area. Another example of the similarity in the fossils are the number of legs. Fossils #3 and #6 have four legs, which shows that Artiodactyla have always been grazers.  Four-legged animals are often grazers, which means they feed on plants like leaves from trees and shrubs, since having four legs allows them to easily move around to places with an abundance of plants.  So, this shows evolution because it shows how organisms in the Order Artiodactyla have always been grazers.

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Name of fossil: Oreodont

Age of fossil: Oligocene

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Name of fossil: Megaloceros

Age of fossil: Paleocene

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Name of fossil: Diacodexis

Age of fossil: Early Eocene

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Name of fossil: Leptauchenia nitida (Oreodont)

Age of fossil: Upper Oligocene

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Name of fossil: Perchoerus sp. (Pecarry)

Age of fossil: Upper Oligocene

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Organisms within the order include pigs, hippos, giraffes, camels, sheep, deer, goats, bison, cows, moose, and pronghorns.  Major characteristics of all organisms in the order include an even number of toes, find food through through grazing, are herbivores, and have the symmetry of the foot passing through the last two toes.  Since animals in the order are social animals, they are rarely ever found without their herd which can consist of 5 to thousands of animals.  Artiodactyla also use the practice of aggregating, which is basically grouping up with other animals, for protection and they also take seasonal migrations between breeding and feeding grounds.  Organisms in the order need sufficient forage in their habitat and often live in grasslands or meadows.  This is because grasslands and meadows both have large amounts of food for the Artiodactyla and the areas also have rocky cliffs to protect them from predators.  While males tend to live in areas with more food due to their larger size, females live in areas with more protection from predators since they are responsible for their young.

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Kingdom- Animalia
Phylum- Chordata
Class- Mammalia
Order- Artiodactyla
Family- Cerdivae
Genus- Odocoileus
Species- Virginianus

Deer often live in places in between the forest and open spaces that have vegetation, for example they are often found in agricultural land, grassland, or human settlements. Deer are mainly found in the US but they also stretch into Mexico and Canada. Their hooves consist of two toes, and deer hold their weight between the two toes.  The coat of a deer changes during the different seasons, which is most noticeable in the white tail deer. The bucks, males, grow and shed antlers once a year while the doe, females, do not. With their excellent sense of smell, deer have the ability to smell predators from a long distance.  In order to find food, which their diet consists of plants, fruits, and fallen leaves or twigs, deer forage in the early morning and late afternoon, which their night vision allows them to do.  Deer have two eyes that have the ability to see in the night on either side of their head, which allows them to view 310 degrees at all times in order to see predators and food in the early morning or late at night.  Deer also eat on the go since they are constantly moving and their flexible diet allows them to change what they eat depending on what is available.  When deer are alarmed or nervous, they stomp their feet into the ground, wave their tail in the air like a flag, and whistle out of their snouts.  While bucks usually spend the year alone, does spend most of the year with their young or with other does if they have none.

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Kingdom- Animalia
Phylum- Chordata
Class- Mammalia
Order- Artiodactyla
Family- Giraffidae
Genus- Giraffa
Species- Camelopardalis

The majority of giraffes are found in the open woodlands of eastern and southern Africa. Primarily, Giraffes live in areas with large amounts of acacia trees and bushes that they can feed on. Giraffes spend most of their day grazing, so they are often moving around and are considered non-terrestrial. They tend to only migrate when there is a lack of food or water but will stay in the same general area if there is no shortage. The most distinguishing characteristics of giraffes are their necks and spots. The neck of a giraffe can grow as long as 8 feet and allow them to see over trees/bushes in order to see predators at far distances and it is caused by the extremely elongated vertebrates in their necks. The spots on giraffes, which are used for disruptive camouflage, are all over a giraffe's body except for their underbellies.  The foot of a giraffe consists of four toes and the symmetry of their weight is between the third and fourth toes. Male giraffes also have small horns or "knobs" on the tops of their heads that are about 5 inches that are sometimes used to fight each other. The 15-20 inch long tongues that giraffes have help them to lick bugs off of their faces. When a giraffe senses a predator, they try to hide themselves in between the trees but they wait to run until they are in great danger.  Giraffes are also very social animals, as they travel in large herds with other giraffes of all different ages and sexes.

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Kingdom- Animalia
Phylum- Chordata
Class- Mammalia
Order-Artiodactyla
Family- Hippopotamidae
Genus- Hippopotamus
Species- Amphibius

Hippos are usually found in the water since they spend most of the day in freshwater sources but they are also found in grasslands. Since hippos are found in places with a hot climate like Africa, the water helps the hippos to escape the heat and the grasslands are used to forage and graze for food when it is cooler.  The features on the hippos face like eyes, ears, and nose are all on the top of their head, which allows them to have most of their body underwater to stay cool while still being able to see, breathe, and hear.  Hippos also have sebaceous (sweat) glands, which serve many purposes.  For example, the glands produce a liquid that runs red after a few minutes in the sun to protect the hippos skin.  Hippos can also open their mouths 180 degrees and they have 36 teeth, which allow them to easily retrieve and chew food.  They tend to eat grass and vegetation, but since shortages often happen due to hippos eating 1.5% of their body weight daily, hippos often are forced to eat other animals and insects.  Throughout the day, hippos tend to stay in large groups but are often in solidarity during the night.  Females are very protective of their young and when males serve a threat to them, the females will attack the male and in order to say they mean no harm, male hippos will lay down.